How long does it take the moon to rise and set each day in the sky?
The Moon’s disk is approximately one-half a degree wide. There are 720 half-degrees in a complete circle, and 24×60 or 1440 minutes in a day. So on the average it takes the Moon about two minutes to move its own width through the sky as the Earth rotates. You can check this by timing the full Moon as it crosses a wire that’s at a right angle to the direction the Moon seems to be moving. However, over the course of a month the moon moves backwards through the sky to return approximately to where it started. Also, the moon rides higher in the sky in the winter than it does in the summer. Finally, because of the slant of the moon’s orbit relative to the Earth’s equator, the time between successive risings of the Moon can vary from about forty minutes to well over an hour. The Moon’s main apparent motion, though, is due to the Earth’s rotation. Eight hours is one-third of a day, so the Moon would have seemed to move a bit less than one-third of 360°, that is, a bit less than 120° from wher
