Scientists have redefined gravity to explain the Big Bang and perhaps change our picture of the earliest moments of the cosmos. This new framework of "quantum gravity" may explain aspects of the Big Bang that Albert Einstein's 1915 theory of gravity, general relativity, fails to account for — maybe even doing away with the challenging concept of a singularity existing prior to the dawn of the universe.

Proving the concept of quantum gravity is something of a holy grail for physicists, as it would bridge the gap between the explanation we have of the universe on vast cosmic scales (general relativity) and on tiny scales (quantum physics).

However, general relativity doesn't just fail at small scales; the theory also collapses when trying to explain the extreme high-energy conditions that existed during the universe's first moments. To get around this issue, a team of researchers, led by Niayesh Afshordi, a professor of physics and astronomy at the University of Waterloo and Perimeter Institute, explored a theory called Quadratic Quantum Gravity. As it turns out, this theory seems to work even when explaining the high-density, high-temperature birth of the cosmos.

"General relativity works extraordinarily well in many settings, but when we run it back to the Big Bang, and apply it to the inside of black holes, it predicts a singularity: a moment where density, curvature and temperature formally become infinite. That is usually a sign that the theory is being pushed beyond where it can be trusted," Afshordi told Space.com. "In other words, general relativity is likely incomplete for describing the very first moments of the universe, when quantum effects should also matter."

Expanding the standard picture of general relativity

Afshordi explained that in the standard picture of the Big Bang, scientists usually start with Einstein's theory of gravity, then add extra ingredients to explain the earliest moments of the universe, most notably a hypothetical "inflation field" to account for the initial rapid expansion of the cosmos."

Our approach asks whether some of that early-universe behavior could come directly from gravity itself, once gravity is extended in a way that remains better behaved at extremely high energies," he said. "So, instead of treating the Big Bang as a point where our equations fail and then patching over that with additional assumptions, we study a theory in which gravity already contains the ingredients needed to describe that ultra-early phase more consistently. This is what physicists call an ultraviolet completion: a theory that remains complete and self-consistent even at arbitrarily high energies."

The team's quantum-consistent extension of gravity recovers a model of early cosmic inflation, while also potentially removing the troubling concept of an initial singularity.

"Our model provides a very good fit to current data, in some cases better than many standard inflationary models," Afshordi said. "What surprised me most was how naturally an inflation-like phase emerged once the theory was treated in a consistent high-energy, or ultraviolet complete, framework. We often think of inflation as something that must be added on top of gravity, so it is striking that it may instead arise from gravity itself. More broadly, it was encouraging to see that a relatively minimal extension of Einstein's theory could already go a long way toward resolving the deep problem of our cosmic origins."

The researcher added that the next step for the team is to sharpen the model’s observational predictions and compare them carefully with future data.

"There are two main directions. The first is theoretical: we want to understand the framework more fully and test how robust the conclusions are beyond the simplified setting we studied," Afshordi continued. "The second is observational: we want to work out clearer predictions for primordial gravitational waves and other relics from the early universe. That will help determine whether this idea can be distinguished from more conventional models of inflation."

Observational evidence to help confirm the team's theory could come from some of the oldest observable signals in the universe, especially tiny ripples in space and time called primordial gravitational waves as well as subtle imprints in a cosmic fossil called the cosmic microwave background (CMB), a remnant of the universe's first light. "These are among the few probes that can tell us directly about physics at extremely early times," Afshordi said. "If future observations detect the right pattern of primordial gravitational waves, or other distinctive imprints in the CMB, that could provide a way to test whether this picture of the early universe is correct, or whether a more conventional explanation is needed."

The team's research was published in the journal Physical Review Letters.

A team of scientists is proposing a bold alternative to the Big Bang theory, suggesting that our universe may have formed inside a colossal black hole residing in a larger, parent universe. The Big Bang theory, along with Einstein's general relativity, has successfully explained major cosmological phenomena, including the cosmic microwave background, the universe's large-scale structure, and its accelerating expansion often linked to dark energy.

Yet, fundamental problems remain with this theory, such as the unexplained nature of dark energy and dark matter, the singularity at the Big Bang, and inconsistencies between general relativity and quantum mechanics. "Most scientists have responded by proposing either a mysterious new form of energy — [called] dark energy — or by modifying the laws of physics," Enrique Gaztañaga, professor at the University of Portsmouth, told Space.com. "But these are drastic steps."

Gaztañaga says he and his colleagues wondered if a simpler explanation might suffice. "[Our study] began with a simple but profound question: Why is the expansion of the universe accelerating?" he said. "Our entire observable universe lies inside its own gravitational radius, meaning that from the outside, it would appear like a black hole. That led to a radical idea: What if the universe formed in the same way a star collapses into a black hole?"

The universe is believed to have begun as an extremely hot, dense point known as a singularity that underwent a rapid expansion just fractions of a second after the Big Bang. "If we rewind that expansion using known physical laws, we eventually reach a point of infinite density — a singularity — where space, time, and matter all seem to begin," said Gaztañaga. "Because the physics breaks down at that point, it has often been interpreted as a creation event: the beginning of everything."

The new study explores the idea that the universe may not have begun with a singularity but instead emerged from the collapse of a massive cloud of matter in another universe. To investigate, the research team ran simulations in search of a solution that could address some of the inconsistencies in current cosmological theories — and unexpectedly found that an exact, analytical solution describing the fundamental principles of this process already exists.

"Under the right conditions, this collapse doesn't end in a singularity — instead, it bounces and begins expanding again," said Gaztañaga. "That bounce mimics what we call the Big Bang."

While "bouncing scenarios" have been proposed in the past, this model stands out by relying solely on known laws of physics. It avoids introducing speculative particles or forces and describes a purely gravitational collapse occurring within a black hole.

"In quantum mechanics, two identical particles (like electrons or neutrons) cannot occupy the same state — they can't be in the exact same place at the same time," explained Gaztañaga. "This principle creates a kind of pressure — called degeneracy pressure — that resists compression. It's what stops the cores of dying stars from collapsing endlessly, and it's what can trigger a supernova explosion. In our model, it's this same quantum effect that halts the universe's collapse and causes it to bounce."

A hypothesis not included in the current paper is that gravity interacts directly with the Higgs field — a subatomic quantum field responsible for giving particles mass, as confirmed by experiments at the Large Hadron Collider.

In very dense and high-energy environments, quantum effects become important, says Sravan Kumar, a visiting research fellow at the University of Portsmouth and another of the study's authors. If gravity interacts with the Higgs field under these conditions, this interaction could change how gravity behaves. For example, if the interaction between gravity and the Higgs field becomes repulsive at extremely high energy densities, it could counteract the gravitational collapse. Instead of collapsing into a singularity, the universe could bounce — reversing from contraction to expansion.

"This could explain the high densities seen in cosmic microwave background data and suggest that a gravitational bounce might naturally link gravity with quantum mechanics, without needing speculative new theories," said Kumar.

"[If there is sufficient matter], gravity overcomes quantum forces such as degeneracy pressure, [which can stabilize different kinds of stars from collapse]," added Swaraj Pradhan, a visiting master's student at the University of Portsmouth and another of the study's contributors. "While we understand these forces in white dwarfs and neutron stars, we don't have firsthand data at the extreme densities after black holes form.

"Rather than presuming a singularity where physics fails, it is fair to think that quantum effects may prevent actual singularities," Pradhan continued. "The most honest answer is that we don't yet know for sure. Our model simply extrapolates well-tested [ideas] while remaining consistent with known physics."

The model predicts a small positive spatial curvature of the universe and the existence of relic objects, like primordial black holes or neutron stars, formed before a cosmic bounce.

"The gravitational bounce of our model is based on a small positive spatial curvature of the universe, a consequence of the finite mass and radius of the black hole into which the universe has collapsed, and the Pauli exclusion principle stating that not two quantum particles, more specific fermions, cannot occupy the same quantum state simultaneously," explained Michael Gabler, researcher at the University of Valencia, and another of the study's authors. "The collapse occurs completely within the framework of Einstein's theory of general relativity, and we expect the existence of relic objects, like primordial black holes or neutron stars, formed before a cosmic bounce."

"If we find such relics, especially in the early universe, it would be strong evidence in favor, [of this theory]," added Gaztañaga. "In fact, some early results from the James Webb Space Telescope (JWST) have found surprisingly old galaxies close to the origin of the universe. These findings may be hard to reconcile with the standard Big Bang timeline, but they could make sense if early relics like supermassive black holes helped galaxies form faster.

"Of course, suggesting that the Big Bang wasn't the absolute beginning of everything is controversial," continued Gaztañaga. "[Scientists] can be reluctant to move beyond familiar models. But challenging long-held assumptions is essential to scientific progress."

A study about this theory has been published in the journal Physical Review D.

Not long after the James Webb Space Telescope (JWST) began its science operations, astronomers announced that they had discovered galaxies in the early universe that were far too large, bright and full of stars for their age. While headlines around the world claimed that these galaxies were "breaking" our understanding of the Big Bang, the truth is much more nuanced — and much more interesting.

The Big Bang theory is our general picture of the history of the universe, starting in its deep past, when the cosmos was much smaller, hotter and denser than it is today. This model, initially developed in the early 20th century, has survived a battery of observational tests and is extremely good at explaining a variety of cosmological observations, including the redshifting of light from distant galaxies, the appearance of leftover radiation in the form of the cosmic microwave background, the abundances of light elements, and the evolution of galaxies and larger structures.

While the Big Bang theory can't say for certain which galaxies will appear where, it can talk about probabilities. For example, cosmologists can say roughly how many small galaxies, how many medium galaxies and how many large galaxies should appear in a given volume at a certain age of the universe. But until JWST, we did not have direct observational access to the earliest stages of galactic evolution — something the telescope was explicitly designed to study.

In 2022, astronomers announced that they had found extremely distant galaxies that were surprisingly, weirdly large. They had measured the redshift of the galaxies to be over 16, implying that these galaxies existed just 200 million to 250 million years after the Big Bang. Yet they were gigantic and appeared to be fully formed, with spiral arms and everything.

Related: No, the Big Bang theory is not 'broken.' Here's how we know. 

These galaxies seemed far outside the expectations of the Big Bang theory; they were like finding teenagers in a kindergarten classroom. So what was going on?

Bending cosmology 

Cue the brazen headlines proclaiming the death of the Big Bang theory. But those stories left out a crucial detail: Astronomers estimated the redshift of those galaxies through a technique known as photometry, which is incredibly uncertain. A full evaluation of the ability of those galaxies to "break" cosmology would have to wait for a more precise measurement of their redshift, and hence their age.

When those more precise measurements finally came a few months later, those galaxies turned from record-shattering to just … normal galaxies. For example, one galaxy's redshift was revised from over 16 to just 4.9, moving its age from 240 million years after the Big Bang to well over a billion years. That's more than enough time for the normal Big Bang theory to explain their sizes and shapes.

But along with those less-exciting revisions came some new confirmed redshifts of other galaxies, including JADES-GS-z14-0, the current most distant known galaxy, with a redshift of 14.32. This galaxy was alive and well when the cosmos was just 290 million years old.

Astronomers fully expected galaxies to exist 290 million years after the Big Bang; that's why they built JWST. And as galaxies go, JADES-GS-z14-0 is certainly a juvenile — it's only 1,600 light-years across, compared with the Milky Way's 100,000 light-years. But interestingly, the galaxy is rather bright and full of stars — not enough to outright break cosmology, but enough to open up some questions about the origins and development of the first galaxies to appear in the universe.

Building cosmology 

It's quite possible that the Big Bang theory is wrong; scientists must maintain the mental discipline to admit the possibility. But with such a wealth of evidence behind it, the Big Bang is unlikely to be unseated from a single observation. And it's worth reiterating that JWST is doing exactly what we designed and built it to do: answer some major lingering questions about how the first stars and galaxies appeared.

It's entirely possible that cosmologists will be able to explain the appearance of galaxies like JADES-GS-z14-0 within the framework of the Big Bang without having to make any major revisions. For example, large black holes may have appeared before these galaxies did, and their superpowered gravitational attraction may have triggered bright bursts of star formation. Or perhaps supernova feedback and other mechanisms caused the first galaxies to be richer with stars than present-day galaxies, making those early galaxies appear mighty despite their small size.

Or maybe our initial observations are biased toward these small-but-bright outliers and further campaigns will reveal larger populations of more mundane galaxies, thus reducing the tension with galaxy formation models.

And lastly, perhaps we need to add some new ingredient to the universe, like allowing for dark energy to evolve with time, to produce these kinds of galaxies at such early times.

This is exciting enough on its own, without the need to upend the Big Bang as we know it. There are more than enough mysteries and hidden corners within the universe to keep astronomers up at night wondering about the possibilities — and up in the morning to keep working on how to solve them.

We think of galaxies as ancient. Our own galaxy, the Milky Way, formed 13.6 billion years ago, and the James Webb Space Telescope has allowed us to peer back to some of the first galaxies in the early universe. But are galaxies still being born today?

It's a fun question to tackle because it lets us dig into the messy, complicated, beautiful process of galaxy formation. Let's take a look at the possibilities.

First answer: No

Galaxies are pretty easy to identify. They are large collections of stars, gas and dark matter. They are largely distinct from one another; a typical galaxy is roughly 100,000 light-years across, while the typical distance between galaxies is roughly 1 million light-years. 

Sometimes, galaxies merge or clump together inside clusters, but with a few exceptions, we can largely separate one galaxy from another. They're like towns in the countryside: The distance between towns is larger than the towns themselves, so they're easy to spot and define. Sometimes, towns bump up next to each other, and sometimes, a sprawling city consumes its neighbors. But by and large, a town is just a town.

Related: Did monster black holes or galaxies come first? The James Webb Space Telescope may have a surprise answer

Defining the start of a galaxy, however, is a different matter. Galaxies emerged in the early universe through a gradual process starting all the way back in the first second of the Big Bang. At that time, tiny pockets of higher-than-average density emerged and steadily grew over the next few hundreds of millions of years. At first, only the dark matter could pour in, as regular matter was busy getting tangled up with itself. But once the pockets of dark matter grew large enough, they drew in the surrounding regular matter.

As the regular matter gathered, it compressed, fragmented and gave light to the first stars. These protogalaxies went on to consume more gas, merge with neighbors and grow to become the fully formed galaxies we see today.

So, in many senses, no new galaxies appear today. The process of building them — of seeding them as tiny differences in density or the initial gathering of dark matter — is over and done with, an act that took place in the ancient cosmos and never again. There are no more protogalaxies — no more clouds of gas just waiting for the chance to compress and create a new galaxy — in the present-day universe.

When it comes to galaxies, what we see is what we get.

Second answer: yes

But that's just one way to define the beginning of a galaxy. We can also look at another pivotal step: the appearance of the first stars. Going back to the city analogy, there's a difference between when a city is first planned — its outlines defined with boundary markers and survey lines — and when the first people start moving in.

If we focus just on star formation, we see that this is an ongoing process that continues even into the modern-day universe. In recent years, astronomers have built a detailed understanding of a measure called the stellar mass function. This is a basic demographic census that maps how many stars are lighting up in each galaxy — or, put another way, how much mass is in the form of stars within each galaxy at different epochs in the universe.

Stars make up only a tiny percentage of a galaxy's mass; the rest goes to dark matter and random clumps of gas. However, stars make a galaxy what it is, and they're much easier to observe than any other galactic component.

With new surveys that have sampled galaxies across the universe, astronomers have recently discovered that the stellar mass function is going up across the board. This means that there are more small galaxies, medium galaxies and large galaxies than there were billions of years ago. 

The new small galaxies don't come from the emergence of protogalaxies in seeds of dark matter; they are already-existing clumps of material that are just beginning star formation. The larger galaxies, on the other hand, are driven mostly by the continued merger of smaller galaxies.

It won't last forever

So, in at least one important way, new galaxies are continuing to appear on the cosmic scene as they light up with new rounds of star formation. They've always been there, hanging out for billions of years, but they're just now making themselves visible. This process is viable because star formation is incredibly inefficient. Most of the gas within a galaxy will never turn into stars, and it can proceed for very long periods without using up much material — and it can take a galaxy a really long time to get started in the first place.

But sadly, the party won't last forever. The problem is that not only is the universe expanding, but its expansion is accelerating — an effect known as dark energy. Although astronomers still don't understand what drives dark energy, they can observe its effects on the rest of the universe: It's spreading everything out.

As the universe ages, it's harder and harder for material to clump together to form new galaxies and drive continued star formation. In fact, the peak of star formation passed billions of years ago. While new galaxies continue to light up, the rate of emergence is slowing down, with fewer and fewer new galaxies appearing every year.

We still have plenty of time — galaxies will continue forming stars for hundreds of billions of years to come — but we should still enjoy the party while it lasts. 

The second and fourth most distant galaxies ever seen have been spotted by the eagle eye of the James Webb Space Telescope (JWST), supporting the basic picture of galaxy formation as described by the Big Bang theory.

The discovery was made possible thanks to a huge helping hand from a massive gravitational lens in the form of the galaxy cluster known as Abell 2744, nicknamed Pandora's Cluster, which is located about 3.5 billion light-years away from us. The immense gravity of the cluster warps the very fabric of space-time sufficiently to magnify the light of more faraway galaxies. 

Using the James Webb Space Telescope to search for early galaxies magnified by this cosmic lens, Bingjie Wang of the Penn State Eberly College of Science and member of the JWST UNCOVER (Ultradeep NIRSpec and NIRCam Observations before the Epoch of Reionization) team discovered two of the highest redshift galaxies ever seen.

Related: James Webb Space Telescope confirms 'Maisie's galaxy' is one of the earliest ever seen

Cosmological redshift is the stretching of light wavelengths, provoked by the continuous expansion of the universe. The more distant a galaxy is, the more the universe had expanded while that galaxy’s light traveled across space to reach us, and therefore, the more the wavelengths of that light are stretched. As wavelengths get stretched out in this manner, they go from tighter, blueish ones to redder ones, eventually falling into the invisible, infrared region of the electromagnetic spectrum. Galaxies that existed just between 300 and 400 million years after the Big Bang have had their light stretched into those infrared wavelengths that can't be seen by humans, but can indeed be detected by the JWST’s Near-Infrared Camera (NIRCam) and Near-Infrared Spectrometer (NIRSPec).

Wang and her team were able to identify the lensed images of two high-redshift galaxies. One, designated UNCOVER-z13 ("z" is shorthand for "redshift"), has a redshift of 13.079, confirming it to be the second most distant galaxy known. (The most distant confirmed galaxy is JADES-GS-z13-0, which was also discovered by the JWST in 2022 and has a redshift of 13.2.) We see UNCOVER-z13 as it existed just 330 million years after the Big Bang.

The other galaxy recently discovered, UNCOVER-z12, has a redshift of 12.393, placing it in fourth place in the all-time list of most distant galaxies. We see this realm as it was just 350 million years after the Big Bang.

What marks the two UNCOVER galaxies out as different is their appearance. Other galaxies seen at similarly high redshifts seem to be point-like, indicating they are very small —  just a few hundreds of light years across. The UNCOVER galaxies, on the other hand, have structure.

"Previously discovered galaxies at these distances … appear as a dot in our images," Wang said in a statement. "But one of ours appears elongated, almost like a peanut, and the other looks like a fluffy ball."

These galaxies are also bigger, with UNCOVER-z12 sporting an edge-on disk about 2,000 light years across, which is six times larger than other galaxies seen in this era.

"It is unclear if the difference in size is due to how the stars formed or what happened to them after they formed, but the diversity in the galaxy properties is really interesting," said Wang. "These early galaxies are expected to have formed out of similar materials, but already they are showing signs of being very different than one another."

Although the dichotomy in galaxy properties, even at this early stage in the universe, is eye-opening, both of the newfound realms have  general characteristics that are strongly supportive of the Big Bang model. This model describes how, in the aftermath of our universe's creation, galaxies began life small before growing rapidly through mergers with other galaxies and gas clouds. 

This growth, in turn, spurred more star formation, which ultimately increased the abundance and variety of elements contained within the young galaxies, introducing substances to them that are heavier than hydrogen and helium. The galaxies uncovered by UNCOVER — if you’ll pardon the pun — are young, small, have a low abundance of heavy elements and are actively forming stars, all of which supports "the whole paradigm of the Big Bang theory," Joel Leja, who is an assistant professor of astronomy and astrophysics at Penn State University and a co-researcher on Wang’s team, said in the statement.

Interestingly, the JWST has the ability to see even higher redshift galaxies than UNCOVER-z13 and -z12, meaning they'd be even younger — but it didn’t detect any being lensed by the Pandora Cluster. "That could mean that galaxies just didn’t form before that time and that we’re not going to find anything farther away," said Leja. "Or it could mean we didn’t get lucky enough with our small window."

Astronomers will keep looking, using a multitude of lensing clusters to open up new windows into the deep universe in search of some of the first galaxies.

The discovery was reported on Monday (Nov. 13) in Astrophysical Journal Letters.

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.

Astronomers have found a new way to detect one of the oldest features of our universe.

These Baryon Acoustic Oscillations, or BAO, are subtle wrinkles that flowed through cosmic matter during the first 380,000 years of the universe's existence. Today, they are popular subjects in space science because they're one of the very few hints of the Big Bang that can still be traced — and importantly, astronomers can use the presence of BAOs to measure cosmic distances as well as the rate at which the universe is expanding.

While astronomers have historically focused on galaxy clusters to observe these cosmically imprinted waves, a new study aims to sniff out some overlooked waves by looking at galaxy shapes and orientations rather than just clusters as a whole. These features, the study researchers write, can offer a "promising cosmological probe" yet have been ignored so far.

Related: No, the Big Bang theory is not 'broken.' Here's how we know.

To fill this gap, the team looked at oddities in the orientations of about one million galaxies by studying how stretched those galaxies are. In turn, that revealed the number of nearby galaxies which exert a gravitational pull. Then, researchers zoomed in on galaxies that were not as intensely stretched, which stood out as oddballs in the database.

"It is in those points, where galaxies do not point where they should, where statistics tell us that the Baryon Acoustic Oscillations are located, since these waves also act as points of gravity attraction," Antonio Cuesta, an astrophysicist at the University of Córdoba in Spain and one of the authors of the new study, said in a statement.

As the new way of detecting BAO is quite independent, it helps researchers in measuring the locations of galaxies in the universe and their distances more accurately, according to the study. Ultimately, this knowledge could be used to better map the universe, scientists say.

The novel method also reveals more information about the universe's expansion — which is a puzzle in itself because it is accelerating at a rate the scientists can't quite explain. According to the team, the mechanism could also help calculate the amount of the elusive dark matter and dark energy that lies in our universe — the latter of which is actually suspected to be causing space's accelerating expansion somehow.

The new study is not the first effort to detect BAO in the universe. That milestone belongs to two independent teams who spotted the signal in 2005 while analyzing data of nearby galaxies. At the time, the size of BAO signals in the universe was found to be about 150 million parsecs.

One of the goals of the European Space Agency’s Euclid telescope, which launched early July to hunt for dark matter and dark energy, is to measure at least some of these signals across the universe. 

Hovering about a million miles (1.6 million km) above Earth, the telescope recently sent home its first starry images.

The paper was published last month in the journal Nature Astronomy.

"The cosmos is within us. We are made of star stuff. We are a way for the universe to know itself." Carl Sagan

During the course of his 1980s mini-series "Cosmos," astronomer and science communicator Carl Sagan said many inspirational and profound things based on our understanding of the universe. But arguably, none have resonated with the general public more than the statement above. 

With this sentiment, Sagan, who passed away in 1996 at the age of 62, was talking about the cosmic origins of humanity.

And in a new video from the European Southern Observatory (ESO), part of the Chasing Starlight series, astrophysicist Suzanna Randall explains what this statement means and how it relates to the elements that comprise our bodies.

Related: How did supermassive black holes get so big so fast just after the Big Bang?

How the universe became more metal

Randall explains that shortly after the Big Bang, the dense and hot universe was comprised mainly of the two lightest elements, hydrogen and helium, as well as a smattering of heavier elements collectively known as metals. 

"But, you can't make up something as complex as the human body of just helium and hydrogen," she explains. "So, where do the other more complex elements that make up our body and the rest of the universe come from?"

Winding the cosmic clock forward to around 100 million years post-Big Bang, Randall explained that this is when the first nebulas — vast clouds of hydrogen and helium — had formed in the universe. When overly dense regions of these nebulas gathered more and more mass from their surroundings, they eventually collapsed under their own gravity, birthing the first generation of stars. 

But, like the universe at that time, these stars were all hydrogen and helium with a negligible amount of metals. 

This first generation of stars fused hydrogen in their cores to create helium, something that Randall points out the sun, our 4.6 billion-year-old star, is doing today.

Why did stars have to die for you to live?

This all means that, at the time when the first stars existed, the universe still didn't have enough heavy elements needed to form our bodies like nitrogen, oxygen and carbon. 

But this changed as the first generation of stars began to die.

"When the hydrogen in the core of the star has been used up, things start happening very quickly," Randall says. "The star enters a new phase of its life, called the red giant phase."

During the red giant phase, the cores of these first stars would have contracted. Meanwhile, their outer layers, where the nuclear fusion of hydrogen to helium was still taking place, would have puffed out and increased the stars' sizes by as much as 100 times. The core would've continued to contract until conditions at the hearts of the stars, which would've been much more massive than the sun, became hot and dense enough to start fusing helium into heavier elements. And there, elements like carbon and oxygen, which comprise around 84% of our bodies, spawned into existence.

"The majority of the atoms in my body are actually created deep inside stars in these incredibly hot stellar furnaces," Randall explained.

The universe finally got the "stuff" needed for life, but that stuff wasn't of much use locked in the hearts of red giant stars. Don't worry, though, these elements wouldn't stay confined for long — not in cosmic terms, anyway.

"Stars with more than about eight solar masses continue to fuse elements in their core, and they create heavier and heavier elements — as heavy as iron," Randall said. "At some point, they have to die, and they go out with a bang. They explode as supernovae."

During those cosmic explosions, Randall says some astronomers believe even heavier elements, like gold or platinum, had formed. However, other scientists think it would've had to take the collision of two stellar corpses, called neutron stars, and therefore a kilonova explosion to create such precious elements. 

What is certain about the supernova explosions of the universe's first stars is they took all the elements forged by these stars during their lives and flung them out into the cosmos. 

Eventually, these elements were integrated into nebulas and thus became part of the next generation of stars born from those vast dust clouds. 

That means this next generation of stars was more "metal-rich" than the preceding generation. This continued through to the creation of the third generation of stars, one of which is the sun.

Enriched material from the nebula that created the sun, but didn't manage to become part of our star 4.6 billion years ago, then formed a disk of material around the stellar body called a protoplanetary disk.

As the name implies, it is from this disk of material that the planets of the solar system, including Earth, formed. And it is from this disk that the elements that make up our bodies are derived. 

"As it turns out, Carl Sagan was right. We are literally made up of star stuff," Randall said. "And the story of stars in their lives is also the story of the elements that make up our body. We're all part of this grand cosmic cycle."

As the astrophysicist points out, however, we maybe shouldn't let this go to our heads too much. As an ego-cleanser, Randall concludes by adding: "Before you get too excited, cockroaches are also made up of star stuff."

Astronomers have begun measuring of the most distant star ever detected, thanks to the powerful eyes of the James Webb Space Telescope (JWST).

That star, known as Earendel, was discovered last year by the Hubble Space Telescope. It has taken 12.9 billion years for Earendel's light to reach Earth, meaning the star was shining less than a billion years after the Big Bang spurred our universe into existence. However, Earendel doesn't lie a mere 12.9 billion light-years away from us.

Because the universe has been expanding at an accelerating rate since the Big Bang, the star now lives a whopping 28 billion light-years from Earth.

 Hubble was able to spot Earendel thanks to a phenomenon known as gravitational lensing, in which the gravity of a massive foreground object sort of acts like a lens as it warps the very fabric of space and time, bending and brightening light from a more distant body as that light passes by. 

The JWST team employed this same strategy by harnessing the space-warping power of a gravity cluster called WHL0137-08 that just so happens to line up with Earendel. 

The $10 billion scope, which views the universe in infrared light, got a glimpse of Earendel last summer, just after beginning its science operations. But that glimpse has now become something more, as researchers now have enough information to begin characterizing the record-breaking star.

Photos: Amazing images from James Webb Space Telescope's 1st year

For example, JWST's NIRCam (Near-Infrared Camera) instrument "reveals the star to be a massive B-type star more than twice as hot as our sun, and about a million times more luminous," NASA officials wrote today (Aug. 9) in a statement announcing the new Earendel observations.

Our sun, in case you're wondering, is a G-type star with a surface temperature around 10,000 degrees Fahrenheit (5,500 degrees Celsius). Earendel — which was named after a character in J.R.R. Tolkien's "The Silmarillion," a prequel to "The Hobbit" and the "Lord of the Rings" trilogy — may not be alone in its distant quarter of deep space. 

Based on the star's colors, "astronomers think they see hints of a cooler, redder companion star," NASA officials wrote. "This light has been stretched by the expansion of the universe to wavelengths longer than Hubble's instruments can detect, and so was only detectable with Webb."

The existence of a companion would not be a surprise; most big stars like Earendel are part of binary systems, NASA officials noted.

The JWST's observations are also shedding new light on the Sunrise Arc, the galaxy that Earendel calls home. 

For example, the scope has identified a star-forming region in the galaxy that's thought to be less than five million years old from our perspective. Its imagery also revealed a more established star cluster near Earendel that appears to be gravitationally stable and has perhaps even persisted into the present day — if its stars are still alive, that is.

And more insights are bound to emerge as JWST continues to study Earendel and other ancient stars.

"The discoveries have opened a new realm of the universe to stellar physics, and new subject matter to scientists studying the early universe, where once galaxies were the smallest detectable cosmic objects," NASA officials wrote. "The research team has cautious hope that this could be a step toward the eventual detection of one of the very first generation of stars, composed only of the raw ingredients of the universe created in the Big Bang — hydrogen and helium."

A feature of light absorption by hydrogen surrounding early galaxies could be used as a novel new probe into the mysteries of dark matter and how it influenced the evolution of the universe during the cosmic dark ages. 

Scientists have long theorized that dark matter, a mysterious substance that makes up around 85% of the matter in the universe, played a huge role in the formation of early galaxies. But because dark matter doesn't interact with light (unlike the "normal" matter that makes up stars, planets and us), its nature remains unknown. That means the precise role it played as galaxies began to form remains a gap in cosmological models. 

To investigate this puzzle, scientists from Northeastern University in China and the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC) have suggested a novel probe to shed light on both the nature of dark matter and the early formation of galaxies.

Related: We have never seen dark matter and dark energy. Why do we think they exist?

One possible way of investigating the particles that comprise dark matter and their mass has been by studying small-scale structures in the universe. The problem comes when attempting to do this for a period called "cosmic dawn," around 380 million years after the Big Bang, a time when the earliest stars were just being born. There were thus few viable light sources to illuminate this ancient epoch for astronomers.

But there were atoms during this era, in the form of a gas of the lightest chemical element, hydrogen. Like all elements, hydrogen absorbs light at characteristic wavelengths, leaving its fingerprint on light passing through it. 

Searching for dark matter in a cosmic forest

Atomic hydrogen gas in and around the small-scale structures that existed during the cosmic dawn, which ended around one billion years after the Big Bang, creates characteristic absorption lines at 21 centimeters, in the radio range of the electromagnetic spectrum. These are collectively called the 21-cm forest, which has been proposed as a potential probe of gas temperature and dark matter during cosmic dawn for over 20 years.

This has remained just a theoretical concept, however, due to the fact that light from this era has been traveling for around 13.4 billion years to reach us. Along the way, it has lost energy and had its wavelength stretched and its frequency lowered, moving it down the electromagnetic spectrum toward the red region and beyond to infrared. 

The more distant the source of light, the more extreme this "redshift" process is. With starlight absent, using the 21-cm forest as a dark matter probe requires radio-loud sources like quasars to be seen at cosmic dawn and thus at high redshift. But signals from such radio sources in this epoch are faint, and these high-redshift background sources are difficult to identify.

This situation may be about to change, however. Not only have a number of high-redshift radio-loud quasars been discovered recently, but the world’s largest radio telescope, the Square Kilometre Array (SKA), began construction in Australia and South Africa in December 2022 and will soon open its sensitive radio eye on the universe. This suggests that detecting and using the 21-cm forest may soon be feasible.

Related: SKA Observatory: A guide to the soon-to-be largest radio telescopes in the world

The team behind the new study thinks that measuring the distribution of energy of the 21-cm forest, or its "power spectrum," will make it a plausible probe to simultaneously measure dark matter properties and the thermal history of the universe. 

This could help researchers distinguish between a cold dark matter model of the universe  —  one with massive dark matter particles moving slowly in comparison to the speed of light  —  and a hot dark matter model, with lighter and more fast-moving dark matter particles.

"By measuring the one-dimensional power spectrum of the 21-cm forest, we can not only make the probe actually feasible by increasing the sensitivity, but also provide a way to distinguish the effects of warm dark matter models and early heating process," said National Astronomical Observatories researcher Yidong Xu, corresponding author of the new study. "We will be able to kill two birds with one stone!"

As long as cosmic heating wasn't too extreme during cosmic dawn, the low-frequency capabilities of phase 1 of SKA’s operations should mean scientists can constrain the mass of dark matter particles and gas temperature. If cosmic heating was too great, then the second phase of SKA will see the instrument enlarged, leading to the use of multiple background radio sources delivering the same constraints.

As the potential use of the 21-cm forest as a dark matter probe is tied to observations of high-redshift background radio sources, the next step in this research is identifying more radio-bright sources during the cosmic dawn, including more radio-loud quasars and the afterglows of gamma-ray bursts. 

These sources can then be followed up once SKA once it begins observing the universe in 2027, thus allowing astronomers to shed more light on the mysteries of both dark matter and the first galaxies.

The team’s research was presented in the July 6 edition of the journal Nature Astronomy.

Just as Charles Darwin once used the fossil record to tell the story of the evolution of life on Earth, astronomers are using the first light ever to shine through the universe to understand events that have shaped the cosmos.

This first light is called the "Cosmic Microwave Background (CMB)," leftover radiation which is spread almost evenly through the universe. The CMB carries with it the signatures of the physical processes of the early universe and possesses unique features that can be used to determine the make-up of the universe. 

Just like how the study of biological evolution has evolved since the time of Darwin, the ways in which cosmologists use this cosmic fossil have changed, and future missions are set to increase the focus on the CMB and what it can teach us about how the universe evolved.

Related: What is the cosmic microwave background?

On Monday, July 2, at the National Astronomy Meeting 2023 (NAM 2023) held at Cardiff University in the U.K., astrophysicist Erminia Calabrese offered overviews of both where CMB science is currently and where it is headed in the near future.

"The reason why this light has been really the driving force of modern cosmology is that it has been there throughout the whole of cosmic history," Calabrese said. "It was there from the beginning, it went through everything that the universe experienced. It traveled across the formation of the first stars, the forming and evolving large-scale structure of the universe.

"While taking this journey towards us, it has basically captured imprints from all these physics, and carries it with it when it today."

Let there be light: What is the Cosmic Microwave Background?

If you could journey back around 380,000 years in cosmic history to the point at which the universe was filled with a dense hot soup of electrons and protons, the first thing you would notice is how dark the cosmos is. 

The reason this early epoch in the 13.8 billion-year history of the universe is a literal cosmic dark age is because the abundance of free electrons meant that photons, particles of light, were endlessly scattered, thus preventing them from traveling. At this time, the universe was essentially opaque to light. 

"So what we are looking at is the very first light ever emitted in the universe, composed of photons that were emitted during the Big Bang," Calabrese explained. "The photons were trapped in interactions with everything else, meaning any particle phenomenon that was happening in this very hot and dense phase of the universe was interacting with these photons." 

That means as they were trapped, the photons were creating a record of the physics in the early universe, but they couldn't stay trapped and in equilibrium with matter forever. 

Eventually, undergoing rapid cosmic inflation as a result of the Big Bang, the universe expanded and cooled enough to allow electrons to bond with protons and form the first neutral atoms. This is known as the period of recombination, even though electrons and protons had not been previously connected. 

Initially, the light that comprises the CMB was incredibly hot and energetic, but as the universe continued to expand it has cooled and lost energy, which has seen the frequency of this radiation reduced to the microwave region of the electromagnetic spectrum.

Calabrese explains that currently, the CMB takes the form of a radiation field with a temperature of 2.7 Kelvin (-455 degrees Fahrenheit or -270.4 degrees Celsius).

How do scientists use the Cosmic Microwave Background?

Because recombination happened all over the universe at the same time, CMB radiation streams to us from all directions evenly. That means that this cosmic fossil looks the same in all areas of the sky  —  which scientists describe as being isotropic. 

This sameness, even at opposite sides of the universe in areas not currently in contact, is one of the key pieces of evidence that the universe once existed in a hot and dense state and then underwent a period of rapid inflation, which we now call the Big Bang. But it is in the areas where tiny differences arise that scientists find a useful cosmic fossil record.

Within the CMB are small deviations from this uniformity called anisotropies. It is through these anisotropies that the CMB contains information about the evolution of the universe.

Small-scale anisotropies in the CMB represent tiny fluctuations in density in the early universe that eventually resulted in the creation of galaxies and galaxy clusters. Though they may be tiny, without these variations, the large-scale structure we see in the universe today couldn't have taken shape. 

It is larger anisotropies that reveal the contents of the universe and the abundance of these elements throughout cosmic history. This includes not just visible "everyday" matter comprised of atoms and constituting stars, planets, cosmic gas clouds, and us, but also invisible dark matter and dark energy, the forces that are driving the current day accelerating expansion of the universe. 

"In particular, there are three methods we work with to study the CMB: We can go to space, and we've had three different generations of satellites that have been dedicated to measuring the CMB anisotropies," Calabrese explained. "You can stay on Earth but try to get higher in the atmosphere with stratospheric balloons, or you just stay on the ground and then deal with the atmosphere. All these methods have got pros and cons; no single experiment can give you access to everything."

In Calabrese's NAM 2023 talk, the researcher highlighted the need for future CMB studying missions that could answer fundamental questions such as what is dark matter made of and what is the large-scale distribution of mass in the universe. 

One such mission mentioned by Calabrese is the Japanese Aerospace Exploration Agency (JAXA) mission known as the Space Lite (Light) satellite for the study of B-mode polarization and Inflation from cosmic background Radiation Detection (LiteBIRD).

LiteBIRD will observe the entire sky for three years from orbit, and JAXA says it will achieve unprecedented sensitivity, allowing it to precisely distinguish between the CMB and foreground radiation signals from sources like cosmic dust. That means that LiteBIRD, set to launch in 2028, could help fill in the gaps in cosmic evolution that current Big Bang models can't explain.

"We really don't have answers to the big key fundamental questions that we were aiming to answer with CMB temperature, and now we need to take the next step and continue exploring and exploiting everything that is in the CMB to be able to answer them," Calabrese said. 

Scientists are about to get a new tool to uncover some of the most elusive mysteries of our universe.

The European Space Agency's Euclid mission, which is set to launch on July 1, is designed to study the so-called "dark universe." This is how scientists refer to the more mysterious components of the cosmos, namely dark matter and dark energy. To do so, this cutting-edge mission will employ some of the principles of geometry laid down by its ancient Greek namesake, the mathematician Euclid of Alexandria.

But who exactly was Euclid, and why is he still so important?

Related: Euclid mission: ESA's hunt for dark matter and dark energy

What is the Euclid mission?

The Euclid spacecraft contains a 3.9-foot-wide (1.2 meters) telescope — half the size of the Hubble Space Telescope — that can view the universe in visible and near-infrared light. Unlike Hubble and the James Webb Space Telescope, which are designed with narrow fields of view for close-up, high-resolution work, Euclid is taking a wide-angle approach that can encapsulate thousands of distant galaxies at a time. 

Its field of view is 0.57 square degrees, which is just less than twice the diameter of the full moon. For a telescope, this is a huge expanse of sky to see in one shot, and it will allow Euclid's two instruments — its Visible Imager (VIS) and its Near-Infrared Spectrometer and Photometer (NISP) — to probe 1.5 billion distant galaxies in just six years to learn more about dark matter and dark energy. These two mysterious components make up 26.8% and 68.3% of the universe, respectively, but astronomers do not know what they are; we only know these dark elements are there because of invisible dark matter’s gravitational effect and the way dark energy is accelerating the expansion of the universe.

The density of matter and energy in the cosmos determines the geometry of the universe, in the sense that matter and energy can warp space-time, or stretch it. Since dark matter and dark energy make up the vast majority of matter and energy in the universe, it is they that truly control the universe’s geometry.

Euclid will study these dark influences in two ways. One is to look at how galaxies cluster by conducting a survey that catalogs galaxy redshifts to create a three-dimensional map of galaxies stretching across 10 billion light-years. How galaxies are clustered relates back to fluctuations in the density of matter in the cosmic microwave background (CMB), radiation emitted just 279,000 years after the Big Bang that created the universe. Comparing those fluctuations — called baryonic acoustic oscillations (BAOs) — with the size of clusters at later epochs can tell us about how the strength of dark energy has changed over time, because its repulsive force works against the gravity that causes galaxies to cluster.

The other way in which Euclid will study the dark universe is by looking at the shapes of galaxies. The gravity from dark matter spread across the universe can create gravitational lenses that bend light. We see this in dramatic fashion in the strong gravitational lenses of galaxy clusters, but dark matter can also cause "weak lensing" that subtly distorts the shapes of galaxies by altering the geometry of space and the path that light takes to reach us. Euclid will image 1.5 billion galaxies and look for those shape distortions to allow astronomers to map dark matter in the universe.

Who was Euclid the mathematician?

The mission is named after the father of geometry, the ancient Greek mathematician Euclid. (That’s his anglicized name, his Greek name was Eukleides). He lived around the year 300 BCE in the city of Alexandria, which was founded by Alexander the Great in 330 BCE. No one is entirely sure of Euclid’s personal details, including when exactly he was born and died. What we do know are what he left us: his great works of mathematics, particularly "Elements," a treatise on geometry and one of the most widely translated books in the world.

As such, Euclid has become known as the "father of geometry." Much of what Euclid the space mission will do relies on geometry, and how gravitational lensing and cosmic expansion alters that geometry.

In particular, we call Euclid's particular brand of geometry "Euclidean geometry." It's the geometry that you're taught in school, of flat planes, parallel lines, right angles, trigonometry and the Pythagorean Theorem. 

Euclid based his geometry on a foundation of five axioms, or accepted truths. These include the fact that any two points can be joined by a straight line; straight lines can be extended indefinitely; a circle can be drawn by simply knowing where its centre is and the size of its radius; that all right angles (90 degrees) are equal; and that if a straight line X intersects two other straight lines, Y and Z, and if the angles X makes with Y and Z respectively are less than 90 degrees, then Y and Z will cross each other if extended indefinitely (in other words, forming a triangle).

From this foundation, Euclid was able to formulate a geometrical system that we still use 2,300 years later in everyday life. However, astronomers are able to look for deviations from Euclidean geometry in space, such as in gravitational lenses, to search for evidence of the dark universe. 

Euclid of Alexandria's legacy will live on forever. He was a genius of his time, dabbling also in perspective geometry, algebra and so-called "spherical astronomy," which involves a form of geometry for finding objects on the celestial sphere. There's some evidence suggesting that Euclid was a student of Plato and taught at Alexandria's Museum, which was home to the famous Library of Alexandria and where he also set up a famed school of mathematics. 

Now, over two millennia later, his legacy will enter the final frontier in our best attempt yet to get to the bottom of some of the most confounding mysteries of our universe.

Additional Resources

You can read more about the Euclid mission on the website of the Euclid Consortium, the collaboration of institutions and organizations behind the mission to map the dark universe. NASA also has a stake in the mission, having provided the infrared detectors and being involved in the analysis of the data that Euclid will collect.

Bibliography

— European Space Agency, The Euclid Consortium, Partnerships and Euclid Flagship Mockup Galaxy Catalog: https://www.eoportal.org/satellite-missions/euclid#the-euclid-consortium-partnerships-and-euclid-flagship-mockup-galaxy-catalog

— University of St Andrews, Euclid of Alexandria: https://mathshistory.st-andrews.ac.uk/Biographies/Euclid/

— Mark Cropper et al, VIS: The Visible Imager for Euclid: https://arxiv.org/pdf/1608.08603.pdf

—European Space Agency, Euclid VIS Instrument: https://sci.esa.int/web/euclid/-/euclid-vis-instrument

— European Space Agency, Euclid NISP Instrument: https://sci.esa.int/web/euclid/-/euclid-nisp-instrument

— Chris North, University of Cardiff, the Planck Satellite: Cosmic Microwave Background: https://plancksatellite.org.uk/results/cosmic-microwave-background/

— University of Geneva, Euclid in a Nutshell: Looking Through the Universe: https://www.isdc.unige.ch/euclid/

— European Space Agency: What Are Baryonic Acoustic Oscillations? https://sci.esa.int/web/euclid/-/what-are-baryonic-acoustic-oscillations-

— European Space Agency: What is Gravitational Lensing https://sci.esa.int/web/euclid/-/what-is-gravitational-lensing

— Bartel Leendert van der Waerden and Christian Marinus Taisbak, Encyclopaedia Britannica, Euclid: https://www.britannica.com/biography/Euclid-Greek-mathematician

— Benjamin Wardhaugh, Princeton University: Who Was Euclid https://press.princeton.edu/ideas/who-was-euclid

— J. L. Heiberg, Richard Fitzpatrick, Euclid’s Elements of Geometry: https://farside.ph.utexas.edu/books/Euclid/Elements.pdf

— John D. Norton, University of Pittsburgh: Euclidean Geometry: The First Great Science: https://sites.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/non_Euclid_Euclid/index.html

— Norman Swartz, Simon Fraser University: Axioms and Postulates of Euclid: https://www.sfu.ca/~swartz/euclid.htm

— Mostafa El-Abbadi, Encyclopaedia Britannica: Library of Alexandria: https://www.britannica.com/topic/Library-of-Alexandria

You may have wondered: Why didn't the universe collapse into a black hole during the earliest moments of the Big Bang? Simply put, because that's not how you make a black hole.

If you want to make a black hole yourself, it's relatively straightforward: You just take any object and squeeze it as hard as possible. If you can resist all of the other forces and squeeze any amount of matter below a certain critical threshold, then gravity will take over and do the rest of the work for you, crunching that matter down into an infinitely small point and creating a black hole.

That threshold, known as the Schwarzschild radius, depends on the amount of matter you want to squeeze. If you were to take a human body and squeeze it down to the size of roughly an atomic nucleus, you would end up with a human-mass black hole the width of an atomic nucleus. If you were to repeat the process with our planet, you would end up with an Earth-mass but bean-sized black hole.

Related: What happens at the center of a black hole?

Nature makes black holes all the time through the deaths of massive stars. When they run out of fuel, their own gravitational attraction pulls as much material as possible into as small a volume as possible, eventually overwhelming any other force of nature and creating black holes a few miles across with the mass of a few suns.

So that's the simple, one-step trick to making black holes: You take a lot of matter and squeeze it to incredibly high densities.

The early universe

But the centers of massive stars are not the only locales in the universe that have reached incredibly high densities. About 13.77 billion years ago, our entire visible universe was crammed into a volume no bigger than a peach with a temperature of over a quadrillion degrees. That's a rather high density.

So why didn't the entire universe collapse into a black hole? There are two reasons.

One, the creation of a black hole relies on not only incredibly high densities but also density differences. To make a black hole, you need a lot of material crammed into a very small volume, with nothing else surrounding it. Gravity works only on differences. If the density is the same from place to place, then there are no gravitational differences and thus no chance to trigger the formation of a black hole.

Yes, the early universe was incredibly dense. But it was dense everywhere, with barely any differences. Without those differences, black holes couldn't form, because there was no difference in gravity that could lead to the sudden collapse of matter.

A dynamic universe

But even without density differences, what about the entire universe recollapsing into the singularity that birthed the Big Bang itself? Just to be clear, that wouldn't make the universe turn into a black hole. A black hole is an ultradense collection of matter within space. When we're talking about the expansion or contraction of the universe, we're talking about the evolution of space itself. 

But even if it wasn't a black hole, what prevented the collapse into a singularity? What prevented it is that the early universe wasn't static — it was dynamic. It was evolving. It was changing. And most importantly, it was expanding.

The rules of black hole formation simply don't apply in an expanding universe. It's no longer like a star sitting in the middle of empty space, imploding on itself. To collapse into a singularity, it's not enough to have a ton of mass sitting around. You need an overwhelming amount of mass to counteract the natural expansion of the universe and force it to collapse.

And there simply wasn't enough mass in the universe to do that — back then and even now. For decades, cosmologists wondered if there might be enough matter in the universe to cause the present-day expansion to slow down, stop and reverse, eventually leading to a "big crunch" and a return to a singularity.

But multiple measurements have confirmed that there isn't enough stuff to get the job done. Our universe will, as far as we can tell, continue expanding well into the future. Which is a good thing for us — life as we know it doesn't tend to do well inside black holes.

Dark energy, the mysterious entity that dominates the energy of the cosmos and appears to be accelerating the expansion of the universe, presents a cosmic conundrum for scientists. 

In short, cosmologists have no idea what dark energy really is. So they are concocting all sorts of possible models, and exploring the observational consequences of those models, in hopes of finding some clue as to what dark energy is and how it works.

Now, new research suggests that we may have already found evidence of an evolving, dynamic kind of dark energy, in the form of the radiation emitted when the first stars appeared in the universe.

Billions of years ago, the universe was much darker than it is today. It took time for the first stars and galaxies to coalesce and appear, and when they did, they completely transformed the cosmos.

Related: The history of the universe from Big Bang to now in 10 steps

Prior to the formation of the first stars, the universe was dominated by a thin fog of neutral hydrogen and helium gas. That gas had formed during the momentous epoch known as recombination, a stage that occurred when our universe was 380,000 years old and had cooled to the point where the hot plasma could become neutral — when electrons could finally bind to nuclei to form the first atoms.

When the first stars ignited, however, their intense radiation ripped through the neutral gas, turning it back into a plasma state. And so cosmologists named the appearance of the first stars the "Cosmic Dawn" and the subsequent dramatic phase change of the universe the "Epoch of Reionization." These events occurred around a few hundred million years after the Big Bang.

We do not yet have any direct measurements or maps of the cosmological epoch when the first stars and galaxies formed, or of the Epoch of Reionization. The main challenge is that these events occurred an extremely long time ago, so the light from those first stars is incredibly weak.

An open window

But there is another window into the Epoch of Reionization. Neutral hydrogen emits radiation at an extremely specific wavelength: 21 centimeters (8.3 inches). This is not a strong signal at all, but there was a whole lot of neutral hydrogen back in the day. But that radiation was emitted billions of years ago, and in the intervening ages, the universe has expanded to be about 10 times its previous size. That expansion has stretched the wavelength of that 21-cm radiation, and today, it's now detectable in radio wavelengths.

In 2018, a team of astronomers claimed to have detected the 21-cm signal emitted when the universe was only 230 million years old. But the signal from that radiation was more than twice as strong as theoretical calculations had suggested. Assuming that the observation is valid (which is still a matter of debate, as the result has yet to be replicated by another team), it suggests that something in our understanding of early cosmic history is off.

Most recently, Lu Yin, an astrophysicist at the Asia Pacific Center for Theoretical Physics in South Korea, has suggested a new possibility to explain the strange result.

Dynamics in the dark

Yin's work, published to the preprint database arXiv, explored a model called interacting Chevallier-Polarski-Linder dark energy, or ICPL. In this model, dark energy is not a fixed constant of the cosmos but a dynamical entity that can change and evolve in time, resulting in changes in the acceleration rate of expansion. But that ability to evolve immediately opens up a question: What controls the way dark energy can change? In response, this model allows for dark energy to interact with dark matter; their behavior is linked, keeping both of them in check as the universe expands.

There are more cosmological observations than the 21-cm signal. So, to start, Yin tuned the ICPL model to fit other observations, especially ones focusing on the recent expansion history of the universe. With a tuned model in hand, Yin then simulated the evolution of the early universe. Yin found that this ICPL model caused stars and galaxies to appear earlier than in standard cosmological models, which made the ICPL model better at accounting for the strange observed 21-cm signal compared with traditional cosmological models.

This is an intriguing result, but not a slam dunk. The 21-cm observations are still in dispute, and there are other possible explanations for the strange signal. Still, this shows how scientists can approach observations like this and continue to push into the frontiers of understanding dark energy and dark matter.

Stephen Hawking's most famous theory about black holes has just been given a sinister update — one that proclaims that everything in the universe is doomed to evaporate.

In 1974, Hawking proposed that black holes eventually evaporate by losing what's now known as Hawking radiation — a gradual draining of energy in the form of light particles that spring up around black holes' immensely powerful gravitational fields. Now, a new update to the theory has suggested that Hawking radiation isn't just created by stealing energy from black holes, but from all objects with enough mass.

If the theory is true, it means that everything in the universe will eventually disappear, its energy slowly bled from it in the form of light. 

Related: Lab-grown black hole may prove Stephen Hawking's most challenging theory right

"That means that objects without an event horizon [the gravitational point of no return beyond which nothing, not even light, can escape a black hole], such as the remnants of dead stars and other large objects in the universe, also have this sort of radiation," lead author Heino Falcke, a professor of astrophysics at Radboud University in the Netherlands, said in a statement. "And, after a very long period, that would lead to everything in the universe eventually evaporating, just like black holes. This changes not only our understanding of Hawking radiation but also our view of the universe and its future."

The researchers published their findings June 2 in the journal Physical Review Letters.

Space-time monsters

According to quantum field theory, there is no such thing as an empty vacuum. Space is instead teeming with tiny vibrations that, if imbued with enough energy, randomly burst into virtual particles, producing very-low-energy packets of light, or photons.

In a landmark paper published in 1974, Hawking famously predicted that the extreme gravitational force felt at the mouths of black holes — their event horizons — would summon photons into existence in this way. Gravity, according to Einstein's theory of general relativity, distorts space-time, so that quantum fields get more warped the closer they get to the immense gravitational tug of a black hole's singularity.

Because of the uncertainty and weirdness of quantum mechanics, Hawking said this warping creates uneven pockets of differently moving time and subsequent spikes of energy across the field. These energy mismatches make photons appear in the contorted space around black holes, siphoning energy from the black hole's field so they can burst into existence. If the particles then escape the black hole, this energy theft led Hawking to conclude that — over a vast timescale much longer than the current age of the universe — black holes would eventually lose all of their energy and disappear completely.

But if a gravitational field is all that's needed to produce quantum fluctuations and photons, what's stopping any object with a space-time warping mass from creating Hawking radiation? Does Hawking radiation need the special condition of a black hole's event horizon, or can it be produced anywhere in space? To probe these questions, the authors of the new study analyzed Hawking radiation through the lens of a long-predicted process called the Schwinger effect, in which matter can theoretically be generated from the powerful distortions caused by an electromagnetic field.

Sure enough, by applying the framework of the Schwinger effect to Hawking's theory, the theoretical physicists produced a mathematical model that reproduced Hawking radiation in spaces experiencing a range of gravitational field strengths. According to their new theory, an event horizon isn't necessary for energy to slowly leak from a massive object in the form of light; the object's gravitational field is good enough on its own.

"We show that far beyond a black hole the curvature of space-time plays a big role in creating radiation," second author Walter van Suijlekom, a professor of mathematics at Radboud University, said in the statement. "The particles are already separated there [beyond the black hole] by the tidal forces of the gravitational field."

What the researchers' theory means in reality isn't clear. Possibly, as the matter that makes up stars, neutron stars, and planets ages, it will eventually undergo an energy transition into a completely new ultralow energy state. This might be enough to eventually collapse all matter into black holes, which could continue to slowly drip out light until they too disappear without a trace.

Unfortunately (or fortunately, depending on any misgivings you may have about evaporating), all of this is just speculation awaiting confirmation. To figure out if it's a true prediction of our universe's eventual fate, physicists will need to spot some Hawking radiation being produced around gravitationally dense objects — both around black holes and planets, stars, or neutron stars. If everything is destined to disappear in a flash of cool light, there should be plenty of places to look.

Astronomers have detected the oldest known examples of complex organic molecules in the universe, a new study reports.

These chemicals — much like ones found in smoke and soot on Earth — reside within an early galaxy that formed when the universe was about 10% of its current age, according to the study.

The carbon-based molecules, technically known as polycyclic aromatic hydrocarbons, are found in oil and coal deposits on Earth, as well as in smog.

"The molecules we found aren't simple things like water or carbon dioxide," study lead author Justin Spilker, an astronomer at Texas A&M University in College Station, told Space.com. "We're talking about big, floppy molecules with dozens or hundreds of atoms in them."

Related: Our expanding universe: Age, history and other facts

These complex organic molecules are common in space, where they are often linked to tiny dust grains. Astronomers investigate them because they can help reveal key details of activity within galaxies — for instance, they help influence the rate at which interstellar gas cools. However, detecting these molecules in very distant galaxies that formed when the universe was relatively young has been challenging, because telescopes were limited in their sensitivity and the number of wavelengths of light they monitored.

Now, using NASA's extraordinarily powerful new James Webb Space Telescope (JWST), Spilker and his colleagues have detected these molecules in a galaxy known as SPT0418-47 more than 12 billion light-years from Earth. 

"It's remarkable that the universe can make really large, complex molecules very quickly after the Big Bang," Spilker said.

Given the extreme distance of SPT0418-47, the light the astronomers detected began its journey less than 1.5 billion years after the Big Bang. (The universe is currently about 13.8 billion years old.)

"This pushes back the old record for detections like this by about an extra billion years," Spilker said.

The discovery was made with the help of a warp in the fabric of space-time known as a gravitational lens. Albert Einstein discovered that mass distorts space-time, a bit like how a bowling ball might stretch a rubber sheet it was resting on. The greater the mass of an object, the more space-time curves around the item, and so the stronger the object's gravitational pull is. The way in which gravity behaves means that it can bend light like a lens, so a powerful gravitational field, such as that produced by a massive cluster of galaxies, can act like a giant magnifying glass.

Astronomers detected the previous record-holder for the oldest complex organic molecules using more than a full-day's worth of observations by NASA's Spitzer Space Telescope, Spilker said. In comparison, using JWST, "we only stared at this galaxy for a grand total of one hour," he said. "Webb really makes looking for organic molecules look too easy."

Related: 12 amazing James Webb Space Telescope discoveries

In addition, whereas previous efforts to detect complex organic molecules in ancient galaxies could only tell if the chemicals were there or not, "Webb's resolution lets us see actual details of where within a galaxy the molecules are located instead of just whether or not they are there at all," Spilker said. In SPT0418-47, the presence of these molecules is not uniform across the galaxy, the reason for which remains to be explained.

All in all, these new findings suggest that "it's possible for galaxies to form in overdrive," Spilker said. "The galaxy we studied is already just as massive, and its stars have formed just as much carbon and oxygen, as our own Milky Way, even though it's only a tenth the age. It's like a third grader who's already lived an entire career — gone to college, accomplished a career's worth of work, and then retired at age eight. The new results from Webb imply that it's not actually very difficult for galaxies to produce really complex molecules through all this rich chemistry going on in space."

In addition, scientists had previously thought these complex organic molecules were linked with star formation. However, the new data revealed this might not always prove true — Spilker and his colleagues found lots of regions with these molecules but no star formation, and others with new stars forming but none of these molecules, he said.

"Finding these big, complex molecules in galaxies when the universe was very young is one of those things that a lot of astronomers were hoping and expecting Webb to do, and I hope that the lessons we learned from this first attempt can help all of us as we move forward," Spilker said. "I'm eager to push to even more distant, younger galaxies — can we eventually find one that just hasn't had enough time for molecules this big to form? I'd also like to understand a lot better why these molecules exist in some regions of galaxies but not others. What was special about the regions with the molecules that allowed large molecules to form rapidly?"

Spilker cautioned that the JWST mid-infrared instrument (MIRI) used to make the new findings "appears to have declining performance right now. NASA has a team of very good engineers who are currently investigating the cause of the problem. But if the performance continues to deteriorate, it may make studies like this one impossible after the next year."

The scientists detailed their findings online today (June 5) in the journal Nature.

Astronomers are spying on the Milky Way's neighbors, assessing the amount of light that escapes from them and how this is connected to each galaxy's physical properties. 

This deep investigation of our local universe could help scientists better understand the early, distant galaxies currently being observed by the James Webb Space Telescope (JWST) and the Hubble Space Telescope. 

Because galaxies in the early universe are incredibly faint and thus difficult to observe, a team of astronomers led by Jens Melinder of the University of Stockholm in Sweden set out to create a reference sample of galaxies in the neighborhood of our Milky Way. 

Related: Galaxies: Collisions, types and how they're made

In particular, Melinder and colleagues collected and collated data regarding a special wavelength of ultraviolet radiation from these local galaxies known as Lyman alpha light.

Lyman alpha light is found in the light from gas surrounding the hottest stars, which means it is found in star-forming galaxies in particular. The peak period of star formation in the universe occurred around 10 billion years ago, so Lyman alpha light is a great way of studying galaxies that existed when the universe was just four billion years old or so. (The Big Bang that created our universe occurred about 13.8 billion years ago.)

But decoding the information carried by this light can be difficult, as the path it takes to instruments like Hubble and the JWST is complex. 

Lyman alpha light takes the scenic route around the cosmos

The exact wavelength of Lyman alpha light and the direction from which it travels are factors influenced by the physical processes it encounters as it makes its way out of its source galaxy. Regions of these galaxies with differing physical conditions through which Lyman alpha light travels can change the path of individual photons that make up the light, change their wavelength and even absorb a fraction of the light.

The fact that Lyman alpha light can encounter hot regions, or dusty areas, or sectors with strongly flowing gas clouds in their source galaxy and during its journey means that, by the time it reaches us, the information it carries can be difficult to interpret.

If an accurate interpretation of this light after its complicated journey is possible, however, it can reveal substantial amounts of information about the physical properties of the galaxies from which it originates. 

To better understand these emissions and to build their Lyman Alpha Reference Sample (LARS), the team selected 45 local galaxies that are highly star-forming, observing them across the entire electromagnetic spectrum. This allowed the team to deduce how much Lyman alpha light escapes each galaxy, and how this fraction correlates with the physical properties of that galaxy.

One of the most important findings reached by the astronomers is the connection between how much gas, plasma (which is super-hot, electrically charged gas) and dust envelopes surround the galaxies they studied and the amount of Lyman alpha light that escapes them. 

"There is a clear correlation between the amount of cosmic dust a galaxy has and how much Lyman it lets out," Melinder said in a statement. "This was expected, because dust absorbs light, but now we have quantified the effect."

The scientists were also able to determine how this gas is distributed in the galaxies and how it moves through them.

The team discovered a connection between the total mass of the stars in a galaxy with the amount of Lyman alpha light that is able to escape it, though this connection is less clear than the link between gas and the escape of this light. 

What does not seem to be linked with Lyman alpha light escape in the galaxies, however, is the rate at which those galaxies are forming new stars. 

Related: The early universe was crammed with stars 10,000 times the size of our sun, new study suggests

Lyman alpha light 'shrinks' galaxies

One thing the team found that could be particularly significant is the fact that, when observed in other wavelengths of light, these galaxies suddenly look considerably larger. This is an effect that has been seen before by astronomers.

"We see the same effect in computer simulations of galaxies with calculations of how Lyman alpha travels through the gaseous clouds in interstellar space," team member Peter Laursen, a researcher at the Cosmic Dawn Center in Denmark, said in the same statement. "This confirms that we have a rather good theoretical understanding of the physics at play."

This effect is important to consider when looking at early and distant galaxies, because the light from their outskirts can be too faint to detect or can fall beyond the limits of the detectors observing them. That means the examination and the quantification of this effect as seen in LARS could help astronomers better account for it, and thus more accurately determine the size of early galaxies.

"These results will help in interpreting observations of very distant, but similar, galaxies observed with the Hubble and James Webb space telescopes," Melinder concluded. "Understanding the detailed astrophysics of this type of galaxy is crucial for developing theories of how the first galaxies formed and evolved."

The team's research was published earlier this month in the Astrophysical Journal Supplement Series.

Cosmic monsters dwell in dense star clusters born just a few hundred million years after the universe's birth, new observations by the James Webb Space Telescope (JWST) suggest.

These monsters are supermassive stars, which JWST spotted signs of in globular clusters born about 13.4 billion years ago.

Globular clusters are found in almost every galaxy; our own, the Milky Way, hosts at least 180 of them. Not only are globular clusters the most massive and most ancient of star groupings, often containing up to a million stars born together as early as 440 million years after the Big Bang, but these stars can show anomalies not found in any other stellar collections. 

Related: James Webb Space Telescope (JWST): A complete guide

For example, globular cluster stars tend to show high levels of compositional variation, despite the fact that they were born together at the same time from the same collapsing cloud of cool gas and dust. The proportion of oxygen, nitrogen, sodium and aluminum varies from one star to another in globular clusters. Explaining these so-called "abundance anomalies" has become a significant challenge for astronomers. 

One potential explanation for this mystery, suggested back in 2018, is that supermassive stars "pollute" the original gas cloud as globular clusters form. This leads to the infant stars being unevenly enriched with chemical elements as they are forming.

Now, a team of researchers has announced that JWST has spotted chemical traces suggesting that monstrous stars are indeed lurking in stellar clusters, thus providing the first observational evidence for this enrichment theory.

"Today, thanks to the data collected by the JWST, we believe we have found a first clue of the presence of these extraordinary stars," study lead author Corinne Charbonnel, an astronomy professor at the University of Geneva in Switzerland, said in a statement. 

These supermassive stars are between 5,000 and 10,000 times as massive as the sun and are as hot as 135 million degrees Fahrenheit (75 million degrees Celsius) at their cores, compared to 27 million degrees F (15 million degrees C) or so at the heart of the sun. But, despite their intimidating size and fearsome temperatures, these stellar beasts are not always easy to locate. This is because they burn through their fuel for nuclear fusion quickly and thus have short lifespans.

"Globular clusters are between 10 and 13 billion years old, whereas the maximum lifespan of superstars is two million years," team member  Mark Gieles, of the University of Barcelona, said in the same statement. "They therefore disappeared very early from the clusters that are currently observable. Only indirect traces remain." 

To spot signs of these supermassive stars, the study team turned to the infrared vision of JWST to try and catch globular clusters earlier in their existence. The powerful space telescope saw light emitted by one of the most distant and earliest galaxies found to date, GN-z11. The galaxy is located around 13.3 billion light-years away, and JWST sees it as it was when it was just a few tens of millions of years old, making it a good choice as a hunting ground for young globular clusters. 

Because chemical elements absorb and emit light at certain frequencies, the spectrum of light from cosmic sources contains "fingerprints" that point to the composition of celestial objects. The astronomers took light from GN-z11 seen by JWST and broke it down, finding two valuable pieces of information in the process. 

"It has been established that it [GN-z11] contains very high proportions of nitrogen and a very high density of stars," said study team member Daniel Schaerer, an astronomy professor at the University of Geneva. 

These facts suggest that several globular clusters are being born in GN-z11 as we see it, but also that those clusters still host active supermassive stars. This is because the strong presence of nitrogen can only be explained by the combustion of hydrogen at extremely high temperatures — temperatures that can be reached only in the cores of supermassive stars, Charbonnel said. 

The results strengthen the model of supermassive star enrichment suggested by the team to explain the strange compositions of globular clusters. The next step in this investigation will be to look at more globular clusters in distant galaxies as seen by JWST to see if the same patterns hold. 

The team's research was published this month in the journal Astronomy and Astrophysics.

A warp in the fabric of space and time that acted like a giant magnifying glass may help solve a celestial mystery about the rate of the universe's expansion, which could shed light on the ultimate fate of the universe, a new study finds.

The universe has continued expanding since it was born about 13.8 billion years ago. By analyzing the present rate of cosmic expansion, known as the Hubble constant, scientists can estimate the age of the universe and details of its fate, such as whether it will expand forever, collapse upon itself or rip apart completely.

Scientists use two primary strategies to measure the Hubble constant. One involves monitoring nearby objects whose properties researchers understand well, such as stellar explosions known as supernovas and pulsating stars called Cepheid variables, to estimate their distances. The other focuses on the cosmic microwave background (CMB), the leftover radiation from the Big Bang, examining how it has changed over time to estimate how quickly the cosmos has expanded.

Related: What is the Hubble constant?

However, this pair of methods has produced two different results for the value of the Hubble constant. Data from the CMB suggests that the universe is expanding at the rate of about 41.9 miles (67.5 kilometers) per second per megaparsec (a distance equivalent to 3.26 million light-years). In contrast, data from supernovas and Cepheids in the nearby universe suggests a rate of about 46 miles (74 km) per second per megaparsec.

This inconsistency suggests that the standard cosmological model — scientists' current understanding of the universe's structure and history — might be wrong. Resolving this controversy, known as the Hubble constant conflict, could shed light on the evolution and fate of the cosmos.

In the new study, an international research team explored another way to measure the Hubble constant. This approach depends on Einstein's model of gravity, in which mass distorts space-time, a bit like how a bowling ball might stretch a rubber sheet it was resting on. The greater the mass of an object, the more that space-time curves around the item, and so the stronger the object's gravitational pull is.

The way in which gravity behaves means that it can bend light like a lens would, so objects seen through powerful gravitational fields, such as those produced by massive clusters of galaxies, are magnified. Gravitational lensing was discovered a century ago, and today, astronomers often use these lenses to see features otherwise too distant and faint to detect with even the largest telescopes.

In the new study, the scientists investigated the distant supernova SN Refsdal located about 9.3 billion light-years away from Earth. It was named in honor of the late Norwegian astrophysicist Sjur Refsdal, a pioneer of gravitational lensing research. 

"Sjur Refsdal had proposed that a strongly lensed supernova could be used in principle to measure the cosmic expansion rate," study lead author Patrick Kelly, an astrophysicist at the University of Minnesota at the Twin Cities, told Space.com. "However, no examples of multiply imaged supernovae were known until we found the first example, SN Refsdal, in 2015."

The researchers examined five gravitationally lensed images of SN Refsdal generated by a massive cluster of galaxies located about 5 billion light-years from Earth between our planet and the exploding star. Since light can take various paths around and through a gravitational lens, these images arrive at Earth at different times.

By measuring the brightness of each gravitationally lensed image of SN Refsdal for multiple years, the scientists estimated the time delays between each image to within 1.5%. By combining those estimates with models of the galaxy cluster's mass and the strength of its gravitational lens, they were able to measure the Hubble constant.

The new findings suggest a value of about 41.4 miles (66.6 km) per second per megaparsec for the Hubble constant. This is much closer to the CMB value than the one from supernovas and Cepheids. Still, the level of uncertainty in the data means "we cannot exclude the supernovae value," Kelly said.

If the supernova and Cepheid value for the Hubble constant does turn out to be correct, scientists may have to identify shortcoming existing models of dark matter in galaxy clusters. Astronomers will have to analyze more cluster-lensed supernovas using telescopes such as the Vera C. Rubin Observatory in Chile and the James Webb Space Telescope to either support the CMB value or the supernova and Cepheid value, Kelly said.

The scientists detailed their findings online today (May 11) in the journal Science.

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Dark energy, the mysterious force apparently driving the accelerating expansion of the universe, is spread evenly through space and time, new results suggest.

The findings also better constrain how much of the universe's energy and matter content dark energy accounts for, the study team said. 

They reached their conclusions after analyzing observations of galaxy clusters made by the eROSITA X-ray instrument, which searches the entire sky over Earth for these find-to-find collections of galaxies. eROSITA is mounted on Spektr-RG, a Russian-German space telescope that launched to Earth orbit in 2019.

Related: Dark matter and dark energy: The mystery explained (infographic)

Galaxy clusters are useful for understanding dark energy because, on large scales, this odd repellant "anti-gravity" force should suppress the formation of enormous cosmic structures. That means dark energy determines how and where galaxy clusters, the largest objects in the universe, can form. 

"We can learn a great deal about the nature of dark energy by counting the number of galaxy clusters formed in the universe as a function of time," study co-author Matthias Klein, an astrophysicist at Ludwig-Maximillians-Universitat Munchen in Germany (LMU), said in a statement.

The eROSITA Final Equatorial-Depth Survey (eFEDS) found about 500 galaxy clusters, one of the largest samples of low-mass galaxy clusters discovered to date. The observed clusters cover roughly the past 10 billion years of the 13.8 billion-year-old universe's evolution.

The study team combined the eROSITA observations with optical data from the Hyper Suprime-Cam Subaru Strategic Program. This enabled the first cosmological study performed using galaxy clusters detected by eROSITA.

The results of the study were then compared to theoretical predictions, confirming that dark energy accounts for around 76% of the total energy density of the universe. The findings also suggest that this energy density is uniform in space and constant in time. 

The team's results agree well with other independent approaches to the investigation of dark energy, such as previous galaxy cluster studies as well as those using an effect of gravity on light called weak gravitational lensing. Yet, while the new findings shed more light on dark energy, this force remains a mystery that physicists are eager to get to the bottom of. 

Why is dark energy so problematic?

In the 1920s, American astronomer Edwin Hubble made observations of distant galaxies that showed they are receding from us. In addition, the farther away a galaxy lies, the quicker it's moving away, which led scientists to discover that the universe is expanding.

This was shocking enough, overturning the commonly held idea at the time that the universe existed in a stable steady state. Things got weirder in 1998, when observations of distant supernovas showed that, not only is the universe expanding, but this expansion is accelerating. 

"To explain this acceleration, we need a source, and we refer to this source as 'dark energy,' which provides a sort of 'anti-gravity' to speed up cosmic expansion," said study co-author Joe Mohr, an LMU astrophysicist.

Yet, despite knowing what dark energy does and being able to calculate that it comprises around 76% of the energy and matter in the universe, scientists still are in the dark about what it actually is, or why it started acting on the universe in its later epochs.

The effect of dark energy causing accelerating expansion in the later universe, after the initial rapid expansion of the universe as a result of the Big Bang ended, is something like applying an initial push to a child on a swing. As the child slows toward a halt, the swing starts to pick up speed again, without any further push. Not only that, but it accelerates faster and faster and reaches increasingly greater heights. 

Just like the swing analogy, the accelerating expansion of the universe tells scientists that something is missing from their picture of the cosmos. 

"Although the current errors on the dark energy constraints are still larger than we would wish, this research employs a sample from eFEDS that, after all, occupies an area less than 1% of the full sky," added Mohr. "The nature of dark energy has become the next Nobel Prize-winning problem."

The team's research was published last month in the journal Monthly Notices of the Royal Astronomical Society.

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Humans aren't the only ones who recycle. Galaxies young and old do so too, by devouring used gas from their cosmic communities to evolve across eons.

In new research, astronomers have spotted a giant nebula in a thicket of young galaxies feeding on material some of them previously spewed out. The observations, which for the first time capture such a process just three billion years after the Big Bang, add to the growing evidence that galaxies mature by trading material with their local environments.

"We think that this is a common mechanism in galaxy formation," Zheng Cai, a cosmologist at the Tsinghua University in China and a lead author of the new study, told Space.com. "With the help of the new observations, we are able to understand more [about] how massive galaxies accrete the gas and form stars."

Related: What is the Big Bang theory?

Although galaxies, no matter their size, were once believed to be like lonely islands floating in a void, research has shown that they are surrounded by enormous yet ghostly clouds of gas and dust. These are thought to be part of a giant cosmic web, also containing elusive dark matter, that connects galaxies across space, providing pristine hydrogen as fuel for galaxies and stars to form.

More recently, astronomers have found such clouds also play a key role in recycling galaxy material by helping run so-called galactic fountains. For example, massive stars that die in violent supernova explosions blast out huge amounts of heavy metals, some of which may get pushed outside galaxies and form halos of hot gas above and below their disks. 

One theory suggests that the ejected hot gas, which reaches a few thousand light-years beyond galaxy disks, cools and "rains" back into the galaxy, reigniting star formation. This theory addresses a long-standing puzzle of how galaxies — despite not having sufficient material within them — keep birthing stars across eons. Although simulations predict galaxy recycling is a very common process, astronomers find that testing those predictions is difficult because direct observations of this cosmic rain are hard to make, thanks to a myriad of galaxy orientations.

"Direct assessment of gas flows on galactic scales is a major unknown observationally, yet critical to galaxy formation," Xavier Prochaska, professor of astronomy and astrophysics at the University of California, Santa Cruz and one of the authors of the latest study, told Space.com. 

From ground-based observations using the Keck and Subaru telescopes in Hawaii, the study team imaged MAMMOTH-1, a bright nebula in a dense galaxy cluster roughly 11 billion light-years from Earth. MAMMOTH-1 was quite mysterious when the team discovered it back in 2017, but latest images show it feeding on material from its local environment via at least three streams of gas. These streams illuminate part of the cosmic web that connects galaxies with their local environments. Two streams point to a quasar — a bright celestial object powered by a supermassive black hole — whose existence in MAMMOTH-1 was only suspected so far.

The study team found the streams around the nebula to be rich in carbon, which is formed inside stars when lighter molecules like helium and hydrogen fuse to form "metals" (astronomers' term for any element heavier than helium and hydrogen). So carbon's presence in MAMMOTH-1, extending across 300,000 light-years, offers evidence of an active galactic recycling system in place, as the metal-rich gas will help trigger the birth of a new generation of stars in the growing nebula, researchers say.

"This metal-enriched gas, compared to pristine gas, can cool faster, which could make the star formation to be more efficient," Cai told Space.com.

Because light takes time to travel across space, we are seeing the MAMMOTH-1 nebula as it was 11 billion years ago. The group of galaxies it belongs to then spanned 50 million light-years, but likely collapsed as it matured, such that today it may be densely packed across just one million light-years, astronomers say. In comparison, our local cosmic neighborhood — home to a group of galaxies including the Milky Way, all of which formed from similar clumps of gas and dust — spans 10 million light-years.

Our home galaxy, the Milky Way, also hosts galactic fountains, although astronomers don't know exactly how many are sprouting from its disk.

"Our galaxy is, by and large, about as normal of a star-forming galaxy as it gets," Prochaska said. "We can observe evidence of recycling even today."

The new study was published Thursday (May 4) in the journal Science.

 Follow Sharmila Kuthunur on Twitter @Sharmilakg. Follow us on Twitter @Spacedotcom or Facebook.

Astronomers have found the chemical remains left behind by the universe's first stars after they died in massive cosmic explosions called supernovas. 

The stellar remains were discovered for the first time in distant gas clouds by astronomers using the Very Large Telescope (VLT) based in the Atacama Desert in northern Chile. 

The find could help scientists better understand the conditions of the universe shortly after the Big Bang, when the universe was just around 300,000 years old and the first stars were being born.

Related: Supernova photos: Great images of star explosions

"We detected three distant gas clouds with a chemical fingerprint matching what we expect from the first stellar explosions," study leader and Observatoire de Paris Ph.D. student Andrea Saccardi told Space.com via email. 

The new findings offer a way of indirectly studying this first generation of stars, study co-author Stefania Salvadori, an associate professor in the University of Florence's Physics and Astronomy Department, explained to Space.com via email. 

"We can use these studies to complement stellar archeology and uncover the nature of the first stars and the first supernovas," she continued.

The first generation of stars that formed 13.5 billion years ago was very different from the stellar bodies we see in the universe today. This is because they were born when the universe was filled mostly with hydrogen and helium, with only traces of heavier elements, which astronomers call "metals." As a result, these stars were rich in hydrogen and helium but were also metal-poor. 

During their lives, these stars performed nuclear fusion, taking atoms of hydrogen and helium and forging progressively heavier atomic elements. This also created the light these stars radiated and the energy that supported them against collapse under their own gravity. Once the stars ran out of fuel for nuclear fusion, the balance against outward radiation pressure and inward gravitational pressure ended, with gravity winning out. 

As a result, the stars' cores collapsed while the outer layers were blown away in massive supernova blasts. This distributed the elements forged in this first generation of stars, such as carbon, oxygen and magnesium, which are present in the outer layers of stars, into the cosmos. This material then became the building blocks of the second generation of stars.

As a result, stars descended from earlier stellar bodies are richer in heavier elements, and thus as stars are born later and later in the history of the 13.8 billion-year-old universe, they become progressively less metal-poor. Despite their tremendous power, these first supernovas were still too weak to disperse very heavy elements like iron located mainly in the cores of these first stars. 

So, when astronomers search for the chemical remains of these early stars and for second-generation stars, they look for plenty of carbon and other elements mixed with very little iron.

Related: James Webb Space Telescope spies most ancient galaxies ever observed

Finding the first stellar ashes

To discover these chemical imprints, the study team looked at the light from distant quasars, intense sources of radiation powered by feeding supermassive black holes, as it passes through gas clouds. Different elements absorb light at different wavelengths, leaving a fingerprint in the light from background quasars that can be read by astronomers to determine the composition of the cloud.

The chemical fingerprints seen in the three clouds spotted by the study team match the template for enrichment by the first supernovas. This fingerprint has, according to Saccardi, also been observed in many old stars in our Milky Way galaxy, which researchers consider to be second-generation stars that formed directly from the "ashes" of the first ones. 

"These faraway clouds in the early universe have a very low iron content but plenty of carbon and other light elements," Saccardi added. "Indeed, in the Milky Way, several ancient stars show a small iron content and a large excess of carbon and other light elements as our gas clouds."

Salvadori added that these chemical signatures from the first stars may have thus far evaded detection because the search for them has focused on dense gas clouds that could sustain star formation after the gas had been enriched by the first supernovas.

"In other words, subsequent generations of 'normal,' more metal-rich supernovas were able to further pollute these dense gas clouds, thus erasing the chemical fingerprints of the first stars," Salvadori said. "We instead analyzed the chemical composition of more diffuse gas clouds and pinpointed the fingerprints of the first stars. This success is a consequence of a tight synergy between theory and observations."

The team said that they will now attempt to better understand the nature of these gas clouds and aim to discover how prevalent they have been throughout the history of the universe.

"First of all, we have to look for other systems with the same chemical composition as those we have found," Saccardi said. "Looking into the farthest future, a significant step forward in the analysis of these faraway gas clouds will be represented by the Extremely Large Telescope (ELT). Thanks to its collecting power and its high-resolution spectrograph, ANDES, we will carry out detailed chemical investigations, resolving faint metal absorption lines and determining significant constraints on key elements."

The team's research was published on Wednesday (May 3) in The Astrophysical Journal.

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A new map of the cosmos shows the distribution of mysterious dark matter in sharp detail. 

The map, which covers a quarter of the sky over Earth and extends deep into the cosmos, was created using a "cosmic fossil" known as the cosmic microwave background (CMB), radiation left over from just after the Big Bang.

The new map, created by the Atacama Cosmology Telescope (ACT) collaboration, has helped confirm a theory of gravity pioneered by Albert Einstein over a century ago.

Related: No, the Big Bang theory is not 'broken.' Here's how we know.  

Einstein's 1915 theory of general relativity posits that objects with mass "warp" the fabric of space-time, giving rise to gravity and leading to specific predictions about how the large-scale structure of the universe formed and evolved to the state we observe today, 13.8 billion years after the Big Bang. These predictions comprise what is known as the "standard model of cosmology."

"We have used the CMB, the oldest light in the universe, emitted soon after the Big Bang, to measure how dark matter  —  the invisible stuff that makes up the majority of the matter in the universe  —  is distributed on large scales," ACT team member Adam Hincks, an astrophysicist at the University of Toronto, said in a statement. 

"The distribution agrees very well with theoretical predictions," Hincks said. "It's a really satisfying result scientifically because it shows we have a robust understanding of how our universe grows and evolves."

Using the effects of gravity to 'see' the invisible

To create the map, the scientists used data collected by the ACT, which viewed the heavens from Cerro Toco in the Chilean Atacama Desert for 15 years before it was decommissioned in 2022. The ACT observations allowed the team to study the effect that gravitational lensing, also predicted by general relativity, has on the CMB. 

Gravitational lensing arises from the fact that, when gravity warps space-time, it distorts the path of light traveling toward us. The nature of this warping can tell astronomers a lot about the distribution of the mass causing the spatial distortion.

The CMB is effectively the "first light" in the universe, as it comes from an era called the epoch of recombination and an event called "the last scattering." When the universe was an infant, it was filled with a sea of electrons, gluons and quarks. Electrons endlessly scattered photons, particles of light, which meant that light couldn't travel through the cosmos. As a result, the universe was opaque, like a brick.

As the universe cooled, particles could start to stick together. Quarks and gluons formed protons and neutrons, and these bonded with electrons to create the first atoms, around 380,000 years after the Big Bang. With fewer free electrons around, photons could travel unimpeded, and the universe became transparent, like a window.

The CMB is this first freely traveling light. Thanks to the continuing expansion of the universe, this ancient radiation fills the cosmos almost uniformly, with the occasional tiny variation.  

The ACT scientists looked at the effect the gravity of the large structure of the universe has on the CMB as the result of gravitational lensing, providing them with a great way of mapping ordinary matter and, especially, dark matter, which makes up about 85% of the material universe but remains mysterious.

Dark matter doesn't interact with light like the "normal" stuff that comprises stars, planets and us, meaning that astronomers can't see it in any wavelength of electromagnetic radiation. But dark matter does have mass and thus it does interact gravitationally. That means that its presence can be inferred as a result of its gravitational interactions with matter and radiation.

Crucially, it also means that dark matter has a gravitational lensing effect, especially when it is in large concentrations like the halos that are theorized to surround most, if not all, galaxies. This lensing effect can be seen in the distortion of the CMB.

This distortion allowed the team to create a highly detailed cosmic map of the distribution of both ordinary matter and dark matter, revealing that the stuff takes the shape predicted by general relativity and the standard model of cosmology that emerged from it.

Related: What is dark matter?

Dark matter is just lumpy enough

The matter distribution map could also help settle a problem in cosmology that emerges from measurements of light from distant stars, which suggest that dark matter isn't as "lumpy" as it should be, according to the standard model of cosmology. 

The ACT map suggests that the vast clumps of dark matter observed are just the right size to fit in with the standard model of cosmology. The ACT team said that means that the new findings fit the overall picture scientists have about the evolution of the cosmos. 

At the same time, the more accurate measurements that comprise the ACT map should allow researchers to scrutinize that picture on an entirely new and deeper level. This could help finally nail down where discrepancies in different dark matter mapping techniques are coming from, team members said. 

"In cosmology, as in all of science, having independent measurements that test the same theoretical model is really important," Hincks said. "The fact that we can successfully explain how our cosmos works with this level of precision is amazing."

The collaboration's research is discussed in three papers soon to be published in the Astrophysical Journal, which are currently available on the Atacama Cosmology Telescope website.

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NASA's James Webb Space Telescope (JWST) has turned its sharp eyes on a distant patch of sky made famous by its predecessor.

A newly released JWST photo captures the Hubble Ultra Deep Field (HUDF), a faraway region in the southern constellation Fornax (the Furnace). The HUDF has long been "an extremely fertile hunting ground" for astronomers, as it contains at least 10,000 galaxies dating back to just 800 million years after the Big Bang, providing a glimpse into how the very first galaxies may have formed.

When NASA's Hubble Space Telescope observed this pocket of the universe in late 2003, it clicked the first images of galaxies at the farthest distances ever known. At the time, Hubble's representatives said this record is "unlikely to be surpassed" until Webb comes onto the stage.

Related: James Webb Space Telescope: Everything you need to know

Two decades later, Webb observed the same region at similar depths that Hubble did — which means Webb could see galaxies as faint as its precursor — "in just one-tenth as much observing time," NASA representatives wrote in an image description published on Wednesday (April 13).

While Hubble took 11.3 days to click the image, Webb one-upped the record in just a little over 20 hours. The latest image is also unveiling young galaxies that were not seen previously, astronomers said.

"The fact that we see hot, ionized gas is telling us exactly where stars are being born in these galaxies," Michael Maseda, an astronomy professor at the University of Wisconsin-Madison, said in a statement. "Now we can separate those areas from where stars already existed. That piece of information is very important because, billions of years later, we don't exactly know how galaxies became how they are today."

The image, which was snapped in infrared wavelengths by JWST's powerful Near-Infrared Camera (NIRCam) instrument, is helping astronomers piece together the universe's history in the first billion years after the Big Bang. This period, which is when the first cohort of stars were born, is called the reionization era. 

Galaxies this early on were not as well defined as the ones we see closer to our Milky Way, which itself is a fine-tuned spiral galaxy. In this early slice of the universe, astronomers have previously spotted one galaxy shaped like a toothpick and another like a bracelet link. What will Webb's image end up revealing?

Follow Sharmila Kuthunur on Twitter @Sharmilakg. Follow us on Twitter @Spacedotcom and on Facebook. 

The most accurate observation to date of distant stars that periodically change in brightness may spark a rethink of the rate at which the universe expands — perhaps by settling a longstanding problem in cosmology, or deepening it.

The observation confirms a disparity that exists between the two major methods of measuring how fast the universe is expanding, conforming with one but not the other, a new study reports. 

Researchers with the Stellar Standard Candles and Distances group used data collected by Europe's Gaia spacecraft to study Cepheid variable stars, which pulsate in a regular manner, providing a way of accurately measuring cosmic distances. The Cepheid star measurement technique expands on other methods, such as one that relies on observations of Type 1a supernovas. 

Related: Hubble telescope refines universe expansion rate mystery

The light output of supernovas, mammoth explosions that occur at the end of big stars' lives, is so uniform they are referred to as "standard candles" and form an important part of what astronomers call the "cosmic distance ladder." The Cepheid star distance measurement method adds another "rung" to that metaphorical ladder, and this new research has strengthened that rung.

"We developed a method that searched for Cepheids belonging to star clusters made up of several hundreds of stars by testing whether stars are moving together through the Milky Way," study co-author Richard Anderson, a physicist at the École Polytechnique Fédérale de Lausanne (EPFL) in Switzerland, said in a statement. 

"Thanks to this trick, we could take advantage of the best knowledge of Gaia's parallax measurements while benefiting from the gain in precision provided by the many cluster member stars," Anderson said. "This has allowed us to push the accuracy of Gaia parallaxes to their limit and provides the firmest basis on which the distance ladder can be rested."

The cosmic distance ladder is also used to measure the expansion rate of the universe, known as the Hubble constant. This new recalibration of the Cepheid "rung" deepens a problem with the rate at which the universe expands, which has come to be known as the "Hubble tension."

What is the Hubble tension?

In the early 20th century, shockwaves rippled through physics and astronomy when Edwin Hubble uncovered evidence that the universe is not static, as was believed at the time, but is actually expanding. This rate of expansion therefore became known as the Hubble constant. 

This concept underwent a major shakeup in the late 1990s, when astronomers discovered via the observation of distant supernovas that, not only is the universe expanding, but it is doing so at an accelerating rate. Since then, measuring the Hubble constant has become a thorny issue for astronomers and cosmologists, because there are two major ways of determining this value — and they don't agree. 

One method uses galaxies' velocities as a function of distance to deliver a Hubble constant value of about 73 ± 1 kilometers per second per megaparsec (km/s/Mpc), with 1 Megaparsec representing around 3.26 million light-years. This is known as the "late time" solution, because it comes from measurements of the universe in recent times.

The other method of measuring the Hubble constant looks at the light from an event shortly after the Big Bang called "the last scattering," in which electrons combined with protons to form the first atoms. As free electrons had previously scattered photons (particles of light) dramatically, preventing them from traveling very far, this event meant that light was suddenly allowed to travel through the cosmos freely.

This "first light" is now seen as the cosmic microwave background (CMB), and it almost uniformly fills the cosmos, barring tiny variations. When astronomers measure these tiny variations in this fossil radiation, it predicts a modern-day value for the Hubble constant of around 67.5 ± 0.5 km/s/Mpc.

The differences between the two estimations of the Hubble constant have strangely only grown as measuring techniques for both have been refined and have become more precise. This 5.6 km/s/Mpc difference, and the general trouble surrounding it, is referred to as the "Hubble tension." It's a serious issue for cosmologists, as it suggests there is something wrong with our understanding of the basic physical laws that govern the universe.

Related: The universe is expanding so fast we might need new physics to explain it

Cepheid variables pick a side

Anderson explained why a difference of just a few km/s/Mpc in the Hubble constant matters, even given the vast scale of the universe. (The width of the observable cosmos alone is estimated to be around 29,000 MPC.)

"This discrepancy has a huge significance," Anderson said. "Suppose you wanted to build a tunnel by digging into two opposite sides of a mountain. If you've understood the type of rock correctly and if your calculations are correct, then the two holes you're digging will meet in the center. But if they don't, that means you've made a mistake  —  either your calculations are wrong or you're wrong about the type of rock."

Anderson said that is analogous to the Hubble tension and what's going on with the Hubble constant. 

"The more confirmation we get that our calculations are accurate, the more we can conclude that the discrepancy means our understanding of the universe is mistaken, that the universe isn't quite as we thought," he added. 

The improved calibration of the Cepheid variable measurement tool means that this technique finally "takes a side" in the Hubble tension debate, providing agreement with the "late time" solution.

"Our study confirms the 73 km/s/Mpc expansion rate, but more importantly, it also provides the most precise, reliable calibrations of Cepheids as tools to measure distances to date," Anderson said. "It means we have to rethink the basic concepts that form the foundation of our overall understanding of physics."

The team's results have other implications as well. For example, the more accurate Cepheid calibration also helps to better reveal the shape of our galaxy, study team members said. 

"Because our measurements are so precise, they give us insight into the geometry of the Milky Way," study lead author Mauricio Cruz Reyes, a Ph.D. student in Anderson's research group, said in the same statement. "The highly accurate calibration we developed will let us better determine the Milky Way's size and shape as a flat-disk galaxy and its distance from other galaxies, for example."

The new study was published last week in the journal Astronomy & Astrophysics.

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The James Webb Space Telescope (JWST) has clapped eyes on the most ancient galaxies ever observed. 

Astronomers are now confident that the light from these galaxies has been traveling to Earth for over 13.4 billion years, two new studies report. The results show that these galaxies inhabited the universe when it was less than 350 million years old and demonstrate the rapid emergence of the first generations of galaxies.

"It was crucial to prove that these galaxies do, indeed, inhabit the early universe. It's very possible for closer galaxies to masquerade as very distant galaxies," Emma Curtis-Lake, a co-author of one of the new studies and an astronomer at the University of Hertfordshire in England, said in a statement.

"Seeing the spectrum revealed as we hoped, confirming these galaxies as being at the true edge of our view, some further away than Hubble could see! It is a tremendously exciting achievement for the mission," Curtis-Lake said.

Related: James Webb Space Telescope: Everything you need to know

The discovery confirms JWST's ability to perform one of its most important tasks — studying the early universe via light that has been traveling for so long that the expansion of the universe has stretched its wavelength. This stretching of light is called redshift; the longer the light travels, the further toward the red end of the electromagnetic spectrum the expansion of the universe shifts its light. This means that redshift can be used as a measure of distance, and that early galaxies should have light displaying extreme redshifts, with their light stretched all the way into the infrared range — JWST's specialty.

Thus far, the $10 billion observatory has identified several extremely high-redshift candidate galaxies, but these observations have to be confirmed using spectroscopy. 

Spectroscopy can be used to make the distinction between early galaxies and closer, more contemporary galaxies that might share similar properties, because spectroscopy can spot the characteristic fingerprints of specific elements. Early galaxies are composed of mostly hydrogen and helium, lacking heavier elements like oxygen, nitrogen and carbon. This is because they have not yet been enriched by the heavy elements forged by stars via nuclear fusion and then dispersed when these stars die and go supernova.

The researchers' analysis of data collected from JWST's near-infrared camera (NIRCam) and Near-Infrared Spectrograph (NIRSpec) instrument allowed them to determine that the four galaxies designated JADES-GS-z10–0, JADES-GS-z11–0, JADES-GS-z12–0, and JADES-GS-z13–0 do indeed have extreme redshifts, of 10.3 to 13.2. (JADES, by the way, stands for "JWST Advanced Deep Extragalactic Survey.")

They came to this conclusion because the spectra from these galaxies lack the telltale signature of heavy elements like carbon, meaning JWST is seeing them as they were when the universe was just 300 to 500 million years old. (The universe is currently about 13.8 billion years old.)

"For the first time, we have discovered galaxies only 350 million years after the Big Bang, and we can be absolutely confident of their fantastic distances," co-author and NIRCam science team member Brant Robertson said in the statement. "To find these early galaxies in such stunningly beautiful images is a special experience."

The observations come from the first round of JADES observations, which were directed toward a tiny area of the sky known as the Ultra Deep Field that has been investigated for around two decades by the Hubble Space Telescope. This patch of sky contains around 100,000 galaxies, each caught at some moment in its history, potentially billions of years in the past. 

The researchers used over 10 days of JWST mission time to study the Ultra Deep Field with NIRCam, observing it in nine different infrared colors. This was followed by 28 hours of data collection conducted by the NIRSpec instrument over three days. JWST therefore delivered exceptionally sensitive and sharp images of the region and also provided astronomers the data they needed to get a precise measurement of each galaxy's redshift and reveal the properties of the gas and stars within each one.

"These results are the culmination of why the NIRCam and NIRSpec teams joined together to execute this observing program," said NIRCam principal investigator Marcia Rieke of the University of Arizona.

The two papers were published today (April 4) in the journal Nature. The researchers first reported the results in December 2022, when they presented them at a conference.

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The universe could, in fact, be a giant doughnut, despite all of the evidence suggesting it's as flat as a pancake, new research suggests. 

Strange patterns found in echoes of the Big Bang could be explained by a universe with a more complicated shape, and astronomers have not fully tested the universe's flatness, the study finds.

Related: What shape is the universe? 

Flat surfaces

All observations so far suggest the universe is flat. In geometry, "flatness" refers to the behavior of parallel lines as they go out to infinity. Think of a tabletop: Lines that start out parallel will remain that way as they extend along the table length. 

In contrast, look at Earth. Lines of longitude begin perfectly parallel to each other at the equator but  eventually converge at the poles. The fact that parallel lines initially intersect reveals that Earth is not flat.

The same logic applies to the 3D universe. For instance, the cosmic microwave background (CMB) — light released when the cosmos was only 380,000 years old — now sits over 42 billion light-years away and features tiny fluctuations in temperature across the sky. Astronomers have calculated the predicted size of those fluctuations compared with observations. If their measured size differs from predictions, that means those rays of light, which started out parallel, changed directions over space-time, indicating that the geometry of the universe is curved.

But those same measurements have revealed that, ignoring small-scale deflections from galaxies and black holes, the overall geometry of the universe is flat.

Different types of flat

But there's more than one kind of flat. For example, draw parallel lines on a piece of paper. Then wrap one end of the paper to connect with the other, forming a cylinder. The lines remain parallel as they circle the cylinder. In the language of mathematics, any cylinder is geometrically flat but is said to have a different topology. Close up both sides of the paper, and you make a torus, or doughnut shape.

To get another example of a weirdly flat shape, wrap a thin strip of paper in a circle, but make a 180-degree twist in one end. The end result is a Möbius strip, which is still geometrically flat, because parallel lines stay parallel, even when they flip over each other.

Mathematicians have discovered 18 possible geometrically flat, 3D topologies. In each one, at least one dimension wraps up on itself, and sometimes, they flip over like a Möbius strip or make partial rotations. In such a twisty universe, if we looked far away, we would see a (maybe upside-down) copy of ourselves from a much younger age. For example, if the universe were 1 billion light-years across, astronomers would see a version of the Milky Way galaxy as it was 1 billion years ago and, behind that, another copy from 2 billion years ago, and so on.

If the universe were a giant doughnut, astronomers could look in two directions to see such copies.

The universe's shape

Astronomers have measured the topology of the universe in multiple ways, from looking for duplicates of patterns of galaxies to matching circles in the CMB. All evidence suggests the universe is both geometrically flat and has a simple unwrapped topology.

But a paper published Feb. 23 to the preprint database arXiv suggests that past measurements have been limited. Most notably, observations have assumed that the universe wraps around itself in only one dimension and does not have a more complicated topology. Also, observations of the CMB have revealed some strange, unexplained anomalies, like large patterns appearing where they shouldn't.

In fact, a universe with a complicated topology could explain at least some of the anomalies in the CMB. While this isn't an iron-clad case for complicated topologies, the researchers offered ideas for more sophisticated direct searches, like follow-up studies of the CMB.

In that case, there may be a mirror image of us somewhere in our twisty universe.

This story originally appeared on Livescience.

The early universe may have been such a violent place that space-time itself fractured like a pane of glass. Those fractures would have released floods of gravitational waves, and a team of astronomers has discovered that we may have already detected these ripples in the fabric of space-time.

The team, who reported their results recently in a paper submitted for publication in the Journal of Computational Astrophysics and published on arXiv.org, claim that they have seen evidence for so-called domain walls in the early universe.

When our universe was incredibly young, it was also incredibly exotic. The four forces of nature were bound up into a single, unified force. We do not know what that force looked like or how it operated, but we know that as the universe cooled and expanded, that unified force fractured into the four familiar forces we have today. First came gravity, then the strong nuclear force splintered off, and lastly, the electromagnetic and weak nuclear forces split from each other.

Related: The history of the universe: Big Bang to now in 10 easy steps

With each of these splittings, the universe completely remolded itself. New particles arose to replace ones that could exist only in extreme conditions previously. The fundamental quantum fields of space-time that dictate how particles and forces interact with each other reconfigured themselves. We do not know how smoothly or roughly these phase transitions took place, but it's perfectly possible that with each splitting, the universe settled into multiple identities at once.

This fracturing isn't as exotic as it sounds. It happens with all kinds of phase transitions, like water turning into ice. Different patches of water can form ice molecules with different orientations. No matter what, all the water turns into ice, but different domains can have differing molecular arrangements. Where those domains meet walls, or imperfections, fracturing will appear.

Probing the GUT

Physicists are especially interested in the so-called GUT phase transition of our universe. GUT is short for "grand unified theory," a hypothetical model of physics that merges the strong nuclear force with electromagnetism and the weak nuclear force. These theories are just beyond the reach of current experiments, so physicists and astronomers turn to the conditions of the early universe to study this important transition.

The GUT phase transition, which occurred when the universe was the barest fraction of a second old, may very well have left behind domain walls, a network of boundaries between different configurations of space-time. These defects could not have lasted long, however. If they persisted for a few seconds, or even minutes, their intense energies would have thrown off the process of nucleosynthesis, which gave rise to all of the primordial hydrogen and helium in the universe or distorted our images of the cosmic microwave background (CMB), the leftover radiation from the Big Bang.

So this interconnected set of domain walls had to decay into other particles — either normal particles, like electrons or quarks, or more exotic particles, like some form of dark matter. Either way, that decay process, coupled with the undulating motion of the domain walls themselves, would have released a flood of gravitational waves that could persist to the present-day universe.

Surveying the domain

Those gravitational waves would be incredibly weak, and impossible to detect with existing ground-based gravitational wave facilities. But for over a decade, several teams of astronomers around the world have instead been looking to pulsars to map gravitational waves sloshing through the universe.

Pulsars are incredibly precise timekeeping objects, able to maintain their rhythm down to less than a millionth of a second. If a gravitational wave passes between us and a set of pulsars, however, that will subtly affect the period of pulsation. By studying large numbers of pulsars for long periods of time, we can hope to find signals of a background frothing of gravitational waves.

These pulsar timing arrays, like the NANOGrav experiment and the European Pulsar Timing Array, have already found hints of a signal. Most astronomers believe this signal is due to the combined action of millions of supermassive black holes colliding with each other over billions of years.

But the new study presents a different picture. The team argues that the signal also could be explained by domain walls decaying in the early universe. Their models allow for the domain walls to decay fast enough to not violate other observations, like the CMB, while still providing a strong enough signal to explain the pulsar-timing-array data.

Because the signals in the data are very faint and not confirmed to come from any particular source, there's room for this kind of radical proposal. The team argues that future pulsar timing measurements should be able to distinguish their model of decaying domain walls from the traditional picture of colliding supermassive black holes. Also, if their model is accurate, the domain walls should decay into either normal or exotic particles. Either way, that should be detectable with future, much more sensitive CMB measurements.

If the result holds up, it will be a major win for physics: The first time we've discovered concrete evidence for GUT phase transitions and the beginnings of a new understanding of physics.

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Will the universe end in a bang or a whimper? A pair of theoretical physicists have proposed a third path: perhaps the universe will never end.

In a study that attempts to define the nature of dark energy — a mysterious phenomenon thought to be causing the universe to expand faster and faster every moment — the physicists find that cosmic expansion isn't always a given. 

Rather, they write, dark energy may periodically "switch" on and off, sometimes growing the cosmos, sometimes shrinking it down until the conditions are right for a new Big Bang to occur — and for a new universe to be born.

Related: What is the Big Bang Theory? 

The great escape

Our universe is currently experiencing a phase of runaway expansion: The cosmos is getting bigger faster with every passing moment. Cosmologists do not understand the cause of this acceleration, which they name dark energy. If this acceleration persists, then our universe will eventually expand into oblivion, with all matter and radiation torn apart.

This wouldn't be the first period of runaway growth. In the earliest moments of the Big Bang, the energies and densities were so extreme that existing physics cannot cope — it predicts a singularity, a point of infinite density where the math breaks down. After that, the universe experienced a period of incredibly rapid expansion known as inflation, which is also poorly understood.

Astronomers have long wondered if these two phases of accelerated expansion — one in the earliest moments of the Big Bang and one in the present epoch — are connected to each other, and whether an entity that drives both of them avoids the problem of the big bang singularity.

Dynamical demons

To answer that, a pair of theoretical physicists published a study Feb. 7 in the preprint database arXiv which examined a model of the universe where dark energy has always played a role. Previous research modeled dark energy "switching on" at various times to drive cosmic expansion, but the new research proposes a more realistic model that includes matter and radiation.

They wanted to see if dark energy can avoid a Big Bang singularity, drive inflation, and accelerate the late universe. To avoid that initial singularity, the universe can't begin from a point of infinite density. Instead, the universe we live in would have to be one in an infinite series of repeated "Big Bounces."

In this scenario, dark energy drives the universe until it reaches a certain size. But then the dark energy transforms itself, forcing the universe to contract. The cosmos then suffers a big crunch, but right before reaching a state of infinite density, dark energy turns around again, driving a period of incredibly rapid inflation and starting the cycle anew.

A finely tuned mechanism

The researchers found a model of dark energy that performed the trifecta. But crucially, matter and radiation could not be present in the extremely early universe, otherwise they spoiled inflation. Instead, matter and radiation had to appear just after inflation, as a portion of the dark energy decayed away, flooding the universe with light and matter. 

While initially successful, the researchers weren't able to find a generic class of dark energy models that could always lead to the same results. Instead, they had to artificially put in a smaller value for the present-day accelerated expansion than quantum mechanics predicts in order to get the exact right outcome.

However, this new research does point in a promising direction, providing a viable platform for further exploring models like this. Humans are not necessarily destined to live in a cold, empty cosmos, because dark energy might behave differently in the far future. Only continued research will uncover our ultimate fate. 

Originally published on LiveScience.

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The only known video interview with Belgian physicist Georges Lemaître, widely considered the "father of the Big Bang," talking about the birth of the universe has been rediscovered almost 60 years after it was lost.

Lemaître (1894-1966) was a professor of physics at the Catholic University of Louvain in Belgium and  a practicing Catholic priest. In 1927, he was the first person to propose that the movement of galaxies away from Earth was a sign that the universe was expanding, which was later observationally confirmed by the American astronomer Edwin Hubble. 

Lemaître was also the first to derive Hubble's law, which states that galaxies are moving away from Earth at speeds proportional to their distance, even though Hubble received all the credit at the time. (The International Astronomical Union renamed the idea the Hubble-Lemaître law in 2018.) In 1931, Lemaître proposed his "hypothesis of the primeval atom" to account for the universe's expansion, which stated that the universe began from a single point, and later inspired what we now know as the Big Bang theory.

The rediscovered video features Lemaître discussing his ideas with journalist Jérôme Verhaeghe during a Belgian TV interview, which was broadcast on Feb. 14, 1964. A small clip of the interview, around two minutes long, has been widely available for decades, but the full 20-minute video was considered to be lost after the film reel containing the footage disappeared shortly after the interview aired. 

But this reel, it turns out, was simply misplaced.

Related: Long-lost copy of Newton's famous book 'Opticks' to be auctioned for half a million dollars

On Dec. 29, 2022, Belgium's national service broadcaster for the country's Flemish-speaking community, Vlaamse Radio- en Televisieomroeporganisatie (VRT), rereleased the video after it was discovered in the broadcaster's archives. The film reel had been lost because it was miscategorized and because Lemaître's name was misspelled on the label, which made searching for it like "looking for a needle in a haystack," VRT representatives wrote in a translated statement. (Flemish, also known as Dutch Flemish, is one of the three official languages of Belgium; it is spoken by people living in the Flanders region in the north of the country.)

In the interview, Lemaître speaks in French, with Flemish subtitles added to the video. In a new paper, uploaded Jan. 19 to the preprint server arXiv, a team of researchers translated the interview into English to make it accessible to a wider audience. 

"To our knowledge, it is the only video interview of Georges Lemaître in existence," the researchers wrote in the paper. 

Expansive interview 

The video starts with Lemaître answering an unknown question that was likely asked by Verhaeghe during the interview's introduction. While it's unclear what these opening remarks refer to, Lemaître soon dives into how his hypothesis of the primeval atom differed from the Steady State model — the idea that the universe is always expanding but maintaining a constant average density, with no start or end — which was the preferred view of the cosmos at the time.

Lemaître talks in great length about his rival Sir Fred Hoyle, an English physicist who was one of the best-known and fierce proponents of the Steady State model but who also accidentally coined the term "Big Bang." Although he repeatedly calls out Hoyle for being wrong during the interview, Lemaître remarks that he has the "greatest admiration" for his colleague's work.

Lemaître explains that the Steady State model could work only if the hydrogen required to make stars appeared "like a ghost" from nowhere, which he argued would go against the principle of conservation of energy, the idea that energy is neither created nor destroyed, only transformed from one type to another, which he described as "basically the most secure and solid thing in physics." 

Instead, Lemaître argues in the video, the expansion could be traced back to the "disintegration of all existing matter into an atom," which created "an expanding space filled by a plasma" via a "process that we can vaguely imagine."

Related: How was the universe created?

Lemaître also discusses the work and ideas of several renowned academics, including French mathematician Élie Cartan, English astrophysicist Edward Arthur Milne, and Sir James Hopwood Jeans, an English physicist, astronomer and mathematician who was another champion of the Steady State model. 

During the interview, Lemaître notes that detecting cosmic rays — high-energy particles or particle clusters that move through space at nearly the speed of light, which Lemaître poetically described as "rays of the primeval fireworks" — would play an important role in proving his theory. (Lemaître died shortly after learning about the discovery of cosmic microwave background radiation, which occurred two years after the interview and was the first major piece of evidence that he was correct.)

The priest-turned-physicist was also asked whether his theories contradicted his religious views, but he explained that his research involved no "religious ulterior motive" and that "the beginning [of the universe] is so unimaginable" and "so different from the present state of the world" that he saw no reason why it disproved God's involvement in creation. 

The researchers who translated the French transcript to English are pleased to have played a role in making Lemaître's only filmed interview more accessible to the astronomical community and the public.

"Of all the people who came up with the framework of cosmology that we're working with now, there's very few recordings of how they talked about their work," lead study author Satya Gontcho A Gontcho, a physicist at the Department of Energy's Lawrence Berkeley National Laboratory in California, said in a statement. "To hear the turns of phrase and how things were discussed … It feels like peeking through time."

Originally published on LiveScience.com

The James Webb Space Telescope, not even finished with its first full year of observations, has delivered some real stunners. But amid the breathtaking images and unprecedented findings, there was a puzzling claim: that the telescope had detected galaxies in the incredibly young universe. Those galaxies were so massive and appeared so early that they, the headlines claimed, "broke" the Big Bang model of cosmology. 

The claim went viral, but as with many things on the internet, it's simply not true.

Now, there's more research to back up the Big Bang. Recently, researchers took a more careful look at the data and determined that the distant galaxies discovered by the James Webb Space Telescope are, indeed, perfectly compatible with our modern understanding of cosmology.

Related: The James Webb Space Telescope never disproved the Big Bang. Here's how that falsehood spread.

The potential problem with distant galaxies isn't that they exist. In fact, the modern formulation of the Big Bang theory, called ΛCDM cosmology (the Λ stands for dark energy, and CDM is short for "cold dark matter"), predicts galaxies to appear in the very young universe. That's because billions of years ago, there were no galaxies, or even stars, at all. When our universe was much smaller and much denser than it is today, everything was much more uniform, with only tiny density differences appearing here and there randomly.

But over time, those density differences grew, with the slightly denser pockets pulling more material onto them. Over hundreds of millions of years, those pockets formed into the first stars, and eventually grew to become the first galaxies.

In fact, one of the main goals of the Webb telescope was to discover and characterize those first galaxies, so finding galaxies in the incredibly young universe is a point in favor of the Big Bang theory, not against it.

So what's the conflict, then? The apparent tension came about because of the estimated masses of those galaxies. Several were quite large — well over 10^10 solar masses. That is still much smaller than the Milky Way, but for the early universe, they are quite gigantic. 

The researchers who discovered these galaxies estimated that their large masses put them in tension with many models of galactic formation and evolution. At the extreme end, the researchers claimed that it might even be possible for no galaxy formation model within the ΛCDM framework to create such large galaxies so quickly.

A matter of some debate

But those claims hinged on measuring a precise distance to those galaxies — an incredibly difficult task at these extreme distances. For the record-breaking galaxies that could be tension with cosmological models, the researchers relied on something called a photometric redshift, which fits a rough light spectrum of a galaxy to a model to estimate a distance.

That method is notoriously unreliable, with simple effects — like excess dust surrounding the galaxies — making them appear more distant than they really are.

To accurately judge if the Big Bang is in trouble, a new team of researchers used Webb to identify galaxies with a much more precise and reliable method of determining distance, known as spectroscopic redshift. This technique identifies the spectral lines of known elements emitted by the galaxies and uses them to measure the redshift, and thereby the distance, to the galaxies. 

Using this more accurate technique, the team found a sample of four galaxies. All those galaxies were just as distant as the previously identified galaxies, but they had confirmed, reliable distances. However, these galaxies had much smaller masses: around 10^8 and 10^9 solar masses.

So the question then became, does ΛCDM allow for these smaller galaxies to exist at such a young age in the history of the universe, or does the tension remain?

In come the simulations 

Building galaxies is no easy task. While pen-and-paper mathematics can allow cosmologists to chart the overall history and evolution of the cosmos within the ΛCDM model, galaxy formation involves the complex interplay of many kinds of physics: gravity, star formation and supernova explosions, dust distribution, cosmic rays, magnetic fields and more.

Accounting for all these interactions requires the use of supercomputer simulations that take the raw, primal state of the universe as it was billions of years ago and follow the laws of physics to build artificial galaxies. That's the only way to connect what we see in the real world (galaxies) with the fundamental parameters of the ΛCDM model (like the amount of normal and dark matter in the cosmos).

The simulations allowed the researchers to play around with many kinds of models. If no models could generate galaxies of that mass at that age, then ΛCDM would be in trouble.

Thankfully, there were no such problems. The appearance of galaxies with 10^8 solar masses in the early universe was no sweat for ΛCDM, the team explained in their research paper, which has been submitted to The Astrophysical Journal Letters and is available as a preprint via arXiv.

As usual, this isn't the final answer. Astronomers may yet confirm the distance to a very large galaxy in the early universe that may force us to rethink our understanding of galaxy formation, and maybe even the ΛCDM cosmological model. In science, it's always important to keep an open mind. But the exaggerated claims made from the early Webb data aren't enough to worry about yet.

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It's a big universe, but a new book from an All About Space editor crunches it down into a compact guide.

The universe, Milky Way and other incredible space objects are the centerpiece of "The Short Story of the Universe", by astronomer Gemma Lavender. The book is available now from Laurence King Publishing. Lavender is a long-time space writer for All About Space and also Space.com, as the two are sister websites.

Lavender summarizes nearly 14 billion years of the universe's history in little more than 200 pages, providing a pocket-sized look into how the universe came to be, why it matters and what it means for the public today.

Space.com spoke with Lavender about her aims for the book, what readers can learn and where they can get more information after completing this engaging read. You can also buy Lavender's previous books at Amazon to round out your galactic collection.

Related: Discover the glitch in the universe with All About Space magazine

Space.com: This book puts your team's work at All About Space in mind, along with the physics research you have done at Cardiff University in Wales. Can you talk about the life and work experiences you drew upon to create the book?

Gemma Lavender: The universe is an extremely mind-boggling place, which can make it quite a complex entity to understand: where do you even begin in trying to fathom how truly fascinating it is? This is something that I have come across throughout my career — the general public want to be able to understand, but may have not been taught in the right way while at school, they were bogged down in the mathematics, or amazing details were glossed over that could have really fired their interest. 

My work at Cardiff looks at how science content can inspire school leavers to go onto college to follow a STEM career; is there a way of communicating space science to inspire and engage in such a way? Are we missing a trick on accessibility or is there a specific formula that can be used to ensure that we're always increasing the number of astronomers, astrophysicists, mathematicians, computer scientists, or even science communicators, writers, editors, and other associated professions?

This is really what inspired "The Short Story of the Universe." It was created with accessibility in mind and inspires, engages and educates everyone about the cosmos — whatever the reader's background, education or age.

Related: The history of the universe: Big Bang to now in 10 easy steps

Space.com: The universe is literally such a big topic. How did you choose the things to distill in this beginner's guide?

Lavender: I wanted to ensure that a complete overview of the universe was given, while ensuring that each of the sections are in bite-sized chunks. My career has taught me that you only have a small window to really grab the attention of a reader, so it was really a balance of really pulling out the how, what, where and why with each of the subjects — what can I tell an audience and why should they care? 

Space.com: Science is built on math, so how did you teach readers the things they need to learn about topics like quantum physics, without bringing them through so many equations?

Lavender: I have to admit, this was a challenge for me when I first begin writing. Having a background in astrophysics meant that I often talked in equations and numbers, but knowing who you're speaking to before you begin writing means that you naturally leave the equations out. Equations tell us something important, but what are they telling us in words and does it tell the reader something of particular note? This is something I need to consider.

Space.com: How does one choose an artist's conception of some of the theoretical parts scientists are still struggling with, like the first few moments of the Big Bang or how the universe will die?

Lavender: When choosing images, it's important to get the balance of scientific accuracy and accessibility just right. Ensuring that there are recognisable elements in a concept, whether they're galaxies, planets or stars, brings some of the most complex ideas to life. The same goes for the theoretical portions in our understanding of the cosmos — it's important to go for the more widely accepted theories and weaving that into our artist's concepts. 

Space.com: What most surprised you when you were writing the book or assembling all the bits for publication?

Lavender: No matter how long you've been producing content about the universe, you'll learn something new about it everyday — there is always something that's truly mindboggling to know. I'll forever be amazed by how big the universe is, or at least our predictions of its size, how we think it sprang into existence and how we think it'll end.

Space.com: What do you hope people get from the book, and where should they turn next to learn more about the universe?

Lavender: I love that I am in the privileged position to engage, inspire and educate about the cosmos — I hope that the same is true of each of the readers of "The Short Story of the Universe." Even if they learned a small factoid to amaze their friends and family, or even if the book helped a school student with their homework. 

As for where they should go to learn more about the universe, I can certainly vouch for the works of Stephen Hawking, Michio Kaku and Brian Greene. If I was being biased though, I can certainly recommend Space.com and All About Space magazine to enhance a reader's knowledge!

Elizabeth Howell is the co-author of "Why Am I Taller?" (ECW Press, 2022; with Canadian astronaut Dave Williams), a book about space medicine. Follow her on Twitter @howellspace. Follow us on Twitter @Spacedotcom or Facebook.

Through a variety of tests on Earth and throughout the universe, physicists have measured no changes in time or space for any of the fundamental constants of nature. 

All of modern physics rests on two main pillars. One is Einstein's theory of general relativity, which we use to explain the force of gravity. The other is the Standard Model, which we use to describe the other three forces of nature: electromagnetism, the strong nuclear force and the weak nuclear force. Wielding these theories, physicists can explain vast swaths of interactions throughout the universe.

But those theories do not fully explain themselves. Appearing within the equations are fundamental constants, which are numbers that we must measure independently and plug in by hand. Only with these numbers in place can we use the theories to make new predictions. General relativity depends on only two constants: the strength of gravity (commonly called G) and the cosmological constant (usually denoted by Λ, which measures the amount of energy in the vacuum of space-time).

Related: The problems with modern physics

The Standard Model requires 19 constants to plug into the equations. These include parameters such as the masses of nine fermions (like the electron and the up quark), the strengths of the nuclear forces, and constants that control how the Higgs boson interacts with other particles. Because the Standard Model does not automatically predict the masses of the neutrinos, to include all their dynamics we have to add seven more constants.

That's 28 numbers that completely determine all the physics of the known universe.

 Not so constant 

Many physicists argue that having all these constants seems a little artificial. Our job as scientists is to explain as many varied phenomena as possible with as few starting assumptions as we can get away with. Physicists believe that general relativity and the Standard Model are not the end of the story, however, especially since these two theories are not compatible with each other. They suspect that there is some deeper, more fundamental theory that unites these two branches.

That more fundamental theory could have any number of fundamental constants associated with it. It could have the same set of 28 we see today. It could have its own, independent constants, with the 28 appearing as dynamic expressions of some underlying physics. It could even have no constants at all, with the fundamental theory able to explain itself in its entirety with nothing having to be added by hand.

No matter what, if our fundamental constants aren't really constant — if they happen to vary across time or space — then that would be a sign of physics beyond what we currently know. And by measuring those variations, we could get some clues as to a more fundamental theory.

And physicists have devised a number of experiments to test the constancy of those constants.

Constants to the test 

One test involves ultraprecise atomic clocks. The operation of an atomic clock depends on the strength of the electromagnetic interaction, the mass of the electron, and the spin of the proton. Comparing clocks at different locations or observing the same clock for long periods of time can reveal if any of those constants change.

Another ingenious test involves the Oklo uranium mine in Gabon. Two billion years ago, the site acted as a natural nuclear reactor that operated for a few million years. If any of the fundamental constants were different back then, the products of that radioactive process, which survive to the present day, would be different than expected.

Looking at larger scales, astronomers have studied the light emitted by quasars, which are ultraluminous objects powered by black holes sitting billions of light-years away from us. The light from those quasars had to travel those enormous distances to reach us, and they passed through innumerable gas clouds that absorbed some of that light. If fundamental constants were different throughout the universe, then that absorption would be altered and quasars in one direction would look subtly different from quasars in other directions.

At the very largest scales, physicists can use the Big Bang itself as a laboratory. They can use our knowledge of nuclear physics to predict the abundance of hydrogen and helium produced in the first dozen minutes of the Big Bang. And they can use plasma physics to predict the properties of the light emitted when our universe cooled from a plasma to a neutral gas when it was 380,000 years old. If the fundamental constants were different long ago, then it would show up as a mismatch between theory and observation.

In these experiments and more, nobody has ever observed any variation in the fundamental constants. We can't completely rule it out, but we can place incredibly stringent limits on their possible changes. For example, we know that the fine structure constant, which measures the strength of the electromagnetic interaction, is the same throughout the universe to 1 part per billion. 

While physicists continue to search for a new theory to replace the Standard Model and general relativity, it appears that the constants we know and love are here to stay.

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We know that we live in an expanding universe. That means the entire universe is getting bigger with every passing day. It also means that in the past our universe was smaller than it is today. 

Rewind that tape far enough, and the physics suggests our universe was once an infinitely tiny, infinitely dense point — a singularity. 

Most physicists think this point expanded out in the Big Bang, but because all known physics breaks down in the extreme conditions that prevailed in our universe's infancy, it's hard to say with confidence what happened in those earliest moments of the universe.

Related: Our expanding universe: Age, history & other facts

Going back in time

For most of the history of the universe, it was dotted with similar celestial objects as are present now — they were just closer together. 

For example, when our universe was less than 380,000 years old, the volume of the universe was about a million times smaller than it is today, and it had an average temperature of around 10,000 Kelvin. It was so hot and dense that it was a plasma, a state of matter where atoms are ripped apart into protons, neutrons and electrons. However, we encounter plasmas in many other situations in space and on Earth, so we have a pretty good understanding of how they work.

But the farther back we go, the more complex the physics become. When the universe was just a dozen minutes old, it was an intense soup of protons, neutrons, and electrons, still governed by the same physics that we use to understand nuclear bombs and nuclear reactors. 

If we look back even earlier than that, however, things get really sketchy.

When we try to make sense of the universe when it was less than a second old, we have no theory of physics that can cope with the insanely high temperatures and pressures the universe experienced. All of our theories of physics break down, and we have no understanding of how particles, forces and fields operate in those conditions.

Birthing the singularity

Physicists can chart the growth of the cosmos using Einstein's general theory of relativity, which connects the content of the cosmos to its history of expansion.

But Einstein's theory contains a fatal flaw. If we follow general relativity to its ultimate conclusion, then at a finite time in the past our entire universe was crammed into a single, infinitely dense point. This is known as the Big Bang singularity.

The singularity is often framed as the "beginning" of the universe: But it's not a beginning at all.

Mathematically, the singularity at the Big Bang isn't telling us that the universe began there. Instead, it's telling us that general relativity itself has broken down, and has lost its predictive and explanatory power.

Physicists have long known that general relativity is incomplete. It cannot explain gravity at high strength or at small scales, known as quantum gravity. In other words, to fully understand the earliest moments of the universe, we need new physics. 

A question for the ages

Sadly, we currently lack such physics. We have several candidates for quantum gravity, like string theory and loop quantum gravity, but these theories have not been fully developed, let alone tested.

But if either of those theories are correct, they can tell us interesting things about the early universe.

In the case of loop quantum gravity, the singularity is replaced with a finite-size chunk of space-time. In string theory, meanwhile, our universe originates from a "landscape" of possible universes. It's also possible that our Big Bang exists as just one of an infinite series of universes, multiplying without end in a multiverse. Only further advances in theoretical physics will help sort out the murkiness of these possible ideas.

But there's another problem: We may never know what caused the Big Bang. In its earliest moments, even our very conceptions of time and space break down. At such extreme scales, normal, everyday concepts like "beginning" and "before" may not even make sense. 

Originally published on LiveScience.

A new interactive map of the universe presents the entire span of the known cosmos in stunning detail and with pinpoint accuracy. 

Astronomers created the map, which shows the positions and real colors of 200,000 galaxies, using two decades' worth of data collected by the Sloan Digital Sky Survey. The interactive map can be downloaded for free at mapoftheuniverse.net, allowing the public to access information that was previously available only to scientists. 

"Growing up, I was very inspired by astronomy pictures, stars, nebulas and galaxies, and now it's our time to create a new type of picture to inspire people," Brice Ménard, a professor in the Johns Hopkins University Department of Physics and Astronomy and co-creator of the map, said in a statement. "Astrophysicists around the world have been analyzing this data for years, leading to thousands of scientific papers and discoveries."

Related: 3D intergalactic map will reveal details about dark matter, black holes and stars

Despite this effort, nobody had taken the time to create a map that is beautiful, scientifically accurate and accessible to the lay public. 

"Our goal here is to show everybody what the universe really looks like," Ménard said.

The detailed map was possible thanks to the pioneering Sloan Digital Sky Survey, one of the most influential surveys in the history of astronomy. The survey is an ambitious effort to capture a huge proportion of the night sky through the 2.5-meter telescope at Apache Point Observatory in New Mexico. Every night for eight years, the telescope has aimed its 120-megapixel camera on 1.5 square degrees of the sky at a time — around eight times the area of the full moon — at slightly different locations, to capture a broad perspective of the universe.

Ménard and former Johns Hopkins computer science student Nikita Shtarkman used these data to recreate a slice of the universe containing 200,000 galaxies. Each dot on the map is a galaxy with billions of stars and planets. Our own galaxy, the Milky Way, is just one of these dots located at the very bottom of the map. 

Let there be light 

One notable aspect of this cosmic map is the striking colors that are in part created by the expansion of the universe. As the universe expands, the wavelengths of light traveling to Earth are stretched to redder regions of the electromagnetic spectrum. The more distant a light source, the more extreme this redshift. 

At the very top of the map is the universe's first light, emitted around 13.7 billion years ago, shortly after the Big Bang, as the universe expanded and cooled enough to allow electrons to form atoms with protons. The reduction of free electrons meant that photons — individual packets of light that act as both particles and waves — were suddenly not being infinitely bounced around and were instead free to travel. In an instant, the universe effectively went from being opaque to transparent.

At the opposite end of the interactive map is the Milky Way, including the solar system and Earth as they exist today.  

"In this map, we are just a speck at the very bottom, just one pixel," Ménard said. "And when I say 'we,' I mean our galaxy, the Milky Way, which has billions of stars and planets." 

Ménard hopes that, in addition to displaying the universe in its full beauty, the interactive map will demonstrate the awe-inspiring scale of the universe. 

"We are used to seeing astronomical pictures showing one galaxy here, one galaxy there, or perhaps a group of galaxies," he said. "But what this map shows is a very, very different scale. From this speck at the bottom, we are able to map out galaxies across the entire universe, and that says something about the power of science."

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NASA's newest space telescope has left scientists seeing distant stars — and galaxies.

The James Webb Space Telescope (Webb or JWST), which launched in December 2021, has executed just five months of science observations. Astronomers knew the $10 billion telescope would offer a new view on the universe, but early observations have still blown those expectations away. In particular, JWST has carried scientists out deeper into the universe, farther from Earth and earlier in cosmic history than researchers had anticipated

"We're really on track to realizing the dream of understanding galaxies at the earliest times," Garth Illingworth, an astronomer at the University of California, Santa Cruz, said during a NASA news conference held Thursday (Nov. 17) dedicated to early science results from the new observatory. "The last few months have been exciting, but a huge amount remains in front of us to learn and to gain insights into what is really happening in the first billion years of galaxies."

Related: Dazzling James Webb Space Telescope image prompts science scramble

The very first science-quality image released by the JWST team — an image showing countless galaxies sprinkled across space — sparked a scramble as scientists hunted for the most distant galaxies in the observable universe, a quest that continued as the telescope settled into operations.

"One thing that really struck me in the early days of JWST images is how quickly our understanding of galaxies is changing," Jeyhan Kartaltepe, an astrophysicist at the Rochester Institute of Technology in New York, said during the briefing. She looked back to the moment the first image was revealed, saying, "We were witnessing a once-in-a-generation moment where, just overnight, our capabilities and understanding of the universe were about to change."

Because light travels at a fixed speed, observing distant objects means seeing them as they were in the past, so the most distant galaxies astronomers can see are also the most primitive.

Now, some of those early finds have been published in peer-reviewed studies. Perhaps the star of the show is a galaxy dubbed GLASS-z12, which two separate teams of researchers have used early JWST observations to date to just 350 million years after the Big Bang. The find made headlines in July but even now isn't quite settled.

Since the detection, a ground-based facility, the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile, has offered "a tentative confirmation" of the distance analysis, Tommaso Treu, an astronomer at the University of California at Los Angeles and co-author on one of the new papers, said during the briefing.

However, sealing the deal requires new and different JWST data. The research to date identifying GLASS-z12 and other distant candidates has analyzed images. Scientists can estimate distances from images, but nearer galaxies have been known to masquerade as distant ones in this type of data.

A more reliable technique relies on what scientists call spectra, the barcode-like smear of light from an object separated by wavelength. It's a type of data JWST specializes in, but the astronomers must wait as the observatory conducts the plentiful science already booked for its first year in space.

The researchers have asked that the observatory use a separate instrument to revisit the galaxy in the coming months. That hope comes through a program that allows the Space Telescope Science Institute in Maryland, which operates the observatory for NASA, to jump on fleeting opportunities that couldn't have been predicted when scientists applied for time in the telescope's first year. The astronomers have not yet heard back, Treu said; if the request is rejected, they will propose the work for the observatory's second year, which begins next July.

But even without spectral observations in hand, Treu said he and his colleagues feel confident in their dating of GLASS-z12. "I think this is as solid as it gets at this point without JWST confirmation," he said.

Early bounty 

The finding, and the other identifications of super-distant galaxies scientists have proposed in the months since JWST started work, aren't just curiosities. Identifying these primitive galaxies allows scientists to hone the timeline between the Big Bang and the universe as we see it today.

Astronomers had estimated how many galaxies they might find at these distances, but in JWST's observations to date, candidates are proving more plentiful than expected. The bounty means that galaxies — and, in turn, the stars they're made of — must have started forming earlier than scientists previously thought.

"Finding these really bright galaxies has opened up the whole ballgame," Illingworth, a co-author on the second paper, said. Perhaps the first stars might have formed just 200 million years after the Big Bang, he said.

"That's a happy surprise, that there's lots of these kinds of galaxies to study," Jane Rigby, Webb operations project scientist at NASA's Goddard Space Flight Center in Maryland, said during the briefing.

"These galaxies we're talking about are bright, and so they were hiding, just under the limits of what Hubble could do," she added. "They were right there waiting for us — we just had to go a little redder and go deeper than what Hubble could do."

The research is described in two papers published in The Astrophysical Journal Letters — one on Oct. 18 and one on Thursday (Nov. 17).

Email Meghan Bartels at mbartels@space.com or follow her on Twitter @meghanbartels. Follow us on Twitter @Spacedotcom and on Facebook.

As cosmic strings — exotic wrinkles in space-time left over from the earliest moments of the Big Bang — travel, they may trigger the formation of magnetic fields in their wakes, new research suggests. These magnetic fields would then soak the universe, thereby explaining the magnetization of galaxies and clusters, scientists propose in a new paper.

Almost every substantial object in the universe hosts a magnetic field. Smaller objects, like planets and stars, generate their own magnetic fields from dynamo actions inside them, where swirling flows of electrically charged plasma force weak magnetic fields to fold over themselves.

At larger scales, astronomers have observed magnetic fields inside nebulas, supernova remnants and protoplanetary disks. In those cases, complex flows of charged particles can generate weak fields.

Related: Listen to the terrifying rumble of Earth's magnetic field being assaulted by a solar storm

Some of the largest objects in the universe, like galaxies and clusters of galaxies, also maintain magnetic fields. They're typically very weak — around a millionth the strength of Earth's magnetic field — but they are tremendous, in some cases stretching for millions of light-years.

Astronomers aren't exactly sure how galaxies and clusters get their magnetic fields. To make a magnetic field, you need charged particles moving together. But at the early stages of the universe's development, before the appearance of the first stars and galaxies, the cosmos was electrically neutral. A neutral gas can't generate magnetic fields on its own, so somehow, the universe had to create a magnetic field.

Once the universe had that initial seed magnetic field, it could amplify it when the evolution of the universe changed the neutral gas into an electrically charged plasma. But the source of the first magnetic field has been an enduring mystery in astronomy for decades.

Tangled cosmic strings 

In a new paper published to the preprint server arXiv, researchers propose what's perhaps the most exotic explanation for the source of the universe's seed magnetic field: cosmic strings.

Cosmic strings are theoretical objects that many astronomers believe formed in the very early universe. When our cosmos was less than a second old, it went through several stages of violent phase transitions. At the earliest times, all four forces of nature were unified into a single force. These phase transitions took the unified force and, one by one, split it into the forces of gravity, the strong nuclear force, the weak nuclear force and electromagnetism.

With each splitting of the forces, the fundamental vacuum of space-time reconfigured itself. But that process may not have been completely smooth or perfect, and flaws may have appeared in space-time. Some of these defects appeared as one-dimensional folds in space, like wrinkles in a piece of paper. These are the cosmic strings.

Astronomers have been hunting for cosmic strings ever since they were theorized in the 1970s. So far, all searches have turned up empty, and yet cosmic strings appear to be a generic prediction of all of our theories of the early universe.

If cosmic strings do exist, they would be very strange indeed. For example, because of the unique way they fold space-time, if you were to travel in a circle around one, when you completed your journey and returned to your starting point, you would find that you had traveled less than 360 degrees. Cosmic strings can also vibrate, with the ripples traveling up and down their length at the speed of light, and occasionally form loops that then vibrate themselves to death in a frenzy of radiation.

The making of magnetization 

The study authors took advantage of the unique properties of cosmic strings to turn them into generators of magnetic fields. The idea is that, as cosmic strings traveled, they would leave behind ripples in the fabric of space-time, like wakes trailing a speed boat.

If a cosmic string passed through a plasma, those ripples in space-time could change the temperature and density of small pockets in the plasma. Those differences would set electric charges in motion, and they could become the beginnings of a magnetic field. Those seed fields wouldn't be very strong — less than a millionth of a millionth of Earth's magnetic field — but it would be enough. 

Once the cosmic strings left the area, the remaining plasma could compress and cool to form stars, galaxies and clusters. As the plasma compressed, it could have amplified that initial field into the strengths that astronomers see today.

Although this hypothesis is interesting, it has a major problem: We don't yet know if cosmic strings exist. Thankfully, the authors addressed that point and noted a potential observation signature of cosmic strings. Those same wakes that generate magnetic fields in plasmas continue to persist long after the cosmic string has departed. Eventually, the wakes wash over Earth in the form of gravitational waves.

If there were enough cosmic strings in the early universe, it might be possible for us to observe the remnants of their space-time wakes with the next generation of gravitational wave detectors. And once we know that cosmic strings actually did exist at some point, we just might finally know what caused the universe to become magnetized.

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New research highlights a troubling problem with concepts of a cyclical universe that experiences infinitely alternating periods of rapid expansion and contraction, known as 'bouncing universe' models.

These bouncing universe models suggest the cosmos has no beginning, eliminating the need for a troubling singularity prior to the initial period of rapid inflation  — commonly known as the Big Bang —  needed by 'beginning of time' models. 

University at Buffalo researchers say a newly suggested bouncing universe recipe that attempts to deal with the problem of entropy  —  the measure of unusable energy in the universe, which can only increase  —  suffers from a problem that has plagued previous models of endless inflation and contraction. It still needs a beginning.

Related: The Big Bang: What really happened at our universe's birth?

"People proposed bouncing universes to make the universe infinite into the past, but what we show is that one of the newest types of these models doesn't work," University of Buffalo physicist Will Kinney said in a statement. "In this new type of model, which addresses problems with entropy, even if the universe has cycles, it still has to have a beginning."

This means that proponents of cyclical models of the universe may have to go back to the drawing board. 

The leading theory of the universe's origins is so-called 'cosmic inflation.' This suggests that before time began all the energy in the cosmos was contained in a singularity  —  an infinite dimensionless point not described by the laws of physics.

This ended with a period of rapid inflation  —  the Big Bang  —  that saw the universe expand and cool, thus allowing the formation of matter  —  first atoms of hydrogen, then heavier elements, and eventually stars and galaxies.

The problem is, while this theory is very good at describing the universe as it ages from fractions of a second until the cosmic structure we see today, around 13.8 billion years later, it can't describe the conditions of the singularity that existed before this inflation was kick-started. Or even what kick-started it.

This issue is eliminated by a bouncing universe because if periods of inflation and collapse are infinite, then there was no beginning and thus no need to explain what preceded it. This would see the universe undergo similar inflation as suggested by the cosmic inflation model, but then 'springing back' on itself in a 'Big Crunch' of sorts.

Each new inflation period would, therefore, begin from the 'wreckage' of a previous period of expansion rather than a singularity. But, Kinney thinks that bouncing universes come with their own unique problems.

"Unfortunately, it's been known for almost 100 years that these cyclic models don't work because disorder, or entropy, builds up in the universe over time, so each cycle is different from the last one. It's not truly cyclic," the UB researcher said. "A recent cyclic model gets around this entropy build-up problem by proposing that the universe expands a whole bunch with each cycle, diluting the entropy."

Kinney said that this new bouncing universe model tries to stretch everything out to get rid of cosmic structures such as black holes thus returning the universe to its original homogenous state before another bounce begins.

"We showed that in solving the entropy problem, you create a situation where the universe had to have a beginning. Our proof shows in general that any cyclic model which removes entropy by expansion must have a beginning," he said, adding one bouncing universe may survive this assessment. "Our proof does not apply to a cyclic model proposed by Roger Penrose, in which the universe expands infinitely in each cycle. We're working on that one."

Kinney's collaborator is UB physics Ph.D. student, Nina Stein. She highlighted the problem the duo had with a bouncing universe: "The idea that there was a point in time before which there was nothing, no time, bothers us, and we want to know what there was before that  —  scientists included.

"But as far as we can tell, in models that address entropy, there must have been a 'beginning.' There is a point for which there is no answer to the question, 'What came before that?'"

This means, for now, the mystery of what existed before the universe and time itself remains and will be hotly debated by cosmologists for some time to come.

"There are a lot of reasons to be curious about the early universe, but I think my favorite is the natural human tendency to want to know what came before," Stein said. "Across cultures and histories, humans have told stories about creation, about 'in the beginning.' We always want to know where we came from."

Kinney and Stein's findings are discussed in a paper published in the June edition of the Journal of Cosmology and Astroparticle Physics. 

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The "most comprehensive studies" of the Higgs boson conducted to date reveal that the particle behaves just as expected and could help unlock some of the greatest mysteries of physics, including the nature of dark matter, scientists say.

Two new studies, based on 10,000 trillion proton-on-proton collisions conducted inside the Large Hadron Collider (LHC) during its second run, which ended in 2018, analyzed 8 million Higgs boson particles detected by the LHC's ATLAS and CMS detectors. 

The studies were published on Monday (July 4), the 10th anniversary of the Higgs boson discovery by the LHC, the world's largest particle smasher. They show that the particle behaves just as predicted by the Standard Model of particle physics, the all-encompassing theory describing how the basic building blocks of the universe hold together. 

Related: The Large Hadron Collider returns in the hunt for new physics

The Higgs boson plays a prominent role in the Standard Model. The particle is a carrier of an all-pervading quantum field, known as the Higgs field, which gives other elementary particles their mass. 

"After just 10 years of Higgs boson exploration at the LHC, the ATLAS and CMS experiments have provided a detailed map of its interactions with force carriers and matter particles," ATLAS spokesperson Andreas Hoecker said in a statement. "The Higgs sector is directly connected with very profound questions related to the evolution of the early universe and its stability, as well as to the striking mass pattern of matter particles."

During the experiments, physicists studied how Higgs bosons interact with each other and also with other particles. Such interactions frequently lead to Higgs bosons decaying into other particles, and scientists believe that, somewhere in this chain reaction, they could produce dark matter, the elusive substance that no one has ever seen directly but which is believed to make up about 80% of all matter in the universe.  

"Sketching such a portrait of the Higgs boson this early on was unthinkable before the LHC started operating," CMS spokesperson Luca Malgeri said in the same statement. "The reasons for this achievement are manifold and include the exceptional performances of the LHC and of the ATLAS and CMS detectors, and the ingenious data analysis techniques employed."

The Large Hadron Collider, run by the European Organization for Nuclear Research (known by its French acronym, CERN) in an underground tunnel near Geneva in Switzerland, restarted earlier this year with its third run of experiments that will see it smash particles with even greater force than before. Some 180 million Higgs boson particles are expected to be produced during the new batch of studies, which will further improve the precision of the measurements of the particles' interactions. 

The studies describing the ATLAS and CMS experiments were published on Monday in the journal Nature.

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook. 

The Large Hadron Collider (LHC) is back and smashing particles at higher speed than ever before, exciting scientists with its upgraded potential.

The Large Hadron Collider is the world's longest and most powerful particle accelerator, zipping subatomic particles through a 17-mile-long (27 kilometer) loop underneath Geneva at speeds nearing that of light. Already the collider has led to some 3,000 scientific papers since beginning operations in 2010; now, with new upgrades, it's poised to showcase new insights, team members say.

"It's a magic moment," Fabiola Gianotti, Director-General of the European Organization for Nuclear Research (CERN), said during a press conference held on Tuesday (July 5) after the facility's new science run began. "We just had collisions at an unprecedented energy of 13.6 tera-electron volts, and this opens a new era of exploration at CERN," Gianotti added. 

Related: 10 years after the discovery of the Higgs boson, physicists still can't get enough of the 'God particle'

Increased energy, more collisions and better data collection practices may allow scientists to learn more about the subatomic world, perhaps even surpassing the Standard Model of particle physics.

"We really hope that we're going to collect something like 10 times as much data in this next run as we collected before, so hopefully, we can see a whole range of new phenomena," Chris Parkes, a spokesperson for the LHCb experiment, said in the same press conference. 

LHCb seeks to study differences between matter and its mirror, known as antimatter, by studying the "beauty quark" (or b quark) particle. Parkes noted it took 15 years of planning to get this far, which means that finally operating the upgraded detector "is a really exciting time." 

Patricia McBride, spokesperson for the Compact Muon Solenoid detector at CERN, told reporters that the hope is to see "lots more Higgs," referring to the Higgs-Boson scientists at last discovered almost exactly 10 years ago using LHC. The so-called "God particle" predicts the mechanism that gives rise to mass and is fundamental to subatomic physics and the Standard Model.

McBride said the upgraded LHC will "be able to do precision measurements to understand what the Higgs is, what it's telling us about nature." The pivot to using Higgs in this way is "really exciting," McBride added, as "now we're actually using it as a tool to look for new physics."

Uncovering these new insights with Higgs will be helpful to studies of the universe at large, Gianotti said: "It's a very special particle with very special properties, which brings new interactions. In some sense, [Higgs] is related to many open questions related to, for instance, the evolution of the universe [and] to even its fate."

While discovery schedules are unpredictable, Gianotti said the "dream scenario" would be LHC at last uncovering the elusive nature of dark matter, which constitutes much of the known universe but cannot be directly seen with conventional instruments. (Accurate measurements of dark matter are key in predicting the expansion of the universe, among other things.)

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A new simulation maps the first few seconds after the Big Bang, focusing on what scientists call the intergalactic medium, or the gas and dust between galaxies.

A team led by researchers at the Institute of Astrophysics of the Canary Islands (IAC) used machine learning, a type of algorithm in which a computer is trained to recognize patterns, to complete 100,000 hours of computation. The algorithm for this project is called Hydro-BAM.

This new work allowed researchers to chart phenomena including dark matter, energized gas, neutral hydrogen and other cosmic ingredients that are essential to understanding the structure of our universe, IAC representatives said in a May 20 statement.

Related: The history of the universe: Big Bang to now in 10 easy steps

"The research has also made it possible to reproduce with high precision the so-called 'Lyman-alpha forests,'" they added. That is a particular pattern of lines in a spectrum (light signature) of galaxies and similar objects created when clouds of hydrogen gas in the way absorb the galactic light.

"These 'virtual universes' serve as test beds for the study of cosmology," the researchers added. "However, the simulations are computationally very expensive, and current computing facilities only allow [us] to explore small cosmic volumes."

Hydro-BAM is designed to include probability, machine learning and cosmology, meaning the history of the universe. "This algorithm has made it possible to obtain very accurate predictions in just a few tens of seconds," the researchers said.

Charting the absorption lines in the galactic spectra allowed the team to learn about where the clouds of hydrogen gas are located. Location is a proxy for distance, given that the universe is continually expanding. The clouds also give clues as to what is contained in the intergalactic medium of gas and dust.

"The breakthrough came when we understood that the connections between the quantities of intergalactic gas, dark matter and neutral hydrogen that we were trying to model are well organized in a hierarchical way," Francesco Sinigaglia, a doctoral student at the University of La Laguna in Spain, the IAC and the University of Padua in Italy, and lead author of the research, said in the statement. 

The most recent study on the research was published in March in The Astrophysical Journal, and a related study was published in the same journal in November 2021.

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The world's most powerful heavy-ion accelerator — which will create new exotic atoms and reveal how stars and supernovas forge the elements that make up our universe — is finally completed, researchers announced May 2. 

Experiments at the $730 million Facility for Rare Isotope Beams (FRIB) at Michigan State University (MSU) are slated to start this week. Once online, the new reactor will fire two heavy atomic nuclei at each other, splitting them apart in ways that enable scientists to study what glues them together and how rare atomic isotopes — versions of chemical elements with different numbers of neutrons in their nuclei — are structured.

While past heavy-ion accelerators (such as the National Superconducting Cyclotron Laboratory, MSU's previous accelerator) enabled scientists to catch glimpses of exotic atoms, they didn't produce them at a fast enough rate to make detailed study possible. The new FRIB accelerator will grant researchers access to more than 1,000 new isotopes, giving them fresh insight into new cancer treatments, radiometric dating of ancient materials, and nuclear security, according to MSU scientists. 

Related: 'X particle' from the dawn of time detected inside the Large Hadron Collider

"FRIB will be the core piece of our nation's research infrastructure," Thomas Glasmacher, the FRIB Laboratory Director, said at the ribbon-cutting ceremony, according to the Lansing State Journal. "More than 1,600 scientists are eager to come here because we will be the best, most powerful superconducting heavy-ion linear accelerator."

Physicists are excited by the FRIB because it may provide a much clearer view of the landscape of possible atomic isotopes. Right now, physicists have a good idea of what holds nuclei together — one of the four fundamental forces called the strong force — and have made a good number of models to predict what some unobserved atomic nuclei might look like. But nuclei are complex and can glue together in surprising ways, making the models far too simplistic. A number of the nuclei predicted by the models, for instance, might not hold together well enough to exist.

Other questions that scientists hope to answer include how well the most stable isotopes are described by current models, and how elements heavier than iron and nickel (the latter two being the heaviest elements made by nuclear fusion in stars) are formed through radioactive beta decay. Beta decay takes place when an atomic nucleus absorbs a neutron or when one of its neutrons becomes a proton, making the nucleus unstable.

Scientists believe that elements formed by beta decay are typically made as byproducts of supernovas or the collisions of neutron stars, but until now haven't been able to check, or to study what kinds of elements are produced and in what proportions during these celestial processes. But FRIB will provide a way to finally test these suppositions, as one if its accelerators speeds up individual isotopes before smashing them into a target, enabling scientists to simulate the collisions that take place inside stars and supernovas.

To produce isotopes for study, physicists will select atoms of a very heavy element, such as uranium, before stripping them of their electrons to turn them into ions. Then they will launch them down a 1,476-foot-long (450 meters) pipe more than halfway to the speed of light. At the end of the pipe, the beam of ions will hit a graphite wheel, splintering into smaller neutron-proton combinations, or isotopes.

By steering these freshly made isotopes through a series of finely adjustable magnets, the physicists will be able to carefully select which isotope they want to fire into one of the facility's experimental halls for further study. FRIB will eventually be joined by another atom smasher, the $3.27 billion Facility for Antiproton and Ion Research (FAIR) currently being built in Darmstadt, Germany. The accelerator, set for completion in 2027, has been designed to make antimatter as well as matter, and will be able to store the nuclei it produces for longer timeframes than FRIB.

Originally published on Live Science.

If you thought the coldest place on Earth is Antarctica, well, you just might be wrong about that. One of the coldest places on Earth is actually in Menlo Park, California — or more specifically, 30 feet (9 meters) below it.

An underground superconducting particle accelerator at the SLAC National Accelerator Laboratory has been cooled down to a mind-boggling minus 456 degrees Fahrenheit (minus 271 degrees Celsius or 2 kelvin). That's just a few degrees above the coldest possible temperature in the universe, absolute zero. The extreme cooling is part of an upgrade to the Linac Coherent Light Source (LCLS) X-ray free-electron laser — soon to be dubbed LCLS-II — which can accelerate electrons close to the speed of light. The apparatus is used to study rare chemical events, biological molecules, quantum mechanics and complex materials used in computing (an appropriate purpose, given the accelerator's location in Silicon Valley).

Once the upgrades are complete, LCLS-II will be able to produce X-ray pulses 10,000 times brighter than its predecessor, at a rate of up to one million pulses per second — something that's only possible under the extremely cold temperatures of the accelerator, according to a statement from the facility.

Related: 10 cosmic mysteries the Large Hadron Collider could unravel

In the former iteration of LCLS, which began work in 2009, electrons were accelerated through half a mile of copper pipes at ambient temperature, which only permitted a maximum of 120 X-ray pulses per second. 

Instead, the new system features 37 cryogenic accelerator modules lined with cavities made of the metal niobium, all surrounded by a host of cooling equipment. Once the niobium cavities reach minus 456 F, they become superconducting. That state eliminates electrical resistance so that the electrons can reach incredibly high speeds.

"In just a few hours, LCLS-II will produce more X-ray pulses than the current laser has generated in its entire lifetime," Mike Dunne, director of LCLS, said in the statement. "Data that once might have taken months to collect could be produced in minutes. It will take X-ray science to the next level, paving the way for a whole new range of studies and advancing our ability to develop revolutionary technologies to address some of the most profound challenges facing our society."

To develop LCLS-II, SLAC partnered with Argonne National Laboratory, Lawrence Berkeley National Laboratory (Berkeley Lab), Fermilab, the Thomas Jefferson National Accelerator Facility (Jefferson Lab), and Cornell University.

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The inflationary epoch that caused our universe to rapidly expand in its earliest moments may be connected to the modern era of dark energy, thanks to a phantom component of the cosmos that changes the strength of gravity as the universe evolves, a physicist proposes in a new paper.

The traditional approach to understanding gravity involves Einstein's famous theory of general relativity. For such a powerful idea, which can explain everything from the orbit of the moon to the evolution of the entire universe, it's a pretty simple concept. In general relativity, there is just space-time and the contents inside it. The contents of the cosmos cause space-time to bend and warp, and the bending and warping of space-time dictate how the contents should move.

For example, the presence of a planet distorts space-time around it, causing other objects to follow in orbits, or the distortions caused by a star can deflect the path of passing light.

Related: Was Einstein wrong? The case against space-time theory

Although general relativity is the simplest approach to gravity, it is not the only one. An alternative, known as scalar-tensor theories, goes back to the early 1960s and is the work of physicists Robert Dicke and Carl Brans, so sometimes it gets the name Brans-Dicke theory.

In scalar-tensor theories, in addition to space-time and its contents, there's a third ingredient, known as a scalar field. The scalar field soaks all of space-time, and its one job is to change the strength of gravity from place to place or from time to time. In vanilla general relativity, the strength of gravity is fixed; it's just Newton's gravitational constant, forever and always. No matter where or when you are in the universe, a given amount of mass and energy will always distort space-time in the exact same way.

But in scalar-tensor theories, that can change. A planet on one side of the universe could have a weaker or stronger impact on space-time around it, depending on the local value of the scalar field. The strength of gravity can also change with time, if the scalar field itself evolves.

Tuning the cosmos

Experimentally, general relativity and scalar-tensor theories are equivalent. General relativity has passed every single experimental obstacle thrown at it. But if you take a scalar-tensor theory and simply assume that your scalar field has a constant value equal to Newton's constant, then you also get those same results. But because general relativity is so much simpler than scalar-tensor theories and there's no known way to tell them apart, physicists prefer Einstein's classic theory.

Except there's a little problem: dark energy. According to observations, the expansion of the universe is accelerating, but at a very gentle pace. The only way to account for this in general relativity is to include a cosmological constant, an extra value in the equations that has an incredibly small, but not quite zero, value. That feature of the cosmological constant troubles most physicists because it seems incredibly unnatural. If dark energy had almost any other value, the expansion of the cosmos would have torn apart the cosmos long ago, leaving it unable to support life (including anyone who could observe it), and yet it's not perfectly zero, either.

"Adding extra values to the equations" sure does look a lot like scalar-tensor theories. So, ever since astronomers discovered dark energy in the late 1990s, physicists have been working to see if there's a potential way for that long-discarded model of gravity to explain the accelerated expansion more naturally.

Curiously, the present era is not the only time the expansion of the universe has gone into overdrive. Cosmologists think that very early in the Big Bang, the universe experienced a period of extremely rapid expansion known as inflation. You might wonder if there's a connection between the early period of inflation and the modern period of dark energy, and you're not the only one.

Gravitational threads

Now, Motohiko Yoshimura, a physicist at the Research Institute for Interdisciplinary Science at Okayama University in Japan, has proposed that scalar-tensor theories provide a direct link between inflation and dark energy.

In this model, described in a paper published in the preprint database arXiv, the scalar field part of the scalar-tensor theory (the "tensor" refers to space-time itself) is a lot stronger in the early universe, thereby triggering the epoch of inflation. At the end of inflation, the scalar field weakens and releases its energy in the form of all the particles of the Standard Model (like quarks and electrons).

Crucially, the scalar field never goes away. It maintains some background presence as the universe continues to evolve, forming stars and galaxies in the meantime. Then, after cosmic expansion dilutes all the matter to a low enough level, the scalar field kicks in again — but at a much weaker level — giving rise to the current era of dark energy.

But while it's an intriguing story, astronomers still need to test the hypothesis. Thankfully, this model produces a lot of potentially observable relics of the early universe. For example, in this scenario, gravity can be so strong in places that black holes spontaneously form and survive to the present day. Finding evidence of these primordial black holes would help bolster the idea. 

Another approach is to search for gravitational waves from the early universe that are left behind when inflation is done. Astronomers can look for these gravitational waves either directly, by trying to detect them in the faint background hum of the universe, or through their influence on this so-called cosmic microwave background. 

Physicists know that dark energy and inflation represent the current boundaries of our knowledge, and only radical suggestions like this — and the experiments to go along with them — will help us push past that edge.

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Scientists are investigating the elusive neutrino with a new experiment at the Large Hadron Collider (LHC).

Scientists used the Compact Muon Solenoid (CMS) detector at the LHC at CERN (the French acronym for the European Organization for Nuclear Research) near Geneva, Switzerland for a new experimental test investigating the mass of neutrinos.

Neutrinos, or "ghost particles," are subatomic particles similar to electrons but with no electrical charge and a minuscule, near-zero mass. The new study used data from the LHC's previous run.(In April, the particle accelerator was restarted after a three-year shutdown, which was implemented for upgrades and maintenance.) 

This experiment was conducted to try and answer the question of why the neutrino has such a small mass. (The neutrino has such little mass that scientists throughout history have suggested it might have no mass at all.)

Related: Large Hadron Collider will explore cutting edge physics after 3-year shutdown

Produced within stars through nuclear fusion, neutrinos are strange and mysterious particles that have eluded our full understanding for years. We know that they are one of the most common particles in the entire universe; it has been estimated that about 100 billion neutrinos pass through every square centimeter of the human body every second.

According to the current Standard Model of particle physics, a theory that describes all known fundamental particles and three of the four forces in the universe, elementary particles like electrons gain their mass by interacting with a field associated with the Higgs boson particle, known as the Higgs field. But the neutrino doesn't play by these rules; the Higgs field cannot explain its minimal mass. 

With this experiment, researchers tested what is called the "seesaw model" that some researchers think could explain the neutrino's mass. Within this theory, a light neutrino (a known particle) pairs with a hypothetical heavy neutrino, which acts like the heavier partner on a seesaw, lifting the lighter particle up and giving it its very light mass. 

But for the seesaw model to work, the neutrinos involved would need to essentially be their own antimatter particles, called Majorana particles, according to a statement describing the new research. Antimatter particles have the mass of their corresponding particles but with an opposite electric charge. (The antimatter equivalent of the electron, for example, is the positron.)

So, to test the seesaw model with this experiment, researchers tried to find Majorana neutrinos in high-energy particle collisions at the LHC. The team used the CMS detector to collect the data from these collisions. While the study is recent, the collisions producing this data took place between 2016 and 2018.

The team didn't find any evidence of Majorana neutrinos in the data.However, the data they did collect helped them to set new limits on the seesaw model. 

Now, while this is a new study from older collisions at the LHC, with the facility switched back on, the particle accelerator is ready to start making new collisions this summer, and researchers "can look forward to collecting more data and trying out the seesaw again," according to the same statement.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

What mysteries of the universe could the world's largest and most powerful particle accelerator unlock?

The Large Hadron Collider (LHC) at CERN (the European Organization for Nuclear Research) near Geneva, Switzerland was just switched back on for the third time after a three-year hiatus planned to implement upgrades. In the 14 years since it was first turned on, the particle accelerator has explored some of the biggest mysteries in the universe, colliding countless particles at near the speed of light in a tunnel  328 feet (100 meters) underground. 

One of the most amazing things about the LHC is that scientists don't know exactly what might happen when they smash protons together at nearly the speed of light. Despite its years of driving groundbreaking science, at the end of Run 2 in 2018, scientists estimated that the LHC had only delivered about 3% of the data expected in its lifetime. And it's just getting started.

There are some major mysteries in the universe that scientists hope to answer, and the LHC could be instrumental in some of that progress. Below, let's explore 10 strange corners of the universe that the LHC could explore.

Related: The Large Hadron Collider will explore the cutting edge of physics after 3-year shutdown

The Higgs boson

What is probably the most famous discovery to come out of the LHC to-date, the Higgs boson, is an elementary particle the existence of which was confirmed in 2012 at the LHC. There is, however, still a lot to be learned from studying the strange particle..

First proposed in 1964 by a group of theorists including Peter Higgs and François Englert, the Higgs boson was the last undiscovered particle predicted by the Standard Model, the theory that explains all known fundamental forces and particles in the universe. (In 2013, Higgs and Englert were awarded the Nobel Prize in physics following the LHC's detection of the Higgs boson the year before.)

The Higgs boson was suggested as an explanation for why certain particles have mass. The particle is associated with what is called the Higgs field, which gives mass to other elementary or fundamental particles like electrons and the quarks that make up protons. The particle even gets its own mass from interactions with the Higgs field. 

But not all fundamental particles have mass: The photon, or light particle, has no mass, for example. There remain many mysteries about the Higgs boson and, with future experimentation at the LHC, particle physicists could paint a more complete picture of this strange particle.

LHC scientists have already observed the Higgs particle doing strange things ever since they finally spotted it, offering additional mysteries to solve. In fact, in Run 2 at the LHC, researchers experimented to see if the Higgs boson might decay into dark matter particles (though they did not detect this.)

Dark matter

Scientists hope that with the help of the LHC, they will be able to find particles that constitute dark matter, the never-before-observed stuff that makes up about 80% of all matter in the universe.

Dark matter is a mysterious material that scientists predict makes up over 80% of all matter in the universe. Although dark matter is invisible material, of stars, planets and galaxies. In other words, we can't see dark matter but we know it's there because we can see its effects.

"Dark matter is most of the matter in the universe, and we have no idea what it is. One of the most outstanding questions in all of science is, 'What is dark matter?'" Benjamin Safdi, an assistant professor of physics at the University of California, Berkeley whose research includes investigating possible explanations for dark matter, said in a statement. 

Currently, scientists have a number of different dark matter candidates, strange particles that could be the elusive dark matter. But, while the culprit hasn't yet been identified, the LHC remains a powerful tool that scientists will continue to use to solve this major mystery.

"If the LHC detects a potential dark-matter particle, it will require confirmation from the other experiments to prove that it is indeed a dark-matter particle," CERN officials wrote in a statement. "By contrast, if the direct and indirect experiments detect a signal from a dark-matter particle interaction, experiments at the LHC could be designed to study the details of such an interaction."

Dark Energy

While its name might seem to imply that dark energy is similar to dark matter, their connection lies in the name alone. 

In addition to their similar names, dark energy is also invisible and expansive. Dark energy is a mysterious force suspected to make up nearly three-fourths of the universe, and scientists think it's causing the expansion of the universe is speeding up. 

While the LHC is designed to experiment with particles, some theorists have suggested that if dark energy is a type of force or field, then the LHC could be used to investigate that idea, similarly to how the LHC used the Higgs field to produce the Higgs boson particle, physicist Clare Burrage described to Symmetry Magazine. 

"Cosmologists know that there is new physics we don't understand, and all the evidence is pointing toward something very fundamental about our universe,” Burrage said. "The experiments on the LHC are also very interested in the fundamentals."

Scientists have also suggested that dark energy, if it's a type of field, could produce light-weight particles, Burrage said.

"The main focus of LHC has been heavy particles, so we had to go back and re-interpret the data to look for something light," she added.

WIMPs

In terms of dark matter, one of the candidates that's gotten serious attention over the years has been weakly interacting massive particles, or WIMPs, which LHC has already investigated. 

WIMPs are hypothetical particles that are said to interact via forces including gravity and which might exist outside of the Standard Model.

"The LHC has really broken new ground in the search for dark matter in the form of weakly interacting massive particles," dark-matter theorist Tim Tait of the University of California Irvine involved in the LHC Dark Matter Working Group said in a CERN statement. 

So far, the LHC has attempted to spot this dark matter candidate. Scientists have used the LHC to look for WIMPs by searching for signals of what might be created by, for example, WIMPs interacting with ordinary matter, Tais said. 

But "all of the observed results have been consistent with models that don’t include dark matter," Tait said. However, the data so far gives "us important information as to what kinds of particles can no longer explain [dark matter]."

Even if WIMPs can't explain dark matter, chasing these particles has been fruitful. "The results have both pointed experimentalists in new directions for how to search for dark matter, and prompted theorists to rethink existing ideas for what dark matter could be — and in some cases to come up with new ones," Tait added.

But the door isn't completely shut on WIMPs, and the mystery of what they may or may not be still hangs out there. 

"I still hold a fire for WIMPs," John Ellis, a particle physicist, told Space.com earlier this year. 

Axions

Axions are another hypothetical elementary particle that have been in the spotlight as WIMPs have lost a bit of their luster in the scientific community. The axion, proposed in 1977, has both low mass and low energy; in 2020, physicists found the first direct evidence of axions and fanned the flames of interest in the particle as a dark matter candidate.

Especially with the 2020 findings, the axion is growing in popularity as a dark matter candidate. But no one has yet "caught" an axion by directly detecting the particle in an accelerator like the LHC.

"We suspect it is a new particle we don't know about, and the axion could be that particle," Benjamin Safdi said about dark matter. "It could be created in abundance in the Big Bang and be floating out there explaining observations that have been made in astrophysics."

Scientists have proposed a number of possible experiments that could be used to try and "catch" an axion, but, as researchers described in a 2018 CERN statement, the LHC can be used to search for a new, hypothetical particle: the QCD axion. 

Even though physicists haven't yet "caught" either the axion or this similar variety, it's possible that future experimentation with the LHC might shed new light on this particle mystery, potentially confirming scientists' suspicions about the axion or finding new information that changes existing ideas entirely. 

"Ghost particles"

Neutrinos, nicknamed "ghost particles" because of their elusive nature, were spotted for the first time in a particle accelerator in 2021. The discovery was made at the LHC and was a major breakthrough for physics that has opened up a whole world of subatomic mysteries.

Neutrinos are subatomic particles similar to electrons with no electrical charge and such a small mass that scientists used to think they had no mass at all. Neutrinos are thought to be one of the most prevalent particles in the entire universe; every second, about 100 billion neutrinos pass through every square centimeter of the human body and these particles, produced in the hearts of stars through nuclear fusion, are just about everywhere.

But, because neutrinos don't interact much with matter (neutrinos only interact via gravity and the weak force) and because of their lack of charge and tiny mass, they have been remarkably difficult to spot in particle accelerators. 

LHC's landmark 2021 detection changed that, and with this big "first" accomplished, the LHC can now push this science forward, further exploring these ghostly particles that permeate our universe. 

Supersymmetry

Supersymmetry is a fundamental mystery of the universe that continues to lurk in the back of scientists' minds. 

Simply put, supersymmetry is a theory suggesting that all of the universe's fundamental particles should have counterpart theoretical "superparticles." This theory, which is an extension of the Standard Model, says that when elementary particles (like photons or electrons) were formed at the beginning of the universe, they were created alongside matching "superparticles." The theory suggests that every particle seen in the Standard Model has a partner particle that spins differently. 

However, there has been no concrete, direct evidence of supersymmetry. 

Scientists hope that, by using a facility like the LHC, as astrophysicist Paul Sutter has explained, scientists could essentially recreate the conditions of the early universe and search for signs of supersymmetry. 

"If the theory is correct, supersymmetric particles should appear in collisions at the LHC," CERN said in a statement. Scientists have previously wondered whether the LHC is creating supersymmetric particles that are escaping the detector then decaying. And since experiments at the LHC like ATLAS, the largest general-purpose experiment at the LHC, detect particles' decay and the products of that decay rather than the particles directly, physicists remain concerned about how these particles could be detected if they are indeed there. 

But with this mystery lingering, it makes new opportunities for exploration with the LHC all the more exciting. 

The matter-antimatter problem

One of the biggest mysteries in science remains what is known as "matter-antimatter asymmetry."

As we understand it, the Big Bang should have created nearly equal amounts of matter and antimatter in the early universe. (Antimatter particles have the same mass as their counterpart matter particles, but with an opposite electric charge.) But the universe today appears to be primarily composed of matter, with very little antimatter. This mystery asks: what happened? 

Scientists believe that the Big Bang created a "nearly" equal amount of antimatter and matter because if there was the exact same amount, the two types would have essentially canceled one another out, leaving behind an empty universe, CERN has described.

But that slight asymmetry between matter and antimatter at the Big Bang isn't fully explained by the Standard Model and physicists are also unsure how this slight asymmetry led to the matter-dominated universe that we live in today.

With the LHCb (Large Hadron Collider beauty) experiment, scientists have investigated slight differences between matter and antimatter. Most recently, earlier in 2022, the largest matter-antimatter asymmetry was observed with this experiment. Future investigation could reveal new details about why and how our universe came to be. 

Mystery particles

If the world's largest and most powerful particle accelerator is good at one thing, it's smashing particles together. This technology has enabled incredible steps forward in the field of particle physics, including creating and observing strange, new particles that scientists had only suspected might exist.

From 2011 to 2021, scientists using the LHC discovered 59 new types of hadron particles. Among those, in 2018, was a strange "mystery particle"; in 2021, a rare four-quark "tetraquark" particle, a non-elementary particle, was spotted at the LHC. And, of course, the Higgs boson discovery at the LHC certainly counts as a remarkable particle find. 

As researchers continue to smash protons near the speed of light and explore the fringes of what we know to be true about the universe, it's likely that strange, new particles will continue to pop up during the LHC's new operational phase. 

The Standard Model

The last item on this list is almost an honorable mention, but it remains one of the most significant, all-encompassing objectives that scientists use the LHC to investigate.

The Standard Model describes all known forces and particles in the universe; it's the best "theory of everything" that scientists have to work with. But the Standard Model isn't complete and, as we explore major unknowns like dark matter and dark energy, researchers continue to explore how they might need to extend the Standard Model. 

The LHC, allows scientists to both confirm what we already suspect about the Standard Model and also see where the model falls short, whether physicists may need to extend the theory or break the model apart altogether.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

After nearly 13.8 billion years of nonstop expansion, the universe could soon grind to a standstill, then slowly start to contract, new research published in the journal Proceedings of the National Academy of Sciences suggests.

In the new paper, three scientists attempt to model the nature of dark energy — a mysterious force that seems to be causing the universe to expand ever faster — based on past observations of cosmic expansion. In the team's model, dark energy is not a constant force of nature, but an entity called quintessence, which can decay over time.

The researchers found that, even though the expansion of the universe has been accelerating for billions of years, the repellent force of dark energy may be weakening. According to their model, the acceleration of the universe could rapidly end within the next 65 million years — then, within 100 million years, the universe could stop expanding altogether, and instead it could enter an era of slow contraction that ends billions of years from now with the death — or perhaps the rebirth — of time and space.

And this could all happen "remarkably" quickly, said study co-author Paul Steinhardt, Director of the Princeton Center for Theoretical Science at Princeton University in New Jersey.

"Going back in time 65 million years, that's when the Chicxulub asteroid hit the Earth and eliminated the dinosaurs," Steinhardt told Live Science. "On a cosmic scale, 65 million years is remarkably short."

Nothing about this theory is controversial or implausible, Gary Hinshaw, a professor of physics and astronomy at the University of British Columbia who was not involved in the study, told Live Science. However, because the model hinges on past observations of expansion alone — and because the present nature of dark energy in the universe is such a mystery — the predictions in this paper are currently impossible to test. For now, they can only remain theories.

Energy of the void

Since the 1990s, scientists have understood that the expansion of the universe is speeding up; the space between galaxies is widening faster now than it was billions of years ago. Scientists named the mysterious source of this acceleration dark energy — an invisible entity that seems to work contrary to gravity, pushing the universe's most massive objects farther apart rather than drawing them together.

Though dark energy makes up approximately 70% of the total mass-energy of the universe, its properties remain a total mystery. A popular theory, introduced by Albert Einstein, is that dark energy is a cosmological constant — an unchanging form of energy that's woven into the fabric of space-time. If that's the case, and the force exerted by dark energy can never change, then the universe should continue expanding (and accelerating) forever.

However, a competing theory suggests that dark energy doesn't need to be constant in order to fit with observations of past cosmic expansion. Rather, dark energy may be something called quintessence — a dynamic field that changes over time. (Steinhardt was one of three scientists who introduced the idea in a 1998 paper in the journal Physical Review Letters.)

Unlike the cosmological constant, quintessence can be either repulsive or attractive, depending on the ratio of its kinetic and potential energy at a given time. Over the last 14 billion years, quintessence was repulsive. For most of that period, though, it contributed insignificantly to the expansion of the universe compared to radiation and matter, Steinhardt said. That changed about five billion years ago when quintessence became the dominant component and its gravitational repulsion effect caused the expansion of the universe to speed up.

"The question we're raising in this paper is, 'Does this acceleration have to last forever?'" Steinhardt said. "And if not, what are the alternatives, and how soon could things change?"

The death of dark energy

In their study, Steinhardt and his colleagues, Anna Ijjas of New York University and Cosmin Andrei of Princeton, predicted how the properties of quintessence could change over the next several billion years. To do this, the team created a physical model of quintessence, showing its repellent and attractive power over time, to fit with past observations of the universe's expansion. Once the team's model could reliably reproduce the universe's expansion history, they extended their predictions into the future.

"To their surprise, dark energy in their model can decay with time," Hinshaw said. "Its strength can weaken. And if it does so in a certain way, then eventually the antigravitational property of dark energy goes away and it transitions back into something that's more like ordinary matter."

According to the team's model, the repellent force of dark energy could be in the midst of a rapid decline that potentially began billions of years ago.

In this scenario, the accelerated expansion of the universe is already slowing down today. Soon, perhaps within about 65 million years, that acceleration could stop altogether — then, within as few as 100 million years from now, dark energy could become attractive, causing the entire universe to start contracting. In other words, after nearly 14 billion years of growth, space could start to shrink.

"This would be a very special kind of contraction that we call slow contraction," Steinhardt said. "Instead of expanding, space contracts very, very slowly."

Initially, the contraction of the universe would be so slow that any hypothetical humans still alive on Earth wouldn't even notice a change, Steinhardt said. According to the team's model, it would take a few billion years of slow contraction for the universe to reach about half the size it is today.

The end of the universe?

From there, one of two things could happen, Steinhardt said. Either the universe contracts until it collapses in on itself in a big "crunch," ending space-time as we know it — or, the universe contracts just enough to return to a state similar to its original conditions, and another Big Bang — or a big "bounce" — occurs, creating a new universe from the ashes of the old one.

In that second scenario (which Steinhardt and another colleague described in a 2019 paper in the journal Physics Letters B), the universe follows a cyclical pattern of expansion and contraction, crunches and bounces, that constantly collapse and remake it. If that's true, then our current universe may not be the first or only universe, but just the latest in an infinite series of universes that have expanded and contracted before ours, Steinhardt said. And it all hinges on the changeable nature of dark energy.

How plausible is all this? Hinshaw said the new paper's interpretation of quintessence is a "perfectly reasonable supposition for what the dark energy is." Because all of our observations of cosmic expansion come from objects that are millions to billions of light-years away from Earth, current data can only inform scientists about the universe's past, not its present or future, he added. So, the universe could very well be barreling toward a crunch, and we'd have no way of knowing until long after the contraction phase began.

"I think it really just boils down to how compelling do you find this theory to be and, more importantly, how testable do you find it to be?" Hinshaw added.

Unfortunately, there is no good way to test whether quintessence is real, or whether cosmic expansion has started to slow, Steinhardt admitted. For now, it's just a matter of fitting the theory with past observations — and the authors do that capably in their new paper. Whether a future of endless growth or rapid decay awaits our universe, only time will tell.

Originally published on Live Science.

The newly-upgraded Large Hadron Collider (LHC) just broke a world record with its proton beams.

The LHC, located at CERN near Geneva, Switzerland, restarted on Friday (April 22) after a planned, three-year hiatus during which a number of upgrades were made to the facility. These improvements are already being put to the test and, in restarting and preparing for its new operating phase, called Run 3, the LHC has already beaten a previous record. 

This particle accelerator is both the largest and most powerful in the world. And, in a test run conducted shortly after being switched back on, the LHC accelerated beams of protons to a higher energy than ever before.

"Today the two #LHC pilot beams of protons were accelerated, for the first time, to the record energy of 6.8 TeV per beam. After #restartingLHC, this operation is part of the activities to recommission the machine in preparation of #LHCRun3, planned for the summer of 2022," CERN tweeted today (April 25).

Related: The Large Hadron Collider will explore the cutting edge of physics after 3-year shutdown

The LHC works by accelerating two beams of particles like protons towards each other. These high-energy beams collide, allowing particle physicists to explore the extreme limits of our physical world and even discover aspects of physics never seen before. 

With the upgrades implemented during the planned shutdown, the energy of the LHC's proton beams was set to increase from 6.5 teraelectronvolts (TeV) to 6.8 TeV. For reference, one teraelectronvolt is equivalent to 1 trillion electron volts and, in terms of kinetic energy, is roughly equal to the energy of a mosquito flying. While this might seem like a very small amount of energy, for a single proton it is an incredible amount of energy.

The LHC facility is used to explore cosmic mysteries ranging from investigating possible candidates for dark matter to completely breaking apart our understanding of physics. Now both switched on and working as intended with the new upgrades, the LHC is well on its way to enabling a new round of groundbreaking physics research.

Email Chelsea Gohd at cgohd@space.com or follow her on Twitter @chelsea_gohd. Follow us on Twitter @Spacedotcom and on Facebook.

Scientists overseeing the largest particle accelerator on Earth switched it on for the first time in three years this weekend to solve some of the biggest mysteries in physics. 

The Large Hadron Collider (LHC), the powerful particle accelerator located at CERN near Geneva, Switzerland, restarted on Friday (April 22) after a three-year shutdown for maintenance and upgrades. The reactivation kicked off what scientists call Run 3, the LHC's third science run, which will perform experiments through 2024. 

"The machines and facilities underwent major upgrades during the second long shutdown of CERN’s accelerator complex," Mike Lamont, CERN's Director for Accelerators and Technology, said in a statement Friday. "The LHC itself has undergone an extensive consolidation programme and will now operate at an even higher energy and, thanks to major improvements in the injector complex, it will deliver significantly more data to the upgraded LHC experiments." Those experiments will build on LHC's discoveries during its Run 1 (2009-2013) and Run 2 (2015-2018).

Related: Large Hadron Collider will explore the cutting edge of physics after 3-year shutdown

For its reactivation, scientists fired up the LHC's 16.7-mile-long ring (27 kilometers) to inject two beams of protons in opposite directions at an energy level of 450 billion electronvolts. That's just an appetizer for even higher energy levels LHC will operate at once it reaches its target of a mind-blowing 13.6 trillion electronvolts for Run 3, scientists said.

"These beams circulated at injection energy and contained a relatively small number of protons. High-intensity, high-energy collisions are a couple of months away,” said Rhodri Jones, who leads CERN's Beams department, in the statement.  "But first beams represent the successful restart of the accelerator after all the hard work of the long shutdown."

LHC's three-year shutdown allowed scientists to make substantial upgrades to four key experiments on the particle accelerator. It's ATLAS and CMS detectors detectors alone will receive more particle collisions than the past two runs combined, according to CERN. ATLAS (short for A Toroidal LHC Apparatus) detects the tiny subatomic fragments from particle collisions and is used to hunt for the Higgs Boson, dark matter and extra dimensions. CMS (short for Compact Muon Solenoid) is a general-purpose detector that uses different systems for observations similar to ATLAS.

In addition to ATLAS and CMS, the particle accelerator's ALICE experiment for heavy-ion collisions will be able to detect 50 times more collisions thanks to its upgrade, while another instrument, called LHCb, will see its detection capability increase by a factor of three, according to CERN. 

"The unprecedented number of collisions will allow international teams of physicists at CERN and across the world to study the Higgs boson in great detail and put the Standard Model of particle physics and its various extensions to the most stringent tests yet," CERN officials wrote in the statement.

Two new experiments will be activated on LHC for Run 3. Called the Forward Search Experiment (FASER) and the Scattering and Neutrino Detector at the LHC (SND@LHC), they are expected to explore new physics beyond the Standard Model, measure how often antimatter forms and explore the physics of cosmic rays and a strange state of matter called quark-gluon plasma.

It will take several weeks of commissioning work before the revamped LHC will be ready for actual science measurements. Those science runs are expected to begin in the summer, CERN officials have said. 

Once Run 3 concludes in 2024, CERN scientists will shut it down for another planned overhaul that will include more upgrades for the massive particle accelerator. Once complete, those upgrades will allow scientists to rename LHC the "High Luminosity Large Hadron Collider" once it reopens in 2028.

Email Tariq Malik at tmalik@space.com or follow him @tariqjmalik. Follow us @Spacedotcom, Facebook and Instagram.

As the early universe cooled shortly after the Big Bang, bubbles formed in its hot plasma, triggering gravitational waves that could be detectable even today, a new study suggests.

For some time, physicists have speculated that a phase transition took place in the early universe shortly after the Big Bang. Phase transition is a change of form and properties of matter that usually accompanies temperature changes such as the evaporation of water into vapor or the melting of metal. In the young and fast expanding universe, something similar likely took place as the plasma, which was filling the space at that time, cooled down. 

The phase transition in the early universe, however, was quite remarkable, triggering gravitational waves, ripples in spacetime that are most commonly caused by collisions between massive bodies such as black holes and neutron stars. Moreover, the gravitational waves triggered by the early universe's phase transition were so powerful that they might be detectable with the future U.S./European Laser Interferometer Space Antenna (LISA) space mission, according to scientists from the University of Helsinki in Finland.

Related: Here's how the universe could end in a 'false vacuum decay'

In the new study, the scientists model how these gravitational waves could produce a signal that would be detectable by LISA using a technique known as holographic duality. 

Holographic duality is based on string theory and enables scientists to mathematically describe the behavior of particles in gravity and gravity-free environments. 

Using this technique, the scientists could analyze the likely events that followed phase transitions in the early universe. Their model took into account the temperature at which the transition was likely taking place, as well as the rate of the universe's expansion.

Since no one was around to observe these early universe phase transitions when they were taking place, the process is still very much shrouded in mystery. Scientists think as the hot plasma cooled down, bubbles started to form in it as part of the so-called nucleation process. Nucleation is the first step in the transition between phases (such as from water to vapor or from water to ice)  when bubbles form in the original medium that act as centers of the transitioning process.

But these bubbles, scientists think, collided with each other in the transforming universe, triggering the measurable gravitational waves. 

It will, however, still take some time to unravel this mysterious process. LISA, a collaboration between the European Space Agency (ESA) and NASA, is not expected to launch before 2037. LISA will be the first mission dedicated to recording gravitational waves, according to ESA, and it will be able to pick up small fluctuations in spacetime created by colliding black holes and supernovae. If it finds the signals proposed in the research, it will be the first evidence to back up wide speculation of early universe phase transitions.

The study was published in the journal Physical Review Letters in March.

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