In 1947, a meteorite fell on the Sikhote-Alin Mountains in the southeastern area of the then Soviet Union. An estimated 23 tons of fragments survived this fiery passage, leaving a smoke trail 20 miles long and producing a bright flash and loud boom that could be observed from 190 miles away. At 3.5 miles from the Earth's surface, the largest area of the meteor exploded in what's called an air burst, spreading pieces around a half square mile and embedding fragments into surrounding trees.