Death by meteorite

I recently wrote about the odds of getting hit by a meteorite. But what are the odds of getting killed by one?

Turns out, they're a lot higher! Why?

Because you are small and the Earth is big, getting knocked on the noggin by a meteorite is a low odds event. But a big meteorite, say one 100 yards across, doesn't have to directly fall on top of you to shuffle you off this mortal coil. It could land kilometers away and the blast wave (or the heat) could do you in. And a bigger one can land hundreds of kilometers away and still snuff you out, especially if it hits in the ocean and causes a big tsunami to march over the beaches and coastlines.

However, big asteroids coming in and whacking us are much rarer than small ones; if you go out on a clear night you might see a dozen meteors caused by rocks smaller than a grain of sand, but you could wait 100 million years for a dinosaur-buster. You have to account for that as well. This is a calculation worth doing, because a) a lot of people fret about it, and b) it could in fact mean the end of all life on Earth. That might be worth knowing.

Astronomer Alan Harris has made that calculation. Allowing for the number of Earth- crossing asteroids — the kind that can hit us because their orbits around the Sun intersect ours — as well as how much damage they can do (which depends on their size), he calculated that any person's lifetime odds of being killed by an asteroid impact are about 1 in 700,000.

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