Posts: 900
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Joined: Feb 2022
Kornee
Mar 23, 2023 02:24 PM
QED/QFT buffs will quickly point out or anyway claim it's impossible to come up with a physical picture of what a photon 'really looks like'. All down to math that works.
I recall one thread at PF where a member asked if there was proof photons can only be emitted if an absorber exists somewhere else in the universe.
So I did a very easy experiment. Laser pointer shone through a slightly frosted clear plastic plate. Most of the beam transmits but it's easy to note the intensity of the scattered part. Aimed first at the ground where essentially full absorption of the transmitted beam occurs. Then up at the clear night sky. No discernible difference in scattered intensity. Lack of a mysterious dimming indicating that photons don't need to 'know in advance' that a distant absorber is there before being emitted.
Given that light from very distant galaxies arrives with minimal scattering absorption, and has traveled from a time when everything was much more crowded, light currently shone into the great yonder will have an indefinitely easier journey as the ever expanding universe continually thins out. Further, cosmic stretching of wavelength will mean photons emitted by a given atomic orbital transition will sooner or later no longer be able to be absorbed in reverse fashion.
I can't recall the exact reaction from the forum member, but it was probably silence.
