“What is the speed minimum of light? How slow can it move?”
Well, c is the speed of light in a vacuum, it always moves at that speed in a vacuum, it never slows down. It can be slowed down when moving through a medium, but I think the individual waves or photons are still moving at c, it is just that they are being absorbed and re-emitted by the matter they move through, so that causes the aggregate speed to drop.
So light can slow as it passes through a medium but then re-accelerate once it clears the medium? At a photon level, what energy causes the re-acceleration?
I am not a physicist and not trying to be coy. But I have questioned some of the science as it pertains to some “known” constants when applied to the whole universe. The age and size of our universe is based on the observable light and the red shift in that light (among other things). If lights path can be altered by gravitational waves (black holes) and magnetic waves and even slowed as it passes through gaseous portions of space, how is the observable light measured accurately? Or is it’s trajectory and speed deviation irrelevant/inconsequential?