There are two stories, both of great consequence, that Lee Billings tells in his new book, the excellently titled Five Billion Years of Solitude. The first concerns the recent discovery of planets circling distant stars, and our ongoing struggle to find life on their surfaces. Billings takes us to the cutting edge of this field, letting us share intimate moments with its most accomplished scientists. We get a deep sense for the cosmic wonder of their work, and the steep challenges they face in carrying it out.
If the book had no higher ambition than to be a richly reported, lyrical meditation on the frontier of exoplanetology, it wouldn’t disappoint. But Billings goes further, putting that field's discoveries into context. He does this by telling a second story, one that hits a bit closer to home: the story of our planet, the only place known to support life. Billings takes us from Earth’s violent formation, to the rise of life here, and onward, to the events that will someday make this world uninhabitable. This deep history shows us the incomparable splendor of planet earth, but it also illuminates its limits—and reveals the high stakes that attend our search for new earths.
Last week, I interviewed Billings by email about Five Billion Years of Solitude. What follows is an edited transcript of our exchange.
Tell me a little bit about how you first got interested in this subject. Were you always into astronomy, or fascinated by the possibility of finding extraterrestrial life, or did you find your way to this project some other way?
The short answer is that I’ve been interested in these topics for as long as I can remember. The longer answer is that around the turn of the millennium I started regularly seeing news stories about how astronomers were discovering ever-larger numbers of exoplanets, and how sometime in the next decade or so NASA and other space agencies would build and launch space telescopes designed for the explicit purpose of seeking out Earth-like worlds and the life they might harbor. That just seemed like such a cool, wild idea. It was always in the back of my mind as a good story to research and pursue when I was just starting out in science journalism.
The real turning point for me occurred in 2007, when a prescient astrophysicist friend of mine gave me a simple exercise: Take the year-to-year records for the smallest exoplanet, graph them over time, and draw a trend line through the data. When I did that I was amazed by what I saw. All the early exoplanets were big bloated balls of gas rather like Jupiter, but later discoveries were often more diminutive, more Earth-like worlds. The trend of the data suggested that by mid-2011, planet-hunters would have found at least one Earth-sized planet. Astronomers were already talking about the Kepler mission, and how it could find potentially habitable Earth-like planets after it launched in 2009. A handful of other instruments and telescopes were also in contention, so there was really a race going on to find the first small, rocky worlds. I thought that was pretty exciting and dramatic, so I started writing about it where and when I could.
In the meantime, NASA’s push for big life-finding space telescopes was already running into very serious trouble and major delays, and the prognosis would only become more grim as the years went on. As I delved deeper into the topic, I was struck by the notion that, soon, potentially habitable planets would be piling up by the dozens, but without major shifts in policy and funding we would have extremely limited abilities to determine whether or not any of those worlds were actually habitable or inhabited. That just didn’t make any sense to me, and I started wondering why nobody was really raising a fuss about it. It troubled me greatly that, outside of a handful of astronomers, no one really seemed to care that an opportunity to discover life beyond the solar system was slipping away. I wanted to figure out how the state of play had changed so dramatically in such a relatively short time, and, if I could, do my own small part to shift things back on course. That’s basically how the book came to be.
This book is a kind of snapshot of where we are, technologically and culturally, in our quest to find out whether there is life elsewhere in the universe. While I was reading it, I couldn’t help but wonder where you think this question stacks up against the other big, primary intellectual inquiries. Is this ultimate question right now? If not, what is?
The book’s central question isn’t really whether or not life exists elsewhere in the universe. If that was the central question, I would’ve included much more detail about research into the origins of life, and about the prospects for extraterrestrial life within our own solar system. I’m inclined to believe that life is an emergent cosmic phenomenon, something as inevitable in our universe as the formation of stars and galaxies, and that perspective certainly informs the book. So piling on pages and pages of detail and debate about how life might emerge on a planet seemed to me a case of missing the forest for the trees. The book is less about life’s origins and more about what life does after it gets started on a planet like Earth.
Because, if you think about it, if life is so common throughout the universe, you have to wonder why everything we see out there looks so dead. I’d guess it’s because most life is actually quite hard to detect over cosmic distances, because it doesn’t end up progressing to sentience and technology. It doesn’t end up building starships and interstellar beacons to explore and communicate with the rest of the galaxy, at least not in any obvious way we can easily see. Put another way, right now it looks like most life out there doesn’t do the things that we like to tell ourselves we’ll eventually do. Short of joining in the search myself or just writing extremely speculative science fiction, it seems the only way to get at why that might be is to take a long, hard look at our current situation on Earth in light of recent discoveries about other planetary systems and our own world’s deep past.
So the book’s real central question is what the future holds for life—particularly intelligent life—on this small world orbiting a lonely star. We already know that someday our Sun will cease to shine, bringing life on Earth and in the solar system to an end. Can we—will we—avoid this dismal fate forecast for us by stellar astrophysics? No one really knows that answer yet. And perhaps that’s not an “ultimate” question in the big universal scheme of things. But perhaps it is. I certainly think that, either way, it’s of immense importance to everyone in the here and now on Earth. The book’s core theme, if it can be said to have one, is that the question of life’s future on (or off) this planet is not only worth asking, but also more urgent than commonly believed.