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| bartist |
 Posted: Sun Mar 10, 2024 8:48 pm |
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Joined: 27 Apr 2010
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Location: Black Hills
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| Firing off a canine? |
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| Syd |
| Posted: Fri Mar 15, 2024 1:17 am |
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Joined: 21 May 2004
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Location: Norman, Oklahoma
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| BEWARE THE IDES OF MARCH! |
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| bartist |
| Posted: Fri Mar 15, 2024 11:13 am |
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Joined: 27 Apr 2010
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| Thanks, I have a pi hangover from yesterday. |
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| gromit |
| Posted: Mon Mar 25, 2024 6:09 am |
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Joined: 31 Aug 2004
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Location: Shanghai
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Bart, it's annoyed me for the last decade or two that science articles casually state that dark matter makes up xx% of the universe. As though it were an established fact and not merely a fancy theory. Same with dark energy. It would be better to write that dark matter is believed to ...
Or the scientific consensus estimates that dark matter ...
In many ways, dark matter/energy are a classic fudge factor akin to ether or epicycles. Something created not because it has been observed and is known to exist -- the names give that away -- but because they salvage an established theory which increasingly doesn't accord with measurements and interpretations thereof. Not to say that they are wrong theories, but when you invent something which fits the numbers, you can't use the fact that the numbers work as proof of its existence. So I cringe at assertions that dark matter and/or energy exist. They are theorized to exist, and astrophysicists endeavor to measure them and ascertain if they are real.
Quote: Scientists have long believed that dark matter makes up about 27 percent of the universe, with ordinary matter constituting less than 5 percent, and the rest being dark energy. This understanding has helped explain the behavior of galaxies, stars, and planets.
So what you know accounts for only 5% of what you believe exists. When one fudge factor provides only another perhaps 27%, so you have to invent a second invisible phenomenon for the remaining 2/3rds of the universe, perhaps your standard model is crap.
Anywho what spurred this mini-rant was a new alternative theory which dispenses with the need for dark anything.
Quote: “The study’s findings confirm that our previous work about the age of the universe being 26.7 billion years has allowed us to discover that the universe does not require dark matter to exist,” explains Gupta in a media release. “In standard cosmology, the accelerated expansion of the universe is said to be caused by dark energy but is in fact due to the weakening forces of nature as it expands, not due to dark energy.”
Gupta’s research employs a combination of the covarying coupling constants (CCC) and “tired light” (TL) theories, together known as the CCC+TL model. This innovative model posits that the forces of nature weaken over cosmic time and that light loses energy as it travels long distances. Gupta’s findings, which align with several observations about the distribution of galaxies and the evolution of light from the early universe, suggest that the universe operates differently than currently believed.
https://www.spacechatter.com/2024/03/19/no-dark-matter-in-universe/
I have no idea if this is anything more accurate, but theories should be presented as such. Until they pass a level of certainty and proof that they can be accepted as fact.
Just as the sub-atomic world follows distinctly different physics to our everyday world, it's possible that at the macro-universal level some different physics are at play. The notion of tired light gets at that. Interesting.
Hopefully new models which question or dispense with dark matter and dark energy will relegate them back to theories and no longer facts in scientific writing. |
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| Syd |
| Posted: Tue Mar 26, 2024 12:30 pm |
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Sabine Hossenfelder always says 'dark matter, if it exists' to remind us that it's still unproven and a lot of the candidates are really hypotheses without much to back them. I say the same fo Gupta's ideas and they would contradict a lot of what we know of star formation.
She also remarked that dark energy is really the curvature of the universe and I'm not sure what she means by that, although curving space takes mass and energy and some of that energy is in the curvature.I'm still skeptical of the idea that the expansion of the universe is speeding up. It relies partly on the cosmological principle, which supposedly holds beyond a certain distance, and I have seen no evidence that that is true. |
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| Syd |
| Posted: Tue Apr 02, 2024 9:36 pm |
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| Here's a take on Gupta's hypothesis from Anton Petrov: https://www.youtube.com/watch?v=1uYB9KOYGuk |
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| bartist |
| Posted: Thu Apr 04, 2024 12:27 pm |
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Syd wrote: Sabine Hossenfelder always says 'dark matter, if it exists' to remind us that it's still unproven and a lot of the candidates are really hypotheses without much to back them. I say the same fo Gupta's ideas and they would contradict a lot of what we know of star formation.
She also remarked that dark energy is really the curvature of the universe and I'm not sure what she means by that, although curving space takes mass and energy and some of that energy is in the curvature.I'm still skeptical of the idea that the expansion of the universe is speeding up. It relies partly on the cosmological principle, which supposedly holds beyond a certain distance, and I have seen no evidence that that is true.
I greet a fellow Sabine fan. (she had many at the online science forum I used to run)
I was going to reply to Gromit, but you have covered it. LCDM is but one theory to deal with an observed acceleration in Hubble expansion. (supported IIRC by the observations of "standard candles" of 1A supernovae) I am not quite clear on how energy density would not be at the causal heart of spatial curvature - my understanding was that the curvature of a 4D Lorentzian manifold was a geometric representation of something that matter/energy does when you have a lot of it. I will try to unrust some of my astrophysics and go give Dr. Gupta a read. Dark matter is, at least, something that there is some hope of finding, so the theory remains strong in that sense that it is quite testable.
Dark energy remains, for me, a lot of conjecture of varying coherence. Sure, there could be vacuum energy, with virtual particles popping in and out of existence, and creating a negative pressure effect, which unfortunately gets translated by some journalists as "antigravity" (as if someday, we could make these nearly magical starship drives with it). As Gromit alludes to, this veers pretty close to epicycles and phlogiston. Bah. |
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| Syd |
| Posted: Fri Apr 05, 2024 9:43 pm |
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| I argue stuff like this with a friend on Wednesday nights. Neither of us is a physicist but when has that stopped anyone? He always maintains that the General Theory of Relativity must be wrong because it doesn't blend with quantum mechanics. Being contrarian, I maintain quantum mechanics is the one that should be corrected since general relativity has passed every test. (I don't think there really is a contradiction since quantum mechanics is designed for subatomic scales and general relativity for macroscopic scales. Besides, quantum mechanics predicts that vacuum energy is 10^180 times what we observe, so so much for accuracy.) It's a bit like trying to work out the ideal gas law through nuclear physics. |
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| bartist |
| Posted: Sat Apr 06, 2024 11:09 am |
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Yep the "vacuum catastrophe" points to real problems that need to be worked out in QFT.
Gupta seems to cherrypick his obervations, as Petrov in your video noted. Tired light has never held up well and always feels pretty ad hoc. It can't be Compton scattering, it can't be a photon losing energy for no reason other than some vague handwaving, and I can't make much sense of the version of tired light where a boson can bump into another boson. (photons aren't really tiny little balls, more like spots of field strength or as Dirac et al would have it, field perturbations)
Quote: Neither of us is a physicist but when has that stopped anyone?
Indeed. I've noticed that biologists or chemists, e.g., are often not reluctant to try their hand at physics (and often crash), but physicists (to their credit) rarely try to assert any knowledge of those less fundamental sciences. Their plate is already full. |
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| Syd |
| Posted: Mon Jul 01, 2024 2:55 am |
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Clint Laidlaw (of Clint's Reptiles) has a lot of fun videos where he asks whether a certain animal may make the best pet reptile/mammal/bird/etc. for you. SPOILER: Black Mambas don't make good pets, as don't human children (though the rewards are enormous). Death adders do as long as you're sensible--otherwise you need antivenom but you and the snake will be really embarrassed.
Clint's a phylogenist by degree, so has been doing a lot of phylogeny videos, by no means restricted to reptiles. These are fascinating, and he's at his best in his two videos on Carnivora, the first on Feliformia, the second on Caniformia (which includes seals). He's halfway through Rodentia, doing the mouselike rodents, which include squirrels. But did you know that falcons are more closely related to parakeets than to eagles or owls? |
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| bartist |
| Posted: Fri Jul 05, 2024 11:55 am |
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Syd wrote: But did you know that falcons are more closely related to parakeets than to eagles or owls?
I did not know this. I still don't feel they are close enough for casual substitutions. E.g. I feel that The Maltese Parakeet would have to be quite a different movie. However, if one were tempted to replace other avian species in movies with parakeets, then The Three Days of the Parakeet would definitely get my green light. |
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| knox |
| Posted: Mon Jul 08, 2024 11:02 am |
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Location: St. Louis
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bartist wrote: Syd wrote: But did you know that falcons are more closely related to parakeets than to eagles or owls?
I did not know this. I still don't feel they are close enough for casual substitutions. E.g. I feel that The Maltese Parakeet would have to be quite a different movie. However, if one were tempted to replace other avian species in movies with parakeets, then The Three Days of the Parakeet would definitely get my green light.
Sounds like they'd need a big budgie to make that. |
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