I recently read about this new theory, that the speed of light was much greater in the past and is slower now. All speculation until proven somehow.
What puzzles me is how light photons can travel billions of light years without fizzling out. We can see galaxies in the form they were billions of years ago, if their light has taken that long to reach us. How can light keep going in space for billions of years, with a small amount of energy within each photon? A combination of wave, particle,... and magic?
Quite the question huh?
It’s because of the time dilation effect—photons don’t experience time, so they can’t change, or fizzle, or anything while in transit. See my #14.
Good question - to me anyway.
Light does not, according to our current understanding, expend energy to travel (although there are theories of ‘tired light’, too). Being massless, photons travel at the speed of light (in a vacuum). And relativity says that that is true regardless of the speed of the observer.