Jennie Joy Lovelace, Age 14, Of Sioux City, Ia., for her question:
What are bolides?
The word bolide is coined from a Greek word for missile, and when a blazing bolide crashes down from the sky, you might well think that the earth is bcanbarded by missiles from mars. But before you have time to feel scared, chances are you will realize that the razzle dazzle event is just a falling fireball.
Bolides are related to fireballs, to so called shooting stars and falling stars. Meteors are space traveling lumps of minerals voyaging for countless ages through the solar system. Their space ways are enormous. But every hour thousands of speck sized meteors collide with the earth.
Traveling through empty space at perhaps speeds of 25 miles a second, a meteor suddenly crashes into the resisting air of the earth. It must ,jam on its brakes and slow down, and its speed energy is turned instantly into heat energy. The space traveler catches fire, and the speck sized meteors burn to ashes before they reach the ground.
A meteor of 10 pounds or more, however, is likely to survive the fall. It lards with a thud on the ground or into the sea with a splash. Its space traveling days are done, and the lump of grounded mineral is now called a meteorite. A large falling meteor is bright enough to turn night into day. We can call it a fireball or a bolide, though we usually use the term bolide for bolides that explode in the air.
For a few seconds, we see a blazing ball of red or yellow, white or bluish green arching down to earth. Behind it trails a streak of fiery vapor often fringed with pinwheeling sparks. When a bolide explodes high in the air, the dazzling fragments scatter in all directions. Air current high in the stratosphere soon twists the fiery train out of shape, the glowing specks and the whole spectap4 disappear in a few minutes.
Out in space, the bolide is a cold lump of dead minerals. It begins to slow down when it meets resistance frown the upper atmosphere and catches fire perhaps 100 miles above the ground. The sudden heat is terrific, and the fall is so fast that only the surface of the meteor catches fire. The inside remains stone cold, even after a meteor or its fragments strike the ground. The sudden surface heat may crack the lump of minerals, and it becomes an exploding bolide.
A meteor may travel the space ways of the solar system at 25 miles a second, while the earth rotates at 18i miles a second. If it strikes from one direction, its speed is added to that of the rotating earth. A fireball may start its collision at 45 miles a second. But the resisting air slows down this fantastic speed as the meteor falls. It hits the ground with no more force than any other falling body.