6-8 > Earth Science
 Grade level: 6-8 Subject: Earth Science Duration: Two class periods
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Students will:
 1 understand that local solar time is determined by the position of the sun relative to an observer’s horizon 2 identify by name the phases of the moon—waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter, waning crescent, and new 3 define elongation as the measurement of angular distance (in degrees) between a line of sight from an observer on Earth to the sun and a line of sight to any other celestial object 4 understand that the phase of the moon depends upon the measurement of the eastern or western elongation of the moon from the sun.

For this lesson, you will need:
 • scissors • cardboard • thumbtack • transparency film for ink-jet or laser printer (optional) •

 Adaptation for older students:Throughout history, geometry has played an important role in helping us determine the size, shape, and placement of all the objects in our solar system—particularly our moon. Older students can challenge their creativity with the activityWhat Is the Diameter of the Moon?In this activity, they will use geometry to measure and calculate the diameter of the moon during its full phase.

 1 Compare the relative motion of the moon and the sun as they “chase” each other through the constellation of stars on a day-to-day basis. Describe how you might determine their individual rates of motion through the stars in degrees per day. 2 Ocean tides are caused by the combined gravitational interactions between the Earth and the moon and between the Earth and the sun. Explain why the difference between high and low tides is more extreme when the moon is in either the new phase or the full phase. 3 There are many references to the various phases of the moon in art, music, literature, religion, and other cultural experiences. Debate which cultural events, celebrations, and icons would not exist if the Earth did not have its companion moon to inspire human creativity. 4 Lunar eclipses can be observed about twice a year by everyone on Earth when the moon is in a full phase. Explain why a lunar eclipse does not occur for every full moon during the year. 5 Theorize why solar eclipses, which happen only when the moon is in its new phase, occur even less frequently then lunar eclipses. When they do occur, why do so few people on Earth see them? 6 The lunar cycle of phases takes 29.5 days (the synodic period), but it takes only 27.3 days (the sidereal period) for the moon to make a complete 360-degree orbit of Earth. Explain why there is a discrepancy between these two periods.

 Position a student in the front of the classroom with a basketball representing the moon held outward at arm’s length. As the student, who represents Earth, and the “moon” turn slowly in a circle, illuminate them from the back of the classroom with a bright light source (such as an overhead projector) representing the sun. Randomly call out the names of various moon phases and ask the student to stop turning when the “moon” demonstrates that phase from the student’s point of view. Have the other students critique the correctness and accuracy of each phase demonstration. To assess student understanding of the measurement of lunar elongation and its relationship to the phase of the moon, ask the student demonstrator to stop at various elongations, such as 90 degrees west elongation and 135 degrees east elongation. Students should critique this demonstration and predict which phase will be observed from the demonstrator’s point of view. Have the demonstrator confirm or correct the class’s phase predictions.

 What If There Were No Moon? Explain to students that we believe the moon and its cycles affect the life cycles of creatures great and small here on Earth. There is even some suggestion that if we had never had a moon, life would not have evolved at all on Earth. Have students use references from the library or the Internet to find 10 concrete examples of how the moon affects life in the simplest to the most complex species on the land, in the air, and under the sea. Why Do We Have a Moon? Point out to students that not every planet in our solar system has a moon. Some have two moons, and some have many. Moons come in a variety of sizes, shapes, and compositions, suggesting that there may be several different origins of the moons in our solar system. Three theories are in competition with one other regarding the origin of the Earth’s moon. The theories are known as the “molten proto-Earth theory,” the “capture theory,” and the “planetary impact theory.” Currently scientists supporting the planetary impact theory seem to be winning the debate. Have students research and report on each of the three theories and explain why the planetary impact theory seems to be preferred at this time.

 The Planetary Report A Publication of the Planetary Society, (magazine) J/F 1999Excellent information on the moon, and other moons in the solar system great pictures and text. Sky and Telescope 9/99, 118-123, 5/99, 36-38, 3/99, 53-55.These three publications of Sky and Telescope explain "Lunar glows, clouds and volcanoes" and the hype behind a blue moon.

 National Air and Space Museum Information about a variety of flight and space related topics. Jet Propulsion Laboratory's Home Page Space information. Galileo K-12 Science Lesson Plans Science lesson plans for K-12 classrooms. Space Shuttle Home Page Information about space shuttle flights. Eric Weisstein's Treasure Trove of Astronomy Allows astronomy-related searches, including information on the Earth's moon.

 Click on any of the vocabulary words below to hear them pronounced and used in a sentence. Definition:The angular distance of a planet or other celestial body from the sun. Context:When the moon is full, it is a full 180-degree elongation away from the sun. Definition:The time of day reckoned by the sun, based on 12 o’clock noon occurring at the instant of the transit of the sun’s center over the meridian. Context:When the two cowboys met face to face on Main Street, the local solar time was “high noon,” and I could see that the sun was as high as it would get in the sky on that fateful day in Tombstone. Definition:One of the cyclically recurring apparent forms of the moon. Context:I noticed that with each passing night the lunar phase changed from a mere sliver of light in the sky that chased the setting sun over the western horizon into a bigger and rounder full moon that shone down upon me all night long. Definition:The moon during the phases in which it exhibits a decreasing illuminated area. Context:I don’t like to go out after dark during a waning moon because night after night it gets darker and I get scared. Definition:The moon during the phases in which it exhibits an increasing illuminated area. Context:As the waxing moon grew brighter each night, I found it easier and safer to find my way along the path through the park on my way home from work.