How heavy is the universe? Conflicting answers hint at new physics.

rod

Oct 22, 2019
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"Potential "new physics" fixes to the standard model could involve changing the amount and nature of dark energy or dark matter—or both—as well as tweaks to how they interact with each other and with normal matter, among other more exotic modifications. "Some theoretical solutions to tinker with the cosmological model to fix the Hubble constant tension make this [sigma-eight tension] worse. Some make it better," Riess says. Hildebrandt agrees that there is no obvious solution in sight. "If there was a compelling model, maybe people would jump on that bandwagon," he says. "But at the moment, I don't think there is. It's really on us observers to improve the significance [of the sigma-eight tension] or disprove it."

This is an interesting article. Consider that about 4% of the universe is readily observable and as one source i have said, "That leaves only about 4% of reality accessible to observation." The other 96% remains a struggle in the BB cosmology.
 
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It's all swag right now with almost no experimental evidence. At least Einstein made predictions and suggested experiments that would either confirm or disprove his theories. So far General Relativity has held up well to experimentation with each year brining actual data that confirms his theories, the latest being a photograph of a black hole's event horizon in M87. Quantum mechanics is still very much theory with little experimental evidence. Same goes for dark energy and dark matter. Calculations suggest it but who knows.
 
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rod

Oct 22, 2019
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Good comment LijeBaley. I note this recent report searching for DM at the quantum level in experiments. No evidence of an influence of dark matter on the force between nuclei, "The universe mainly consists of a novel substance and an energy form that are not yet understood. This 'dark matter' and 'dark energy' are not directly visible to the naked eye or through telescopes...Dark matter interacts with normal matter via the gravitational force, which also determines the cosmic structures of normal, visible matter. It is not yet known whether dark matter also interacts with itself or with normal matter via the other three fundamental forces—the electromagnetic force, the weak and the strong nuclear force—or some additional force."
 
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As a chemist I am not convinced that dark matter exists. Some other explanation is needed.
It seems that the old gravimetric analytical methods would not so consistently agree with newer analytical methods involving mass spectrometry and coulometric methods or be so self consistent. Gravity will influence gravimetric methods but have no effect on MS or electro-chemical methods. If my sample or the earth contain dark matter it will throw off (cause inconsistencies) gravimetic measurements. OR is the physics community claiming there is no dark matter in our solar system? I have been watching for a reasonable explanation. Does anyone have one?
 
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rod

Oct 22, 2019
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As a chemist I am not convinced that dark matter exists. Some other explanation is needed.
It seems that the old gravimetric analytical methods would not so consistently agree with newer analytical methods involving mass spectrometry and coulometric methods or be so self consistent. Gravity will influence gravimetric methods but have no effect on MS or electro-chemical methods. If my sample or the earth contain dark matter it will throw off (cause inconsistencies) gravimetic measurements. OR is the physics community claiming there is no dark matter in our solar system? I have been watching for a reasonable explanation. Does anyone have one?
FYI. DM in our solar system has been discussed on some of the forum threads, one source cited a 2018 report claiming only an asteroid worth of DM would be in the solar system. I did some checking and found 2020 reports that contradicted such claims, ref - Measuring the local Dark Matter density in the laboratory, "Despite strong evidence for the existence of large amounts of dark matter (DM) in our Universe, there is no direct indication of its presence in our own solar system. All estimates of the local DM density, crucial for all direct DM searches, rely on extrapolating estimates on much larger scales. We demonstrate for the first time the possibility of measuring the local DM density with a direct detection experiment..."

ref - Gravitational Focusing of Low-Velocity Dark Matter on the Earth's Surface

Searches continue but so far, direct DM detection at Earth or in our solar system remains something yet to be confirmed it seems---Rod
 
Did they forget to measure the temp matter and temporary energy of quantum fluctuation particle creation/destruction.? Simple solution to the missing mass and dark energy.
Large universe with many small temp mass and energy properties= large fleeting constant mass and energy.
 
"Potential "new physics" fixes to the standard model could involve changing the amount and nature of dark energy or dark matter—or both—as well as tweaks to how they interact with each other and with normal matter, among other more exotic modifications. "Some theoretical solutions to tinker with the cosmological model to fix the Hubble constant tension make this [sigma-eight tension] worse. Some make it better," Riess says. Hildebrandt agrees that there is no obvious solution in sight. "If there was a compelling model, maybe people would jump on that bandwagon," he says. "But at the moment, I don't think there is. It's really on us observers to improve the significance [of the sigma-eight tension] or disprove it."

This is an interesting article. Consider that about 4% of the universe is readily observable and as one source i have said, "That leaves only about 4% of reality accessible to observation." The other 96% remains a struggle in the BB cosmology.
Well, it is not statistically significant enough result, and so opinions may differ - there are many such suggestions out there, and as the statistics suggest most go away with further observations.

On the contrary there is no "struggle" to predict dark matter or dark energy in LCDM, the observations fits very well and at low uncertainty. For a recent test, the new repetition of measuring intergalactic gas with 6 instead of 2 FBR radio sources pinned the 4 % normal matter perfectly.

I think you mean that we don't know much detail about dark energy or dark matter yet. But as the above example show, LCDM makes advances all the time. No need to "struggle".
 
It's all swag right now with almost no experimental evidence. At least Einstein made predictions and suggested experiments that would either confirm or disprove his theories. So far General Relativity has held up well to experimentation with each year brining actual data that confirms his theories, the latest being a photograph of a black hole's event horizon in M87. Quantum mechanics is still very much theory with little experimental evidence. Same goes for dark energy and dark matter. Calculations suggest it but who knows.
Both quantum physics and LCDM has many and independent experimental evidences! The data that is observed and predicted by both are astronomical, see for example the LHC and the Planck surveys.

- LHC has analyzed 300 trillion (3×10^14) proton-proton collisions and store 25 petabyte observational data per year. *All* of it tests quantum physics well! [ https://en.wikipedia.org/wiki/Worldwide_LHC_Computing_Grid ]

- Planck has made a 4+ year, sky wide, multiple band analog survey. They too had to do sophisticated data processing to get it done [ https://arxiv.org/ftp/astro-ph/papers/0604/0604069.pdf ], and *all* of it tests LCDM well!

The amount of data generated and tested in astronomy is today ... well, astronomical.
 
As a chemist I am not convinced that dark matter exists. Some other explanation is needed.

It seems that the old gravimetric analytical methods would not so consistently agree with newer analytical methods involving mass spectrometry and coulometric methods or be so self consistent. Gravity will influence gravimetric methods but have no effect on MS or electro-chemical methods. If my sample or the earth contain dark matter it will throw off (cause inconsistencies) gravimetic measurements. OR is the physics community claiming there is no dark matter in our solar system? I have been watching for a reasonable explanation. Does anyone have one?


As we all know, some other explanation is not needed, however much personal opinion wish so. LCDM works well, and even if it didn't we have many agreeing dark matter observations so it would likely remain anyway.



I'm not sure what you mean by dark matter "throw off" gravimetric measurements. Dark matter density is lumpy, but still so low that our solar system contains about an asteroid worth of it, most likely sunk into Sun. And we would see the gradient, not the average.



"When you do these calculations, you find that about 10¹³ kg of dark matter ought to be felt by Earth’s orbit, while around 10¹⁷ kg would be felt by a planet like Neptune.



But these values are tiny compared to the other masses of consequence! The Sun has a mass of 2 × 10³⁰ kg, while Earth is more like 6 × 10²⁴ kg. Values like the one we came up with, in the 10¹³ — 10¹⁷ kg range, are the mass of a single modest asteroid. Someday, we may understand the Solar System well enough that such tiny differences will be detectable, but we’re a good factor of 100,000+ away from that right now."



[ https://medium.com/starts-with-a-bang/ask-ethan-if-dark-matter-is-everywhere-why-havent-we-detected-it-in-our-solar-system-67ca11f94b1f ]
 
FYI. DM in our solar system has been discussed on some of the forum threads, one source cited a 2018 report claiming only an asteroid worth of DM would be in the solar system. I did some checking and found 2020 reports that contradicted such claims, ref - Measuring the local Dark Matter density in the laboratory, "Despite strong evidence for the existence of large amounts of dark matter (DM) in our Universe, there is no direct indication of its presence in our own solar system. All estimates of the local DM density, crucial for all direct DM searches, rely on extrapolating estimates on much larger scales. We demonstrate for the first time the possibility of measuring the local DM density with a direct detection experiment..."



ref - Gravitational Focusing of Low-Velocity Dark Matter on the Earth's Surface



Searches continue but so far, direct DM detection at Earth or in our solar system remains something yet to be confirmed it seems---Rod

Your first link discuss doing detection of weakly interacting dark matter.

Your second link talks about doing direct detection, not that they have done it. But for what it is worth, no direct detection experiments that are based on weakly interacting or axion like particles have succeeded. Not to worry, dark matter may only interact by gravity.

TL;DR: I can't see that you have contradicted that we shouldn't - and isn't - seeing dark matter from only gravity.
 

rod

Oct 22, 2019
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FYI, responses here supporting BB cosmology using LCDM looks more like hand waving at times. This is an interesting article that space.com disclosed in the thread. Consider that about 4% of the universe is readily observable and as one source I have said, "That leaves only about 4% of reality accessible to observation." The other 96% remains a struggle in the BB cosmology. DM of any *kind* remains undetected in our solar system, in labs on Earth or the study of the Sun, showing DM is in the core (even a little bit) or perhaps a tiny bit of DM on the surface of the Sun too. I can understand why a chemist would look at this in science and be a bit suspicious.
 
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The chemist with suspicions thinks it may be a bit convenient to assert that something that makes up 10 times more "mass" than observable matter around us is so scarce here. it does stand to reason, as has been pointed out, that DM would be drawn to the cores of the sun and planets. If there were a significant amount in the core of a star, then I would suspect solar activities such as magnetic fields, H to He fusion and the like are affected. Then by extension, various stars with varying amounts of DM should show variances in properties. I don't have the physics background to model these things and at 67 I'm not looking for a dissertation project.

If there is a difference somewhere then there is a difference somewhere else, or there is no difference. I'll be watching for the wonderful things you guys turn up.
 
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It seems to me that the article is more about tweaks to our modeling of DM and DE. So not changing physics, but tweaking it, which is a way of saying it is changing, I suppose, but not dramatically. Am I right?

The comments from Adam Reiss add to the story. Recall that it was he that broke the story, publicly, that our universe is accelerating. He was on the Harvard team that beat, by a hair, the Berkley team in their independent SN research to tweak the Hubble Constant (now called the Hubble-Lemaitre Constant). [Hubble never said the universe was expanding, ironically.]
 
It seems to me that the article is more about tweaks to our modeling of DM and DE. So not changing physics, but tweaking it, which is a way of saying it is changing, I suppose, but not dramatically. Am I right?

The comments from Adam Reiss add to the story. Recall that it was he that broke the story, publicly, that our universe is accelerating. He was on the Harvard team that beat, by a hair, the Berkley team in their independent SN research to tweak the Hubble Constant (now called the Hubble-Lemaitre Constant). [Hubble never said the universe was expanding, ironically.]
I think it's a thinking problem why dark matter and energy eludes detection and when the universe weighs 1 and measure says .05. A rethink of temporary matter and energy from fluctuation fills in the missing elusive to find mass and energy of something that only exists for a brief moment but in a very large area has substance that persists with randomness. It exists only as a temporary weight/gravity and energy but it exists as a random mass/energy total.
 
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It's worth noting that we do have evidence for DM. Zwicky noticed that the speed of galaxies in their cluster were too fast without some sort of extra matter within it. He coined it Dark Matter in the 1930s. The odd rotation rate for spirals (Vera Rubin) was more evidence. I think it was the mapping of DM within the Bullet Cluster several years ago that also helped promote it.

But DE seems to be a simple label for a much more difficult idea that we can test.
 

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