Five billion years ago, the sun was just an embryonic patch of drifting gas, waiting to collapse to a central core and burst forth with light. Five billion years from now, the sun, in its death throes, will expand and swallow the Earth.

In that 10 billion-year period, the entire history of the planet will play out, from its formation out of the rocks and pebbles that stuck together within the gaseous swirl, to the mad rush of continents across its watery face, to the rise of an atmosphere full of a ghastly poison called oxygen, to the evaporation of the oceans and the snuffing out of all life, to the Earth’s final disintegration in the outer layers of the red giant star that the sun will become. When the end finally arrives — and it will — the story of humans in the universe will have come and gone. Or, just maybe, the story will continue.

We as a species are perched at an inconceivably special moment in this cosmic timescale. If the age of the Earth were compressed into a human lifetime, in just the past two weeks primates came down from the trees and learned to navigate among the planets. In the past few minutes, they figured out that the stars in the sky are suns like our own. Ten seconds ago, they realized that those suns have planets around them. And within the next minute, it seems likely that they will discover the first evidence of life on those planets in the sky.

Or maybe not. Lee Billings’s contemplative new book, “Five Billion Years of Solitude,” while deftly moving back and forth between geological time and the current epoch of astronomers searching for life, has many reminders of the uncertainty as to what is out there, as well as the precariousness of the Earth, its societies and the humans living on it. The tone is set with the first words out of the mouth of Frank Drake, an astronomer who wrote down an uncannily simple equation 50 years ago that attempted to predict the number of contactable civilizations in our galaxy. Where once Drake headed attempts to find such civilizations, today he says that “things have slowed down, and we’re in bad shape in several ways.”

As the rest of the book shows, he’s not exaggerating. Radio telescopes that used to scan the skies for distant signals have been mothballed; giant space telescopes that could detect the presence of biological activity on distant planets have been canceled; even the recent hero of planet-hunting — the Kepler mission, a space telescope devoted exclusively to finding signals of Earth-like planets — has recently suffered a mechanical failure, causing it to stop its search early without the shining discovery of anything truly Earth-like. But Kepler gleaned the first hints — some of which were revealed this month — that we are on the verge of making those discoveries.

‘Five Billion Years of Solitude: The Search for Life Among the Stars’ by Lee Billings (Current. 294 pp. $27.95). (Penguin)

On top of all of that, Drake’s equation forces one to contemplate the answer to a downer of a question: How long can a civilization last before it is destroyed?

Billings weaves between our eventual destruction and our hope to avoid it in a way that makes the future and the past seem as real as the present. We are taken on a quick journey with Tom Murphy, an astronomer from San Diego, as he breezily contemplates how we might maintain our currently modest 2.3 percent annual increase in energy consumption. By 2287, we will need to have covered all of the Earth’s land with solar panels. If we then switched to nuclear power, we would have a few more centuries before “the waste heat from the vast amount of power being produced evaporated the oceans and turned Earth’s crust to a glowing slag.” On a walk around a lake in Pennsylvania, planetary scientist Jim Kasting contemplates the slowly warming sun and how it will eventually boil away the oceans. He muses that “intelligence has only now appeared at the halfway point in the Sun’s ten-billion-year lifetime, and it won’t be easy to hang around longer than another half-billion years.”

As an antidote to this gloom, the physicists and astronomers around whom Billings spins his story remain dedicated to trying to find life among the stars and, perhaps, to joining it. Their fields are intensely competitive, with egos, personalities and rivalries often having a major impact on the scientific enterprise — just as with any other human endeavor — but it is they and their colleagues who have put us on the brink of being able to know just how rare or common in the cosmos planets like ours are. Their collective goal is to try to make the next 5 billion years of the history of Earth not quite as solitary as those first 5 billion years. Drake has spent a lifetime thinking about and searching for extraterrestrial signals; Kasting ponders how you would know a habitable planet if you saw one; and the ache to find an Earth-like planet is so intense in Sara Seager, an astronomer at MIT, that you might almost feel the need to look away.

This book is sweeping in scope, from the creation of the coal belts in Pennsylvania to the moving details of a single canoe trip across the Canadian wilderness. In these juxtapositions, Billings performs a brilliant sleight of hand, in which you suddenly find yourself as emotionally connected to the seemingly abstract fate of Earth over the next few eons as you are to the tangible prospects of a husband and father struggling against early cancer. The ending is a poignant reminder that humankind may yet find a way to the stars, but people — the ones we know, the ones we love, the ones we lose — are our entire history and our full universe.

Mike Brown is a professor of planetary astronomy at the California Institute of Technology and the author of “How I Killed Pluto and Why It Had It Coming.”


The Search for Life Among the Stars

By Lee Billings

Current. 294 pp. $27.95