Friday, 15 February 2019

special relativity - If a neutrino has a rest frame, why can't a photon have a rest frame as well?


Concerning Rest Frame Wikipedia states:



For example, in the rest frame of a neutrino particle travelling from the Crab Nebula supernova to Earth the supernova occurred in the 11th Century AD only a short while before the light reached Earth, but in Earth's rest frame the event occurred about 6300 years earlier.



If a neutrino has a rest frame, why can't a photon have one as well?



Answer




Neutrinos have mass and travel slightly below light speed, therefore an inertial frame for the neutrino exists, while it doesn't exist for a massless photon which travels exactly at $c$. We don't know the masses of the neutrinos, but neutrino oscillations tell us that the three neutrino families must have a mass difference. For all we know, one of the three neutrinos could still be massless, but it is assumed that all neutrino families have a non-vanishing mass.


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