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B A quick theoretical question on dark matter

  1. Jul 8, 2018 #1
    This is a theoretical question that may not be rooted in reality. I hope this was the right section. Please clear up all misunderstandings.

    Since dark matter can’t emit light, could it be possible that dark matter is ionized matter? I always thought you needed electrons to emit light. Then that doesn’t answer how they don’t catch electrons.

    Help would be appreciated.
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  3. Jul 9, 2018 #2


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    No. You need charged particles to interact with light. Ions, by definition, are charged particles.
  4. Jul 9, 2018 #3


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    But "ionized matter" means that it has CHARGE. And charged entities tend to emit EM radiation, especially when they go through varying fields. If dark matter has charge, it would have been easily detected by now.

    And no, your notion that you "needed electrons to emit light" is false. I could have just protons and jiggle them up and down and I can create EM radiation. I don't need any stinking electrons there.

  5. Jul 9, 2018 #4


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    Not only does DM not emit light, it doesn't even interact with other matter, except via gravity. They pass right through each other, which is why we don't find all sorts of bodies with DM as a component. DM doesn't clump with matter.

    No ions are gonna do that.
  6. Jul 10, 2018 #5


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    Ionized matter is plasma, and plasmas are certainly not dark. Fully ionized plasma will not emit atomic line radiation, but it will still emit free-free bremsstrahlung, and if there is a magnetic field, then also synchrotron radiation. Also, depending on the density of the plasma, light above the plasma frequency will be reflected. Light will also be refracted or absorbed by the plasma, so it is anything but invisible.
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