美国有线新闻 CNN 2013-02-20

 As we kick off a new week of CNN studentnews, we're going to start with what in the world caused this. Well, forstarters, it wasn't from this world, it was a meteor and left that trail in thesky and casued a lot of problems on the ground.

In Russia, more than a thousand people wereinjured, most of that was from flying glass, the shock wave from this meteorshattered more than 75,000 square miles of glass. Here is an idea of whathappened. Friday morning, this meteor entered the earth atmosphere. When thathappened, it exploded, broke up into a lot of smaller pieces and caused thishuge light and a massive 2 sonic boom 3. That boom came from the energy of themeteor when it hit the atmosphere. The thing was around 55 feet wide, weighedaround 10,000 tons, so that's about 20 million pounds.
"It was traveling at 33,000 miles perhour, and as it decelerated, it's kind of like a swimmer doing a belly 4 flopfrom a very high diving board into water. But you know, it was travling a lotfaster than the swimmer, so that energy has to go somewhere. Then energy wentinto light, that's you saw on that street. When it was hitting up the column ofair, and the injuries why it happened because people naturally went to theirwindow and saw this bright light, because light travels faster than sound. Andthen the sound arrived and shattered 1 the windows when everybody was looking outof their window."
It's easier to talk about the sciencebehind a sonic boom once it's over. But living through a firsthand can beterrified. We've got to look at that from this video inside a Russian highschool.
There's been a lot of news reports the pastcouple of weeks about an asteroid 5, it passed by the earth on Friday, the sameday this meteor exploded over Russia. The tow 6 had nothing to do with eachother, Tom Foreman has more on the one that stayed in space.
"This really was a very close call, withthis asteroid in a cosmic 7 sense. Let's get the lay of the land so we canunderstand how close it was, we also talk about the Moon as being close to theEarth, the Moon isn't really all that close, the Moon is some quarter millionmiles out there. What's much much closer are satellites, the ones we've beenlaunching for decades now. The furthest ones away from us from the surface ofthe Earth, about 22,000 miles out there. This asteroid actually cut across thesouthern hemisphere 8 and right through the outer edge of those satellites. Sothe Earth is right here, we're talking about some 17,000 miles above it, goingthrough those satellites. Now there is no real danger it was going to hit thesatellites because we don't have that many of them, frankly 9. They are small,and this was actually fairly small too, but let's look at the stats to talkabout that, some you may it was known as 2012 DA14, it was about half the sizeof a football field, it was traveling close to 17,000-18,000 miles an hour. Andif it had hit the Earth, we're told that would explode with the force of morethan 2 million tons of dynamite 10. what would that be like? How big would thatbe? Well, by comparison, let's think about what happened in Russia where thatmeteor exploded in the atmosphere, about 30 miles above the Earth and producedall of that damage. That was about this big, if it were actually here rightnow, my comparison to it would be, about like this, it's not really that large.The asteroid that missed us, however, was more like this size. And you can justimagine the impact comparatively if this came in and exploded in theatmosphere, or if this actually hit the Earth, and bear in mind, this is arelatively small asteroid. That's one of the reason so many scientists watchedwith interest and so many people are asking, is there something we might beable to do, if something bigger than this starting heading our way?"