Thousands of meteorites enter Earth’s atmosphere and
fall harmlessly to the ground each year. One widely
accepted theory is that the impact of an asteroid 6 miles
(10 kilometers) in diameter could have been responsible
for the extinction of many life forms, including the
dinosaurs 65 million years ago.
On June 30, 1908, a small asteroid of approximately
200 feet (60 meters) in diameter exploded at an altitude
of 5 miles (8 kilometers) over the remote region of
Tunguska in Siberia. The explosive energy from the
meteor was so great that half a million acres of Siberian
forest were devastated, and some trees were knocked
over at distances as far as 25 miles (40 kilometers) away.