Asked if he was lonesome in his hut on Walden Pond, our neighbor Henry Thoreau famously replied, “How could I be lonely? Don’t I live in the Milky Way?”
Thoreau doubtless would have been encouraged by the recent discovery of Kepler-22, a planet just 600 light years from earth right in the Goldilocks zone: not too hot, not too cold, but a balmy 72 degrees on the surface, just right for organic chemistry to flourish. It’s just one of 139 potentially habitable worlds sighted since the Kepler spacecraft started looking for them a couple of years ago. And given the size of our galaxy, there are almost certainly billions of others.
Life is probably widespread in our universe, scientists now agree. Back when I was a boy, a famous experiment produced amino acids (the building blocks of proteins) by flashing an electric spark through a beaker of ammonia, methane, hydrogen and water vapor—thought to be the primitive components of earth’s atmosphere. The theory was that, long ago, a lucky lightning strike in a shallow pond produced the first protoplasm. But now we know that amino acids are everywhere: in the tails of comets and in the dust of interstellar space. Wherever conditions are right, evolution takes off.
And conditions are right all over, not just on places like Enceladus, a moon of Saturn where liquid water has been proven present in geysers. Many cosmologists agree that the cosmos appears propitiously suited to life, right down to the fundamental constants that govern gravity and allow stars and planets to form at all.
Of course, this doesn’t necessarily mean that the universe was “designed” for beings like us. But it does put a new twist on old legends like the Christmas star. Does it really matter whether a nova appeared over Bethlehem all those years ago? For me, the real wonder is that we are all born out stars, every molecule in our bodies forged in the furnaces of the heavens.
What this means is that we humans belong here. We are not just accidental tourists in this world. We have grown out time and space as naturally as grass pushes up through city sidewalks. And we are linked to nature, not only in our biology but in our minds and spirits also, which conceive space probes like Kepler and seem eternally fascinated by the big questions of where we come from and where we fit into the greater scheme.
Who cares whether astronomers find another habitable planet anyway? It would take 22 million years for our fastest rockets to reach Kepler -22, not even figuring in pit stops. But the answer is, people care. For beyond the business cycle, the election cycle, and other ephemeral headlines, human beings remain creatures hungry for news of the infinite. And for me at least, it is satisfying to know not only that we live in the Milky Way. In some important sense, the Milky Way—in all its brilliance and unfathomable extent --also lives in us.