Sometimes we can see very special, unique events in the sky when the Sun, Moon and Earth line up in a certain way. An eclipse is a shadow cast by one large object on another. A solar eclipse occurs when the Moon passes directly in front of the Sun and casts its shadow on the Earth in the middle of the day. In a lunar eclipse, the Moon passes through the Earth's shadow. During a full moon, when a lunar eclipse occurs, you can see the Earth's shadow move over the moon.