material 2C: Face of the Moon
Intended Learning Outcomes
- Recognize data patterns.
- Revise models based on additional data
- 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
- Understand that the Moon rises in the
East and sets in the West because the Earth rotates in a counterclockwise
- 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)
and moonset data
- blank POM
charts (one per student)
Time Frame and Sequence
This material can be completed in one class
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 Earths 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
Student Ideas and Teaching Strategies
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 doesnt
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
- 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
- Still others may say that the Moon doesnt
set, but just "goes away" after a time.
- Students may suggest that the Moon is
always in the sky during the day, but we cant 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 Earths 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 Earths 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
Earths own rotation and the Moons orbit becomes difficult
to simulate when the orbital periods are so similar. Students realize
that in order for the Moons 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 TimeThe 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 1/28th
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.