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I used to work on dark matter experiments. (This was a few years ago now, and wasn't for very long -- I was helping out colleagues -- but I don't think the situ

I used to work on dark matter experiments. (This was a few years ago now, and wasn't for very long -- I was helping out colleagues -- but I don't think the situation has changed much.) I don't think anyone worth listening to considers dark matter to be a Universal Truth or anything. It's a crappy theory that needs better experimental evidence on the micro scale. It's just that all attempts to find that evidence have turned up nothing. (Except DAMA/LIBRA, the bane of the previously mentioned colleague's days and motivating factor for the experiment in question... but nobody actually believes them, so let's value their reports at "nothing".) The biggest problem is that all alternatives to date are worse. They all have problems, problems of equal or greater severity than dark matter. That, more than any other reason, is the reason dark matter is still the leading theory. I do strongly believe we should work on the advancement of non-dark matter theories. That's how you lap the current leader, after all. And neglecting alternative theories was what got us into a couple decades of string theory stagnation, a mistake we'd be wise not to repeat. If a new theory or new evidence for an existing theory emerges, dark matter will lose mindshare amazingly quickly. There is, of course, a "nightmare scenario". The WIMP carries a weak charge, by definition. It was dreamed up that way to make it detectable and have a presence in the universe. (And there may have been a theoretical preference; I wouldn't know, I've always been an experimentalist.) But there's no reason it must carry a charge, weak, strong, or electromagnetic. That would make it really quite invisible to experiments. This may be the universe we live in.

sgt101 6y ago
But doesn't it have to have some charge to interact with matter in some way so as to achieve the observed effects that show that gravity from normal matter is inadequate to explain how things move on a macro scale?
- corty 6y ago
  It only has to have mass for gravitational interaction, and other charged (color, weak, em) are (mostly) excluded by observations. If there were much beyond gravity going on, we would have seen it. So our hope of detection is the remaining "not much"...
- LoSboccacc 6y ago
  > have to have some charge it can also be a new interaction driven by a completely different fundamental force. it's extremely unlikely, but "have to" is quite a strong statement for something we only know exists because observations deviate from our expectations.
  - enkid 6y ago
    How do you even judge the likelihood of something like that?
    - LoSboccacc 6y ago
      same as everything else, the more changes it requires from the current model the less likely it's the solution
      - enkid 6y ago
        That's not how I judge likelihood at all. If you were to say that there is more mathematical wiggle room for other explanations, I would be more likely to agree, but simply having to change models has no impact on likelihood. That thinking would make Quantum Mechanics, Special Relativity, Natural Selection, or Genetics unlikely. Your argument could even be used to explain why it's more likely that the earth is flat because that's the intuitive model.
        LoSboccacc 6y ago
        unlikely doesn't mean it's less good of a theory. it means the bar for verification/falsification is so much higher.

sgt101 6y ago

But doesn't it have to have some charge to interact with matter in some way so as to achieve the observed effects that show that gravity from normal matter is inadequate to explain how things move on a macro scale?

corty 6y ago
It only has to have mass for gravitational interaction, and other charged (color, weak, em) are (mostly) excluded by observations. If there were much beyond gravity going on, we would have seen it. So our hope of detection is the remaining "not much"...
LoSboccacc 6y ago
> have to have some charge it can also be a new interaction driven by a completely different fundamental force. it's extremely unlikely, but "have to" is quite a strong statement for something we only know exists because observations deviate from our expectations.
- enkid 6y ago
  How do you even judge the likelihood of something like that?
  - LoSboccacc 6y ago
    same as everything else, the more changes it requires from the current model the less likely it's the solution
    - enkid 6y ago
      That's not how I judge likelihood at all. If you were to say that there is more mathematical wiggle room for other explanations, I would be more likely to agree, but simply having to change models has no impact on likelihood. That thinking would make Quantum Mechanics, Special Relativity, Natural Selection, or Genetics unlikely. Your argument could even be used to explain why it's more likely that the earth is flat because that's the intuitive model.
      - LoSboccacc 6y ago
        unlikely doesn't mean it's less good of a theory. it means the bar for verification/falsification is so much higher.