BERLIN (AP) — A meteor exploded in the sky above Russia's Ural Mountains on Friday, causing a shockwave that blew out countless windows and injured more than a thousand people. Here's a look at those objects in the sky:
Q. What's the difference between a meteor and a meteorite?
A. Meteors are pieces of space rock, usually from larger comets or asteroids, which enter the Earth's atmosphere. Many are burned up by friction and the heat of the atmosphere, but those that survive and strike the Earth are called meteorites. They often hit the ground at tremendous speed — up to 30,000 kilometers an hour (18,650 mph) — releasing a huge amount of energy, according to the European Space Agency.
Q: How often do meteorites hit Earth?
A: Experts say smaller strikes happen five to 10 times a year. Large meteors such as the one in Russia on Friday are rarer, but still occur about every five years, according to Addi Bischoff, a mineralogist at the University of Muenster in Germany. Most of them fall over uninhabited areas where they don't injure humans.
Q: How big was Friday's meteor and why did it cause so many injuries?
A: Before it entered the atmosphere, the meteor was about 15 meters (49 feet) in diameter and had a mass of about 7,000 tons, NASA says.
The space agency also says the fireball from it, which was brighter than the sun, is the biggest reported in more than a century, since a 1908 event in Siberia. The blast released the equivalent of hundreds of thousands of tons of TNT. The huge release of energy shattered windows and sent loose objects flying.
The blast produced 20 times or more the explosive force of the U.S. bomb dropped over Hiroshima during World War II. But the bomb detonated just 2,000 feet above a densely populated city, while the Russian fireball exploded miles in the air, reducing the potential damage.
Q: Is there any link between this meteor and the larger asteroid that passed Earth later on Friday?
A: No, it's just cosmic coincidence. According to NASA, the trajectory of the Russian meteorite was significantly different from that of asteroid 2012 DA14. "In videos of the meteor, it is seen to pass from left to right in front of the rising sun, which means it was traveling from north to south. Asteroid DA14's trajectory is in the opposite direction, from south to north," the U.S. space agency said.
Q: When was the last event like this?
A: In 2008, astronomers spotted a meteor similar to the one in Russia heading toward Earth about 20 hours before it entered the atmosphere. It exploded over the vast African nation of Sudan, causing no known injuries.
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