June Shores, ago 9, of Williamsport, Penna., for her question:
What causes a star to fall?
A real star is big enough to swallow a million earths in one gulp. They are blazing monsters, scattered through the vast reaches of space, trillions of miles apart. Our sun is one of those blazing stars. Our earth is merely a little planet, one of nine children of the sun.
In the space between the planets there is a lot of debris. There are drifting pebbles, flying gravel, a few boulders and clouds of dust. There fragments are called meteors and every day countless numbers of them collide with the earth. When this happens we see a so‑called shooting star. A meteor, maybe no bigger than a grain of sand, bursts forth into blazing glory and, for a moment, it rivals the stars in the heavens.
No real star could fall from its appointed place in the heavens, for the stars obey strict traffic rules. All the stars we see in the sky are part of a vast cartwheel we call the Galaxy. The big wheel turns and turns, each star turning with it. Our sun is turning around with the Galaxy at about 170 miles a second, taking all its planets along with it.
A falling star then, is not really a falling star. For each monster star is fully occupied with its own orderly routine and could not possibly fall out of the sky. What looks to us like a falling star is a blazing fragment of dust, a meteor.
Meteors, big ones and little ones, have plenty of space between the planets. Out there in the cold of empty space, they are solid bits of rock or metal. And they whiz along at great speeds. Some astronomers estimate that a slow meteor travels around the Solar System at about 100,000 miles an hour. Space is empty, open of air, and there is nothing to resist their speed and slow them down.
When a meteor flies near the earth it feels the terrific pull of gravity. It is drawn down and down. It strikes the atmosphere which, after the emptiness of space, is like hitting a brick wall. The solid meteor rubs through the air like a match scraping on a matchbox. This causes friction and friction generates heat. Like a match, the speeding meteor heats up and bursts into flame.
We see the gloving meteor fall down in a bright arc and it looks for all the world like a falling star. Thousands of little meteors strike the earth every day and night. Most are burned to ashes long before they reach the ground. If a meteor originally weighed morn than ten pounds some of it may have survived the fall. It lands with a thud, after which it is called a meteorite.
No one knows for sure how the meteor dust and debris in the Solar System was formed. Some think the pieces may have been broken from a lost planet. Some could be dust loft from a passing comet. At times there are meteor swarms and hundreds of them swoop down from a certain region in the sky. Usually this follows the path of a long‑tailed comet.