Earth Exceptionalism

Earth Exceptionalism

Maybe life really is one in a hundred billion. If so, that might be good news for Earth.

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The source: “Where Are They?” by Nick Bostrom, in Technology Review, May–June ­2008.

Philosopher Nick Bostrom has surprising aspirations for the Phoenix spacecraft, which landed in the arctic zone of Mars on May 25. The director of the Future of Hu­man­ity Institute at Oxford University wants the probe to turn up nothing—sterility, dead rocks, lifeless sands.

Such an outcome would be a good omen for humanity, Bostrom writes. It would provide new evidence that the emergence of life is extremely improbable. It would suggest that billions upon billions of rolls of the dice have produced a score of only one. Heretofore, the notion that 100 billion galaxies containing possibly 100 billion stars each would have only once gener­ated the spark of life seemed almost preposterous. Yet after nearly half a century of searches for ­extra-
ter­restrial intelligence with increas­ingly powerful telescopes and data mining techniques, the night sky has yielded no messages, no aliens, and no spacecraft.

The likely explanation for this, Bostrom writes, is that the path to ­life ­forms capable of colonizing space leads through a “Great Filter,” a term he borrowed from George Mason University economist Robin Hanson. This filter consists of one or more steps that must be negotiated against odds so great as to make a particular process essen­tially ­impos­sible—­except once. If the filter is in the human past, maybe it was traversed 3.8 billion years ago, when life first shows up in the fossil record. Or maybe it happened after single-celled organisms became more complex eukaryotes 1.8 billion years later. That’s Bostrom’s opti­mistic scenario.

But what if the Great Filter is ahead of us? This would mean, according to Bostrom, that some horrific probability lies in our ­fu­ture—­nuclear destruction, climate catastrophe, genetically engineered super­bugs, or high-energy physics experiments run amok. If other ad­vanced civilizations were born but failed to pass through the filter, could our earthly civilization be any ­different?

If traces of some creature are found on Mars, it could mean that the emergence of life is not so rare. If it could happen twice in a single small solar system, it’s probably occurred in galaxy after galaxy. It could mean that all the civilizations created by the life forms that evolved over time were somehow destroyed before they could colonize or communicate with others. It could mean the Great Filter is in Earth’s ­future.

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