IDS 102
Name___________________
Phases of the Moon
Over the past month you have been collecting observations of the position of the Moon in
the sky, the time of day for your observation, and sketching the appearance of the Moon.
Use these observations to answer the following questions:
1. In what way did the appearance of the Moon change over this past month?
2. From your observations, is there a pattern to the positions of the Moon in the sky over
the previous month?
3. How do these observations agree or disagree with the predictions you made on the first
evening of class?
Once you have answered these questions, see an instructor for the next part of the
module.
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January and February, 2007:
Sunday
Monday
Tuesday
Wednesday
Thursday
Friday
Saturday
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2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
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21
22
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25
26
27
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31
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2
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IDS 102
Phases of the Moon- Part II
Along with this part of the module you should receive a two page handout of the
appearance of the Moon over the previous month. Look carefully at the appearance of the
Moon and describe how the Moon changed in appearance over the month and how your
observations were similar or different from this handout.
You may have noticed that if you could observe the Moon several nights in a row at the
same time each evening that the Moon was closer to the eastern horizon each evening.
Discuss what this observation tells us about the orbit of the Moon around the Earth.
What direction does the Moon revolve around the Earth? About how long would it take
the Moon to go completely around the Earth?
If we observe the Earth from a spaceship directly above the North Pole, we would see the
Moon move around the Earth in a _____________________ -wise direction. This is an
important perspective for the animations we will be using simulating the Earth and Moon
positions.
Earth
N
Moon
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To investigate the Phases of the Moon, we will use two approaches:
1) A light bulb, a ball that is white on one side and black on the other and a partner to
help you. Assume that your head is the Earth and the ball is the Moon. Your partner will
move the white/black ball around you so that the white part of the ball is always toward
the light bulb (the Sun) and the dark part is away from the light. As the Earth, you slowly
spin on your axis. How long does it take make one rotation?
2) A computer animation from the University of Nebraska:
http://astro.unl.edu/naap/lps/animations/lps.swf
Click on “show phase panel” and “show time tickmarks”
In the upper right corner of the screen is the phase panel. This will illustrate how the
Moon appears from the Earth. Also notice that when the web page first opens, the Moon
phase is a New Moon. You can click on start animation or you may click on days and
hours to move the Moon around the Earth.
Move the Moon to the “first quarter” phase as noted on the web site. How many days
after the new Moon is the first quarter? Sketch below how the Moon appears from the
Earth (shade the dark area of the Moon).
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Move the Moon in the animation to the “last quarter” phase. How many days after the
“first quarter” phase is the last quarter phase? Again, draw the appearance of the Moon
as it appears from Earth.
Get your partner to help you determine position of the Sun, Earth and Moon for the first
quarter phase and the last quarter phase using the ball and light. For these two phases,
what is the difference in the appearance of the Moon from the Earth?
Complete the orbit of the Moon around the Earth. Using both the days and hours button,
determine how long it takes the Moon to orbit the Earth once.
A solar eclipse is when we are in the shadow of the Moon and we can not see the Sun.
The lunar eclipse is when the Moon is in the shadow of the Earth. During which Moon
phase must a solar eclipse happen?
During which lunar phase does a lunar eclipse happen?
Eclipses are scheduled to happen this year (2008) on:
Feb 21 – total lunar eclipse
Aug 1 - total solar eclipse
Aug 16- partial lunar eclipse (only part of the Sun is obscured and it will not be visible in
the USA)
Notice that eclipses do not happen every time the Moon orbits the Earth. What ideas do
you have to explain this?
Check with an instructor before continuing.
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The orbit of the Moon is not in the same plane as the plane of the Earth’s orbit around the
Sun, therefore only sometimes do the Sun, Earth and Moon happen to be in the same line,
not every time the Moon orbits the Earth.
Draw the arrangement of the Sun, Earth and Moon in the space below for the “full
Moon” phase. (Notice that we are seeing only half of the Moon during a “full Moon”
phase, but this is the full surface that we can see from Earth.)
Draw the arrangement of the Sun, Earth and Moon for the new Moon phase.
Use the white/black ball and light to confirm that you understand the difference in a full
Moon and a new Moon.
A couple of important definitions:
Waxing Moon: the appearance of the Moon between the new Moon phase and the full
Moon phase. The lighted part of the Moon appears to get larger each evening with a
waxing Moon.
Waning Moon: the appearance of the Moon from the full Moon phase to the new Moon
phase. The lighted part of the Moon gets smaller each evening with a waning Moon.
In the arrangement of the Sun, Earth and Moon illustrated below, show where would one
see a waxing Moon and then a waning Moon?
Sun
E
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Determine which of the Moon illustrations below is waxing and which is waning: (We
suggest using the light, ball, and your partner to help you on this question).
Waxing or waning ?
Waxing or waning?
What logic did you use to determine your answers?
As you use the animation, you will notice times that the Moon appears to be a thin sliver
(called a crescent Moon) and times when the Moon is larger than a quarter Moon, but
smaller than a full Moon (called a gibbous Moon). Draw on the illustration below (we
are looking at the north pole of the Earth) the positions of the waxing crescent, waning
crescent, waxing gibbous, and waning gibbous Moons.
Sun
E
For review and to insure that you understand the positions of the various phases, locate
the positions of the eight phases we have described in the drawing below (again, our view
of the Earth is directly at the North Pole).
E
Sun
Check with an instructor before proceeding!
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End of module Questions:
When the Moon looks like this draw the
position of the Sun, Earth, and Moon in the
space below:
When the Moon looks like this draw the
position of the Sun, Earth, and Moon in the
space below:
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How much of the Moon is being illuminated by the Sun when the Moon appears like the
illustration below?
So, explain why we see the Moon as illustrated above.
waxing or
waning
waxing or
waning
How could you tell the difference?
Is the following Moon, waxing or waning?
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For each of the Moons below, determine the position of the Moon, Earth, and Sun, the
phase of the Moon, and what the Moon would look like 7 days later:
position
of Sun,
Moon,
and
Earth
waxing
or
waning
name for
this
phase
what
will the
Moon
look like
7 days
later?
When we observe the Moon, we always see the same side of the Moon. (Our first
observation of the “far side” of the Moon was when a satellite took photographs of the
surface in the 1960’s). Does the Moon rotate on its axis? Explain your reasoning.
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The following statements are either true or false. If the statement is true, defend your
choice in the space below. If the statement is false, state why the statement is false.
________ 1. A waxing gibbous Moon phase will be a few days before the full Moon
phase.
________ 2. When the Moon appears as it does below, it is possible to have a lunar
eclipse:
_________ 3. The time of day we expect to see the following phase of the Moon is in the
early morning, such as 5 or 6 AM.
Congratulations! You now have an honorary degree in Moon observation. Think
about what you have learned on the next night when you see the Moon!
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