That is interesting. But then what is the explanation? Medium is not really anything concrete, we call that a collection of atoms isn't it?
By default there is only one medium, the vacuum of space, in which there can be various densities of "stuff", particles/atoms/molecules.
So then, it becomes some sort of quantum thing, a probability of photons bumping/being captured/emitted or?
Simplifying from memory, light propagation in medium can be treated on two levels (some phenomena require the 2nd, quantum, level):
- classical (Maxwell): electrons in the medium oscillate out of phase in response to the incident wave; this results in a new wave, propagating somewhat slower
- quantum (QED): incident photon couples to matter excitation (an exciton), producing a pseudo-particle called a polariton; it has a non-zero effective mass, resulting in propagation slower than c
As mentioned above, it absolutely isn't "absorbing and re-emitting". If that was the case, transparent materials would not exist (only milky/clouded ones), as re-emission is in random direction. However, photon propagation in the Sun is just that, a (very long, counting from the core to photosphere) random walk.
Thank you, that is very interesting!
I remember seeing something about absorption/emission and seemed to make some logical sense. But indeed if emission is in a random direction then transparent materials wouldn't make sense.
Four years on a shared remote machine before building the local backend is a good lesson in when to invest in dev tooling versus living with the workaround.
