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How Does the Earth Affect the Phases of the Moon?

The sun's light illuminates half of the moon. The phases of the moon that we see depend on the moon's position in its orbit around Earth. This orbit, or lunar cycle, takes 29.5 days to complete.

New Moon
- Barely a crescent, just past new moon
  
  During this moon phase, the moon is between the sun and the Earth so the moon will "show" its dark side to Earth.
Crescent Moon
- Crescent moon
  
  The moon starts to show a portion of the illuminated side as it continues its orbit around Earth, away from the sun.
Quarter Moon or Half Moon
- Quarter or half moon
  
  The moon appears half full. First quarter moon occurs after the new moon, third quarter occurs after the full moon.
Gibbous Moon
- Gibbous moon
  
  Gibbous means "having a hump." This phase shows the moon a little more than half full.
Full Moon
- Full moon
  
  The moon appears completely illuminated. During this phase the moon is on the other side of Earth from the sun.
Helpful Terms
- Waning means "to decrease in size." Waxing means "to grow in volume." For example: a waxing gibbous moon will be heading toward full moon.

Astronomy