NASA gives us five days to hide from asteroids

NASA has set up the Scout System to warn us of asteroids heading our way, and the good news is, it works!

The bad news, however, is that if it's big enough to wipe out the planet, we really don't have anywhere to hide, no matter how many days warning we have.

Recently, a telescope in Hawaii detected asteroid 2016 UR36 and three other telescopes confirmed its existence and its trajectory. They also learned its size, between five and 25 metres diameter.

They worked out it would "just" miss Earth by 498,000 km. But if it had been going to hit, it would have been another story.

For big asteroids there's probably not much we could do with five days except maybe play or watch a test cricket match. But for smaller meteorites like the one in Chelyabinsk, they might be able to evacuate towns and avoid casualties.

And in any case, the really big ones NASA already knows about - or so we hope. It has plans to launch a Deep-Impact-type redirect mission if they look like getting too close, and will commence the program in 2020, giving it time before a near-Earth event due in 2028.

If you want to see what a small piece of an asteroid can do, here is some amazing dash-cam vision of the Chelyabinsk meteorite crashing into the Urals in 2013.