black moon

Black moon refers to when there are two new moons in a single month. This is rare, but it can happen once every 32 months. New moons happen when the moon is between the Earth and the Sun, so we can't see it in the night sky. This happens because the Moon moves around the Earth in an orbit and it takes 29.5 days to go all the way around the Earth. While it's going around the Earth, the Sun, Earth, and Moon all line up together every 29.5 days. When the alignment of these three things is complete and the Moon is directly between the Earth and Sun, a new moon occurs. So if the Moon moved around the Earth twice in one month, a black moon would happen.