How can there be no moonset? What happens to the moon?
— M.S. A. When the moon rises, it surely sets, but it follows it own cycles, not a human clock. There was indeed no moonset yesterday. The moon set at 11:30 p.m. Thursday, rose at 3:03 yesterday afternoon, and then went down again just after midnight today. Just as the length of days varies with the seasons, the amount of time that the moon spends above the horizon (from moonrise to moonset) varies on different days. But although the length of days changes over the course of a year as the Earth makes one orbit around the sun, the time that the moon spends in the sky varies over the course of about a month — which is the length of time that it takes for the moon to orbit Earth. Also because of its orbit, the moon rises and sets later each day over the course of a month, by an average of about 50 minutes. Because of these factors, there is usually a day each month that does not contain a moonset, as well as a day that does not contain a moonrise. Times for moonrise and moonset — as we
