Protecting the planet
In the unlikely event that astronomers discovered a civilization-ending asteroid or comet destined to impact Earth in a month, we wouldn't have enough time to stop it. But with more warning, we should be able to deflect a doomsday rock.
The most commonly suggested strategy so far is a nuclear explosion to blast the object aside. However, if the asteroid was a loosely bound collection of rubble instead of a dense solid mass, it might absorb the explosion's energy.
Other proposed schemes include attaching a nuclear-powered or solar-powered rocket to steer the asteroid out of the way, or setting up a scooping mechanism to repeatedly fling bits of rock away from the asteroid, thereby nudging it off course. Some researchers think that painting an asteroid white would cause energy from sunlight to push the rock out of the way.
"Who knows whether, when a comet shall approach this globe to destroy it, ... men will not tear rocks from their foundations by means of steam, and hurl mountains, as giants are said to have done, against the flaming mass?"
- Lord Byron, 1821
Topic: Earth Science
Keywords: Meteorites, Astrophysics, Asteroids--Collisions with Earth--Prevention, Astrogeology, Collisions (Astrophysics), Natural disasters