Question: How would you prevent collisions from happening?

Alan Fitzsimmons answered on 17 Mar 2014:

Scientists have had lots of ideas, but there are three good ways we think we could do this.

First, we can run a small spacecraft into a asteroid at high speed. Something called momentum will be given to the asteroid – basically it will get a small kick. This will slightly nudge the asteroid onto a new path so it misses the Earth.

Second, Sir Isaac Newton showed us that gravity means everything pulls on everything else (although the pull might be so weak you don’t notice). So we could hover a large spacecraft over an asteroid, and its gravity would slowly pull the asteroid onto a new path, so it misses us.

Finally, we could explode a nuclear bomb above the surface of the asteroid. That would give the asteroid a big kick onto a new path so that is misses us. But mucking about with nuclear weapons is dangerous, and we’d rather not do this unless we have to!