Sometime in the late Seventies, a certain stream of photons flowed through a window in Barryville, NY. In the flow danced tiny bits of dust. I, at age four or five, stared transfixed at the beam. Did the beam create the dust or just illuminate it? I hoped the former, even though I suspect I was wrong.
Years later, I had an epiphany. According to Einstein’s theory of special relativity, time is experienced according to how we sense light. Therefore LIGHT==TIME. Excited, I sped to an astrophysicist friend and asked if my idea was accurate.
Nope! My friend informed me that light plays very little role in how physicists think about the phenomenon of time.
(This is why you always want to ask someone with expertise, folks)
The thing is that you can go the other way: since, according to Einstein, light is so plastic, physics had to proceed to more reliable ways of describing time (and time gets more complicated and much less assured as you discover more about it.)
Yet there is some relationship. LIGHT==TIME was off. But I am told that if I were to somehow teleport to a point far enough away from earth, I could see that moment captured in my memory fleeing out to distant stars. When we look into the night sky, we see the distant past. Light is a form of time travel.
I still remember that beam of light, defining the dust motes within it. Light and memory and time, all interwoven. Beams of light everywhere and always, in 1978, in 1928, in 1028, in -1028, ten thousand years before that moment, ten million years before that moment, ten hundred million years before that moment. Light may not define time, but it defines the moment.