But even in this “concertinaed” timeline — extending millions of centuries into the future, as well as into the past — this century is special. It’s the first in our planet’s history where one species — ours — has Earth’s future in its hands, and could jeopardize not only itself, but life’s immense potential.
Suppose some aliens had been watching our planet for its entire history. Over nearly all that immense time — 4.5 billion years —- Earth’s appearance would have altered very gradually. But in just a tiny sliver of its history — the last few thousand years — the patterns of vegetation altered much faster than before. This signaled the start of agriculture. The pace of change accelerated as human populations rose.
Then there were other changes, even more abrupt. Within the last 50 years — little more than one hundredth of a millionth of the Earth’s age — the carbon dioxide in the atmosphere began to rise anomalously fast. The planet became an intense emitter of radio waves (TV, cellphone and radar transmissions.) And something else unprecedented happened: small projectiles launched from the planet escaped the biosphere. 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 halfway 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 few decades? Will 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 outcome depends on political choices. But those choices can be influenced by effective and idealistic scientists, environmentalists and humanists, guided by the knowledge and technology that the 21st century will offer.
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