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Activity: Phases of the Moon
with Simulator

Introduction

Moon.Phases

In this activity you will use classroom materials, the NAAP Lunar Phase Simulator (http://astro.unl.edu/naap/lps/lps.html), and SkyView Café (http://www.skyviewcafe.com).

First, go to the NAAP site (see above) and read through the background materials they have provided. The materials are short, easy to read and very instructive. Next, work through the questions below using the simulators and SkyViewCafé.


Lunar Phase Simulator

Use the simulator to answer the following questions. The simulator shows the Earth/Moon system from above the North Pole. The Sun is off the screen to the left. In the upper right there is a pane showing the phase of the Moon that allows you to choose what phase you are looking at. In the lower right there is another pane (Horizon Diagram) that shows an observer in the Northern Hemisphere. In this pane you can watch how the Moon changes its location in the sky relative to the Sun through the cycle of its phases.

  1. For each of the phases listed in the table below write down how much of the face of the Moon is lit from the point of view from an observer on Earth. Use the Moon Phase box in the upper right of the simulator. Also, use the “show angle” option to find the Sun/Earth/Moon angle for each phase.
    Phase Angle Percent
    Lit
    Picture
    New
    Moon
         
    Waxing
    Crescent
    45° 14.6% Moon.Phase2.Wax.Cresc
    First
    Quarter
         
    Waxing
    Gibbous
         
    Full
    Moon
         
    Waning
    Gibbous
         
    Third
    Quarter
         
    Waning
    Crescent
         



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  1. The phrase the “dark side of the Moon” is often used by people who don’t really know what it means. Usually people think they mean that there is one side of the Moon that is always in the dark and never lit by the Sun. Use the simulator to determine whether there really is a “dark side of the Moon”. Explain what you find out in one or two sentences.
  2. Click the optional box marked “show lunar landmark”. Use the simulator to find out how long it takes for the Moon to rotate once on its axis relative to the Sun. You can measure this by watching the landmark. Start out with it pointing directly away from the Sun and drag the Moon through its cycle until it points exactly the same again. How long does it take? You can read off time elapsed in the Moon Phase pane.
  3. While you were working on answering the previous question you may have noticed something interesting. How long does it take for the Moon to cycle through all of the phases, from New Moon back to New Moon again?
  4. Use the simulator to find out why we on Earth can only ever see ½ of the Moon’s surface. Hint: Refer back to the previous two questions to help you. Explain what you find out in one or two sentences.
  5. If the “dark side of the Moon” has any meaning at all, what is it? Is the “dark side of the Moon” really dark?



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  1. Find the time of Sunrise-set and Moonrise-set for each phase. Turn on the “show time tickmarks” option. Set the exact phase of the Moon using the menu in the upper right. Then click on the stick figure on the Earth to change the time of day. You can put the Sun or Moon on the horizon in the Horizon Diagram to find the time each rises and sets. The time of day is given in the Horizon Diagram. Give times to the nearest hour or ½-hour.
    Phase Sunrise Sunset Moonrise Moonset
    New
    Moon
           
    Waxing
    Crescent
           
    First
    Quarter
           
    Waxing
    Gibbous
           
    Full
    Moon
           
    Waning
    Gibbous
           
    Third
    Quarter
           
    Waning
    Crescent
           
  2. Does Moonrise get later every day or earlier? The Moon orbits the Earth in the same direction as the Earth’s rotation. Use this information, and the simulator, to explain your answer to the question in one or two sentences.
  3. Use the simulator to find out whether the Full Moon is ever visible during daylight hours. Is it? Why or why not?
  4. Do Waxing phases (all the phases from New Moon to Full Moon) rise before or after the Sunrise on any given day? Use the simulator to find out.
  5. Do Waning phases (all the phases from Full Moon to New Moon) set before or after the Sunset on any given day? Use the simulator to find out.
  6. Is a Waning Crescent visible before Sunrise or in the evening just before Sunset? What direction should you look for it (East or West)?



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Moon Phases and the Horizon Diagram

Go back to the main page for the Lunar Phase Simulator. Now go to Moon Phases and the Horizon Diagram [swf]. Click at the top to Show Position Labels. Click at the bottom to show phase of moon on moon disc. Put the Sun and the Moon at position 1 by using the sliders in the Sun Settings and Moon Settings.

  1. When the Sun is at position one it is 6 am and the Sun is due East at sunrise. For each of the following Moon positions draw the phase of the Moon as you see it in the lower right-hand corner of the simulator. Also, label the phase. Finally, indicate whether the Moon is in the sky in the East, overhead, West, or below the horizon.





    Moon at 1
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 8
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 7
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 6
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 5
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 4
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 3
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 2
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon
  2. Use the slider to move the Sun to position 5. When the Sun is at position five it is 6 pm and the Sun is due West at sunset. For each of the following Moon positions draw the phase of the Moon as you see it in the lower right-hand corner of the simulator. Also, label the phase. Finally, indicate whether the Moon is in the sky in the East, overhead, West, or below the horizon.





    Moon at 5
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 4
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 3
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 2
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon








    Moon at 1
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 8
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 7
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 6
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon
  3. Use the slider to move the Sun to position 6. When the Sun is at position six it is 9 pm and the Sun is about 45° below the western horizon. For each of the following Moon positions draw the phase of the Moon as you see it in the lower right-hand corner of the simulator. Also, label the phase. Finally, indicate whether the Moon is in the sky in the East, overhead, West, or below the horizon.





    Moon at 6
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 5
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 4
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 3
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 2
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 1
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 8
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon





    Moon at 7
    ______________
    Phase
    Circle one:
    E           W
    overhead
    below horizon
  4. What phases of the Moon are always above the horizon at 6 am (sunrise)?
  5. What phases of the Moon are always above the horizon at 6 pm (sunset)?
  6. What phases of the Moon are always above the horizon at 9 pm?



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SkyViewCafé

Go to SkyViewCafé.com and start the interactive planetarium. Go to the Ecliptic tab (which shows the paths of the Sun, Moon and planets as if the Earth stood still). Be sure to click the box that says “Enlarge Sun/Moon”. Use the blue arrows at the top to go to the next New Moon. Note the location of the Sun and Moon. Now use the arrow buttons on the keyboard and the digits of the date/time box to move forward one day at a time. Keep going until you reach another New Moon.

  1. How long did it take to get the Moon back to its starting point?
  2. How long did it take to get to a second New Moon?
  3. What happened to the position of the Sun in the meantime while you cycled the Moon around through its phases?
  4. Why does the apparent position of the Sun move?
  5. The Moon orbits the Earth every 271/3 days as measured against the stars. The cycle of the Moon’s phases is longer than that: 29½ days. Use the information you gathered in answering the last few questions to explain why it takes longer to cycle through the phases than for the Moon to go once around the Earth.
  6. Use only your brain for this one: Sherlock Holmes interviewed the key witness in a murder trial. He found that the witness claimed to have recognized the perpetrator by the light of the Moon on the night of the murder. The witness said that she saw the murderer at 11 pm on the night of October 21, 2008. When you check your moon phase calendar you find that it was the night of the Third Quarter. Sherlock Holmes decided that the witness is hiding something and may even be a suspect herself. Why?
Moon Phases: Hand-held Simulator
Moon Phases: Introduction
Moon Phases: Rising and Setting
Moon Phases: Poster
Moon Poster Grading Rubric
Last updated: Nov 19, 2008        Home
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