A blood moon is a phenomenon where the moon has a reddish tinge when in total eclipse. The full moon is usually illuminated by sun rays and refracted by the atmosphere of the Earth to form the reddish color. In a total eclipse, the moon is entirely in earth’s shadow, and some sunrise and sunset rays that appear red may fall on the surface of the moon, bringing in the illumination of this red color.
The blood moon phenomenon also describes four total lunar eclipses that occur in a sequence or a row. Lunar eclipses only occur during a full moon, and this is when the Sun fully illuminates the Earth’s surface.