IDS 102
Your Name___________________
The other members of your group:
Phases of the Moon, Part 1: Your Observations
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. You will
need to use this data and data from your group mates to answer the following questions:
Pick a short name for your group and summarize your observations below:
Your group’s name =
.
 On how many were you personally able to record the position of the moon:
?
 Were there any days that the other members of your group had observations, but you did
not? If so, list these dates below.
On the moon observations table provided, show the shape of the moon that your group observed
on the dates noted.
In the column marked “observer, “list your initials and those of everyone who observed the
moon on a given day (Note: List “all” if everyone has an observation).
After you have compiled the data for your group, check with the other groups to see if they have
additional observations that you do not. If they do, then add their observations to your table,
noting the name of their group in the “observer” column.
Check to see if there are any clear days where nobody could see the moon. If so, write the word
“not visible” in the “shape of the moon” column.
Use the information recorded in your table to answer the questions below:
 Describe how the size and shape of the moon changed over this past month.
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Check with your instructor for the next step
 Look carefully at the appearance of the Moon on the handout provided and describe 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.
Examine your observation and the sheet provided and come up with an estimate of how
long it takes the moon to go through 1 complete phase change. This time is equal to the
time it takes the moon to complete 1 orbit 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 counter clock-wise direction as shown below. 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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Phases of the Moon, Part 2: Models of the Earth-Moon System
To investigate the Phases of the Moon, we will next use a computer animation from the
University of Nebraska from the website: http://astro.unl.edu/naap/lps/animations/lps.swf
You should see something similar to the image shown below. Click on “show time tickmarks”
in order to show the times around Earth.
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 the + or – symbols next to “days” to move the Moon
around the Earth.
 Complete the orbit of the Moon around the Earth. Using both the days and hours button,
determine as precisely as possible how long it takes the Moon to orbit the Earth once.
 What is the name of the 1st phase after “new moon”?
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 Move the Moon until the “first quarter” phase is noted “moon phase” box in the upper
right hand corner of the screen. How many days after the new Moon is the first quarter?
Sketch the relative position of the moon and sun and the shape of the Moon as it appears
from the Earth (= moon phase). Be sure to shade the dark area of the Moon.
 Move the Moon until the “last quarter” phase is noted “moon phase” box. How many
days after the “first quarter” phase is the last quarter phase? Sketch the relative position
of the moon and sun and the shape of the Moon as it appears from the Earth (= moon
phase). Be sure to shade the dark area of the Moon.
Pick up a light bulb and a ball that is white on one side and black on the other. Pick 1 person to
represent the Earth. Assume that the head is the Earth and the ball is the Moon. Your partners
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 need to slowly spin on your axis – each rotation = 1 day.
Get your partners to help you determine relative positions of the Sun, Earth and Moon for the
new moon and the full moon using the ball and light.
 Sketch or describe the relative positions of the moon and sun during the “new moon”
phase.
 Sketch or describe the relative positions of the moon and sun during the “full moon.”
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The orbit of the Moon is not in exactly the same plane as the plane of the Earth’s orbit around
the Sun. However, sometimes do the Sun, Earth and Moon happen to be in the same line.
When this happens there is an eclipse.
 A solar eclipse is when we are in the shadow of the Moon (in other words when the moon
is between us and the Sun) so that we can not see the Sun. During which Moon phase
must a solar eclipse happen?
 A lunar eclipse happens when the Moon crosses into the shadow of the Earth (or when
the Earth comes between the Sun and the Moon). During which lunar phase does a lunar
eclipse happen?
Check with your instructor before continuing
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?
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
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