The Origins of Neutrinos in the Big Bang

Neutrinos don't move at the speed of light, which means they have some mass. But then is that the main way that we know they have mass? So there's another really fascinating clue which comes from the Big Bang. We think that a lot of neutrinos were made in the Big bang. And by studying the relics of the Big Bang, we could actually get some clues as to like how many neutrinos there were. and we can even figure out something about the mass of those neutrinos.