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Old Jul 25th 2017, 09:14 AM   #1
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Neutrino travelling at the speed of light.

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?
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Old Jul 25th 2017, 09:57 AM   #2
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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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Old Jul 25th 2017, 02:18 PM   #3
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I am curious.... How do they know it has rest mass if they haven't measured it?
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Old Jul 25th 2017, 03:45 PM   #4
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Originally Posted by kiwiheretic View Post
I am curious.... How do they know it has rest mass if they haven't measured it?
There is some good evidence that neutrinos have mass. For an overview I suggest you take a look at this wikipedia site, and see the section titles "Flavor, mass, and their mixing": https://en.wikipedia.org/wiki/Neutrino
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