...shouldn't it: 1. become asymptotic to c as you pump more energy into it? 1a. don't I need to a lot more energy to move it a little closer to c? 1b. can't I compare it with a beam of light to confirm that light is faster? 2. be able to come to rest as you take energy away from it? The reason I am confused is, I have read that for all intents and purposes, a neutrino could be considered massless and yet, it has some non-zero mass! It's like reading that a neutrino half-pregnant: shouldn't a particle either have no mass and always travels at the speed of light, or have mass and be subject to the same characteristics that apply to all massive bodies?