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Matter/antimatter annihilation question

  1. May 19, 2008 #1
    Although this question is simple it's been bugging me:

    If you were to take one kilo of antimatter and annihilate it with one kilo of matter is the energy (using E=mc^2) released proportional simply to the mass of the matter or to the sum of the masses of both the matter and antimatter?

    So is the energy released :

    E=mc^2=1*299792458^2= 89875517873681760 Joules

    or E=mc^2=2*299792458^2= 179751035747363520 Joules


    Cheers in advance :tongue:
  2. jcsd
  3. May 19, 2008 #2


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    Staff: Mentor

    If one has 1 kg of matter and 1 kg of anti-matter, then energy related to mass is 2 kg. However, the energy is not completely released as kinetic energy or EM energy directly.

    While positron + electron annihilate to produce two gamma rays, proton + antiproton produce pions (or rarely Kaons), which decay to muons (if pions are charged) or gammas or e+-e- pairs (if pions are neutral), and muons decay to electrons and neutrino/anti-neutrinos. So there is some mass retained, but very briefly.

    See - http://hyperphysics.phy-astr.gsu.edu/hbase/particles/piondec.html#c1

    Review the half-lives of pions and muons.

    Given the tremendous energy from the first annihilations, it would be difficult to contain the masses of matter and anti-matter to ensure complete annihilation.
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