When you look up at the night sky, you see stars. The brightest thing you see in the night sky, though, is the moon.

The moon is Earth's nearest neighbor, only 238,857 miles away. That's about 157 trips from New York to Los Angeles back and forth.

How Was the Moon Formed?

There are many theories on how the moon was formed. Some scientists think the moon was formed about 4.6 billion years ago when a huge object the size of Mars hit Earth. Debris from the crash came together and formed the moon.

Another theory says the moon was a small planet traveling around the sun. The Earth's gravity captured the moon, making it the Earth's satellite.

The Moon's Surface:

The moon has no atmosphere. Without an atmosphere, it has nothing to protect it from meteorites. That explains why every time you look at the moon in a picture, it's covered with 

craters. Some craters can be as large as 50 miles wide while others are as small as a pinpoint.  This all depends on how big the meteor was and how much impact it hit the ground with. Most meteors and comets burn up before they hit Earth. The friction generated by the speed of the meteor and our atmosphere would cause it to burn. Since there is no atmosphere on the moon, footprints left by Apollo astronauts will be visible for billions of years because there will be nothing to wash or blow them away.

The Moon's Gravity:

The Earth's gravity always pulls us down and keeps us on the ground.  It also holds the moon in its orbit. If the Earth's gravity disappeared, the moon would start to orbit the sun instead of Earth. The moon's mass is 1/81 of Earth's, so that's why the moon has less gravity than Earth. The moon also affects Earth because the moon's gravity pulls the water on Earth, causing tides in lakes and oceans.

The Moon's Orbit:

The moon travels around Earth in an oval shaped orbit at speeds reaching 2,300 miles per hour. Because its orbit is oval, the moon is not always the same distance from Earth. The perigee is the point where the Moon is closest to the Earth, only 221,456 miles away. The apogee is the point where the Moon is the farthest from the Earth, 252,711 miles away.

Temperature on the Moon:

The moon's surface changes from hot to cold more than any other place on Earth. The average temperature in the day on the moon can reach up to 261 degrees Fahrenheit. At night, the temperature can drop all the way to -279 degrees Fahrenheit. During the two week lunar night on the moon, craters by the moon's poles can drop to -400 degrees Fahrenheit.

Spacecraft Sent to the Moon:

For many hundreds of years, people have dreamed about going up to the moon. In the 1950's 

and 1960's, this dream came true. NASA and the former Soviet Union sent scientific spacecraft carrying probes up to the moon. These probes gathered information helping astronauts land on the moon.

In 1998, NASA launched the Lunar prospector to learn more about the moon. The probe's mission was to gather information to help find out how the moon was formed. It gathered some information but not enough to solve the mystery.

Big Red:

During a lunar eclipse the moon grows dim and has a dark orangey red color. This is known as ''The Big Red." This happens because the Sun's light passes through the Earth's atmosphere, which bends the light separating it into all the colors of the rainbow. Red is the only color to reach the moon. The red light bounces off the moon, making the moon appear red.

Lunar Month:

In ancient times, people watched the phases of the moon to keep track of time. An astronomer made a lunar calendar based on the changes of the moon. It took one lunar month for all the phases of the moon to start over again. The word month comes from the word "moon."

Facts About the Moon:

Everything You Need to Know and Beyond! </J0112388> Last Visited: February, 2002.

Space Today, Tomorrow, and Always. </J0112188> Last Visited: February, 2002.

Walker, Niki. The Moon. New York: Crab Tree Publishing, 1998.

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All pictures courtesy of NASA unless otherwise noted