> There's plenty of hot dark matter coursing right through you right now !
That statement is exactly the problem as I see it, as dark matter is an attempt to save an existing paradigm using a trick that makes use of unknown but conceptually understandable matter.
The same was and is true for Einstein's cosmological constant: It's a hack that was necessary to make a theory match with the observations.
Introducing hypothetical/imvisible matter to make a theory fit observations does not mean that this matter really exists.
I did not say that scientists think that there is nothing more to discover, just that there is a tendency to try to fix up existing theories instead of accepting that they might be wrong. I'm no expert in particle physics or relativity (my field is quantum mechanics), so I'm not able to judge the merit of different theories involving dark matter, I'm just not convinced that dark matter / dark energy is real. If anyone shows me compelling experimental evidence I'll be happy to change my mind.
So far we haven't seen any convincing arguments for the existence of dark energy or dark matter though, and I think there's a chance that they end up as the 21st century equivalent of the "ether".
I'm pretty sure raattgift was referring to neutrinos when he said hot dark matter was "coursing right through you". He wasn't assuming the existence of any speculative form of dark matter.
Yes. "Hot" because neutrinos move quickly compared to the speed of light, "dark" because they do not feel electromagnetism, and "matter" because they couple to the metric.
They explain the anomalous momentum in beta decays, among other things, and are still difficult to detect.
To explain the anomalous momentum we infer around large scale structures at z << 1, it's pretty reasonable to consider neutrinos or neutrino-like particles that are "cold" -- moving slowly compared to the speed of light, thus more likely to "hang around" in a region of spacetime instead of quickly running away to infinity. Although they interact very weakly with matter, they still impart momentum, so hot dark matter would tend to smear apart gas clouds rather than encouraging them to collapse into denser objects like stars. Likewise, it is perfectly reasonable to search for them in ways analogous to how the neutrino itself was searched for experimentally and observationally, and like with the first detection of the neutrino, it is liable to take time to detect or let various non-detections exclude all the regions of the particle mass vs nucleon cross-section parameter space.
Moreover, the search for this sort of cold dark matter does not preclude concurrent searches for other possibilities.
So I can't agree with ThePhysicist that there is a problem here, other than that there is apparently a communications gap that affects even people with backgrounds in quantum mechanics.
That statement is exactly the problem as I see it, as dark matter is an attempt to save an existing paradigm using a trick that makes use of unknown but conceptually understandable matter.
The same was and is true for Einstein's cosmological constant: It's a hack that was necessary to make a theory match with the observations.
Introducing hypothetical/imvisible matter to make a theory fit observations does not mean that this matter really exists.
I did not say that scientists think that there is nothing more to discover, just that there is a tendency to try to fix up existing theories instead of accepting that they might be wrong. I'm no expert in particle physics or relativity (my field is quantum mechanics), so I'm not able to judge the merit of different theories involving dark matter, I'm just not convinced that dark matter / dark energy is real. If anyone shows me compelling experimental evidence I'll be happy to change my mind.
So far we haven't seen any convincing arguments for the existence of dark energy or dark matter though, and I think there's a chance that they end up as the 21st century equivalent of the "ether".