Lesson Plan
Lesson Title / Phases of the Moon
Grade Level
State Indicator(s)
Goals and Objectives for Student Learning / By examining the geometry of the Sun, Earth and Moon with respect to one another, students will learn the cause of Moon phases. Drawing diagrams of the Sun-Earth-Moon system will help them understand how different Moon phases occur and when they are visible to us on the Earth.
Diversity
Teaching Method
Learning Activities / Science Introduction:
Despite appearing very bright at night, the Moon produces no visible light of its own. When we see the Moon “shining,” it is reflecting sunlight. Because of this, the Moon phase we see depends upon the configuration of the Earth, Moon, and Sun.
There are 8 phases of the Moon that proceed in a cycle. New Moon is when there is no moon visible from Earth. This occurs when the Moon and Sun are on the same side of the Earth. The side of the Moon that we can see from the Earth is not lit up by the Sun, and as the Moon does not make its own light, we on Earth are not able to see the Moon. In contrast, when the Moon and Sun are on opposite sides of the Earth, the lit side of the Moon is facing the Earth, and we observe a Full Moon. When the Moon phase is going from New to Full that is called “waxing,” i.e. the amount of visible Moon is increasing. From Full Moon to New Moon, the amount of visible Moon is decreasing, known as “waning.”
In between the New and Full Moons are six phases, three associated with waxing and three with waning. Moving from New to Full Moon, first a small sliver of the Moon is visible, known as a Waxing Crescent. If you imagine a line drawn between the Sun and Earth, for a Crescent phase the Moon is at a 45 degree angle with respect to this line. On Earth, we can only see a small sliver of the lit side. Following this is a First Quarter Moon. Here the Moon is at a 90 degree angle with respect to the Sun-Earth line. Observers on Earth can see half of the lit side of the Moon (i.e. one quarter of the Moon is bright). The last of the three waxing phases is the Waxing Gibbous. The Moon is at a 135 degree angle with respect to the Sun-Earth line. Thus, most of the lit side of the Moon is visible, except for a small sliver. After the Waxing Gibbous phase, we observe a Full Moon, where the Moon is on the opposite side of the Earth from the Sun.
After the Full Moon, the amount of illuminated Moon we observe from the Earth decreases, and we observe the waning phases. First is the Waning Gibbous. Similarly to the Waxing Gibbous, for this phases all but a sliver of the illuminated side of the Moon is visible from the Earth. Following this phase is the Last Quarter phase, where again, only half of the lit side of the Moon is visible. Lastly, we observe the Waning Crescent phase, where only a sliver of the illuminated side is visible from Earth. The amount of illuminated Moon that is visible decreases until, once again, the Moon is on the same side of the Earth as the Sun, and we observe a New Moon.
As the Moon phases depend on the Earth-Moon-Sun configuration, they are only observed at certain times. For example, for a New Moon, the Moon is on the same side of the Earth as the Sun. As the Earth rotates around its axis daily, the Sun and a New Moon appear to rise and set at the same time. Conversely, a Full Moon is opposite the Sun; when the Sun is setting, the Full Moon starts to rise. As the Full Moon sets, the Sun rises. As a final example of this, a First Quarter Moon begins to rise at noon, when the Sun is directly overhead. At sunset, the First Quarter Moon will be directly overhead, and it will set at midnight.
Procedure:
1)  Collect two balls on sticks (to represent the Earth and Moon) and a flashlight (to represent the Sun).
2)  Have a volunteer stand in the center and hold out the Earth ball in front of them, towards the class. Another volunteer will have the Moon ball, and a third holds the flashlight.
3)  With the flashlight off, have the volunteer with the Moon stand in between the Sun and Earth. The students should face the classroom having the balls sticking out away from them towards the class.
4)  Have the class predict what an observer on Earth would see as the Moon phase. Each student should use an Oreo cookie to make their prediction. Namely, the student should split the cookie apart so all of the filling is on one side. Then they can eat the appropriate amount of filling so the Oreo resembles the Moon phase they think the Earth-Moon-Sun configuration will result in.
5)  Turn on the flashlight, which is directed towards the Moon and Earth balls, demonstrating that the lit side of the Moon is not visible from the Earth, making it a New Moon.
6)  Continue to place the Moon and Earth in different configurations with one another, predicting what someone on Earth would see the Moon phase to be using the Oreos and confirming it with the flashlight.
Materials / 1)  One large styrafoam ball (Earth) and one medium styrafoam ball (Moon)
2)  Two sticks (insert into balls so students can hold them without covering the ball itself)
3)  Flashlight
4)  Oreo cookies (enough so each student has several cookies, one for each planned Earth-Moon-Sun configuration)
Supplements / In addition to a physical demonstration, drawing diagrams of the Earth-Moon-Sun configuration can be very helpful. A figure such as the one included above where students can determine the various phases are useful for cementing understanding. This diagram can also be used to determine when certain phases will be visible from the Earth. A worksheet asking questions such as when different phases rise and set can be solved using the diagram.
References / Lesson by Katie Schlesinger, The Ohio State University