Nothing grabs media attention like a close visit by an asteroid or comet. At Slooh, the online observatory, hundreds of thousands tune in for such live events. Judging from their comments, some are motivated by paranoia: They think that the government will lie to them if a genuine threat from space materializes. Since Slooh is independent, they visit us to see the intruder for themselves. Armageddon never loses its allure.
On February 15, a mere four months ago, we had a double whammy. The nearest asteroid in many years whizzed past Earth some 20 times closer to us than the Moon. That same day, the Siberian meteor exploded in the air, its sonic boom blowing out windows and injuring a thousand people. And in case you were wondering, the answer is yes: An unusually large number of near-Earth objects zoomed through our neighborhood this past year – mostly due to better detection methods. Last year, NASA boosted its annual budget for hunting such interlopers from $6 million to $20 million. None of this has done anything to assuage Doomsday fears.
In reality, you can expect major damage from an incoming meteor once every few centuries, and destruction great enough to obliterate half the animal species on the planet perhaps every hundred million years. Through all of that, Earth lives on.
A half-century ago, everyone feared that we humans would be the architects of our own destruction. The novel On The Beach by Neville Shute and its subsequent movie graphically depicted the end of Homo sapiens due to worldwide radiation following a nuclear war. Soon after, Carl Sagan popularized the idea that such a war would produce a devastating Global Winter.
But despite tens of thousands of nuclear missiles remaining in the world’s arsenals, and such weapons now in the hands of several unstable governments, the public – oddly enough – does not currently seem to worry about destruction via nuclear weapons. Perhaps that’s because, as things now stand, if and when such devices are used again, it will probably happen in a limited, regional, foreign conflagration. Again, no end of the world.
People here in the mid-Hudson Valley have even less to fear. If terrorists ever succeed in the ultimate crime of detonating an atomic bomb in Manhattan, the biological effects in our region would be negligible unless that day’s weather has a precise south wind, which is rather rare. But let’s not even contemplate such a thing.
So what will end life on Earth? Not any flipping of the poles. Not global warming. Not changes in the sea level. Not any pandemic. In all probability, it will simply be the Sun.
Life has existed here for about four billion years. It would be nice if we were only halfway through our tenure and had another four billion to look forward to. It ain’t gonna happen. Our understanding of stellar evolution and the Sun’s proton-proton energy cycle is quite solid. We look around us in space and see other Sun-type spectral class G stars, and it’s very clear what will unfold not so far in the future.
The Sun is continually getting brighter and hotter. It’s ten percent more luminous every billion years. Our planet has been able to tolerate the previous increases in the solar flux. But we’ve reached our limit. In just 1.1 billion years, all natural compensation mechanisms will have been exhausted. Gaia, the intelligence underlying Earth’s biosphere, will run out of tricks. The oceans will evaporate. Temperatures worldwide will stabilize at 740 degrees Fahrenheit: hotter than an oven. A thick overcast will enshroud us, like Venus. Game over.
But that’s a billion, with a B – a thousand million years: plenty of time left for all the mischief we care to make, and all the adventures we care to have. More than time enough to learn to be gentle with our planet – which we will surely learn. Won’t we?