A lunar eclipse takes place when the sun, earth and
moon are all perfectly aligned with the Earth in the middle. When the
moon passes behind the earth, the sun's rays are blocked from striking the moon. This can only occur when the moon is full.
Unlike a solar eclipse, which can only be seen for a few moments from any specific spot, a lunar eclipse can be viewed for several hours.
The eclipse will happen Monday night on the West Coast and during the early hours Tuesday on the East Coast.