Does light lose any any energy in a vacuum?

[Red monkey]

Would there be any energy loss at all from a beam of light travelling in a vacuum?

 

[Bill_K]

Nope. The energy of a light beam of course is frame dependent - can be red-shifted or blue-shifted according to the rest frame of the observer. But if you stay with the same rest frame and ask, does the light lose energy just because it has been traveling a long distance, the answer is no.