1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    Astronuc

    User Avatar
    Staff Emeritus
    Science Advisor

    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
    http://hyperphysics.phy-astr.gsu.edu/hbase/particles/lepton.html#c3

    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.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook