"Disaster." The term invokes hurricanes, tornadoes, earthquakes, exploding gas lines, chemical spills. And yet it literally means "bad star" - a star that augers misfortune.
Now, astrologers make plenty of money telling folks how the stars influence their fortunes. There is not much in the way of scientific accuracy to this field: a 1985 study found astrologers unable to correctly match personality profiles with astrological charts. (In other words, your future really doesn't depend on whether Mars was or was not in, say, Ophiuchus, when you were born.)
But there really are bad "stars" out there - points of light in the night sky that have the potential to spell doom for life on Earth. The baddest are Earth-crossing asteroids: chunks of rock that are orbiting the Sun at tens of thousands of miles per hour, on paths that cross the Earth's own orbit around the Sun.
What makes asteroids "stars"? They reflect sunlight, appearing like little stars on images that telescopes take. Their true nature is revealed when they move against a backdrop of real stars (watch this image sequence for a dramatic example).
Those asteroids that span a kilometer or so can pack upwards of a trillion tons of rock. And if that much rock were to slam into Earth's atmosphere at supersonic speeds, it would be a disaster to dwarf any that has afflicted the human race.
We know how to find most, if not all, of the Earth-crossing asteroids that plague our solar system: build a globe-spanning network of large, fast telescopes with robotic "brains" and program them to photograph the entire night sky in search of moving "stars." Astronomers already operate some telescopes in this mode, but they don't yet have enough of them up and running to guarantee 24/7 coverage of the entire sky.
A bigger question is what to do once you find an asteroid that seems to have it out for us. First of all, astronomers need to triple-check their calculations to ensure that a collision is certain. Five years ago, the asteroid Apophis ("The Destroyer") was given a better than 1-in-40 chance of striking Earth in the year 2029. Now they are telling us that it'll come no closer than 29,000 kilometers to Earth's surface on Friday, April 13th of that year. That's pretty close - just over twice the Earth's diameter! - but it won't be a disaster.
What if the asteroid were certain to hit us in 2029? According to Apollo 9 astronaut Russell Schweickart, humanity is capable of building and launching spacecraft that could change an asteroid's orbit enough to prevent a collision with Earth. Schweickart's B612 Foundation is lobbying for a mission to put the idea to the test - before we find a space rock that's got our name on it. (And that may not take long; apparently it remains an open question whether or not Apophis's near-miss in 2029 will put it on course for a collision with Earth in 2036.)
Copyright 2009 Joshua Roth. All rights reserved.
