Everything you need to know about meteor strikes

On Friday, a meteor exploded 32,000 feet above the Chelyabinsk region of Russia, lighting up the sky and producing a shockwave that shook buildings and shattered windows. At least 1,000 people were injured in the blasts, the highest toll ever caused by an object from space. Video footage of the meteorites, while mesmerizing, is also terrifying. It "appeals to our most primitive fears," tweeted The Week's D.B. Grady. "It's an astonishing glimpse at the end of the world." Here's what you should know about Russia's meteor blast, and others like it:

First off: What exactly is a meteor?

Meteors are space rocks that find their way into Earth's atmosphere. They can be as small as a grain of sand or as big as a boulder. They usually burn up during their descent. The ones that survive are called meteorites, and they can hit the Earth at speeds of up to 18,600 mph.

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How often do they hit Earth?

Small strikes occur once every few months, but often go unnoticed. "Two-thirds of the Earth is ocean, so we tend to miss them," says Robert Massey of Britain's Royal Astronomical Society. He estimates the object that exploded over Russia was roughly 30 feet across upon entry, and weighed eight to 10 tons. Meteorite strikes this big are rare, but still happen about once every five years. In 2008, for instance, a big meteor exploded over Sudan. No one was hurt.

Can we detect these meteors before they hit?

Not really. Meteors like this go mostly undetected by telescopes, which are busy scanning for massive asteroids. And even if we do manage to spot an incoming rock, "there's not a weapon forged by man that could do something about it," says Spencer Ackerman at Wired. But don't worry: "You're thousands of times more likely to die by car on [your] way to work" than by meteor strike, says Brian Weeden of the Secure Earth Foundation.

What's the worst-case scenario for a meteorite strike?

The largest meteorite strike in recorded history was in 1908, also over Russia. Know as the "Tunguska event," the blast from the impact was more powerful than the atomic bomb dropped on Hiroshima. It leveled millions of trees, but miraculously, no one was killed. If a similar impact happened over a metropolitan area, the city would be destroyed. "It's a global challenge and we need to find a solution together," says European Space Agency spokesman Bernhard von Weyhe.

Check out footage of Friday's strike over Russia: