GE 150 Astronomy

1. GE 150 Astronomy Week #3 January 29, 2013

2. Homework • Homework #1 – Due Now • Solutions posted on Blackboard Vista • Grades posted there as well (when finished) • Pick-up at Seyi’s office hours • Homework #2 – The Seasons Ranking Task • Download from Blackboard Vista • Due beginning of class Feb 5

3. Anonymous Attendances • 2401 • 4335 • 6846 • 7183 • 7992

4. How long did it take to get this picture?

5. Path of the Sun Yearly Changes

6. The changing position of the Sun during the year! March 20th/Sept. 22nd December 21st June 20th Zenith E S N W Sun at Noon throughout the year

7. Altitude of the Sun Animation NOTE: how the altitude of the Sun at noon changes during a day and over the course of the year. Remember: Sun crosses meridian at noon and reaches it’s highest point in the sky for that day NOTE: how the shadows cast changes during a day and over the course of the year. sun

8. Altitude of the Sun Animation NOTE: how the altitude of the sun at noon changes during a day and over the course of the year. NOTE: how the shadows cast changes during a day and over the course of the year. NOTE: where the sun rises and sets Will be covered in today’s Lecture Tutorial

10. Tutorial: Path of the Sun – p.89-92 Work with your partners! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Come to a consensus answer you agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help. p. 87-90 if using 2nd edition

11. Under which of the following circumstances will a vertical flagpole not cast a shadow as seen from the continental United States? every day at noon every day at the time when the sun is highest in the sky when the sun is highest in the sky on the summer solstice when the sun is highest in the sky on the winter solstice none of the above

12. If you are located in the continental U.S. on the first day of October, how will the position of the Sun at noon be different two weeks later? It will have moved toward the north. It will have moved to a position higher in the sky. It will stay in the same position. It will have moved to a position closer to the horizon. It will have moved toward the west.

13. For an observer in the continental U.S., which of the three shadow plots, shown at right, correctly depicts the Sun’s motion for one day? Shadow plot A Shadow plot B Shadow plot C All three are possible, on different days of the year. None of the plots are possible.

14. For an observer in the continental U.S., how many X’s in the figure below correctly show(s) the possible positions of the Sun’s shadow at noon? Note that the position of the Sun’s shadow at noon on the Winter and Summer Solstices are indicated with a dot. One Two Three Four Five

15. Path of the Sun Seasons: Conclusion

16. Complete this statement! When the noontime Sun is ____________________________ it’s summer; and when the noontime Sun is ____________________________ it is winter?

17. The changing position of the Sun during the year! March 20th/Sept. 22nd December 21st June 20th Zenith E S N W

18. Which of these are true and which are false statements about the causes of the seasons and what evidence is there to support your answer? Earth is closer to the Sun in summer than in winter. During the summer, the Sun is giving off more energy and when it is winter the Sun is giving off less energy. When it is summer, more sunlight reaches Earth than it does during the winter.

19. Seasons Animation • Note that the Earth’s rotational axis is tilted relative to the Earth’s orbit and how much directsunlight shines on the northern and southern hemispheresthroughout a year. • How is this related to the seasons?

20. Tilted 23.5 degrees from vertical

22. Number of Daylight Hours Not to scale! 67°N 27°N Equator 27°S 67°N

23. The Reasons for the Seasons • The tilt of the Earth’s axis is the cause for the seasonal changes – it contributes two major effects

24. The Reasons for the Seasons: 1 The light from the Sun strikes the ground more directly in the Summer than in the Winter thus concentrating more of the Sun’s energy.

25. The Reasons for the Seasons: 2 The Sun spends more time above the horizon in the Summer than Winter resulting in longer days with more hours for heating

26. When the Sun is high in the sky during the day, the number of daylight hours is greater and the amount of direct sunlight received is greater. This results in Summer. Note how little the ‘beam’ of light is spread out in Summer

27. When the Sun is low in the sky during the day, the number of daylight hours is less and the amount of direct sunlight received is less. This results in Winter. Note how much more the ‘beam’ of light is spread out in Winter

28. The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight Which positions (A, B, C or D) correspond with which seasons (fall, summer, spring, winter) for the northern hemisphere? What about the southern hemisphere? A D B C

29. The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight What are the possible dates for positions A, B, C and D? A D B C

30. The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight

31. GE 150 Astronomy Week #3 January 31, 2013

32. Homework • Homework #2 – The Seasons Ranking Task • Download from Blackboard Vista • Due beginning of class Feb 5 • Homework #3 – Lunar Phases Ranking Task • Download from Blackboard Vista • Due beginning of class Feb 7 • Exam #1 – Feb 12

33. The Reasons for the Seasons • The tilt of the Earth’s axis is the cause for the seasonal changes – it contributes two major effects

34. The Reasons for the Seasons: 1 The light from the Sun strikes the ground more directly in the Summer than in the Winter thus concentrating more of the Sun’s energy.

35. The Reasons for the Seasons: 2 The Sun spends more time above the horizon in the Summer than Winter resulting in longer days with more hours for heating

36. Lecture: Tutorial Seasons p. 93-99 • Work with your partners! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you agree on. • If you get stuck or are not sure of your answer, ask another group. • If you get really stuck or don’t understand what the Lecture Tutorial is asking, ask one of us for help. • p. 91-96 in 2nd edition

37. Looking at the images below, which letter (a-e) best represents winter in the United States? Sunlight Sunlight a c 2 3 b e Sun Note: this drawing is not to scale. In fact you could fit more than 11,000 Earths between the Sun and the Earth. d

38. Which of the locations, identified with an “x” for each of the situations (A – E), would experience the coolest temperature over the course of one day? warmest Cross-Tab Label 0 / 10

39. Which of these are true and which are false statements about the causes of the seasons and what evidence is there to support your answer? Earth is closer to the Sun in summer than in winter. During the summer, the Sun is giving off more energy and when it is winter the Sun is giving off less energy. When it is summer, more sunlight reaches Earth than it does during the winter.

40. Lunar Phases

41. How are the motions and positions of Earth and the Sun connected to what happens on Earth? Earth’s rotation on its axis determines the length of the day. Earth’s orbit around the Sun determines the length of the year. The tilt of Earth’s rotational axis with respect to the plane of Earth’s orbit causes the seasons.

42. The changing phases of the Moon originally inspired the concept of the month

43. Some Lunar Facts: Mean distance: 385,000 km or 30 Earth Diameters Diameter: 3480 km or 0.273 Earths Time from New Moon to New Moon: 29.5 days

44. Names of Moon Phase • New Moon • Waxing Crescent • First Quarter • Waxing Gibbous • Full Moon • Waning Gibbous • Third Quarter • Waning Crescent

45. The Causes of Moon Phases • Think about the answer to this question: What causes the phases of the Moon? • Take out a piece of paper and quickly write out a brief answer. Put your name and 1st four digits of Eagle ID # turn in at end of class

47. Let’s put it in motion! Pay attention to where the Moon, Sun and Earth are located and how the Moon appears from Earth at each of these positions. Look at how much of the Moon is illuminated when at each position. Look at which side of the Moon is illuminated when at each position.

49. Phases of the Moon Although the Moon is always ½ lit by the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its orbit.

50. Phases of the Moon Although the Moon is always ½ lit by the Sun, we see different amounts of the lit portion from Earth depending on where the Moon is located in its orbit.