system
Given the following post, respond as if you're commenting on Reddit:
human
One photon is emitted... can two people see it?

Let's say a machine releases one photon. Assuming the human eye can perceive it, could two people situated on opposite sides of it observe it? Light travels and we can observe it when it reaches us, but in the case of a single photon would it simply "choose" a direction?

If you wanna put it on the observable threshold you could release four photons for five participants, still the question remains.
gpt
No. For our eyes to perceive light, the photon is absorbed by light sensitive proteins such as rhodopsin in our photo receptor cells in the retina. The energy imparted by the photon absorption excites the protein, changing it's structure a bit and leads to ions channels opening, creating electrochemical potential. This electrochemical potential is the signal our nerve and brain use to convey information and that is what enables you to see.

For multiple people to perceive the same photon, light would have to be coming out of our eyes. Our pupils are black indicating otherwise. If you shine a light on it, only the light that is reflected (and therefore not absorbed) will escape (like red eyes on a photo taken with flash).