I want to start by saying that I'm in no way trying to say that Dark Matter isn't a real pehonomenon in space. I also have no intention to sway one way or another. However, I feel like most scientiests are swaying towards the 'dark matter' is some kind of WIMP or such. It's much easier to read about 'proofs for' DM than 'proofs against' DM. This might be because there simply are more proofs for but it might also be that leading scientists are swayed towards one way because of fear of losing their jobs otherwise (since so much money is being spent on (and will be spent on) finding the particles). I want to gather all half/minor hints towards DM not being what we believe it is (the hints towards it being matter is easy to find). All I can find is; 1. Abell 520 A cluster of galaxies colliding and the space is actually bent where the mass is (unlike bullet cluster - the smoking gun for DM). However, according to the wiki page it says the validity of this data is uncertain and that the scientists involved have starting doubting it. What's the current status on this find? Is it a 'hint' towards DM not being a real thing? (I found this paper on Abell 520 from 2016, couldn't find any more recent work) 2. 21cm problem This one is a bit more complicated to understand and fairly new so it's hard to say. I left the link in the header. But lets say this goes the way and the study gets proven to be right, what would it mean for DM as a theory? 3. Most galaxies have (roughly) the same amount of DM in them. It's would be more compelling theory-wise if some galaxies proved to have almost no DM. But none has been found as of yet. However there was a galaxy with 'no dm' floating around in forums a few months ago but that got rebutted a month after it came out. Finally, what's your thought's on DM? Is it a 'solid' hypothesis given the current observations? How many more years will you give it before you start doubting DM being some sort of WIMP's?