wolfpack_charlie t1_itvav05 wrote
Reply to comment by Due_Connection179 in Earth's atmosphere could be turned into a giant dark-matter detector by trevor25
Dark Matter is every single place that astronomers look. Everywhere. Every galaxy rotates faster than it should, gravitational lensing from huge galaxies always shows a big excess in mass from what's visible, large galaxy clusters don't have enough visible mass to stay held together, and the CMB should be more uniform unless there's way more hidden mass in the universe.
All of these discrepancies are explained by there being some kind of matter that interacts with gravity and not light. Astronomers aren't saying "this is exactly what dark matter is", they're saying "the most reasonable explanation is that there is some kind of matter we can't directly see that is exerting all this gravitational force"
What part of dark matter are you "not convinced" on? The data is there. Astronomers have simply observed these gravitational anomalies and there has to be *something* causing it
Due_Connection179 t1_itveh9m wrote
>Dark Matter is every single place that astronomers look. Everywhere.
- Except they can't see it, nor can they prove it yet.
>Every galaxy rotates faster than it should
- What if we are simply underestimating the power that super-massive black holes have on gravity and the galaxies around them?
>gravitational lensing from huge galaxies always shows a big excess in mass from what's visible
- Gravitational Lensing causes weird things to happen to the background of the galaxies we are looking at, so why wouldn't it just fall in this category?
>large galaxy clusters don't have enough visible mass to stay held together
- What if they are held together in ways similar to multi-star systems but on a much larger scale? What if they are actually orbiting around each other but they are so massive that it's hard to pick that up?
>the CMB should be more uniform unless there's way more hidden mass in the universe.
- Are there any good articles on this?
>All of these discrepancies are explained by there being some kind of matter that interacts with gravity and not light.
- We have picked up particles that are 34 picometers across (1 picometer = 1 trillionth of a meter), so how come we can't pick up this particle that makes up 95% of the universe?
>"the most reasonable explanation is that there is some kind of matter we can't directly see that is exerting all this gravitational force"
- It seems like the most reasonable explanation is that we don't understand enough about gravity when it's on the scales of black holes, super-massive black holes, or full galaxies. That's what I'm not convinced of.
wolfpack_charlie t1_itvlyso wrote
> Except they can't see it, nor can they prove it yet.
What I mean to say is that everywhere astronomers look, there isn't nearly enough mass to account for the gravitational effects they see. (It's like how astronomers observed black holes indirectly, by seeing their gravity affect nearby stars before the EHT got a direct photo) This is called the "missing matter problem" and dark matter is the best explanation they have.
> we don't understand enough about gravity
If a modified theory of gravity was proposed that offered a better and more consistent explanation than dark matter, then it would be the dominant theory. The best attempt at this is called MOND, and it can explain fast galaxy rotation but none of the other observed phenomena that point towards dark matter, so it's not considered a better explanation than dark matter
Due_Connection179 t1_itvn6jm wrote
>Proponents of MOND emphasize predictions made on galaxy scales (where MOND enjoys its most notable successes) and believe that a cosmological model consistent with galaxy dynamics has yet to be discovered.
This was my whole point, so I guess for now I side with MOND over the Dark Matter theory.
wolfpack_charlie t1_itvobgy wrote
From the same wikipedia article:
> The most serious problem facing Milgrom's law is that it cannot eliminate the need for dark matter in all astrophysical systems: galaxy clusters show a residual mass discrepancy even when analyzed using MOND.[2] The fact that some form of unseen mass must exist in these systems detracts from the adequacy of MOND as a solution to the missing mass problem
MOND still requires dark matter to exist.
Due_Connection179 t1_itvreuf wrote
Thanks for linking that. That is very interesting that MOND needs dark matter to exist like that.
This article is the only one I could find that could "detect" dark matter and so far no one has been able to duplicate their results.
This article suggests that the best chance of detecting dark matter is currently in the middle of its 1000-day mission to collect data.
I honestly just need more than "trust me, it exists" before I can actually believe it because right now I laid out 5 questions that scientists can't really answer about Dark Matter.
wolfpack_charlie t1_itw3tr3 wrote
This video is really good rundown of why astronomers are confident that dark matter exists even though they haven't directly detected it yet. The indirect evidence is overwhelming and can't be explained by any kind of ordinary matter or modifications to gravity. You're right that there are a lot of unanswered questions about dark matter - it's one of the biggest unsolved problems in science.
I recommend Dr Becky's channel in general for astronomy content. She's a PhD astrophysicist and great at explaining deep concepts in astronomy and cosmology
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