# Matter/antimatter annihilation question

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

?

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Astronuc
Staff Emeritus
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.