The universe is mostly darkness. There is very little light. Yet there are 100 billion galaxies in the universe. To picture a galaxy — well, I hope you’ve had the opportunity to look into the centre of our own, the Milky Way. When I was a kid, I saw this routinely at night, I took it for granted: the concentration of stars that formed a band of white in the black sky that arched over the tree tops and the barn roof.
It would be there at night especially when there was no moon, and sometimes I lay on the ground and stared into it for so long that I got to see more and more stars inside it, more detail, and then it was disorienting to bring my attention back to earth, to stand up and hear my shoes crunch the gravel and see the dim lamp light in the windows of the farm house.
That dense band of stars is always there, we just can’t see it during the day when the light from our own star (the Sun) brightens the sky. And if we live in Toronto, or near Toronto, or any other large city, we can’t really see the Milky Way anymore even at night. We see only a few stars. Not enough to dazzle us, they don’t dominate our sky. And most human beings alive today live in cities, and this is how they experience the night sky. But for most of human history, people have lived without electricity in small villages or campsites, and they spent their nights under a full canopy of stars with a view into the centre of our galaxy.
This galaxy of ours is a disc-shaped cluster of approximately 100 billion stars. The Sun that we orbit is just one of those 100 billion. It’s located — we are located — near the outer edge of the galactic disc, far from the centre. We’re 25,000 light years from the centre. Is it hard for you to understand just how far that is? It’s very hard for me. I was interested in physics when I was in high school, and I got very good grades in it, but still never felt like I understood what the hell was going on. 25,000… light… years… from the centre of our galaxy. A year. A year is the time it takes our planet to travel a full circle around our star. (I like to call it “our star” sometimes, to remind myself that that’s what the Sun really is, a star like all the other ones that look so small and multitudinous in the night sky.) You might imagine that the Earth is travelling slowly, or you might imagine that it’s moving quickly, speeding along in outer space, covering that immense distance around our star the Sun in just a year. I’ve been on this planet for 39 trips around the Sun. Pretty soon, the Earth will cross that precise spot in its orbit where it was when I was born, and I’ll be in that location for the 40th time. Actually for the 41st time — the first time was the day I was born, when I was officially aged 0. (And I was actually alive before that, but I was inside my mother, which doesn’t get counted as my “age”, at least in my culture. And of course, the molecules inside me have been in orbit much longer.) The Earth itself will be crossing that location in space (what I call my birthday) for approximately the 4 thousand six hundred millionth time. That is, for the 4,600,000,000th time.
Anyway, that is what we mean by “a year” — the time it takes for this planet to complete a full circle around that star. Now let’s try to think about the speed of light. It’s very, very fast. I’m in Toronto right now. Imagine that you’re in Australia. And somehow we’ve set up a network of mirrors that will reflect a ray of light all the way from — where would you like to be in Australia? Let’s say Melbourne, from Melbourne to Toronto. You point a flashlight at the first mirror and turn on the light. I’d see the light in Toronto instantly. I mean, of course it’s not really “instant”, but the delay would be imperceptible. That’s how fast light travels. For you to travel from Melbourne to Toronto, you’d have to get onto a plane and fly for about 23 hours, it would take almost a full day and it would take the burning of heavy amounts of fossil fuels made from ancient forests. If you could travel at the speed of light, you’d get to Toronto in less than a second. Faster than I can say “Melbourne”. You could leave when I said “Mel” and you’d be here by the time I say, “bourne”.
So imagine you can travel through space at the speed of light. And you take off right now en route to the centre of our galaxy. I pick up my cup of coffee, and you’ve already passed the moon — one second. A little girl is crying in the cafe where I’m sitting, and I look up and watch the mother take the girl outside and bounce her up and down, and then I notice a pretty woman across the street talking on her cellphone, and then I remember what I was writing, and by this time, you’ve passed the planet Mars. I finish my coffee, go home, do some laundry, prepare notes for my class tomorrow, and you pass the planet Saturn. I fry a pork cutlet and make a salad for my dinner, watch an episode of Corner Gas, go to bed and sleep for 8 hours, and you’ve left the solar system far behind. Everything that you can see looks to you like a faraway star. You’re still travelling as fast as when I said “Melbourne”. I get up the next morning, shower, check the weather, decide what to wear, read the paper while eating my cereal. You speed onward through space at the speed of light. Days go by. I get my new shoes waterproofed, have an argument with my girlfriend, apply for a loan, wait and worry if I’m going to get the loan. I read and mark 115 students’ journals, the leaves turn colours and fall off the trees, I drive to Kingston one day and listen to Keith Jarrett, winter arrives and it snows… and you’re still speeding that fast through outer space. I drive with my dog all the way to Halifax for Christmas, I do a jigsaw puzzle with my mother and my sister, walk on the beach, go to the pub with my dad, drive back to Toronto having to watch out for ice and blowing snow on the highway, and I stop in a remote service station in New Brunswick when it’s dark and look up and I can see the Milky Way. My dog sniffs at the snow by the side of the road, he doesn’t look up at the sky he just looks up at me. With every sniff of my dog, you’ve gone another vast distance, you’re still speeding unbelievably fast through outer space. Through the winter I work on a novel in between my teaching duties, day after day I go to this cafe in the morning; I ride the streetcar, I visit my girlfriend and she visits me; we break up, and we get back together again; and break up again and feel helpless. It’s not only light speed that feels impossible. I search for jobs to come after my contract expires, the weather gets warmer, the snow melts, I get out my t-shirts and shorts and wonder if I need to go shopping for new ones, I should probably replace my sandals. There are days of sweltering heat and buzzing cicadas, when time seems to be going nowhere. And finally a whole year has passed since you left. During all this time, you’ve been travelling at an impossible and silent speed through outer space, going further than the distance between Toronto and Melbourne in every one of those fleeting instants when I took a sip of my coffee, or turned the page of a student’s journal, or listened as one quiet note changed to another in Keith Jarrett’s Koln Concert. The distance that you’ve just travelled, during that whole year of my life (and yours), is one light year. That was one light year.
After all that, you’ve yet to make it to the nearest star beyond our solar system. You’re one light year from the Sun, which is grand. But you’re still three light years from the nearest star.
On the galactic scale, you’ve hardly gone anywhere. If we looked down at our galaxy of stars from above — say, at a map of our galaxy — you’ve hardly moved. You’ve gone 1/25,000th of the distance from our solar system to the centre of the Milky Way. You need to keep travelling at this astonishing speed of light for another 24,999 years before you will get to the centre of that band of light that I used to see above my barn roof. And what are the chances that on this long journey you’ll ever get to see another planet? A planet with running water? What colours will you see? It’s possible that for the entire 25,000 years you’ll never see the colour blue, nor green, not once. And we do know for sure that most of what you’ll see is, nothing. Nothing but constellations of stars that change in pattern, but never seem to get any closer.
Twenty-five thousand years is a long time, for humans. For example, 25,000 years ago there was no English language, nor Chinese; there were no gardens, nowhere on Earth; no agriculture. There was no such thing as a chicken. You’d search in vain for a grapefruit, and the homo sapiens species had barely just arrived on the huge land mass that we call the Americas. An ice age receded, there were the first plantings of corn, wheat, rice, the development of towns, the rise of the first kings, emperors; the building of pyramids and Great Walls and the live burials of countless female concubines alongside ridiculous numbers of terracotta warriors (oh civilization!); so many plagues, many wars and whippings of slaves, many deaths, murders, many loves, many childbirths and mothers holding and carrying their children for a few fleeting years til they grew older. The light from a star that you might see tonight in the centre of the Milky Way, that light that you see now, left that star 25,000 years ago, when the only light on Earth at night came from the small campfires of a human species still tiny in number, a species that was painting pictures of other animals on the walls of caves.
Do you think it’s a long time since your parents were born? A long time since poor Europeans built ships out of wood and wealthier ones sailed those ships across vast oceans? A long time since the Romans were building roads across Europe and everyone was speaking Latin and executing thousands of criminals on crosses including one guy who counted more than all the others and in whose memory we started counting our years such that it’s now past the two-thousandth? Two thousand years sounds like a long time, but in that time, at the speed of light, you’d still have 23,000 more to go before you get to the centre of our galaxy the Milky Way. A lot of people – not to mention dogs, whales, cicadas and willow trees – have lived, (maybe) loved, withered and died in that time.
And when you finally get to the centre of our galaxy: first of all, congratulations. That’s a remarkable thing, to traverse a galaxy (well, traverse about 40% of it – you’ve gone half way through it, not from end to end). But this galaxy of ours is just one out of 100 billion. That bears repeating. There are an estimated 100 billion galaxies in the universe. They come in different sizes. Some contain tens of billions of stars; others contain hundreds of billions. The cosmologist Carl Sagan used to get (gently) teased for how often he repeated the phrase “billions and billions of stars”. But really, what else can you say? Words should fail us when we’re faced with this enormity. There are at least 100 billion galaxies in the universe. Think about what that means. We’ve just tried to imagine your 25,000 year trip to the centre of our galaxy. On the scale of our universe, that trip (at the impossible speed of light for the duration of the rise and fall of whole languages and empires) has been miniscule.
And that universe continues to expand; everything is getting further away from us, further than it already is. Sometimes it feels like a long time ago that I was a kid looking at the stars above the elm trees and the barn roof at night, and the truth is, not only is that time growing more distant, but so are the stars themselves. But I’m not capable of noticing the changes in the stars, so even as time passes and I grow older and the farm is now gone, some things seem to stay the same. I don’t get to see them as often as I used to. But I know they are still the same.