How fast does the moon move?

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| Waning Gibbous | Third Quarter | Waning Crescent |

During a month or one lunar cycle, the Moon falls behind the Sun from day to day, traveling roughly eastward around the zodiac. The synodic period of the Moon (or lunar month) ranges from 29 to 30 days; the actual value (known to ancient Babylonian astronomers) is 29.53059 days.

The Moon and the Sun both fall behind the fixed stars from day to day as they move roughly eastward around the ecliptic; this is their zodiacal motion. The Moon completes one trip around the zodiac in one month; the Sun requires a year. So, subtracting out the daily motion to consider only their zodiacal motion, in one month (synodic period) the Moon gains one 360-degree lap on the Sun in their zodiacal race eastward. So how fast does the Moon move along the ecliptic?

360 degrees ÷ 29.53 days
= 12.19 degrees per day

Thus each day the Moon gains an average of 12.2 angular degrees eastward along the ecliptic from the Sun. This means that each day the Moon rises about 50 minutes later, although the actual moonrise delay varies considerably from this average value:

(24 hours/360 degrees) x (60 mins/1 hour) x (12.19 degrees/day)
= 48.8 minutes/day

(Note how the units of hours and degrees cancel out in the above equation, yielding an answer in units of minutes and days.)

Variation: At the latitude of Shawnee, the Moon delays its rising each day between 32 and 61 minutes (the former corresponding to a Full Moon one day after the September equinox and the latter representing a Full Moon two days before the March equinox). Watch the Moon two nights in a row at the same time of night to see for yourself how fast it moves!

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