Neutrino travelling at the speed of light.

Feb 2017
As we know that according to relativity nothing that has mass can travel at the speed of light. But the latest study about neutrinos has shown that neutrinos have mass.

But how can neutrinos that have mass travel at the speed of light?


PHF Helper
Jun 2010
Morristown, NJ USA
My understanding is that neutrinos do not travel at the speed of light. As you note, they can't because they have a rest mass. However, their mass is so small (less than 1 millionth the mass of an electron) they travel at very close to the speed of light - so close that no experiment done to date can distinguish between the speed at which neutrinos travel and the speed of light.
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Nov 2013
New Zealand
I am curious.... How do they know it has rest mass if they haven't measured it?