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MUSE | Earth-Moon-Sun Dynamics | Course Overview and Materials | Building the EMS Model | Course Material 2D: Phases of the Moon | Instructional Notes


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Instructional Notes

Intended Learning Outcomes
  • Use classroom norms in small and large group work.

  • Organize data.

  • Use props to create or communicate models.

  • Recognize data patterns.

  • Identify components of models.

  • Use models to account for phenomena.

  • Assess models for data fit and consistency.

  • Use models to predict.

  • Alter component of model and predict (cause to effect reasoning).

  • Understand that every 28 days we see a complete cycle of Moon phases: new Moon, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, third/last quarter, waning crescent.

  • Understand that the Moon changes in appearance gradually each night.

  • Understand that phases are caused by the relative position of the Moon with respect to the Earth and Sun.

  • Understand that the Moon’s relative position changes as it revolves around the Earth.

  • Understand that ‘waxing’ means increasing in size. A waxing Moon phase appears lit on the right side.

  • Understand that ‘waning’ means decreasing in size. A waning Moon phase appears lit on the left side.

  • Understand that one half of the Moon is always facing the Sun and therefore one half of the Moon is always lit.

  • Understand that the Moon is in the sky for approximately 12 hours within a 24–hour period. Therefore, if the full Moon rises at approximately 6pm, it will set at approximately 6am.

  • Understand that the full Moon rises at sunset and the new Moon rises at sunrise. Based on the position of the Moon in its orbit around the Earth, it is possible to determine the approximate rise and set time of each Moon phase.

  • Moon spheres (one/group)
  • Light source (one/classroom)
  • Earth globes (one/group)

Time Frame and Sequence

This material will take about 5-6 days to complete. It starts with a review of students’ prior knowledge of Moon phases and continues as students extend the explanatory power of their EMS model to account for the Moon phase observations that they have been gathering since the beginning of the unit.

Day 1 – Students’ Prior Knowledge

Students took a Moon phenomena pre-test about the same face of the Moon and Moon phases before starting Material 2B: Moon Rise and Set. Now would be an appropriate time for you to review your students’ responses to the Moon phase portion of this pre-test in order to refresh yourself and your students about their ideas on this topic.

Naming Moon Phases

Students will be familiar with the various shapes of the Moon from the data they have been gathering about the Moon’s phases, but will likely not have heard all the names of the phases. Discuss with students how to correctly recognize and name the Moon’s phases. List the names of the eight major Moon phases on the board along with an accompanying picture of each (full Moon, new Moon, waxing crescent, waning crescent, waxing gibbous, waning gibbous, first quarter, last/third quarter) and ask students to put them in an order that makes sense to them. This can be done by individual students or in small groups. Next, have a few students share their sequence and justification with the class. Give students a sheet with the eight major Moon phases pictured in sequence and ask students to label them. Once complete, this sheet can serve as an organized study aid to help students learn how to recognize and name Moon phases. Before moving on, discuss and confirm the names associated with each of the 8 phases.

Simulating Phases

students in classroom with model Now that students have identified a pattern in their Moon phase data, they are ready to use their EMS model to account for this pattern. For the remainder of the class, students should work in small groups to simulate the pattern of Moon phases using a light source to represent the Sun and a Styrofoam ball to represent the Moon. Students’ heads should represent the Earth in this simulation.

Darken the room and turn on one bright light bulb (the Sun). Each group should have one Styrofoam ball (Moon). Tell students to stick this ball onto the end of a pencil so that they can simulate its motion around themselves (the Earth) more easily (also note that having the ball on a pencil encourages the students to hold the ball up and out of the plane of the ‘Earth/Sun’, thus avoiding simulation of lunar eclipses during this demonstration). Now ask students to simulate, or recreate, the motion of the relevant bodies such that they result in the expected pattern of Moon phases. They will have to decide whether or not Earth’s motions (rotation and revolution) are important, the direction in which to move the Moon, etc. during this simulation. When they place themselves (the Earth) next to the light source and simulate the Moon’s orbit, they will observe the Styrofoam ball going through phases analogous to those of the Moon. That is, when the ‘Moon’ is directly between themselves and the light source, they will see an entirely dark disk (new Moon). When their own bodies are directly between the ‘Sun’ and the ‘Moon’, they will observe an entirely light disk (full Moon), provided the Moon ball is not in the same plane as their bodies and the light source, etc. Different Moon phases will be apparent on the Styrofoam ball as it changes its position relative to the ‘Earth’ and ‘Sun’.

Once students observe the ‘Moon’ changing phase in this simulation, they should think more about the phenomenon and determine which bodies (and which of their motions) are important to account for the pattern they noted in their actual Moon observation data. After talking through their ideas, student groups should be ready to complete a Moon phase POM. It is important that the students share their ideas with their partners first before trying to structure them using the POM. Students will probably have time to begin their POM as a small group but will need to complete it for homework. Students should also be prepared for a Moon phase identification quiz tomorrow.

Day 2 – Identification of Phases: Quiz

Start class with a Moon phase identification quiz which should take about 10 minutes. On the quiz, students identify the phases that correspond to various Moon diagrams and also draw diagrams that correspond to particular phase names.

Using the EMS Model: Explaining Phases

After the quiz, ask students (in small groups) to take out the Moon Phase POMs that they completed for homework and discuss how their models account for the phenomenon of Moon phases. Next, reconvene as a whole class and have one group share its model with everyone. After hearing this group’s ideas, allow time for groups with other models to share those as well. The likely outcome of this discussion will be agreement by the class on a single model to account for the phenomenon of Moon phases. This class model will probably include:

  • the Earth, Moon, and Sun.
  • the Moon’s orbit around the Earth (in a counterclockwise direction once approximately every 28 days).

Representing How the EMS Model Accounts for Phases

Next, the class should decide how to represent their model. Ask students to individually diagram the components of their model to account for the four major Moon phases (new, full, first quarter and last/third quarter). After about 10 minutes, ask a few (3-4) students to share their diagrams with the class by drawing them on the board. It is helpful to have within this group examples of diagrams from an Earth perspective as well as from a space perspective. Have one student explain his/her diagram to the class and have others do the same if their diagrams and justifications differ from those of the first student. Even though most, if not all, students will have the same model to account for phases, their diagrams will likely vary considerably in terms of the perspective selected, motions represented, labeling conventions, etc. Sample student diagrams are provided in the student work examples section.

Next, hand out a Phases of the Moon diagram template to each student. This tool is designed to help students realize their options about how to represent their model and will also help them come to a consensus about their representation. Discuss the need for such a common representation with your students and emphasize the importance of everyone understanding the diagram and how it can be used to represent the phenomenon of Moon phases. Together as a class, create a convention that will allow you to represent the Moon phases from both a space and an Earth perspective on the same diagram. This will involve taking parts from each type of diagram and combining them into one. The final diagram should show that half of the Moon is always lit by the Sun and the portion of the illuminated half that we can see from Earth varies according to the relative positions of the Moon, Earth, and Sun. A sample student diagram is pictured in the student work section for this material. Give students time to finish this diagram in their small groups by adding the remaining phases — waxing and waning crescent and waxing and waning gibbous — to the diagram. Have students modify the diagram on their Moon phase POM for homework tonight.

Day 3 – Moon Phase POM

Yesterday the class should have reached some consensus about the objects and motions in the EMS model that were important for explaining phases. Also, they should have decided on a convention for diagramming Moon phases such that the Moon's appearance from the perspective of the Earth and from space can be represented in a single diagram. You might choose to begin class today by reviewing the students' POMs to make sure the necessary elements of the EMS model are included and that their diagrams conform to the conventions the class has established.

Extension Questions

The remainder of the class can be spent with the students in small groups grappling with the Moon phase extension questions. Students should complete their explanations for these questions for homework.

Day 4 –Extension Questions

Start class by allowing students about 10 minutes to converse in their small groups about their ideas about the Moon phase extension questions. Encourage students to discuss each question using props (as time allows) and to revise their answers as a result of their discussion.

Bring students together as a large group for continued discussion and demonstration of each of the extension questions. Ask different students to demonstrate and discuss how they came up with their understanding of each scenario. Also, ask for competing explanations from other students for each question.

Quiz Preparation

If time remains, involve students in any additional preparation for the Moon phase quiz tomorrow.

Day 5 – Quiz

Start class with a Moon phase quiz. Students should have access to props as needed. Plan for the quiz to take about 25 minutes.

EMS Model Summary

Although the students' EMS model is not yet complete, it is already quite complex and can account for a number of phenomena. Thus, it is a good time to step back as a class and review the objects and motions that the model includes as well as the phenomena it can explain. The EMS Model Summary sheet will assist students with this task. You may want to get students started on this summary by demonstrating how you would like to use the sheet for one phenomenon; perhaps day and night. Then discuss as needed how you want students to continue to summarize their EMS model using this sheet. There is not one best way to use this summary sheet, but rather many effective options. It is recommended that you give students some time to reflect on the comprehensive nature of their EMS model and make some progress on completing the summary sheet in small groups for about 15 minutes. Students should complete the EMS model summary sheet for tomorrow.


Hand out and explain the self–assessment sheet to each student. In addition to taking time at this juncture of the unit for students to assess their EMS model, it is also a good time to give students an opportunity to assess their working relationship skills. Students should complete this self–assessment for homework.

Day 6 – EMS Model Summary

Start class today by compiling individual student EMS model summary ideas into a class summary. Lead a class discussion to complete one overall version of the EMS model summary sheet (see the sample in the student work section). This will likely take ~15–20 minutes.

Student Ideas and Teaching Strategies

Day 1 – Sequence of Moon Phases

When putting the Moon phases in order, most students will start with the new Moon and proceed from there. Many will have difficulty determining whether the Moon is then gradually lit on the right side (waxing) or the left side (waning). Remind students that they have already observed a cycle of Moon phases and they should consult their data to make this determination. Assist students as they learn the names of phases and how to associate names with specific Moon phases by sharing any hints you can. For example, the phrase ‘wax build-up’ can be helpful when learning that waxing means getting bigger. ‘Waning’ is a term that is not unique to Moon phases, thus using it in other contexts such as, "during my lectures your attention seems to wane" can sometimes be helpful for students.

Modeling Phases

  • When students begin simulating the Moon’s phases using the light source and Styrofoam ball, remind them to simulate the cycle of phases that they have already observed: that is, they should be recreating motions that result in the 'Moon' appearing new, waxing (lit on the right), full, waning (lit on the left) – in that order.
  • Having students represent phases works best if the light source is suspended from the classroom ceiling in the middle of the room so students will not have to work in shadows created by other students working closer to the light. This enables students to use the entire classroom as a work space as well. You should have only one light source in the room and the room should be as dark as possible. If the light is lower (rather than on the ceiling) the students’ heads (representing Earth) and the Styrofoam ball (representing the Moon) will sometimes be in the same plane. Thus, when the 'Moon' should appear full, it will tend to fall in the shadow created by the 'Earth' and this arrangement ('Earth' directly between the 'Sun' and 'Moon') will result in a lunar eclipse rather than a full Moon. Suspending the light source higher in the classroom will help eliminate this complication.
  • Whenever students share their models, try to provide opportunities for them to discuss competing or incomplete ideas in addition to models that are consistent with the scientifically acceptable explanations. Your role during these discussions is to ask questions that require students to clarify and defend their ideas. You should avoid telling students that certain models are correct and others incorrect. Rather, when students present an idea that does explain all of their data, you can ask the rest of the class whether they agree with the model. If so, why? If not, why not? Remind students that they should be judging models based upon the three criteria established during the Black Box material (1D): explanatory adequacy, predictive power, and consistency. When students propose models that are unable to account for all the observations or that are inconsistent with other ideas, point these out through questioning or encourage the other students to do so whenever possible.
  • It is possible that your students will develop more than one model (or models of varying "completeness") to account for the phenomenon of Moon phases. As long as these models are consistent with accepted knowledge (what your students know so far) and can explain the observations at hand, this is OK. As the EMS unit progresses, the students will become familiar with more phenomena. Those who develop alternative models early on will become dissatisfied with those models as they attempt to use or modify them to account for these additional phenomena. Ultimately, your students will develop a model consistent with current scientific opinion as they attempt to account for more and more natural phenomena. Allowing them to develop dissatisfaction with early models at their own pace is an important aspect of success in this curriculum.
  • You may need to remind your students, through questioning, that they are not constructing individual models to account for new phenomena, but elaborating their existing EMS model by adding objects or specifying additional motions. In this way you can reinforce the need to examine consistency among ideas and the notion that powerful scientific models can account for a wide variety of phenomena. Moreover, you can eliminate the possibility that students will develop ad hoc variations in their models when faced with different phenomena. (For example, the students will have to accept that it takes the Moon roughly 28 days to orbit the Earth – and this period cannot vary no matter which phenomenon one is attempting to explain.)

Day 2 – Representing Moon Phases

  • It is likely that some students will diagram their model from an Earth perspective and others from a space perspective. Have some of each represented on the board for consideration. It is recommended that as a class you use a convention that will incorporate both perspectives into the diagram.
  • When making the combined perspective diagram, either on the board or on an overhead transparency of the Phases of the Moon diagram template, solicit student input to help you draw the four major Moon phases and label them accordingly based on their relative positions with respect to the Earth and Sun. Divide each Moon in half using a solid line and shade each to emphasize which half is lit by the Sun as seen from space (all four Moons will look the same at this point). Next add information to the diagram indicating the counterclockwise direction of the Moon’s orbit around the Earth. Now add another line, dotted this time, to represent the horizon of a person viewing each Moon phase at the point when it is highest in the sky. Note that some portion of the Moon that faces the Earth (indicated by the dashed line) will appear lit and some shaded (other than for new and full phases) due to the initial shading you did to indicate which half of the Moon was lit from a space perspective. The final diagram you create to represent both a space and an Earth perspective of the Moon’s phases will contain multiple pieces and it is fairly complicated to explain in the abstract (see image below).

moon phase model


  • When shading Moon phases to emphasize illumination by the Sun, follow the convention that shaded means 'not lit' and unshaded (white) means 'lit'.
  • On the diagram, it is difficult for students to see the difference between the first and third/last quarter Moon phases unless they observe from an Earth perspective. Students should turn their diagrams to show the Sun on the appropriate side of the Moon to light it as represented on the diagram. Encourage students to do this so they can see both quarter phases and how they are represented.

Day 3 – Moon Phase POM

In the motions section of the POM, some students will likely want to include the fact that the Earth rotates along with the fact that the Moon orbits the Earth. Discussing the implications of a non-rotating Earth on the Moon’s phases will yield some interesting points. Students are likely to see that the Earth’s rotation does not affect the Moon’s phases, but it does impact which Moon phases one sees from a given vantage point on the Earth. In general it is recommended that you have a stack of blank POMs available for your students throughout this unit and encourage them to use and keep many iterations of their ideas rather than thinking that the POM is just the place to write their final idea. This should help emphasize the processes along with the products of science.

Extension Questions

The extension questions emphasize a number of main points about the phenomenon of Moon phases. Some questions ask students to modify the conditions under which their model exists, ie: make the Moon spin twice as fast and discuss the implications of this on the Moon’s phases. Other questions ask students to apply their Moon phase knowledge in the same situations they have been working ie: How much of the Moon is lit on any given day? These extension questions are meant to provide students with scenarios that allow them to work with their EMS model and modify its components and then determine the outcomes (cause to effect reasoning). As a result of tackling the extension questions, students will likely be much more comfortable manipulating their model and have a greater appreciation for its explanatory and predictive power.

Day 4 – Extension Questions

  • When students are conversing at the beginning of class about their extension questions, ask each group to start with a different question. This will ensure that at least some groups will have had time to deal with each question to make sharing in the whole class setting more comprehensive.
  • During a discussion like this, remember to stress which objects and motions are relevant to account for a particular phenomenon and the need to focus on whether or not they are modified in each extension question scenario. Also remind students about the model assessment strategies they learned in the black box material (1D) and encourage them to assess models based on their explanatory power, consistency with other information students have about the way the world works, etc.
  • Encourage students to modify their answers to the extension questions as a result of this day’s discussions/demonstrations.

Day 5 – Moon Phase Quiz

It is recommended that quiz conditions match student learning conditions as much as possible. Suggestions for this include giving students access to props as needed and making this choice as likely for students as possible (minimize the classroom norms that exist against students getting up during the quiz etc.). You may also consider giving each student the opportunity to converse with another student and allow them to make any changes before handing in their quizzes. It is easiest if students team up for this as they finish. You do not necessarily need to announce beforehand that you will provide this option. It is often exciting to hear what students talk about during this time and it is usually just what you would hope to hear in such a discussion.

EMS Model Summary

There are a variety of ways to organize the summary sheet and you may want to establish one convention for the whole class to follow or you may prefer to allow student groups to each develop and use their own convention.

Day 6 – EMS Model Summary

It is recommended that you post an enlarged copy of the EMS model summary your class created today. This can serve as a reference and will likely be very helpful as you continue to expand the model to account next for eclipse phenomena and later the phenomenon of seasons.


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