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).
The Moon itself puts out no light at all. It takes about four weeks for the Moon to orbit once around Earth. During this time, the Moon's position relative to Earth and the Sun is constantly changing. During part of its journey, the Moon is between Earth and the Sun. Then, a few days later, it is off to one side.t takes about four weeks for the Moon to orbit once around Earth. During this time, the Moon's position relative to Earth and the Sun is constantly changing. During part of its journey, the Moon is between Earth and the Sun.