Dark Matter Is Not Dark Matter

Mond does not do a good job of describing how galaxy clusters rotate and spin around themselves. It's much more difficult for it to explain like the cosmic microwave background and lensing which is very strong evidence for dark matter. The galaxies we see don't really line up with what we expect for dark matter so one thing specifically we look at is a relationship between how bright the galaxies are and how fast they're spinning that should tell us something about how much dark matter there is in the galaxy.