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what exploded over russia

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presented by science at nasa

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when the sun rose over russia's ural

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mountains on friday february 15th

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many residents of nearby chelyabinsk

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already knew that a space rock was

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coming

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later that day an asteroid named 2012

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da14 would pass by earth only 17 200

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miles above indonesia

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there was no danger of a collision nasa

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assured the public

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maybe that's why when the morning sky

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lit up with a second sun and a shockwave

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shattered windows in hundreds of

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only a few people picking themselves off

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the ground figured it out right away

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this was not a crashing plane or a

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rocket attack

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it was a meteor strike the most powerful

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since the tunguska event of 1908 says

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bill cook of nasa's meteoroid

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environment office in a one in a million

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coincidence that still has nasa experts

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shaking their heads a small asteroid

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completely unrelated to 2012 da14 struck

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earth only hours before the publicized

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event

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incredible to see them happening on the

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same day says paul chodes of nasa's near

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earth object program at jpl

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researchers have since pieced together

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what happened

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the most telling information came from a

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network of infrasound sensors operated

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by the comprehensive test ban treaty

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organization

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their purpose is to monitor nuclear

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explosions

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infrasound is a type of very low

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frequency sound wave that only elephants

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homing pigeons and a few other animals

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can hear

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it turns out that meteors entering

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earth's atmosphere cause ripples of

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infrasound to spread through the air of

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our planet

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by analyzing infrasound records it is

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possible to learn how long a meteor was

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in the air which direction it traveled

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and how much energy it unleashed

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the russian meteor's infrasound signal

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was detected by multiple stations

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including one in alaska more than 6 500

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kilometers from chelyabinsk

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western ontario professor of physics

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peter brown analyzed the data

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the asteroid was about 17 meters in

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diameter and weighed approximately 10

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000 metric tons he reports

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it struck earth's atmosphere at 40 000

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miles per hour and broke apart about 12

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to 15 miles above earth's surface

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the energy of the resulting explosion

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exceeded 470 kilotons of tnt

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for comparison the first atomic bombs

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produced only 15 to 20 kilotons

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based on the trajectory of the fireball

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analysts have also plotted its orbit

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it originally came from the asteroid

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belt about 2.5 times farther from the

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sun than earth says cook

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comparing the orbit of the russian

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meteor to that of 2012 da14 nasa orbit

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analysts have shown that there is no

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connection between the two these are

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independent objects cook says the fact

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that they reached earth on the same day

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one just a little closer than the other

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appears to be a complete coincidence

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infrasound records confirm that the

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meteor entered the atmosphere at a

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shallow angle of about 20 degrees and

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lasted more than 30 seconds before it

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exploded

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the loud report which was heard and felt

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for hundreds of miles marked the

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beginning of a scientific scavenger hunt

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thousands of fragments of the meteor are

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now scattered across the ural

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countryside and a small fraction have

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already been found

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preliminary reports mainly communicated

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through the media suggest that the

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asteroid was made mostly of stone with a

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bit of iron in other words a typical

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asteroid from beyond the orbit of mars

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says cook

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there are millions more just like it

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and that is something to think about as

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the cleanup intelligence continues