The Mass of Neutrinos in the Universe

An electron has like 500,000 electron volts. Neutrinos have mass much closer to zero than anything we've ever seen before. They're weird compared to the other particles in even another way. Like if you create an electron neutrino and shoot it through space and then wait like a light ear, two light ears and try to measure it, you might discover it's now a muon neutrino or a tau neutrino.