[Ma8ee]

I understand the motivation for dark matter. My point is that as long we have a full density distribution to play with, we can explain almost anything with the model. And the start of this thread was me disagreeing with how much it actually proved that observations matched "really really well " with the model.

I don't see why the scenario "gravity works differently at large scales" couldn't explain the observations until we have some idea how gravity would work differently.

Don't forget that each of these observations rely on a quite large sets of assumptions about everything from how much luminosity from galaxies with a certain (normal) mass can vary to how we estimate distances to very far away objects. We don't have that many observations of e.g. gravitational lensing. And, if we realize we actually don't know how to calculate things correctly with GR, or our theory of GR is wrong, that will have implications for all of those assumptions.

The dark matter hypothesis might very well be right. It is a very reasonable guess. But so far I think the proofs for it have been overstated.

[ymolodtsov]

Nobody says it's proven. It's just the best what we have so far. Any theory that would work just as good and explain anything on top would be welcome.

And I can say myself that not everyone agrees with that discovery: http://www.astronomy.com/news/2019/09/astronomers-cant-agree...

Well, people still debate about the Bullet cluster. But if it's correct then it's actually a good (relatively) confirmation for some sort of dark matter. It two similar galaxies look the same but have dramatically different mass distribution then there's some mass we don't see yet.