student work examples
Intended Learning Outcomes
Time Frame and Sequence
Completion of this material usually requires only 1 class period. The objective is for students to recognize that only one side of the Moon is visible from Earth and the same side is always visible regardless of the observer's position on Earth. Students will modify their EMS model to account for this phenomenon by adding a motion: the Moon's rotation (or spin) on its axis.
Day 1: Moon Face
Begin class by displaying several pictures of the Moon in its full phase. Include labels that identify both the location and date for each picture. Make sure that your picture set includes photographs taken from each hemisphere and both Eastern and Western continents. You should also vary the time of year during which each picture was taken. Ask the students to look closely at the pictures and note any patterns that they see. Write down their comments on the board. After you've generated this list of patterns, focus the students' attention on the fact that the Moon face is always the same, regardless of where or when you look at it from Earth. Tell the students that they will spend the rest of the period modifying their EMS model to account for this new phenomenon.
Ask students to work in their small research groups to modify their EMS model in order to account for why we always see the same face of the Moon. After about 15 minutes, ask for volunteers to share their models. At this point, there are often two competing models:
While students are discussing these tentative models, use the board to keep track of their different ideas. After the initial discussion, ask students what they can agree upon thus far. Generally, they will agree that the objects involved in explaining this phenomenon are the Earth, Moon, and Sun. Write the following on the board:
Next, summarize where there is still disagreement. Usually the students have not come to consensus about whether or not the Moon spins on it axis. Write the following on the board:
Now have the students return to their small groups and attempt to test these alternative ideas and refine their EMS model. Thus, the students will spend the rest of class focusing on identifying the specific motions involved in this phenomenon. Because it is frequently difficult for students to discern slow movement from no movement, you can suggest strategies for them to simulate these motions. In particular, we have found it helpful for the students to use their own bodies, rather than the Moon balls and globes, as they attempt to recreate the Moon face phenomenon through motion. As the groups work, circulate among them and ask students to demonstrate the phenomenon for you. Help them to distinguish between scenarios where they are spinning very slowly versus not at all (more is said about this in the Student Ideas & Teaching Strategies section below).
After about 15 more minutes, ask the groups to demonstrate their models to the class and hand each student a blank Moon Face POM to complete for homework.
Day 2: Review POM
Begin the second day by spending just a few minutes reviewing the modified EMS model and the Moon Face POM, then begin Material 2D: Moon Phases.
Student Ideas and Teaching Strategies
The purpose of showing the students pictures of the Moon taken at different Earth locations and different times of the year is to help them recognize a general pattern: that the Moon's craters are always in the same place from our perspective. Thus, we always see the same face of the Moon regardless of our vantage point on Earth. A variety of pictures will enable students to see that the same Moon face is visible
Moreover, if you are able to do so, obtain a few pictures of waxing gibbous Moons as well. The waxing gibbous Moon is full enough to see many of the craters (and thus to compare easily with the full Moon) and is also visible during daylight hours (from about 3 PM until about 3 AM). Thus, these pictures can provide evidence that the same Moon face is also visible at different times of the day.
When you show the students the Moon pictures, remind them that the first thing they did with the Black Box data (in Material 1D) was to identify a pattern. Similarly, they will be seeking a pattern in these Moon photographs. Keep a written record of students' ideas about patterns on the blackboard. Our students have noticed the following patterns in the Moon picture data:
Occasionally, it has been difficult for students to notice the craters. You might prompt them to pay attention to this feature by asking, "Are these all pictures of Earth's Moon? How do you know?" or "Do you think some of these pictures might be of Mars' Moon?" These and other similar questions focus students' attention on the similarities between the pictures rather than their differences. Conclude the discussion by explicitly inferring from the shadow pattern that we are always seeing the same face of the Moon from Earth.
Generally, students readily agree that the objects involved in this phenomenon are the Earth, Moon, and Sun. They struggle to identify the specific motions that give rise to the phenomenon, however. After the initial group modeling work, our students are usually in the process of testing one of three explanatory models:
When students present their initial models, keep in mind the criteria for judging explanatory models in science. On this basis alone, the first model above is easily dismissed: the students' own work in Material 2B: Moon Rise & Set demonstrated that the Moon orbits Earth in the same direction as Earth's rotation. Thus, this model is inconsistent with accepted ideas (their EMS model thus far) and must be rejected.
Judging between the other potential models is usually more complicated due to two factors: First, our students have difficulty distinguishing between an object that is very slowly spinning (rotating) and one that is not spinning at all. Second, our students have difficulty learning (and consistently using) the terms 'spin,' 'rotate,' 'orbit,' and 'revolve.' Thus, they frequently have difficulty understanding one another during discussions of their EMS models.