How could we save the planet from a killer asteroid?

Gravitational tug

What is wonderful about space is that physics becomes a strange and idealized thing. If you imagine trying to pull a rock of several million tons on Earth, it seems almost impossible. But in the space, the frictions cease to exist. The bodies move according to gravity. So, if you place something heavy near an asteroid, you can remove it from the frame.

This method is slow. This would only change the course of the asteroid at the rate of millimeters or centimeters per second and year. So you need a lot of time. But if we found a monster asteroid heading towards us within a hundred years, this method is the surest and simplest way to deflect it.

As an inverted tug, scientists have also considered monitoring beams of ions. This basically means that a spaceship flies alongside the asteroid and covers it with plasma, thus repelling it. Of course, the spacecraft must be constantly approaching at the same time, otherwise the effect of "equal and opposite reaction" in physics would simply result in the spacecraft moving away in equal measure. Like the gravity tractor method, this method is slow but predictable and possible using existing technology.

Or, to simplify this idea, other scientists have suggested simply painting a white asteroid to increase its reflectivity. This equates to more sun photons bouncing off its surface, and the extra pressure would serve to gradually move it away from its path.

Dismantling of an asteroid

There are also other more successful methods.

We could blow it up with a laser, for example. The goal here is not really to destroy the rock (although that's part of it), but rather to push it with the laser and use the pieces that flake off to help further move the asteroid away from the laser . But since we do not currently have a giant space laser, this method requires a little more planning.

Another option is commonly called mass driver. It takes the "equal and opposite reaction" to its logical conclusion. In its most basic form, imagine a catapult throwing rocks from an asteroid. Physics dictates that when you throw small rocks at Earth, the asteroid itself will escape.

All of these methods require a prior warning. The good news is that asteroids big enough to end life on Earth are big enough to be spotted, so we'll have plenty of time to panic and plan.

Korey Haynes is a Astronomy contributing author.