Asked if he was lonesome in his hut on Walden Pond, Henry Thoreau famously replied, “How could I be lonely? Don’t I live in the Milky Way?”
Thoreau doubtless would have been encouraged by this week’s discovery of a new planet orbiting the sun-like star Tau Ceti, just 12 light years away and not much more massive than our Earth, right in the Goldilocks zone: not too hot, not too cold, just right for organic chemistry to flourish. Scientists collated 6000 observations from three different telescopes to find the planet, while the Kepler spacecraft has found hundreds of others like it since its launch three years ago. Given the size of our galaxy, there are almost certainly billions more.
Life is probably widespread in our universe, astronomers 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 world anyway? It would take our fastest rockets more than a thousand years to reach Tau Ceti 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.