What are the causes of a lunar eclipse?

A series of four total lunar eclipses in a row is called a tetrad, or four Blood Moons. See how lunar eclipse tetrads work in this Space.com infographic. read more

[Amazing Total Lunar Eclipse Photos] Four Blood Moons: Total Lunar Eclipse Series Not a Sign of Apocalypse. Lunar eclipses occur in pairs with solar eclipses, two weeks apart. This is because the Earth, sun and moon must be aligned for an eclipse to occur, and the alignment can only happen twice during the moon's month-long orbit. read more

A lunar eclipse occurs when the earth passes between the sun and the moon during a full moon phase. The moon enters the earth's shadow, which consists of two parts: the umbra, or inner, dark shadow, and the penumbra, or the outer, hazy shadow. read more

A penumbral lunar eclipse occurs when the Moon passes through Earth's penumbra. The penumbra causes a subtle dimming of the lunar surface. A special type of penumbral eclipse is a total penumbral lunar eclipse, during which the Moon lies exclusively within Earth's penumbra. read more