Circling The Earth

It takes the moon about 29 days to go through all its phases. This amount of time is called a lunar month. It begins with a new moon. Then, after about 29 days, the lunar month starts over.

As Earth circles around the sun, the moon is circling around Earth. The same side of the moon always faces Earth.

The moon does not make its own light. We only see it because sunlight bounces off the surface of the moon and back to us. Different parts of the moon get sunlight at different times. The changes in sunlight are what make the moon look like it is changing shape each night.

Moon Phases

When the lunar month starts, the moon is between the Earth and the sun. The sun is lighting one-half of the moon. We only see the dark half of the moon. This makes it look like there is no moon at all. This phase is called the new moon.

As nights pass, the moon moves through the sky. We start to see more of the lit-up side of the moon. It looks like a thin sliver in the sky. This curved thin shape is called a crescent. The crescent moon gets bigger until half of the moon is lit up. This phase is called the first quarter moon.

The moon continues to get bigger. This is called waxing. When more than half of it is lit up the moon takes a rounded shape. This is called the gibbous moon. It keeps getting larger each night until the whole moon is lit up. This phase is called the full moon.

Then, the moon starts to get thinner each night. This is called waning. Soon, only half of the moon is lit up. As the moon gets even smaller, it becomes a crescent again. Then it becomes another new moon. The next lunar month begins. Try It At Home

You can use a lamp and a baseball to recreate the phases of the moon at home. First, place the lamp in the corner of a dark room. Remove the lamp shade, if it has one. Take a seat at the other end of the room. Hold up the baseball between your face and the lamp. Slowly move the ball around your head. The light on the ball will look like the phases of the moon.