Critical Election? Critical Century!

Sir Martin Rees, an eminent Cambridge University astrophysicist, has an article on science in the next century in the current issue of The New York Review of Books, in which he covers space, nuclear weapons, climate change, green energy, resources and population, epidemics, weaponry of mass destruction, and ultimately the social responsibilities of scientists. As The New York Review may not be the usual destination for IEEE Spectrum readers, Rees's arresting final remarks may be worth quoting at length. Here they are:

''. . . This century may be a defining moment. It's the first in our planet's history where one species''ours''has the earth's future in its hands.

Suppose some aliens had been watching our planet''a "pale blue dot" in a vast cosmos''for its entire history, what would they have seen? Over nearly all that immense time, 4.5 billion years, the earth's appearance would have altered very gradually. The continents drifted; the ice cover waxed and waned; successive species emerged, evolved, and became extinct. But in just a tiny sliver of the earth's history''the last one millionth part, a few thousand years''the patterns of vegetation altered much faster than before. This signaled the start of agriculture. The changes accelerated as human populations rose.

But then there were other changes, even more abrupt. Within fifty years''little more than one hundredth of a millionth of the earth's age''the carbon dioxide in the atmosphere began to increase anomalously fast. The planet became an intense emitter of radio waves (i.e., the total output from all TV, cell phone, and radar transmissions). And something else unprecedented happened: small projectiles lifted from the planet's surface and escaped the biosphere completely. Some were propelled into orbits around the earth; some journeyed to the moon and planets.

If they understood astrophysics, the aliens could confidently predict that the biosphere would face doom in a few billion years when the sun flares up and dies. But could they have predicted this unprecedented spike less than half-way through the earth's life''these human-induced alterations occupying, overall, less than a millionth of the elapsed lifetime and seemingly occurring with runaway speed? If they continued to keep watch, what might these hypothetical aliens witness in the next hundred years? Will a final spasm be followed by silence? Or will the planet itself stabilize? And will some of the objects launched from the earth spawn new oases of life elsewhere?

The answers will depend on us, collectively. . . ."


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