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Thread: Why Do Matter and Antimatter Annihilate?

  1. #1 Why Do Matter and Antimatter Annihilate? 
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    Apologies if this has been posted before, I did a search but did not find anything similar.

    My question is why do matter and antimatter annihilate? As I understand, matter and antimatter have the same mass and spin state but opposite electric charge. Is it due to the charge difference? If so, what about neutral particles like the neutron or even the photon? But neutrons consist of quarks which do have charge, the total combination being zero.

    The Pauli exclusion principal says that two fermions cannot occupy the same energy state. But to annihilate, an electron and positron for example, must, even if it is for the briefest of time, occupy the same state?

    And finally, what if you collided a proton and an electron together, would the result be similar to an electron-positron collision? But in the case of an electron-proton collision, the kinetic energy being converted to other forms of energy would be the "mechanism"?


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  3. #2  
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    You are asking several questions. As far as "why", that is a question no one can really answer - it is just a fact of physics. It has nothing to do with charge - neutrons and anti-neutrons will annihilate.

    The Fermi exclusion principle refers to two particles of the same kind, like two electrons, not to an electron and a positron.

    Electron proton collision will not lead to annihilation. There are several possible results depending on the energies of the particles. Possibilities include formation of a Hydrogen atom, simply scattering, or (at very high energies) formation of a neutron.


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  4. #3 well 
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    becuse thay (the same thing but ) move in difrent direction of time
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  5. #4  
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    That's a disproven hypothesis. See here: http://en.wikipedia.org/wiki/One_electron_universe.
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  6. #5 Re: Why Do Matter and Antimatter Annihilate? 
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    Quote Originally Posted by MoJo98221
    My question is why do matter and antimatter annihilate? As I understand, matter and antimatter have the same mass and spin state but opposite electric charge. Is it due to the charge difference?
    Not quite. It's because they have the opposite chirality, see http://en.wikipedia.org/wiki/Chirality_(physics).

    Quote Originally Posted by MoJo98221
    If so, what about neutral particles like the neutron or even the photon?
    There's no such thing as an antiphoton. As mathman said neutrons annihilate with antineutrons. and this isn't because of charge difference. Neutrons do have "internal charge", we know this from the magnetic dipole moment, but the net charge is zero. So the annihilation isn't because of the charge difference. Again it's because of the opposite chirality, which is related to charge, but not quite the same thing.

    Quote Originally Posted by MoJo98221
    The Pauli exclusion principal says that two fermions cannot occupy the same energy state. But to annihilate, an electron and positron for example, must, even if it is for the briefest of time, occupy the same state?
    It's more like two opposite spins coming together and cancelling.

    Quote Originally Posted by MoJo98221
    And finally, what if you collided a proton and an electron together, would the result be similar to an electron-positron collision?
    No. The electron and proton are different in other ways. They don't annihilate.
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  7. #6 Re: Why Do Matter and Antimatter Annihilate? 
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    Quote Originally Posted by MoJo98221
    "]If so, what about neutral particles like the neutron or even the photon?
    There's no such thing as an antiphoton. As mathman said neutrons annihilate with antineutrons. and this isn't because of charge difference. Neutrons do have "internal charge", we know this from the magnetic dipole moment, but the net charge is zero. So the annihilation isn't because of the charge difference. Again it's because of the opposite chirality, which is related to charge, but not quite the same thing.
    when a wave of photon going forward it statistic annihilate it self
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