Currently, there are countless stars and galaxies shining in the universe, but how much matter actually exists? The question is quite simple, but the answer turns out to be quite a headache.
The main reason this dilemma exists is that current cosmological observations simply do not agree on how matter is distributed in the current universe.
A new computer simulation that tracks how all the elements of the universe – ordinary matter, dark matter and dark energy – evolve according to the laws of physics could help. Breathtaking visuals virtually show galaxies and galaxy clusters, macrocosmis powered by the so-called cosmic web. This web is largest structure in the universeconstructed of filaments composed of both regular or baryonic matter; dark matter.
Unlike previous simulations that only considered dark matter, the new study carried out by a project called FLAMINGO (abbreviation for All-Water Large-Scale Structure Simulation with All-Sky Mapping for the Interpretation of Next Generation Observations) considers ordinary matter will also be tracked.
Related: Are we living in a simulation? The problem with this surprising hypothesis.
“Dark matter dominates gravity, but the contribution of ordinary matter can no longer be ignored,” Joop Schaye, a professor at Leiden University in the Netherlands and co-author of three new studies on the FLAMINGO project, said in the paper. Ta. statement.
Astronomers say that computer simulations like this one not only provide cosmic eye candy, but also reveal a major discrepancy in cosmology called the S8 tension. He said it would also be an important piece of research to help determine the cause. It is a discussion about how matter is distributed in the universe.
What is S8 tension?
When investigating the universe, astronomers sometimes use what is known as the S8 parameter. This parameter essentially characterizes how “clumpy” or strongly clustered all the matter in our Universe is, and can be precisely measured by so-called low-redshift observations.used by astronomers redshift Measure distance from an object earthand low redshift studies such as “weak” gravity lens “Investigations” can reveal processes unfolding in a distant and therefore older universe.
However, the value of S8 can also be predicted using the following method: standard model of cosmology. Scientists can essentially adjust their models to match known characteristics. space microwave background (CMB), this is the radiation left over from the Big Bang, from which we calculate the lumpiness of matter.
So, here’s the problem.
These CMB experiments found higher S8 values than weak gravitational lensing surveys. And cosmologists don’t know why. They call this discrepancy S8 tension.
In fact, the S8 tension is creating a crisis in cosmology that is a little different than its more famous cousins. hubble tensionwhich refers to the contradiction that scientists face in determining the rate of expansion of the universe.
Why it’s such a big deal that the team’s new simulations don’t provide an answer to the S8 tension is that unlike previous simulations that only considered dark matter’s influence on the evolving universe, the latest study uses normal matter This is because the effects of . In contrast to dark matter, ordinary matter is governed by: gravity So is the pressure from gases throughout the universe. For example, Galaxy Wind is supernova Explosions and active accretion supermassive black hole An important process that redistributes matter by blowing particles of ordinary matter into galaxies. space.
But this new study’s consideration of ordinary matter and some of the most extreme galactic winds was not enough to explain the weak clumps of matter observed in the universe today.
“I’m at a loss here,” Hsieh told Space.com. “An interesting possibility is that this tension points to a flaw in the Standard Model of cosmology, and even the Standard Model of physics.”
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Unusual physics or flawed model?
So where did this S8 tension come from?
“We don’t know, but that’s what makes this so interesting,” said Ian McCarthy, a theoretical astrophysicist at Liverpool John Moores University in the UK and co-author of the three new studies. “We’re doing it,” he told Space.com.
But computer simulations like the one FLAMINGO ran could bring us one step closer. Grand virtual maps of the universe could help identify possible errors in current measurements, so they could help reveal the cause of the S8 tension. For example, astronomers have argued that this problem may be due to general uncertainties in observations of large structures, or the fact that it may be related to problems with the CMB itself. We are gradually eliminating more commonplace explanations for the problem.
In reality, the team suspects that the effects of ordinary matter are probably much stronger than in current simulations. But that also seems unlikely, since the simulations match the observed properties of galaxies and galaxy clusters very well.
“All of these possibilities are very exciting and have important implications for fundamental physics and cosmology,” McCarthy said. But the most interesting possibility is that the standard model is somehow wrong.
For example, dark matter may have exotic self-interacting properties not considered in the Standard Model. S8’s tension could signal a collapse of the theory of gravity on the largest scale, McCarthy said.
Nevertheless, the latest simulations show that ordinary matter and neutrino Both are known to be important for accurately predicting how galaxies evolve over time, but the tension in S8 was not resolved.
This is the ultimate headache. At low redshifts, the Universe is much less bumpy than predicted by the Standard Model.However, measurements to explore the structure of the universe are while The CMB and low-redshift measurements are “perfectly consistent with standard model predictions,” McCarthy said. “The universe appears to have behaved as expected for a large part of its history, but something seems to have changed later in the universe’s history.”
Perhaps the key to resolving the S8 tension lies in the answer to what exactly caused the change.