Our next-door neighbor
As earth whirls along on its endless journey through space, it has a
companion that is always beside it— the moon. The moon is a small
planet. It is only about one-fourth as big as earth.
The moon is our nearest neighbor in space. The stars are billions of
miles (kilometers) away. The sun is millions of miles (kilometers) away.
But the moon is only about 239,000 miles (384,000 kilometers) away. That
makes the moon truly a next-door neighbor.
In a way, the moon “belongs” to earth. Just as earth moves around and
around the sun, the moon moves around and around earth. It is held in
place by the tug of earth’s stronger gravity. A planet that is held by
another planet this way is called a satellite. The moon is earth’s
satellite.
The moon is a ball of gray rock, some of which is covered with dust. It
has no air or water—and, of course, no plants or animals. Its whole
surface is nothing but mountains and plains of rock. When we look up at
a full moon, we can often see dark patches. These dark places are the
lowlands. They seem to form a shadowy face that people have named “the
man in the moon.” The brighter parts of the moon are the highlands.
In ancient times, many people worshiped the moon. The Romans, who
thought the moon was a goddess, named it Luna. Our word lunar means
“of the moon.”
