# Do neutrinos travel faster than light? [duplicate]

There are particles like tachyon which moves faster than light theoretically,does this holds good enough for neutrinos?

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• I see you are a student. This site is usefule of particle physics and astrophysics hyperphysics.phy-astr.gsu.edu/hbase/index.html – anna v Sep 19 '17 at 5:34
• In the hyperbolic geometry of our spacetime, time and distance are not two independent quantities. They depend on each other and this works out in such a way that in this geometry there are no speeds faster than light. A particle cannot travel faster than light not because there is such a speed, but the particle cannot get to it. No, there is simply no such a speed in this geometry. As a rough visual analogy, think of going to the North on the globe. Once you are at the North Pole, can you move any further to the North? No, and it is not because you can't, but because there is no such a place. – safesphere Sep 19 '17 at 5:37

Do neutrino travels faster than light?

No.

There are particles like tachyon which moves faster than light theoritically,does this holds good enough for neutrinos?

No, there aren't. No, it doesn't hold even remotely.

• Theoritically it is proved that tachyons move faster than light – hitesh Sep 19 '17 at 3:58
• @hitesh No it isn't. Tachyons are particles which possess imaginary rest mass, but at the level of quantum field theory, even tachyonic particles are restricted to traveling below the vacuum speed of light. – J. Murray Sep 19 '17 at 4:08
• @J.Murray - This is technically correct, but misleading. Tachyons simply don't exist in any stable quantum theory. A tachyonic excitation signals instability of the theory (vacuum) which implies that the vacuum decays to give the usual massive excitations. In other words, there are no tachyonic particles. Also I should say, that the very definition of tachyon (whether they exist or not) is a particle that travels faster than light, nothing more. – Prahar Sep 19 '17 at 4:39
• @Prahar what you said is technically correct, but misleading :) The original question can be paraphrased as "do things travel faster than light?" and the most straightforward answer is "no". – Prof. Legolasov Sep 19 '17 at 4:53
• @Prahar You're right. I should have said that tachyonic fields have complex mass parameters, but that their excitations are particles with real masses, so tachyonic fields do not give rise to tachyonic particles. I suppose one could debate as to whether or not the label "tachyon" should be attached to the original FTL intent+etymology or to the immediately subsequent "imaginary mass" idea ... – J. Murray Sep 19 '17 at 4:56

No, neutrinos do not travel faster than light. In 2011, an experiment called OPERA claimed to measure superluminal neutrino velocities, but it was later realized to have been an error.

At least two of the three types of neutrino have nonzero rest mass, based on measurements of neutrino oscillation. It's possible that the third neutrino is massless, though this seems unlikely. If it is massless, then it would travel at the vacuum speed of light - otherwise, like the other two, it would travel subluminally.

The question of neutrino masses and their origin is far from settled, and is an active area of research.

• It is not massless ,ts rest mass is 0 ,but dynamic mass is there – hitesh Sep 19 '17 at 3:57
• @hitesh I'm not sure what you're talking about, but anytime somebody says "massless" they are referring to rest mass. Dynamic mass is an unhelpful and outdated concept, in my opinion, but to each their own. – J. Murray Sep 19 '17 at 4:02
• My fault @J.Murray but to be more clear i said that – hitesh Sep 19 '17 at 4:04
• @hitesh - Dynamic/relativistic mass is just a wrong and extremely misleading concept. Don't bother learning it at all. – Prahar Sep 19 '17 at 4:40