World Without End

We can't do much to deflect a hurricane, but we may have a defense against asteroids, because a particularly pale asteroid could reflect so much sunlight that the photons would create enough force to steer it away.

A recent paper estimates that as little as five tons of paint-balls full of white powder could be launched towards an asteroid 20 years in advance of a possible collision with Earth. The force of the pellets' impact will push it off course slightly, but the albedo of the asteroid would also increase, and with it the number of photons bouncing off its surface, forcing the asteroid away from our planet.

This work won the United Nations-sponsored 2012 Move An Asteroid Paper Competition, vying against ideas such as nuclear detonation and projectile collision.

By the way, we may need this strategy soon, as astronomical observations say that the Apophis asteroid will come close to Earth in 2029 and again in 2036.