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I'M BEING FOLLOWED BY A MOONSHADOW
Grades 3 - 8

Overview

Since mankind has been observing the heavens, eclipses have inspired great awe and fear among peoples of all cultures. Dragons, wolves, jaguars, even angry gods have all shared the blame for the consumption of the Sun and Moon. Throughout history, some cunning people have used eclipses to their advantage by capitalizing on the fear and confusion of their adversaries. Lawrence of Arabia led a handful of raiders against two heavily fortified Arab outposts and captured them without any casualties because the Arabs were preoccupied with banging pots and firing their guns into the air to frighten off the demons who were consuming the moon. Columbus, on his fourth voyage to the New World, lost his ships to wormrot, had half of his crew mutiny and was without supplies, with relief months away. The crew that had mutinied was terrorizing the natives and plundering their supplies. The natives were therefore in no mood to supply Columbus and his faithful men. Columbus knew of an impending lunar eclipse and used this knowledge to scare the natives into supplying his men. Needless to say, he was well- provided for until his rescue.

Eclipses of the Sun and Moon were objects of great fear because they weren't understood. It was the ancient Greeks who first surmised that the Earth was round because of the curved shadow on the Moon during lunar eclipses. The Greeks were also among the first to put forth the hypothesis that the Earth went around the Sun, and the Moon went around the Earth. As the centuries passed, scientists began to understand eclipses and make models to explain them. It is now known that eclipses occur when there is an alignment of the Sun, Earth and Moon. When the Earth is positioned between the Sun and Moon, and the Moon is full, a lunar eclipse can occur. Since the Earth is much larger than the Moon, the entire moon is eclipsed. When the Moon is in its new phase, located between the Sun and Earth, a solar eclipse can happen. Since the Moon is much smaller than the Earth, the Moon's shadow affects only a small strip of the Earth during a solar eclipse. Solar eclipses happen because of an astronomical fluke of nature. Although the Sun is about four hundred times the diameter of the Moon, the Moon appears to be the same size as the Sun because it is about four hundred times closer to the Earth. If solar eclipses happen at the Moon's new phase, and solar eclipses at the full phase, one would wonder why they don't occur every month. This is because the plane of the Moon's orbit is tilted at an angle of about five degrees to the Sun-Earth plane, enough of a tilt to cause the Earth and Moon to miss each other's shadows most of the time.

In this lesson, students will learn the relationships among the Sun, Earth and Moon that cause solar and lunar eclipses and create models to demonstrate them. This is to be part of a unit on the Solar System and prior knowledge of the Earth-Moon system is required. This prior knowledge should include tidal forces, phases of the Moon, why we always see the same side of the Moon, and the concepts of revolution and rotation.
ITV Series
Earth, the Environment and Beyond, #9: Moon Conquest
Nova, July 11, 1991: Solar Eclipse
Learning Objectives
Students will be able to:

Materials
For the previewing activity:
For the class:

For each student:

For the postviewing activity
For each group of 4 students:

For the teacher: (These items are for making holes 45" apart in the wooden stick above for the
toothpick and the golf tee to sit in. Do this before starting the lesson plan.)

Pre-Viewing Activities
Tell the students that they are about to create a model of the Sun-Earth-Moon system, and demonstrate the phases of the Moon as well as solar and lunar eclipses. Prepare the room for this demonstration by darkening it as best you can. The darker you can get it, the better. Explain to the students that in this model, the Sun will be represented by a lamp without a shade located in the center of the room (be sure to tell students not to look into the light for prolonged periods); the Earth will be their heads with their eyes being the location of the observers; and the Moon will be the styrofoam ball placed on the end of a pencil. Explain to the students that this model is not to scale.

Pass out a pencil (preferably sharpened) and a foam ball to each student. Have them place the ball on the pencil. Instruct the students to stand throughout the perimeter of the room with their backs to the wall and at least an arm's length from their neighbors on either side of them and from the wall. Move among the class making sure the students understand that the Moon travels from west to east as it orbits the Earth, and that the Earth orbits the Sun in the same direction. In our demonstration here, this west to east motion is modeled by the students moving the Moon in a counterclockwise direction around their bodies.

Inform the students that they will be modeling the phases of the Moon first. This should be a review exercise at this point. Have the students hold their spheres in their left hands and at arm's length in front of them and just below the light while they are facing the light source.

Ask, What phase of the Moon are you observing now? (They are observing the new Moon, where the unlit half of the Moon is facing the Earth.)

Keeping their arm's straight in front of them, if they move their bodies slightly counterclockwise, they will see a thin crescent appear on their spheres.

Ask, What do you see on your spheres? What phase does this represent? (They should see a crescent of light which represents, of course, the crescent phase. There are two sets of crescent Moons during each month, one just after the new Moon and one just before the new Moon. All phases between the new and full Moons are known as waxing phases, because they are in the process of showing more and more of the Moon's surface. All phases between the full and new Moons are known as waning phases, because they are showing less and less of the Moon's surface to observers on Earth. During the waxing phases, the lighted part of the Moon grows from the right side to the left side. During the waning phases, the dark part of the Moon is growing from the right side towards the left, also. Therefore, at this time the students are modeling a waxing crescent phase of the Moon.)


Have the students turn their bodies so that they are facing the student to their left.

Solicit a description of the phase being modeled here. Some people mistakenly call it a half moon, because half of the surface of the Moon facing us is lit up. The correct name for this phase is the first quarter Moon, so named because the Moon is now one quarter of the way in its orbit around the Earth.

Have the students turn a little more towards the wall but not quite facing it yet. Students should describe this phase as a gibbous Moon. As with the crescent phase, there are two times in a month where a gibbous Moon can happen; just before and just after the full Moon. At this time, a waxing gibbous Moon is being demonstrated.

Direct the students to now face the wall behind them with the sphere slightly above the shadow of their head. Even the most novice sky watchers will have little difficulty identifying this phase as the full Moon. The Moon is now in its second quarter, or half moon phase, as it is now half way through its orbit around the Earth.

At this point, tell the students to switch the hand that is holding the pencil to their right hands, before they continue.

Turning slightly away from the wall, still in a counterclockwise direction, the students will be modeling a waning gibbous phase.

When the students turn until they are facing their neighbors to their right, they will observe a third quarter Moon. The Moon is now three quarters of its way around the Earth.

Another turn of their bodies almost, but not quite, facing the light again, they will see the waning crescent phase.

Finally, facing the light once more with their spheres slightly below the light brings them full circle through the monthly cycle of the phases of the Moon.

Having the students hold the spheres slightly below the light source at the new Moon phase and slightly above the shadow of their head at the full Moon phase, illustrates the tilt of the Moon's orbit in relation to the Earth's orbit about the Sun (it could also have been demonstrated with the sphere above the light source and below the shadow of the head, but the shadow of the rest of their bodies would be in the way). This shows why we don't experience a solar eclipse at every new Moon and a lunar eclipse at every full Moon.

Tell the students they will now demonstrate a solar and lunar eclipse.

Ask, At what phase of the Moon can a solar eclipse happen? (Students should respond that a solar eclipse can only occur during the new Moon phase.)

Have the students hold their spheres out in front of them again, only this time have them block the light bulb with them. They are now modeling a solar eclipse because the "Moon" (sphere) is now located between the "Sun" (light) and the "Earth" (their head). Instruct the students to look at the person across from them and describe the shadow being cast on that person's head. They should notice that the entire head is not in shadow, but only a small portion of it is. This is similar to the effect the real Moon's shadow has on the Earth during a solar eclipse. Students can experiment with moving the shadows around on their faces for their classmates to see by moving the sphere in front of the light, side to side and up and down. If the sphere only grazes the light, this represents a partial eclipse, which can, and does, happen. There is also one more kind of solar eclipse to mention here, the annular eclipse. Annular eclipses occur when the Moon is furthest away from the Earth in its orbit and therefore appears too small to the observer on Earth to cover the entire Sun, leaving a ring of light around the dark disk of the Moon.

Once you are comfortable that the students have mastered the concept of the solar eclipse, ask, who can explain how we can model a lunar eclipse? Students should respond by demonstrating with their backs to the light source, passing the sphere through the shadow of their heads. Have each student repeat this exercise.

Ask students for their observations on the shadows being cast on the spheres. They should note that in contrast to the Moon's shadow on the Earth during the solar eclipse, the entire Moon is engulfed in the Earth's shadow during a lunar eclipse.

However, just as there are partial solar eclipses, there are also partial lunar eclipses. These can be modeled by passing the sphere along the outside edge of the shadows of their heads so as not to cover the entire sphere in darkness.

After allowing some time for the students to "mess around" with the shadows again, prepare them for watching two video clips; one for each type of eclipse.
Focus Viewing
To give the students a specific responsibility while viewing, ask them to be on the lookout for: Why we always see the same side of the Moon? What effect the Moon's phases have on people? Who first thought the Earth was round and why? What effects the Moon has on the Earth besides causing the tides? What is the corona? Why do we see the corona only during solar eclipses? Why the Moon appears to be the same size as the Sun to us here on Earth?

Have these items posted on newsprint or the chalkboard and have the students copy them on a piece of paper on which to jot notes. Have them diagram the two kinds of eclipses and write a brief description of them.
Viewing Activities
Tape #1, Earth, The Environment and Beyond, #9: Moon Conquest

START the video after the clip of the silent movie depicting people landing on the Moon, where the narrator states, "Scientists have known for thousands of years that the Moon is the nearest celestial body to the Earth."

PAUSE and ask "What is a celestial body?" (Celestial means "among the stars" so a celestial body is something in space.) Before continuing video, cue students to listen for the reason why we always see the same side of the Moon.

RESUME video.

STOP video where narrator states, "For this reason, we always see the same face turned towards us."

Select two students to help in a demonstration of this concept. One student will be the Earth and stand still, while the other student will represent the Moon orbiting the Earth. Instruct the Moon to walk around the Earth stopping at four equidistant points while always keeping their face towards the Earth. At each of the four points, ask the student what they see behind the Earth. Each time the response will be something different until they come full circle. Then have the Earth sit down. Now tell the Moon to stand in place and slowly turn around, stopping at four equidistant points. At each point, have the Moon state what they see. The responses should be identical to their previous answers. This proves that they did indeed rotate once on their axis as they revolved once around the Earth. Before continuing, cue the students to look for the relationship between the Moon's phases and human behavior.

RESUME video.

PAUSE at scifax question, "Do the Moon's phases affect human behavior?" After soliciting student responses, discuss why full Moons are popular in folklore and horror stories. Cue students to look for illustration of a lunar eclipse and to listen for who first thought that the Earth was round, and why?

RESUME video.

PAUSE at scifax question, "Does the Moon affect events on Earth?" Solicit student responses and discuss with the class.

RESUME video to reveal answer, then END first video tape segment.

INSERT second video tape, Nova, July 11, 1991: Solar Eclipse. Inform students they are about to see a video on solar eclipses.

To give the students a specific responsibility while viewing, have them be on the lookout for the following information: definitions of first contact, second contact, totality and the corona. Alert them to the fact that this segment will be repeated so they can gather all the information that they need.

START video after the beginning credits are finished, where the narrator says, "Astronomers have come from around the world to peer into the mysteries that can be seen only during the four minutes when Sun and Moon meet."

PAUSE video after graphic showing a solar eclipse where the narrator says, "In July, 1991, it is Hawaii's turn."

REWIND video to the beginning of the graphics showing a solar eclipse. REPLAY this segment so the students may write down the information given quickly here. REPLAY a third time if necessary.

STOP video after showing of an actual solar eclipse where Jack Eddy says, "Delay eclipse seven days. Send more kaopectate."
Post-Viewing Activities
The Eclipse Stick. This activity is best when done outdoors with sunlight. However, there is no need to venture outdoors until the eclipse stick is constructed.

Divide the class into groups of four. Inform the class they are about to create a scale model of the Earth-Moon system to demonstrate solar and lunar eclipses. Ask the students what the difference is between a model and a scale model? (A scale model depicts objects in an exact ratio to each other, whereas a regular model doesn't necessarily do this.) Have students give examples of scale models they have seen or used (toy boats, cars, airplanes, dinosaurs, model kits from hobby stores).

Ask the students to think about the size of the Moon compared to the Earth and to guess which is bigger (the Earth is). About how much bigger is the Earth than the Moon? (Solicit various responses, then tell them the Earth is about four times larger than the Moon.)

Distribute the materials listed above for the Postviewing Activity except for the long stick. Have students measure the diameter of the ping pong ball. Tell them that if this is to represent the Earth in our model, how big should our moon be? (The ping pong ball measures about 1 1/2" in diameter. One fourth of that would be approximately 3/8".) Once this calculation has been made, instruct them to construct a Moon from the clay that will measure 3/8" in diameter.

Now that they have the relative sizes of the Earth and Moon figured out, tell the students they now need to place the two bodies the proper distance apart. Using the ping pong and clay balls, have each group discuss about how far apart the two bodies should be. Have them demonstrate this with their hands. The correct answer is about 30 Earth diameters! Once they have been given this answer, have them calculate how far apart the two bodies need to be if we know that the ping pong ball is 1 1/2" in diameter. (1 1/2" x 30 = 45")

At this point, the long sticks may be distributed to the groups. Have the students measure the distance between the two holes. It should equal 45".

Have the students place the clay ball on the tooth pick, and stick the toothpick in the smaller of the two holes on the long stick. (Holes should have been predrilled per instructions in materials section above.)

Instruct the students to take a 2"-piece of masking tape and roll it into a loop so that the sticky side is on the outside. Have them stick this onto the top of the golf tee, attach the ping pong ball and insert the tee into the larger hole in the long stick.

The eclipse stick is now ready for use. At this point, the class can be taken outside into the schoolyard on a bright sunny day.

Ask the groups, in what order do the Sun, Earth and Moon need to be for there to be a lunar eclipse? (The correct response would be: Sun-Earth-Moon in order for the Moon to be in the Earth's shadow.) Ask the groups if the Earth's shadow will cover part, or all, of the Moon? Have them keep their answers in mind as they perform the following demonstration. The groups can demonstrate a lunar eclipse by having one student stand with their back to the Sun so that their shadows fall in front of them. That student should slant the eclipse stick over one of his/her shoulders with the ping pong ball (Earth) at the top (closer to the Sun) and the clay ball (Moon) at the bottom. Have the students play with the shadow of the Earth until it falls on the Moon. The Earth's shadow will be big enough to cover the entire Moon with some to spare. They can model a partial lunar eclipse by moving the Earth's shadow over just the edge of the Moon. Give each student in the group an opportunity to model the total and partial lunar eclipse before moving on to the solar eclipse demonstration.

Now ask the students, in what order do the Sun, Earth and Moon need to be in to have a solar eclipse? (The correct answer is Sun-Moon-Earth in order for the Earth to be in the Moon's shadow.) Ask them if the Moon's shadow will cover all or part of the Earth? Again, have them keep their answers in mind as they perform the demonstration. Have one student stand with his/her back to the Sun once more. Have him/her place the eclipse stick over his/her shoulder with the clay ball at the top and the ping pong ball at the bottom. The student should align the shadow of the clay ball until it falls on the ping pong ball. Ask the students, judging by this model, can a solar eclipse be viewed from anywhere on the side of the Earth facing the Sun? The answer is no, because the Moon's shadow will only cover a portion of the Earth just as the clay ball's shadow covers only a portion of the ping pong ball. This is due to the relative small size of the Moon compared to the Earth. Have them move the shadow all over the Earth to show that it can't cover the whole planet at one time. Again, a partial solar eclipse can be modeled by moving the Moon's shadow over just the edges of the ping pong ball. Each student should also get a chance to model the total and partial solar eclipses before concluding this activity.
Action Plan
Visit a planetarium, or have a portable planetarium visit your school (check with local planetariums and your Yellow Pages).

Contact your local astronomy club and invite a guest speaker. These local clubs are often very accommodating. Again, consult with your local planetarium for this information.

Contact your regional NASA educational resource center for free, or low cost, information and materials available to educators.

View (or tape) the five-minute TV program, Star Hustler, hosted by Jack Horkheimer. This program provides weekly updates on happenings in the heavens that can be viewed with the naked eye or a small pair of binoculars. Check your local PBS schedule for air times.
Extensions
Math: The Moon has a mass 1/6 that of Earth's, therefore its gravitational pull is 1/6 of the Earth. Have each student multiply their Earth weight by 0.6 to find their Moon weight. Then measure how high they can jump on Earth. Since the gravity on the Moon is 1/6 of Earth's, they would be able to jump six times higher on the Moon! Have each student calculate how high that would be for themselves. (Variations on this exercise could be ball tosses, running jumps and hopping. You could do an entire Moon Olympics!)

Art: Have your students design and construct a model of a lunar community. What environmental concerns will they need to look out for?

Social Studies: Research the history of the Moon's exploration by American, Russian and European spacecraft and the American astronauts during the Apollo program.

Language Arts: Read the following books as a class and contact your media center specialist for other suggestions: Yolen, Jane, Owl Moon. New York, NY: Scholastic, Inc., 1987. A Caldecott Medal winner.

Ehlert, Lois, Moon Rope. New York, NY: Harcourt Brace Jovanovich, 1992. A Peruvian folktale in both English and Spanish with vivid illustrations.

Bruchac, Joseph and London, Jonathan, Thirteen Moons on Turtle's Back. New York, NY: Philomel Books, 1992. Describes a Native American year of Moons with great illustrations.

Caduto, Michael J. and Bruchac, Joseph, Keepers of the Night. Golden, CO: Fulcrum Publishing, 1994. Native American stories and nocturnal activities for children.

Master Teacher: Daniel E. Reidy
Newfound Memorial Middle School, Bristol, NH

This Master Teacher would like to acknowledge Dick Cowan and staff from the Christa McAuliffe Planetarium in Concord, NH, for their contribution to this lesson plan.

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