Do photons exist outside of time

Decay of photons not excluded

According to today's understanding of electromagnetic force, the photon, i.e. the light quantum, is massless. However, this is by no means prescribed by the theory: photons could also have a very small mass and possibly even decay into even lighter particles. Julian Heeck from the Max Planck Institute for Nuclear Physics in Heidelberg examined the cosmic background radiation and found that the data are compatible with the thesis of mass photons with a limited lifespan.

From past experiments it is known that the rest mass of the photon, if it actually exists, is less than 2 × 10-54 Must be kilograms. This value is tiny even in elementary particle physics - according to the mass-energy equivalence, it corresponds to an energy of about one attoelectron volt, i.e. 10-18 eV. Usual photon energies are considerably higher: A visible photon has an energy of around 1 eV, radio radiation consists of photons in the range of 10-9 eV.

Influence of mass photons on the cosmic background radiation

The difference between the largest possible rest mass and the energy according to the mass-energy equivalence is therefore very large. For this reason, the behavior of the hypothetical mass photons is subject to the rules of the special theory of relativity. Accordingly, due to the time dilation, the particles have a longer lifespan, the greater their energy is, from our point of view. An observer is therefore more likely to discover a decaying photon if it has a low energy. Then the life time seems shorter to the observer. The best chances of success for a decay detection are offered by photons that were emitted a long time ago and have a low energy.

Cosmic background radiation is an ideal source: Today it shines in the microwave range and its light comes from the time of the Big Bang around 13.8 billion years ago. Heeck examined the data from the COBE satellite, which provided the most accurate measurement of the spectrum of cosmic background radiation to date. The scientist comes to the conclusion that the lifetime of photons with an assumed mass of 2 × 10-54 Kilograms must be at least three years. This may sound like an extremely short time by cosmic standards, but the effects of the special theory of relativity mean that a photon of cosmic background radiation in the microwave range has a lifespan of three quadrillion years from our point of view. This agrees with our observation that most of the photons have apparently not yet decayed.

“The study of photons and light has always caused surprises that have advanced physics, be it in quantum theory or relativity. A precise analysis of the photonic properties such as mass, charge and lifespan is therefore always a touchstone of our current physics knowledge, ”says Heeck. A more detailed understanding of what happened shortly after the Big Bang could help to further refine the results.