...and a 30 percent chance of sky-falling

Sorry about the giant graphic, but I like the pretty colors.

This is the Torino scale, a Richter scale for asteroid strikes. Unlike the old Richter scale used to do -- measuring the magnitude of an earthquake -- Torino measures the likelihood of a hit, and how bad that hit's going to be.

For a while, when some backyard astronomer with a high-powered 'scope would see something that looked like it was on the way to a "rendezvous," he'd send a telegram to the Harvard-Smithsonian Center for Astrophysics (this is before email), and they'd send out a notice to the world astronomy community saying, basically, keep watching the skies. Then a lot of people would do some math and figure out if the thing was going to hit us or not.

But by the time they'd done the equations that said, nope, we're good for another few thousand years, the press would have gotten wind of it, and the civilians would be panicking and demanding that we send Bruce Willis up there to get the job done.

Over the past couple decades a bunch of organizations have sprung up (and gotten funded) to look for asteroids that pose a potential threat -- NASA's Near-Earth Object program, for example. But there's a lot of sky up there, and a lot of rocks.

My favorite part of the scale: Torino 7. "International contingency planning is warranted." Yeah...I think so, too.