Death and destruction are not exactly foreign themes incosmology. Black holes can rip apart stars; unseen darkenergy hurtles galaxies away from one another. Somaybe it’s not surprising that Sir Martin Rees, Britain’sAstronomer Royal, sees mayhem down on Earth. Hewarns that civilization has only an even chance of mak-ing it to the end of this century. The 62-year-old Univer-sity of Cambridge astrophysicist and cosmologist feels sostrongly about his grim prognostication that last year hepublished a popular book about it called Our Final Hour.

The book (entitled Our Final Century in the U.K.)represents a distillation of his 20 years of thinkingabout cosmology, humankind and the pressures thathave put the future at risk. In addition to consideringfamiliar potential disasters such as an asteroid impact,environmental degradation, global warming, nuclearwar and unstoppable pandemics, Rees thinks scienceand technology are creating not only new opportuni-ties but also new threats. He felt compelled to writeOur Final Hour to raise awareness about both the haz-ards and the special responsibilities of scientists.

As one himself, Rees was among the first to positthat giant black holes power quasars, and his work onquasar distribution helped to refute the theory that thecosmos exists in a steady state. Rees directed Cam-bridge’s Institute of Astronomy until 1992; he thenserved for a decade as a Royal Society Research Pro-fessor before assuming the mastership of Cambridge’sTrinity College. Since 1995 Rees has also held the hon-orary title of U.K. Astronomer Royal, once an activepost based at Greenwich Observatory and first held byJohn Flamsteed and then Edmond Halley.

Astronomers are well positioned to ponder the fateof humanity, Rees insists, because they have a uniquevantage point in terms of the vast timescales of the fu-ture. “Astronomers have a special perspective to seeourselves as just a part of a process that is just beginningrather than having achieved its end,” he says. “And per-haps this gives an extra motive to be concerned aboutwhat happens here on Earth in this century.”

Innovation is changing things faster than ever be-fore, and such increasing unpredictability leaves civi-lization more vulnerable to misadventure as well as todisaster by design. Advances in biotechnology, in termsof both increasing sophistication and decreasing costs,means that weaponized germs pose a huge risk. In awager he hopes to lose, Rees has bet $1,000 that a bi-ological incident will claim one million lives by 2020.“In this increasingly interconnected world where indi-

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Doom and Gloom by 2100Unleashed viruses, environmental disaster, gray goo—astronomer Sir Martin Rees calculates thatcivilization has only a 50–50 chance of making it to the 22nd century By JULIE WAKEFIELD

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■ Knighted in 1992; became Astronomer Royal in 1995.■ Career choice in an alternative universe: music composer.■ Has bet $1,000 that a bioterror or “bioerror” incident will claim one million

lives by 2020 (see www.longbets.org/9).■ “We can’t enjoy the benefits of science without confronting the risks.”

SIR MARTIN REES: LIFE AMONG STARS

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viduals have more power than ever before at their fingertips,society should worry more about some kind of massive calami-ty, however improbable,” Rees states.

In calculating the coin-flip odds for humanity at 2100, Reesadds together those improbabilities, including those posed byself-replicating, nanometer-size robots. These nanobots mightchew through organic matter and turn the biosphere into a life-less “gray goo,” a term coined by nanotech pioneer K. EricDrexler in the 1980s. Gray goo achieved more prominence lastyear after Prince Charles expressed concern about it andMichael Crichton used it as the basis for his novel Prey.

It’s not just out-of-control technology that has Rees worried.Basic science can present a threat. In July 1999 Scientific Amer-ican ran a letter by Princeton University physicist Frank Wilczek,who pointed to “a speculative but quite respectable possibility”that the Brookhaven National Laboratory’s Relativistic HeavyIon Collider (RHIC) could produce particles called strangelets.These subatomic oddities could grow by consuming nearby or-dinary matter. Soon after, a British newspaper posited that a“big bang machine”—that is, RHIC—could destroy the planet.

The ensuing media flurry led then Brookhaven director JohnH. Marburger to pull together an outside panel of physicists,who concluded that the strangelet scenario was remote, abouta one-in-50-million chance of killing six billion people. (Anoth-er panel, convened by CERN near Geneva, drew a similar con-clusion.) In Our Final Hour, Rees noted that the chances canbe expressed differently—namely, that 120 people might diefrom the RHIC experiments. He thinks experts should debatein public the merits and risks of such work.

Some researchers were not pleased with Rees’s position. SubirSarkar, a University of Oxford cosmologist who considers Reesa true “guru” for his wide-ranging perspective and contributionsto astrophysics and cosmology, contends nonetheless that Reeswas “irresponsible in making a big deal of the negligible prob-ability” connected with the particle collisions at RHIC. Rees ac-knowledges that other doomsday scenarios rank much higher interms of a “risk calculus.” Yet he maintains that if the safety cri-teria used for nuclear reactors are applied—in terms of maximumacceptable probability of deaths multiplied by number at risk—

the probability of global catastrophe from any particle acceler-ation experiment would need to be below about one in a trillion.

Perhaps more important than his Our Final Hour argumentsis Rees’s ability to popularize technical subjects. “He is, by anyaccount, one of the clearest and most readable expositors of cur-rent science to the general public,” asserts friend and colleaguePeter Meszaros, a Pennsylvania State University astrophysicist.Rees has written six books for the lay reader (as well as severalScientific American articles).

It’s possible to tip the balance to civilization’s advantage,Rees concludes, believing that environmental and biomedical is-

sues should be higher on the political agenda. To raise the de-bate above the level of rhetoric, however, the public must be bet-ter informed. He looks to the U.S. to take a leadership role. Butso far he finds its handling of the controversies over stem cell re-search and global warming to be wanting: the U.S. “has beenrather remiss in tackling issues that are taken more seriouslyelsewhere in the world, especially environmental problems.”

If humanity loses, would it really matter to the rest of the uni-verse? Life exists thanks to a happy combination of physical con-stants. Tweak a few, and life as we know it becomes impossible.Those who ponder whether we were meant to be here or whetherour universe is part of a multiverse, consisting of universes withdifferent physical parameters, sometimes invoke the anthropicprinciple. It basically states that the universe must be able to

spawn intelligent life because we are here to observe it. “An-thropic reasoning will be irrelevant if the ‘final theory’ definesall the constants of physics uniquely, but unavoidable if it does-n’t,” Rees states. “The latter option is favored by an increasingproportion of theorists”—in other words, science may be ableto explain the numbers only with an anthropic argument.

Anthropic reasoning would seem to cast a supernatural pallover science. But Rees doubts that revelations from cosmologywill ever resolve the controversy between science and religion.For a start, he sees no qualitative change in the debate since New-ton’s time: scientific explanations remain perpetually incomplete.“If we learn anything from the pursuit of science, it is that evensomething as basic as an atom is quite difficult to understand,”Rees declares. “This alone should induce skepticism about anydogma or any claim to have achieved more than a very incom-plete and metaphorical insight into any profound aspect of ourexistence.” Or nonexistence, depending on the coin flip.

Julie Wakefield is based in Washington, D.C.

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APOCALYPSE SOON? A 2003 bioterror drill in Cambridge, Mass.

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