New computer simulation of the universe escalates cosmology dilemma
We see countless stars and galaxies sparkling in the universe today, but how much matter is actually there? The question is simple enough — its answer, however, is turning out to be quite a head-scratcher
This dilemma exists largely because current cosmological observations simply disagree on how matter is distributed in the present-day universe.
Of some help could be a new computer simulation that traces how all elements of the universe — ordinary matter, dark matter and dark energy — evolve according to the laws of physics.
The breathtaking visuals virtually show galaxies, and clusters of galaxies, manifesting in the universe, fed by the so-called cosmic web.
This web is the largest structure in the universe, built with filaments made up of both normal matter, or baryonic matter, and dark matter.
Unlike previous simulations that only considered dark matter, the new work, carried out by a project called FLAMINGO (short for Full-hydro Large-scale structure simulations with All-sky Mapping for the Interpretation of Next Generation Observations), tracks ordinary matter too.
“Although the dark matter dominates gravity, the contribution of ordinary matter can no longer be neglected,” Joop Schaye, a professor at Leiden University in the Netherlands and a co-author of the three new studies on the FLAMINGO project, said in a statement.
As for how much matter the universe really contains, astronomers say computer simulations like this one are not just great cosmic eye candy but also important probes to help pin down the cause of a major discrepancy in cosmology called the “S8 tension.” That’s the debate over how matter in the cosmos is distributed.
What is the S8 tension?
When investigating the universe, astronomers sometimes work with what’s known as the S8 parameter. This parameter basically characterizes how “lumpy,” or strongly clustered, all the matter in our universe is, and can be measured precisely with what are known as low-redshift observations.
Astronomers use redshift to measure how far an object is from Earth, and low-redshift studies like “weak gravitational lensing surveys” can illuminate processes unfolding in the distant, and therefore older, universe.
But S8’s value can also be predicted using the standard model of cosmology; scientists can essentially tune the model to match known properties of the cosmic microwave background (CMB), which is the radiation leftover from the Big Bang, and calculate the lumpiness of matter from there.
So, here’s the thing.
Those CMB experiments find a higher S8 value than the weak gravitational lensing surveys. And cosmologists don’t know why — they call this discrepancy the S8 tension.
In fact, S8 tension is a brewing crisis in cosmology slightly different from its famous cousin: Hubble tension, which refers to the inconsistencies scientists face in pinning down the rate of expansion of the universe.
The reason it’s a big deal that the team’s new simulation doesn’t offer an answer to S8 tension is, unlike previous simulations that only considered the effects of dark matter on an evolving universe, the latest work takes into account the effects of ordinary matter too.
In contrast to dark matter, ordinary matter is governed by gravity as well as pressure from gas across the universe. For example, galactic winds driven by supernova explosions and actively accreting supermassive black holes are crucial processes that redistribute ordinary matter by blowing its particles out into intergalactic space.
However, even the new work’s consideration of ordinary matter as well as some of the most extreme galactic winds was not sufficient to explain the weak clumping of matter observed in the present-day universe.
“Here I am at a loss,” Schaye told Space.com. “An exciting possibility is that the tension is pointing to shortcomings in the standard model of cosmology, or even the standard model of physics.”
Exotic physics or a flawed model?
So, where did this S8 tension originate?
“We don’t know, which is what makes this so exciting,” Ian McCarthy, a theoretical astrophysicist at Liverpool John Moores University in the U.K. and the co-author of three new studies, told Space.com.
Computer simulations, however, like those carried out by FLAMINGO could be bringing us a step closer. They may help reveal the cause of S8 tension because a grand, virtual map of the cosmos might assist with identifying possible errors in our current measurements.
For example, astronomers are slowly ruling out more mundane explanations for the issue, such as the fact it could be due to general uncertainties in observations of large-scale structures or related to a problem with the CMB itself.
In reality, the team speculates, perhaps the effects of normal matter are a lot stronger than in current simulations. That too seems unlikely though, as simulations agree very well with observed properties of galaxies and galaxy clusters.
“All of these possibilities are extremely exciting and have important implications for fundamental physics and cosmology,” said McCarthy. The most exciting possibility, however, “is the Standard Model is incorrect in some way.”
For example, dark matter could have exotic self-interacting properties not considered in the standard model — the S8 tension may be signaling a breakdown of our theory of gravity on the largest scales, McCarthy said.
Nonetheless, while the latest simulations track effects of normal matter and subatomic particles known as neutrinos — both of which are found to be important to make accurate predictions of how galaxies evolve across eons — they did not resolve the S8 tension.
Here’s the ultimate head-scratcher: At low-redshifts, the universe is significantly less lumpy than predicted by the standard model.
But measurements that probe structures of the universe between the CMB and low-redshift measurements are “fully consistent with standard model predictions,” McCarthy said. “It seems the universe behaved as expected for a significant fraction of cosmic history, but that something changed later on in cosmic history.”
Maybe the key to resolving the S8 tension lies in the answer to what, exactly, drove that change.
This research is described in three papers published in the journal Monthly Notices of the Royal Astronomical Society.
See more here space.com
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Tom
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Because computer models are created by limiting humans, they can never go into the “twilight” zone for answers. Every computer model will be bounded by human expectations and never be able to discover realities beyond their programming capabilities and inputs.
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Howdy
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How does one model something one does not understand, nor comprehend the vastness of?
Modelling a fish bowl doesn’t start to describe how the oceans work.
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VOWG
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Oh wow, a computer simulation, now where have we seen that before? Are you still taking your shots.
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VOWG
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I agree with both Tom and Howdy.
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Herb Rose
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If energy cannot be created or destroyed, only transferees to other matter, what happens to the greater than 99.999% of the light emitted by the sun that doesn’t strike matter in the solar system? It will keep traveling through space until it encounters matter. Light bends as it travels through magnetic fields of different strengths, causing it to changes direction as it travels through space (bending). The speed of light also changes as it travels through magnetic fields emitted by matter. A red shift is where light slows in a weakening magnetic field while a blue shift occurs when the strength of the magnetic field increases. (According to Planck, since the energy (v^2) of light is a function of frequency the velocity and energy of blue light shift increases with distance from the source.) It is the blurring of spectral lines (red and blue shifts) that indicate the distance the light has traveled, not the red shift. The matter we see in a telescope is multiple images of the same matter that have been emitted by an object and traveled different routes to our eyes.
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Jerry Krause
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Hi Fellow Commenters,
At her website Sharmila Kuthunu wrote: “In my past life, I trained as a computer science engineer in India and waddled in data science before switching to science journalism.” So she is no ordinary science journalist.
And Herb began: “If energy cannot be created or destroyed, only transferees to other matter, what happens to the greater than 99.999% of the light emitted by the sun that doesn’t strike matter in the solar system? It will keep traveling through space until it encounters matter.” He asked a question and it is my opinion that he gave a very valid answer.
However, he follows his answer with ” Light bends”. Light does not bend; it is refracted as it encounters matter. It seems he hasn’t tried to spear fish near the bottom of clear water and found that his spear comes no where near the fish one sees. Herb and others, we cannot explain any thing if deny the phenomenon which can be clearly seen.
I stop here because if Herb and any-others can not agree with my statement.
Have a good day
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herb Rose
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Jerry,
In matter energy equalizes with all the matter and the magnetic field in the matter is constant. This produces refraction where light in the matter travels in a straight line. In space the energy and magnetic fields are changing as the distance from the source changes. This causes the bending of light as it travels through these fields.
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Jerry Krause
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Hi Herb,
I have no idea what you mean by “In matter energy equalizes with all the matter.” And I believe (understood) that magnetic fields occur in space and not in matter. Will you please clarify how I am so badly misinformed?.
Have a good day
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Herb Rose
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Jerry,
If you add energy to an object that energy will be distributed to all parts of the object, producing a uniform temperature in the object. Energy flows from high to low trying to equalize. Think of what happens when you heat a pan of water.
Objects radiate the energy they contain in the form of magnetic and gravitational fields just like the protons and electrons in matter radiate electric fields. Does this mean there are no electric fields within matter?
How you can have such a complete lack of understanding about basic actions remains a mystery to us all.
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Jerry Krause
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Hi Herb,
I know I have drawn the following to your attention but I can not remember asking if you agreed with every thing that Feynman taught in this brief paragraph. So I ask you now for he did not refer to “magnetic and gravitational fields” or even electrons or protons..
“1–2Matter is made of atoms
If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.” (The Feynman Lectures On Physics, Cal Tech)
Have a good day
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Koen Vogel
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I have my own thoughts and could comment but if the astrophysicists are at a loss then it would be pretty presumptive of me to think I can confuse the issue any more with my musings. I am enormously pleased by the quote “An exciting possibility is that the tension is pointing to shortcomings in the standard model of cosmology, or even the standard model of physics.” In this age of post-normal science it is very refreshing to discover a devotee of the Scientific Method, whereby scientists attempt to falsify their pet theories, and get excited by the possibility that the standard model of physics is wrong. Hats off to Schaye.
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Jerry Krause
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Hi Herb,
I know I have drawn the following to your attention but I can not remember asking if you agreed with every thing he taught in his single sentence. So I ask you now for he did not refer to “magnetic and gravitational fields” or even electrons or protons.. Feynman only referred to atoms and their movements.
“1–2Matter is made of atoms
If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made of atoms—little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little imagination and thinking are applied.” (The Feynman Lectures On Physics, Cal Tech)
Have a good day
Reply
Herb Rose
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Jerry,
Electrons, protons, light, energy, gravity, alpha particles, gamma rays, and neurons are not made of atoms. Atoms are made from other things: energy and matter, which are indestructible, while atoms not only can be destroyed but also self destruct.
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Gary Brown
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Mar 17, 2020 Disaster Petroglyph, Mantle Mystery, Bad Day 4 Dark Matter | S0 News
Daily Sun, Earth and Science News
https://youtu.be/csFKsJPYZUk
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