WMAP results / Dark Matter / Dark Energy

Discussion in 'Physics & Math' started by GundamWing, Feb 26, 2003.

  1. GundamWing Registered Senior Member

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    So, back to dark matter and WMAP...

    If dark matter emits no light, does it at least 'interact' with light in any way? (all jokes aside, does it actually 'suck light'? what about 'matter'? for something to be truly dark, it must either (1) suck light, or (2) be transparent to light so that light cannot 'see it'). Or is it possible that 'light' bends completely around 'dark matter' and just skirts by?

    Also, does the E=mc^2 relation hold for dark matter/energy?

    Any ideas/knowledge? :m:
     
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  3. synergy Registered Senior Member

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    It could reflect light, just be of low density in space so no large clumpings are seen. Not likely from what little I know of it, though (which is VERY little, although I'm not really sure how much there IS to know as of yet).
     
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  5. chroot Crackpot killer Registered Senior Member

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    It presumably interacts with light just like normal matter, except it never emits any light. Its primary mode of detection is via its gravitational effects.

    - Warren
     
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  7. GundamWing Registered Senior Member

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    Well, if it presumably interacts with light as ordinary matter, yet it emits no light -- then what happens when it absorbs the light, if not excitation and emission? It'd be nice if this could be tested in a lab, unfortunately, we'd probably need a handful of darkmatter (which I hear, possibly fictitiously, is more ultradense than your average neutron star, or maybe i'm getting it mixed up with the stuff of neutron stars, which as I recall are regular atoms with collapsed or highly squeezed electron shells).

    If it absorbs light, and presumably gets excited by it, it must translate this into some form of emission or possibly motion. So (1) it moves, or (2) it creates some waves that disperse the energy. Given that there must be a lot of dark matter out there absorbing light, and that we can't detect ubiquitous levels of gravitational waves all over the place, it must be either a rare event that it emits gravitational waves, or it simply doesn't work like this. The other possibility is that it moves somehow. Of course, since energy/momentum must be preserved, and given the relative density of dark matter to normal matter or photons, it must not be affected 'much' by a little absorption here and there. On the other hand, if there is no 'other outlet' for the energy to disperse, the dark matter could continually absorb energy and would gain appreciable kinetic energy in the process or possibly may grow 'darker' (

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    )...

    One thing I can't understand is ... if the universe is 73% + dark matter / energy, why is it that we can't scoop up some right now? It should be more plentiful than the air we breathe -- I mean, you'd expect that it'd be "easy" to find the majority rather than the "minority" in a population, so where'd it all go? Where is it hiding?

    And Warren -- what are these 'gravitational effects' one might observe?

    Ok, so anyway, i'm floating way out there now. Returning to earth.

    peace. :m:
     
  8. chroot Crackpot killer Registered Senior Member

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    We don't know. It may not interact with light. Since it can't be baryonic (protons and neutrons), it might be some exotic kind of uncharged particle that does not interact with light. A neutrino, for example, does not interact with photons -- but it looks like dark matter isn't neutrinos either.
    Neutron stars are literally stars made out of neutrons -- like a giant atomic nucleus. Dark matter is nowhere near this dense!
    We presume that if it does interact with light, its so massive that it doesn't move much.
    It quite possibly could be all around us right now -- but we haven't developed the means of detecting it. They may be some kind of extremely massive, yet extremely weakly interacting particles. If we can't detect it with collisions or EM phenomena, we can't detect it at all right now. We currently lack the technological sophistication to measure gravitational effects on the required scales (mainly because gravity is so impossibly weak).

    - Warren
     
  9. Persol I am the great and mighty Zo. Registered Senior Member

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    What happens to the electrons though? The only thing I could find was
    Do the electrons just form a 'cloud' on the surface or do they disperse?
     
  10. GundamWing Registered Senior Member

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    probably would form a dense plasma that would either swirl around it or whatever...couldn't even imagine this one.

    but yeah, i blundered my original statement, i meant "neutrons" not atoms haha. wasn't watching what i was typing.

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  11. chroot Crackpot killer Registered Senior Member

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    The electrons and protons are essentially squeezed together -- the inverse beta decay becomes energetically favorable, so the electrons and protons combine and emit electron neutrinos.

    - Warren
     
  12. synergy Registered Senior Member

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    inverse beta decay-
    in other words, for those with Q's, the electrons and protons combine to form the neutrons and emit neutrinos (analogous but not exactly like fusion versus fision for atoms) - these neutrinos would be the anti-version of those emitted in beta decay when a neutron decays into a proton and electron. (just clarifying

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  13. GundamWing Registered Senior Member

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    but e- and p+ could be used to form hydrogen gas, so presumably, if you compress hydrogen beyond its 'solid' state you generate neutrinos? (of course, hydrogen compressed beyond a solid state is ridiculously high pressure, kind of like the conditions near a neutron star)....? :m:
     
  14. chroot Crackpot killer Registered Senior Member

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    If you compress ANYTHING, it will eventually reach a state like a neutron star.

    - Warren
     
  15. GundamWing Registered Senior Member

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    true but i was referring to the reaction between protons and electrons generating neutrinos.... i never spent much time with particle physics and the reactions.
     

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