The phases of the Moon are a result of its position relative to the Earth and the Sun. As the Moon orbits Earth, sunlight illuminates only a portion of its surface. The phases we observe depend on the angle at which sunlight strikes the Moon and our viewpoint from Earth.
-
Illumination and Shadow: The Moon is a spherical body, and only the side facing the Sun is illuminated. As it moves in its orbit, different portions of the illuminated side become visible from Earth, leading to the various phases—from new moon (when the Moon is between Earth and the Sun and the illuminated side faces away from us) to full moon (when the Earth is between the Moon and the Sun, showing the fully illuminated side).
-
Relative Positions: The cycle of lunar phases occurs approximately every 29.5 days and includes several distinct phases—new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. The changing positions of the Earth, Moon, and Sun create this cycle of illumination, resulting in the beautiful variety of phases we observe in the night sky.
2 answers