I’ve seen a few articles about neutrinos recently, high energy ones, super fast ones, ones from open space, others from “sources”, and my understanding of the particle is that it’s very hard to detect, passes through light-years of lead without interaction, etc. don’t headings and speed require multiple readings to make? How do we know the velocity of a neutrino when we can only detect them at single points?
Just like the first smash when you’re playing pool, quite a few balls are going down the table while a couple might go off up the table. There’s a net movement down the table. It gets more complicated because we’re talking balls of different masses and a bit of relativistic speeds, but analysis will reveal what those masses are and hence the net direction of the momentum and thus the direction of the velocity.