photon

My first ancestor was born from the fusion of two protons at the center of a star millions of years away from the planet you call home. It took two hundred thousand years for my progenitors to reach the surface of that star, each one making it no longer than a few centimeters—fractions of nanoseconds—before being absorbed. Collectively, we were destroyed and re-emitted ten septillion times, making tiny steps in random directions before finally finding the surface. And now, I am here, having just left the surface of my star, in the barred spiral galaxy you call Andromeda. It is your closest galaxy, but at the same time the farthest object you can see without a telescope.

Where do I go? I could find comfort in the warmth of another star's surface, or a cloud of hot gas in the interstellar medium. I could land on a planet, an asteroid, or a comet. I could visit one of the clusters near my own galaxy, or perhaps to some foreign world in our neighbor Triangulum. Or I could be more daring and pass the thousands of galaxies that compose the Virgo Supercluster, moving through vast swaths of space and time and even past the edge of the observable universe until I have run to my hearts content. But this does not interest me. I visit the Milky Way—I deliver myself to you.

It is a long and treacherous journey to make it from the surface of my star to the receptors in your eye, but it is a noble one. Your ancestors wouldn't have been able to navigate the seas of Earth without photons like me to light the way. You could never witness the beauty of a starry night sky. You could not even make out the faces of your loved ones if it were not for my kind. You would live your entire life shrouded in darkness. And so I am steadfast in my travels, for a quantum of radiation knows no fear. I cannot be hurt; I can only be absorbed. I am indivisible.

Not to mention, in some sense this grand trek isn't long at all. To you it takes me two and a half million years to get from my star to your planet. But you see, the faster an object goes, the faster it experiences time. I travel at the speed limit of this universe, so I experience my birth, death, and everything in between, all in one instant. In the language of physicists, I am null. I pass no time, and am never at rest.

And so I zip between our galaxies, dodging particles of dust and gas, curving minutely by the influences of gravity. The ever accelerating expansion of space stretches the crests of my waves apart, sapping away my precious energy. Thankfully, it isn't lonely. Other photons just like myself join me in unfathomable numbers, making empty space hum with the energy of our countless bodies. A few of us will be scattered by bits of matter, redirecting us to some other alien corner of this universe. Those worlds deserve light, too.

This entire journey occurs in one instant that lasts two point five million years. But for what? To slam face-first into a concrete sidewalk? To be caught in your hair as you look away? To be destroyed on the skin of your eyelids?

Lucky for both of us, none of this has happened yet. In your frame of reference, I am still meandering on my long trek. So on your next clear night, cast your gaze about halfway between the north pole and the position your Sun takes in the springtime. Look for a faint, oblong cloud, the size of a dime at arm's length. Watch carefully, and don't blink. You just might catch me.