Asteroids are rock-like objects that orbit the Sun, and meteors are pieces of asteroids (or comets) that enter the Earth's atmosphere. They vary greatly in size and threat to us here on Earth. While small meteors occur every day, large meteors or asteroids are far more rare. According to NASA, an asteroid as big as a car will usually enter the Earth's atmosphere around once per year. This size will burn up before it hits the ground, creating an impressive fireball. Roughly every 2,000 years, an object the size of a football field hits Earth and causes significant damage.
Intrigued? Click through this gallery to discover some of the close calls from the last 20 years.