A friend asked me a question that has me wanting to copy the tree in the forest question. If a star is shining and there is no one there to see it, is there light?
That was not her question, of course. Her question was what happens to light once it passes us. She is asking about the first light that reaches us - those first photons. Where does it go? Good question? Unlike sound, light is particles (photons). Even though they are massless, they are something real that is traveling. Can her question even be answered without the question I asked above - along with its answer? I am thinking the answer to my own question is "no". Then her answer would be it goes on forever until there is no one to see it.
So, (1) what happens to light once it passes us?
And (2) what happens to light if there is no one to see it?