PHYSICS WORLD
Across the universe – what is the lifetime of a photon?
The photon – the quantum of light or other electromagnetic radiation – is normally considered to have zero mass. But some theories allow photons to have a small rest mass and one consequence of that would be that photons could then decay into lighter elementary particles. So if such a decay were possible, what are the limits on the lifetime of a photon? That is the question asked by a physicist in Germany, who has calculated the lower limit for the lifetime of the photon to be three years in the photon’s frame of reference. This translates to about one billion billion (1018) years in our frame of reference.
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