Michael Tomlinson, aged 11, of Nashville, Tenn., for his question:
What makes a star fall?
Every day we get a close look at a star. It is about 93 million miles away from us. That is a good long distance. But it is as close as we would ever want to come to a star. It is so bright that no sensible person ever looks directly at its face. It is so hot that our earth would be ice‑cold without it. It is so big that our whole earth could fit inside it a million times.
This star, of course, is our own glorious sun. There are millions of stars like it in the heavens. As stars go, our sun is medium bright and medium sized. The stars that shine at night look small to us. But this is because they are such vast distances away. The skies are populated with these monstrous stars.
There are rules for stars; just as there 'are rules for everything else. There are traffic rules which keep the stars in their places. All of them travel. But they travel around in order, keeping their proper distances. It would be impossible for one of these great stars to fall out of the sky.
Sometimes we see a bright flash arch over the sky. There goes a falling star, we say. And naturally, we make a wish. Chances are, that falling star was no bigger than a grain of sand. It certainly was not one of the great stare falling through the sky.
The proper name for this kind of falling star is a meteor. It is part of our sun's huge family of heavenly bodies. The aunts family has nine planets. There are also moons and comets. The planets, moons and comets move around the sun keeping the traffic rules.
But there are also billions of Junior members of the sun family. Most of them are grains of dust. Some weigh a few pounds, a few weigh tons. These small relatives do not always keep the traffic rules. Sometimes they collide with a moon or a planet.
Every day and every night, thousands of these grain‑sized meteors bump into the earth. They have been traveling through empty apace with nothing to hinder their speed. Suddenly they strike the air above us. True, the air is not very dense to us. But it is a lot denser than empty space. The little meteor feels as though it has hit a brick wall.
It plows through the air as the earth's gravity pulls it down. It rubs against the particles of air like a match on a match box. This rubbing is friction. And friction causes heat. 'The meteor becomes hot enough to melt and burn. In a few seconds it has burned Itself to ashes.
Most meteors burn away before they reach the ground. Sometimes a larger meteor does not have time to burn entirely. It comes right through the air and lands on the ground with a thud. These fallen stones are called meteorites.