Astronomy Lab Lunar Phases.docx

Lunar Phase Simulator – Student Guide Part I: Background Material Answer the following questions after reviewing the background pages for the simulator. Page 1 – Introduction to Moon Phases Is there a dark side of the moon? (Note: this question can be effectively answered either yes or no, so it is important to explain your reasoning.) Yes; there is always a side of the moon that faces away from the Earth, making it known as the “dark side.” How long does it take the moon to complete one cycle of phases, in days? 29.5 Days If the moon is full today, what phase do you expect it to be at in a week? Third Quarter How about one month later? If the moon is full today, it will be a full moon again a month later. Many words in astronomy are also non-astronomical uses as well. Using your knowledge of how the terms on the left are used in astronomy match them with the non- astronomical uses on the right. waning convex, rounded -- also hunch-backed, having a hump gibbous to increase in size, quantity, volume, intensity, etc. waxing decrease in magnitude, importance, brilliancy, intensity, etc. The following sketches of the moon's appearance were made over about four weeks. Identify the phases and put them in the correct numerical order. One is labeled for you. NAAP – Lunar Phase Simulator 1/10

Picture Order Phase Picture Order Phase A 3 Waning Crescent D 4 First Quarter B 1 Waning Gibbous E 5 Waxing Gibbous C 6 Full Moon F 2 Third Quarter Page 2 – Introduction to Moon Phases From the perspective of an observer above the North Pole, the moon moves clockwise / counter-clockwise (circle) in its orbit around the earth. In the diagram below the sun's light is coming in from the right. The moon's location is marked at several points on its orbit. These are the points the moon was at when the sketches above were drawn. Identify each position with the letter of the corresponding sketch. NAAP – Lunar Phase Simulator 2/10 D

Page 3 – The Time of Day Use the interactive diagram at the bottom of the page to determine the direction of the earth’s rotation when viewed from above the North Pole. (Hint: rotate the observer – the stick figure – to the noontime position, then sunset position, then midnight position, and finally back to sunrise position. The earth has made one complete rotation and the observer has experience one daily (diurnal) cycle of day and night.) When viewed from above the North Pole, does the earth rotate clockwise or counter-clockwise? Counter-Clockwise Page 4 – Rising and Setting When the moon crosses the western side of the horizon plane it is rising / setting (circle). When it crosses the eastern side of the horizon plane it is rising / setting (circle). Page 5 – The Horizon Diagram NAAP – Lunar Phase Simulator 3/10 E A F B C

Moon Earth sunlight Describe the location of the moon in the sky of the horizon diagram at bottom. Use direction words (like north, west, etc.) and estimate its altitude in degrees. Northwest with an altitude of about 45 degrees. Page 6 – The Witness and the Detective If we know the moon's position in the sky and its phase, we can estimate the Time . In general, knowing any two of the following three things allows us to estimate the third: 1. moon's position in the sky 2. moon’s phase 3. the time Part II: Visualizing Phases We can determine the appearance of the moon based on the orientation of the moon and sun with a simple heuristic. In the figure below, bisect the moon twice . a) Draw a line (perpendicular to the direction of sunlight) that shows the half of the entire moon that is illuminated and shade the shadowed region. b) Draw a line (perpendicular to the Earth-moon line) that shows the half of the moon visible for an observer on earth. c) Mark the region that is both visible from earth and illuminated by the sun. That region will be the phase of the moon we on earth see. NAAP – Lunar Phase Simulator 4/10

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