AST 301
Homework #2
Due Friday Jan. 31
1. Look up the orbital period of the Moon (in Appendix A of Seeds).
This is the orbital period of the Moon as seen by a distant observer.
Knowing the number of days in a year calculate the number of lunar orbits
in a year (the answer won't be an integer).
Find a calendar which shows which day the Moon is full this month and next
month. How many days are there between this month's full moon and next
month's? This should not be the same as the orbital period. After you do
this problem you should know why and how they are different.
Calculate the number of lunar months in a year (that is, the number of
cycles from full moon to full moon. Again, the answer won't be an integer).
Get four people together, one to be the Sun, one the Earth, one the Moon,
and one to be a distant star. Have the Earth walk slowly around the Sun
while the Moon is walking more quickly in a smaller circle around the Earth.
Have the star count how many orbits of the Moon occur in a year (that is,
how many times the Moon is lined up between the Earth and the star in the
time it takes the Earth to walk once around the Sun). Have the
Sun count the number of full moons in a year (that is, the number of times
in a year the Moon lines up behind the Earth as seen by the Sun.
Discuss (verbally and then in writing) what your walking around tells you
about the difference between the number of lunar orbits in a year and the
number of months in a year. Note: our calendar month doesn't quite agree
with either of these.
2. Describe in a sentence or two how the path of the Sun across the sky
in June differs from its path in December. Explain why this difference
makes it hotter here in June.
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