Space Watch III 
When Hollywood scriptwriters need someone to save Earth from an asteroid, they usually call on a demolitions expert — someone who can blow the big space rock to space dust. In reality, though, the best person to call just might be a house painter.
Astronomers have discovered about 1400 good-sized asteroids that come perilously close to Earth, and they expect to find many more over the next few years.
A collision with one of those big boulders could have devastating consequences. An asteroid just a couple of hundred feet in diameter gouged the meteor crater in Arizona, killing everything within many miles when it did so. And in fact, a similar-sized asteroid will pass close to Earth on Friday; more about that tomorrow.
So far, none of the hazardous asteroids is on a collision course. But if one is found to be heading our way, there are a few ideas for knocking it off course. They depend on the size of the asteroid and how much lead time we have to prepare for it.
One idea follows the typical Hollywood story line. A nuclear explosion could vaporize part of an asteroid’s crust, spraying enough gas to push the asteroid off course.
Another idea is to paint a large part of the asteroid white. That would change the way it absorbs solar energy and re-emits it as heat — a process that imparts a tiny thrust on the asteroid. With enough lead time, a tiny change in that thrust could push the asteroid just enough to keep us safe from a cosmic threat.
Script by Damond Benningfield, Copyright 2012