AMA | October 2024

11278.795 - 11302.888 Sean Carroll

A rest frame can be defined by a physicist defining a rest frame, whether or not there's any stuff that is at rest with respect to that rest frame. Furthermore, if I have a box full of photons, okay, I literally have a box, a bunch of light particles bumping around inside the box, all those particles are moving at the speed of light. But there is an average amount of energy, right?