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First of all, this is super cool but I'm confused about these sentences: >The discovery of NGC 1052-DF2 demonstrates that dark matter is somehow separable from
by wuliwong 9y ago
First of all, this is super cool but I'm confused about these sentences:
>The discovery of NGC 1052-DF2 demonstrates that dark matter is somehow separable from galaxies. This is only expected if dark matter is bound to ordinary matter through nothing but gravity.
Why is this the only explanation? Was this a prediction of dark matter theorists that they will find galaxies without any dark matter and that proves it only interacts via gravity?
Lately, I've pondered that the observed behavior dark matter explains could be the result of a new force that only has an appreciable effect in regimes of extremely high mass/energy. Or possibly gravity is more complex than predicted by GR. Just like newtonian gravity needed to be extended by GR possibly GR still needs further extension to account for unexpected behavior in these extreme mass/energy regimes? If all the forces are ultimately just one force than these two ideas I've been thinking about are essentially the same.
I would assume there has been some work exploring this avenue of thought? Has it been fruitless?
- enkid 9y agoThe idea of modifying general relativity is called as MOND and has been thoroughly investigated by physicists. There are still proponents, but I think the models are not matching the observational data. Also, the fact that Galaxies with similar (visible) masses have different levels of rotational momentum seems to hint that dark matter is a thing. I don't understand why people think having something that interacts with fewer forces than normal matter is more complicated than Jerry rigging a change to the elegant general relativity.
- wuliwong 9y agoDark matter is easily the most popular theory for this observed phenomena, so clearly most people do NOT think having "something that interacts with fewer forces than normal matter is more complicated than Jerry rigging a change to the elegant general relativity." I'm not sure if you are saying that I think one is more complicated than the other because I do not. I'm simply wondering about ideas and asking questions. Surely we should still ask questions, right?
- noetic_techy 9y agoMOND is only one theory in a whole class of modified gravity theories: https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics https://en.wikipedia.org/wiki/Modified_Newtonian_dynamics
- lalaithion 9y agoThere are physicists working on the problem, yes: https://en.wikipedia.org/wiki/Alternatives_to_general_relativity#Modern_theories_1980s_to_present https://en.wikipedia.org/wiki/Alternatives_to_general_relati...
- wuliwong 9y agoThanks for googling for me. :)
- eloff 9y agoI'm not a physicist, but my laymans understanding is that it's fairly easy to account for some cherry-picked observations with modified gravity, but to account for all of them requires something at least as contrived as dark matter. So the evidence is still pointing in that direction for now.
- dnautics 9y agoKeep in mind that each Galaxy must have its own curve-fit distribution of dark matter whereas alternative gravity theories fit all galaxies using a single free parameter, which makes it en face a more appealing model.
- eloff 9y agoPlus to me dark matter feels like a hack to make the math work. It feels inelegant. But that doesn't make it wrong - nature doesn't care what I like or don't like.