If I was in a totally dark room, and I had a machine that could emit a single photon across my field of vision, but not directly AT my eyes, would I be able to see it? If so, how?
Answers (1)
No, not a chance. Unless the photon enters your eye you will see nothing. I think you've forgotten how the eye works.... the retina at the back of your eye is stimulated by energy (light aka photons) which sends a signal to the brain along the optic nerve and in a complicated process creates an "image". You cannot see a single photon as no photons are being reflected off the object to enter your eye. If the object is reflecting nothing (absorbes everything) it is unable to be observed and if there is nothing for it to reflect (absence of all forms of energy) then it cannot be observed.
So, no you could not see a single photon unless other photons were being reflected off it and even then the number of photons a single photon could reflect would be one (repeatably for sure) and your eye, the human eye, is simply not sensitive enough to detect a single photon.