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.

Life–the unquantifiable and ill-defined thing life–takes perfectly ordinary atoms & molecules and gives them a motive force, like throwing a stick into a river. Suddenly, it zips. And here’s the weird part: I cannot take into my body any molecules that have not been transformed by the force of life. Unliving molecules are useless–actually harmful–to my body. Yet the molecules in question need not be alive at the time when I ingest them, only that they once were, as if they earned some kind of degree. Trees can suck from the earth, and lichens from rock, but either of these would poison me.

The answer to this oddness is, of course, that not just any old molecules will do. My body needs very specific chemical forms of molecules formed by life. By taking vitamins, we have finally found a way to fake our bodies out, thinking it has found those life-transformed molecules when it really hasn’t. But one cannot live on vitamins alone.

And when I die, my molecules will be on the loose again, ready to be snatched up by other lives.