Here. There. Everywhere.

You are relaxing with a book on a nice sunny day when a friend leans over your shoulder and the page goes dark. "Hey, you're blocking my light!" It is a familiar

experience. Any time an object blocks the light from another source, it can form a shadow.

Learn more about Shadows.

People in Shadow.: When a light source is blocked, a shadow results. Here we see the familiar shadows from people on a beach whose bodies are blocking the light of the Sun from reaching the sand behind them.; Image: Stock Photography

Lunar Eclipse.: The light we see from the Moon is produced by reflected light from the Sun. During a "lunar eclipse," the Earth blocks the light from the Sun and casts a shadow over the Moon. Some light is bent by the Earth's atmosphere and does reach the lunar disk, producing the (often-seen) faint red glow.; Image: John Chumack/Science Photo Library

A Moon of Jupiter.: Shadows occur on other planets as well. In this image, sunlight shining onto Jupiter is blocked by one of its moons as it passes over the face of the planet. A similar type of event takes place on Earth during a solar eclipse, when the Moon blocks the Sun's light and casts a shadow onto some portions of the Earth.; Image: NASA/Cassini