# 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?

-

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.
There are 3 types of neutrino: electron neutrino $\nu_e$, muon neutrino $\nu_\mu$ and tau neutrino $\nu_\tau$, here's image that shows masses and other details: click here (Note that Electron neutrino has very low mass $<2.2$ $eV$ but it's not zero) –  Gigi Butbaia May 2 at 18:28
It could still be $0$. Moreover, the flavor eigenstate of the neutrino does not coincide with the mass eigenstate, therefore the mass of an $\nu_e$ is ill defined. To be precise, one'd need to write $\nu_1 < 2.2$ eV, where $1$ denotes the lightest mass eigenstate of the neutrino. –  pfnuesel May 2 at 18:46