Can someone explain why we are certain there is dark matter in our universe? I understood it like this. At some Point in our recent history we figured out, that according to our math galaxies (or sth like that) wouldnt have developed like they did or wouldnt even stay in 1 Piece since they do not have enough mass. So we came up with dark matter as a source of mass to Keep it all in place. Now since dark matter does not react with anything other than its gravitational pull u cannot testify its existence. If that is the case "dark matter" seems like a pretty far fetched concept to me which maybe is validating bad math or sth just to make it work. Im sorry for my bad spelling english isnt my first language and im not very educated. I hope someone maybe takes the time to help me with this even a good link (other than Wikipedia) would help me alot.