Moon Blog: February 2014

How to Teach About the Moon

After hearing the story, students could write, with partners or individually, their own myths or legends explaining the phenomenon of the moon phases. The teacher can later engage students in a discussion about what in the Inuit story (and their own stories) they believe correspond to scientific "facts" about the moon. Again, lists would be generated based on student input. The students would then be provided with reference materials about the moon. In small groups, they would generate facts about the moon that correspond with information in the story. Teacher background information follows:

The earth's one natural satellite, the moon, is more than one quarter the size of earth itself (3456-Km diameter), making the earth-moon system virtually a double-planet. Because of its smaller size, the moon's gravity is one-sixth of the earth's gravity, as we saw demonstrated by the gigantic leaps of the Apollo astronauts.

When the moon appears smaller than a quarter, we call it a crescent. When the moon appears larger than a quarter, we call it gibbous. When the moon is getting bigger (phases New to Full) it is waxing. When it is getting smaller (phases Full to New), it is waning. For example, if today the moon were a waxing crescent, then tomorrow the crescent shape would continue to grow larger, approaching first quarter. After first quarter, the Moon would be a waxing gibbous, and continue growing until it reached full. The moon would then begin to shrink, becoming first a waning gibbous and eventually reaching third quarter. Following third quarter, it becomes a waning crescent, and continues to shrink until it becomes invisible at new moon. A helpful way to remember whether the moon is waxing or waning is the following: A crescent moon that looks like a "C" is shrinking (C for collapsing). If it looks like a "D", then it is growing. This is also true for a gibbous moon, but it is a bit trickier to see. If the edge of the moon (the real edge of the moon, not the edge of the night on the moon) is curved like a "C" the gibbous moon is shrinking. Another way to think of it is that the moon always grows or shrinks from right to left.

The class can do month-long moon observations, recording what they see during a 24 hour period, drawing the moon, noting where it is in the sky and its angle above the horizon. After a discussion of what they have learned about the moon and its phases, a lesson would be introduced.

Styrofoam Ball Simulation

Type of Lesson: Hands-on activity

Time needed: 1 hour (or one class period with follow-up the next day)

Science skills addressed:

- Describe, compare and explain the motions of the earth and the moon in the solar system. - Describe and explain common observations of the day and night skies. Summary of Lesson:

After completing this activity students should understand that the observed phase of the moon is determined by the moon's position relative to the earth and sun.

Materials: Light bulb (suspended from ceiling or on a stand) or overhead projector light Styrofoam balls 2-3 inches in diameter (have students work in pairs) Plenty of room for students to rotate! Helpful: At least one additional adult and/or high school student for assistance.

Procedure

1. Turn on the model sun and turn off the other lights in the room. Have students stand. Tell them that in this system, the lamp is sun and their head is the earth. Their nose is their hometown on the surface of the earth.

2. Ask students to stand so that it is noon in their hometown (Their nose should point toward the sun). Have students turn (rotate) until it is midnight in their hometown. Counterclockwise rotation simulates the direction as seen from the North Pole. (Midnight is when their backs are to the "sun"). Students can also rotate to show dawn and dusk in their hometowns and get an idea why the sun appears to rise in the east and set in the west.

3. Hand out the Styrofoam "moons" and have students hold them at arm's length away from (and above) their heads. Allow students to figure out how to rotate to simulate the phases of the moon as they viewed them during the previous month-long observation. (If necessary, demonstrate how the moon orbits the earth in a counterclockwise direction (from right to left). As students watch their moons, they will see that it goes through phases similar to those of the real moon.  4. Allow students to work through the phases of the moon with partner (If necessary, go through the 8 major phases of the moon with students) a. New Moon: moon is between sun and earth, students view shadowed side of "moon". b. Waxing Crescent: rotating from a new moon towards a first quarter, a backward "C" shape will appear on "moon". c. First Quarter: right half of the "moon" facing "earth" is lit (right shoulder is pointing towards the "sun") d. Waxing Gibbous: rotating from a first quarter to full moon e. Full Moon: earth is between the moon (be sure "moon" is held above "earth") and the sun, entire lit side of "moon" is visible. A lunar eclipse occurs when the moon passes through the earth's shadow. Have students simulate this event. f. Waning Gibbous: rotating from a full moon to last quarter, less and less of the moon is lit each night. g. Last Quarter: left half of side of "moon" facing the "earth" is lit (left shoulder is pointing to the "sun"). h. Waning Crescent: Rotating from a last quarter to a new moon, a "C" shape of light is seen on the left side of the "moon".  

Evaluation

Name a moon phase and have students rotate until they are in the correct phase. Inclusion of eclipses (when the "earth" is in a direct line between the "sun" and the "moon") can also be demonstrated.

Extensions and Follow-up

This lesson can be a springboard for theme immersion with the students. They can do a mapping exercise in which they indicate areas of specific interest that they would like to explore as individuals or in small groups. One idea is to allow students to explore the origin of the myths and legends about the moon. This honors and validates the beliefs of non-mainstream cultures. Following this, having discussed the myths and legends, students could write their own myth or legend about the phases of the moon. 

All About the Moon-Background Knowledge

Diagram Explanation The illustration may look a little complex at first, but it's easy to explain. Sunlight is shown coming in from the right. The earth, of course, is at the center of the diagram. The moon is shown at 8 key stages during its revolution around the earth. The moon phase name is shown alongside the image. The dotted line from the earth to the moon represents your line of sight when looking at the moon. The large moon image shows what you would see at that point in the cycle. For the waning gibbous, third quarter, and waning crescent phases you have to mentally turn yourself upside down when imagining the line of sight. When you do this, you'll "see" that the illuminated portion is on your left, just as you see in the large image. One important thing to notice is that exactly one half of the moon is always illuminated by the sun. Of course that is perfectly logical, but you need to visualize it in order to understand the phases. At certain times we see both the sunlit portion and the shadowed portion -- and that creates the various moon phase shapes we are all familiar with. Also note that the shadowed part of the moon is invisible to the naked eye; in the diagram above, it is only shown for clarification purposes. Finally, please realize this diagram is only meant to demonstrate how the phases work; the small inner moons in the diagram do not show the fact that the same side of the moon always faces Earth. So the basic explanation is that the lunar phases are created by changing angles (relative positions) of the earth, the moon and the sun, as the moon orbits the earth. If you'd like to examine the phases of the moon more closely, via computer software, you may be interested in this moon phases calendar software. Moon Phases Simplified It's probably easiest to understand the moon cycle in this order: new moon and full moon, first quarter and third quarter, and the phases in between. As shown in the above diagram, the new moon occurs when the moon is positioned between the earth and sun. The three objects are in approximate alignment (why "approximate" is explained below). The entire illuminated portion of the moon is on the back side of the moon, the half that we cannot see. At a full moon, the earth, moon, and sun are in approximate alignment, just as the new moon, but the moon is on the opposite side of the earth, so the entire sunlit part of the moon is facing us. The shadowed portion is entirely hidden from view. The first quarter and third quarter moons (both often called a "half moon"), happen when the moon is at a 90 degree angle with respect to the earth and sun. So we are seeing exactly half of the moon illuminated and half in shadow. Once you understand those four key moon phases, the phases between should be fairly easy to visualize, as the illuminated portion gradually transitions between them. An easy way to remember and understand those "between" lunar phase names is by breaking out and defining 4 words: crescent, gibbous, waxing, and waning. The word crescent refers to the phases where the moon is less than half illuminated. The word gibbous refers to phases where the moon is more than half illuminated. Waxing essentially means "growing" or expanding in illumination, and waning means "shrinking" or decreasing in illumination. Thus you can simply combine the two words to create the phase name, as follows: After the new moon, the sunlit portion is increasing, but less than half, so it is waxing crescent. After the first quarter, the sunlit portion is still increasing, but now it is more than half, so it is waxing gibbous. After the full moon (maximum illumination), the light continually decreases. So the waning gibbous phase occurs next. Following the third quarter is the waning crescent, which wanes until the light is completely gone -- a new moon. The Moon's Orbit You may have personally observed that the moon goes through a complete moon phases cycle in about one month. That's true, but it's not exactly one month. The synodic period or lunation is exactly 29.5305882 days. It's the time required for the moon to move to the same position (same phase) as seen by an observer on earth. If you were to view the moon cycling the earth from outside our solar system (the viewpoint of the stars), the time required is 27.3217 days, roughly two days less. This figure is called the sidereal period or orbital period. Why is the synodic period different from the sidereal period? The short answer is because on earth, we are viewing the moon from a moving platform: during the moon cycle, the earth has moved approximately one month along its year-long orbit around the sun, altering our angle of view with respect to the moon, and thus altering the phase. The earth's orbital direction is such that it lengthens the period for earthbound observers. Although the synodic and sidereal periods are exact numbers, the moon phase can't be precisely calculated by simple division of days because the moon's motion (orbital speed and position) is affected and perturbed by various forces of different strengths. Hence, complex equations are used to determine the exact position and phase of the moon at any given point in time. Also, looking at the diagram (and imagining it to scale), you may have wondered why, at a new moon, the moon doesn't block the sun, and at a full moon, why the earth doesn't block sunlight from reaching the moon. The reason is because the moon's orbit about the earth is about 5 degrees off from the earth-sun orbital plane. However, at special times during the year, the earth, moon, and sun do in fact "line up". When the moon blocks the sun or a part of it, it's called a solar eclipse, and it can only happen during the new moon phase. When the earth casts a shadow on the moon, it's called a lunar eclipse, and can only happen during the full moon phase. Roughly 4 to 7 eclipses happen in any given year, but most of them minor or "partial" eclipses. Major lunar or solar eclipses are relatively uncommon. Source: http://www.moonconnection.com/

ALCOS Correlations to Teach About the Moon

K.10 Identify objects observed in the day sky with the unaided eye, including the sun, clouds, moon, and rainbows. 1.11 Compare the day sky to the night sky as observed with the unaided eye. 2.3 Recognize that light travels in a straight line until it strikes an object. Recognizing that light can be reflected. 2.11 Identify basic components of our solar system, including the sun, planets, and Earth’s moon. 3.14 Describe the position of Earth, the moon, and the sun during the course of a day or month. 4.9 Describe the appearance and movement of Earth and its moon Identifying waxing and waning …… Identifying lunar and solar eclipses. 4.10 Describe components of our solar system. 5.11 Compare distances from the sun to planets in our solar system. 6.8 Describe how Earth’s rotation, Earth’s axial tilt, and distance from the equator cause variations in heating and cooling of various locations on Earth. 6.9 Identify the moon’s phases.