### Question

In a matter-antimatter reaction, is all the material converted into energy? If not, what is the efficiency of the reaction?

Yes, the reaction between matter and its corresponding anti-matter particles is 100% efficient, converting all of the mass into energy. If you want to find the amount of energy produced in any such reaction, just multiply the total mass (particles plus their anti-particles) in kilograms by the speed of light squared (9 x 1016) and you will get the result in joules.

Because this reaction is 100% efficient, cosmologists believe that were it not for an asymmetry that favors matter over antimatter, the Big Bang may have annihilated ALL matter and produced a Universe filled with only energy.
Answered by: Paul Walorski, B.A. Physics, Part-time Physics Instructor

When it comes to Anti-matter, the annihilation effect converts the particle or particles that are opposite the anti-particle. An example is the electron and positron. They annihilate each other completely and the resultant energy is high end gamma ray radiation. If, on the other hand, there is a hydrogen ion and a positron, the end result is a proton (maybe a neutron, depending on the isotope) and gamma radiation. With anti-MATTER it depends on the particles used. Interesting enough, If you reverse the process, by starting with the high end gamma ray radiation, you can create electron/positron pairs. This is much much harder to do. To figure out the output (or input) energy, use Einstein's energy equation: E=mc2.

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### Science Quote

'We should take care not to make intellect our god; it has powerful muscles but no personality.'

Albert Einstein
(1879-1955)