If the action of least principle says light needs a destination what happens when we shine a laser into the dark region of the microwave background radiation?
Alternatively, if we put a light source in a box made of a material that does not absorb light (a perfect reflector perhaps) and we could measure the energy use of the light device, would any light ever be emitted? In this case the box would be opened eventually so it's not as good as finding a real void.
