Phases of the Moon

As moon orbits Earth, the Sun always illuminates one-half of the moon surface.  Viewed from Earth, the moon's phases are seen as different portions of the illuminated sphere.
No other object in the night sky is as spectacular as Earth's moon.  For almost all of recorded human history, the moon has inspired myths, songs, poems, and superstitions.

Phases of the Moon

The moon completes one revolution around the Earth in 27.3 days. During this orbit, the illuminated area of the moon increases and then decreases. This effect makes the moon appear to change shape. These phases (apparent changes in shape) of the moon are caused by the constant changes in relative positions of Earth, the Sun, and the moon.  When the moon and the Sun are on the same side as the Earth, the moon's dark side faces Earth. At this time, the moon's illuminated side is not visible from Earth.  This is the new moon phase.  The above figure illustrates the way light and shadow on the orbiting moon appear from Earth.  When the moon's position is opposite the Sun, we see a fully lighted moon, the full moon. The following video provides a brief summary on the moon moon-101

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