To be pedantic, photons never accelerate. They only ever travel at one speed in one direction
And as they're massless, photons do not experience time. Regardless of how far a photon travels, from its perspective, the journey takes no time.
A photon would somehow experience the big bang, the heath death of the universe and everything in-between all at the same time.
They don't accelerate, but can travel at different velocities in different mediums.
For example light travels faster in air than in water and fastest in a perfect vacuum.
I believe they still travel at the speed of light, but are regularly absorbed and re-emitted in a way that makes the effective speed less than c.
How do reflections work? Aren't changes in direction caused by acceleration? Also aren't photons affected by the gravity of black holes? How does that work?
Reflections involve the material absorbing and re-emitting photons back the other direction.
The curvature of light from gravity is actually space-time itself being curved by mass. The light continues on a straight path through a curved space-time. It looks like it changes direction from the outside, but that’s just the shape of the universe in that area.
That’s why we feel gravity. The space-time around earth is curved inward, so going forward in time would actually mean falling towards the center if we were stationary in space. The ground is constantly accelerating us upwards. Light does not get accelerated that way, so it follows the curvature.
If you want to get really deep into the reflection topic: https://youtu.be/rYLzxcU6ROM
Well that's like, your point of reference, man
