But then I noticed they only emit light when they’re moving. And boy, do they emit a lot of it. I mean, not a lot from our point of view, but for a tiny single-celled organism it’s a ton.” “And how is that relevant?” “I did some back-of-the napkin math. And I’m pretty sure that light is how they move around.” Stratt raised an eyebrow. “I don’t follow.” “Believe it or not, light has momentum,” I said. “It exerts a force. If you were out in space and you turned on a flashlight, you’d get a teeny, tiny amount of thrust from it.”
