There are appealing theoretical reasons to think an axion exists [strong-cp]; there are appealing theoretical reasons to think an axion does not exist [chiral]. What this device can do is explore. They may come up empty because dark matter is not axions; they may come up empty because dark matter is axions but the physical parameters are surprising. But people agree that if axions comprise any sizeable fraction of dark matter then its parameters should be between this and that, and this device can find it there.
I think many people are worried, but unless there is a good alternative theory, the particle is still the simplest explanation. Over last 20 years a lot focus was on WIMPs (weakly interacting massive particles), but those searches ruled out a lot of parameter space that was considered sensible. For axions, people have only recently started to design detectors, so if dark matter is an axion there is hope to detect it.
If we will not find anything, it remains to be seen what is the best path forward. In the end the dark matter just behaves too much like dark particle with little cross section, so it is hard to replace it by something else ...
I would guess, "It would take a very long time--possibly forever--because scientists don't typically become 'worried' by perceived shortfalls in theories, rather they become excited." Often, that excitement finds an outlet through modifications to the theory or to wholesale alternative theories. In the case of Dark Matter, there's no shortage of proposals to overturn Dark Matter. It seems like there's a new one on HN every day. But, "the more's the merrier", I say! If you ask me (nobody did), they're all welcome. The only catch is, they have got to surpass Dark Matter on all of the many independent lines of observational evidence supporting the theory of Dark Matter, yet in my limited experience they almost never do.
They'll just do what they've done for the past twenty years.
Adjust the theory to make it darker, lighter and more nebulous.
The end station of dark matter is that "we know it's real because computer models but due to a fluke there's no dark matter in the solar system so we can't detect it".
I can't agree with this. No scientist says, "we know it's real because computer models but due to a fluke there's no dark matter in the solar system so we can't detect it." No scientist says, "we know it's real..." about anything. What scientists say is something like, "so far this theory has not been ruled out by evidence." So far, the theory of Dark Matter has not yet been ruled out by numerous attempts to do so along multiple independents lines of observational evidence:
- galaxy rotation curves
- galaxy cluster dynamics
- gravitational lensing
- the Cosmic Microwave Background radiation
- large-scale structure
- Baryon Acoustic Oscillations
- X-ray emission in galaxy clusters
- galaxy cluster collisions
- mass-to-light ratios
That's a tall order for any competing theories. They're welcome to try, of course, but so far none have succeeded.
There are appealing theoretical reasons to think an axion exists [strong-cp]; there are appealing theoretical reasons to think an axion does not exist [chiral]. What this device can do is explore. They may come up empty because dark matter is not axions; they may come up empty because dark matter is axions but the physical parameters are surprising. But people agree that if axions comprise any sizeable fraction of dark matter then its parameters should be between this and that, and this device can find it there.
[strong-cp] https://en.wikipedia.org/wiki/Strong_CP_problem [chiral] https://arxiv.org/abs/2412.02024
I think many people are worried, but unless there is a good alternative theory, the particle is still the simplest explanation. Over last 20 years a lot focus was on WIMPs (weakly interacting massive particles), but those searches ruled out a lot of parameter space that was considered sensible. For axions, people have only recently started to design detectors, so if dark matter is an axion there is hope to detect it. If we will not find anything, it remains to be seen what is the best path forward. In the end the dark matter just behaves too much like dark particle with little cross section, so it is hard to replace it by something else ...
I would guess, "It would take a very long time--possibly forever--because scientists don't typically become 'worried' by perceived shortfalls in theories, rather they become excited." Often, that excitement finds an outlet through modifications to the theory or to wholesale alternative theories. In the case of Dark Matter, there's no shortage of proposals to overturn Dark Matter. It seems like there's a new one on HN every day. But, "the more's the merrier", I say! If you ask me (nobody did), they're all welcome. The only catch is, they have got to surpass Dark Matter on all of the many independent lines of observational evidence supporting the theory of Dark Matter, yet in my limited experience they almost never do.
There are already a growing number of astrophysicists who don't buy into dark matter/energy.
How is that number measured if I may ask?
They'll just do what they've done for the past twenty years.
Adjust the theory to make it darker, lighter and more nebulous.
The end station of dark matter is that "we know it's real because computer models but due to a fluke there's no dark matter in the solar system so we can't detect it".
I can't agree with this. No scientist says, "we know it's real because computer models but due to a fluke there's no dark matter in the solar system so we can't detect it." No scientist says, "we know it's real..." about anything. What scientists say is something like, "so far this theory has not been ruled out by evidence." So far, the theory of Dark Matter has not yet been ruled out by numerous attempts to do so along multiple independents lines of observational evidence:
- galaxy rotation curves
- galaxy cluster dynamics
- gravitational lensing
- the Cosmic Microwave Background radiation
- large-scale structure
- Baryon Acoustic Oscillations
- X-ray emission in galaxy clusters
- galaxy cluster collisions
- mass-to-light ratios
That's a tall order for any competing theories. They're welcome to try, of course, but so far none have succeeded.