When does the moon disappear?

The moon is not visible to observers on Earth during its new moon phase, when the moon is located on the same side of Earth as the sun. During this phase, the portion of the moon that is illuminated by the sun faces entirely away from the Earth.

The opposite phase from a new moon is a full moon, when the entire portion of the illuminated moon is visible from Earth, appearing as a fully illuminated circle. Between the new moon and full moon phases, the moon goes through two gibbous phases, two quarter phases and two crescent phases, changing the amount of the illuminated surface visible from Earth.