Astronomy 101 Lab Manual



Lab 2: Lunar Mechanics LabPurpose: To understand the motions of the moon relative to the Earth and Sun. Materials: Modeling the Moon’s Motions Lab Set, and Pencil Time: 2 hoursTotal Points: 35 possibleProcedures:Answer any numerically listed item for assessmentActivity #1: Modeling the Moon’s MotionsPlace each model (Sun, Earth and Moon) in a cap. This will keep the models from rolling around while you work with them. Find the “Orbit of the Moon” sheet and lay it down on a flat surface. Place the Sun model on the spot on the sheet labeled “Sun”. Place the Earth model and cap on the dot labeled “Earth.” Make sure you place the Earth model so that the blue side, representing daylight, faces the Sun. Place the Moon model and cap on top of position 1 on the sheet. Make sure you place the Moon model so that the black dot faces the Earth.Move the Moon from position 1 to position 2, making sure that the black dot continues to face the Earth. To do this, you will need to slightly turn or rotate the Moon model.Move the Moon model from position 2 to position 3, making sure that the black dot continues to face the Earth. Again, you will need to slightly turn or rotate the Moon model.Continue moving the Moon model from one position to the next along its orbital path around the Earth, until the Moon has completed its orbit around the Earth. Throughout this exploration, make sure that the black dot on the Moon ALWAYS faces the Earth.Move the moon counterclockwise completely around the Earth (positions 1-8).The motion of the Moon around the Earth is called ______________________.The time that it takes for the Moon to make one complete revolution on its orbit around the Earth is known as a (sidereal or synodic)_____________________ month.How many Earth days does it take for the moon to make one complete revolution around the Earth? _____________________How many degrees does the Moon move during one complete revolution around the Earth? ____________________Using your answers from questions 3 and 4, determine how many degrees the Moon moves each Earth day. ___________________________________Using your answer from question #5 above, determine how many degrees the Moon moves in 1 hour. _______________________Repeat the entire activity, moving the Moon around the Earth. Make sure that the dot on the Moon always faces the Earth as it revolves around the Earth.Does an Earth bound observer ever see the back side of the Moon (that is, the side with no dot) at any point during the Moon’s rotation? _________________To an Earth bound observer, does the Moon appear to rotate? ________________ Does the Moon actually rotate? _____________________Repeat the entire activity again, moving the Moon around the Earth. Make sure that the dot always faces the Earth as it revolves around the Earth.Did the dot on the Moon always face the Sun? __________________Would an observer on the Sun ever see the back of the Moon (that is, the side with no dot on it) at any point during the Moon’s rotation? __________________________To an observer on the surface of the sun, does the Moon appear to rotate? ___________________From this activity, you should be able to see that the Moon rotates on its axis as it revolves around Earth. To an Earth Bound observer, however, the Moon does not appear to rotate as it revolves around the Earth. For this to occur, what must be the relationship between the Moon’s rotation rate and orbital period (is the rotation rate faster, slower or equal to the orbital period)? ___________________________________From your answer to number 12, how many Earth days does the moon take to complete one rotation on its axis? _____________________________________What is the name of this phenomenon? ____________________________Activity #2: Phases of the MoonFor this activity, you will use the half white – half black ball for the moon. Again, place each ball in a cap to keep them from rolling. Find the “Orbit of the Moon” sheet and lay it down on a flat surface. Place the Sun model on the spot on the sheet labeled “Sun”. Place the Earth model and cap on the dot labeled “Earth.” Make sure you place the Earth model so that the blue side, representing daylight, faces the Sun. Place the Moon model and cap on top of position 1 on the sheet. Keep the following rules in mind throughout this exploration:The white side of the Moon should always face the Sun. In order to achieve this, you must not turn or rotate the Moon.For a portion of this activity, you will be asked to observe the Moon from the perspective of an observer on Earth. As such, you will need to move out of your chair and crouch down to observe the Moon model at eye-level from the Earth’s perspective. You will also need to move around the circle, to a point directly opposite the Moon model, as shown in Figure 2. For instance, when the Moon is at Position 1, you should observe it at eye-level from Position 5; when the Moon is at Position 2, you should observe it from Position 6, and so on.When identifying each phase of the Moon, be sure to note whether the Moon is waxing or waning, gibbous or crescent, full or new, or first or third quarter, as appropriate.Answer the questions 1-5 below for Position 1 at this point. Without rotating the model, move the Moon counterclockwise from position 1 to position 2 along the Moon’s orbital path, as shown in Figure 2. Answer the worksheet question 7 for Position 2.Without rotating the model, move the Moon counterclockwise to the next position along the Moon’s orbital path, as shown in Figure 2. Answer the worksheet questions 8-11 for the next position.Repeat step 4 for all of the remaining positions on the “Orbit of the Moon” sheet, until you have completed the entire orbit and are back at Position 1. Be sure to answer all the questions and fill in all three diagrams.Locate Diagram 1 (“The Moon in orbit as viewed from above”) on the worksheet provided at the end of this section. Use a pencil to fill in the circle at Position 1, so it shows how the Moon model appears at Position 1 when viewed from above.Locate Diagram 2 (The Moon as viewed from Earth) on the worksheet. Use a pencil to fill in the circle at Position 1 so it shows how the moon model appears at Position 1, when viewed from the perspective of a person on the Earth. On the line below the circle at Position 1, write the name of the phase of the Moon in this position.Locate Diagram 3 (Earth as viewed from the Moon) on the worksheet. Use a pencil to fill in the circle at Position 1 so it shows how Earth appears when the moon is at Position 1, when viewed from the perspective of a person on the Moon. On the line below the circle at Position 1, write the name of the phase of Earth in this position.What is the phase of the Moon in Position 1? _______________________________How many days will pass before this phase will be repeated? ____________________________The time period in question 2 is the length of a ________________________ (sidereal or synodic) month.A person on Earth experiences sunrise as the Earth rotates into a position where they can see the sun. The same is true for moonrise. Look at the geometry of Position 1. Can you figure out what time the Position 1 moon rises? How?What time does this phase of the moon rise? _____________________________Repeat Steps F and G for Positions 2-4. Below the name of each phase on Diagram 2, write the approximate time at which the phase rises. Repeat Step H for Position 3.The term used to describe the Moon as the lit portion increases is _________________________. The term used to describe the Moon as the lit portion decreases is _______________________.At position 2, which side of the Moon is lit, the left or the right? _______________________At position 3, the Moon has now completed _________________ percent of its orbit around the Earth.In an actual lunar month (synodic), approximately how long does it take for the Moon to travel from position 1 to position 3?_________________________Now carry out Steps F and G for the remaining phases, including rise times for each phase. Show the results on your worksheet. Repeat Step H for Positions 5 and 7.In an actual lunar month, approximately how long does it take for the Moon to travel from position 1 to position 5? _____________________________________Summarize what you’ve learned by explaining why the Moon appears to go through a cycle of phases. Activity #3: ConclusionIf you have understood everything you’ve read so far, you should now be able to draw a diagram showing the positions of the Sun, Moon and Earth for each of the eight principle phases. Include sketches of what these phases look like from Earth and their rise and set times. Do this without looking at your previous drawings or at any other diagram to test your understanding. Assignment Reflection: ................
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