Tunguska

On June 30, 1908, a violent explosion occurred in the atmosphere over the Podkamennaya Tunguska River in a remote part of central Siberia. The blast's consequences were similar to a hydrogen bomb explosion. It sent up a mushroom cloud, leveled thousands of square miles of forest, and wiped out a herd of reindeer. The shock of the explosion shattered windows 600 miles (960 kilometers) away. A number of theories have been proposed to account for this event.

Some people thought that a large meteorite or a piece of antimatter had fallen to earth. (Antimatter is a substance that is the opposite of matter; it is believed that when matter and antimatter come into contact, they destroy each other.) However, a meteorite, composed of rock and metal, would have created a crater and none was found at the impact site.