Drop the Big One on the Big One
Nuclear weapons may not be original, but they're a known entity and, as a result, a logical choice if you need to blast a boulder to smithereens. This supermacho approach involves slamming a nuclear warhead into an approaching asteroid. There's only one problem: A direct hit on a large object might only break it into several smaller pieces (remember "Deep Impact"?). A better option might be to detonate a warhead near the asteroid, letting heat from the explosion sear one side of the rock. As material vaporizes from its surface, the asteroid would accelerate in the opposite direction -- just enough (fingers crossed) to steer it away from Earth.
If explosions aren't your thing, but you still want to hit something, then you'll appreciate another technique known as kinetic impactor deflection. The "kinetic" in this case refers to kinetic energy, which all moving objects have and the universe conserves. But we're getting ahead of ourselves. Turn the page to learn how the behavior of billiard balls just might save our planet.