Neutrino's are very small though they have mass. Because of that it is probably that the don't have a speed faster than photons.

But is it in all events, like supernova's or else events, where it is possible that we first receive their neutrino's instead of their light?

Perhaps gravity or other interactions could change something in their way to earth?

  • $\begingroup$ Supernovae are thought to emit neutrinos immediately, as the core collapses. Photons are emitted from the surface a short time after this. So, the neutrinos don't actually travel faster - they are just released first. $\endgroup$
    – Andy
    Mar 29, 2016 at 16:12
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    $\begingroup$ Incidentally photons might move slower than neutrinos in reality, due to scattering on the way. Is this what your question is about? (I think there was a recent paper about this somewhere...) $\endgroup$
    – Andy
    Mar 29, 2016 at 16:41
  • $\begingroup$ Ok, that is something interesting. And neutrino's aren't scattered because they are neutral?! And do they behave the same in curved spacetime, or is it also possible that the geodesic of neutrino's are 'shorter'? $\endgroup$
    – Marijn
    Mar 30, 2016 at 8:09
  • $\begingroup$ If you're interested in neutrino arrival times, have a look at Jack's answer and especially SN1987A. That's an example of this difference being noticed. $\endgroup$
    – Andy
    Mar 30, 2016 at 8:33

1 Answer 1


Yes. When a core collapse supernova happens, it takes a few hours for the shock wave to reach the surface and "break out" (when we first "see" it). Meanwhile, the neutrinos can escape nearly directly once they reach the top of the core.

Of course, as you wrote, photons travel slightly faster, so if the SN is far enough away, the photons might overtake these neutrinos. However, I have not done the calculation to see if the universe is big enough.

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    $\begingroup$ Neutrons from such a supernova have been observed (2-3 hours before the photons) and the supernova SN 1987A was close-by in the Large Magellanic Cloud. This is well-known. See this wikipedia article en.wikipedia.org/wiki/SN_1987A . $\endgroup$ Mar 30, 2016 at 4:18
  • $\begingroup$ We still cannot rule out that Neutrinos do in fact travel at the speed of light. $\endgroup$
    – Dean
    Mar 30, 2016 at 8:54
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    $\begingroup$ Not so. We know neutrinos have mass because they oscillate between different species (ie they transform from one species to another, and this requires mass). Since they have mass, special relativity forbids them from achieving light speed. $\endgroup$
    – eshaya
    Mar 31, 2016 at 15:59

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