Lunar Phases

moon · space · cycles

The Moon doesn't actually change. The Moon itself stays the same size and shape, but from Earth it looks different because we see different amounts of its sunlit side as it orbits around us.

Eight phases in one month. The eight lunar phases are the new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The whole cycle takes about 29.5 days.

Same side always faces us. The Moon is tidally locked to Earth, which means it rotates at exactly the right speed so we always see the same side of it, just with different amounts lit up by the Sun.

The lunar month length varies. Because the Moon's orbit is slightly oval-shaped instead of perfectly round, a lunar month isn't always exactly the same number of days, but it averages about 29.5 days long.

Four major phases rule the sky. When people talk about Moon phases simply, they usually mean the new moon (completely dark), first quarter (half lit), full moon (completely bright), and last quarter (half lit on the other side).