Why does a lunar eclipse occur either two weeks after a total solar eclipse?
An eclipse occurs because one heavenly body moves between another body and the Sun. For the Moon to be eclipsed, the Earth must be between the Moon and the Sun. For the Earth to be eclipsed, the Moon must be between the Earth and the Sun. Because the Moon orbits the Earth every four weeks, it will be on the opposite side of its orbit in two weeks. Therefore, a total eclipse of the Sun can be followed in two weeks by a total eclipse of the Moon.
