# Neutrinos and Speed of light

Einstein's Special Theory of relativity postulates that the speed of light is same for all frames.

Suppose a neutrino is there moving at the speed of light. Then will that neutrino also be flowing with same speed for all frames or is this a special property of EM waves?

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I have attempted to clarify the question, please let me know if this is not what you meant. – Manishearth May 13 '13 at 10:06

Firstly:

*in a vaccuum

*inertial

Einstein's Special Theory of relativity postulates that the speed of light in a vacuum is same for all inertial frames.

suppose a neutrino is there moving at the speed of light

For a neutrino to move at $c$, it has to be a massless particle. We're not sure of that yet. Apparently the existence of neutrino oscillations prove that neutrinos have some rest mass (h/t Neuneck).

But yes, if any particle moves at $c$ in one inertial frame, it does so in all inertial frames. An example of this would be the gluon.

However, if the neutrino has mass, it will never be able to reach $c$ in any inertial frame. Particles going at subliminal speeds cannot be sped up to $c$, and particles moving at $c$ cannot be slowed down.

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Actually, having observed neutrino oscillations from all families to all others we are sure that neutrinos do have a non-zero rest mass. – Neuneck May 14 '13 at 6:36
@Neuneck: Hmm, true. I'll edit that in in a moment. – Manishearth May 14 '13 at 6:37