It's not random; the moon is actually moving through a cycle of eight phases known as the lunar cycle. The cycle lasts around 29.5 days, and happens as the Sun lights up different parts of the moon ...
March’s “worm moon” sets behind Rocca Calascio castle and village in L’Aquila, Italy. Photograph by Lorenzo Di Cola, NurPhoto/Getty Images Earth’s moon phases cycle from month to month, waning and ...