Scientists who study asteroids often say that Earth is drifting through a cosmic shooting gallery.
Some angry space rocks, like the recent Chelyabinsk meteorite that exploded over Russia, are big enough to shatter windows and crumble walls. Others, like the one that caused the Tunguska Event of 1908, can flatten entire cities. A handful can trigger global extinctions, like the asteroid that smashed into Mexico's Yucatan Peninsula 66 million years ago.
But how big of an asteroid does it take to damage cities, states, countries, and the planet?
Images in this story come from a previously published video.
Most of us go through life without thinking much about rocks from space. But even a small — and relatively frequent — asteroid can inflict great damage.
By numbers, most meteors are smaller than a car and burn up in the atmosphere as harmless meteors.
Any larger than that, and things start getting risky.
Some detonate into airbursts high above the ground. These explosions create shockwaves strong enough to break windows.
They can also emit enough light energy to cause a sunburn.
A house-sized meteorite can explode in Earth's atmosphere with a force greater than the nuclear weapon the US dropped on Hiroshima in 1945.
Such a space rock could flatten most buildings within 1.5 miles of ground zero.
An asteroid the size of a 20-story building is bad news.
With the right composition, speed, and angle of attack, a rock this size might leave a wake of destruction the size of central Paris.
One roughly the size of a football field could obliterate New York, causing a 7.7-magnitude earthquake that might be felt than 1,000 miles away.
An asteroid more than half a mile wide would start to have global implications.
It could destroy an area the size of the US state of Virginia.
Dust tossed up from the impact would block the sun and lead to rapid changes in climates across Earth.
The crater would be more than 100 miles wide.
The aftermath that follows would kill most life on Earth.
In fact, this is the same size as the space rock that killed the dinosaurs.
A London-sized asteroid would be more than just a major extinction-level event. Its impact would slow down Earth's rotation enough to make its day last almost half a second longer.
The largest known asteroid, Ceres, is about the size of Texas.
Lucky for us, Ceres has no chance of striking Earth.
Watch our full video about how much damage asteroids can do.