Look up at the clear night sky. What do you see? You can see thousands of stars. There are too many stars for us to count. The biggest thing you'll see, of course, is the moon. Sometimes it shows up late in the day and seems to disappear in the morning. For thousands of years, people have wondered about this big thing in the sky.
Earth's moon is a satellite. A satellite is a body that orbits a planet. All moons are satellites, and many planets have them. Some have many moons. Earth, of course, only has one. It's the fifth-largest moon in the solar system!
The moon looks as big as the sun. It only looks that way because it's much closer to Earth. The moon is so close that you can see its dark and light spots without a telescope. You can also see big craters on the moon's surface.