Repetition of Lunar Position ```Name: Fred Status: other Grade: other Location: NV Country: N/A Date: N/A ``` Question: If you draw a line on the quarter moon, then some times the hemisphere is up, sometimes left etc. Does the reoccurrence in position ever repeat itself and can it be used as a calender? Can the angle of a quarter moon be calculated as a date, or is it totally random? Replies: Dear Fred, I believe that this "line" is a function of your latitude. The quarter Moon will always appear to "point" in one direction depending on your latitude. Sincerely David H. Levy Fred This URL http://www.windows.ucar.edu/tour/link=/the_universe/uts/moon1.html tells us the moon orbits the earth every 27.322 days. This means that the orbit of the moon around the earth is periodic. That means the moon's position can be predicted on an (almost) monthly basis because it the position repeats itself every 27.322 days. This URL http://csep10.phys.utk.edu/astr161/lect/time/moonorbit.html shows how the phases of the moon appear from the earth as the moon is radiated by the Sun's light. And again, since this is a periodic phenomenon, the occurrence of the quarters repeat in a 27.322 day cycle. You cannot get an absolute date from the moon's phase (like October 12, 1492), but you could derive a relative date in the 27.322 cycle. Sincere regards, Mike Stewart Click here to return to the Astronomy Archives

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