# How fast do neutrinos actually go?

 Sci Advisor P: 905 How fast do neutrinos actually go? Neutrinos from nuclear reactions have energies on the order of 1 MeV. Their mass if nonzero is thought to be around .1 eV. This means $$\gamma=10^7$$ But $$\gamma={1\over\sqrt{1-\beta^2}$$ so $\beta$ which is the ratio of speed to speed of light, is veryvery close to 1: $$1-\beta\sim 10^{-14}$$