[MattPalmer1086]

The bullet cluster is not the slam dunk proof of dark matter that is commonly supposed. For example, see this: https://tritonstation.com/2024/02/06/clusters-of-galaxies-ru...

[whatshisface]

>So the unseen mass in clusters could just be ordinary matter that does not happen to be in a form we can readily detect.

That is the same thing as dark matter...

[MattPalmer1086]

No. Dark matter is a proposed form of matter which does not interact with light.

Normal matter we can't detect isn't dark matter - it's just currently undetected matter. As our observational ability improves we find more of it.

[whatshisface]

That's WIMPS, early candidates for dark matter included primordial black holes and dust.

[petre]

WIMPS are most probably not real. They'll keep searching but it's quite unlikely they'll find any.

https://en.m.wikipedia.org/wiki/LZ_experiment

[MattPalmer1086]

A good point. I have heard of primordial black holes as a candidate for (at least some) dark matter. Not heard that dust was ever a candidate (if you have a reference it would be appreciated).

[ahazred8ta]

Baryonic (tangible) dark matter exists in the form of MACHOs, which includes small cold planetary-mass dwarf stars. But there's a limited number of these, and the Big Bang hydrogen helium ratio puts limits on the amount of baryonic matter there can be.

[kelseyfrog]

Dark matter is a question, not a theory.

WIMPS, sterile neutrinos, SIDM, primordial blackholes, MACHO, MoND, entropic gravity, &c all seek to answer the black hole question.