<P> A lunar eclipse occurs when the Moon passes directly behind Earth and into its shadow . This can occur only when the Sun, Earth, and Moon are exactly or very closely aligned (in syzygy), with Earth between the other two . A lunar eclipse can occur only on the night of a full moon . The type and length of a lunar eclipse depend on the Moon's proximity to either node of its orbit . </P> <P> During a total lunar eclipse, Earth completely blocks direct sunlight from reaching the Moon . The only light reflected from the lunar surface has been refracted by Earth's atmosphere . This light appears reddish for the same reason that a sunset or sunrise does: the Rayleigh scattering of bluer light . Due to this reddish color, a totally eclipsed Moon is sometimes called a blood moon . </P>

What occurs at a full moon when the earth is directly between the moon and the sun