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MUSE | Earth-Moon-Sun Dynamics | Course Overview and Materials | Building the EMS Model | Course Material 2B: Moonrise and Moonset | Instructional Notes

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INSTRUCTIONAL NOTES

• Recognize data patterns.
  
  
• Revise models based on additional data (model extension).
  
  
• Identify components of models.
  

• Use props to create or communicate models.

• Understand that the Moon rises later each day because the Moon revolves around the Earth in a counterclockwise direction.

• Understand that the Moon rises in the East and sets in the West because the Earth rotates in a counterclockwise direction.
  
  
• Understand that the Moon is in the sky for roughly 12 hours in a 24-hour period. Therefore, if the Moon rises at about 6PM, it will set at about 6AM.

Unless otherwise noted, you will need one of each item per group of students.

• Earth globes
• Moon spheres (Styrofoam balls or other balls to represent the Moon)
• moonrise and moonset data
• blank POM charts (one per student)

This material can be completed in one class period.

Begin by asking students to take about 10 minutes to complete the Moon phenomena pretest. After you have collected the pretests, you can discuss their answers to questions 7 and 8:

Many students have noticed that the Moon rises and sets due to their own daily Moon observations – but others will be unfamiliar with this phenomenon. Ask students whether they think the Moon rises and sets. Allow the students to talk with one another as a class and offer evidence from their own observations about this phenomenon. Once there is consensus about the fact that the Moon rises and sets, give each student group a copy of the Moon rise and set time data and ask them to find a pattern. After a few minutes, ask students to share their ideas about patterns in the Moon rise and set data.

Next, ask students (in their groups) to use globes, balls, their bodies, etc. to determine which celestial bodies and motions result in the phenomenon of Moon rise and set. They will need to explain several aspects of this phenomenon:

• Why does the Moon rise and set daily?
• In what direction does the Moon appear to rise and set and why?
• Why does the Moon rise approximately one hour later each day?

After approximately 15 minutes, ask one group to demonstrate their model. Initially, it is common for students to recognize that the counterclockwise rotation of the Earth creates the appearance of daily Moon rise and set similar to Sun rise and set. You may want to make this connection with students if they do not address it in class. However, many will not yet be able to account for the pattern in moonrise times. Allow the student groups to continue to work on this aspect of the model and ask students to share their ideas when it seems appropriate.

When 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 (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 out these flaws through questioning or encourage the other students to do so whenever possible.

It is entirely possible that your students will develop more than one model to account for the pattern of Moon rise and set data. 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 additional phenomena. Ultimately, your students will develop a model consistent with current scientific thinking 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.

Also, you will probably 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 depending upon which phenomenon one is attempting to explain.)

By the end of the Moon rise/set modeling day, students should have a model to explain Moon rise and set phenomena and also have realized (again, facilitated by your questioning) that all celestial objects appear, from an Earth perspective, to move at least in part because of the Earth’s own rotation.

Ask students to complete a POM chart to describe their model for Moon rise and set for homework. If class time remains, encourage students to begin this task in their small groups.

Moon Rise and Set – general

From our analysis of students’ pretests, we have noted the following:

• Some students think that the Moon is always in the same place in relation to the Earth. While this idea is consistent with the Moon rising and setting, it is not consistent with the observation that the Moon rises and sets about one hour later each day.
  
  
• Some students may say that the Moon doesn’t actually rise and set, but only appears to do so because the Earth rotates. You may want to probe this idea further during a class discussion to find out exactly what they mean by "appears" to rise and set and why they think this way. Take some time to discuss the importance of perspective in determining what one observes and the need for a conventional way of speaking about observations throughout this course. Generally, when we describe the motions of celestial bodies in this course, we assume an Earth perspective or we stipulate a space perspective.
  
  
• Some students may know that the Moon rises and sets, but have no idea why. They have seen the Moon appear above the Eastern horizon and then sink below the opposite horizon. Working with the props during this modeling session will help them understand the "why."
  
  
• Still others may say that the Moon doesn’t set, but just "goes away" after a time.
  
  
• Students may suggest that the Moon is always in the sky during the day, but we can’t see it because it is too bright outside. Thus, the Moon is never beyond the horizon to rise and set. Again, their own Moon observation data will help provide dissatisfaction with this alternative conception since many students should have seen the Moon visible in the daylight hours by this time in the unit. Emphasize the regularity with which they can see the Moon during the day. If students have not seen this yet, you may instruct them to look for the Moon at a certain time during daylight hours when you know it will be visible (waning phases). If this is not possible because of a full Moon, find a picture where the Moon is visible during the day. There is a difference, however, between saying that the moon is sometimes "there" and sometimes not and to say that it rises and sets. You may want to ask students if they have seen moonrise and moonset firsthand to establish the idea that there is an actual moonrise and moonset. Again, a picture or video of a moonrise or moonset may help if firsthand data is not available.
  
  
• At the outset of this material, some students already understand the current scientific explanation for Moon rise and set. Similar to Sun rise and set, the Earth’s rotation causes the Moon to appear to rise and set. For approximately 12 hours, the Moon is visible on the other side of the world and for 12 hours it is on "our side" of the world.

• Finally, some students think that moonrise and moonset happen only because the Moon orbits the Earth. They do not think that the Earth’s rotation contributes to this phenomenon. There are at least two possible lines of questioning to assist students in identifying the limitations of this idea: (1) Ask these students to look back at their Moon observation data and determine how long it takes for the Moon to go from a new phase to another new phase (one complete cycle). Most will know that this takes about a month. If they also connect this cycle of Moon phases with its Earth orbit, they will realize that rather than taking one day, the Moon takes one month to complete an orbit. Thus, their explanation of Moon rise and set is inconsistent with their observations of phases. (2) If your students do not yet make the connection between cycles of phases and Moon orbit (which is perfectly fine, since this material has not yet been covered), you can challenge their model by asking how they can account for the fact that the Moon rises consistently later each night. Ask them to use props to account for this phenomenon using their model. This task generally produces some dissatisfaction with their own model because the combination of Earth’s own rotation and the Moon’s orbit becomes difficult to simulate when the orbital periods are so similar. Students realize that in order for the Moon’s orbit to produce the rise/set phenomenon, the Moon must be orbiting Earth faster than Earth rotates. Moreover, if this were the case, people on Earth would occasionally see more than one moonrise during a given 24-hour period.

Moon Rise Time–The One Hour Delay

Students suggest various explanations for the pattern in moonrise and set times:

• Some will say that it is because the Moon orbits the Earth in the same direction that the Earth rotates (counterclockwise), but much slower, a correct response. Since it takes approximately 28 days for the Moon to orbit the Earth, the Moon travels 1/28^th of the way around the Earth each day, making it appear in our sky, over the Eastern horizon, about an hour later.

• Some students have the idea that the Moon revolves in the same direction that the Earth rotates, but cannot relate this to why the Moon rises and sets an hour later each day. Encouraging students to use props and asking them to think about what we would observe if the Moon orbited clockwise (opposite the spin of the Earth) versus counterclockwise is helpful in this instance.
  
  
• Another idea is that Moon rise and set have "something" to do with the tilt of the Earth. To address this misconception, ask the student to explain further. He most likely will say that day length changes some each day. By further exploring this idea, you should be able to help students see that day length changes only slightly from day to day, only a few minutes at most, where the Moon rise and Moon set times vary almost an hour each day.

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