As far as cosmologists can tell, the mysterious force behind the accelerated expansion of the universe, a force that we call dark energy, remains constant.
But that's today. It's entirely possible that dark energy changed in the past, according to new research, and those changes may have flooded the universe with the particles of our everyday lives, the scientists behind the new research suggested.
Let's start with the present: Something strange is happening to the cosmos. It's expanding, but it's also full of matter. The gravitational attraction of all that stuff ought to be slowing down that expansion of the universe as time goes on.
Related: Amazing photos from dark energy camera in Chile
And yet, the expansion isn't slowing down. It's not even staying at the same rate. It's getting faster.
Every day that goes by, our universe gets bigger and bigger, faster and faster. Cosmologists call this accelerated expansion "dark energy," in part because we basically have no idea what's causing it, where it came from or what it will do in the future. All we know is that starting about 5 billion years ago, dark energy turned on and stayed on.
We also know that during those 5 billion years, dark energy’s “strength” (as measured by its density) has stayed pretty constant. It doesn't appear to be getting weaker or stronger with time, making it a cosmological constant.
But the early universe was a much stranger place, and much stranger things could have happened long ago. And if they did happen, they could have had massive consequences for the rest of cosmic history.
And then there was light
While we barely understand the nature or cause of dark energy, we do know that it can't do much more than accelerate the expansion of the universe. That's because, nowadays, the universe is — cosmologically speaking — old, cold and mostly dead.
This big-picture retirement means that there isn't a lot of energy (dark or otherwise)to go around. If dark energy did something funky now, like change over time, it wouldn't have a big effect, because dark energy is already incredibly feeble. Yes, it’s accelerating the expansion of the universe, but only mildly, which is why it took us so long to identify its effects in the first place. This weakness limits both what dark energy can do today and what we can learn about it; there just aren't a lot of effects for cosmologists to measure. But the early universe was much hotter, denser, more compact and, most especially, more energetic.
And while dark energy emerged onto the cosmic scene about 5 billion years ago, that wasn't necessarily its first appearance. Dark energy could have been alive and kicking in the young cosmos, doing all sorts of interesting things before temporarily subsiding into the background. Recently, a team of theoretical physicists pondered what such early dark energy could have done, reporting their results in November 2019 in a paper they uploaded to the preprint server arXiv.org.
The researchers found that a brief fluctuation in dark energy could have flooded the early universe with exotic particles like quarks, gluons and leptons that would eventually congeal into the atoms we know and love today.
A better universe
According to those researchers, this flood must have happened after inflation, when the very early universe grew incredibly large in a very short amount of time. After this inflation, the universe was altogether empty; all of the preinflation ooze was simply blown away like dust in the wind. Something had to come after that to "reheat" the cosmos, bringing in a fresh round of particles to the universe in what we commonly think of as "the Big Bang."
Most theorists think that whatever caused inflation itself must have also generated the reheating, but this new work suggests that early dark energy could have created the flood of particles by losing its own energy. It's an interesting story, but the scientists' hypothesis still has to fit with the observations that cemented our understanding of the Big Bang and inflation in the first place. If dark energy is responsible for the universe's reheating, then we should see subtle changes to the standard picture’s model of the cosmic microwave background, which in turn influences the pattern of galaxies in the modern universe.
So far, the new model of reheating matches all current observations, a bit better, even, than traditional theories of inflation do. But we don't really have enough information to tell whether that's just a statistical fluke.
New generations of astrophysics tools, like NASA's Wide Field Infrared Survey Telescope (WFIRST), might help scientists better understand dark energy and its role in the young universe and today's cosmos.
- The history & structure of the universe (infographic)
- Alternatives to the Big Bang theory explained (infographic)
- Cosmic microwave background: Big Bang relic explained (infographic)
Paul M. Sutter is an astrophysicist at The Ohio State University, host of "Ask a Spaceman" and "Space Radio," and author of "Your Place in the Universe." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights.
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Very interesting how the new physics is explaining the cause of the Big Bang event now. After reading, it would be good to see a timeline here. Before the BB event, BB event, and moments just after the BB event. Is the dark energy that floods the early universe with exotic particles that evolve into atoms (exactly what atoms on the Periodic Table for example), when does this creation event take place? After inflation is indicated but we have the Planck time, Planck length, and evolution of the universe that followed and one second after the BB event, the matter vs. anti-matter destruction of everything too. It seems the new physics goes back before the Planck time and perhaps smaller than the Planck length now, at least it may. James Peebles had something to say about the new math explaining the BB event. ‘Top cosmologist's lonely battle against 'Big Bang' theory’ "One of these theories is known as the "inflation model," which holds that the early universe expanded exponentially fast for a tiny, tiny fraction of a second before the expansion phase. "It's a beautiful theory," said Peebles. Many people think it's so beautiful that it's surely right. But the evidence of it is very sparse."
When it comes to *sparse* evidence, I compare the new cosmology to the debate between geocentric teaching and heliocentric solar system and what type of science won the day and changed the paradigm. For example, I find the measurements for the solar parallax (that determined the astronomical unit) using transits of Venus and Mercury with telescopes more reliable and verifiable than the new cosmology doctrine that explains what was there before the BB event and how the BB event took place.
It is basically very supernumerary since inflation makes the same predictions, and ad hoc to better suit the observations.
The only reason to raise it now is since there is a tension in observations of expansion rate, which roughly divide between methods looking at the local - or youngest - data and global - heavily weighted with oldest - data. And one early suggested, suitable and simple ad hoc for that is that dark energy had a temporary early extra component. But that, and/or the application here, is still very weak in nature.
When you say "Big Bang event" you define it as the start of the Hot Big Bang era P1Q8tS-9hYoView: https://www.youtube.com/watch?v=P1Q8tS-9hYo]. I think modern cosmologists like Paul Sutter here, or Matt O'Dowd @ PBS Space & Time, prefer to define big bang as the later, lower expansion rate period we still live in. The last Planck team cosmology parameter integration managed to discern that inflation is naturally eternal (i.e. slow roll) and so of indefinite - likelier eternal - extent . The video link above reflect that, and explain why the Planck scale is irrelevant since slow roll happens at 10^-5 that energy scale. The inflation energy release process is described in O'Dowd's videos xJCX2NlhdTcView: https://www.youtube.com/watch?v=xJCX2NlhdTc; chsLw2siRW0View: https://www.youtube.com/watch?v=chsLw2siRW0].
Robustness and uncertainty of the observations is not a problem for inflation as much as the exact field model, it is claimed to be the modern consensus . As for robustness the above parameter integration saw it consistently with two independent methods (cosmic background spectra of spot size respectively spot polarities) as well as with both data combined, and it gives some preliminary inkling of how the field behaved. And the uncertainty is at the modern cosmology or down towards parts of a percent. Even if the last, outstanding data tension of expansion rate may upend some parts of cosmology - unlikely - the background spectra show flatness of space, and inflation as the cause of that flatness, so it seems fairly safe. I see that while early solar parallax measurements were robust they did not have at all that low uncertainty (to say the least) https://en.wikipedia.org/wiki/Heliocentrism ]. All those problems - robustness, uncertainty and what models apply - instead append to the Hot Big Bang era. Even if Planck can see that inflation had a natural exit - it quickly releases energy as the system slosh around after exit from inflation - I believe there are questions about non-linear couplings to gravity since the energy scale is still high (as such couplings would release heat faster). And above all which phase transitions happened as the quantum fields froze out, i.e. which forces and which particles appeared when (say, dark matter).
Expansion rate is measured in many ways. Planck 2018 cosmology parameter paper @ Planck Legacy Archive is an older synthesis:
https://pla.esac.esa.int/#home -> https://www.cosmos.esa.int/web/planck/publications -> https://www.cosmos.esa.int/web/planck/publications#Planck2018 -> https://arxiv.org/abs/1807.06209
History of expansion rate measurements:
The latest public review:
I would start with the history since it has an introductory image showing how it started out like the solar parallax large errors but converged (or not) since modern, high precision cosmology arrived. Then read the latest insight. Planck cosmology is more advanced, for the whole picture (albeit you may want to read a Wikipedia entry on Hubble rate before that since Planck integration is with Planck data front and center). Good luck!
Others say inflation is not proven at this time. https://astronomy.com/magazine/2018/07/inflation-leaves-its-mark, “With inflation, the number of observational quantities we have is limited,” says Marc Kamionkowski, a professor and theoretical physicist at Johns Hopkins University. “Therefore, it limits the level of detail at which the model or theory can be specified...In the past four decades, inflation has become a central pillar around which cosmology is organized. But while it tidies up outstanding problems with the Big Bang theory, it remains unverified. And the lack of evidence leaves some scientists with reservations. “It’s had incredible success at describing what we see . . . and people talk about it as the only option, but many theorists think that we should be considering other options for what happened in the early universe,” Dunkley says. “I think it’s unlikely that it happened exactly the way we’ve been thinking about it. I don’t think we’ve got the whole story yet.” For now, inflation remains cosmologists’ best theory to explain the current structure and infancy of our universe. Perhaps it will be another half-century before scientists have a clearer understanding of what happened in the universe’s first breaths."
Here is the key concerning inflation in cosmology "...it remains unverified". The solar parallax is verified and verifiable today, just like the measurement was in the 1700s using Venus or Mercury transits across the Sun or even later observations.
I'm not sure what expansion rate you are discussing now, since you mention inflation. This is by the way a basic reason, I think, why astrophysicists separate between the inflation era with high expansion rate and the big bang era with low expansion rate, we are talking different expansion rates as well as measurements.
I was earlier discussing only the low expansion rate ("Hubble rate") earlier, and the ESA image show that it wasn't very well observed and understood until the the late 90's - early 00's https://en.wikipedia.org/wiki/Hubble's_law ]; I hear by the way it was Freedman, from the Quanta article, which did the first solid observation so she is a solid rock in a stormy sea then and now. The point with the ESA figure and Quanta article is that this rate is measured in many independent ways so can be trusted.
The 3D expansion - which means the universe is homogeneous (alike at every distance) and isotropic (same laws at every spatial direction) - is a basic observation and theory result from LCDM cosmology. It is also verified differently such as by galaxy redshift and spectroscopy surveys, but the best evidence is the whole sky data from the cosmic background. After removing the solar system velocity in respect to the background photon reference frame, it shows the universe and its laws are homogeneous and isotropic to 1 part in 10^-5.
This homogeneity and isotropy also carries over to the earlier inflation era, where the best evidence for the high expansion rate is that space is spatially flat, that it is homogeneous and isotropic, and that there are no funny "cosmic strings" or odd "magnetic monopoles" and other possible physics theory defects. The exact inflation era rate (as well as minimal duration) observations are iffy - see the Planck papers - but as I pointed out the 2018 integration has two independent data sets they use which agree in every possible combination.
As I said on inflation, it seems to be the (new) consensus. If you can't accept it, that is fine - though it can make it hard to understand modern cosmology. The "unverified" claim in the article is the last out of 6 possible ways to test it (more or less 6 parameters or outcomes to test it on), and it is uncertain that last test can be done at all. The consensus has moved on - the tests are considered enough: it is verified- I take it - in the eyes of the consensus. That arguably leaves "unverified" as sophistry. If you want to be funny and return some sophistry of your own, you can say that "unverified" is an unverified claim. :-D
So I read the paper as I should in the first place, and it is not supernumerary in all senses. It is a suggestion of a possible energy exchange between vacuum and matter sectors in the very early universe, right after baryons have frozen out, so it does not add new fields as much as asks for constraining possible theory effects. And while it is the Hubble rate tension that motivates them, their fitted model predicts the lowest scales of the matter power spectrum (how much baryon matter at different scales, I think) better than LCDM. The lowest scales of the cosmic background spectra has some deviation, i.e. the largest background spatial spots of temperature variation differs from predictions, and if the largest matter "spots" becomes better predicted maybe that helps.
That said, they have to exclude exchange with dark matter, so assume it is a GUT scale remnant and hence already decoupled from the vacuum (too high energy to be easily created by the exchange). That is, the forces (except gravity) are unified at high enough energy and the remnants seem to leave topological defects https://books.google.se/books?id=oTzwCAAAQBAJ&pg=PA495&lpg=PA495&dq=GUT+energy+scale+remnants&source=bl&ots=Poemv7hrWR&sig=ACfU3U3VvrsgMkMFEg6viSpzmAXlE--KRQ&hl=sv&sa=X&ved=2ahUKEwiMibWP7YXoAhUvposKHQESD68Q6AEwAnoECAcQAQ#v=onepage&q=GUT%20energy%20scale%20remnants&f=false ]. But GUT would mean protons decay, which is not seen.
Inflation is very different than the cosmological redshift interpretation of light, it depends upon quantum gravity, inflatons, and inflation field(s) as well as 3D space expanding >> c. The cosmological redshift interpretation of light from galaxies dating back to the days of Edwin Hubble et al, as far as I know has no direct method of verification like lab experiments showing photons redshift as the photons travel through 3D space stretching. The same can be asked about space probes like New Horizons sending information back to Earth over some 47 AU distance. The cosmological redshift interpretation, is an *interpretation of the redshift observed* based upon GR using the principle of equivalence and the favored interpretation as you said is "LCDM cosmology". Unlike the displacement of stars near the Sun during a total solar eclipse that was predicted by Einstein and tested numerous times since 1919 (including August 2017 total solar eclipse across the USA), the redshift of photons passing through 3D space has no direct measurement to show this is true, other than an interpretation using GR to understand the galaxy redshifts documented since Edwin Hubble days. This type of test is circular. When you examine the history of cosmology, George Gamow and Ralph Alpher are the fathers of the Big Bang and predicted a very different temperature to the primordial universe than what was found in the mid-60s, proclaimed as the evidence for George Gamow and Ralph Alpher model. The CMB temperature variations have been reworked in cosmology ever since to explain various problems uncovered and the CMB is the primary testbed vs. other objects in the universe. A serious issue in the Big Bang model that forced the acceptance of inflation cosmology was the horizon problem in the Big Bang model. Special Relativity places a speed limit on the temperature smoothness that could evolve during the expanding universe and what should be observed today. The measured CMBR near 3 Kelvin and the smoothness does not match this (just look at George Gamow work), we should see a very lumpy CMBR today.
So, I consider the solar parallax measurements more verifiable and secure than inflation cosmology and the circular interpretation of the cosmological redshift used today. However, I do like the cosmological interpretation for galaxy redshifts.
Or dark matter just a property of the real universe quantum fluctuation and the rest just a product of it.
Final frontier just an illusion in and endless sea of universes following similar self regulated laws.
IMO quantum fluctuation is the universe and big bang just an event inside it.