Can a Human See a Single Photon? (1996)

TL/DR: No, we cant. The retina itself can respond to a single photon, but we are not retinas. Instead, the eye filters out this low light sensitivity lest we go crazy with the resulting visual noise at night.

Re: Can a Human See a Single Photon? (1996)

#5

Post by high_byte » Fri, Jan 20, 2023, 1:36 PM UTC

sbaiddn wrote: post #4

Question in the title -> No. TL/DR: No, we cant. The retina itself can respond to a single photon, but we are not retinas. Instead, the eye filters out this low light sensitivity lest we go crazy with the resulting visual noise at night.

Not 1 but 5-9 photons, still less than billions :)

pretty amazing

Re: Can a Human See a Single Photon? (1996)

#6

Post by superposeur » Fri, Jan 20, 2023, 1:37 PM UTC

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.

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.

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 more numerous as they are massless and easily created, destroyed.

Yet, somehow, they are not far below the human scale of detection — as few as 5 (!) results in a perceivable flash.

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.)

Re: Can a Human See a Single Photon? (1996)

#7

Post by ilyt » Fri, Jan 20, 2023, 1:37 PM UTC

sbaiddn wrote: post #4

Question in the title -> No. TL/DR: No, we cant. The retina itself can respond to a single photon, but we are not retinas. Instead, the eye filters out this low light sensitivity lest we go crazy with the resulting visual noise at night.

So that would be yes but our noise filter in brain doesn't let us see it

Re: Can a Human See a Single Photon? (1996)

#8

Post by Eddy_Viscosity2 » Fri, Jan 20, 2023, 1:43 PM UTC

You can't see a photon, but you can taste a proton.

Re: Can a Human See a Single Photon? (1996)

#9

Post by pavlov » Fri, Jan 20, 2023, 1:55 PM UTC

superposeur wrote: post #6

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. 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. Light also comes in chunks, and the number of these c…

Maybe seeing in the dark is simply so valuable that evolution has created extremely light-sensitive eyes for many species?

If there was a molecule whose detection in tiny amounts would give a species a competitive edge, we might have noses capable of detecting 5-molecule amounts of this substance.

Re: Can a Human See a Single Photon? (1996)

#10

Post by bitexploder » Fri, Jan 20, 2023, 1:57 PM UTC

high_byte wrote: post #5

sbaiddn wrote: post #4

Question in the title -> No. TL/DR: No, we cant. The retina itself can respond to a single photon, but we are not retinas. Instead, the eye filters out this low light sensitivity lest we go crazy with the resulting visual noise at night.

Not 1 but 5-9 photons, still less than billions :) pretty amazing

It’s cool our brains have that as a heuristic for whatever reason. Wonder if you could train yourself to see 1-3?