• A lunar eclipse occurs when the moon passes directly behind the earth into its shadow. The earth, sun and the moon are either closely or perfectly aligned, with the earth in the middle. The earth’s shadow blocks sunlight from reflecting off the moon, thus resulting in an eclipse – partial or total. A total lunar eclipse is dramatic, as the earth’s shadow (umbra) completely covers the moon. This can happen only when the sun, the earth and the moon are perfectly aligned. Anything less than perfection will create a partial lunar eclipse or no eclipse at all. An eclipse does not appear every full moon because the orbit of the moon (around the earth) lies in a different plane than that of the earth (around the sun).