If we see magnificent plumage in the night sky, we may think of giant meteors, but in reality, most meteors are the size of small pebbles or even grains of sand. In fact, scientists think of them as cosmic “dustballs” careening through our atmosphere. Most meteors come to life in the part of the atmosphere called the thermosphere, which is generally 50 to 75 miles above Earth. But don’t take out your yardsticks to start measuring. “This is a general guideline only, since very fast meteors may first become visible above this height, and slow, bright meteors may penetrate below this band,” according to the American Meteor Society.