The Big Picture: Life In The Troposphere

Hike to a high place at dusk on a clear evening.

Turn yourself around. Take in the expanse of land and sky as stars begin to appear. Recognize how little of the planet you can see, because its curvature keeps the rest for itself. Here are two thought experiments to occupy you as the last colors of the day slip into the Sun’s shadow (you brought a flashlight, right?).

Wherever you live — in a small town, an urban jungle, or a vast stretch of farmland — picture two points eight miles, or thirteen kilometers, apart. It’s not very far. A fast walker can make the trip in an hour and a half.

In Los Angeles it’s the distance from Disney Hall to the Hollywood sign. In Las Vegas it’s just longer than the Strip, from the ‘Welcome to Las Vegas’ sign to downtown. In Dallas, Dealey Plaza to the Botanical Garden. And in New York City it could lead from Harlem to the Battery, straight down 5th Ave.

Open Google Earth (in your mind. This is a thought experiment. Work with me). Draw a line between those two points, then start to zoom out. Long before you can see your entire state (yes, even Rhode Island), your line has become a dot. Keep going. By the time you can see the whole country (even in Lithuania) you can’t detect it. Keep going until you can see the sphere of the planet.

The Troposphere contains Earth’s atmosphere; all the breathable air, all the weather. Thirteen kilometers is its average height. At just eight kilometers you can’t breathe without an oxygen tank. As you look at the world, rotating slowly on your screen, and you think about the length of that tiny line, raise it vertically like a telephone pole.

That’s all we get. That paper-thin membrane is the air that has supported the only life that’s ever existed in the known universe. As you look straight up from your hilltop, the sky seems to go on forever. It doesn’t. This is why a few short centuries of industry have changed the cycles of heat and humidity across the planet to the point that its ability to sustain our fragile lives is now in question.

By now, the sky above you is full of stars. Every star you can see lives inside our own single galaxy, the Milky Way. Our star is out near the edge of that spinning spiral. If you’re far enough away from a city, you won’t be able to miss the rest of the Milky Way, the Great Rift, which can be bright enough to see by, even if you forgot your flashlight. Most of the stars in our galaxy are in there; hundreds of billions of them.

If you find yourself in Los Angeles, go to the Griffith Observatory and head downstairs to the Gunther Depths of Space exhibit gallery. It’s free. Parking isn’t, so you may want to get a ride. In this gallery, taking up an entire wall, you’ll find an enormous photo of the night sky called The Big Picture. It’s full of galaxies only visible with a large telescope. In rough numbers, each one of those galaxies contains as many stars as ours. Some more, some less. Start to calculate how many stars are in that picture and your head will begin to hurt. When you put enough zeros after a number it gets abstract, but think about those points of burning atoms hanging above you on the hilltop and work forward. You’ll get the idea.

Now look beside the photo and you’ll see another picture showing how The Big Picture was enlarged from only a small sliver of the visible night sky. Look at the rest of the sky that isn’t included in the photo and try to do the math. Unless you’re at sea (you’re not. You’re on a hilltop), or maybe in the American Great Plains (not known for an abundance of hilltops) the horizon is obscured by terrain. Add the hidden part of the sky to what you can already see. Do more math.

Now remember that even from your hilltop you can only see about a third of the space surrounding our planet. There’s all that other space below you on the other side of the world. Whatever math you did, whatever way you’re able to think about how many stars you could potentially see from your hilltop with enough telescopes viewing enough galaxies in enough of the sky, multiply it all by three.

Now consider that there are even more galaxies out there which are too small to see in the photo because the imagers which took The Big Picture are twenty years old now, and the Samuel Oschin Telescope, which is on land, not in orbit, was built during World War II. More math.

That’s our universe.

Practically every one of those stars has planets orbiting them. Most are just chunks of frozen rock, or they’re wrapped in toxic gasses, or both. But we’re detecting more every day with similar enough conditions to Earth that it’s possible they could support life like ours. There are billions of them. Science still hasn’t figured out how life started on Earth, and it may never. But whatever caused it, there’s no reason to think it couldn’t have also happened on any of those other goldilocks exoplanets, or on other ones down in thermal vents under oceans of ice. Or on any of their moons. There are trillions of test cases waiting for us to explore.

The evolution of human life is a miracle. It’s unique and precious and fragile. In spite of our weaknesses, which cause us to start territorial wars, or persecute each other for tribal differences, or cut each other off in traffic, we’re worth fighting to preserve. We are indeed at a decision point right now, today. Every day that we don’t buckle down and decide which hard decisions we’re willing to make and which ones we aren’t in order to preserve our habitat for future humans, our ability to explore those distant worlds diminishes. And losing the chance to do that would be a tragedy.

So look up at the stars and breathe in the fresh mountain air. Appreciate it all for what it is. Help make the choice to protect it. It’s all we have.

— Dave Coulter

11/18/2023