Chelyabinsk, a large city in western Russia, was best known for producing tractors and professional hockey players until the morning of February 15, 2013, when a 19-meter-wide meteor screamed through the sky and exploded with the force of 500 kilotons of TNT. The meteor generated a fireball many times brighter than the sun, so powerful it even caused sunburns. The shock wave blew out windows and knocked residents off of their feet, injuring more than 1,200. The object was the largest to strike Earth in more than a century... Asteroids that come within 28 million miles of our planet are...