Can you see the moon?

Does it look like a big round ball? Or is it just a sliver of light in the sky? The moon seems to change. But it doesn't really. The moon revolves around the Earth. It takes about four weeks to make the journey, and as it travels round we can only see certain parts of it. Try the simple experiment described inside using an orange, a pencil, and a flashlight, and you'll understand why the moon seems to change.

Franklyn M. Branley was the originator of the Let's-Read-and-Find-Out Science series and the author of close to 150 popular books about scientific topics for young readers of all ages. He was Astronomer Emeritus and former Chairman of the American Museum of Natural History-Hayden Planetarium.