After more than two decades of searching, scientists have finally observed a phenomenon in a hot and dense particle 'soup' similar to that which filled the cosmos moments after the Big Bang. The observation could help cosmologists better understand the incredibly hot and dense state of the universe in its earliest moments.

The world's most powerful particle accelerator, the Large Hadron Collider (LHC), regularly creates this so-called quark-gluon plasma by smashing together the atomic nuclei of heavy elements like lead and generating sprays of particles called jets, from which this hot and dense particle soup emerges. This is necessary because in the modern universe, quarks and gluons, referred to as "partons," are only ever found together comprising particles like protons and neutrons. Thus, it takes the kind of energy generated by smashing atoms together at near-light-speeds to free these partons and generate the hot 'soup' known as quark-gluon plasma.

As particles ripple through the quark-gluon plasma, they lose energy and momentum to this medium, which should create wakes in this primordial soup, much like that which is created when the hull of a boat pushes through the ocean. However, researchers had failed to see this so-called "diffusion wake" for two decades. That is, until now.

"Observing and quantifying the quark-gluon plasma diffusion wake opens the door to the new precision characterization of the properties and dynamics of the quark-gluon plasma, and promises new insights into the evolution of the early universe,” team leader Raghunath Pradhan of the University of Illinois Chicago (UIC) said in a statement.

A new approach in the hunt for particle wakes

Previously, the search for wave signals had involved generating events involving the production of a jet alongside a particle called a Z boson. However, while this had provided some evidence of particle wakes, signals from these wakes are subtle and easily drowned out by other jet-related effects, meaning these detections weren't statistically significant enough to be classed as a confirmed detection.

To search for the wave signal, this team took a different approach and used the LHC to smash together two lead nuclei to create jets of particles that were back-to-back, called a dijet event. The unique shape of these events meant that signals from wakes could be more easily disentangled from surrounding noise.

The team's measurement showed a clear lack of particles behind the direction of the jets, which was particularly prominent at relatively low momentum. That is exactly what would be expected for a diffusion wake. The strongest wake signals were detected in more centralised lead-lead collisions, which create more quark-gluon plasma.

"This observation is a culmination of a decades-long quest to observe the wake phenomenon; it has been predicted by theory over 20 years ago, but remained elusive in the experimental data," team leader Olga Evdokimov of UIC said.

The team's research was accepted for publication on June 25 in the journal Physical Review Letters.

Astronomers have traced a high-energy "ghost particle" back to Shadow Blaster, a star-forming galaxy located 11 billion light-years away. That means that this particle, a neutrino, had been travelling to us ever since the 13.8 billion year-old universe was just around 3 billion years old.

The discovery offers the first evidence that star-forming galaxies like Shadow Blaster play a significant role in populating the universe with mysterious high-energy cosmic ghost-neutrinos. These particles get their spooky nickname because, possessing virtually no mass and no electric charge, they pass through matter with little to no interaction while moving at nearly the speed of light. For context, as you read the preceding sentence, over 65 billion neutrinos streamed through every square inch of your body; that's about 100 billion per square centimeter.

Despite the difficulty associated with detecting such particles, humanity has been spotting neutrinos since the 1960s, but only a few sources of these particles have been identified. Neutrinos are the second most abundant particles in the cosmos after photons, particles of light, and the identified sources are nowhere near enough to account for this abundance. That has prompted the search for other, hidden neutrino sources, especially those which can accelerate neutrinos to high energies. Now that hunt has led to the identification of the incredibly bright Shadow Blaster galaxy, officially designated JCMT0402−0424, which shines in infrared, as a potential neutrino source.

"Shadow Blaster possesses the kind of dense, gas-rich environment that theoretical models have long suggested could efficiently produce high-energy neutrinos," Yuji Urata of MITOS Science Co., LTD. in Taiwan said in a statement. "If confirmed, Shadow Blaster would be the first-ever individual dusty star-forming galaxy directly linked to a high-energy neutrino event."

Thus far, no other credible candidates exist as potential sources for this high-energy neutrino, designated IC 210922A.

Chasing ghosts

Astronomers were alerted to the existence of IC 210922A half a decade ago when this high-energy neutrino event was detected by the IceCube Neutrino Observatory located in Antarctica. This set the astronomical community scouring space in the direction of the constellation Eridanus for potential sources for an electromagnetic counterpart to this event with a range of telescopes. This turned up no convincing gamma-ray, X-ray or optical counterpart for the neutrino detection, nor could any gamma-ray burst, supernova, or tidal disruption event (in which a black hole violently shreds a star) be linked with IC 210922A.

Urata and colleagues began their personal search with the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, and the Submillimeter Array (SMA), discovering Shadow Blaster, a galaxy in the right position and with the right level of brightness to be associated with IC 210922A. The team followed this up with an investigation using the Atacama Large Millimeter/submillimeter Array (ALMA), a collection of 66 radio wave antennas in northern Chile.

The detection of this galaxy was possible because it is strongly gravitationally lensed. Gravitational lensing is a phenomenon that occurs when an object of great mass comes between Earth and a distant background source, curving the fabric of spacetime. As light from the background source navigates this curvature, its path is curved. This results in light from the lensed source arriving at different times to our telescopes, causing it to be amplified.

In the case of Shadow Blaster, before the team could learn anything about this distant galaxy, they had to discover more about the object serving as the intermediate gravitational lens, specifically what type of object it is, its mass, and its distance from us. To do this, they turned to the Gemini North telescope and its Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near-InfraRed Spectrograph (GNIRS) instruments.

With the model of a gravitational lens determined, the team discovered that Shadow Blaster is a galaxy with an extremely compact heart filled with dense clouds of gas and dust that is fueling an intense burst of star formation. A region such as this has long been theorized to serve as a powerful particle accelerator. Because Shadow Blaster lacks a feeding supermassive black hole, this research shows that these regions can still serve as cosmic particle accelerators when they harbor sleeping black holes and in the absence of the powerful jets that erupt from active galactic nuclei (AGNs).

As for the overall population of neutrinos, this research could help account for that too. Intensely star-forming galaxies, or starburst galaxies, are believed to have been prevalent around 10 billion years ago in the early universe. Thus, these galaxies could have been producing a multitude of high-energy neutrinos. Proving that may prove difficult, however, as astronomers don't have the good fortune to find all of these galaxies lurking behind a gravitational lens, meaning they may be too faint and distant to study.

"Our analysis suggests that this population could contribute up to roughly 20% of the observed diffuse neutrino background measured by IceCube," Urata concluded,

The team's research was published on Wednesday (June 17) in the journal Nature Astronomy.

Anyone who has been paying attention to cosmology over the past few years is aware of problems with our best attempts to explain why the universe is the way it is.

Our standard model, Lambda-CDM (or LCDM), is one of the most successful theories in the history of science. It accounts for the cosmic microwave background, the large-scale distribution of galaxies, the abundances of light elements, and basically every other large-scale observation we throw at it. The trouble lies with that capital L. Lambda is the cosmological constant, Einstein's placeholder for the energy of empty space, and it does the heavy lifting of explaining why the universe's expansion is accelerating.

The trouble is that we have no idea why Lambda has the value it does. Quantum field theory predicts a value roughly 122 orders of magnitude larger than what we measure  — one of the worst predictions in the history of physics. On top of that, the universe seems to be expanding at different rates depending on whether we measure it locally or infer it from the early-universe data, a stubborn disagreement known as the Hubble tension. Neither problem has gone away despite decades of work.

In a new paper posted to the arXiv preprint server, theoretical physicist Savvas Koushiappas of Brown University has put forward an unusual proposal. The universe, he argues, may have its own version of Heisenberg's uncertainty principle. Its size and its rate of expansion can't be simultaneously specified with perfect precision, and that fundamental fuzziness might be enough to explain dark energy without invoking any new physics at all.

Koushiappas's proposal sidesteps both. Instead of adding new particles or new fields, he asks what happens if we treat the universe's scale factor (essentially, its size) and its expansion rate as quantum mechanical operators that don't quite commute. In ordinary quantum mechanics, the same kind of non-commutation is what gives us the uncertainty principle: position and momentum can't both be pinned down at once. Apply the same idea to the universe as a whole and you get a deformed version of the Friedmann equation, the master equation that describes how the cosmos grows.

The deformation depends on a single free exponent. When that exponent is positive, the modified Friedmann equation naturally produces late-time accelerated expansion. No dark energy required. The universe behaves as if it had a built-in cosmological constant, but the acceleration comes from the geometry of its own quantum fuzziness rather than from some mysterious vacuum energy.

It gets more interesting. The same equation also predicts that the dark-energy-like behavior shouldn't be perfectly constant. The effective equation-of-state parameter (a number cosmologists use to characterize dark energy, which equals exactly -1 for a true cosmological constant) comes out slightly greater than -1 in this model. That is exactly the kind of deviation that current surveys like DESI have been hinting at, and which next-generation surveys should be able to confirm or rule out.

And if you flip the sign of the exponent, the same machinery does something else entirely. Instead of accelerating the late universe, it smooths out the early universe, replacing the Big Bang singularity with what Koushiappas calls a "classical bounce." The cosmos contracts to a minimum size, then expands. No infinite density, no breakdown of physics at t=0.

There are caveats. This is a single-author theoretical paper, not an observation, and the math is doing a lot of work. The model assumes a spatially flat universe, which is fine given current data. It also requires the expansion rate to be a well-behaved quantum operator, which in turn fixes one of the free parameters. The big question is whether the specific deviations from Lambda-CDM that this model predicts actually show up in the data, or whether the universe stubbornly insists on a value of -1 for the dark energy equation of state.

We should know soon. The Dark Energy Spectroscopic Instrument, the Euclid mission, and the Vera C. Rubin Observatory are all in the business of measuring exactly the quantities that this model predicts will deviate from a pure cosmological constant. If they keep finding hints of an equation of state slightly above -1, Koushiappas's cosmic uncertainty principle is going to start looking very interesting indeed.

On Earth, the Large Hadron Collider can smash atoms together and accelerate particles to near light speeds — but in space, there are high-energy cosmic rays with over 10 million times more power than even those zippy particles. And now, new research suggests such cosmic rays may hide a secret that is the key to unlocking a 60-year-old space puzzle.

One of these cosmic rays for instance, dubbed the Amaterasu particle (after the Japanese sun goddess) slammed into Earth in 2021 with an energy 40 million times greater than particles slammed together at the Large Hadron Collider (LHC). Amaterasu is considered the second most powerful cosmic ray ever detected — after the aptly named "Oh-My-God particle" detected back in 1991. However, the origins of these particles, and the sources that accelerated them to such high energies, are shrouded in mystery.

Traveling with the kinetic energy equivalent to that of a fast-moving tennis ball (a lot for a single cosmic-ray particle), the Amaterasu deepened that mystery as it appears to have originated from a void-like region with no obvious source. However, researchers finally think they may have hit upon an answer. A new study's team thinks the highest-energy cosmic rays may actually be atomic nuclei of elements heavier than iron. Could this be the missing link in our understanding of which mysterious violent events fling these intense particles toward Earth?

"The origins and acceleration mechanisms of ultrahigh-energy cosmic rays have been among the biggest mysteries in the field for more than 60 years, since the first example was reported," team leader Kohta Murase, of Penn State's Eberly College of Science, said in a statement. "Ultrahigh-energy cosmic rays can only be accelerated by some of the most powerful sources in the universe. When we detect individual cosmic-ray particles such as the Amaterasu particle here on Earth, we can often use their energies, arrival directions, and expected magnetic deflections to infer their possible cosmic sources."

Many sources have been proposed as the origins of high-energy cosmic rays, including the collapse of a massive star to form a neutron star or a black hole or the collision of two neutron stars themselves. For context, the matter that composes neutron stars is so dense that if a mere teaspoon of it were brought to Earth, it would weigh about 10 million tons, which is the same as 85,000 adult blue whales (try getting them on one teaspoon).

So, compressing a body with the mass of the sun to a width of around 12 miles (20 kilometers) is already incredibly violent — consider two of those compressed bodies meeting.

"These highest-energy cosmic rays are thought to come from extreme astrophysical sources, like two neutron stars colliding or a massive star collapsing," Murase said. "For many cosmic-ray events taken together, their energy distribution, arrival-direction pattern, and statistically inferred composition provide important clues about where these particles come from and how they are accelerated."

If Murase and fellow researchers are correct that cosmic rays may be the nuclei of elements heavier than iron, then this neutron star collision story may have some real footing at last.

To understand these high-energy particles and their origins, Murase and colleagues performed simulations tracking how cosmic rays of different masses would lose energy as they passed through vast cosmic distances to reach Earth. What this revealed was that atomic nuclei heavier than the atomic nucleus of iron lost energy much more slowly than lighter particles.

"Our research showed that at energies comparable to that of the Amaterasu particle, ultraheavy nuclei lose energy more slowly than protons or intermediate-mass nuclei, making them better able to survive cosmic distances and reach Earth at extreme energies," Murase said. "We are not saying that all ultrahigh-energy cosmic rays are ultraheavy nuclei. But if some of the highest-energy events are ultraheavy nuclei, that would impact how we search for their sources."

The team was also able to place constraints on how many heavy nuclei cosmic rays account for the overall population of high-energy cosmic rays.

"The most promising sites for producing and accelerating such ultraheavy nuclei are massive star deaths involving explosive collapse into black holes or strongly magnetized neutron stars, as well as binary neutron-star mergers known to be powerful gravitational-wave emitters," Murase said. "These violent cosmic phenomena can also power gamma-ray bursts that are among the most energetic explosions in the universe.

"A contribution from these sources could also help explain a possible difference seen between the northern and southern skies in the ultrahigh-energy cosmic-ray spectrum. If ultraheavy nuclei contribute significantly at the highest energies, future data should indicate a composition heavier than iron."

These results were published on Thursday (May 7) in the journal Physical Review Letters.

The world's first space-based neutrino detector launched to space last week to study elusive neutrino particles that constantly bombard Earth. The mission will test technology that could help researchers in the future to unravel hidden processes taking place deep inside the sun.

The detector, made of crystals of gallium and tungsten, is embedded in a 3U cubesat (about 12 inches long and 4 inches wide, an equivalent to 30 and 10 centimeters), which will orbit the planet at the altitude of 310 miles (500 kilometers) for about two years. The small instrument rode to orbit on the SpaceX CAS500-2 rideshare mission on May 3.

The project, called SNAPPY (for Solar Neutrino Astro-Particle PhYsic), was conceived by Wichita State University professor of physics and mathematics Nickolas Solomey. The project aims to validate the underlying technology for a future mission that could someday take a neutrino detector to the vicinity of the sun. "Neutrinos on Earth are pretty rare, so to detect neutrinos on Earth, you need very big detectors," Solomey told Space.com. "But closer to the sun, the number of neutrinos is a thousand and more times larger than here on Earth, which means that a one kilogram detector that we launch on a spacecraft and put closer to the sun is going to act like a thousand-kilogram detector here on Earth."

Neutrinos are near massless particles that emerge during natural nuclear decay, in nuclear fission reactions such as those taking place in nuclear reactors, and in nuclear fusion processes inside stars. Despite being the most abundant particles in the universe (tens of trillions of neutrinos pass through your body every second, according to the U.S. Department of Energy), neutrinos are notoriously difficult to detect.

Their elusive nature is caused by their barely there mass and lack of electric charge. To register the presence of neutrinos on Earth usually requires massive detectors buried deep underground. The neutrino's sparse reactions with matter are caused by the weak nuclear force, which guides the process of radioactive decay.

When a neutrino interacts with the nuclei of atoms, it transforms into an electron and a couple of more exotic particles known as muons and tau particles. To make sure the muons and electrons detected by the detectors really come from neutrino interactions, the detectors need to be placed deep underground where other cosmic particles cannot reach. The world's largest neutrino detector, China's Jiangmen Underground Neutrino Observatory, is buried 2,300 feet deep (700 meters) underground. The IceCube Neutrino Observatory on the South Pole sits even deeper — between 4,750 and 8,040 feet (1,450 and 2,450 meters) deep in the ice sheet.

The universe is awash with neutrinos that have been cruising through space since the Big Bang. But many also come from inside the sun. Yet, others reach our planet after being thrust into space in distant supernova explosions (the final blasts of stars that run out of fuel in their cores).

The high concentrations of neutrinos near the sun is what interests Solomey. The Snappy detector, currently undergoing testing in orbit, has a simple purpose — to validate that neutrino detection in space works. The gallium-based detector aboard the cubesat is also more sensitive to neutrino impacts than the argon-based detectors mostly used on Earth.

Solomey hopes that if the experiment proves successful, it might persuade NASA to place a neutrino detector on a possible future mission towards the sun.

"We could do a huge amount of solar neutrino interaction detections, but we could also increase the position resolution to get the image of the solar fusion shells that are around the core," Solomey explained. "We could study particle physics, the transport of the solar neutrinos as they get out of the sun and head towards deep space and some of them go towards Earth."

Because of the exceptional sensitivity of the gallium-based detector, Solomey thinks the team might be able to catch even the less energetic neutrinos that evade Earth-based detection.

Neutrinos come in different "flavors" based on the processes that created them. Solomey thinks that by analyzing en masse the neutrino flux streaming from the sun, researchers could open a unique window into the life-giving fusion processes that take place deep inside the star's core, far away from the reach of any human-made scientific instruments.

Because neutrinos barely interact with matter, they emerge from the immense depths of the sun within seconds of being born, said Solomey. On the other hand, scientists estimate that it takes some 100,000 years for the physical matter to bubble up the 435,000 miles (700,000 kilometers) from the sun's core to its surface.

"It's like putting a microscope into the core of the sun," said Solomey. "There are different types of fusion processes that occur in different layers away from the sun's core, and we could look at and study the structure of the solar fusion core looking at these different kinds of neutrinos."

The world's most powerful particle accelerator, the Large Hadron Collider, has given scientists their best look yet at quark-gluon plasma, the primordial matter that filled the universe moments after the Big Bang.

During the first fractions of a second of the universe's existence, the cosmos was filled with a hot and dense primordial soup called quark-gluon plasma. At the nearly 17-mile-long circular particle accelerator, the Large Hadron Collider (LHC) that sits deep below the French Alps, CERN scientists recreated the quark-gluon plasma by smashing together atomic nuclei of iron at near-light speed. The project is called ALICE (A Large Ion Collider Experiment).

The ALICE team obtained new information about the quark-gluon plasma (and thus the conditions in the early universe) when they spotted a pattern common to collisions between protons — the particles found at the heart of atoms — collisions between protons and lead nuclei, and collisions between lead nuclei themselves. This pattern could reveal how the quark-gluon plasma formed right after the Big Bang, indicating it could be forged by smaller particle collisions than previously thought.

When scientists first started smashing protons together at the LHC, it was theorized that collisions between protons as well as between protons and lead would be too small to generate quark-gluon plasma. However, tantalizing signs of this primordial matter have recently been seen in these small collisions as well as in the collisions between lead nuclei.

One of the signatures of quark-gluon plasma and its formation is the fact that particles aren't emitted evenly, but in a preferred direction, which scientists call anisotropic flow. At intermediate speeds, the anisotropic flow of particles depends on the number of quarks that compose them. Baryons, particles composed of three quarks, exhibit a stronger flow than mesons, which are particles composed of two quarks.

Scientists theorize that this is linked to the process that brings quarks together to form larger particles. Baryons have more quarks and thus gain greater flow.

In new research the ALICE Collaboration explained how they measured the anisotropic flow for different mesons and baryons created by proton-proton and proton-lead collisions. By isolating particles flowing together, the team confirmed that, just as is seen in heavy collisions, these lighter collisions give rise to baryons with stronger flow and mesons with weaker flow at intermediate speeds.

"This is the first time we have observed, for a large interval in momentum and for multiple species, this flow pattern in a subset of proton collisions in which an unusually large number of particles are produced," David Dobrigkeit Chinellato, Physics Coordinator of the ALICE experiment, said in a statement. "Our results support the hypothesis that an expanding system of quarks is present even when the size of the collision system is small."

The ALICE team compared the flow observations they made to models of quark-gluon plasma formation, finding the flow pattern closely fit models that account for the formation of baryons and mesons. Models that don't factor in this quark coalescence, however, failed to replicate the observed flow pattern.

The researchers also found that even the best-fit models couldn't completely account for the observed flow. There are still some lingering discrepancies, wrinkles that the team thinks other collisions between particles with sizes between protons and iron could help to iron out.

"We expect that, with the oxygen collisions that were recorded in 2025, which bridge the gap between proton collisions and lead collisions, we will gain new insights into the nature and evolution of the quark-gluon plasma across different collision systems," ALICE Spokesperson Kai Schweda said in the statement.

Then, scientists will edge even closer to understanding the conditions found at the very dawn of the universe.

A paper about this research was published on March 20 in the journal Nature Communications.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

Time feels like the most basic feature of reality. Seconds tick, days pass and everything from planetary motion to human memory seems to unfold along a single, irreversible direction. We are born and we die, in exactly that order. We plan our lives around time, measure it obsessively and experience it as an unbroken flow from past to future. It feels so obvious that time moves forward that questioning it can seem almost pointless.

And yet, for more than a century, physics has struggled to say what time actually is. This struggle is not philosophical nitpicking. It sits at the heart of some of the deepest problems in science.

Modern physics relies on different, but equally important, frameworks. One is Albert Einstein's theory of general relativity, which describes the gravity and motion of large objects such as planets. Another is quantum mechanics, which rules the microcosmos of atoms and particles. And on an even larger scale, the standard model of cosmology describes the birth and evolution of the universe as a whole. All rely on time, yet they treat it in incompatible ways.

When physicists try to combine these theories into a single framework, time often behaves in unexpected and troubling ways. Sometimes it stretches. Sometimes it slows. Sometimes it disappears entirely.

Einstein's theory of relativity was, in fact, the first major blow to our everyday intuition about time. Time, Einstein showed, is not universal. It runs at different speeds depending on gravity and motion. Two observers moving relative to one another will disagree about which events happened at the same time. Time became something elastic, woven together with space into a four-dimensional fabric called spacetime.

Quantum mechanics made things even stranger. In quantum theory, time is not something the theory explains. It is simply assumed. The equations of quantum mechanics describe how systems evolve with respect to time, but time itself remains an external parameter, a background clock that sits outside the theory.

This mismatch becomes acute when physicists try to describe gravity at the quantum level, which is crucial for developing the much coveted theory of everything – which links the main fundamental theories. But in many attempts to create such a theory, time vanishes as a parameter from the fundamental equations altogether. The universe appears frozen, described by equations that make no reference to change.

This puzzle is known as the problem of time, and it remains one of the most persistent obstacles to a unified theory of physics. Despite enormous progress in cosmology and particle physics, we still lack a clear explanation for why time flows at all.

Now a relatively new approach to physics, building on a mathematical framework called information theory, developed by Claude Shannon in the 1940s, has started coming up with surprising answers.

Entropy and the arrow of time

When physicists try to explain the direction of time, they often turn to a concept called entropy. The second law of thermodynamics states that disorder tends to increase. A glass can fall and shatter into a mess, but the shards never spontaneously leap back together. This asymmetry between past and future is often identified with the arrow of time.

This idea has been enormously influential. It explains why many processes are irreversible, including why we remember the past but not the future. If the universe started in a state of low entropy, and is getting messier as it evolves, that appears to explain why time moves forward. But entropy does not fully solve the problem of time.

For one thing, the fundamental quantum mechanical equations of physics do not distinguish between past and future. The arrow of time emerges only when we consider large numbers of particles and statistical behaviour. This also raises a deeper question: why did the universe start in such a low-entropy state to begin with? Statistically, there are more ways for a universe to have high entropy than low entropy, just as there are more ways for a room to be messy than tidy. So why would it start in a state that is so improbable?

The information revolution

Over the past few decades, a quiet but far-reaching revolution has taken place in physics. Information, once treated as an abstract bookkeeping tool used to track states or probabilities, has increasingly been recognised as a physical quantity in its own right, just like matter or radiation. While entropy measures how many microscopic states are possible, information measures how physical interactions limit and record those possibilities.

This shift did not happen overnight. It emerged gradually, driven by puzzles at the intersection of thermodynamics, quantum mechanics and gravity, where treating information as merely mathematical began to produce contradictions.

One of the earliest cracks appeared in black hole physics. When Stephen Hawking showed that black holes emit thermal radiation, it raised a disturbing possibility: information about whatever falls into a black hole might be permanently lost as heat. That conclusion conflicted with quantum mechanics, which demands that the entirety of information be preserved.

Resolving this tension forced physicists to confront a deeper truth. Information is not optional. If we want a full description of the universe that includes quantum mechanics, information cannot simply disappear without undermining the foundations of physics. This realisation had profound consequences. It became clear that information has thermodynamic cost, that erasing it dissipates energy, and that storing it requires physical resources.

In parallel, surprising connections emerged between gravity and thermodynamics. It was shown that Einstein's equations can be derived from thermodynamic principles that link spacetime geometry directly to entropy and information. In this view, gravity doesn't behave exactly like a fundamental force.

Instead, gravity appears to be what physicists call "emergen" – a phenomenon describing something that's greater than the sum of its parts, arising from more fundamental constituents. Take temperature. We can all feel it, but on a fundamental level, a single particle can't have temperature. It's not a fundamental feature. Instead it only emerges as a result of many molecules moving collectively.

Similarly, gravity can be described as an emergent phenomenon, arising from statistical processes. Some physicists have even suggested that gravity itself may emerge from information, reflecting how information is distributed, encoded and processed.

These ideas invite a radical shift in perspective. Instead of treating spacetime as primary, and information as something that lives inside it, information may be the more fundamental ingredient from which spacetime itself emerges. Building on this research, my colleagues and I have explored a framework in which spacetime itself acts as a storage medium for information – and it has important consequences for how we view time.

In this approach, spacetime is not perfectly smooth, as relativity suggests, but composed of discrete elements, each with a finite capacity to record quantum information from passing particles and fields. These elements are not bits in the digital sense, but physical carriers of quantum information, capable of retaining memory of past interactions.

A useful way to picture them is to think of spacetime like a material made of tiny, memory-bearing cells. Just as a crystal lattice can store defects that appeared earlier in time, these microscopic spacetime elements can retain traces of the interactions that have passed through them. They are not particles in the usual sense described by the standard model of particle physics, but a more fundamental layer of physical structure that particle physics operates on rather than explains.

This has an important implication. If spacetime records information, then its present state reflects not only what exists now, but everything that has happened before. Regions that have experienced more interactions carry a different imprint of information than regions that have experienced fewer. The universe, in this view, does not merely evolve according to timeless laws applied to changing states. It remembers.

A recording cosmos

This memory is not metaphorical. Every physical interaction leaves an informational trace. Although the basic equations of quantum mechanics can be run forwards or backwards in time, real interactions never happen in isolation. They inevitably involve surroundings, leak information outward and leave lasting records of what has occurred. Once this information has spread into the wider environment, recovering it would require undoing not just a single event, but every physical change it caused along the way. In practice, that is impossible.

This is why information cannot be erased and broken cups do not reassemble. But the implication runs deeper. Each interaction writes something permanent into the structure of the universe, whether at the scale of atoms colliding or galaxies forming.

Geometry and information turn out to be deeply connected in this view. In our work, we have showed that how spacetime curves depends not only on mass and energy, as Einstein taught us, but also on how quantum information, particularly entanglement, is distributed. Entanglement is a quantum process that mysteriously links particles in distant regions of space – it enables them to share information despite the distance. And these informational links contribute to the effective geometry experienced by matter and radiation.

From this perspective, spacetime geometry is not just a response to what exists at a given moment, but to what has happened. Regions that have recorded many interactions tend, on average, to behave as if they curve more strongly, have stronger gravity, than regions that have recorded fewer.

This reframing subtly changes the role of spacetime. Instead of being a neutral arena in which events unfold, spacetime becomes an active participant. It stores information, constrains future dynamics and shapes how new interactions can occur. This naturally raises a deeper question. If spacetime records information, could time emerge from this recording process rather than being assumed from the start?

Time arising from information

Recently, we extended this informational perspective to time itself. Rather than treating time as a fundamental background parameter, we showed that temporal order emerges from irreversible information imprinting. In this view, time is not something added to physics by hand. It arises because information is written in physical processes and, under the known laws of thermodynamics and quantum physics, cannot be globally unwritten again. The idea is simple but far-reaching.

Every interaction, such as two particles crashing, writes information into the universe. These imprints accumulate. Because they cannot be erased, they define a natural ordering of events. Earlier states are those with fewer informational records. Later states are those with more.

Quantum equations do not prefer a direction of time, but the process of information spreading does. Once information has been spread out, there is no physical path back to a state in which it was localised. Temporal order is therefore anchored in this irreversibility, not in the equations themselves.

Time, in this view, is not something that exists independently of physical processes. It is the cumulative record of what has happened. Each interaction adds a new entry, and the arrow of time reflects the fact that this record only grows.

The future differs from the past because the universe contains more information about the past than it ever can about the future. This explains why time has a direction without relying on special, low-entropy initial conditions or purely statistical arguments. As long as interactions occur and information is irreversibly recorded, time advances.

Interestingly, this accumulated imprint of information may have observable consequences. At galactic scales, the residual information imprint behaves like an additional gravitational component, shaping how galaxies rotate without invoking new particles. Indeed, the unknown substance called dark matter was introduced to explain why galaxies and galaxy clusters rotate faster than their visible mass alone would allow.

In the informational picture, this extra gravitational pull does not come from invisible dark matter, but from the fact that spacetime itself has recorded a long history of interactions. Regions that have accumulated more informational imprints respond more strongly to motion and curvature, effectively boosting their gravity. Stars orbit faster not because more mass is present, but because the spacetime they move through carries a heavier informational memory of past interactions.

From this viewpoint, dark matter, dark energy and the arrow of time may all arise from a single underlying process: the irreversible accumulation of information.

Testing time

But could we ever test this theory? Ideas about time are often accused of being philosophical rather than scientific. Because time is so deeply woven into how we describe change, it is easy to assume that any attempt to rethink it must remain abstract. An informational approach, however, makes concrete predictions and connects directly to systems we can observe, model and in some cases experimentally probe.

Black holes provide a natural testing ground, as they seems to suggest information is erased. In the informational framework, this conflict is resolved by recognising that information is not destroyed but imprinted into spacetime before crossing the horizon. The black hole records it.

This has an important implication for time. As matter falls toward a black hole, interactions intensify and information imprinting accelerates. Time continues to advance locally because information continues to be written, even as classical notions of space and time break down near the horizon and appear to slow or freeze for distant observers.

As the black hole evaporates through Hawking radiation, the accumulated informational record does not vanish. Instead, it affects how radiation is emitted. The radiation should carry subtle signs that reflect the black hole's history. In other words, the outgoing radiation is not perfectly random. Its structure is shaped by the information previously recorded in spacetime. Detecting such signs remains beyond current technology, but they provide a clear target for future theoretical and observational work.

The same principles can be explored in much smaller, controlled systems. In laboratory experiments with quantum computers, qubits (the quantum computer equivalent of bits) can be treated as finite-capacity information cells, just like the spacetime ones. Researchers have shown that even when the underlying quantum equations are reversible, the way information is written, spread and retrieved can generate an effective arrow of time in the lab. These experiments allow physicists to test how information storage limits affect reversibility, without needing cosmological or astrophysical systems.

Extensions of the same framework suggest that informational imprinting is not limited to gravity. It may play a role across all fundamental forces of nature, including electromagnetism and the nuclear forces. If this is correct, then time's arrow should ultimately be traceable to how all interactions record information, not just gravitational ones. Testing this would involve looking for limits on reversibility or information recovery across different physical processes.

Taken together, these examples show that informational time is not an abstract reinterpretation. It links black holes, quantum experiments and fundamental interactions through a shared physical mechanism, one that can be explored, constrained and potentially falsified as our experimental reach continues to grow.

What time really is

Ideas about information do not replace relativity or quantum mechanics. In everyday conditions, informational time closely tracks the time measured by clocks. For most practical purposes, the familiar picture of time works extremely well. The difference appears in regimes where conventional descriptions struggle.

Near black hole horizons or during the earliest moments of the universe, the usual notion of time as a smooth, external coordinate becomes ambiguous. Informational time, by contrast, remains well defined as long as interactions occur and information is irreversibly recorded.

All this may leave you wondering what time really is. This shift reframes the longstanding debate. The question is no longer whether time must be assumed as a fundamental ingredient of the universe, but whether it reflects a deeper underlying process.

In this view, the arrow of time can emerge naturally from physical interactions that record information and cannot be undone. Time, then, is not a mysterious background parameter standing apart from physics. It is something the universe generates internally through its own dynamics. It is not ultimately a fundamental part of reality, but emerges from more basic constituents such as information.

Whether this framework turns out to be a final answer or a stepping stone remains to be seen. Like many ideas in fundamental physics, it will stand or fall based on how well it connects theory to observation. But it already suggests a striking change in perspective.

The universe does not simply exist in time. Time is something the universe continuously writes into itself.

Scientists are investigating the origin of one of the most energetic particles ever seen hitting Earth from space. The Amaterasu particle, named for the Japanese sun goddess, was first detected in 2021, carrying 40 million times more energy than particles accelerated by the world's largest and most powerful particle accelerator, the Large Hadron Collider (LHC).

Amaterasu is an example of a cosmic ray, energetic charged particles that race through space at nearly the speed of light. It is the second most energetic cosmic ray ever detected after the "Oh-My-God" particle, detected in 1991. Such high-energy particles are extremely rare, which means scientists would very much like to understand their origins — currently thought to involve the wreckage of supernova explosions and central regions of galaxies dominated by feeding supermassive black holes.

Deepening the puzzle of Amaterasu is the fact that it seems to have emerged from the "Local Void," a region of space devoid of galaxies and the extreme environments and violent conditions thought be the factories that launch high-energy cosmic rays.

Enter Francesca Capel and Nadine Bourriche, researchers at the Max Planck Institute for Physics, who have found that Amaterasu's origins may not be locked within the local void. Instead, this highly energetic particle may have emerged from a range of relatively local cosmic environments.

"Our results suggest that, rather than originating in a low-density region of space like the Local Void, the Amaterasu particle is more likely to have been produced in a nearby star-forming galaxy such as M82," Bourriche said in a statement.

The duo's findings emerged from a novel data-driven approach that allowed them to trace the possible path of Amaterasu through the cosmos. The team considered the journey of this high-energy cosmic ray through space under the influence of magnetic fields using a statistical technique called in three dimensions called Approximate Bayesian Computation.

"This approach works by comparing the results of realistic, physics-based simulations with actual observational data to infer the most probable source locations," Bourriche said.

The result of this analysis was a collection of "probability maps" all tracking back to possible Amaterasu origin points beyond the Local Void. The research has implications beyond the origins of this extraordinary goddess particle, however. The team's findings could help better pin down which powerful and violent cosmic events serve as high-energy cosmic ray factories.

"Exploring ultra-high-energy cosmic rays helps us to better understand how the Universe can accelerate matter to such energies, and also to identify environments where we can study the behavior of matter in such extreme conditions," Capel said. "Our goal is to develop advanced statistical analysis methods to exploit the available data to its full potential and gain a deeper understanding of the possible sources of these energetic particles."

The team's results were published on Jan. 28 in The Astrophysical Journal.

Using the world's most powerful particle accelerator, CERN's Large Hadron Collider, scientists have discovered that the trillion-degree hot primordial "soup" that filled the cosmos for mere millionths of a second after the Big Bang actually behaved like a liquid, making it akin to a literal soup.

This primordial soup was composed of a plasma of particles called quarks and gluons that rapidly cooled, causing these two types of particles to fuse and create fundamental particles like protons and neutrons, which today sit at the heart of all atoms that make up the matter all around us. Today, quarks and gluons are only found locked up in the particles they comprise, with one exception. By smashing together heavy atoms of lead traveling at near-light speeds using the Large Hadron Collider (LHC), scientists can create a high-energy environment that briefly frees gluons and quarks from this atomic bondage, recreating the quark-gluon plasma of the early universe.

Using the 17-mile (27 kilometers) long accelerator located near Geneva, Switzerland, a team of researchers from the Massachusetts Institute of Technology (MIT) generated quark-gluon plasma. Within this pseudo-primordial soup, they observed quarks creating "wakes" as they raced through the plasma, akin to the trail created by a boat as it travels through water. This is the first evidence that this quark-gluon plasma reacts to particles speeding through it in the same way that liquid does, splashing and rippling, acting as a single unified liquid rather than randomly scattering as individual particles would. This cohesion means the plasma-quark gluon wasn't just a fluid, a term which can include a liquid or a gas, but acted as a liquid. Scientists say it could settle some long-standing questions about what the universe's earliest 'stuff' was like.

"It has been a long debate in our field on whether the plasma should respond to a quark," team member Yen-Jie Lee, professor of physics at MIT, said in a statement. "Now we see the plasma is incredibly dense, such that it is able to slow down a quark, and produces splashes and swirls like a liquid. "So quark-gluon plasma really is a primordial soup."

To observe the wakes created in quark-gluon plasma by travelling particles, Lee and colleagues used the LHC's Compact Muon Solenoid (CMS) detector to develop a technique that also allowed them to measure the size, speed, and extent of these wakes, and how long it takes for them to ebb and dissipate. This information could be critical to better understanding both the properties of quark-gluon plasma and how it behaved during the first microseconds of the cosmos.

"Studying how quark wakes bounce back and forth will give us new insights on the quark-gluon plasma's properties," Lee said. "With this experiment, we are taking a snapshot of this primordial quark soup."

You might want to blow on this soup for a while

The quark-gluon plasma wasn't just the first liquid to have existed in the universe, but with a temperature of many trillions of degrees, it is also the hottest liquid that ever existed. The primordial soup is considered to have been a near-perfect liquid, which means its quark and gluon contents flowed together as a smooth, frictionless fluid.

Though there are many models of quark-gluon plasma, one theory, dubbed the "hybrid model," suggests that this primordial soup should react like any other liquid when particles pass through it at speed. In the hybrid model, a jet of quarks moving through the quark-gluon plasma should create a wake as it causes this plasma ocean to ripple and splash.

There have been many experiments at the LHC and other particle accelerators that have attempted to see this effect in action. Those experiments are only made possible through slamming heavy charged atoms, or heavy ions, together at near light-speed, which can generate a droplet of primordial soup that lives for no more than a quadrillionth of a second. Scientists continue to attempt to take snapshots of this primordial soup to understand the characteristics of quark-gluon plasma.

In the attempt to identify wakes in the quark-gluon plasma, scientists have been hunting for pairings of quarks and their antimatter counterparts known as anti-quarks. When a quark races through plasma, an anti-quark should exist, travelling at precisely the same speed but in the opposite direction. Both particles, according to the hybrid model, should create detectable wakes. Sounds simple enough, but there's a fly in this soup.

"When you have two quarks produced, the problem is that, when the two quarks go in opposite directions, the one quark overshadows the wake of the second quark," Lee explained. This team realized that finding the wake of a quark would be simpler if there were no second quark obscuring it.

"We have figured out a new technique that allows us to see the effects of a single quark in the quark-gluon plasma, through a different pair of particles," Lee added.

Boson croutons

Instead of hunting for quark pairs, Lee and colleagues looked for quarks travelling in unison with a neutral elementary particle called a Z-boson, which has little effect on its surroundings. The benefit of Z-bosons is that they have a specific energy, and that makes them comparatively easy to spot.

"In this soup of quark-gluon plasma, there are numerous quarks and gluons passing by and colliding with each other," Lee said. "Sometimes when we are lucky, one of these collisions creates a Z boson and a quark, with high momentum."

In these circumstances, the quark and Z-boson should slam into each other and bounce off in opposite directions, with the quark leaving a wake, but with the Z-boson not leaving one due to its lack of impact on the surrounding quark-gluon plasma. That means any ripples spotted in this situation are made by a quark alone.

After observing 13 billion LHC collisions, Lee and the team identified around 2,000 instances in which a Z-boson was produced. During these events, the scientists consistently observed a fluid-like pattern of splashes travelling in the opposite direction of the Z bosons they detected. That, they determined, was the sought-after quark wake effect. Indeed, the patterns observed conformed to ripple-predictions made by the hybrid model of quark-gluon plasma.

"We've gained the first direct evidence that the quark indeed drags more plasma with it as it travels," Lee concluded. "This will enable us to study the properties and behavior of this exotic fluid in unprecedented detail."

The team's research was published in the journal Physics Letters B.

In 1971, astronaut David Scott stood on the lunar surface, holding a hammer and a feather, and in the vacuum of the moon, he let them go. They struck the gray dust at the exact same time. It was a poetic nod to Galileo, who, centuries earlier, disproved the Aristotelian notion that heavy objects "want" to be on the ground more than light ones do.

This wasn't just a parlor trick for the cameras; it was a demonstration of the weak equivalence principle, which is the bedrock of general relativity. It states that all objects, regardless of their mass or internal composition, fall at the exact same rate in a gravitational field. When Einstein was building his masterpiece theory, he didn't try to explain why this happens. He simply assumed it was a fundamental rule and moved on.

But what if there's an astrophysical creature that refuses to play by the rules? What if we dropped something so exotic, it wasn't even on Einstein's radar? We need to talk about antimatter.

To understand the allure of falling antimatter, we have to look at the history of its discovery. In the 1920s, physicist Paul Dirac was trying to force two very different worlds — quantum mechanics (the rules of the very small) and special relativity (the rules of the very fast) — to play together.

Dirac found an equation that worked, but it had a quirk. Just as the square root of 4 can be both 2 and -2, his equation offered two solutions for the energy of a particle: one positive and one negative. This was a problem. Positive energy has a "ground floor" at zero, but negative energy is a basement of a basement with no bottom.

Dirac's solution was what became known as the "Dirac sea." He imagined outer space not as an empty vacuum but as a filled "ocean" of negative energy states. If you kick one of these invisible particles into the positive realm, you leave behind a hole. That hole behaves like a normal particle but with an opposite charge. It was the first time a particle was predicted by pure math before being seen in a lab. We call it antimatter.

Why focus on antimatter to test gravity? Because antimatter is the bridge to the greatest divide in physics. General relativity (gravity) and quantum mechanics (everything else) famously do not get along. They speak different languages and live in different neighborhoods. Because antimatter is a pure product of the quantum world, it is the perfect candidate to test Einstein's theory of gravity.

However, this is a nightmare, for three reasons:

1. When matter and antimatter touch, they annihilate in a flash of pure energy.
2. Nature doesn't just hand us antimatter; we have to build it in advanced laboratories.
3. Compared with the electromagnetic force, gravity is incredibly weak.

To overcome these hurdles, scientists at CERN's ALPHA-g experiment had to get creative. First, they made neutral antihydrogen by pairing antiprotons with positrons (anti-electrons). Because these antiatoms are neutral, they aren't pushed around by electricity.

The team caught about a hundred of these antiatoms in a Penning trap, which is a magnetic bottle that holds them in place because, while neutral, they still act like tiny bar magnets. Then, using lasers, the researchers chilled the atoms to near absolute zero to stop them from jiggling.

Then came the moment of truth: They slowly turned down the magnetic field.

If antimatter ignored the weak equivalence principle, the atoms might have drifted upward, repelled by Earth. If Einstein was right, they should tumble downward. The researchers waited for the flash of annihilation as the antiatoms escaped the trap and hit the walls of the container. After they filtered out the noise of stray cosmic rays, the results were clear: Roughly 80% of the antiatoms fell through the bottom of the trap.

Antimatter falls down. It's an anti-climactic (ha ha) result in the best way possible. It means the weak equivalence principle holds firm and Einstein's vision of a universal gravitational response remains unblemished.

However, the case isn't entirely closed. While we know antimatter falls down, we don't yet know if it falls at the exact same acceleration as regular matter does. If there is even a 1% difference in the speed of the fall, it would signal a total revolution in physics — a sign that gravity treats mirror matter differently. But for now, the universe remains a place where hammers, feathers and antihydrogen all race to the floor at the same speed.

New research puts forward compelling new evidence that dark matter interacts with cosmic "ghost particles" called neutrinos. If that is the case, then this interaction could pose a serious challenge for the standard model of cosmology, our current best model of the universe.

Neutrinos earn their spooky nickname due to the fact that as these chargeless and virtually massless particles travel through space at near the speed of light, they barely interact with other particles, ghosting their way through solid objects like planets. In fact, the interactions between these particles and other matter are so rare and fleeting that every second, around 100 trillion neutrinos stream through your body without you feeling a thing. Dark matter is similar; even though it accounts for around 85% of the matter in the universe, whatever comprises dark matter also barely interacts with ordinary matter and light, if at all. In fact, effectively invisible, dark matter can only be inferred due to its interaction with gravity and the effect this has on light and conventional matter.

However, new findings from a team of researchers from the University of Sheffield suggest that a slight interaction, in the form of a minor exchange of momentum, exists between dark matter and neutrinos. That contradicts the so-called "Lambda Cold Dark Matter (LCDM)" model that attempts to explain the universe's structure and evolution, which says that dark matter and neutrinos exist independently and do not interact with each other.

The evidence for this potentially paradigm-shift-inducing suggestion comes from observations of the universe in its current state, conducted by the Dark Energy Camera on the Victor M. Blanco Telescope in Chile, from galaxy maps created by the Sloan Digital Sky Survey, and details of the universe's distant past gathered by both the Atacama Cosmology Telescope (ACT) and the European Space Agency (ESA) Planck Telescope spacecraft.

These observations have revealed that the modern universe is less "clumpy" than it should be. This cosmic conundrum could be explained by interactions between dark matter and neutrinos, which would impact the way cosmic structures like galaxies form and evolve.

"Our results address a long-standing puzzle in cosmology. Measurements of the early universe predict that cosmic structures should have grown more strongly over time than what we observe today," team member Eleonora Di Valentino of the University of Sheffield said in a statement. “However, observations of the modern universe indicate that matter is slightly less clumped than expected, pointing to a mild mismatch between early- and late-time measurements. This tension does not mean the standard cosmological model is wrong, but it may suggest that it is incomplete.

"Our study shows that interactions between dark matter and neutrinos could help explain this difference, offering new insight into how structure formed in the universe," Di Valentino added.

The next step is to test this idea, something that the team thinks is possible using precise observations from future telescopes of a cosmic fossil called the Cosmic Microwave Background (CMB), a leftover from an event in the universe shortly after the Big Bang. Astronomers could also test this theory using a specific effect that objects of great mass have on space, and therefore light, a phenomenon called "gravitational lensing." This would allow them to better measure the distribution of ordinary matter and dark matter.

"If this interaction between dark matter and neutrinos is confirmed, it would be a fundamental breakthrough," team member William Giarè of the University of Hawaii, said. "It would not only shed new light on a persistent mismatch between different cosmological probes, but also provide particle physicists with a concrete direction, indicating which properties to look for in laboratory experiments to help finally unmask the true nature of dark matter."

The team's research was published on Jan. 2 in the journal Nature Astronomy.

You are currently making a conscious, willful decision to read this article. But physics says every action has a cause. So did you really make this decision as freely as you thought?

One of the bedrock philosophical concepts under all of physics is something called causal determinism. It says that every effect has a cause, and that if you know the current state of a system, you can use the power of physics to predict how it behaves. If effects happened without causes, then there wouldn't be much need for physics. And if we couldn't predict how systems would behave, then we wouldn't be very good at our jobs.

With this philosophy, physics has made enormous progress in advancing our understanding of the universe, from subatomic quantum systems to the Big Bang. And a part of that universe contains these weird things called brains that have the curious property of consciousness and the ability to freely make decisions.

So, at first glance, it seems like our understanding of physics forbids free will. We don't really have a choice, because if we had perfect knowledge of all the molecules and electrical activity in our brains, then we must be able to determine our choices in advance.

But there are three aspects of physics that add some wrinkles to this line of thinking.

The first is chaos theory. Some systems are easy to predict. But others, like double pendulums and weather patterns, are much harder to tackle. In these special kinds of systems, even a minuscule amount of uncertainty in the measurement of the initial state of a system very quickly compounds into complete ignorance about its future behavior. Strangely, these systems are perfectly deterministic; causes always lead smoothly to effects, so there's no mystery there. But they are impossible to predict well into the future.

The second wrinkle comes from quantum mechanics, which tells us that it's impossible to predict the outcomes of many kinds of experiments involving subatomic particles. Probabilities rule the day there, and the best we can do is assign chances to certain outcomes. Quantum mechanics is still a deterministic theory of nature — but again, it places a layer of ignorance over our understanding. We can't say for sure where a particle will go or how it will behave; we can only say what might happen. But it's not clear if the probabilistic rules of quantum mechanics apply to things like neural connections in the brain and the rise of consciousness, which is an emergent phenomenon.

The last wrinkle is exactly that: emergence. Fundamental descriptions of nature do not automatically guarantee an understanding of more complex systems. For example, we have an incredibly sophisticated theory of particle physics, based on quantum field theory, but that sophisticated theory works only when describing quantum systems. We have no quantum field theory description of how a star forms, or why chocolate tastes so good. We have to adopt other laws and theories to describe the systems as a whole.

None of these wrinkles gives a clear-cut yes-or-no answer to the question of free will. But they do show that our understanding of physics is limited. Most philosophers believe in a class of ideas under the heading of "compatibilism," which says that free will and physics can live together in harmony. It might be that our understanding of nature is not yet sophisticated enough to explain how free will can work with causal determinism.

In other words, if we work hard enough, we might someday reach a level of understanding that preserves causal determinism and all the usual physics goodness while including things like free will in a framework that makes sense.

Either way, we have no choice but to keep asking.

Exotic, dark astrophysical objects may be hiding in interstellar space, and a new proposal outlines how to find them: stare really, really hard.

We don't know what dark matter is, even though we strongly suspect it exists. We see circumstantial evidence for it everywhere, from the rotation rates of galaxies to the growth of the largest structures in the cosmos. For decades, cosmologists have thought dark matter is some sort of exotic particle that was previously unknown to the Standard Model of particle physics. This strange particle would not interact with light, or really much of anything else, except through its gravitational influence.

But searches for these dark matter particles have come up empty so far, driving theorists to get more creative with their ideas.

It could be that dark matter isn't made of zillions of tiny particles flying through the universe. Instead, it could be composed of bunched-up collections of much larger objects. In particular, the researchers behind a new study, published in November 2025 in the open access server arXiv, investigated two kinds of exotic objects.

The first is known as a boson star. In this model, dark matter is made of an ultra-ultra-ultra light particle — potentially millions of times lighter than neutrinos, the lightest known particles. They would be so light that their quantum nature would make them appear more like waves at galactic scales than like individual particles. But these waves would sometimes bunch up and collect on themselves, pulling together with their own gravity, without collapsing.

Another possibility is called Q-balls. In this model, dark matter isn't a particle at all but rather a quantum field that soaks all of space and time. Due to a special property of this field, it could occasionally pinch off, creating gigantic, stable, lump-like balls that wander the cosmos like a floating piece of flour in gravy that hasn't been mixed well.

Both boson stars and Q-balls, which live under the more general heading of exotic astrophysical dark objects (EADOs), are difficult to detect. They're large — roughly star-size — but they do not emit light of their own, making them nearly invisible in our scans of the cosmos.

But astronomers have discovered a way that EADOs can betray their presence: microlensing. If a Q-ball or boson star were to pass between us and a distant star, the strong gravity of the EADO would cause the light from the star to act as a gravitational lens. From our perspective, it would make the star appear to suddenly jump into position and then quickly return to normal.

So all we'd have to do is stare at a whole bunch of stars for a really long time and hope we get lucky. Thankfully, we have just the instrument for the job. The Gaia space telescope's mission was to do just that: stare at a whole bunch of stars for a really long time.

The astronomers behind the study propose a campaign using Gaia data to search for Q-balls and boson stars by looking for their unique, "smoking gun" signal of sudden jumps in stellar positions. Depending on how many are out there, Gaia may have observed up to several thousand EADOs.

But if they're not out there, then this same campaign would produce stringent limits on Q-balls' and boson stars' contributions to the overall dark matter picture. No matter what, staring into the dark would teach us something.

How do you search for invisible hypothetical particles? One way is to see how quickly they could kill white dwarfs — the dense, leftover cores of dead stars.

In recent years, astronomers have become increasingly interested in a theoretical particle known as the axion, which was concocted decades ago to solve a challenging problem with the strong nuclear force. After initial attempts to find it in particle collider experiments turned up empty, however, the idea sunk into the background.

But further research revealed that the axion could be a contender to explain the mystery of dark matter. Theorists realized that there might be ways for axions to flood the universe but so far evade direct detection.

Just because this little particle would be largely invisible, it doesn't mean it would go completely unnoticed in the universe. In a pre-print paper published in November 2025 in the open access server arXiv, researchers reported a way to test axion models using old archival data from the Hubble Space Telescope. Although they didn't find any evidence for axions, they beat other attempts and gave us a much clearer picture of what is and isn't allowed in this universe.

The targets for this study were white dwarfs — the dense, dim cores of dead stars. A single white dwarf can pack the mass of the sun into an object smaller than Earth, making white dwarfs among the most exotic objects in the universe. Crucially, white dwarfs support themselves against collapse through something called electron degeneracy pressure, in which a huge sea of free-floating electrons resists collapse because, according to quantum mechanics, electrons can never share the same state.

Some models of how axions might behave say these particles could be created by electrons: If an electron were moving quickly enough, it would trigger the formation of an axion. And because the electrons deep inside a white dwarf are moving very, very quickly — at nearly the speed of light — as they buzz around in their tight confines, they could produce a lot of axions.

The axions would then go speeding off, leaving the white dwarf altogether. This production of escaping axions would rob the white dwarf of energy. And because white dwarfs don't produce energy on their own, this would cause them to cool off faster than they would otherwise.

The researchers fed this model of axion cooling into a sophisticated software suite that can simulate the evolution of stars and how their temperature and brightness change as their interiors evolve.

This model allowed the researchers to predict the typical temperature of a white dwarf, given its age, both with and without axion cooling. With the results in hand, they turned to data of the globular cluster 47 Tucanae collected with Hubble. Global clusters are crucial because all of the white dwarfs in them were born at roughly the same time, giving the astronomers a large sample to study.

In short, the researchers found no evidence for axion cooling in the white dwarf population. But their results did give brand-new constraints on the ability for electrons to produce axions: They can't do it more efficiently than once every trillion chances.

This result doesn't rule out axions entirely, but it does say it's unlikely that electrons and axions directly interact with each other. So, if we're going to keep searching for axions, we're going to have to find even more clever ways to look.

In the late 1970s, legendary physicist John Wheeler proposed a radical question: Exactly when does the universe notice that we're paying attention to a quantum experiment? And does it really matter? The answer goes against everything we thought we knew.

Wheeler's thought experiment, which eventually became a real experiment, involved the famous double-slit experiment. Let's say you have a source of light and a screen with two thin, vertical slits. When you shine the light through the slits, the light acts like a wave. It interferes with itself, causing a ripple-like pattern on a far wall, with strips of brightness alternating with darkness. This is exactly how waves work, and if you ever find yourself in a harbor with two narrow openings, you'll see the waves washing up onshore with a similar pattern.

Now, let's say you make the light really weak — so weak that, eventually, only one photon at a time goes through the double slit. Amazingly, even though each individual photon acts like a particle — it hits the far wall in one specific spot — after enough photons arrive, the same interference pattern emerges. The usual conclusion is that the wave nature of a single photon interferes with itself to create the pattern.

Now, let's add one more layer. Let's say you introduce a detector to the slits, to figure out which slit the photon actually passed through on its way through the screen. When you do this, the wave nature of the photon goes away. You get to see which slit the photon passed through — but it only ever acts like a particle, and you never get an interference pattern on the far wall.

When we design a quantum experiment, we must choose to investigate either the wave nature or the particle nature of photons — but we can't do both. OK, it's weird. But so far, it's the standard sort of quantum weirdness.

Wheeler upped the ante. He asked what would happen if you were to introduce a delay. What if you were to insert a detector at the slits after the photon had already passed through?

Wheeler proposed a helpful analogy. Imagine a distant light source, like a quasar, that sends light traveling for billions of light-years. Some of that light heads right for us, while some beams follow a curved path through a gravitational lens, like a massive cluster. Both beams arrive on Earth at the same time, and we can set up an experiment to interfere with those beams. In that experiment, we can choose to study either the wave nature or the particle nature of light.

Wheeler guessed the answer. He was right, and his correctness was later borne out by experiments. Even when we make a delayed choice, the photons somehow keep track of that and alter whether they're going to make an interference pattern.

How does this work? We're making our choice at the final leg of the light's journey. How did the photons "know" what choice we were going to make ahead of time? It seems as if our choice in the future went back in time to alter how the photons behaved in the past.

An updated version of the experiment, known as the "delayed choice quantum eraser," makes this even crazier. In this experiment, the photons pass through the slits. Then, the experiment decides whether to monitor the slits. Well after the photons have struck the screen, the experimenter decides to read the information. If the experimenter reads the information about which slit the photon passed through, there will never be an interference pattern. If the experiment throws away the information, an interference pattern emerges.

Remember, all of this is after the photon has already hit the screen.

Wheeler taught us how to think about this. He argued that it doesn't make sense to talk about photons "in flight." We only have measurements and observations — the final results of our experiments. The order of the events and what happened during the experiment itself don't matter. Photons aren't really in flight in the way we think of it, and the wave-particle duality of photons doesn't make sense in the way we usually think about things.

What we get, whether particles or waves, is what we get. And it's only once we make that measurement that nature reveals what aspect of reality to show us.

Scientists have inched a step closer to solving an enduring mystery in physics — why the universe contains any matter at all — thanks to a newly combined analysis from two of the world's leading neutrino experiments.

By pooling nearly 16 years of measurements, the NOvA experiment in the United States and the T2K experiment in Japan have produced the most precise picture yet of how neutrinos and their antimatter twins transform as they travel. The results, published on Oct. 22 in the journal Nature, sharpen the search for subtle differences in how these particles behave — differences that may help explain why matter prevailed over antimatter in the early universe.

If the two are perfectly symmetric, according to the Standard Model of particle physics, the Big Bang should have created equal amounts of matter and antimatter nearly 14 billion years ago. And in fact, because matter and antimatter annihilate on contact, a perfectly balanced universe should have ended in a wash of pure energy. Yet, today's cosmos is overwhelmingly made up of matter, suggesting some subtle mechanism gave matter a slight and still-mysterious advantage early on.

A prime suspect for tipping the scales is the neutrino, a ghostly, almost massless particle that permeates the universe but rarely interacts with anything. This is why scientists often refer to them as "ghost particles." Physicists have long wondered whether neutrinos and antineutrinos behave differently in ways experiments can detect. Even a subtle mismatch, known as CP violation, could illuminate how matter gained its cosmic edge.

"While there is still more to understand, the critical experimental question is clear: can we see this symmetry violation in neutrinos, and if so, how big is it?" Ryan Patterson, a physics professor at the California Institute of Technology and co-lead of the NOvA team, told Space.com.

Neutrinos change 'flavor'

Part of what makes neutrinos so elusive — and so intriguing — is their ability to change identity. They exist in three "flavors," and as they move through space, they oscillate among these types because each flavor is a blend of three mass states. As neutrinos travel, those underlying mass states shift, causing the particles to morph from one flavor to another.

"If you think of the flavors as being like strawberry, chocolate and vanilla, this would be like finding your strawberry ice cream cone turned to chocolate on your way home," a recent Caltech statement explains.

By tracing these flavor changes, scientists can measure the tiny mass differences that govern neutrino oscillations — and by comparing neutrinos with antineutrinos behaviors, they can probe CP violation.

To do this, the NOvA experiment (short for NuMI Off-axis ν_e Appearance) fired a beam of neutrinos from Fermilab near Chicago to a detector 500 miles (800 kilometers) away in Minnesota. Across the Pacific, Japan's T2K (short for Tokai-to-Kamioka) experiment sent its own beam 183 miles (295 kilometers) from the Japan Proton Accelerator Research Complex in Tokai to the massive Super-Kamiokande detector, buried 0.6 miles (about 1 kilometer) beneath a mountain in Kamioka.

Because the experiments operate at different distances and energies, each captures complementary features of neutrino oscillations. Combining their data allows researchers to isolate the subtle parameters that control how neutrinos transform.

A key result of the joint analysis is a sharply refined measurement of one of the most fundamental oscillation parameters, known as the neutrino mass splitting. The collaboration has now constrained this value to just 2 percent, making it one of the most precise measurements ever reported.

"It underlies all the other measurements we make," Patterson said. He added that this progress also opens up avenues to determine the neutrino mass hierarchy, the still-unknown ordering of the three neutrino mass states.

"As of today, we accept the existence of three neutrino families, each associated with distinct masses," Federico Sanchez, an experimental physicist specializing in neutrino physics and a longtime T2K collaborator, told Space.com. "But we still lack a fundamental understanding of why there are precisely three, not two, four or more — and why their mass differences take the specific values we observe."

"The mass hierarchy is not only a cornerstone for many theoretical calculations and predictions but also provides a tangible result that can be directly compared with existing models," he added.

The mass hierarchy affects how neutrinos and antineutrinos oscillate differently — a key part of the search for CP violation. In what is called normal hierarchy, one of the three known neutrino "flavors," muon neutrinos, transform into electron neutrinos more readily than their antimatter counterparts, muon antineutrinos, transform into electron antineutrinos. In the inverted hierarchy, that pattern flips.

The new joint analysis isn't able to say which hierarchy nature prefers. But if future data show the hierarchy is inverted, Patterson says the current dataset already hints that neutrinos may violate CP symmetry. If that data show the normal hierarchy is correct, even more data will be needed to tease apart the competing effects.

"Neutrino physics is a strange field. It is very challenging to isolate effects," Kendall Mahn, a professor at Michigan State University and T2K co-spokesperson, said in the Caltech statement. "Combining analyses allows us to isolate one of these effects, and that's progress."

A new shared 'language' for neutrino science

Beyond the immediate physics results, researchers say one of the collaboration's most significant achievements is the development of an initial common framework — a shared "language" for how neutrino interactions are described across experiments.

Although all experiments are grounded in the same underlying physics, each makes different approximations and methodological choices based on its unique detector design. Among the most critical assumptions are those involving how neutrinos interact with matter, which is essential for accurately reconstructing their energy, and how many neutrinos are produced at a given energy, said Sanchez.

Even small differences in these models can affect the interpretation of oscillation patterns, he noted. By harmonizing these assumptions, the collaboration has created a starting template that future experiments can adopt to ensure their findings are directly comparable.

"Precision in these measurements is critical, as even subtle discrepancies could signal deviations from the model — potentially revealing new physics," Sanchez told Space.com. "The more precise the agreement is the more confident we are that our description is correct."

The timing couldn’t be better. Scientists say such a unified framework will be essential for the next generation of ultra-sensitive experiments — the Deep Underground Neutrino Experiment (DUNE) in Illinois and South Dakota, and the Hyper-Kamiokande in Japan — are under construction and expected to begin operations in 2028. These next-generation detectors will perform measurements far more sensitive than NOvA or T2K, potentially offering definitive evidence of CP violation in the next decade.

And if neutrinos truly do treat matter and antimatter differently, scientists may finally uncover the long-sought reason the universe exists in the form we know today.

A study about these results was published on Oct. 22 in the journal Nature.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

The nature of time has plagued thinkers for as long as we've tried to understand the world we live in. Intuitively, we know what time is, but try to explain it, and we end up tying our minds in knots.

St. Augustine of Hippo, a theologian whose writings influenced western philosophy, captured a paradoxical challenge in trying to articulate time more than 1,600 years ago:

"What then is time? If no one asks me, I know; if I want to explain it to a questioner, I do not know."

Nearly a thousand years earlier, Heraclitus of Ephesus offered a penetrating insight. According to classical Greek philosopher Plato’s Cratylus:

"Heraclitus is supposed to say that all things are in motion and nothing at rest; he compares them to the stream of a river, and says that you cannot go into the same water twice."

Superficially, this can sound like another paradox — how can something be the same river and yet not the same? But Heraclitus adds clarity, not confusion: the river — a thing that exists — continuously changes. While it is the same river, different waters flow by moment to moment.

While the river's continuous flux makes this plain, the same is true of anything that exists — including the person stepping into the river. They remain the same person, but each moment they set foot in the river is distinct.

How can time feel so obvious, so woven into the fabric of our experience, and yet remain the bane of every thinker who has tried to explain it?

An issue of articulation

The key issue isn't one most physicists would even consider relevant. Nor is it a challenge that philosophers have managed to resolve.

Time itself isn't difficult to grasp: we all understand it, despite our persistent struggle to describe it. As Augustine sensed, the problem is one of articulation: a failure to precisely draw the right boundaries around the nature of time both conceptually and linguistically.

Specifically, physicists and philosophers tend to conflate what it means for something to exist and what it means for something to happen — treating occurrences as if they exist. Once that distinction is recognized, the fog clears and Augustine's paradox dissolves.

The source of the issue

In basic logic, there are no true paradoxes, only deductions that rest on subtly mishandled premises.

Not long after Heraclitus tried to clarify time, Parmenides of Elea did the opposite. His deduction begins with a seemingly valid premise — "what is, is; and what is not, is not" — and then quietly smuggles in a crucial assumption. He claims the past is part of reality because it has been experienced, and the future must also belong to reality because we anticipate it.

Therefore, Parmenides concluded, both past and future are part of "what is," and all of eternity must form a single continuous whole in which time is an illusion.

Parmenides' pupil, Zeno, devised several paradoxes to support this view. In modern terms, Zeno would argue that if you tried walking from one end of a block to the other, you'd never get there. To walk a block, you must first walk half, then half of what remains, and so on — always halving the remaining distance, never reaching the end.

But of course you can walk all the way to the end of the block and beyond — so Zeno's deduction is absurd. His fallacy lies in removing time from the picture and considering only successive spatial configurations. His shrinking distances are matched by shrinking time intervals, both becoming small in parallel.

Zeno implicitly fixes the overall time available for the motion — just as he fixes the distance — and the paradox appears only because time was removed. Restore time, and the contradiction disappears.

Parmenides makes a similar mistake when claiming that events in the past and future — things that have happened or that will happen — exist. That assumption is the problem: it is equivalent to the conclusion he wants to reach. His reasoning is circular, ending by restating his assumption — only in a way that sounds different and profound.

Space-time models

An event is something that happens at a precise location and time. In Albert Einstein's theories of relativity, space-time is a four-dimensional model describing all such occurrences: each point is a particular event, and the continuous sequence of events associated with an object forms its worldline — its path through space and time.

But events don't exist; they happen. When physicists and philosophers speak of space-time as something that exists, they're treating events as existent things — the same subtle fallacy at the root of 25 centuries of confusion.

Cosmology — the study of the whole universe — offers a clear resolution.

It describes a three-dimensional universe filled with stars, planets and galaxies that exist. And in the course of that existence, the locations of every particle at every instance are individual space-time events. As the universe exists, the events that happen moment by moment trace out worldlines in four-dimensional space-time — a geometric representation of everything that happens during that course of existence; a useful model, though not an existent thing.

The resolution

Resolving Augustine's paradox — that time is something we innately understand but cannot describe — is simple once the source of confusion is identified.

Events — things that happen or occur — are not things that exist. Each time you step into the river is a unique event. It happens in the course of your existence and the river's. You and the river exist; the moment you step into it happens.

Philosophers have agonized over time-travel paradoxes for more than a century, yet the basic concept rests on the same subtle error — something science fiction writer H.G. Wells introduced in the opening of The Time Machine.

In presenting his idea, the Time Traveller glides from describing three-dimensional objects, to objects that exist, to moments along a worldline — and finally to treating the worldline as something that exists.

That final step is precisely the moment the map is mistaken for the territory. Once the worldline, or indeed space-time, is imagined to exist, what’s to stop us from imagining that a traveller could move throughout it?

Occurrence and existence are two fundamentally distinct aspects of time: each essential to understanding it fully, but never to be conflated with the other.

Speaking and thinking of occurrences as things that exist has been the root of our confusion about time for millennia. Now consider time in light of this distinction. Think about the existing things around you, the familiar time-travel stories and the physics of space-time itself.

Once you recognize ours as an existing three-dimensional universe, full of existing things, and that events happen each moment in the course of that cosmic existence — mapping to space-time without being reality — everything aligns. Augustine's paradox dissolves: time is no longer mysterious once occurrence and existence are separated.

In 1919, physicist Theodor Kaluza hypothesized that extra dimensions might solve some outstanding problems in physics. And while we haven't found any evidence yet for anything outside our normal four-dimensional space-time, there are still plenty of intriguing options worth exploring.

One of the biggest puzzles facing modern physics is the "hierarchy problem." Basically, the force of gravity is way too weak. It's billions upon billions of times weaker than any of the other fundamental forces, and we have no idea why.

One weird possibility is that gravity gets to do something special that the other forces don't. Perhaps there are more dimensions than our familiar space-time — all of the other forces are stuck to space-time, but gravity gets to spread out to extra dimensions. This would dilute gravity so much that it would make it appear weak in our normal everyday experience.

But this opens up a major question of its own: Where, exactly, are these extra dimensions? We don't feel, sense or detect any extra freedoms of movement. The only answer is that the extra dimensions must be curled up on each other at scales so small that we don't notice them. When we move around in the universe, we're actually circumnavigating all of those curled-up dimensions trillions of times over with even the smallest of movements. We don't notice, and life proceeds as normal.

String theorists have long used the ideas of extra dimensions to make their theory work. But the ability to explain the weakness of gravity uses the same fundamental concept, without dragging string theory along for the ride. To make gravity as weak as it is, the extra dimensions must be roughly one-tenth of a millimeter across, which is absolutely huge when it comes to subatomic processes. And the only reason we haven't noticed such large extra dimensions is that only gravity gets to experience them.

Surprisingly, there are ways to peer into hidden dimensions without having to access them directly. Imagine rolling up a tube of paper really tightly and then sending a massless particle, like a photon, down the edge of the tube. That particle will travel lengthwise, but it will also go around the circumference of the tube.

If you look at the tube from far enough away, you won't be able to see its curled-up dimension. You will see the photon making its way down, but because some of its motion will be in a dimension we can't see, it will appear to move more slowly than light. But particles that are slower than light have mass, which means if photons could access extra dimensions, they wouldn't be massless at all.

We strongly suspect that gravity is carried by massless particles called gravitons. Those gravitons would travel at the speed of light, but if they could access extra dimensions, they would instead appear massive. And because of the weird rules of quantum mechanics and the wave nature of particles, we would actually see an infinite variety of graviton masses.

So the key to unlocking extra dimensions is to run high-energy particle collider experiments and see if any massive graviton-like particles pop up.

But despite physicists' searches, we haven't found any. This doesn't rule out extra dimensions, but it does make the idea unappealing. To fit within current observational constraints, the extra dimensions have to be really, really tiny — far tinier than needed to explain the weakness of gravity.

But there may be a way. In 1999, physicists Lisa Randall and Raman Sundrum extended the idea of extra dimensions. Instead of making them flat, Randall and Sundrum allowed the extra dimensions to have curvature. This flexibility allows for the dimensions to be big enough to explain why gravity is weak, but it makes the gravitons undetectable to current particle colliders.

This is good news and bad news; it allows the whole extra-dimensions shtick to solve the hierarchy problem while evading current experimental constraints.

So while it's a cool idea, it's currently not supported by any evidence. But it's still fun to imagine extra dimensions to the universe hidden in plain sight.

A new discovery suggests gravitational fields can enable matter to become quantum entangled — and that's even if the concept of quantum gravity does not exist. The idea comes from two London-based physicists who are challenging the way we think about quantum fields and how classical gravity operates.

The search for quantum gravity is the next big step in physics, as researchers seek to unify the physics of the very small with that of the very large. Quantum mechanics explains the former while general relativity theory — which famously describes how gravity works — explains the latter. Both quantum physics and the theory of general relativity were products of the first quarter of the 20th century, but 100 years later, scientists are still none the wiser as to how the two can be unified. As it stands, the theories contradict one another.

In fact, new findings from Joseph Aziz and Richard Howl of Royal Holloway, University of London, could certainly complicate matters. Their work builds on the back of a thought experiment first proposed by famed physicist Richard Feynman in 1957, which would involve placing an object — say, an apple — into quantum superposition.

To understand superposition, think of the properties that make up a particle's quantum state, such as its position, momentum, charge or quantum spin. The value of each of these properties is probabilistic in nature, and this distribution of probabilities is described by a wave, with the peak of the wave representing the greatest probability. Superposition is shown when wave functions for different outcomes overlap each other.

Feynman's thought experiment would place the position of that hypothetical apple into superposition — in other words, it would exist simultaneously in two locations until it is observed. Once observed, its wave function collapses. A second apple would then be introduced in Feynman's experiment, and if the first apple in quantum superposition interacted gravitationally with the second object even though the first apple's superposition state collapsed, Feynman decreed that this would then be a sign of quantum gravity at work.

"When Feynman proposed this idea that you could, in principle, place a mass into superposition in two locations and then see if its gravitational field is also in quantum superposition, he believed that it would mean that gravity is quantum," Howl told Space.com.

Modern treatments of this thought experiment explain the coupling between the two objects as them becoming quantum entangled. This means the quantum properties of the objects become inextricably linked to each other to the point that a change to one will initiate a change in the other — no matter how far apart they are. Albert Einstein referred to quantum entanglement as "spooky action at a distance."

However, Aziz and Howl have now shown that the entanglement could take place even without quantum gravity.

A big contradiction

Einstein described gravity as being the curvature of spacetime (the four-dimensional unification of space and time). Yet, there's an issue when it comes to quantum physics.

In quantum physics, the fundamental forces are divided up into discrete packets of energy called quanta. For example, a quantum of the electromagnetic force is a photon. In a quantum description of gravity, the gravitational force must therefore also have its own quanta, and these have been called gravitons. Nobody has ever seen a graviton, however, because the chances of an individual graviton interacting with a detector are exceptionally low.

Furthermore, in quantum gravity, the entanglement of gravitational fields would be mediated by "virtual gravitons." These would not really exist, hence being described as "virtual," — but in the wacky world of quantum physics, particles that don't exist are allowed for very brief amounts of time.

Howl and Aziz showed that if gravity is not quantum, it can still become entangled with matter that itself can be described according to quantum field theory. The classical gravitational field interacts with the quantum field of the matter that makes up the two objects, and this quasi-entanglement is mediated by virtual particles. Basically, Aziz and Howl pictured virtual atoms.

"Generally it has been considered that for the gravitational interaction to entangle, you need the gravitational field to be quantum mechanical so that it can be in quantum superposition," said Howl. "What we've tried to argue is that you could think about the gravitational interaction as more general than just the mediation of the gravitational field, and there could be quantum processes associated with it, virtual matter processes, and in that case even if the gravitational field is classical the gravitational interaction could still potentially entangle matter."

Howl says his work with Aziz does not rule out quantum gravity, nor does it mean that quantum gravity would be impossible to distinguish from this quasi-entanglement. Their findings suggest that the effect of classical gravity entangling matter is much smaller than if gravity were quantum.

"If you see the effects at a strong scale then you know it's quantum gravity," said Howl.

These effects manifest as correlations between particles or objects. For example, imagine you had a particle with a quantum spin of 1/2 (described as "up") and another particle with a quantum spin of –1/2 (described as "down"), and these two particles were in a state of quantum entanglement with each other. A strong correlation means that if you know the spin of one of the particles is up, then you automatically know that the spin of the other particle is down without having to measure it.

On the other hand, in the classical gravity case, that correlation becomes much weaker. It's a matter of probabilities — measure the spin of the other particle in repeated experiments and it won't be down as often as it would be if quantum gravity was at work in the entanglement.

For now, Aziz and Howl's work, along with Feynman's original thought experiment, are mathematical treatises. Could the experiment be performed in real life?

"It's still an open question as to whether you could do it," said Howl. "There's nothing to say you can't do it in theory, and people are working on it in the U.K. and Austria and various other places as well, but you have to eliminate all decoherence [things that would cause the superposition to collapse] and it is an incredibly difficult challenge."

Even if gravity is quantum — and not everyone thinks it necessarily is, for example in 2023 Jonathan Oppenheim at University College London published a model that combined classical general relativity with quantum field theory — Aziz and Howl's findings potentially tell us something new about how classical gravity behaves.

Howl also predicts there will be pushback to the team's ideas. "I don't know if everyone is going to agree with us!" he said. However, he is optimistic that in the coming decades Feynman's experiment could finally be conducted and provide a real test into whether quantum gravity is real or not.

Aziz and Howl's work was published on Oct. 22 in the journal Nature.

In a first-of-its-kind experiment, scientists have recreated "cosmic fireballs" here on Earth in a particle accelerator.The experiment aimed to investigate the stability of jets of high-temperature gas or plasma blasted at Earth by feeding supermassive black hole-powered galactic engines called blazars. This could, in turn, solve the mystery of hidden magnetic fields and missing high-energy gamma-rays.

Scientists from the University of Oxford and the Science and Technology Facilities Council’s (STFC) Central Laser Facility (CLF) teamed up and turned to the Super Proton Synchrotron based at CERN’s HiRadMat (High-Radiation to Materials) facility to generate electron–positron pairs. They then blasted these matter-antimatter counterpart pairs through 3.3 feet (1 meter) of plasma, recreating conditions in the jets of feeding supermassive black holes known as blazars. This enabled them to simulate some of the universe's most extreme physics.

"These experiments demonstrate how laboratory astrophysics can test theories of the high-energy universe," Bob Bingham, team member and researcher at the University of Strathclyde, said in a statement. "By reproducing relativistic plasma conditions in the lab, we can measure processes that shape the evolution of cosmic jets and better understand the origin of magnetic fields in intergalactic space."

What the blazes?

Blazars are a subset of active galactic nuclei (AGN), central regions of galaxies that are dominated by ravenously feeding supermassive black holes with masses millions or even billions of times that of the sun. These cosmic titans are surrounded by swirling flattened clouds of gas and dust called accretion discs that glow brightly due to friction generated by the immense gravitational influence of the central black hole.

These accretion disks gradually drop matter into the maw of the black hole, but not all of the material surrounding black holes is consumed. Powerful magnetic fields channel some of the matter to the poles of the black hole, where it is accelerated to near light-speed and blasted out as twin collimated jets of plasma. Blazar is the name given to AFNs that point one of these jets of plasma right at Earth. These jets produce intense gamma-ray radiation, which can be detected here on Earth by ground-based telescopes. But something is missing.

When these gamma-rays blast through intergalactic space, they scatter off photons in the background light from stars, creating matter in the form of electrons and antimatter in the form of positrons. These matter-antimatter pairs should scatter from a cosmic fossil field of radiation that ubiquitously fills the cosmos, called the "cosmic microwave background" or "CMB," which is a leftover from an event that occurred shortly after the Big Bang.

This scattering should create lower-energy gamma-rays that could be picked up by space-based gamma-ray telescopes such as the Fermi spacecraft. However, thus far, such a detection of low-energy gamma-rays has eluded these instruments.

Help! Our gamma-rays are missing!

There are a few theories as to why low-energy gamma-rays may be "missing." One idea suggests that the electron-positron pairs are deflected by weak intergalactic magnetic fields and that this bounces low-energy gamma-rays out of our line of sight. Another suggestion is that these matter-antimatter pairs become unstable as they travel through the extremely sparse matter scattered between galaxies. This could result in small fluctuations in the current of these jets that generate magnetic fields that cause further instability. The net result would be the dissipation of the beam's energy. Another possibility is that there is a relic magnetic field that exists between galaxies which remains from the early universe and disturbs low-energy gamma-rays.

In testing these first two concepts, the team of scientists arrived at some very enlightening and surprising results. The team had expected the beam to spread out and become disrupted. However, what they actually observed was a beam that maintained its narrow shape with little disruption and an absence of disruption generating magnetic fields. The implications of this are that plasma beam instabilities are too weak to explain missing low-energy gamma-rays. This could then support the idea of a relic magnetic field existing in the intergalactic medium, the matter that drifts between galaxies.

The findings raise additional questions. In particular, as the early universe was extremely uniform, it is unknown how such a relic could have been seeded in the primordial cosmos. Answering this conundrum may involve searching for physics beyond the Standard Model, possibly using future facilities such as the Cherenkov Telescope Array Observatory (CTAO).

"It was a lot of fun to be part of an innovative experiment like this that adds a novel dimension to the frontier research being done at CERN – hopefully our striking result will arouse interest in the plasma astrophysics community to the possibilities for probing fundamental cosmic questions in a terrestrial high-energy physics laboratory," Subir Sarkar, team member and University of Oxford researcher, said.

The team's research was published on Monday (Nov.3) in the journal PNAS.

Imagine a particle so ghostly that over 100 trillion of them could pass through you every single second without you noticing anything at all. Spooky, right? Well, believe it or not, these particles, called "neutrinos," not only exist, but they are so abundant that they are the second most common particle in the universe (after photons, the particles that make up light).

So, you might not get visited by a phantom this Halloween, but you'll definitely encounter plenty of cosmic ghost neutrinos, yet you won't notice a single thing. In fact, you're encountering them right now.

The ethereal nature of neutrinos, understandably nicknamed "ghost particles," means that despite how common they are, and the fact we are being constantly pelted with trillions of them, scientists haven't been able to get a good handle on many of their characteristics. For instance, their masses are shrouded in mystery. That is troubling because the sheer abundance of neutrinos in the observable universe — , about 10 to the power 87 (or 10 followed by 86 zeroes) — means they must have played a key role in the development of the cosmos even though they rarely interact with other particles of matter.

For example, scientists theorize that neutrinos were vitally important in the process that led to matter vastly outweighing antimatter in the universe. Antimatter and matter should have been created in equal amounts by the Big Bang — shouldn't they be perfectly symmetrical because they're made of the same particle components, just with opposite charges? — it is perplexing how one came to rule over the other. And, because when matter and antimatter counterparts meet, they annihilate each other; if it weren't for the process that gave matter the upper hand, the universe may have been devoid of matter altogether.

Like the Scooby-Doo-gang approaching another haunted mansion or abandoned funfair, scientists are determined to get to the bottom of this cosmic ghost story. As you might imagine, even though neutrinos are created by a wealth of cosmic events like stars and supernovas and even nuclear reactors here on Earth, the fact that they are virtually massless, chargeless and traverse the cosmos at near the speed of light means detecting them is much harder than nabbing Mr. Carswell the corrupt bank manager or dastardly museum curator Mr. Wickles.

However, just like Fred, Velma, Daphne, Shaggy and Scooby always come together to remove another rubber fright mask and expose a spooky crook, selected scientists have gathered via 2025's Science Policy & Advocacy for Research Competition (SPARC) to solve the mystery of these cosmic phantoms. Lasting 10 weeks, the SPARC seminar series aims to equip scientists with essential skills in science policy and communication, helping them translate complex research into clear messages for nontechnical audiences.

And neutrinos really fit the bill.

"I've always been fascinated by how we extract information from reality — even when we can’t fully define what reality is," Karim Hassinin, a Ph.D. candidate at the University of Houston and SPARC participant, said in a statement. "Theory, at its core, is a kind of storytelling, and every model is just one way of seeing the world. Through this program, I hope to learn how to translate those complex layers of scientific reasoning into stories that anyone can understand — so people can see not just the data, but the wonder behind discovery."

Hassinin is behind a new way to think about neutrinos, developed as a result of teaching an undergraduate physics class and seeing that his students had different perspectives on these cosmic phantoms. He is bringing that new approach to SPARC and, through it, to a wider general audience.

"The technical details will always be there, but it’s essential to show people the purpose of science and how it shapes our world," Hassinin said. "Our daily lives depend on technology, and technology depends on science. Through SPARC, I’ve gained a new perspective on how vital it is to bridge the gap between complex research and public understanding — because science communication truly matters everywhere."

In terms of his research, Hassinin uses computer simulations to investigate how neutrinos work their ghostly magic as they pass through different types of materials.

"We tell the generator how many neutrinos we want to use, what type of neutrino, and what material we want the neutrino to interact with," Hassinin explained. "Without neutrino interactions, we don't know anything about neutrinos. We have to understand something deeply before we can understand how to apply it."

Meghna Bhattacharya, a Postdoctoral Research Associate at Fermi National Accelerator Laboratory (Fermilab), is another scientist hot on the trail of neutrinos, focusing on algorithms that could identify neutrinos ejected into the universe when massive stars reach the end of their lives and go supernova.

Bhattacharya's work is set to play a key role in helping to develop the Deep Underground Neutrino Experiment (DUNE), two neutrino detectors placed in an intense beam of trillions of neutrinos currently under development near Fermilab, Illinois, and a far detector at the Sanford Underground Research Facility (SURF), South Dakota.

"These tools are designed to be integrated into DUNE, contributing to major questions about the universe’s evolution while also advancing computational techniques in physics," Bhattacharya said. "The tools being developed to answer fundamental science questions often lead to broader real-world applications. For example, technologies like proton beams, originally used in particle physics, are now being used for cancer treatment."

For Bhattacharya, the appeal of SPARC is the opportunity to share the story of her research with a wider audience and to make this audience aware of its wider impact on society.

"Looking forward, I hope to grow as a communicator and advocate for science more effectively, not only to learn how to distill complex research into accessible narratives but also to pass down the excitement of my research," she concluded.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

A clever mathematical tool known as virtual particles unlocks the strange and mysterious inner workings of subatomic particles. What happens to these particles within atoms would stay unexplained without this tool. The calculations using virtual particles predict the bizarre behavior of subatomic particles with such uncanny accuracy that some scientists think "they must really exist."

Virtual particles are not real – it says so right in their name – but if you want to understand how real particles interact with each other, they are unavoidable. They are essential tools to describe three of the forces found in nature: electromagnetism, and the strong and weak nuclear forces.

Real particles are lumps of energy that can be "seen" or detected by appropriate instruments; this feature is what makes them observable, or real. Virtual particles, on the other hand, are a sophisticated mathematical tool and cannot be seen. Physicist Richard Feynman invented them to describe the interactions between real particles.

But many physicists are not convinced by this cut-and-dried distinction. Although researchers can't detect these virtual particles, as tools of calculation they predict many subtle effects that ultrasensitive experiments have confirmed to a mind-boggling 12 decimal places. That precision is like measuring the distance between the North and South poles to better than the width of a single hair.

This level of agreement between measurements and calculations makes virtual particles the most thoroughly vetted idea in science. It forces some physicists to ask: Can a mathematical tool become real?

A bookkeeping tool

Virtual particles are the tool that physicists use to calculate how forces work in the microscopic subatomic world. The forces are real because they can be measured.

But instead of trying to calculate the forces directly, physicists use a bookkeeping system where short-lived virtual particles carry the force. Not only do virtual particles make the calculations more manageable, they also resolve a long-standing problem in physics: How does a force act across empty space?

Virtual particles exploit the natural fuzziness of the subatomic world, where if these ephemeral particles live briefly enough, they can also briefly borrow their energy from empty space. The haziness of the energy balance hides this brief imbalance, which allows the virtual particles to influence the real world.

One big advantage of this tool is that the mathematical operations describing the forces between particles can be visualized as diagrams. They tend to look like stick-figure cartoons of particle pingpong played with virtual particles. The diagrams – dubbed Feynman diagrams – offer an excellent intuitive framework, but they also give virtual particles an aura of reality that is deceiving.

Amazingly, this virtual particle-based method for calculation produces some of the most precise predictions in all of science.

Reality check

All matter is made of basic building blocks called atoms. Atoms, in turn, are made of small positively charged particles called protons found at their core, surrounded by even smaller negatively charged particles called electrons.

As a professor of physics and astronomy at Mississippi State University, I perform experiments that often rely on the idea that the electrons and protons seen in our instruments interact by swapping virtual particles. My colleagues and I have recently measured the size of the proton very precisely, by bombarding hydrogen atoms with a beam of electrons. This measurement assumes that the electrons can "feel" the proton at the center of the hydrogen atom by exchanging virtual photons: particles of electromagnetic energy.

Physicists use virtual particles to calculate how two electrons repel each other, with exquisite precision. The forces involved are represented as the accumulated effect of the two electrons trading virtual photons.

When two metal plates are placed extremely close together in a vacuum, they attract each other: This is known as the Casimir effect. Physicists can accurately calculate the force that pulls the plates together using virtual particle mathematics. Whether the virtual particles are really there or not, the math predicts exactly what researchers observe in the real world.

Yet another mysterious prediction made using the virtual particle tool kit is so-called Hawking radiation. When virtual particle pairs pop into existence at the edge of black holes, sometimes the black hole’s gravity grabs one partner while the other escapes. This rift causes the black hole to slowly evaporate. Although Hawking radiation has not yet been directly observed, researchers have recently observed it indirectly.

Useful fiction

Let's circle back to the question: Can a mathematical tool become real? If you can perfectly predict everything about a force by imagining it is carried by virtual particles, do these particles qualify as real? Does their fictional status matter?

Physicists remain divided on these questions. Some prefer to "just shut up and calculate" – one of Feynman's famous quips. For now, virtual particles are our best way to describe how particles behave. But researchers are developing alternative methods that do not need them at all.

If successful, these approaches could make virtual particles vanish for good. Successful or not, the fact that alternatives exist at all suggests virtual particles might be useful fiction rather than physical truth. It also fits the pattern of previous revolutions in science – the example of ether comes to mind. Physicists invented ether as a medium through which light waves traveled. Experiments matched well with calculations using this tool, yet they could not actually detect it. Eventually, Einstein's theory of relativity showed it was unnecessary.

Virtual particles are a striking paradox of modern physics. They shouldn't exist, yet they are indispensable for calculating everything from the strength of magnets to the behavior of black holes. They represent a profound dilemma: Sometimes the best insights into reality come through carefully constructed illusion. In the end, confusion around virtual particles may be just the price of understanding fundamental forces.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Back in the 1930s, physicists were doing experiments involving what they called "beta decay." They observed that an element would suddenly spit out a fast-moving electron, and once it was done, it would be different — sometimes a different isotope of the same element, and sometimes a different element altogether.

So the question on everybody's mind was, exactly how did this decay process unfold?

Enrico Fermi had an answer: a new force of nature. We knew that the nucleus of an atom was a bundle of neutrons and protons. Fermi hypothesized that some new force could change a proton into a neutron, or vice versa, and, in the process, release an electron and a nearly massless particle called a neutrino.

It was just a guess. But he was right, and the weak nuclear force was born.

The weak force can do things that no other force can. For example, it can change one flavor of quark into another, which is how neutrons and protons can swap places.

It's also incredibly weak (hence the name). It has a coupling constant, which is a fancy way of describing rare interactions that can happen that are 100,000 times smaller than the electromagnetic force. And it has an incredibly short range. At around 10^-18 meters, it has the same strength as the electromagnetic force, but at just 10^-17 meters, it's over 10,000 times weaker already.

And that incredible weakness comes from another property of the weak force that is totally unlike the other forces, and it has to do with what carries the weak force. All the carriers of all the other forces are massless. But the carriers of the weak force, known as the W and Z bosons, are heavier than a proton.

This was such a big surprise in the 1940s and '50s that it demanded its own explanation. How in the world did the weak force end up with massive force carriers? The answer would come from theoretical physicist Peter Higgs. The whole reason for the existence of the Higgs boson is to explain why the weak force is the way it is, with the side benefit of creating mass for the other particles.

So the weak force doesn't play by the normal rules — and, in fact, it breaks one of the biggest rules of all.

All of the other forces of nature obey something called parity symmetry. If you run a physics experiment and compare it with the same experiment in the mirror, the results should come out the same.

All particles also have a property called helicity, which is their spin relative to their direction of motion. This helicity can be counterclockwise, which we call left-handed, and clockwise, which we call right-handed. All particles spontaneously appear with an even mix of left- and right-handedness. This ensures that their mirror-universe versions are the same, thus maintaining the symmetry of parity.

But neutrinos, which are tiny particles created only by the weak force, do something else. Neutrinos are only ever left-handed. There are no known right-handed neutrinos. If you look at a process involving the weak force in the mirror, you'll see right-handed neutrinos, which don't exist. This breaks the mirror symmetry, and the weak force is the only force to do it.

So the weak force — the force that nobody asked for — is the only force that can change particle flavors, the only force with massive force carriers, and the only force to violate parity symmetry.

And for all that, what do we get? What has the weak force ever done for us?

Well, if you want to fuse two hydrogen atoms together, you can't just do that, because they repel each other. So you need to do a little dance. You need to change one of the protons into a neutron so they can bind together. This creates a deuteron, which is just a fancy name for a proton and a neutron bound together. Those deuterons then go on to fuse to become helium, and energy is released.

And what converts a proton into a neutron? That's right: the weak nuclear force. So, in addition to changing particle flavors, using massive force carriers and making the universe left-handed, the weak nuclear force allows the sun to shine — not a bad trade-off for such a weird force.

Particle accelerators, also known as particle colliders or atom smashers, have been responsible for some of the most exciting physics findings over the past century, including the discovery of the elusive Higgs boson, the fundamental force-carrying particle of the Higgs field, which gives other particles their mass.

But how do particle colliders work?

As the name suggests, particle accelerators involve accelerating subatomic particles to incredibly high speeds and smashing them into tiny targets, usually atomic nuclei, to achieve a desired effect.

To get an idea of the scales at which particle accelerators work, consider one of the basic units used in their applications: the "barn." It's equal to a square just 10 femtometers — 10 quadrillionths of a meter — on each side. And yes, the term, coined in the 1940s by physicists at Purdue University in the heart of the Midwest, is meant to invoke such sayings as "That's as big as a barn" and "You couldn't hit the broad side of a barn."

However, the simplest and earliest accelerators were relatively straightforward devices. There was a source of electrons, and then you launched those electrons through a cavity filled with electric fields. The electrons hit something on the other side of the cavity. Done.

For a few decades, most people in the U.S. had such a particle collider in their home: a CRT television. CRT stands for "cathode ray tube," and cathode rays are an old name for electrons (before scientists realized that electrons are particles). The electrons accelerated and smashed into a phosphorescent screen that lit up for our viewing pleasure.

Naturally, these kinds of colliders have limits on the size of the cavity and the strength of the electric field you can put in that cavity. So the next step in the evolution of colliders was known as a linear collider. The largest one operating today is the SLAC National Accelerator Laboratory, a 2-mile-long (3.2 kilometers) device outside San Francisco.

The idea behind a linear collider is to repeat the basic operation of simpler colliders. Most importantly, electric fields can either push or pull on electric charges, depending on their direction. So, as a charged particle enters a chamber, the electric field pulls on it to accelerate it. Then, once it gets halfway through, the electric field switches into "push" mode, which continues the acceleration.

Next, the charge exits that cavity and enters another with the same setup — and then another, and then another, repeated as long as you can get away with it (or until funding runs out).

Small linear accelerators power a variety of applications around the world. Need an X-ray at the dentist? There's an accelerator that fires electrons at a piece of metal to generate those X-rays. Need a tumor removed? A proton accelerator makes a great device for targeting cancer cells without harming surrounding tissue. Need a new semiconductor? An ion implanter paints microscopic transistors to create circuits. Need new tires? An accelerator has cross-linked those polymers to make the plastics and synthetic rubber more durable.

But what if you could keep the charge accelerating for an infinite length? The easiest way to make a finite line infinite is to bend it into a circle. The charge can then keep looping around and around, without reaching a stopping point.

But one of the main challenges with this is a bottleneck from relativity. As the particle speeds up, it gains kinetic energy — and energy equals mass, so effectively, the particle gets heavier and heavier. This isn't so much from a pure acceleration standpoint; it's kind of easy to just keep pushing subatomic particles harder. Rather, to keep them moving in a circle, we need to employ magnetic fields. At a heavier mass, the magnetic field can't keep up, and the particle starts to drift and slam into the side of the circular chamber.

So the magnetic field has to stay synchronized with the increasing mass of the particle, ramping up in strength as the particle whips around. Thus, we call these kinds of accelerators synchrotrons.

The flagship synchrotron is the Large Hadron Collider (LHC), operated by CERN (the European Organization for Nuclear Research). It features a ring with a circumference of 16.8 miles (27 km) holding 36,000 tons of magnets and chilled to minus 459.58 degrees Fahrenheit (minus 273.1 degrees Celsius) — colder than outer space — and it can accelerate protons to 99.9997828% the speed of light.

The LHC works in both directions at once. Then, at the last minute — right when the two particle beams have reached their peak energy — they slam into each other head-on at a total energy of 14 tera electron volts.

That's less than a billionth of the energy of a thrown baseball. But considering all that energy is crammed into an incredibly tiny area, the energy densities reach conditions not seen in the universe since the earliest moments of the Big Bang. At those energies, short-lived particles appear from the vacuum, giving physicists a glimpse of the most basic operations of nature.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

We have developed a new way to secure video transmissions so even quantum computers in the future won't be able to break into private video livestreams or recordings. We are computer scientists who study computer security. Our research introduces quantum-safe video encryption, which combines two complementary techniques: quantum encryption and secure internet transmission.

With our encryption system, a hacker wouldn’t be able to access or understand the video data because it's scrambled using a quantum key that changes unpredictably. Cryptographic keys scramble data so that only someone with the correct key can unscramble it. If the hacker even tries to peek, the system detects it and raises an alarm. The video also travels in the digital equivalent of a locked box over the internet, so nobody can swap or tamper with it in transit.

Quantum encryption scrambles video data using truly random cryptographic keys based on quantum physics. Unlike traditional encryption that relies on mathematical complexity, quantum encryption uses the fundamental unpredictability of quantum states to generate unbreakable keys.

Quantum refers to the scale of atoms and molecules, which behave in counterintuitive ways. Quantum computers take advantage of these strange behaviors to solve problems that are difficult or impossible for ordinary computers.

We combine this quantum encryption scheme with secure transmission over the internet using transport layer security. This is the encryption scheme used to keep connections between web browsers and web pages private.

Our approach works by converting each video frame into a quantum image representation, essentially a mathematical framework that captures visual information in quantum states. We then scramble the data by combining it with quantum-generated random keys, making the encrypted video statistically indistinguishable from pure noise.

And because quantum encryption is resistant to future technology such as quantum computers, that video is safe for years to come.

Why it matters

Today's encryption works well, until tomorrow's quantum computers arrive. These super-powerful machines will be able to crack most current encryption methods in seconds. That means today’s private videos, stored on cloud platforms or transmitted over the internet, could be decrypted years from now.

More dangerously, these stolen videos can be manipulated into deepfakes: AI-generated videos that can make anyone appear to say or do anything. A forged video can ruin reputations, sway decisions and even incite violence. A secure encryption system not only protects privacy, it helps protect truth.

What other research is being done

Researchers around the world are exploring quantum key distribution to securely share encryption keys. Others use chaos theory, deep learning or hybrid algorithms to secure video and image content.

But most existing work focuses on images, or only on key exchange, without fully securing live or stored video data.

What's next

We're working toward scaling this system to encrypt full video files and real-time video streams, such as those used in video conferencing and surveillance systems.

Next steps include reducing the performance overhead for smoother playback and testing the system in real-world environments. We're also exploring how it can work alongside deepfake detection tools, so we not only stop hackers from accessing videos but also prove the videos haven’t been altered.

While our framework shows strong early results, practical use will depend on phased adoption as quantum systems become more accessible over the years.

The Research Brief is a short take on interesting academic work.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

This article was originally published at The Conversation. The publication contributed the article to Space.com's Expert Voices: Op-Ed & Insights.

Why didn’t the universe annihilate itself moments after the big bang? A new finding at Cern on the French-Swiss border brings us closer to answering this fundamental question about why matter dominates over its opposite – antimatter.

Much of what we see in everyday life is made up of matter. But antimatter exists in much smaller quantities. Matter and antimatter are almost direct opposites. Matter particles have an antimatter counterpart that has the same mass, but the opposite electric charge. For example, the matter proton particle is partnered by the antimatter antiproton, while the matter electron is partnered by the antimatter positron.

However, the symmetry in behavior between matter and antimatter is not perfect. In a paper published this week in Nature, the team working on an experiment at CERN, called LHCb, has reported that it has discovered differences in the rate at which matter particles called baryons decay relative to the rate of their antimatter counterparts. In particle physics, decay refers to the process where unstable subatomic particles transform into two or more lighter, more stable particles.

According to cosmological models, equal amounts of matter and antimatter were made in the big bang. If matter and antimatter particles come in contact, they annihilate one another, leaving behind pure energy. With this in mind, it’s a wonder that the universe doesn’t consist only of leftover energy from this annihilation process.

However, astronomical observations show that there is now a negligible amount of antimatter in the universe compared to the amount of matter. We therefore know that matter and antimatter must behave differently, such that the antimatter has disappeared while the matter has not.

Understanding what causes this difference in behavior between matter and antimatter is a key unanswered question. While there are differences between matter and antimatter in our best theory of fundamental quantum physics, the standard model, these differences are far too small to explain where all the antimatter has gone.

So we know there must be additional fundamental particles that we haven’t found yet, or effects beyond those described in the standard model. These would give rise to large enough differences in the behavior of matter and antimatter for our universe to exist in its current form.

Revealing new particles

Highly precise measurements of the differences between matter and antimatter are a key topic of research because they have the potential to be influenced by and reveal these new fundamental particles, helping us discover the physics that led to the universe we live in today.

Differences between matter and antimatter have previously been observed in the behaviour of another type of particle, mesons, which are made of a quark and an antiquark. There are also hints of differences in how the matter and antimatter versions of a further type of particle, the neutrino, behave as they travel.

The new measurement from LHCb has found differences between baryons and antibaryons, which are made of three quarks and three antiquarks respectively. Significantly, baryons make up most of the known matter in our universe, and this is the first time that we have observed differences between matter and antimatter in this group of particles.

The LHCb experiment at the Large Hadron Collider is designed to make highly precise measurements of differences in the behaviour of matter and antimatter. The experiment is operated by an international collaboration of scientists, made up of over 1,800 people based in 24 countries. In order to achieve the new result, the LHCb team studied over 80,000 baryons (“lambda-b” baryons, which are made up of a beauty quark, an up quark and a down quark) and their antimatter counterparts.

Crucially, we found that these baryons decay to specific subatomic particles (a proton, a kaon and two pions) slightly more frequently – 5% more often – than the rate at which the same process happens with antiparticles. While small, this difference is statistically significant enough to be the first observation of differences in behavior between baryon and antibaryon decays.

To date, all measurements of matter-antimatter differences have been consistent with the small level present in the standard model. While the new measurement from LHCb is also in line with this theory, it is a major step forward. We have now seen differences in the behavior of matter and antimatter in the group of particles that dominate the known matter of the universe. It’s a potential step in the direction of understanding why that situation came to be after the big bang.

With the current and forthcoming data runs of LHCb we will be able to study these differences forensically, and, we hope, tease out any sign of new fundamental particles that might be present.

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Physicists at CERN — home of the Large Hadron Collider — have for the first time made a qubit from antimatter, holding an antiproton in a state of quantum superposition for almost a minute.

This landmark achievement has been performed by scientists working as part of the BASE collaboration at CERN. BASE is the Baryon Antibaryon Symmetry Experiment, which is designed to measure the magnetic moment of antiprotons – in essence, how strongly they interact with magnetic fields.

However, while qubits are commonly associated with quantum computing, in this case the antiproton qubit will be used to test for differences between ordinary matter and antimatter. It will specifically help probe the question of why we live in a universe so dominated by ordinary matter when matter and antimatter should have been created in equal quantities during the Big Bang.

They're opposites of one another, right?

A proton and antiproton have the same mass but opposite charges, for example. In physics, the mirror-image properties between matter and antimatter is referred to as charge-parity-time (CPT) symmetry. CPT symmetry also says that a particle and its antiparticle should experience the laws of physics in the same way, meaning that they should feel gravity or electromagnetism with the same strength, for example (that first one has actually been tested, and indeed an antiprotons falls at the same rate as a proton).

So, theoretically, when the universe came into existence, there should have been a 50-50 chance of antimatter or regular matter particles being created. But for some reason, that didn't happen. It's very weird. Even the BASE project found that, to a precision of parts per billion, protons and antiprotons do have the same magnetic moment. Alas, more symmetry.

However, the BASE apparatus has enabled physicists to take things one step further.

Antiproton antics

When matter and antimatter come into contact, they annihilate one another in a burst of gamma-ray photons, so BASE has to keep them apart. To do so, it uses something called Penning traps, which can hold charged particles in position thanks to the careful deployment of electric and magnetic fields. BASE has two primary Penning traps. One is called the analysis trap, which measures the precession of the magnetic moment around a magnetic field, and the other is the precision trap, which is able to flip the quantum spin of a particle and measure that particle's oscillation in a magnetic field.

Quantum physics tells us that particles are born in a state of superposition. Take, for instance, the property of quantum spin, which is just one example of the weirdness of the quantum universe. Despite the name, spin does not describe the actual rotation of a particle; rather, it describes a property that mimics the rotation. How do we know that it isn't a real rotation? If it were, then the properties of quantum spin would mean particles would be spinning many times faster than the speed of light — which is impossible.

So, fundamental particles like electrons, protons and antiprotons have quantum spin values, even if they are not really spinning, and these values can be expressed either as a whole number or a fraction. The quantum spin of a proton and antiproton can be 1/2 or –1/2, and it is the quantum spin that generates the particle's magnetic moment.

Because of the magic of quantum superposition, which describes how all the possible quantum states exist synchronously in a particle's quantum wave-function, a proton or antiproton can have a spin of both 1/2 or –1/2 at the same time. That is, at least until they are measured and the quantum wave-function that describes the quantum state of the particle collapses onto one value. That's another bit of weirdness of the quantum world — particles have all possible properties at once until they are observed, like Schrödinger's cat being alive and dead at the same time in a box, until someone opens the box. In fact, any kind of interaction with the outside world causes the wave function to collapse in a process known as decoherence.

Why this happens is a subject of great debate between the various interpretations of quantum physics.

Regardless, by giving an antiproton that is held firmly in the precision trap just the right amount of energy, BASE scientists have been able to hold an antiproton in a state of superposition without decohering for about 50 seconds — a record for antimatter (this has previously been achieved with ordinary matter particles for much longer durations). In doing so, they formed a qubit out of the antiproton.

Keep the qubits away!

A qubit is a quantum version of a byte used in computer processing. A typical, binary byte can have a value of either 1 or 0. A qubit can be both 1 and 0 at the same time (or, have a spin of 1/2 and –1/2 at the same time), and a quantum computer using qubits could therefore, in principle, vastly accelerate information processing times.

However, the antiproton qubit is unlikely to find work in quantum computing because ordinary matter can be used for that more easily without the risk of the antimatter annihilating. Instead, the antiproton qubit could be used to further test for differences between matter and antimatter, and whether CPT symmetry is violated at any stage.

"This represents the first antimatter qubit and opens up the prospect of applying the entire set of coherent spectroscopy methods to single matter and antimatter systems in precision experiments," said BASE spokesperson Stefan Ulmer, of the RIKEN Advanced Science Institute in Japan, in a statement. "Most importantly, it will help BASE to perform antiproton moment measurements in future experiments with 10- to 100-fold improved precision."

Currently, BASE's experiments have to take place at CERN, where the antimatter is created in the Large Hadron Collider. However, the next phase of antimatter research will be BASE-STEP (Symmetry Tests in Experiments with Portable Antiprotons), which is a device that contains a portable Penning trap, allowing researchers to move antiprotons securely away from CERN to laboratories with quieter, purpose-built facilities that can reduce exterior magnetic field fluctuations that might interfere with magnetic moment experiments.

"Once it is fully operational, our new offline precision Penning trap system, which will be supplied with antiprotons transported by BASE-STEP, could allow us to achieve spin coherence times maybe even ten times longer than in current experiments, which will be a game-changer for baryonic antimatter research," said RIKEN's Barbara Latacz, who is the lead author of the new study.

The results are described in a paper that was published on July 23 in the journal Nature.

Earlier this year, an underwater detector in the Mediterranean Sea found the most energetic neutrino to date. And scientists are still talking about it because, well, this discovery could be a really big deal. Not only could this neutrino, also known as a "ghost particle," have been fleeing a gamma-ray burst or a supermassive black hole, but it could also have been produced by an ultra-powerful cosmic ray interacting with the cosmic microwave background (CMB).

That latter bit which we'll get to soon, could be huge. Moreover, the detector that pinpointed this particle isn't even totally built yet — once put together, who knows what it can accomplish. "We're excited to have observed this event and we're hungry and curious for more," KM3NeT's spokesperson, Paul de Jong of the University of Amsterdam, told Space.com

For some background, the neutrino was detected on February 13, 2023 by the European Union-funded KM3NeT, the Cubic Kilometre Neutrino Telescope. Neutrinos are ghostly particles because they have very little mass and rarely interact with other forms of matter, making them very difficult to detect. Trillions of neutrinos are passing through your body every second, yet you cannot tell. Scientists have to be patient to spot even one neutrino.

Modern neutrino detectors are placed in water, and particularly in the dark. Sometimes that water is held in a tank, as was the case with the Sudbury Neutrino Observatory in Canada, as well as with Super-Kamiokande in Japan. Other times, that water is frozen in the ground, as in the case of the IceCube Neutrino Observatory at the South Pole. But it's also possible for neutrino detectors to literally be dipped into the sea, as is the case with KM3NeT, which extends as deep as 2.17 miles (3.5 kilometers) below the waves.

The reason water is so important is that, occasionally, a neutrino will interact with a molecule of water. The energies involved can be so great that the collision smashes the water molecule apart into a bunch of daughter nuclei and particles, specifically muons. The muons travel quickly, almost as fast as light in a vacuum, and definitely faster than light through water — the refractive index of water slows light down to approximately 738,188,976 feet per second (225,000,000 meters per second) compared to 983,571,056 feet per second (299,792,458 meters per second) in a vacuum. Because the muons travel faster than light in water, they give off the equivalent of a sonic boom in the form of a flash of light. This light is called Cherenkov radiation.

KM3NeT consists of two detectors. The first, called ORCA, is 8,038 feet (2,450 meters) deep off the coast of France and is designed to study how neutrinos oscillate between different types of neutrinos. The other, aka the detector that spotted the new energetic neutrino — which has been catalogued as KM3-230213A — is called ARCA and is located off the coast of Sicily.

Both ARCA and ORCA are still under construction. When complete, ARCA will feature 230 vertical detection lines descending into the sea. Each will be lined with 18 optical modules containing 31 photomultiplier tubes that can spot flashes of Cherenkov radiation in the darkness at those depths. At the time that ARCA detected KM3-230213A, only 21 of its detection lines were in operation.

The muon ARCA detected had an energy of 120 PeV (1,000 trillion, or quadrillion, electronvolts), which implies the neutrino that produced it must have had a record-breaking energy of 220 PeV. This is 100 quadrillion times more energetic than visible-light photons, and 30 times more energetic than the neutrino that held the previous energy record.

Muons can travel several miles through the sea before being absorbed, and KM3NeT detected the muon traveling horizontally rather than straight down to the sea floor.

"The horizontal direction on the muon is very relevant," said de Jong.

Muons can also be formed in cosmic-ray spallation, wherein a cosmic ray enters Earth's atmosphere and collides with a molecule or atom, smashing it apart into a shower of subatomic particles. Muons formed in this manner can either reach the surface or enter the ocean while traveling straight down — not horizontally. To have been moving horizontally, the muon must have instead "been created close to the detector, and the only realistic scenario is that it was created by a high-energy neutrino," said de Jong.

A neutrino of 220 PeV is unprecedented. No environment or object known in our Milky Way galaxy could have produced a neutrino with so much energy. That means its origin must be extragalactic, perhaps created in the violence of a star exploding and producing a gamma-ray burst, or a supermassive black hole ripping a star or gas cloud to shreds with its titanic gravitational tidal forces. Because neutrinos are not deflected by magnetic fields or by gravity, their direction of travel leads back to their source.

"The muon direction is almost identical to the direction of the original neutrino, so we can play the game of pointing it back to its cosmic origin," said de Jong.

That origin is somewhere in the direction of the constellation of Orion, the Hunter. However, while there are numerous active galaxies with supermassive black holes in that region, none of them was displaying activity at the time that could explain the neutrino, nor was a gamma-ray burst detected from that direction at that time.

But another intriguing possibility is that KM3-230213A is the first "cosmogenic" neutrino to be discovered, produced when an ultra-high-energy cosmic ray smashes into a photon belonging to the cosmic microwave background, which is the residual light released 379,000 years after the Big Bang.

It would take an extremely energetic cosmic ray to be able to produce a neutrino like KM3-230213A. Cosmic rays in excess of 100,000 PeV have been detected by the likes of the Pierre Auger Observatory in Argentina. Their origins are uncertain, but, in theory every time such a cosmic ray encounters a CMB photon, the collision can produce neutrinos as energetic as KM3-230213A.

The greater the cosmic-ray energy, the greater its interaction cross-section, meaning it is more likely to interact with CMB photons. The constant interactions between cosmic rays and CMB photons slows the cosmic ray, limiting their kinetic energy. This is called the Greisen–Zatsepin–Kuzmin (GZK) limit.

The possibility of a cosmogenic neutrino excites de Jong. "It would be the very first observation of a cosmogenic neutrino, and it would be the first confirmation of the GZK cut-off outside charged cosmic rays — and even there the proof is ambiguous," he said.

Furthermore, the energy of cosmogenic neutrinos can reveal the properties of these ultra-high-energy cosmic rays. This parameter is key for discovering whether such phenomena are made of just protons or heavier atomic nuclei — and, therefore, what produces them. Although KM3-230213A was the only extremely high energy neutrino detected by KM3NeT, there will undoubtedly be many more passing through Earth that go undetected. Does KM3NeT's early detection with ARCA bode well for finally being able to detect such neutrinos more regularly?

"We certainly hope so!" said de Jong. "But realistically, other experiments such as IceCube have been taking data for longer and have not observed such an event, so we could simply have been lucky."

The discovery was described in a paper published on Feb. 12 in the journal Nature.

Everything in the universe is, quite literally, built upon particles, ranging from the fundamental particles that construct atoms that make up everything we see around us to the exotic ones that give rise to elusive phenomena like antimatter and dark matter. The former help us observe and manipulate our world while the latter help us understand it, hinting at profound mysteries surrounding the universe’s creation, evolution and structure.

When it comes to particle physics, however, much of the action takes place in giant accelerators smashing particles together at the speed of light. These accelerators are sometimes humanmade and therefore live on Earth — other times, they're of the cosmic sort and exist in deep space.

Indeed, over the past 12 months there has been a great deal of exciting particle action on Earth and in space — and we begin our round-up of 2024's particle physics stories with news that sounds more like science fiction.

The year we learned to move antimatter

No material is more volatile than antimatter, which is made of particles of equal mass but opposite charge to normal matter, so things like anti-protons and positrons, which are the antimatter version of electrons. Place a particle of antimatter with a particle of normal matter and they annihilate each other, instantly, in a burst of energy.

In science fiction, antimatter is typically written as an unrivaled power source, driving starships and detonating as bombs. In science fact, just being able to move antimatter without it coming into contact with normal matter and annihilating has proven to be a challenge, but scientists at CERN think they have now finally figured out a way to do that, and what's more, they're putting it to the test.

A report in Nature, published on Nov. 26, 2024, described how two teams of researchers are competing to be the first to move antimatter, hoping to initially transport antiprotons across CERN as a proof of concept before eventually taking the particles hundreds of miles away to a dedicated laboratory at the Heinrich Heine University in Dusseldorf, where its enigmatic properties can be examined more closely. To move the antimatter, the teams built containers that generate electromagnetic fields from superconducting magnets to hold the antimatter in place, and in a vacuum, without it touching anything.

Antimatter is both scarce and expensive to make, and it cannot simply be made on tap. While there is antimatter in space — as we shall see, it pays us a visit in cosmic rays — on Earth, scientists have only been able to produce about 20 billionths of a gram worth of antimatter. It would cost trillions to make just one gram. So, sharing around what few antimatter particles we can make at CERN's Large Hadron Collider (LHC) is the next best thing.

All in all, we might not be ready to build antimatter-powered spacecraft anytime soon, but transporting it will enable physicists to dig into antimatter's secrets, including why there is so little of it in the universe.

The year we broke the heaviest antimatter-particle record — twice!

Most antimatter particles created in particle accelerators have been fairly simple: anti-protons, positrons, anti-tritium and anti-helium — that sort of thing. However, in experiments at the Relativistic Heavy Ion Collider (RHIC) in New York and at the Large Hadron Collider, scientists have this year succeeded in creating "hyper" particles of antimatter.

The "hyper" is short for hyperon. Consider a particle such as a proton, which is made from three even smaller particles called quarks. A proton has two "up" quarks and one "down" quark (these names are just to differentiate between different types of quark; there's nothing really up or down about them). Conversely, a neutron is made from one up quark and two down quarks. By comparison, hyperons feature a kind of quark called a "strange" quark alongside the up and down ones. When hyperons are incorporated into regular atomic nuclei, those nuclei are made heavier than their regular counterparts. In addition, there are also antimatter versions.

Earlier this year, researchers were able to produce anti-hyperhydrogen-4, which contains an anti-proton, two anti-neutrons and an anti-hyperon, at RHIC. Then, a few months later, an even heavier antiparticle — anti-hyperhelium-4 that is made from two anti-protons, an anti-neutron and an anti-hyperon — was detected by the ALICE (A Large Ion Collider Experiment) instrument at the LHC. Anti-hyperhydrogen-4 and anti-hyperhelium-4 are the most massive anti-particles ever created in a laboratory.

Physicists found that the heavy particle collisions at RHIC and the LHC that formed these anti-hyperparticles created equal amounts of matter and antimatter. That might sound unsurprising — until we look around the universe and see a cosmos filled with normal matter and barely any antimatter. Why the universe made more matter than antimatter in the Big Bang is a mystery — if the two are perfectly symmetrical, then shouldn't there be an equal amount of both? Nonetheless, this asymmetry appears to be a good thing. If you recall, equal amounts of normal matter and antimatter would have completely annihilated one another, leaving the universe filled with nothing but photons of energy released by the annihilation.

That would mean there would be no stars, no planets, and no life.

By producing equal amounts of matter and antimatter, the experiments at RHIC and the LHC have simply deepened the mystery of the matter–antimatter asymmetry in the universe and why the Big Bang favored matter over antimatter. Still, we're slowly getting closer to the truth.

The year we connected antimatter to dark matter?

As we've already mentioned, antimatter isn't only generated in particle accelerators on Earth, but also comes from energetic processes in space that fling charged particles of matter and antimatter at us in the form of cosmic rays. These are particles moving at almost the speed of light and are thought to be produced by some of the most violent and magnetic objects in the universe: supernova remnants, active black holes and so forth.

Because of the observed asymmetry between matter and antimatter, most of these cosmic rays are made from matter, but some are formed of antimatter. The trouble is, we've been detecting more antimatter cosmic rays than we can easily explain.

On board the International Space Station is an experiment called the Alpha Magnetic Spectrometer, or AMS-02, which detects cosmic rays. AMS-02 has been detecting surprising amounts of antimatter in these cosmic rays, with significant abundances of anti-hydrogen-2, anti-helium-3 and anti-helium-4 having been detected by the AMS-02.

A new explanation proposed in 2024 is that these anti-particles are being produced by dark matter.

Nobody knows what dark matter is made from. All we know is that it is an invisible material that constitutes 85% of all the matter in the universe. The only way we know it is there is through its gravity.

Some models of dark matter predict that it could be made from a type of particle called a WIMP, or Weakly Interacting Massive Particle. Occasionally, a WIMP might interact with another WIMP, particularly near the Milky Way's heart, or the Galactic Center, where the density of dark matter is at its greatest. If that interaction takes place, the WIMPs could annihilate each other, producing a shower of other particles in the process — including antimatter.

The amount of anti-hydrogen-2 detected by the AMS-02 matches what models predict should result from WIMP annihilation. However, the observed abundances of anti-helium-3 and -4 in the cosmic rays are so great that they are much harder to explain. It may mean that our models that describe how WIMPs interact are wrong or incomplete, or possibly that WIMPs don’t exist at all – but then where is the antimatter coming from? As we come to the end of 2024, it is a puzzle that still hasn’t been solved.

The year crashing galaxy clusters revealed the motion of dark matter

One of the best places to measure possible dark matter interactions are galaxy clusters. A galaxy cluster contains vast amounts of dark matter, hot gas and assorted galaxies, all wrapped up in a gravitationally bound volume millions of light-years across. When two galaxy clusters collide, the clash is suitably titanic, and research from earlier this year gave us our most detailed look yet at such a collision.

During the collision, the galaxies mostly sailed through, the distances between them generally too great for there to be any crashes. The huge clouds of gas that fill each cluster, however, manage to smash together, emitting X-rays because they are so hot. Because the clouds of gas impede each other, they also don't travel very far in the collision.

In other words, we know where hot gas is coming from by detecting the X-rays, and we can see where the galaxies are just by looking. As for the dark matter, we can infer where it is by looking at how its gravity warps space, thereby creating gravitational lenses.

If dark matter does not interact at all, then it should exist alongside the galaxies in the collision having cleanly sailed through; if it interacts by a significant amount, we’d expect to see it closer to the hot gas. And if it interacts just a little bit, it would be around mid-way between the galaxies and the gas.

The problem is, we only see snapshots of these collisions between galaxy clusters. The collisions take place over hundreds of millions of years — so, we can't see the clusters moving, and we only see each collision from one angle that might not be the best angle. Discerning where the three components are in relation to each other in a collision is thus harder than it might seem.

Astronomers have witnessed many galaxy cluster collisions, the most famous being the Bullet Cluster. We saw the Bullet Cluster from a side-on vantage point, which makes it tricky to measure the motions of the components because we need to measure their Doppler shift, which requires a head-on alignment.

In 2024, that's what astronomers were able to do, with the galaxy cluster collision known as MACS J0018.5+1626, located 5 billion light-years away. Astronomers discovered that the dark matter had indeed decoupled from the hot colliding gas, and that it was moving at 10.8 million kilometers (6.7 million miles) per hour, which is about 1% of the speed of light. The findings suggest there’s not much interaction going on between the dark matter particles in the cluster and any other particle, although the measurements are not precise enough to tell whether there is a small amount of interaction or not.

This ambiguity still leaves the door open to many possibilities for the identity of dark matter.

The year we began waiting for a supernova to reveal the truth about dark matter

WIMPs have been the leading candidate for dark matter for years, but they're beginning to fall out of favor a little bit, since experiments have failed to detect them. A new competitor has risen to challenge WIMPs in the form of a hypothetical particle called the axion.

There's good reason to believe axions could be real. They're predicted by the theory of quantum chromodynamics, which concerns how the strong force binds quarks together to form protons and neutrons (and hyperons). It also just so happens that axions are a good candidate for dark matter. Yet, unfortunately nobody has ever detected an axion.

In 2024, scientists revealed a way that we could make that detection possible, but it requires a degree of luck and perfect timing.

According to the new research, the collapse of a massive star's core as it reaches the end of its life and turns into a neutron star during a supernova explosion could create axions aplenty in the first 10 seconds of that explosion. Unlike WIMPS, axions are not selective about how they interact, and a strong electromagnetic field, like the intense magnetic field of a massive dying star, could convert the axions into gamma-ray photons that we could then detect.

This is fine in principle, but challenging in reality, say the researchers. For one thing, the gamma rays would be relatively faint so we would need a supernova close to us, either in our Milky Way galaxy or in one of our satellite galaxies such as the Large Magellanic Cloud, to detect them. A supernova is predicted to explode in the Milky Way once every 50 years on average, but the last to be witnessed in the sky was in 1604 (although one was seen in 1987 in the Large Magellanic Cloud). All the other galactic supernovas since then have exploded either on the side of our galaxy we can't see, or close to our galaxy's central supermassive black hole where dust and gas shrouds the blast.

Maybe we're due one in the night sky, but the other trick is that we would have to be looking right at it for the first 10 seconds of the explosion to capture the gamma rays — and since we don’t know where it would explode and therefore where to point our telescopes, it leaves a lot to chance. The field of view of NASA's Fermi Gamma-ray Space Telescope gives it a one in 10 chance of looking in the right direction at the right time. To make sure we don't miss out, the researchers are proposing a new constellation of gamma-ray satellites, which they are calling the Galactic Axion Instrument for Supernova, or GALAXIS, which would cover the whole sky 24/7, waiting and watching.

If GALAXIS detected a gamma-ray signal, it would mean that dark matter is probably made of axions, and that would rule out our next dark-matter story from 2024.

The year we learned of a "Dark Big Bang"?

Understanding how dark matter was originally created could tell us more about what it is. A new theory, from Katherine Freese and Martin Winkler at the University of Texas at Austin, describes a "Dark Big Bang" that produced dark matter particles after the actual Big Bang that created our expanding universe. Freese and Winkler noted that, while we can infer the creation of normal matter in the Big Bang, evidence for dark matter only turns up via its gravitational effect. So what if it was formed later? This is where the Dark Big Bang comes in.

It's a somewhat overdramatic name, but describes how a cosmic energy field may have undergone quantum effects that brought about transitions within this field, and the energy difference between the transitions was converted into dark-matter particles. The key thing with the Dark Big Bang is that it predicts dark-matter particles that don’t interact at all (other than via gravity), which would rule out axions and WIMPs.

Building on this, two researchers at Colgate University in New York have shown that dark-matter particles that formed from a Dark Big Bang would create gravitational waves that would still be reverberating around the universe today. These gravitational waves could be detected by pulsar-timing arrays. This is the concept that gravitational waves passing between us and a pulsar could disrupt the timing of a pulsar’s radio pulses. The first pulsar-timing array, named NANOGrav (the North American Nanohertz Observatory for Gravitational Waves) recently found possible evidence for a cosmic background of gravitational waves, and researchers Richard Casey and Cosmin Ilie suggest these gravitational waves could have been produced by the Dark Big Bang, but there’s still a long way to go to confirm NANOGrav's findings.

The year we learned about neutrons' short lives

Neutrons and protons are the building blocks of the atoms that make everything around us. Protons can live forever, as far as we can tell (and if they do decay, then we’re looking at it happening in a colossal trillion trillion trillion years, or thereabouts).

On the other hand, while neutrons are perfectly stable when locked into atomic nuclei alongside protons, they don’t fair well on their own outside atomic nuclei. They last about 15 minutes before they decay.

It’s the ‘about’ that’s the problem. Physicists use two different techniques to measure the lifetime of a neutron, and while both techniques give a measurement of about 15 minutes, there’s a consistent 8 second difference between the two methods.

This difference has puzzled physicists because they could see no obvious reason for it, but in 2024 Austrian scientists developed an explanation. They suggested that free neutrons are not all at the same energy level when they are produced, and excited neutrons would take a slightly different amount of time to decay than neutrons at their lowest possible energy level. The different techniques for measuring the lifetime of neutrons would then give different answers because one favors neutrons in an excited state over those at their lowest energy level.

The year we watched radioactive decay in action

When radioactive atoms — otherwise known as radioisotopes — decay, they release particles that reduce their mass and make them stable. For instance, they can eject alpha particles, which are helium nuclei, or they can spit out electrons in a process called beta decay.

Scientists have known about alpha and beta decay for well over a century, but we've never actually seen the moment of decay, until the year 2024. A team of physicists in the United States devised an ingenious experiment that allowed them to watch the recoil imparted by an escaping alpha particle. How did they do it? First, they attached lead-212 nuclei to a piece of silica just a micron (a millionth of a meter) in size. They then levitated the silica using optical tweezers. Lead-212 has a half life of just over ten-and-half hours, which means that half of any given quantity of lead-212 will, on average, have decayed in that time. So if four lead-212 nuclei were placed on the silica, we'd expect to see two of the nuclei decay into more stable lead-208 every 10-and-a-half hours.

When the lead-212 did decay, the escaping alpha particle caused the isotope, and therefore the silica to which the lead nucleus was attached, to recoil. This recoil was detected by watching for a change in how light scattered off the silica, which allowed the physicists to identify the exact moment a nucleus decayed. In a way, the technique is a brand new type of particle detector, and could one day be used to measure more elusive decay products, such as neutrinos, or even dark matter.

The year we solved the W boson mystery to everyone's disappointment

This was one result scientists really didn’t want.

W bosons are carriers of the weak force, which controls the radioactive decay of alpha particles. The Standard Model of particle physics predicts that W bosons should have a mass of 80,357 ± 6 MeV, but previously researchers at Fermilab's tevatron particle accelerator in Illinois had measured the mass to be 80,433 ± 9 MeV — beyond the range of the Standard Model.

Was this a sign of new physics beyond the Standard Model?

A more massive W boson would fit in well with a theory called Supersymmetry, which posits that every particle has a much more massive "superparticle." If dark matter is made up of WIMPs, that would fit in nicely with Supersymmetry.

Alas, it wasn't to be. In 2024 the LHC's Compact Muon Solenoid instrument confirmed the mass of the W boson to be 80,360.2 ± 9.9 MeV, well within the range predicted by the Standard Model. This mass is equivalent to 1.25 x 10^–25 kilograms. How tiny!

Particle physicists thus went away disappointed that their dreams of breaking away from the Standard Model had come to nought, at least for now. It's not all bad news though; scientists can use the more precise mass of the W boson as a test of the strength of the Higgs field.

The year we said goodbye to Peter Higgs

On April 8, 2024, the British physicist Peter Higgs died at the age of 94. Higgs was famous for his work predicting the existence of the Higgs boson, which carried the Higgs field, and which was discovered by the Large Hadron Collider in 2012. The Higgs field is what gives all particles their mass as they move through the field — some particles can skip through it and are therefore light, like neutrinos or electrons, while for other particles it is like wading through treacle, and so they have more mass. Following the discovery, Higgs won the Nobel Prize for Physics in 2013.

Researchers in Birmingham have created the first image of a photon, a lemon-shaped particle of light emitted from the surface of a nanoparticle. The theory that made this image possible, reported Nov. 14 in the journal Physical Review Letters, enables scientists to calculate and understand various properties of these quantum particles — which could open up a range of new possibilities across fields such as quantum computing, photovoltaic devices and artificial photosynthesis.

Light's quantum behavior is well established, with over 100 years of experiments showing it can exist in both wave and particle form. But our fundamental understanding of this quantum nature is much further behind, and we only have a limited grasp of how photons are created and emitted, or of how they change through space and time.

"We want to be able to understand these processes to leverage that quantum side," first author Ben Yuen, a research fellow at the University of Birmingham in the U.K., told Live Science in an email. "How do light and matter really interact at this level?"

However, the very nature of light means the answer to this question has almost limitless possibilities. "We can think of a photon being a fundamental excitation of an electromagnetic field," explained Yuen. These fields are a continuum of different frequencies, each of which could potentially become excited. "You can split up a continuum into smaller parts and between any two points, there's still an infinite number of possible points you could pick," Yuen added.

The result is that the properties of a photon are heavily dependent on the properties of its environment, leading to some incredibly complex math. "At first glance, we would have to write down and solve an infinite number of equations to reach an answer," Yuen said.

Related: High school students who came up with 'impossible' proof of Pythagorean theorem discover 9 more solutions to the problem

To tackle this seemingly impossible task, Yuen and co-author Angela Demetriadou, professor of theoretical nanophotonics at the University of Birmingham, employed a clever math trick to dramatically simplify the equations.

Introducing imaginary numbers — multiples of the impossible square root of -1 — is a powerful tool when handling complex equations. Manipulating these imaginary components allows many of the difficult terms in the equation to cancel each other out. Provided all imaginary numbers are converted back to real numbers before reaching the solution, this leaves a much more manageable calculation.

"We transformed that continuum of real frequencies into a discrete set of complex frequencies," explained Yuen. "By doing that, we simplify the equations from a continuum into a discrete set which we can handle. We can put those into a computer and solve them."

The team used these new calculations to model the properties of a photon emitted from the surface of a nanoparticle, describing the interactions with the emitter and how the photon propagated away from the source. From these results, the team generated the first image of a photon, a lemon-shaped particle never seen before in physics.

Yuen stressed, however, that this is only the shape of a photon generated under these conditions. "The shape changes completely with the environment," he said. "This is really the point of nanophotonics, that by shaping the environment, we can really shape the photon itself."

The team's calculations provide a fundamental insight into the properties of this quantum particle — knowledge that Yuen believes will open up new lines of research for physicists, chemists and biologists alike.

"We could think about optoelectronic devices, photochemistry, light harvesting and photovoltaics, understanding photosynthesis, biosensors, and quantum communication," Yuen said. "And there will be a whole host of unknown applications. By doing this kind of really fundamental theory, you unlock new possibilities in other areas."

Energetic particles that pop briefly into existence when cosmic rays hit Earth’s atmosphere could help assess hidden damage to buildings in Ukraine after the war ends.

These particles — known as muons — are very strange. They are birthed from collisions between high-energy protons and atomic nuclei that make up cosmic rays, and molecules in Earth’s atmosphere. They exist for only about 2 microseconds before decaying into electrons and anti-neutrinos. But as they travel at the speed of light, they cover vast distances during their fleeting existence. Every second, about 10,000 muons rain on a square meter of Earth’s surface. In fact, these odd particles don’t only rain onto the surface, they penetrate into it, burrowing hundreds of feet into the ground. This ability of these particles to penetrate matter gave scientists in the 1940s the idea to use muon detectors to peer inside vast, otherwise impenetrable, structures. It took a long time before the technology could live up to the task.

In the 1970s, a pioneering experiment used muon detectors to search for hidden chambers in an Egyptian pyramid. It wasn’t until 50 years later that the technology began to come into its own. Over the past decade a handful of companies around the world have made progress developing portable muon tomography devices that can scan vehicles for hidden passengers or illegal goods, or look for cracks in highway bridges or aging nuclear reactors. Estonia-based company GScan is among the companies to have made strides with the development and has already deployed their detectors on several projects including assessing the state of the U.K.’s nuclear decommissioning site Sellafield. The company also has plans to take the technology to Ukraine to help evaluate hidden cracks and fractures in buildings and bridges that could cause the structures to collapse in the future.

"There is no other technology at the moment that can see inside a concrete block," Andi Hektor, GScan’s chief strategy officer and co-founder told Space.com. "The most powerful X-ray system could only see about 10 or 20 centimeters [4 to 8 inches] deep. But with muon detectors, we can see tens of meters deep."

Not only can muon detectors see inside impenetrable structures, they can also assess what’s inside them. For example, corroded metal rods stand out in front of those cosmic particle eyes and so do invisible cracks and hidden vaults filled with liquid.

Related: Scientists find highest energy cosmic ray electrons ever seen

How it works

As muons approach an object, a sensor made from a special kind of plastic fiber detects their passage. By stacking multiple layers of these fiber sheets, researchers are able to reconstruct the muons' trajectories as they pass through each sheet in different locations. Another detector on the other side of the concrete structure then measures how the path of the muons changed as the subatomic particles scattered from the irregularities inside the structure.

“We track hundreds of thousands or even millions of passing particles,” Hektor said. “Based on that information, we can compose an understanding of how the trajectory throughout the object changes on average. Based on that, we can make assumptions about the material and the state of the material that is inside the object.”

To properly assess a large, potentially dangerous structure, like a damaged bridge, is a long and laborious process. The detectors, Hektor said, scan a single key point of the structure for up to a week. To assess an average highway bridge can take up to a month and cost up to $125,000.

GScan are in talks with Ukrainian authorities to possibly test the technology on Kyiv’s Paton Bridge, a 70-year-old, 5,000-foot-long (1,543 meters) structure, which had already been considered seriously dilapidated before the beginning of the war.

"They obviously have different concerns now," Hektor said. "It's something that we could do when conditions are more suitable, and they begin rebuilding everything."

Better than X rays

Not only do muon detectors see much deeper than the better-known X-rays, they are also much safer. Naturally present in the environment, muons don't damage cells and DNA like even low doses of X-rays do. The detectors, unlike X-ray machines, therefore don’t increase the risk of cancer for their operators.

GScan have been developing their technology since 2016. Last year, they used the detectors to examine decommissioned nuclear reactors at the Paldiski nuclear submarine training center in Estonia, a 60-year-old complex built and managed by the Soviet Union. Analyzing the muon scattering, the researchers looked for pockets of radioactive waste and assessed the state of the reactors that have been buried in layers of concrete since the 1990s.

Primordial black holes (PBHs), which are thought to have formed right after the Big Bang, may be heating up and exploding throughout the universe.

These black hole explosions, powered by Hawking radiation — a quantum process where black holes generate particles from the vacuum due to their intense gravitational fields — could be detected by upcoming telescopes, physicists suggest in a new study. And, once spotted, these exotic explosions could reveal whether our universe contains previously undiscovered particles.

Black holes from the dawn of time

There's already plenty of evidence for the existence of black holes ranging from a few times the mass of the sun to billions of times the sun's mass. These black holes have been directly detected through the gravitational waves they emit during the mergers that help them grow. Some black holes, such as the Milky Way's Sagittarius A*, have even been directly imaged as "shadows" by the Event Horizon Telescope.

Related: Stephen Hawking's most famous prediction could mean that everything in the universe is doomed to evaporate, new study says

PBHs, first proposed by Yakov Zeldovich and Igor Novikov in 1967, are thought to have formed within the first fractions of a second after the Big Bang and may have been as small as subatomic particles, according to NASA. Unlike their larger counterparts, which form from the collapse of massive stars and galaxies, PBHs might have emerged from the collapse of ultradense regions in the extremely hot "primeval soup" of particles in the early universe.

If they exist, these compact objects could provide a natural explanation for dark matter, the invisible entity that makes up about 85% of the matter in the universe. However, PBHs remain elusive. Their theoretical existence is supported by a combination of cosmological models, but they have yet to be directly observed.

The Hawking radiation effect

One of the most interesting aspects of PBHs is their connection to Hawking radiation. According to quantum theory, black holes aren't completely "black"; they can emit radiation and slowly lose mass through a process first theorized by Stephen Hawking. This emission, known as Hawking radiation, occurs when virtual particle pairs pop in and out of the vacuum of space near a black hole's edge — its "event horizon." While these pairs normally annihilate each other, if one falls into the black hole, the other particle can escape as radiation. Over time, this leads to the black hole's gradual evaporation.

"For black holes with masses larger than a few times that of the Sun, Hawking radiation is nearly undetectable," Marco Calzà, a theoretical physicist at the University of Coimbra in Portugal and co-author of the study, told Live Science in an email. "But lighter black holes — such as PBHs — would be much hotter and emit far more radiation, potentially allowing us to detect this process. This radiation can include a variety of particles, from photons to electrons to neutrinos."

Related: Stephen Hawking's black hole radiation paradox could finally be solved — if black holes aren't what they seem

As the PBH evaporates, it loses mass, becoming hotter and emitting more radiation in a feedback loop. Eventually, the black hole should explode in a powerful burst of radiation — a process that existing gamma-ray and neutrino telescopes are actively searching for. Although no definitive PBH explosions have been detected yet, the new study suggests these rare events could be the key to unlocking new physics.

Probing the final moments of a PBH

In their recent study, published in the Journal of High Energy Physics, Calzà and study co-author João G. Rosa, also a theoretical physicist at the University of Coimbra, introduced innovative methods for studying PBHs during their final stages of evaporation. By analyzing the properties of their Hawking radiation, the duo developed tools to estimate a PBH's mass and spin.

"Tracking a PBH's mass and spin as it evaporates could provide valuable clues about its formation and evolution," Rosa told Live Science in an email.

Their work has significant implications for fundamental physics. In a previous study, Rosa, Calzà and collaborator John March-Russell of the University of Oxford explored how string theory — an attempt to unify the fundamental forces of nature within a single quantum theory — could affect an evaporating PBH. String theory predicts the existence of numerous low-mass particles called axions, which have no intrinsic spin. Their research suggested that axion emission could actually spin up a PBH, contrary to Hawking's predictions.

"A spinning PBH would provide compelling evidence for these exotic axions, potentially revolutionizing our understanding of particle physics," Calzà said.

Furthermore, the study suggests that analyzing the evolution of a PBH's mass and spin in its final moments could reveal the existence of other new particles. By tracking the spectrum of Hawking radiation, scientists might be able to distinguish between high-energy particle physics models. Neutrino telescopes, such as IceCube, could even help uncover these new particles as PBHs explode in space.

"If we can catch just one exploding PBH and measure its Hawking radiation, we could learn a tremendous amount about new particles and potentially guide the design of future particle accelerators," Rosa said.

Although no exploding PBH has been detected yet, the tools and methods developed by Calzà and Rosa's team could pave the way for future discoveries. The researchers emphasized that dedicated experiments may not be necessary, as several new gamma-ray and neutrino telescopes with unprecedented sensitivity are already in development.

"Upcoming telescopes could easily spot one if it explodes nearby. If we're lucky enough to detect an exploding PBH, it could change everything we know about the fundamental laws of nature," Rosa said.

The mass of the W boson particle has been found by the Large Hadron Collider to be exactly what the Standard Model of particle physics predicts it to be, contradicting earlier results from Fermilab that hinted at a different mass and, therefore, the potential for new physics.

While the discovery further cements the Standard Model as our best depiction of the particle world, scientists had been hoping that their model was actually wrong, and that the discrepancy in the mass of the W boson could point the way to new theories that might explain puzzles such as the identity of dark matter, which accounts for 85% of all the matter in the universe yet remains effectively invisible to us.

Bosons are fundamental particles that carry the forces of nature. The strong force that binds quarks together inside protons and neutrons is carried by a boson called the gluon, the electromagnetic force's boson is the photon, and the weak force, which is responsible for radioactive decay, has three bosons: W+, W– and the Z boson.

Measuring the masses of these particles is tricky, because they have an incredibly fleeting existence before they decay into other particles. So, with their best efforts, physicists first create the bosons by colliding beams of protons traveling at almost the speed of light inside a particle accelerator. For example, at the LHC, the protons collide with a total energy of 13 trillion electronvolts (eV). Upon collision, the protons are forced to smash apart into other particles, some of which are bosons (this is how the Higgs boson, which carries the Higgs field that pretty much gives everything its mass, was discovered at the Large Hadron Collider). The bosons themselves then also decay, and the best way to measure their mass is to combine the masses of all the particles that the decaying bosons produce.

Related: How the Large Hadron Collider's successor will hunt for the dark universe

Bosons decay into particles called leptons (or antileptons), which are electrons, muons or tau particles (a lepton is defined by a half-integer spin, so 1/2 or 3/2). The Z boson decays into two further particles called muons, which are relatively easy to measure. This is, in fact, why the Z boson's mass is well-known, with a value of 91,187.6 MeV and an error margin of ± 2.1 MeV (million eV).

The W+ and W– bosons, however, decay into a lepton (or antilepton) plus a neutrino, and that’s where the problem lies.

Neutrinos are very slight, elusive particles that can zip through detectors like ghosts. Trillions of neutrinos are even running through your body right now, but you can't tell. That's why it takes a cubic kilometer of ice laced with photomultiplier tubes at the IceCube Neutrino Observatory at the South Pole to detect them. The Large Hadron Collider can detect neutrinos as well, but it has only acquired this capability recently via two detectors, FASER (the Forward Search Experiment) and SND (Scattering and Neutrino Detector). The LHC announced its first neutrino detections in August 2023.

The Standard Model predicts that the mass of the W+ and W– bosons is 80,357 MeV, ± 6 MeV, based on a theory that combines the electromagnetic force with the weak force, called "electroweak theory." However, in 2022, physicists who re-analyzed old data from 2011 (produced by Fermilab's Tevatron particle accelerator in Illinois, USA) determined a W boson mass of 80,433 MeV, ± 9 MeV. This took the W boson mass out of the range of the Standard Model. If it was correct, then it implied new physics such as "supersymmetry" (which posits that every particle in the Standard Model has an additional, much more massive counterpart) and Quantum Loop Gravity (which describes how the fabric of the universe might be made of tiny quantum loops). As a result, the physics world became very excited by the possibilities.

Alas, it was not to be. 

In 2023, the LHC's ATLAS experiment measured the mass of the W boson as 80,360 MeV ± 16 MeV, which is indeed in line with the Standard Model — but given Fermilab's tantalizing findings, there was a concern that ATLAS had some unrecognized systematic error affecting its measurements.

However, new measurements of the W boson's mass have been made by the LHC's Compact Muon Solenoid (CMS) experiment, and are also consistent with the Standard Model, producing a mass of 80,360.2 ± 9.9 MeV. This corresponds to just 1.42 x 10^–25 kilograms.

"Basically, we used a 14,000-ton scale to measure the weight of a particle that has a mass of 1 x 10^–25kg, or about 80 times the mass of a proton," physicist Michalis Bachtis of the University of California, Los Angeles, said in a statement.

Many physicists had of course been hoping there would prove to be a discrepancy in the mass of the W boson, as this would have opened the door for new physics that would be required to explain that discrepancy mass. Taking supersymmetry as an example, this concept could point the way towards explaining dark matter. A leading candidate for dark matter right now is a type of particle called a WIMP, which stands for Weakly Interacting Massive Particle — and  a massive, weakly interacting particle would fit perfectly within the confines of supersymmetry. Alas, currently no supersymmetric partners to particles in the Standard Model have yet been found, and the theory of supersymmetry is far from proven.

"Everybody was hoping we would measure it away from the theory, igniting hopes for new physics," said Bachtis. "By confirming that the mass of the W boson is consistent with the theory, we have to search for new physics elsewhere, maybe by studying the Higgs boson with high precision as well."

Nevertheless, confirming the mass of the W boson does open the door to other things. For example, it's possible to use this mass measurement to better judge the strength of the Higgs field, or to better understand electroweak theory. These advancements are options because of the way the CMS measured the W boson mass: by calibrating the energy of the emitted muons with margin of error of just 0.01%, which is orders of magnitude more precise than what had once been thought possible.

"This new level of precision will allow us to tackle critical measurements, such as those involving the W, Z and Higgs boson, with enhanced accuracy," said Ph.D. student Elisabetta Manca, who has been working on this project with Bachtis for 8 years.

So, the Standard Model wins again — but with increasing cosmological mysteries such as dark matter, dark energy and even the Hubble tension, something in our understanding of physics is going to have to break at some point to light the way forward for the world of physics.

The findings are described on CERN's CMS website. 

The use of a special type of atom could make even the most advanced atomic clocks more precise, scientists believe.

If confirmed, this breakthrough that could lead to more accurate GPS systems and better atomic clocks for use in space travel — it could even lead to devices that can detect earthquakes and volcanic eruptions with a higher level of accuracy. And fascinatingly, one of the researchers behind the development has a familiar name, based on a fitting family legacy rooted in the cutting edge of atomic science: Eliot Bohr. He's Neils Bohr's great-grandson.

Related: Atomic clocks on Earth could reveal secrets about dark matter across the universe

Of all the units humanity uses for measurement, the most precisely defined is the second, a fundamental unit of time. Crucial to this and all types of time measurements throughout history are different kinds of oscillations. Just as grandfather clocks use oscillations of a pendulum to measure time, atomic clocks define a second as 9,192,631,770 microwave oscillations of a cesium atom as it absorbs microwave radiation of a specific frequency.

Many modern atomic clocks use oscillations of strontium atoms rather than cesium to measure time; the most precise of these is accurate to within 1/15,000,000,000 of a second. This means that, even if it had been running since the dawn of time around 13.8 billion years ago, the clock still wouldn't have lost or gained a full second. Yet, for the majority of atomic clocks, which are used to keep Universal Coordinated Time (UTC) from positions around the globe and make sure our cell phones, computers and GPS tech is synchronized, there is still some room for improvement. 

That's because the laser used to read the oscillations of atoms in atomic clocks heats up those atoms while doing so, causing them to escape the system. This can create some discrepancy, albeit incredibly slight. Still, researchers from the Niels Bohr Institute thinks they have found a way to eliminate the laser altogether, thus avoiding atomic heating and potential degradation of precision. It is an institute named for Eliot Bohr's great-grandfather, and one Bohr himself is affiliated with.

"We found that it is possible to read out the collective state of an atomic ensemble, as is required in atomic clocks and sensors, at an enhanced rate and with minimal heating using superradiance," lead researcher Eliot Bohr, who was a Ph.D. fellow at the institute, told Space.com. "There is a threshold for superradiance to occur for our chosen experimental geometry, and we can leverage this threshold in a clock sequence."

Atomic clocks could be cooler

In current atomic clocks, 300 million or so hot strontium atoms are spat into a magneto-optical trap located within a vacuum chamber. This trap is a ball of atoms cooled to temperatures near absolute zero, the theoretical temperature at which all atomic movement would cease. Because of these temperatures, the introduced atoms lie almost still. This makes it possible for two mirrors with light between them to register their oscillations.

"In traditional atomic clocks, the detection heats up the atoms, requiring atoms to be freshly loaded," Bohr said. "This loading takes a while and causes downtime in the atomic clock cycle, limiting precision."

The team's sort of "paused" atoms that have been cooled so immensely, however,  can be reused. This means they wouldn't need to be replaced as often, therefore leading to more precise atomic clocks. 

Bohr explained that superradiant atoms are atoms that exist in a collective quantum state and are excited by the addition of energy in the form of photons, or particles of light. When the atoms release the photon-induced energy, or "decay," they all emit light in the same direction and at an enhanced rate.

"One cannot fundamentally distinguish which atom emitted which photon. They emitted them together, collectively," he added. "This enhanced emission rate allows for photons to be emitted much quicker from the type of atomic transitions that are used in atomic clocks."

This powerful light signal can be used to read out the atomic state of the collective strontium atoms, which means a laser isn't actually needed in the first place. And, again, because this process happens without the superradiant atoms being heated more than a very minimal amount, they won't need to be replaced.

Not only would doing away with the laser make more precise atomic clocks, but it could result in devices that are simpler and more portable. 

"State-of-the-art atomic clocks are now so precise they are sensitive to gravity," Bohr said. "There are proposals that if we have atomic clocks that are portable and precise enough, we can place them strategically and better predict earthquakes and volcano eruptions by measuring certain variations in gravity."

Revolutionary atomic science is the family trade

Coming from a line of scientists who have been influential in our understanding of the subatomic world, Bohr may well have this sort of research in his blood. Most famous in this lineage is his great-grandfather, Niels Bohr, one of the fathers of quantum physics and a scientist who made a huge contribution to the understanding of the atomic structure, without which research like this couldn't happen.

In 1913, Niels Bohr, along with Ernest Rutherford, presented a model of the atom, suggesting it to be a dense nucleus surrounded by orbiting electrons. Though this "Bohr model" of the atom is now considered relatively simplistic compared to the detailed diagrams we have now, 111 years after its inception, it is still used to introduce students to the concept of the atom in classrooms across the globe.

Eliot Bohr's family's connection to the atomic structure goes deeper than this, too. 

His grandfather is Aage Niels Bohr, who in 1975 was awarded the Nobel Prize in Physics along with Ben Roy Mottelson and James Rainwater for their discovery of the connection between collective motion and particle motion in atomic nuclei. This led to the development of an improved theory of the structure of the atomic nucleus.

"Both my great-grandfather and my grandfather inspired me greatly," Bohr said. "They both worked on theoretical work, understanding the atom and nucleus. My great-grandfather's theory that atoms can absorb a photon of a particular wavelength and go to an excited state, or emit a photon and decay to a lower state, is precisely what we do in our lab each and every day using lasers."

Bohr added that it is the open-mindedness demonstrated by his great-grandfather and colleagues that he finds particularly inspiring.

"The concepts are completely non-intuitive, but through rigorous data and debates, they accepted these new 'quantum' rules," Bohr said. "We now accept them and use them in many of our modern-day technologies. I hope to contribute to developing the next quantum technologies which will benefit society."

As for his superradient atomic clock research, Bohr said there are lots of possibilities for future advancements. The group he was part of in Copenhagen is now continuing to understand various properties of superradiant light to see how it can be harnessed for other situations.

Meanwhile, Bohr has started a postdoctoral research position at JILA, a joint institute between the National Institute of Standards and Technology (NIST) and the University of Colorado, Boulder. This is a lab that also studies superradiance and other collective atomic effects for next-generation quantum sensors.  

"I plan to continue researching collective quantum effects which can be used in clocks and sensors," he concluded. "We have some ideas for further refining the method, such as finding the optimal parameters and understanding and reducing the noise level in the superradiant signal. 

"There are a lot of possibilities to use superradiance to advance clocks and sensor technology."

The team's research was published in February in the journal Nature Communications.

On April 8, 2024, British theoretical physicist Peter Ware Higgs passed away at the age of 94. It was almost 12 years ago, on July 4, 2012, in a fairly inauspicious lecture hall located in Geneva, Switzerland, when Higgs became an iconic figure in modern science.

That was the day it was announced that collisions between particles at the Large Hadron Collider (LHC) facility — arguably the most ambitious and audacious science experiment ever — revealed the existence of the Higgs boson.

The discovery of the Higgs boson, named for Higgs himself, has been vital for the field of particle physics. It was the last occupant of the particle zoo that's needed to complete what's known as the "Standard Model of particle physics," the best description we have of the universe on the smallest of scales.

For Higgs, born in Newcastle upon Tyne in the U.K. to a Scottish mother and an English father on May 29, 1929, the moment was met with an outflow of emotion. This was unsurprising, given that this announcement represented the culmination of five decades of his work, and validated a theory that he refused to give up on.

Related: Higgs boson: The 'God Particle' explained

Beyond the culmination of the Standard Model, the discovery of the Higgs boson signaled the need for physicists to begin exploring physics beyond parameters they were used to, thus setting the course for physics for decades to come. 

"Peter Higgs' contribution to modern physics is absolutely outstanding," Luz Ángela García Peñaloza, a cosmologist at Universidad ECCI in Colombia told Space.com. "His work on quantum field theory led to a theory for which, later on, he would be awarded the Nobel Prize in Physics and explains the mechanism that provides fundamental particles with mass. 

"He was way ahead of his time."

50 years of searching for a single particle

The 20th century marked the birth of particle physics as a discipline of its own and sparked huge strides in the nascent field. Yet, as that century drew to a close and the particle zoo grew in terms of its occupants, physicists started to wonder why some particles had mass and others, particularly particles of light called "photons," didn't.

By 1964, physicists studying the weak nuclear force, which is one of four fundamental forces of nature that determines the atomic decay of elements by transforming protons to neutrons, concluded something surprising. 

The carriers of this force, W and Z bosons, should be massless — yet, the fact that the weak force appeared strong over short distances and weak over long distances meant they couldn't be massless. If they were, it would risk breaking an important rule of physics called symmetry, which ensures the laws of nature are the same however they are viewed. According to CERN, you can think of the symmetry problem as analogous to a pencil standing on its tip  —  a symmetrical system  —  suddenly tipping to point in a preferred direction, thus destroying its symmetry.

In 1964, Peter Higgs, François Englert and Robert Brout proposed a solution. There might be something, they said, that "tricks" nature into spontaneously breaking symmetry. So, what could that something be?

Higgs and colleagues thought that, when the universe was born, it might have been filled with what's called "the Higgs field" in a symmetrical, but unstable, state  like that precariously balanced pencil.

In just fractions of a second, that field, the "Higgs field," would find a stable configuration, but in doing so, would break its symmetry. This, in turn, gives rise to something called "the Brout-Englert-Higgs mechanism," which grants mass to the W and Z bosons and solves the discrepancy.

While this would have been a vital theory in its own right, it was later discovered the Higgs field would grant mass to many other fundamental particles, and that the strength of these interactions would give different particles different masses. This meant that, if confirmed, the theory would have major ramifications for science. 

The next step was getting that confirmation in the shape of the discovery of a particle that would act as a "messenger" for the Higgs field: The Higgs boson. 

This search would warrant the construction of the LHC. At 17 miles (27 kilometers) long, it is the largest particle accelerator ever built at a cost of around  $4.75 billion USD.

"Higgs' work is a major reason why the LHC was constructed in the first place," CERN experimental high energy physicist Nima Zardoshti told Space.com. "His predictions provided some of the crucial theoretical guidance as to the energy reach required by the LHC in order to potentially find new physics."

In 2012, that expense and ten years of effort by an international collaboration of 23 CERN member states paid off. 

A cascade of particles resulting from the decay of Higgs boson particles was created, and was captured by both the LHC ATLAS detector and the Compact Muon Solenoid (CMS) detector. This was the necessary confirmation for the Higgs field theory. 

Higgs and Englert would share the 2013 Nobel Prize in Physics for the breakthrough. 

"In professor Peter Higgs, physics has lost a gentle giant of the field," Suzie Sheehy, an associate professor of physics at the University of Melbourne and visiting lecturer at the University of Oxford, said in a press release. "Higgs’ work is rightly celebrated as an incredible feat of curiosity-driven research: his proposal in 1964 about the potential existence of the Higgs field and related particle, the Higgs boson, seemed at the time to be an obscure idea … just one of many theoretical mechanisms put forward to explain unknowns in fundamental physics.

"It then took almost 50 years — and around 13,000 other scientists and engineers — to build the experiments (ATLAS and CMS) that enabled the Higgs boson to be discovered in 2012 at the Large Hadron Collider."

Sheehy added that less well known is how curiosity-driven research has had enormous practical influence in our lives, producing unimaginable spin-offs like the World Wide Web and better cancer treatment technologies. 

"Higgs' story represents an important lesson for us all about how science works: he would have been the first person to point out that science does not happen on the timescales of a few years," Sheehy said. "We need to ensure long-term support for curiosity-driven research if we are to make the kinds of breakthroughs in our understanding of the universe that Peter Higgs is celebrated for. "

"Even though we have now discovered it, measuring with precision the properties of the Higgs boson still remains one of the most promising ways of probing physics beyond the Standard Model," Zardoshti added. "Higgs' work has and will continue to shape the field for many years to come and is possibly the largest success story of 21st-century theoretical physics."

As a science reporter, Higgs' legacy has personally touched my life as well.

On July 4, 2019, I was invited to visit the LHC during its shutdown and upgrades, see its ALICE detector up close and explore miles of tunnels under France and Switzerland where the collider is housed.

Before that, I, along with several other journalists, attended an orientation session at CERN in Geneva. Many of us realized that day marked exactly seven years since the announcement of the discovery of the Higgs boson, and we were sat in the very hall where Peter Higgs once shed tears as he heard confirmation his theory had reached fruition. I was able to quickly snap a very poor image of that hall. I made sure to take this image from the perspective of the very seats where Higgs sat, to see what he would have seen on that momentous day.

The moment gave me goosebumps. It still does. 

I'd written many times about how the discovery of the Higgs boson was vital to our understanding of physics, and I would go on to do so many more times.  Yet, in that lecture hall, I felt a connection with that moment, and I know many who have sat there since have felt that connection, too.

Imagine an unquantifiable field stretching across time and space to give metaphorical weight to a single, vital moment that changed everything — a field that can connect all who learn about that moment itself, to each other. 

I think Peter Higgs may have liked that idea.

Scientists have observed like charges attracting each other over long distances in an apparent contradiction of a fundamental principle of physics. 

First stated by French physicist Charles-Augustin de Coulomb in the 18th century, "opposites attract and like charges repel each other" has become a familiar idiom — even being famously reformulated by Paula Abdul. 

Now, new research published March 1 in the journal Nature Nanotechnology has complicated this picture. A team of researchers found that, in some liquids, the opposite is true: Like-charged particles attract.

Related: Scientists find 'ghost particles' spewing from our Milky Way galaxy in landmark discovery (video)

"Because like-charged objects in a vacuum are expected to repel regardless of whether the sign of the charge they carry is positive or negative, the expectation is that like-charged particles in solution must also monotonically repel," the researchers wrote in the paper.

To test the assumption, the researchers placed charged silica microparticles (measuring just 0.0002 inch, or 5 micrometers, wide — a fraction of the width of a human hair) inside water or one of two types of alcohol. By tracking the charges with a microscope, the team established that, inside water, the positively charged particles pushed themselves away from each other in accordance with Coulomb's law.

But the negatively charged particles behaved differently altogether: They clumped into tiny hexagonal structures. This effect occurred when the water was made mildly acidic — in a pH window between 5 and 6.5, or about as acidic as coffee or milk — and disappeared outside this range.

And when positively charged particles were placed inside ethanol or isopropanol, it had the opposite effect: The positive charges were attracted to each other, and the negative ones repelled.

To explain the strange behavior, the researchers turned to a theory they had been developed that modeled the water as molecular rather than as a continuous medium.

"Our [standard] equations are continuum equations — they don't respect the grainy nature of the continuum," lead author Madhavi Krishnan, a professor of physical chemistry at the University of Oxford, told Live Science. "It works perfectly fine for most situations, except when it doesn't."

By modeling the water molecules as tiny electromagnetic dipoles — with a slight negative charge at the oxygen atom and a positive charge around the hydrogen atoms — the researchers found that an "electrosolvation force" arises from the interaction between the negative oxygen and the negative silica particles.

This force reduces the overall energy in the system after a proton has "hopped" onto the silica particles to decrease their overall negative charge, and it occurs at a distinct pH range when the protons in the solution are able to switch their positions.

"You need to be in a range of pH where the protons want to hop on and off," Krishnan said.

In alcohol, the molecular dipole is inverted, leading the force to be felt between positive charges, the team found.

Now that the effect has been demonstrated, the researchers will use it to better understand biomolecular condensates, a type of cell organelle that can separate the phases of a cell's contents and whose workings are vital to understanding diseases.

"I'd be stunned if the basic underlying principle isn't similar," Krishnan said. "If we can contribute to understanding this class of problems, then I think we've added quite an important concept, because such phenomena are expected to be relevant even in human disease."

The past year was a big win for particle physics, as experiments and nature conspired to produce some truly stunning results. Here are the biggest stories about the smallest particles from 2023. 

1. Here comes the sun goddess

In 1992, astronomers were stunned to discover what they later named the Oh-My-God particle, a cosmic ray streaking into Earth's atmosphere with a blistering 320 exa-electron-volts (EeV) of energy. On a human scale, that's not a big number — roughly the energy of a dropped basketball hitting the ground. But for subatomic particles, it's gigantic, far outpacing even our most powerful collider experiments. And this past year, the OMG particle got a partner: a 240 EeV particle dubbed Amaterasu, named after the goddess of the sun in Japanese mythology. Discovered with the Telescope Array Project in Utah, the new particle joins a rarefied list of ultra-relativistic high-energy cosmic rays. These rare particles come from the most energetic events in the universe but are ultimately mysterious. For example, Amaterasu appeared to come from the direction of the Local Void, a big batch of nothing in our cosmological neighborhood.

Read more here: High-energy 'sun goddess' particle opens possibilities for new physics, exciting scientists

2. Who you gonna call? Ghost particles

Astronomers around the world are on the hunt for neutrinos.  These "ghost particles" are produced in all sorts of nuclear and high-energy reactions, but they hardly ever interact with normal matter. So, to catch neutrinos, astronomers have turned to massive observatories, like the IceCube Neutrino Observatory, which turns an entire cubic kilometer of the Antarctic ice sheet into a neutrino detector. Using that sensitive instrument, this year astronomers announced that our own Milky Way galaxy is producing neutrinos by the bucketful. While we've long known that other, more distant galaxies produce copious amounts of neutrinos, this was the first direct evidence that our galaxy does, too, thus opening up a brand-new pathway in neutrino science.

Read more here: Scientists find 'ghost particles' spewing from our Milky Way galaxy in landmark discovery (video)

3. Feel the beat

Pulsars are already known to be amazing objects. They're formed from neutron stars, which are the leftover cores of dead stars. They can compress several times the mass of the sun into a volume no bigger than a city. The fastest ones spin faster than your kitchen blender. Sometimes, they shoot out beams of radiation, and when those beams happen to wash over Earth, we call them pulsars. This year, astronomers added another superlative: the most energetic gamma-ray photons ever detected from a pulsar. Using the High Energy Stereoscopic System observatory in Namibia, the astronomers saw the photons coming from a pulsar located about 1,000 light-years away in the direction of the constellation Vela. A single photon at these energies is over 2 million times more powerful than the photons associated with a typical solar flare — so it's a good thing they were generated so far away. 

Read more here: Pulsar surprises astronomers with record-breaking gamma-rays

4. And now, the BOAT

Speaking of gamma-rays, pulsars aren't the only astronomical object capable of blasting them out. In fact, some explosions are so intense that they're known appropriately as gamma-ray bursts. In 2022, astronomers observed the brightest gamma-ray burst ever seen, which they dubbed the "BOAT," for  "brightest of all time." And in 2023, a different team of astronomers determined that the BOAT, which originated in a galaxy behind the Milky Way, was powerful enough to disturb the upper layer of Earth's atmosphere. The intense radiation affected the ionosphere, which sits between an altitude of 31 and 217 miles (between 50 and 350 kilometers). The effect wasn't very big, but the fact that there was any effect at all is surprising, the team said.

Read more here: Record-breaking 'BOAT' gamma-ray burst managed to disturb Earth's atmosphere

5. Antigravity doesn't exist

Antimatter is just like normal matter, except it has an opposite charge. For example, a positron has the same mass and spin as an electron, but has a positive charge rather than a negative one. First discovered in the early 20th century, antimatter is a major cornerstone of theoretical physics. But besides the charge, just how identical are antimatter and normal matter? This year, physicists determined that, yup, it all acts the same, especially in response to gravity. 

General relativity says that antimatter and matter should behave exactly the same, but no conclusive tests had been performed until this year. It's not exactly a surprising result, but it's good to check these kinds of things off the list. After all, nature has plenty of surprises for us, and you never know where you might find them.

Read more here: Antimatter responds to gravity like Einstein predicted, major CERN experiment confirms

6. The neutrino factory

Neutrinos come in all sorts of energies and from a variety of exotic sources. In 2023, astronomers learned of one more: giant black holes. The black holes themselves don't create neutrinos — after all, nothing can escape their gravitational clutches — but the gas swirling into their gaping maws certainly can. There, the plasma whips up to a healthy fraction of the speed of light and heats up to trillions of degrees. That's more than enough energy to produce all sorts of crazy particles, including neutrinos, which astronomers found constantly washing over Earth.

Read more here: These supermassive black hole jets may pelt Earth with 'ghost particles'

7. Dark matter mysteries

Most of the matter in the universe is a mysterious form of matter known as dark matter, which we can detect only indirectly via its gravitational influence on galaxies and the larger universe. There is no altered theory of gravity that can explain the results, so our current best guess is that dark matter is some sort of unknown particle. 

Scientists have been searching for signs of this particle with detectors scattered around the world, and this year, the Super Cryogenic Dark Matter Search collaboration announced … that they haven't found it. This isn't a bad thing; the team did provide tighter constraints on what dark matter isn't, which helps narrow down future searches — but the hunt continues.

Read more here: We still don't know what dark matter is, but here's what it's not

8. When darkness consumes the light

Dark matter is so mysterious that there may be whole new areas of physics that are currently invisible to us. For example, there could be a new, fifth force of nature that operates only among different kinds of dark matter particles. This force would need its own carrier, which has been dubbed the "dark photon," because that sounds really epic. This year, a team of physicists shed some light (pun intended) on how these dark photons might work and, more importantly, on how we might be able to detect them. Any theoretical insight here helps tremendously, as we need all the help we can get.

Read more here: Hypothetical 'dark photons' could shed light on mysterious dark matter

9. His dark(er) materials

The world of dark matter can get even weirder. Not satisfied with just one kind of particle? A new force of nature not enough? Well, how about an entire dark periodic table, with different "species" of dark matter particles interacting in their own elaborate, invisible dance? This leads to a deeply hypothetical idea known as dark atoms, where dark matter particles bundle up together in the hearts of galaxies. According to new research this year, these dark atoms can go on to influence the rate of star production in their host galaxies — a potentially observable effect. 

Read more here: Dark matter atoms may form shadowy galaxies with rapid star formation

10. Bubbletron mania

The early universe really knew how to throw a party. Within the first second after the Big Bang, the forces of nature split off from their united state, creating the cosmos that we know and love today. These "splittings" were violent and energetic, and they didn't happen all at once across the universe. As each force broke off, bubbles of the new reality formed, expanded and collided with each other. This year, physicists discovered that the colliding bubbles would make for excellent particle accelerators. Dubbed "bubbletrons," they just might be responsible for the creation of most of the particles we're familiar with.

Read more here: Giant 'bubbletrons' shaped the forces of the universe moments after the Big Bang
 

11. Runaway sun

The sun is our closest star, so it's also our nearest laboratory for stellar physics. This year, using the High-Altitude Water Cherenkov Observatory in Mexico, astronomers discovered that our star is far more energetic than we previously thought. The sun is perfectly capable of generating excess gamma-rays, the highest-energy form of radiation. While that radiation doesn't harm us directly, it does show that there's still a lot to learn about the sun.

Read more here: Sun blasts out highest-energy radiation ever recorded, raising questions for solar physics

1. The most powerful light from the sun

Among the new astronomical records set in 2023 was an announcement of the highest-energy gamma ray ever seen coming from the sun, an order of magnitude more powerful than had previously been seen.

"The sun is more surprising than we knew," Mehr Un Nisa, an astronomer at Michigan State University and one of the authors who described the discovery in Physical Review Letters, said in a statement.

Previously, NASA's Fermi Gamma-ray Space Telescope had detected gamma-rays coming from the sun with energies up to 200 gigaelectronvolt, or GeV (200 billion electronvolts). That's incredibly energetic, to say the least. These gamma-rays are produced when cosmic rays, which are particles from deep space moving at almost the speed of light, collide with the solar atmosphere. However, observations by the High-Altitude Cherenkov Observatory, or HAWC, in Mexico have officially trumped that. 

HAWC is able to detect gamma rays indirectly. When a gamma-ray photon enters Earth's atmosphere, it's bound to collide with an atmospheric molecule, smashing the molecule apart to form a shower of subatomic particles. These rain down on HAWC, which is a funny kind of telescope: it consists of 300 water tanks, each filled with 200 metric tons of water. The subatomic particles from the collision between a gamma ray and a molecule are moving so fast that when they enter water, they are actually moving faster than the speed of light through water (which is slightly slower than through a vacuum or through air). The subatomic particles produce a flash of light, a kind of visual equivalent of a sonic boom, called Cherenkov radiation.

The HAWC data revealed subatomic particles that had come from solar gamma rays with energies of about a trillion electronvolts (1 teraelectronvolt, or TeV), and a few that had energies up to nearly 10 TeV. 

"After looking at six years' worth of data, out popped this excess of gamma rays," said Nisa. "When we first saw it, we were like, 'we definitely messed this up, the sun cannot be this bright at these energies.'"

Although the exact mechanism is still unclear, cosmic rays are thought to be responsible for these gamma-rays too, penetrating 1,000 kilometers (620 miles) below the visible surface of the sun, where they interact with hidden magnetic fields. So, detecting these gamma rays might be able to tell us a bit about what’s happening below the roiling surface of the sun.

However, even though these gamma-rays are the most powerful ever seen coming from the sun, they are not the most powerful ever detected from the universe as a whole. That record goes to a gamma-ray detected in 2021 by China’s Large High Altitude Air Shower Observatory, which had an incredible energy of 1.4 quadrillion electronvolts (1.4 petaelectronvolts, PeV) and came from somewhere deep in the universe. 

Read more here: Sun blasts out highest-energy radiation ever recorded, raising questions for solar physics

2. Vela pulsar smashes gamma-ray energy record

More record-breaking gamma-rays were detected in 2023, with photons pushing 20 TeV detected coming from the pulsar within the Vela supernova remnant.

A pulsar is a spinning neutron star that consists of the remains of a massive star that once went boom in a supernova. Pulsars are normally detectable at radio wavelengths, but some of them also emit gamma-rays, thought to be produced by electrons spiraling around the phenomena's intense magnetic-field lines.

The gamma-ray emission from a pulsar can be illustrated as a spectrum of intensity versus energy. In most cases, these gamma-ray energies run up to a few hundred GeV, above which there is a cut-off. Occasionally, a pulsar will be seen to push through this cut-off — the pulsar in the Crab Nebula has been seen to emit gamma-rays that peak at 1 TeV. 

However, the Crab pulsar's peak has been utterly smashed by gamma rays detected coming from a pulsar in the Vela supernova remnant. The discovery was made by the High Energy Stereoscopic System (HESS) in Namibia. These gamma rays are way above the usual GeV cut-off, which implies that our understanding of how electrons are accelerated in strong magnetic fields is incomplete.

Read more here: Pulsar surprises astronomers with record-breaking gamma-rays 

3. The universe's biggest explosion

The most intense, long-lasting and powerful explosion ever seen — ten times brighter than any known supernova and still erupting even now — was discovered in a galaxy whose light has been traveling to us for 8 billion years, according to new research revealed in May in the Monthly Notices of the Royal Astronomical Society.

Cataloged as AT2021lwx, the explosive event was co-discovered by the Zwicky Transient Facility in California and the Asteroid Terrestrial-impact Last Alert System (ATLAS) in Hawaii, which looks for transient events in the sky that can be anything from a moving asteroid to a flaring cosmic explosion. 

"Once you know the distance to the object and how bright it appears to us, you can calculate the brightness of the object at its source," said Sebastian Hönig of the University of Southampton in the UK in a statement. "Once we’d performed those calculations, we realized this is extremely bright."

At its brightest, AT2021lwx shone with a luminosity two trillion times brighter than our sun. Astronomers suspect that AT2021lwx is not an exploding star, as such explosions fade after a few weeks or months, but rather a supermassive black hole consuming a huge cloud of gas — perhaps a cloud thousand times more massive than the sun itself. Astronomers call this a tidal disruption event; no such event on this scale has ever been witnessed before. The gas cloud is ripped apart by the vice-like gravitational tidal forces of the black hole, sending shockwaves reverberating through the tortured cloud and releasing huge amounts of energy.

"With new facilities, like the Vera Rubin Observatory's Legacy Survey of Space and Time, coming online in the next few years, we are hoping to discover more events like this and learn more about them," said Southampton's Philip Wiseman. "It could be that these events, although extremely rare, are so energetic that they are key processes to how the centers of galaxies change over time."

Read more here: Boom! Astronomers just watched the largest explosion in space rage for 3 years 

4. The most distant fast radio burst

The most distant fast radio burst (FRB) ever detected was revealed in 2023. 

A report in the Oct. 19 issue of the journal Science described how, on June 19, 2022, an FRB was spotted having traveled through space for a gargantuan 8 billion years.

FRBs are mysterious. They are short bursts of radio waves that last mere milliseconds, yet in that short fraction of time they can emit as much energy as our sun does in 30 years. Nobody knows what produces them; often, they are seen to go off randomly in the universe. Sometimes, they are even seen to repeat. Magnetars, which are extremely magnetic neutron stars, are the main suspect.

The record-breaking burst was detected by the Australian Square Kilometer Array Pathfinder (ASKAP), which is a group of 36 radio dishes. ASKAP pinpointed the location of the burst, cataloged as FRB 20220610A, which then allowed the Very Large Telescope in Chile to follow up and identify the source as a system of two or three colliding galaxies that we see as they were 8 billion years ago.

Because FRB 20220610A has had to travel through so much space to reach us, it encounters lots of rogue electrons that live in that intergalactic space. The electrons steal some of the radio waves' energy (depending on wavelength) which results in the radio signal becoming slightly dispersed. The more an FRB's signal is dispersed, the more electrons it has passed through. Therefore, the measure of dispersion could tell us about hidden stores of atomic matter that are otherwise undetectable.

"While we still don't know what causes these massive bursts of energy, the paper confirms that fast radio bursts are common events in the cosmos and that we will be able to use them to detect matter between galaxies and better understand the structure of the universe," Ryan Shannon of Swinburne University in Australia said in a statement.

Read more here: Record-breaking radio burst could help us find the universe's missing matter

5. Most distant detection of the 21cm line

The most distant detection of radio emissions associated with neutral hydrogen gas was achieved in 2023, with the discovery of radio waves from a galaxy that we see as it existed in the universe 8.8 billion years ago.

The 21cm line, or 21 centimeter line, is the most fundamental wavelength in the whole of radio astronomy. It's used to study the distribution of hydrogen gas in galaxies and throughout the cosmos at large. Radio telescopes routinely observe the 21cm line in our Milky Way galaxy and other galaxies in the modern universe. Galaxies in the distant universe are usually too faint, however, to be detected at this wavelength.

But one galaxy, cataloged as SDSSJ0826+5630 (the name means it was discovered as part of the Sloan Digital Sky Survey at Apache Point Observatory in New Mexico, the other numbers are its coordinates), has an advantage. Its light, including its radio emission, has been magnified by an intervening gravitational lens — a distortion in space caused by a massive object, in this case a large galaxy, lying in the foreground. 

"This effectively results in the magnification of the signal by a factor of 30, allowing the telescope to pick it up," Nirupam Roy of the Indian Institute of Science said in a statement.

The lensed 21cm radio signal was detected by the Giant Metrewave Radio Telescope in India. Astronomers, including Roy, were able to deduce the amount of gas in SDSSJ0826+5630 on the basis of the strength of the 21cm signal. They concluded that SDSSJ0826+5630 contains twice as much mass in the form of neutral hydrogen gas as it does in stars.

Read more here: Astronomers capture radio signal from ancient galaxy at record-breaking distance

6. Ingenuity takes to the air in record time

By virtue of being the only helicopter on Mars, NASA's Ingenuity chopper only has its own records to beat, but that it continues to beat them is a testament to the longevity of what was and still is a truly experimental mission.

On Sept. 16, Ingenuity performed its 59th flight, which became the longest flight of its mission up to that point, hovering over one spot for 142.59 seconds. It then matched this duration during flight 63 on Oct. 19, during which it also flew across land for 579 meters (1,901 feet), which is the third largest distance it had ever covered in one flight (the record for farthest flight being 704 meters/2,310 feet on April 19, 2022).

Since arriving on Mars along with the Perseverance rover in February 2021, Ingenuity has flown 67 flights as of Dec. 17. It's been in the Martian air for a total of 121.1 minutes, and has covered 15.3 kilometers (9.5 miles), reaching as high as 24 meters (78.7 feet) in the air.

Read more here: NASA's Ingenuity helicopter breaks altitude record on 59th Mars flight

7. NASA confirms the hottest summer on record

Not all records are welcome achievements. 

NASA's Goddard Institute of Space Studies (GISS) in New York confirmed that the Northern Hemisphere summer in 2023 experienced the warmest summer since its temperature records began in 1880, a consequence of human-caused global warming coupled with the effect of El Niño, which helped raise sea temperatures.

GISS scientists compare global temperatures by relating them to the average summer temperatures between 1950 and 1980. They found that June, July and August combined were on average 0.23 degrees Celsius (0.41 degrees Fahrenheit) warmer than the 1950–1980 average. August alone was 1.2 degrees Celsius (2.2 degrees Fahrenheit) warmer. This might not sound like much, but efforts to mitigate climate change rely on keeping global warming to less than 1.5 degrees Celsius above the pre-industrial average.

"Summer 2023's record-setting temperatures aren't just a set of numbers — they result in real-world consequences," NASA Administrator Bill Nelson said in a statement. These consequences included huge wildfires in Canada, Greece and Hawaii among other countries, and deadly heat waves across mainland Europe, Japan, South America and the United States.

"Unfortunately, climate change is happening," said climate scientist Gavin Schmidt, director of GISS. "Things that we said would come to pass are coming to pass, and it will get worse if we continue to emit carbon dioxide and other greenhouse gases into our atmosphere."

Read more here: NASA confirms summer 2023 was Earth's hottest on record

8. Antarctic sea ice hits record low

There was more depressing climate news in 2023, as a joint study by NASA and the National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder, found that the amount of sea ice in Antarctic waters reached a record low. Further, in the Arctic, things were not much better. Scientists found it exhibited  the sixth lowest amount of sea-ice measured since records began.

Sea-ice extent is defined as areas of the ocean where the ice-cover fraction is at least 15%.

Using satellite data to follow sea-ice across polar regions in both hemispheres, scientists discovered that Antarctic sea ice covered just 16.96 million square kilometers (6.5 million square miles) of the continent on Sept. 10, the lowest it's ever been. The previous low came in 1986, when sea-ice coverage was 1.03 square million kilometers (398,000 square miles) greater than the latest figure.

In the Arctic, there was even less sea ice (though not a record low), with frozen waters receding to just 4.23 million square kilometers (1.63 million square miles) on Sept. 19. This is 1.99 million square kilometers (770,000 square miles) less than the average during the period between 1981 and 2010.

"It's a record-smashing sea-ice low in the Antarctic," said Walt Meier of NSICD in a statement. "Sea-ice growth appears low around nearly the whole continent as opposed to any one region."

The loss of sea ice is the result of growing temperatures as a result of human-induced global warming, and it's a process that can rapidly spiral into a vicious cycle. Ice is effective at reflecting solar energy back into space, so the less ice there is, the less solar energy is reflected away. In turn, the planet warms. Plus, the less ice there is, the more sections of darker ocean are exposed, which can absorb solar energy more efficiently. This ultimately raises ocean temperatures, resulting in less sea ice — and so on.

Read more here: Antarctic sea ice hits record low, satellites reveal

9. Astronaut breaks NASA record for time spent in space

NASA astronaut Frank Rubio inadvertently made history in 2023 by becoming the first American to spend a full year in space on board the International Space Station (ISS). Rubio launched along with cosmonauts Sergey Prokopyev and Dmitri Petelin, joining Expedition 67. The trio were set to return to Earth after six months, but a coolant leak in their Soyuz capsule meant they had to stay on the ISS for more than a year. The trio finally returned to Earth, landing in Kazakhstan on 27 September 2023 after spending 371 days in space.

Rubio beat the previous records set by NASA astronaut Mark Vande Hei in 2021–2022 (355 days in space) and Scott Kelly in 2015–16 (340 days in space). However, Rubio is some way behind the global record holder — the late cosmonaut Valery Polyakov, who spent 437 days on the Russian Mir space station between 1994 and 1995.

Read more here: Astronaut Frank Rubio breaks US record on way to spending a year in space 

10. This white dwarf is an interstellar speed demon

The fastest runaway stars ever seen speeding through our galaxy were revealed in July by astronomers poring over data of stellar motions collected by the European Space Agency's Gaia satellite.

Six new hypervelocity stars were discovered, and two of them — cataloged as J0927-6335 and J1235-3752 — are the speediest ever seen, racing through space at 2,285 kilometers per second (5.1 million mph) and 1,694 kilometers per second (3.8 million mph) respectively. To put that into context, J0927-6335 could orbit around the Earth 694 times in an hour — aka not quite as fast as Christopher Reeves' Superman, but still pretty fast.

The stars are white dwarfs, which are the cores of sun-like stars that have stopped their intrinsic fusion reactions, puffed off their outer layers and expired. Astronomers suspect the white dwarfs once belonged in binary systems, where the white dwarf's companion star exploded in a cataclysmic supernova, giving the white dwarf an almighty kick.

"These stars are extraordinary because they are traveling much faster than normal stars in the Milky Way," Kareem El-Badry of the Harvard–Smithsonian Center for Astrophysics told Space.com. "Because they're faster than the galactic escape velocity, they'll soon be launched into intergalactic space."

Read more here: Record breaker! New fastest star zooms through Milky Way at 5 million mph

11. The most ancient supermassive black hole ever detected

It's fitting that, as the most expensive telescope ever built, the James Webb Space Telescope (JWST) is routinely breaking new astronomical records, with one of the standouts being the discovery of the most distant supermassive black hole known to exist in the universe.

The JWST spotted the black hole in a galaxy called CEERS 1019, which we see as it existed about 13.3 billion years ago (just 570 million years after the Big Bang). The mass of the black hole is about 9 million times the mass of the sun, or about twice as massive as the supermassive black hole at the center of our galaxy, the Milky Way.

CEERS stands for Cosmic Evolution Early Release Science, and represents a research program that aims to tap into the JWST's power and identify the most distant galaxies in the universe. Several other candidate black holes in even more distant galaxies are also being investigated by the CEERS team, but have yet to be verified. It's a mystery how these supermassive black holes formed and grew so quickly. The black holes are made visible because they are hungrily feeding from a bright disk of hot gas around them. 

In the case of CEERS 1019, the galaxy appears to be irregularly shaped, with three bright clumps, perhaps misshapen by a coming together between two or more galaxies that has resulted in large amounts of matter being sent towards the black hole.

"A galaxy merger could be partly responsible for fueling the activity in this galaxy's black hole, and that could also lead to increased star formation," said Jeyhan Kartaltepe of the Rochester Institute of Technology in a statement.

However, there has seemingly not been enough time for the black hole to have grown to 9 million solar masses if it indeed began life as a small, stellar-mass black hole. Instead, the black hole must have begun life as a large seed, scientists reason, perhaps itself tens of thousands of times the mass of our sun. This potential seed might've formed from the direct gravitational collapse of a huge cloud of gas. At the moment it is only a theory with some indirect evidence, but JWST's observations are bringing us closer to some answers.

Read more here: James Webb Space Telescope detects most distant active supermassive black hole ever seen 

12. Planet or failed star? The JWST finds the tiniest brown dwarf

Not every new astronomical record has to be about the biggest or the most distant. At the other end of the scale the JWST has discovered the smallest brown dwarf found so far, which at just three to four times the mass of Jupiter is the same size as some planets.

Astronomers using the JWST found the brown dwarf, along with other brown dwarfs holding less than eight times the mass of Jupiter, in the star cluster IC 348. IC 348 is found a thousand light years away in the Perseus Molecular Cloud. 

"One basic question you'll find in every astronomy textbook is, what are the smallest stars? That’s what we’re trying to answer," said Kevin Luhman of Penn State University in a statement. Luhman is lead author of a paper describing the brown-dwarf discovery published on Dec. 13 in The Astronomical Journal.

Brown dwarfs are often referred to a failed stars, because they form like stars by directly coalescing from a gaseous nebula, but their small size means they don't have enough mass to generate the temperatures required in their cores for the nuclear fusion of hydrogen — the telltale signature of a star. (Some brown dwarfs do manage fusion of deuterium for a short while, though.)

This particular record-breaking brown dwarf can't be a rogue planet that formed in a disk around a star before being ejected because it (and IC 348 itself) are only about five million years old. That's  not enough time for a gas giant planet to form around a star in the conventional way and then get ejected into deep space.

Read more here: James Webb Space Telescope spies record-breaking 'failed star' that shouldn't exist 

13. Tonga volcano sparked the most intense lightning storm ever seen

A new study in the summer of 2023 found that the explosive eruption of the Hunga Tonga-Hunga Ha'apai volcano on Jan. 15, 2022 produced a record number of lightning strikes in a supercharged thunderstorm that persisted for 11 hours across a huge region spanning 240 kilometers (150 miles) in width.

The volcano first became active in Dec. 2021, but it was the explosive eruption a month later that made headlines. It produced the most powerful atmospheric explosion ever recorded, made even more unusual because the source of the eruption, the volcano's caldera, is located 150 meters (500 feet) underwater. 

The eruption spewed out 5 billion kilograms of material per second, fueling a plume that climbed 58 kilometers (36 miles) high.

"There are theoretical limits for how high a plume can go and how fast the eruption rate can be, and the Hunga Tonga eruption just smashed them all,"Alexa Van Eaton of the US Geological Survey said in an interview with Space.com.

As the plume leveled out high above the ocean surface, it formed a huge, dome-shaped cloud. And, as overspilling plume material fell onto the cloud, it resulted in pressure waves that rippled out in concentric circles. It was in these ripples, filled with electrically charged crystals of ice from the underwater nature of the eruption and ionized volcanic ash, that the lightning was observed — 2,600 flashes per minute at its peak and totaling 192,000 flashes spread over 11 hours.

Summing up how extreme this new lightning record is, Van Eaton said "We've never seen anything like this sheer rate of lightning before, and at such high altitudes."

Read more here: Tonga undersea volcano created most intense lightning storm ever recorded

A new theory suggests that the unification between quantum physics and general relativity has eluded scientists for 100 years because huge "fluctuations" in space and time mean that gravity won't play by quantum rules.

Since the early 20th century, two revolutionary theories have defined our fundamental understanding of the physics that governs the universe. Quantum physics describes the physics of the small, at scales tinier than the atom, telling us how fundamental particles like electrons and photons interact and are governed. General relativity, on the other hand, describes the universe at tremendous scales, telling us how planets move around stars, how stars can die and collapse to birth black holes, and how galaxies cluster together to build the largest structures in the cosmos.

Since their development, these two theories have grown more robust and have bolstered science with their tremendous success. Quantum mechanics has shown that the quantum world is replete with counterintuitive aspects, like the existence of systems simultaneously in contradictory states or particles instantly influencing each other, even at opposite ends of the universe. General relativity, meanwhile, has revealed that the very fabric of space-time is shaped by the matter sitting upon it, and that violent interactions between bodies of great mass can create ripples in space-time known as gravitational waves that can travel for billions of light-years to wash over Earth.

Yet, there is a problem, a dark cloud that hangs over these disciplines: As these two pillars of physics are perfected, scientists are still unable to bridge the gulf between them.

Related: How dancing black holes get close enough to merge

"The two pillars of modern physics are inconsistent with each other, which means that there is a fundamental contradiction which lies in the very foundation of our laws of nature," University College London (UCL) Professor Jonathan Oppenheim told Space.com via email.

Oppenheim is the pioneer of a new and radical theory that could finally bring together these two concepts, a reconciliation that has defied the greatest scientific minds for over 100 years.

Why should gravity be 'quantum' at all? 

Previously, uniting general relativity with quantum physics has meant taking space-time  —  the three dimensions of space and the one dimension of time, unified as a single 4D entity that is at the foundation of general relativity  —  and breaking it down into discrete units, or "quanta." 

This requires space-time to be a passive stage on which the "action" of the universe plays out. However, general relativity hinges on space-time not being a static stage but rather a dynamic player in the universe's cosmic ballet, shaped by the presence of matter and energy and subsequently telling matter and energy how to move via the curvature and gravity that arises from it. 

Oppenheim's idea of "waving space-time" is based upon asking why gravity should have a quantum nature like that which has been discovered for the universe's other fundamental forces — electromagnetism, and the strong and weak nuclear forces. Gravity, he argues, isn't like these other forces. After all, it is the only one of the four that can define the very geometry of space-time, and the fields of quantum physics evolve upon this geometry. 

"We feel gravity because matter causes space-time to bend. Time flows at unequal rates at different locations," Oppenheim writes in a paper discussing his theory published in the journal Physical Review X. "The rate at which time flows and the causal structure [the fact that cause always precedes effect] it provides may be required to have a classical description in order for quantum theory to be well-formulated."

That means, according to his theory, termed a "postquantum theory of classical gravity," that space-time, and thus gravity, don't have quantum description. That's thanks to random fluctuations in space-time, which cause changes in the flow of time, thus breaking the concept of predictability.

"In both quantum gravity and classical gravity, space-time must be undergoing violent and random fluctuations all around us, but on a scale which we haven't yet been able to detect," Zach Weller-Davies, a researcher at the Perimeter Institute of Theoretical Physics in Canada and a former Ph.D. student of Oppenheim's, said in a statement.

 Related: What is the theory of general relativity? 

Betting on 'wavy space-time' vs. string theory and quantum loop gravity 

Of course, Oppenheim's idea is far from the first theory that has been proposed to heal the division between quantum physics and general relativity.

String theory is one of the most well-known concepts suggested to unite these two pillars of physics. In short, it views the particles that fill the universe as manifestations of one-dimensional vibrating objects called strings. String theory describes how these strings propagate through space and interact with each other, giving rise to a particle called a graviton that carries gravitational force and thus provides a quantum account of this fundamental force. 

A popular alternative unification theory to string theory is quantum loop gravity, which changes the formulation of general relativity to quantize space-time into chunks.

Quantum loop gravity supporter Carlo Rovelli and string theory proponent Geoff Penington doubt Oppenheim's postquantum theory of classical gravity. Their skepticism is the basis of a 5,000-to-1 odds bet with Oppenheim, which would be paid out upon the failure of an experiment devised by Weller-Davies and other former Ph.D. students of the UCL scientist to measure a mass very precisely to see if it appears to fluctuate over time  —  thus confirming the postquantum theory of classical gravity.

This skepticism is a two-way street for Oppenheim, as he doubts the validity of string theory and quantum loop gravity as accurate remedies to the quantum physics-general relativity problem. This is because these other ideas require extra ingredients to be added to the universe, including additional dimensions, that the postquantum theory of classical gravity doesn't need.

"It's unclear to me whether any of the current approaches consistently reconcile quantum theory and general relativity," Oppenheim said. "If string theory does manage to do so, it would require extra dimensions and supersymmetry, neither of which we have observed in nature, although it's still possible they are there."

He added that unitary theories, such as string theory and loop quantum gravity, also appear to require the breaking of Einstein's famous equivalence principle . This refers to the equity between two forms of mass — gravitational mass, experienced when standing on a body like Earth, and inertial mass, experienced in an accelerating frame of reference. Oppenheim explained that this equivalence breaking is needed to reconcile these theories with the "black hole information paradox," which asks where the information carried by matter swallowed by black holes goes. 

In addition to testing the fluctuation of a set mass due to the postquantum theory of classical gravity, Oppenheim and his former students are on the lookout for aspects of nature that may emerge and further support this novel theory. 

"We have shown that if space-time doesn't have a quantum nature, then there must be random fluctuations in the curvature of space-time which have a particular signature that can be verified experimentally," Zach Weller-Davies said. "If space-time is classical, the fluctuations have to be larger than a certain scale, and this scale can be determined by another experiment where we test how long we can put a heavy atom in superposition of being in two different locations."

Some of the universe's most energetic and mysterious light shows, long gamma-ray bursts, could be generated after dense dead stars collide to create infant black holes surrounded by a natal disk of gas and dust. 

This is the conclusion of a team of researchers who used computer simulations to show that when neutron stars  —  dense, extremely dead stars created when massive stars run out of nuclear fuel  —  collide and merge, a long gamma-ray burst can be launched alongside the event's jets and winds of energetic particles.

These results could help astronomers explain the existence of strange long gamma-ray bursts that can't be linked to the collapse of massive stars which, in addition to creating neutron stars, can also birth stellar-mass black holes.

"Our findings, which connect observations with underlying physics, have unified many unresolved mysteries in the field of gamma-ray bursts," Ore Gottlieb, lead author of the research and a scientist at the Center for Computational Astrophysics (CCA), said in a statement. "For the first time, we can look at gamma-ray burst observations and know what happened before the black hole formed."

Related: This gamma-ray space mystery may finally be solved with new black hole simulations

Solving a long gamma-ray burst puzzle 

Gamma-ray bursts were initially spotted in the late 1960s, and since then, they have presented scientists with an enduring puzzle as the exact mechanism that creates these bursts of high-energy light remains mysterious.

The picture is further complicated by the fact that there are two distinct populations of gamma-ray bursts: short-duration bursts lasting no more than a second and long-duration bursts, which can last longer than 10 seconds. 

Physicists initially linked short gamma-ray bursts to jets blasted out during neutron star mergers, which also generate flashes of light called kilonovas and create so-called "hyper-massive neutron stars" that themselves quickly collapse to birth black holes. On the other hand, long gamma-ray bursts were attributed to jets of matter launched in the collapse of massive rotating stars to birth either black holes or neutron stars.

Yet, in 2022, astronomers discovered two long gamma-ray bursts that didn't quite fir in with patterns of other radiation blasts of this type. These bursts thus couldn't be created in the collapse of a massive star, the scientists reasoned. This is what first led experts  to speculate that cosmic collisions could also create long gamma-ray bursts under certain circumstances. 

Gottlieb and colleagues have spent months running sophisticated simulations with the Flatiron Institute's supercomputers to see if such a hypothesis held true, and mergers could indeed spark long gamma-ray bursts. 

The simulations start with two compact objects closely orbiting one another,  then spiraling together, colliding and merging. Upon merging, the event launches jets of matter out at near-light speeds. The team then observed these jets in the simulation as they traveled far away from the merger site's epicenter.

Combining this model with data gathered in astronomical observations, Gottlieb and colleagues devised a unified model for gamma-ray bursts, showing that the strange long gamma-ray burst examples could be created in the aftermath of neutron star mergers. This would happen, they say, because the resultant body of a merger is surrounded by a rotating disk of leftover material that is magnetically charged. This ring of material could technically send out long gamma-ray bursts. 

Interestingly, the model could also help scientists determine what the system sending out those gamma-ray bursts looked like before the merger.

"If we see a long gamma-ray burst like the ones observed in 2022, we now know that it’s coming from a black hole with a massive disk," Gottlieb added. "And knowing there is a massive disk, we now can figure out the ratio of the masses of the two parental objects because their mass ratio is related to the properties of the disk. For example, the merger of unequal-mass neutron stars will inevitably produce a long-duration gamma-ray burst."

The model devised by the team isn't just applicable to long gamma-ray bursts either. It could be used to better understand the process behind the launch of short gamma-ray bursts. Gottlieband and the team’s model may be hinting that these shorter-duration blasts of high-energy radiation could originate from smaller disks of matter around black holes. 

Or, alternatively, short gamma-ray bursts could emerge from unstable hypermassive neutron stars before they rapidly collapse to birth black holes, the team says.Using the model in this way will require it to undergo refinement and needs more gamma-ray burst observational data, which could be forthcoming when the Vera C. Rubin Observatory starts observing in early 2025.

"As we get more observations of gamma-ray bursts at different pulse durations, we’ll be better able to probe the central engines powering these extreme events," Gottlieb concluded.

The research was published on Nov. 29 in the Astrophysical Journal Letters.

Over the years, scientists have managed to unveil the existence of quite a few intriguing particles, pushing the entire field of physics forward with each discovery. There's the "God Particle" for instance, aka the Higgs Boson that grants all other particles their masses. There's also the so-called "Oh My God!" particle, an unimaginably energetic cosmic ray. 

But now we have a new particle in town. It's named  the "sun goddess" particle  —  and is fittingly extraordinary. 

This particle has an energy level one million times greater than what can be generated in even humanity’s most powerful particle accelerators; it appears to have fallen to Earth in a shower of other, less energetic particles. Like the "Oh My God!" particle, these bits come from faraway regions of space and are known as cosmic rays. The particle has been dubbed "Amaterasu" after Amaterasu Ōmikami, the goddess of the sun and the universe in Japanese mythology, whose name means "shining in heaven."

And just as its mythological namesake is shrouded in mystery, so too is the Amaterasu particle. Its discoverers, including Osaka Metropolitan University researcher Toshihiro Fujii, don’t know where the particle came from or indeed what it is. They also still aren't sure what kind of violent and powerful process could have given rise to something as energetic as Amaterasu.

"This is the most energetic charged particle ever detected by the Telescope Array experiment," Fujii told Space.com.

The hope is that, just as Amaterasu is credited with the creation of Japan according to the Shinto tradition, the Amaterasu particle can help create an entirely new branch of high-energy astrophysics. 

Related: High-energy cosmic rays may originate within the Milky Way galaxy

The "Oh My Goddess!" particle

High-energy cosmic rays are extremely rare to begin with, but Fujii said the Amaterasu particle has an energy level not seen in a staggering 30 years of cosmic ray detections. 

In fact, when the researchers spotted Amaterasu with the Telescope Array experiment — involving 507 detectors spread across 270 square miles (699 square kilometers) of the high desert of Millard County, Utah —they initially thought the detection must be some kind of mistake.

"I thought it would be my mistake or bug, and then after checking the details of the event, I was excited to find it was not an error," Fujii said.

First spotted by the Telescope Array experiment on May 27, 2021, the Amaterasu particle exhibits an energy of 224 exa-electron volts (EeV). For contest, one EeV is equivalent to 10¹⁸ electron volts. This puts Amaterasu on a similar energy level to the most energetic cosmic ray ever discovered — yes, that's the "Oh My God!" particle, which was detected in Oct. 1991 by the Fly’s Eye camera in Dugway Proving Ground, Utah. The latter had an energy of 320 EeV.

"The Amaterasu particle should be an important messenger from the universe about extremely energetic phenomena, but we need to disentangle the origin of this mysterious particle," Fujii explained.

There isn’t an astrophysical object, or any cosmic event for that matter, in the direction from which the sun goddess particle appears to have come from. That's why scientists are pretty unclear on what led to its creation. But, while the origins of the Amaterasu particle may be currently unknown, Fujii does have some avenues of investigation to follow up on. Importantly, some of these ideas could extend beyond the Standard Model of particle physics, which is the best outline we have of the universe’s particle zoo and how each of those particles interact with one another. 

"One possibility is the particle has been accelerated by extremely energetic phenomena, such as a gamma-ray burst or a jet from a feeding supermassive black hole at the center of active galactic nuclei," Fujii said. "Another possibility is creation in an exotic scenario such as the decay of super heavy dark matter  —  a new particle, from unknown physics beyond the Standard Model."

The team has been hunting cosmic rays with the Telescope Array experiment in Utah since 2008, and will now continue to do so with a fourfold improved sensitivity of the newly upgraded project. They also expect other next-generation observatories to get in on the cosmic-ray action to help scientists embark on a more detailed investigation of the Amaterasu particle.

"I am personally excited to have found a new mystery in science to solve," Fujii concluded. 

The team’s research will be published on Nov. 24 in the journal Science. 

Blazars are feeding supermassive black holes that sit at the hearts of active galaxies, blasting out enormous jets of radiation and matter. But unlike quasars, the cosmic twin of a blazar, these phenomena are pointed directly at Earth. 

And according to new research, they could actually be pelting our planet with neutrinos — otherwise known as "ghost particles." 

This spooky moniker comes from the fact neutrinos are notoriously difficult to detect. They are chargeless, and have virtually no mass. Around 65 billion neutrinos manage to stream through every square inch of your body every single second with no discernible effect.

So unsurprisingly, neutrinos are considered the "ghosts" haunting the particle zoo. Fascinatingly, however, their ghost-like nature also makes them important probes of the universe. This is because neutrinos can "phase" through obstacles, such as dense dust clouds, that impede other forms of matter and even light. 

Therefore, understanding where exactly neutrinos are coming from in the cosmos is vital. And this new research brings scientists a step closer to establishing blazars as the source of the astrophysical ghosts. 

Related: 100 black hole jets aimed at Earth unleash controversial physics theory

Where gamma-rays come in

Blazars are a subset of bright, active galactic nuclei (AGNs) or "quasars," which are bright enough to outshine the combined light of every single star in the galaxy that houses them. Blazars are only different from standard quasars in that they keep our planet dead in their sights when  emitting material from their cores at near-light speeds.

The jets emitted in blazar flare events are composed of high-energy particles  known as cosmic rays   that can stretch across many light-years, even extending well beyond the limits of the galaxies these phenomena are situated within. These jets also consist of electromagnetic radiation ranging from low-energy radio waves to extremely high-energy gamma rays.

And importantly, when cosmic rays interact with particles of light , or photons ,  they are believed to create showers of none other than neutrinos. Thus, gamma-ray flares from AGNs have long-been the prime suspect in the hunt for neutrino particles detected in our sky.

The link between considerably less conspicuous AGN jets and neutrinos was solidified in 2017, when the IceCube neutrino detector buried deep under the North Pole spotted a high-energy neutrino event coinciding with the flare of a blazar called TXS 0506+056. They were connected in terms of location and timing. TXS 0506+056  emerges from a supermassive black hole powered AGN located around 5.7 billion light-years away from Earth.

Yet, the actual relationship between the blazar flare patterns and the amount of neutrinos passing through Earth  —  the neutrino flux  —  remained shrouded in mystery.

'On-duty' gamma-ray blasting blazars 

To solve this puzzle, an international team of researchers decided to deeply look at TXS 0506+056 as well as another 144 blazars, contenders gleaned from the Fermi Large Area Telescope Monitored Source List. 

This allowed the scientists to calculate the weekly flux of gamma-rays associated with blazars and simultaneously plot the light curves of such high-energy events. The researchers then developed a "flare duty cycle" that shows the amount of time a blazer spends in a flare state, and how much energy this flare state accounts for on blazer light curves. 

"We find that blazars with lower flare duty cycles and energy fractions are more numerous among our sample. Their flare duty cycles and energy fractions represent power law-like distributions [a relationship between two quantities, where a change in one quantity results in a change in the other that is proportional to a power of the change, independent of the initial size of both quantities] correlating strongly with each other,” Kenji Yoshida, team member and a researchers at the Shibaura Institute of Technology, said in a statement. "We found a significant difference between blazar subclasses for the flare duty cycles at the 5% significant level."

The team statistically assessed the neutrino flux from each gamma-ray flare and developed a scale relationship based on a blazar’s gamma-ray flux during more quiet periods. By comparing their neutrino predictions for each blazar for one-week and 10-year periods to the sensitivity of IceCube over time, the scientists were able to place upper limits on the contributions of the flares to neutrino flux. 

"We hope that this study helps improve our understanding of the contribution of blazars to astrophysical neutrinos," Yoshida concluded. "Application of the present method to further observations might have the potential to contribute to the advancement of scientific knowledge of the origin of astrophysical neutrinos."

The team’s research was published in September in the Astrophysical Journal. 

The most energetic particles in the universe appear to emerge from sources within the Milky Way, our home galaxy.

Cosmic rays are made of subatomic particles, such as protons and electrons, whose energies span a wide spectrum. Ultra-high-energy cosmic rays easily host tens of millions of times more energy than any particle accelerator can generate on Earth, but where they come from — and precisely what accelerates them to become some of the fastest in the universe — has intrigued scientists since the discovery of these phenomena in 1962.

In the past, astronomers had managed to provide some solid evidence that cosmic rays come from sources residing outside the Milky Way. But now, a new study suggests they also originate from within the galaxy, blasting out from the leftovers of exploded stars, otherwise known as supernova remnants. 

The new observations "open the tantalizing possibility that matter from a particular nearby supernova remnant can be measured at Earth," study co-author Gregory Guzik of the Louisiana State University said in a statement.

Related: Earthquakes seem more intense after cosmic ray strikes. Scientists say this is why

The latest results are thanks to a sensitive, dedicated telescope mounted outside the International Space Station (ISS), which since 2015 has been struck by over seven million ultra-high-energy cosmic ray particles. The instrument, the Calorimetric Electron Telescope (or CALET), was installed on the ISS with the hopes of being a more powerful cosmic ray detector than its flagship predecessor, the Alpha Magnetic Spectrometer.

Cosmic rays are known to rapidly lose energy once they exit their sources, so scientists say the recorded high-energy rays are convincing evidence that they originated from sources nearby our solar system.

But where exactly are they coming from? The team does not know for sure yet, but have some suspicions. 

It's possible, the researchers say, that the rays emerged from at least three of 12 supernova remnants scattered around our solar system within 3,000 light-years of us. One of them could be Vela, at a little over 800 light-years away. Vela is an 11,000-year-old, well-studied remnant of an exploded star, which shone 250 times brighter than Venus when it blasted and would have been visible as a bright flash in the sky even during the daytime. This remnant is also associated with the Vela pulsar — a rapidly rotating neutron star that broke records this year, when it released the highest-energy radiation ever seen coming from its kind.

The new findings are also "a strong indicator that the paradigm that we have for understanding these high-energy electrons — that they come from supernova remnants and that they are accelerated the way that we think they are — is correct," study lead author Nicholas Cannady, a scientist at the University of Maryland, Baltimore County, said in the statement. 

They "give insight into what's going on in these supernova remnants, and offer a way to understand the galaxy and these sources in the galaxy better," Cannady added.

The CALET telescope recorded its first event in October 2015. Among the seven million rays detected since then, the telescope was able to identify a range of cosmic ray energies,  all the way up to levels of 10 teravolts, with a few even beyond. This is a significant step up from previous works, which could only detect cosmic rays at about 4 teravolts, the scientists say.

"This is essentially what CALET was put up to do," Cannady said. "So it's exciting to be working on this and to finally be getting results that are pushing the bounds of what we've seen before."

The team plans to continue CALET measurements of cosmic ray sources until the ISS retires, which will likely be by the end of this decade.

This research is described in a paper published Thursday (Nov. 9) in the journal Physical Review Letters. 

Imagine going out to the deepest, emptiest place in the universe, achieving a perfect, total vacuum. Would you be surrounded by emptiness? The answer to that question is much subtler than you might realize.

The modern journey into the vacuum began in the 17th century, with a flashy experiment designed by Otto von Guericke, mayor of the town of Magdeburg in the Holy Roman Empire. As part of a political stunt to show that his city had rebounded after the ravages of the 30 Years' War, von Guericke put on a demonstration for the emperor and other notables to show off his newly invented vacuum pump. By placing two hemispheres together and pumping out all of the air, Otto showed that not even a team of horses could pull the hemispheres apart.

Contrary to millennia of thought in Europe following Aristotle's argument that "nature abhors a vacuum," von Guericke showed that the vacuum was possible.

In the decades following von Guericke's demonstration, philosophers and scientists wondered if the vast reaches of space were filled with some sort of material known as the ether, which would serve two purposes: One, it would still prevent a true vacuum from forming, and two, it would function as a medium for light waves to propagate through.

Related: Here's how the universe could end in a 'false vacuum decay'

However, in the late 1800s, two physicists in Cleveland, Albert Michelson and Edward Morley, devised a clever experiment to measure changes in the speed of light as Earth moved through the ether. No changes were detected — and soon, Einstein would demonstrate that the speed of light was always constant — so scientists eventually moved away from the concept of the ether, allowing for the possibility of a true vacuum.

Still, even far from Earth, there's plenty of stuff floating around: charged particles zipping here and there, wandering hydrogen atoms, bits of fluff and dust minding their own business. Even though the density of interstellar space is billions of times lower than even our emptiest human-made vacuum chambers, it's not 100% percent empty.

To reach the emptiest places in the universe, you have to travel to the cosmic voids, the vast regions of nothingness that dominate the volume of the cosmos. In the depths of the largest voids, you can stand hundreds of millions of light-years from the nearest galaxy. The cores of the voids are so empty that not even dark matter — the mysterious, invisible form of matter that makes up the bulk of every galaxy — doesn't even have a presence.

But still, space wouldn't really be empty. Suffusing the entire cosmos are lightweight, neutral particles called neutrinos as well as the radiation left over from the early days of the universe. This radiation, known as the cosmic microwave background (CMB), is responsible for over 99.99% of all the radiation in the universe, and it's impossible to escape. So, even in the darkest voids, you're not entirely lonely.

So let's say you were to build a giant box thick enough to block out the neutrinos and the CMB, leaving you alone inside. (Technically, the walls of the box would emit photons of their own, but let's leave that aside for this thought experiment.) Would you be alone then?

Quantum physics provides a surprising answer: No. Physicists have discovered that quantum fields soak all of space and time, and these quantum fields give rise to the particles of everyday life. But when left to their lonesome, the quantum fields have an intrinsic energy, known as vacuum energy. This energy is omnipresent throughout the universe. Even though you wouldn't have any particles around you, you'd still have this energy to be your sole companion.

So what if you concocted a device to nullify the vacuum energy (which is technically impossible, but let's keep going with the thought experiment)? Would you finally, truly be alone in the universe, surrounded by the perfect ideal of an all-encompassing nothingness?

The answer to that is … it depends. You'd still be an object in space, and some view space itself to have existence. We like to think of space as just a mathematical abstraction, a way for us to measure location and extent. But the concept of space began to take on a more concrete character with the work of René Descartes, the 17th-century genius who invented a mathematical foundation to describe space. If you've ever written down the x- and y-axes of a Cartesian grid, you have Descartes to thank for it.

Isaac Newton elevated the concept of space to serve as an absolute background for the motion of objects and the physical laws that govern their behavior. This is modern physics in a nutshell: Objects move and interact with each other on the background of space, which is assumed to exist.

Einstein took this one step further with general relativity, where space is promoted from a background stage to a starring actor — a dynamic, flexible entity that responds to the presence of matter and directs the motion of that matter. It is space itself, and especially its dynamics, that gives rise to the force of gravity.

So is space just a mathematical abstraction, a tool we use to describe the relationship between physical objects, or is it something more? Here's an interesting thought: What about gravitational waves? Gravitational waves do not require the presence of matter or energy to move; they simply exist as undulations in space-time itself. So if space is just a mathematical tool, then how can the waves exist on their own?

There is no firm answer to the question of whether true nothingness can exist. It could be that the concept of space is just a mathematical trick and does not exist in its own right. Or it could be that no matter where you go, you're always somewhere in space, so you'll always be surrounded by something.

Scientists recently fired up the world's smallest particle accelerator for the first time. The tiny technological triumph, which is around the size of a small coin, could open the door to a wide range of applications, including using the teensy particle accelerators inside human patients.

The new machine, known as a nanophotonic electron accelerator (NEA), consists of a small microchip that houses an even smaller vacuum tube made up of thousands of individual "pillars." Researchers can accelerate electrons by firing mini laser beams at these pillars.

The main acceleration tube is approximately 0.02 inches (0.5 millimeter) long, which is 54 million times shorter than the 16.8-mile-long (27 kilometers) ring that makes up CERN's Large Hadron Collider (LHC) in Switzerland — the world's largest and most powerful particle accelerator, which has discovered a range of new particles including the Higgs boson (or God particle), ghostly neutrinos, the charm meson and the mysterious X particle. 

The inside of the tiny tunnel is only around 225 nanometers wide. For context, human hairs are 80,000 to 100,000 nanometers thick, according to the National Nanotechnology Institute.

Related: Why a physicist wants to build a particle collider on the moon

In a new study, published Oct. 18 in the journal Nature, researchers from the Friedrich-Alexander University of Erlangen–Nuremberg (FAU) in Germany used the tiny contraption to accelerate electrons from an energy value of 28.4 kiloelectron volts to 40.7 keV, which is an increase of around 43%.

It is the first time that a nanophotonic electron accelerator, which was first proposed in 2015, has been successfully fired, the researchers wrote in a statement. (Researchers from Stanford University have already repeated the feat with their mini accelerator, but their results are still under review).

"For the first time, we really can speak about a particle accelerator on a [micro]chip," study co-author Roy Shiloh, a physicist at FAU, said in the statement.

The LHC uses more than 9,000 magnets to create a magnetic field that accelerates particles to around 99.9% of the speed of light. The NEA also creates a magnetic field, but it works by firing light beams at the pillars in the vacuum tube; this amplifies the energy in just the right way, but the resulting energy field is much weaker.

The electrons accelerated by the NEA only have around a millionth of the energy that particles accelerated by the LHC have. However, the researchers believe they can improve the NEA's design by using alternative materials or stacking multiple tubes next to one another, which could further accelerate the particles. Still, they will never reach anywhere near the same energy levels as the big colliders.

Related: Black holes could become massive particle accelerators

That may be no bad thing, given the main goal of creating these accelerators is to utilize the energy given off by the accelerated electrons in targeted medical treatments that can replace more damaging forms of radiotherapy, which is used to kill cancer cells.

"The dream application would be to place a particle accelerator on an endoscope in order to be able to administer radiotherapy directly at the affected area within the body," study lead author Tomáš Chlouba, a physicist at FAU, wrote in the statement. But this is still a long way off, he added.

A new crystal can bend light like a black hole would, causing the light to bow away from its usual straight path.

This phenomenon, called pseudogravity, could be used in 6G communication technology, according to the authors of the new study, published Sept. 28 in the journal Physical Review A. This next-generation communication would transmit information wirelessly at ultrahigh speeds. Because the crystal mimics what happens when light passes by black holes and other ultradense space objects, the new technique could also be used to study so-called quantum gravity, a theory that would unite quantum mechanics and Albert Einstein's theory of relativity.

According to relativity, light and other electromagnetic waves can be influenced by gravitational forces. This is called gravitational lensing, and astronomers use it all the time to study massive space objects such as quasars. Recreating such an effect in a laboratory environment is difficult, given the need for a huge amount of mass, but scientists have long suspected they could mimic the phenomenon using crystalline materials.

Related: Mysterious dark energy is spread evenly across the cosmos

To do so, Kyoko Kitamura, a professor in the graduate school of engineering at Tohoku University in Japan, and her colleagues started with photonic crystals, which are crystals of two or more arrangements that are arrayed in a regular, grid-like pattern and are capable of slowing light as it passes through them. The team gradually distorted these crystals, disrupting the crystalline lattice, and then shined beams of light through the crystals and watched them deflect.

"Much like gravity bends the trajectory of objects, we came up with a means to bend light within certain materials," Kitamura said in a statement.

Manipulating light in this way is one potential pathway for next-generation communications technology, which will require sending information in the terahertz range, or above 100 gigahertz. (5G technology maxes out at 71 gigahertz.) Researchers believe that creative manipulation of light is one way to reach these frequencies. The new material could also have applications in research.

"Academically, the findings show that photonic crystals could harness gravitational effects, opening new pathways within the field of graviton physics," study co-author Masayuki Fujita, an associate professor at Osaka University in Japan, said in the statement.

A graviton is the hypothetical quantum particle that mediates the force of gravity. No such particle has been observed yet, nor have scientists entirely worked out what this particle would even look like in theory.

We see countless stars and galaxies sparkling in the universe today, but how much matter is actually there? The question is simple enough — its answer, however, is turning out to be quite a head-scratcher. 

This dilemma exists largely because current cosmological observations simply disagree on how matter is distributed in the present-day universe.

Of some help could be a new computer simulation that traces how all elements of the universe — ordinary matter, dark matter and dark energy — evolve according to the laws of physics. The breathtaking visuals virtually show galaxies, and clusters of galaxies, manifesting in the universe, fed by the so-called cosmic web. This web is the largest structure in the universe, built with filaments made up of both normal matter, or baryonic matter, and dark matter. 

Unlike previous simulations that only considered dark matter, the new work, carried out by a project called FLAMINGO (short for Full-hydro Large-scale structure simulations with All-sky Mapping for the Interpretation of Next Generation Observations), tracks ordinary matter too.

Related: Do we live in a simulation? The problem with this mind-bending hypothesis.

"Although the dark matter dominates gravity, the contribution of ordinary matter can no longer be neglected," Joop Schaye, a professor at Leiden University in the Netherlands and a co-author of the three new studies on the FLAMINGO project, said in a statement.

As for how much matter the universe really contains, astronomers say computer simulations like this one are not just great cosmic eye candy but also important probes to help pin down the cause of a major discrepancy in cosmology called the "S8 tension." That's the debate over how matter in the cosmos is distributed.

What is the S8 tension? 

When investigating the universe, astronomers sometimes work with what's known as the S8 parameter. This parameter basically characterizes how "lumpy," or strongly clustered, all the matter in our universe is, and can be measured precisely with what are known as low-redshift observations. Astronomers use redshift to measure how far an object is from Earth, and low-redshift studies like "weak gravitational lensing surveys" can illuminate processes unfolding in the distant, and therefore older, universe. 

But S8's value can also be predicted using the standard model of cosmology; scientists can essentially tune the model to match known properties of the cosmic microwave background (CMB), which is the radiation leftover from the Big Bang, and calculate the lumpiness of matter from there. 

So, here's the thing. 

Those CMB experiments find a higher S8 value than the weak gravitational lensing surveys. And cosmologists don't know why — they call this discrepancy the S8 tension.

In fact, S8 tension is a brewing crisis in cosmology slightly different from its famous cousin: Hubble tension, which refers to the inconsistencies scientists face in pinning down the rate of expansion of the universe.

The reason it's a big deal that the team's new simulation doesn't offer an answer to S8 tension is, unlike previous simulations that only considered the effects of dark matter on an evolving universe, the latest work takes into account the effects of ordinary matter too. In contrast to dark matter, ordinary matter is governed by gravity as well as pressure from gas across the universe. For example, galactic winds driven by supernova explosions and actively accreting supermassive black holes are crucial processes that redistribute ordinary matter by blowing its particles out into intergalactic space.

However, even the new work's consideration of ordinary matter as well as some of the most extreme galactic winds was not sufficient to explain the weak clumping of matter observed in the present-day universe.

"Here I am at a loss," Schaye told Space.com. "An exciting possibility is that the tension is pointing to shortcomings in the standard model of cosmology, or even the standard model of physics."

Exotic physics or a flawed model?  

So, where did this S8 tension originate? 

"We don't know, which is what makes this so exciting," Ian McCarthy, a theoretical astrophysicist at Liverpool John Moores University in the U.K. and the co-author of three new studies, told Space.com.

Computer simulations, however, like those carried out by FLAMINGO could be bringing us a step closer. They may help reveal the cause of S8 tension because a grand, virtual map of the cosmos might assist with identifying possible errors in our current measurements. For example, astronomers are slowly ruling out more mundane explanations for the issue, such as the fact it could be due to general uncertainties in observations of large-scale structures or related to a problem with the CMB itself. 

In reality, the team speculates, perhaps the effects of normal matter are a lot stronger than in current simulations. That too seems unlikely though, as simulations agree very well with observed properties of galaxies and galaxy clusters.

"All of these possibilities are extremely exciting and have important implications for fundamental physics and cosmology," said McCarthy. The most exciting possibility, however, "is the Standard Model is incorrect in some way."

For example, dark matter could have exotic self-interacting properties not considered in the standard model — the S8 tension may be signaling a breakdown of our theory of gravity on the largest scales, McCarthy said.

Nonetheless, while the latest simulations track effects of normal matter and subatomic particles known as neutrinos — both of which are found to be important to make accurate predictions of how galaxies evolve across eons — they did not resolve the S8 tension.

Here's the ultimate head-scratcher: At low-redshifts, the universe is significantly less lumpy than predicted by the standard model. But measurements that probe structures of the universe between the CMB and low-redshift measurements are "fully consistent with standard model predictions," McCarthy said. "It seems the universe behaved as expected for a significant fraction of cosmic history, but that something changed later on in cosmic history."

Maybe the key to resolving the S8 tension lies in the answer to what, exactly, drove that change.

This research is described in three papers published in the journal Monthly Notices of the Royal Astronomical Society.

A group of three researchers earned the 2023 Nobel Prize in physics for work that has revolutionized how scientists study the electron – by illuminating molecules with attosecond-long flashes of light. But how long is an attosecond, and what can these infinitesimally short pulses tell researchers about the nature of matter?

I first learned of this area of research as a graduate student in physical chemistry. My doctoral adviser’s group had a project dedicated to studying chemical reactions with attosecond pulses. Before understanding why attosecond research resulted in the most prestigious award in the sciences, it helps to understand what an attosecond pulse of light is.

How long is an attosecond?

“Atto” is the scientific notation prefix that represents 10-18, which is a decimal point followed by 17 zeroes and a 1. So a flash of light lasting an attosecond, or 0.000000000000000001 of a second, is an extremely short pulse of light.

Related: Nobel Prize in physics awarded to 3 scientists who glimpsed the inner world of atoms with tiny light pulses

In fact, there are approximately as many attoseconds in one second as there are seconds in the age of the universe.

Previously, scientists could study the motion of heavier and slower-moving atomic nuclei with femtosecond (10-15) light pulses. One thousand attoseconds are in 1 femtosecond. But researchers couldn’t see movement on the electron scale until they could generate attosecond light pulses – electrons move too fast for scientists to parse exactly what they are up to at the femtosecond level.

Attosecond pulses

The rearrangement of electrons in atoms and molecules guides a lot of processes in physics, and it underlies practically every part of chemistry. Therefore, researchers have put a lot of effort into figuring out how electrons are moving and rearranging.

However, electrons move around very rapidly in physical and chemical processes, making them difficult to study. To investigate these processes, scientists use spectroscopy, a method of examining how matter absorbs or emits light. In order to follow the electrons in real time, researchers need a pulse of light that is shorter than the time it takes for electrons to rearrange.

As an analogy, imagine a camera that could only take longer exposures, around 1 second long. Things in motion, like a person running toward the camera or a bird flying across the sky, would appear blurry in the photos taken, and it would be difficult to see exactly what was going on.

Then, imagine you use a camera with a 1 millisecond exposure. Now, motions that were previously smeared out would be nicely resolved into clear and precise snapshots. That’s how using the attosecond scale, rather than the femtosecond scale, can illuminate electron behavior.

Attosecond research

So what kind of research questions can attosecond pulses help answer?

For one, breaking a chemical bond is a fundamental process in nature where electrons that are shared between two atoms separate out into unbound atoms. The previously shared electrons undergo ultrafast changes during this process, and attosecond pulses made it possible for researchers to follow the real-time breaking of a chemical bond.

The ability to generate attosecond pulses – the research for which three researchers earned the 2023 Nobel Prize in physics – first became possible in the early 2000s, and the field has continued to grow rapidly since. By providing shorter snapshots of atoms and molecules, attosecond spectroscopy has helped researchers understand electron behavior in single molecules, such as how electron charge migrates and how chemical bonds between atoms break.

On a larger scale, attosecond technology has also been applied to studying how electrons behave in liquid water as well as electron transfer in solid-state semiconductors. As researchers continue to improve their ability to produce attosecond light pulses, they’ll gain a deeper understanding of the basic particles that make up matter.

Scientists in China are building the world's largest "ghost particle" detector 11,500 feet (3,500 meters) beneath the surface of the ocean. 

The Tropical Deep-sea Neutrino Telescope (TRIDENT) — called Hai ling or "Ocean Bell" in Chinese — will be anchored to the seabed of the Western Pacific Ocean. Upon completion in 2030, it will scan for rare flashes of light made by elusive particles as they briefly become tangible in the ocean depths.

Every second, about 100 billion ghost particles, called neutrinos, pass through each square centimeter of your body. And yet, true to their spooky nickname, neutrinos' nonexistent electrical charge and almost-zero mass mean they barely interact with other types of matter. 

Related: 'Air showers' could help reveal cosmic rays' mysterious source

But by slowing neutrinos down, physicists can trace some of the particles' origins billions of light-years away to ancient, cataclysmic stellar explosions and galactic collisions.

That's where the ocean bell comes in. 

"Using Earth as a shield, TRIDENT will detect neutrinos penetrating from the opposite side of the planet," Xu Donglian, the project's chief scientist, told journalists at a news conference Oct. 10. "As TRIDENT is near the equator, it can receive neutrinos coming from all directions with the rotation of the Earth, enabling all-sky observation without any blind spots."

Neutrinos are everywhere — they are second only to photons as the most abundant subatomic particles in the universe and are produced in the nuclear fire of stars, in enormous supernova explosions, in cosmic rays and radioactive decay, and in particle accelerators and nuclear reactors on Earth..

Despite their ubiquity, their minimal interactions with other matter make neutrinos incredibly difficult to detect. They were first discovered zipping out of a nuclear reactor in 1956, and many neutrino-detection experiments have spotted the steady bombardment of the particles sent to us from the sun; but this cascade masks rarer neutrinos produced when cosmic rays, whose sources remain mysterious, strike Earth's atmosphere. 

Neutrinos pass completely unimpeded through most matter, including the entirety of our planet, but they do occasionally interact with water molecules. As neutrinos travel through water or ice, they sometimes create particle byproducts called muons that give off flashes of light. By studying the patterns these flashes make, scientists can reconstruct the energy, and sometimes the sources, of the neutrinos. 

But to increase the chances of ghost particle interactions, detectors have to sit under a lot of water or ice.

China's gigantic new detector will consist of more than 24,000 optical sensors beaded across 1,211 strings, each 2,300 feet (700m) long, that will bob upward from their anchoring point on the seabed.

The detector will be arranged in a Penrose tiling pattern and will span a diameter of 2.5 miles (4 kilometers). When it's operational, it will scan for neutrinos across 1.7 cubic miles (7.5 cubic kilometers). The world's current largest neutrino detector, IceCube, located at the Amundsen-Scott South Pole Station in Antarctica, only has a monitoring area of 0.24 cubic miles (1 cubic km), meaning TRIDENT will be significantly more sensitive and much more likely to find neutrinos.

The scientists say that a pilot project will begin in 2026, and the full detector will come online in 2030.

"TRIDENT intends to push the limits of neutrino telescope performance, reaching a new frontier of sensitivity in all-sky searches for astrophysical neutrino sources," the researchers wrote in a paper outlining the detector, published Oct. 9 in the journal Nature Astronomy.

We all know the universe contains a vast array of elements, ranging from light gases, such as helium, to heavy metals, like lead. But where did all of the elements come from? 

The journey of the elements starts in the earliest moments of the Big Bang, when our universe was only a few seconds to a few minutes old. At that time, the entire cosmos was crammed into a volume millions of times smaller than it is today. Due to the incredibly high densities, the average temperature of all the material in the universe was well over a billion degrees, which is more than hot enough for nuclear reactions to take place. In fact, it was so hot that even protons and neutrons could not exist as stable entities. Instead, the universe was just a sea of more fundamental particles, called quarks and gluons, seething in a raw plasma state.

But the universe would not stay that way for long. It was expanding, which means it was also cooling. Eventually, the quarks could bind together to form the first protons and neutrons without instantly getting demolished. Protons are ever so slightly lighter than neutrons, which gave them an edge in this initial phase of particle production. Once the universe was a few minutes old, it was far too cold to create new protons and neutrons. So those first heavy particles were the only ones the universe was ever going to make (outside of future rare high-energy interactions).

Related: The history of the universe: Big Bang to now in 10 easy steps

By the time the heavy particles finally froze out, there were roughly six protons for every neutron. Neutrons by themselves aren't stable; they decay with a half-life of around 880 seconds. Immediately, some of the neutrons began to decay away, while the remainder started binding with protons to form the first atomic nuclei. Of all the light elements, helium-4, which consists of two protons and two neutrons, has the largest binding energy, which means it's the easiest to form and the hardest to break apart. So almost all of those neutrons went into the production of helium-4.

From calculations like this, cosmologists can predict that the universe started out with a mixture of roughly 75% hydrogen (which is just a bare proton), 25% helium and a small scattering of lithium — which is exactly what astronomers observe.

Stellar nucleosynthesis 

The next stage in the appearance of the elements had to wait for the first generation of stars, which didn't start shining until hundreds of millions of years after the Big Bang. Stars power themselves through nuclear fusion, transforming hydrogen into helium. This process leaves a tiny bit of energy left over. But stars have so much hydrogen available that they can burn for billions, or sometimes trillions, of years. 

Near the ends of their lives, stars like the sun switch to fusing helium instead, turning it into carbon and oxygen before they die as planetary nebulae. This is why carbon and oxygen are so abundant in the universe; after hydrogen and helium, they are the most commonly produced elements. In fact, oxygen is the most common element on Earth, although most of it is bound up with silicates to form the ground beneath your feet.

More massive stars — those with at least eight times the mass of the sun — fuse even heavier elements in their cores. Especially in their final weeks, days and even hours, the most massive stars in the universe create nitrogen, neon, silicon, sulfur, magnesium, nickel, chromium and iron.

Aftermath nucleosynthesis 

That's the end of the line for the formation of elements within stars. Their intense energies are perfectly capable of producing heavier elements, but fusing anything above iron saps energy, rather than producing it, so those heavier elements appear only rarely in the cores of massive stars.

Instead, the rest of the elements in the periodic table are produced when stars die, which they do through a variety of fascinating, complicated and spectacular means. Smaller stars slowly turn themselves inside out, spewing their guts all across their stellar systems. Larger stars explode in violent cataclysms known as supernovas. Both kinds of deaths leave remnants. In the case of small stars, they leave white dwarfs, which are made almost entirely of carbon and oxygen. Larger stars leave behind incredibly dense spheres of neutrons known as neutron stars. 

Gas from a companion star can fall onto a white dwarf, causing it to trigger its own kind of supernova blast. Neutron stars can collide with each other, releasing an enormous amount of energy in an event known as a kilonova.

No matter what, all of these processes involve a lot of radiation, a lot of energy and a lot of particles flying around at high speed — in other words, the perfect soup for fashioning new elements. It's through these calamities that the rest of the periodic table came into being.

It's also through these energetic events that these elements spread beyond the bounds of their home stars and out into the interstellar mix. There, those elements join new gas clouds, which eventually coalesce to form new generations of stars that continue the process of elemental recycling and regeneration, slowly enriching the universe.