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Is dark matter a cop-out?

  1. May 17, 2010 #1
    I have no quantitative understanding of current cosmology, so go easy.

    The intent of this post is to promote civil debate, not critisize current science.

    So basically, I look at astrophysicists and I think of them as saying "oh, because there are observations we don't understand, there MUST be a mysterious, magical substance leading to these behaviors". IE, I'm thinking that dark matter/energy is a cop out. To my understanding, with our current technology, this theory isn't really even falsifiable.

    Now, can someone with more knowledge than me (that's basically everyone on this forum), correct me if I am wrong?
  2. jcsd
  3. May 17, 2010 #2
    It is quite falsifiable. Saying that "oh it's just dark matter" and then stopping would be a cop out, but people aren't doing that. What people are doing is to say, "things seem to work out nicely if we assume that there is this much dark matter, composed of this type of substance, which reacts this way with matter, and doesn't react in this other way."

    A lot of what people are doing is to use process of elimination. Let's assume that the dark matter is made up of light particles. Well, if it were made up of light particles then it would smear out large scale structure of the galaxies. Well, lets suppose, it's made up of protons and neutrons, in that case the galaxies aren't clumpy enough. Repeat for about ten years, and you come up with very good ideas for what it is and what it isn't. Well, lets suppose there is no dark matter and our understanding of gravity is wrong, then things clump in the wrong way. Let's suppose dark matter is made of black holes. Then if you look at distant stars, you should see a flicker if one of them passes in front of a star. We looked. We don't see that. Scratch that from the list.

    One reason dark matter is getting a lot more firm, is that it's no longer quite as dark as it was before. If you have clumps of dark matter, then you ought to see it distort the light of distant quasars, and we've gotten to the point that no only do we see these distortions, we can use them to map out where the dark matter is and isn't.

    Saying it's some mysterious magical substance that we can't understand would be bad. But what people are doing is to try to figure out what that substance is, and once you make some educated guesses, you then have some idea where to point your telescope and what to look for,
  4. May 17, 2010 #3
    Also, I think it's the situation that either dark matter/dark energy exists *or* there is something really basic about gravity that we are getting wrong. If you could add one mystery term to gravity and get dark matter, then people would go with that, but no one has gotten that to work.

    It so happens that you can get dark energy to work nicely by adding one term to the gravity equation, so that's one thing that people are looking at, but right not observations haven't ruled out other things.

    It's also possible that we are just basically misinterpreting what we see, but as time passes and we have more and better observations, that becomes less and less likely.
  5. May 17, 2010 #4
    Thank you for clearing that up for me :)
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