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It's much more than a placeholder for observations that don't match theory. There are a whole bunch of very different observations that don't match theory in d

It's much more than a placeholder for observations that don't match theory. There are a whole bunch of very different observations that don't match theory in different ways, if your theory doesn't include dark matter. But if your theory includes dark matter, all those various experiments match theory pretty darn perfectly. There's no a priori reason why something like dark matter shouldn't exist. It would be nice to directly detect it through scattering experiments on Earth, but there are a lot of possibilities for what dark matter is, and each would require a different type of experiment to detect.

davrosthedalek 7y ago
Worst case, all couplings to the SM might be so small that it's undetectable on earth. A purely gravitational direct detection is probably out of reach for quite a while.
- DiogenesKynikos 7y ago
  That would be pretty disappointing, but as far as I understand it, entirely possible. There are three ways to detect dark matter: 1. scattering in a lab 2. annihilation products observed with a telescope 3. gravitational effects We've seen 3, and we'll probably get a huge amount more detail on the distribution of dark matter through that method as time goes on. That would already be pretty convincing to me. People have been looking for both 1 and 2 for a while, without any conclusive detection. But it's easy to write down theories of dark matter that are extremely difficult to detect with those methods. At some point, we may have to accept that the only way to detect dark matter is method 3, through gravitational effects.
  - davrosthedalek 7y ago
    That's why I think it is so important to do precision tests of the Standard model here on earth. DM might show up as differences between theory and measurement. There are a couple of puzzles like that, g_muon-2, proton radius, ^8Be,... Maybe we get lucky.

davrosthedalek 7y ago

Worst case, all couplings to the SM might be so small that it's undetectable on earth. A purely gravitational direct detection is probably out of reach for quite a while.

DiogenesKynikos 7y ago
That would be pretty disappointing, but as far as I understand it, entirely possible. There are three ways to detect dark matter: 1. scattering in a lab 2. annihilation products observed with a telescope 3. gravitational effects We've seen 3, and we'll probably get a huge amount more detail on the distribution of dark matter through that method as time goes on. That would already be pretty convincing to me. People have been looking for both 1 and 2 for a while, without any conclusive detection. But it's easy to write down theories of dark matter that are extremely difficult to detect with those methods. At some point, we may have to accept that the only way to detect dark matter is method 3, through gravitational effects.
- davrosthedalek 7y ago
  That's why I think it is so important to do precision tests of the Standard model here on earth. DM might show up as differences between theory and measurement. There are a couple of puzzles like that, g_muon-2, proton radius, ^8Be,... Maybe we get lucky.