Total lunar eclipse. Sequence of optical images of the total eclipse of the Moon of 9th January 2001. The sequence runs from top right to bottom left. A lunar eclipse occurs when the Earth passes directly between the Moon and the Sun in space, and the Moon enters the shadow cast by the Earth. Even when totally shadowed, the Moon does not disappear. It is still visible due to the sunlight refracted onto its surface by the Earth's atmosphere. The Moon usually appears reddish in such circumstances, because blue light is scattered more during its passage through the Earth's atmosphere.