| > what is dark matter? is it the opposite of matter? how can it be called matter when it doesn't exist? Dark matter is what we call the discrepancy between our observations of how galaxies and galaxy clusters move, and how our theories tell us they should move based on our best estimates for how much normal matter is in those galaxies. We call it "dark matter" because our formulas give the right prediction if we add a lot of mass where we see none, that is, if we assume there is some matter there that does not emit or interact with light. AFAIK, the difference between general relativity with 3 spatial dimensions and one with additional spatial dimensions show up on the small scale, and not large scale like galaxies[1]. > could it not be the space-time curvature from the mass itself but from the encapsulating dark matter around it If dark matter is indeed some kind of matter, then it would indeed affect the space-time curvature. That's in fact the entire point behind calling it dark _matter_, as mentioned above. Of course there is the possibility that our theories needs to change. There have been proposed alternatives that does not require additional matter in the form of new particles. The problem is that it's very difficult to get the theories to match non-dark matter observations, all the "normal stuff", as well as dark matter observations. [1]: https://www.forbes.com/sites/briankoberlein/2016/04/26/looki... |
I'm not a physics expert so forgive me if this is a naive take, but could black holes just sitting around, too far from other objects to have a visible effect, account for this unaccounted mass? IIRC they're small in size but incredibly heavy, and if space is infinite then they could just be sitting around taking up mass.