Over the course of one day, the moon will
rise and set just as the sun and stars do, rising in the east
and setting in the west. Unlike the sun which rises in the morning
and sets in the evening (by definition), the moonrise and moonset
times change drastically over the course of a month.
In this take home experiment, you will observe the motion and
changing phase of the moon over a portion of the moon's orbital
period (27 days).
Observations
This section requires that you make multiple observations over the course of about a week and a half, starting a few days after new moon (January 28). It is possible, and even probable, that you will be clouded out for at least a portion of this window of opportunity, so it is imperative that you remain aware of the weather conditions so that you can optimize observations on nights that are not COMPLETELY cloudy. Since you are observing the moon, you will be able to do the necessary observations even on cloudy nights.
1. A few days after new moon, go and observe the moon soon after sunset.
* Do all observations facing south.
* Note the date and time.
* Sketch its phase.
* Note whether it is east or west of the meridian. The meridian
is the imaginary line drawn on the sky from the north to the south
that divides the sky into two halves.
* Estimate how far (in degrees) the moon is east or west of the
meridian.
2. Repeat this for at least 6 of the next 10 nights at the same time each night. Put all of your observations into a table with the following information for each observation:
* The date & time of observation
* The number of days between observations
* The number of degrees and the direction away from the meridian
(e.g. 30 west)
* The number of degrees that the moon has moved (eastward or westward)
since the previous observation.
* The rate of motion of the moon since the previous observation
in degrees per night (Just as you did in the sun section, divide
the numbers of degrees that the moon has moved by the number of
nights since the last observation.)
Answer the following questions
1. What is the average rate of movement
of the moon over the course of your observations?
2. Based on this rate (degrees/day) how long would it take for
the moon to complete its orbit (360 ) around the earth?
3. How does this compare to the actual orbital period of the moon?
4. Why is it so critical that you do your observations at the
same time each night?
5. Draw a bird's-eye view diagram of the earth, moon, sun system.
Include in this diagram the moon in positions corresponding to
your multiple observations. Indicate also the direction of rotation
and revolution of the earth and moon respectively.
6. What phase must the moon be in just prior to a lunar or solar
eclipse? Draw these earth, moon, sun diagrams as well.
7. Find listings of daily moonrise and sunrise times for this
quarter and make a graph of the date vs. rising time for each.
(You can find these listings by looking in the newspaper, an almanac
or the Web.)
8. Sketch what these graphs might look like if you plotted them
for the entire year. How do the moon and sun graphs differ and
why?