Dark matter IS A THING. At least there is some thing out there that interacts weakly with the elctroweak force and interacts normally with gravity. We have plenty of evidence of it EXISTING. The problem of dark matter is we don’t know what it is… But sure as hell there is something. See the Bullet cluster if you don’t believe me. And if you are a bit physics savvy, you can understand that it’s evidence is imprinted in the CMB. We just don’t know what it is.
The gravitational effect is the only prerequisite. The WIMP theory predicts weakly interacting dark matter but even primordial nucleosynthesis does not require weakly interacting, just that it be nonbaryonic. So only if WIMPs are right is it going to be weakly interacting.
Well I’m not the one to argue with you but dark matter is only a thing because our current assumptions are a thing.
If we had to change our thinking because of new knowledge of some fundamental assumption (such as the reason for red shift), it could very well do away with dark matter. I’m sure such a change of thinking will seem as ridiculous to scientists today as heliocentrism seemed to astronomers of Galileo’s day.
Yes, there may be an alternative answer. Just need to throw general relativity out of the window.
To be fair, future physics may indeed throw it away so there’s that.
It is just not one observation that the new assumption has to fit. There are multiple options that fit some but not others, dark matter fits most we just don’t know what it’s made up of.
