mark@hp-pcd.UUCP (09/24/83)
#R:cbosgd:-32700:hp-kirk:7200006:000:978
hp-kirk!mark Sep 22 09:18:00 1983
On the average the moon will complete a trip around the earth in
27 days, 7 hours, 43.2 minutes (this is the sidereal period);
however, the lunar month (which is the more relevant period) is
the time from one new moon to the next new moon and due to the
earth's motion around the sun, this period (the synodical period)
is about 29 days, 12 hours, 44.05 minutes. This latter figure
works out to a lunar month of 29.5306 days. The seasons are
based on the tropical year which today is about 365 days, 5
hours, 48.75 minutes (but has been decreasing by about .5 seconds
per century). This works out to a tropical year of 365.2422
days. Given all of this there are 12.3683 lunar months in a
tropical year. The closest whole number values result in a year
consisting of 12 months of 30 days each.
from the almanac of
Mark Rowe
hp-cvd!mark
Corvallis, Oregon