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Have We Gotten Dark Matter All Wrong?
- rawgabbit 3y agoI wish the author listed the theories that could potentially replace the dark matter particle theory.
- angiosperm 3y agoIt seems easy to imagine a universe in which dark matter, particles or otherwise, have literally no interactions with regular matter except via gravitation. All the efforts to spot such an interaction seem to be based purely on wishing that it is not true, so that fancy expensive detectors can defensibly be promoted and somebody might get a prize. It seems of a piece with string theory. Maybe astrophysics, like particle physics, has lost its way, and needs to return to investigating phenomena that answer to experiment. Solar photosphere physics has yet to be elucidated in any detail. Jupiter's liquid-electrolyte moons orbit well within its magnetosphere. And planetary nebulae favor a long axis parallel to the galactic plane. Lots of crunchy physics has yet to be done, even without descending to low-status solid-phase phenomena. On a completely different note: why does the author think a dark star would necessarily explode before turning into a black hole? A rotating pair of black holes seems like an efficient way to sweep up billions of solar masses of perfectly serviceable mass, and dynamical friction with it seems like a nice way to bleed off momentum.
- wswope 3y ago> It seems easy to imagine a universe in which dark matter, particles or otherwise, have literally no interactions with regular matter except via gravitation. Very much a valid hypothesis https://en.wikipedia.org/wiki/Sterile_neutrino https://en.wikipedia.org/wiki/Sterile_neutrino
- mikhailfranco 3y agoNeil Turok has recently proposed cosmological models based purely on the existing Standard Model with sterile right-handed neutrinos. No new forms of Dark Matter required. One RH neutrino must be massless, and another must be 4.8 x 10^8 GeV. https://arxiv.org/abs/1803.08930 https://arxiv.org/abs/1803.08930
- ssivark 3y ago> All the efforts to spot such an interaction seem to be based purely on wishing that it is not true, so that fancy expensive detectors can defensibly be promoted and somebody might get a prize. That's incredibly short-sighted. There are many other falsifiable hypotheses and due diligence directs us to make measurements to test those hypotheses. More generally, it makes zero sense to assume the worst case that cannot be ruled out and use that as an excuse to not pursue science. For example, it is impossible to "falsify" superluminal/nonlocal influence -- and not being able to screen for that renders the whole scientific process fundamentally useless (because there could always be something happening in a neighboring galaxy that is influencing your experiment -- how do you rule that out or control for it?). We simple continue doing science with the optimism that the the universe is not perversely adversarial to our attempts to understand it (and give that optimism fancy names like Occam's razor).
- dventimi 3y agoWell put
- angiosperm 3y agoIt makes plenty of sense to spend on a multitude of cheap experiments in place of vanishingly few super-expensive ones, and on a multitude of disparate, poorly understood phenomena instead of hammering away at just one.
- dventimi 3y ago"Plenty of sense" is a subjective measure that can't be quantified. A person could just add easily state that it makes plenty of sense to concentrate some resources on a few or even just one line of inquiry, because of the perceived payoff. Nobody would be in a position to tell that person they're wrong.
- angiosperm 3y agoDollars have always been strictly quantitative. A dollar spent on experiment A is a dollar not spent on experiments B through Z.
- dventimi 3y agoNobody has a perfect understanding of which phenomena won't answer to experiment, not even you.
- angiosperm 3y agoThat is strictly true. However, it is not hard to gauge which phenomena are cheaper to experiment on. I would rather see a hundred independent phenomena pursued than just one. Since significance correlates so poorly with cost, odds favor more results.
- alakep 3y agoDark matter almost certainly doesn’t exist. This hunt for it is very parallel to the hunt for the “ether” that Einstein showed didn’t exist. Curiously, the big insight of relativity was getting rid of two bad assumptions: the concept of “simultaneity” and the idea that gravitational acceleration is locally different from other acceleration. I think the resolution to whatever dark matter is will likely make other fundamental problems in physics simpler as well.
- EGreg 3y agoBoom yes
- deleted 3y ago[deleted]
- dventimi 3y agoBoom no. Dark Matter is already known to exist: neutrinos, for instance
- EGreg 3y agoSorry but you’re mistaken https://www.astronomy.com/science/ask-astro-are-neutrinos-dark-matter/ https://www.astronomy.com/science/ask-astro-are-neutrinos-da...
- dventimi 3y agoNo, that article is referring to COLD dark matter, which is responsible for structure formation but does not encompass all possible species of dark matter. There are others. "Warm" dark matter is one of them and neutrinos are an example. It's difficult to explain structure formation with warm dark matter, which prompts the search for cold dark matter. Popular science articles like this one truncated the term, where it's entered the popular lexicon as just "dark matter."
- dventimi 3y agoWhat's your alternative hypothesis to explain large scale structure formation?
- ETH_start 3y agoThere is also Modified Newtonian dynamics as a potential alternative to the dark matter explanation for the apparent extra mass: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
- dventimi 3y agoMOND doesn't explain galaxy formation.
- quectophoton 3y agoI'm no physicist and I won't pretend that I understand any of those words, so this will probably not make any sense. But I'm curious how particle decay would be like for a particle with a de Broglie wavelength of several lightyears, and how would that be affected by the speed of causality. (EDIT: Or even a few light-minutes (like from Earth to Sun) or whatever distance where we no longer have the luxury of "things looking instantaneous".)
- dventimi 3y ago> Have We Gotten Dark Matter All Wrong? No https://en.m.wikipedia.org/wiki/Betteridge%27s_law_of_headlines https://en.m.wikipedia.org/wiki/Betteridge%27s_law_of_headli...