What Is a Satellite?
Can you remember when you first noticed there was a moon in the sky? Did you understand it was circling the earth? Astronomers that lived thousands of years ago believed that it was, but ancient maps reveal that they thought the sun was, too! The moon is a satellite of Earth, just as Earth and the other planets are satellitesof the sun. How many moons do you think there are in the solar system? There are over a hundred and still counting. Who knows? Maybe in the future they will find more moons circling the planets that they have discovered orbiting around other stars. Many of the other moons in the solar system are much larger than the earth's moon. Some are even larger than a few of the planets, but none of them have a moon that is so close to the size of its planet like Earth's is. Although there may be more interestingmoons than Earth's, none seem to have as much of an effect on their planets. It took a long time before the people on Earth decided they could build other satellites that could be as helpful to them as their natural satellite the moon. There have been thousandsof artificial satellites placed in orbit by spaceshipsand rockets. Can you guess what some of them are used for each day? If you said forecasting the weather, you're right! They are also used for sending and receiving television and telephone signals, navigation, and many other things. Most of these satellitestravel at a certain speed, to orbit the Earth in twenty-four hours, and at a certain altitude, around 22,000 miles, to remain in exactly in the same positionabove a certain spot on Earth.