What would happen if energy would be applied to a photon in some direction? Since photons always travel at c, it shouldn't change their velocity no matter from what direction the energy would come, but what does applying energy do? I could imagine that if you applied energy from the front that the photon would lose some of its energy, and that if energy is applied to the back that some energy is given to the photon. But what happens if you apply energy from the sides, does the path of the photon change? Or is just impossible to apply energy making this a stupid question?