_TrackingMotionsWorksheet

Tracking Motions Worksheet These lab activities have evolved over many years of use in Clemson University’s Department of Physics and Astronomy general astronomy laboratory. Contributors include, in chronological order, Tom Collins, Mark Leising, Neil Miller, Peter Milne, Grant Williams, Donna Mullenax, Jessica Crist, Keith Davis, Amber Porter, Steven Bromley, and David Connick. Please direct all questions, complaints, and corrections to David Connick (dconnic@clemson.edu) who is responsible for all errors and omissions. Student Name: Nicky Section: _______ The Sun's Yearly Motion Table 1. Month Constellation Rises (am) (Hour:minute) Sets (pm) (Hour:minute) Daylight Length (hours) Altitude (above horizon) (degrees Minutes) January Sagitarius 7:39 AM 5:35 PM 10 hour +32º 52' above horizon February Capricornus 7:25 AM 6:05 PM 11 hour +39º 44’ above horizon March Aquarius 6:53 AM 6:31 PM 12 hours +49º’44 above horizon April Pisces 7:11 AM 7:56 PM 13 hours +61º57’above horizon May Aries 6:36 AM 8:20 PM 14 hours +67º 48’ above horizon June Taurus 6:18 AM 8:42 PM 14 hours +72º 13’ above horizon July Gemini 6:24 AM 8:47 PM 14 hours +71º 10’ above horizon August Cancer 6:45 AM 8:28 PM 14 hours +66º 27’ above horizon September Leo 7:07 AM 7:50 PM 13 hours +58º 25’ above horizon October Virgo 7:29 AM 7:08 PM 12 hours +48º 22’ above horizon November Libra 6:56 AM 5:32 PM 11 hours +39º 05’ above horizon December Ophiuchus 7:24 AM 5:32 PM 10 hours +32º 46’ above horizon 1. What month is the Sun's altitude a maximum? June 2. What month is the Sun's altitude a minimum? December 3. In which month is the length of the day the shortest? December 4. In which month is the length of the day the longest? June 5. Describe the relationship between the altitude and the length of the day. The higher the altitude the longer the day.

6. During the longest day of the year, what is the distance from the Earth to the Sun in AU? (You will need to set the date based on your table and look at the info panel for the Sun) 1.0147 AU 7. During the shortest day of the year, what is the distance from the Earth to the Sun in AU? (You will need to set the date based on your table and look at the info panel for the Sun) 0.985281 AU 8. During lunch, you overhear a group of friends claiming that the cold weather in winter is due to the Earth being furthest from the Sun in its orbit. From your data above, is this claim true? Explain. This claim is not true. The distance in december from the Earth to the Sun AU is 0.985281 AU and in june the distance is further 1.0147 AU the cold weather and change of the season depends on the Earth’s axis tilt. 9. What is the true cause of the Seasons? (Use the information in your table and your knowledge from ASTR1010, you should mention the sun’s altitude in your answer) The Sun is in the sky for a longer period of time in the summer because of the tilt of the Earth. The Sun’s altitude is lower in December than in June, But this does not mean that it will be warmer in December. The same amount of sunlight is spread over a larger area in the winter hemisphere, meaning there will be less energy per square foot because of the angle the light is coming in from. There are longer days when the sin is in the sky shining for longer, meaning more direct sunlight, which also means more energy. For shorter winter days there is less energy per square foot which means the weather is usually cooler. 10. Does the Sun spend an equal amount of time in every Zodiacal constellation? Why or why not? (Give examples) (Look at the path of the sun through the constellations, remember the sun moves along the ecliptic at a constant rate.) No because of the large size of some of the zodiacal constellations compared to others, the Sun spends greater amount of time in the larger constellations. In addition to this, the Earth’s precession has changed where the Sun appears to be in the sky. Return to the instruction document to set up the next simulation before answering the next set of questions. Tracking Planets Table 2.

16. Now search for and center on the Moon. Does the Moon travel precisely along the ecliptic (always touch the ecliptic line)? Explain its motion relative to the ecliptic line. The moon does not travel precisely along the ecliptic path. It is always relatively close to it, but not precisely along it. On March 23rd 2020 the moon is close to the sun and a grid line. Set the time and date to see this in Starry Night. Search for and lock on the Sun then prepare to step time forward and answer the next questions. 17. How long does it take for the moon to return to the same grid line? (this is called the sidereal period) The moon returned to the same grid line on April 20th the same year. This means it took 28 days. 18. How long does it take for the moon to get close to the sun again? (this is called the synodic period) It takes the moon 30 days to get close to the sun again (April 22nd) 19. What is the difference in time for the moon to return to the same grid line (background stars) to the time it takes to return close to the sun? The difference is 2 days. 20. When viewed from above the north pole, which direction does the Earth orbit the sun, and which direction does the moon orbit the earth? (think back to ASTR1010) The Earth orbit the sun counterclockwise, and the moon orbits the Earth counterclockwise as well. 21. Do your best to explain the connection between the orbit directions as viewed from above and how we see the sun and moon move in the sky relative to the background stars (grid lines) from the surface of the Earth. Earth is moving west to east so the stars should appear to be moving east to west in out point of view.