a person or thing that retracts. Anatomy. a muscle that retracts an organ or protruded part. Surgery. an instrument or appliance for drawing back an impeding part, as the edge of an incision. a mechanism, device, or the like that regulates retraction: to adjust the retractor on a seat belt.
The Moon orbits Earth in the prograde direction and completes one revolution relative to the stars in approximately 27.323 days (a sidereal month). Earth and the Moon orbit about their barycentre (common center of mass), which lies about 4,600 km (2,900 mi) from Earth's center (about 34 of the radius of Earth).
Best Answer: The Moon has phases because it orbits Earth, which causes the portion we see illuminated to change. The Moon takes 27.3 days to orbit Earth, but the lunar phase cycle (from new Moon to new Moon) is 29.5 days.The Moon spends the extra 2.2 days catching up because Earth travels about 45 million miles around the Sun during the time the Moon completes one orbit around Earth. Re-worded it a little.ne solar day = 24 hours, and 29.53 solar days is the synodic month. You are correct in saying it takes 27.3 solar days for the moon to orbit the earth-that's the sidereal month. But in addition to the moon orbiting the earth, the earth-moon system is orbiting the sun. That's why the sidereal and synodic months differ.