Smile!

Smile! The world doesn’t end without you.

One in two. That’s the clean chance Sir Martin Rees, the UK’s Astronomer Royal, gives our civilization to survive the 21st century. This estimate–humanity’s high-stakes, slow-motion coin toss, if correct–is made early on in Rees’ popular-science guide to the apocalypse, Our Final Hour.

Rees is no dour doomsday quack, but neither is the Cambridge professor inclined to candy coat our predicament. Although his stated purpose is to alert us to the ways in which we can still nudge the odds in our favor, the question hovering over this surprisingly sprightly little volume remains: Do we feel lucky?

Even if we do, our species may have used up all its planetary luck. Surviving 40 years of nuclear superpower stand-off was itself a remarkable feat–and one that looks easy in retrospect. After a brief, drunken burst of post-Cold War optimism, new threats have been creeping in like spiders from all directions, and Rees is coldly confident that these will multiply and fatten in the coming years, in some cases exponentially. These gathering dangers are so critical and so near to us that "it may not be overstatement to assert that the most crucial location in space and time (apart from the big bang itself) could be here and now." Who says your life is boring?

While Rees’ metaphorical coin toss haunts every page, the book is more than just scary. Twenty-first-century dragons often given alarmist coverage in the media look smaller in their scientific and historical contexts, while the clarity of Rees’ prose is calming. And treatments of obscure threats that skirt the line between mainstream futurism and whimsical speculation are so gripping, you almost forget to be afraid. But what really separates Our Final Hour from other catalogs of the same genre is the cosmologist’s Hubble-like long-view and his bubbling excitement over the as-yet unlocked mysteries of the universe. Rees is a man who wants our race to colonize the galaxy and find other dimensions. And he’s confident science will take us there.

But only if we get out of here alive, and Sir Martin Rees is still not the guy you want to tell you a bedtime story. In 2002, as part of Wired magazine’s series of "long bets," he staked one thousand dollars that, as he says in the book, "by the year 2020, an instance of bioerror or bioterror will have killed a million people." Among current threats, Rees views the open can of biotech as by far the most urgent and intractable. The downward proliferation of microbiology technology will soon put the means to create and mutate viruses in the hands of virtually anyone who wants it, and the threat of a killer virus or bacteria’s escaping non-terrorist-related research only grows with the accelerating advance of science.

Rees also examines the likelihood and consequences of visits from old friends like killer asteroids, H-bombs, earthquakes and climate change. More fascinating, however, are the chapters on threats once reserved for sci-fi: life-destroying, self-replicating nanotechnologies and particle accelerators that could rupture the very fabric of the universe.

Although the chance of these experimental catastrophes’ coming to pass is small, Rees argues that their remote probabilities should be balanced against their monumental consequences, and that the precautionary principle should guide all research as we barrel into this brave new century. He likewise applies this principle to the emission of carbon gasses–despite the uncertainties of current climate predictions–and argues for arms control and the intensification of efforts to protect Russia’s rusting nuclear arsenal.

In the end–pun intended–humanity’s survival is, for the author, about more than just ourselves. If our civilization is one of millions in a universe teeming with intelligent life, then Rees considers our extinguishment insignificant. But if we are unique and alone, as he suspects, the result of unimaginably complex factors unlikely to ever be duplicated, then our continued existence and progress takes on a cosmic meaning. In such a lonely universe, we should do everything possible to counter the army of threats now arrayed against us, aware that fate, as always, is at least partly in our hands.