Exercise:
The Moon was New on December
25th, 2000.
At St.Andrews, on January 1st 2001,
the Sun crossed
the meridian at 12:15.
At what time did the Moon cross the
meridian?
On January 1st,
7 days had
elapsed since New Moon
(the Moon was "7 days old").
So
the Moon was lagging the Sun by 7x48.8 minutes = 5h42m.
So it would cross the meridian at 12:15 + 5h42m = 17:57.
In fact it crossed the meridian
at 17:24,
so our calculation is in error by 33 minutes.
The
error is due to:
(a) not knowing the exact
time of New Moon on December 25th
(b) the Moon's
motion not being constant.
Back to "The Moon".