Learn why lunar eclipses happen and how long they last.
A lunar eclipse happens only during a full moon when the moon is on one side of the earth and the sun is on the opposite side and all three bodies are aligned in the same plane.
In this alignment the earth blocks the sun's rays to cast a shadow on the moon. In a total lunar eclipse the moon seems to disappear from the sky when the whole moon passes through the umbra or total shadow created by the earth.
A total lunar eclipse may last up to one hour and 40 minutes. If only part of the moon enters the umbra, a partial eclipse occurs. A penumbral eclipse takes place if all or part of the moon passes through the penumbra (partial shadow or shade) without touching the umbra. It is difficult to detect this type of eclipse from earth. From the moon one could see that the earth blocked part of the sun only.