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I guess the nightmare is more that it might be undetectable. There’s a real possibility that DM is real, but we hit the neutrino floor at some point without fin

I guess the nightmare is more that it might be undetectable. There’s a real possibility that DM is real, but we hit the neutrino floor at some point without finding anything (maybe couplings are too weak). Until there’s an actual convincing alternative, that indeed is not as apparent as you make it out to be, that would be pretty terrible for a lot of physics.

wruza 4y ago
Why isn’t it good for physics? It has found DM and can observe it via gravitational discrepancies, gets finally “solved” in this part. Does physics really need infinite modifications?
- ephimetheus 4y ago
  It’s not good because it means there is something in nature that we cannot understand and study, because we cannot in fact observe it directly. The gravitational discrepancies we have already, but without an explanation or observation, they’re not very satisfactory.
  - NateEag 4y ago
    "The eternal mystery of the world is its comprehensibility … The fact that it is comprehensible is a miracle." If the nightmare scenario is true, there would finally be a counterexample to this.
  - denton-scratch 4y ago
    > because we cannot in fact observe it directly. We can't observe anything "directly", other than the contents of our own minds. The "gravitational discrepancies" are an observation. It seems to me (non-physicist, non-cosmologist) that DM proponents can't tell us what DM is, despite being able to observe it. The article's "nightmare" is that it might turn out to be impossible to do that in principle. To my mind, that would indeed be a nightmare; we would have to accept that there are limits to what we can learn about the Universe. I don't believe we have encountered any such limits before.
    - ephimetheus 4y ago
      Directly here refers to explicit detection (“here is a signal that is DM and gives us immediate knowledge about its properties”) as opposed to implicit detection through inferring DMs existence from a lack of something. A lot of people complain about DM being fuzzy, and that’s exactly why: we only have indirect evidence. So what everyone wants is a direct measurement of DM, for example a particle signal if DM is a WIMP. And to your last point: that’s exactly it, the thought of an unknowable thing in the universe is terrifying, frankly. And this has nothing to do with wanting to be right, whatever DM is, I just want to know, even if it’s fancy MOND without defects somehow, or MACHOs.

wruza 4y ago

Why isn’t it good for physics? It has found DM and can observe it via gravitational discrepancies, gets finally “solved” in this part. Does physics really need infinite modifications?

ephimetheus 4y ago
It’s not good because it means there is something in nature that we cannot understand and study, because we cannot in fact observe it directly. The gravitational discrepancies we have already, but without an explanation or observation, they’re not very satisfactory.
- NateEag 4y ago
  "The eternal mystery of the world is its comprehensibility … The fact that it is comprehensible is a miracle." If the nightmare scenario is true, there would finally be a counterexample to this.
- denton-scratch 4y ago
  > because we cannot in fact observe it directly. We can't observe anything "directly", other than the contents of our own minds. The "gravitational discrepancies" are an observation. It seems to me (non-physicist, non-cosmologist) that DM proponents can't tell us what DM is, despite being able to observe it. The article's "nightmare" is that it might turn out to be impossible to do that in principle. To my mind, that would indeed be a nightmare; we would have to accept that there are limits to what we can learn about the Universe. I don't believe we have encountered any such limits before.
  - ephimetheus 4y ago
    Directly here refers to explicit detection (“here is a signal that is DM and gives us immediate knowledge about its properties”) as opposed to implicit detection through inferring DMs existence from a lack of something. A lot of people complain about DM being fuzzy, and that’s exactly why: we only have indirect evidence. So what everyone wants is a direct measurement of DM, for example a particle signal if DM is a WIMP. And to your last point: that’s exactly it, the thought of an unknowable thing in the universe is terrifying, frankly. And this has nothing to do with wanting to be right, whatever DM is, I just want to know, even if it’s fancy MOND without defects somehow, or MACHOs.