Can a Human See a Single Photon? (1996)
I’ve been aware of this fact as Feynman points it out in the course of the lectures, but find it totally nuts — there is some sense of scale I’m missing.<p>Matter consists of discrete chunks, atoms, but these chunks are so infinitesimal and numerous that there is no question of seeing them and any effect involving a handful of them is far, far below the human scale.<p>Light also comes in chunks, and the number of these chunks should be comparable to number of atoms since, e.g every single atomic transition generates a photon. Actually they should be far <i>more</i> numerous as they are massless and easily created, destroyed.<p>Yet, somehow, they are not far below the human scale of detection — as few as 5 (!) results in a perceivable flash.<p>What am I missing here? (Obviously this boils down to a numeric estimation and the numbers are what they are — my question is why do the numbers wind up even remotely in the human ballpark.)