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1 .This is Scientific American's 60-Second Space. I'm John Matson. Got a minute?
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2 .The Russian city of Chelyabinsk had a rude awakening early on February 15th when a meteor exploded overhead.
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3 .The blast wave shattered windows and injured an estimated 1,000 people.
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4 .Based on preliminary evidence from infrasound stations built to monitor nuclear tests, this looks to be an historic event.
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5 ."We know that the energy of the explosion was about 300 kilotons of TNT equivalent."
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6 .Margaret Campbell-Brown, a professor who studies meteoroids at the University of Western Ontario.
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7 ."So it was a very, very powerful explosion.
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8 .It was the biggest explosion from a meteor that we've seen in the atmosphere since 1908, since the 1908 Tunguska impact."
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9 .The cause appears to be an asteroid, which Campbell-Brown estimates was 15 meters across.
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10 .Objects of that size are expected to hit Earth only once every half-century or so.
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11 .And impacts over cities of more than one million people such as Chelyabinsk are rarer still.
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12 ."When you consider all the areas of the Earth that are uninhabited--the oceans, the ice caps, the deserts and so on,
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13 .it's very surprising that this happened over such a populated area. Very unlucky."
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14 .Thanks for the minute, for Scientific American's 60-Second Space. I'm John Matson.
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