•13. If the moon rose at about 7pm one night (and you know now that its phase would be full or close to
full, right?), at about
what time will the moon rise the next night? [Note I am looking for the typical difference
-- the fact that the
orbit of the moon is elliptical can cause variation in the exact number.]
•This one
is more involved than what we discussed in class so far, but if you follow it, you’re
getting the concepts
down well. The moon orbits the Earth
every 28
days. From moonrise one day, to the
same time the next
day, the moon has gone 1/28 of the way around the Earth and the Earth must go 1/28 a turn
farther for it to
rise again. Because the Earth must turn
farther, the rise
is later. 1/28 of a 24 hour day is
about 45 minutes, so
7:45 is the best choice.