TED演講: 我們?nèi)绾蔚钟E石的襲擊（1/2）

Here is how big of a crater was left. It was huge. To give you a sense of the scale, okay, there you go. The scale here is 50 miles on top, a hundred kilometers on the bottom. This thing was 300 kilometers across -- 200 miles -- an enormous crater that excavated out vast amounts of earth that splashed around the globe and set fires all over the planet, threw up enough dust to block out the sun. It wiped out 75 percent of all species on earth. Now, not all asteroids are that big. Some of them are smaller. Here is one that came in over the United States in October of 1992. It came in on a Friday night. Why is that important? Because back then, video cameras were just starting to become popular, and people would bring them, parents would bring them, to their kids' football games to film their kids play football. And since this came in on a Friday, they were able to get this great footage of this thing breaking up as it came in over West Virgina, Maryland, Pennsylvania and New Jersey until it did that to a car in New York. Now, this is not a 200-mile-wide crater, but then again you can see the rock which is sitting right here, about the size of a football, that hit that car and did that damage. Now this thing was probably about the size of a school bus when it first came in. It broke up through atmospheric pressure, it crumbled, and then the pieces fell apart and did some damage. Now, you wouldn't want that falling on your foot or your head, because it would do that to it. That would be bad. But it won't wipe out, you know, all life on Earth, so that's fine. But it turns out, you don't need something six miles across to do a lot of damage. There is a median point between tiny rock and gigantic rock, and in fact, if any of you have ever been to near Winslow, Arizona, there is a crater in the desert there that is so iconic that it is actually called Meteor Crater.