I should at some time try to be a little more comprehensive than what will follow, I have elsewhere said how photon is very special: zero mass, vector spin state, fastest particle, force carrier of electromagnetic force — actually Maxwell waves and so on.
We can not talk about the position of the photon in relativistic quantum mechanics — we do not have a complete consistency but still. Also photon is it’s own anti-particle …
I was just reviewing a little about the photon: in 1600 Galileo was trying to measure the speed of light, at that time light speed was thought to be infinite, that is; instantaneous. The light is there in alpha-centauri, and it is there in here, at the same instant.
Galileo took his postdoc (pun) to a distant place and took a light source and uncovered it so his postdoc can see it remotely, then he would uncover his, upon seeing this and Galileo would see that and note his time.
ha ha ha that’s silly Galileo, Galileo’s ghost: yes Mohan, easy for you to say that, how about detecting dark matter? Xenon, ha ha ha ha ha ha … Xenon will detect the dark matter, ha ha hahhh haah a
Needless to say Galileo failed or rather he measured light speed to be infinite in line with the PDG (pun) publication of 1600.
A few years later (1849) Fizeu (France) performed his experiment. This was the first experiment that provided the correct result. Compare to the most precise