Did you get the Key Ideas from the Seasonal Stars Lecture Tutorial?

1. Did you get the Key Ideas from the Seasonal Stars Lecture Tutorial?

2. Post Tutorial Question • What component of Earth’s motion causes the stars to rise earlier on successive nights? A) its rotation about its axis B) its orbit around the Sun C) the tilt of its rotation axis

3. W North Star Two months from the time shown what constellation will be high in the Southern sky, at Midnight? At Noon?What sign will a person be if they are born at that time? E Taurus Aries Gemini South Pisces Cancer W E Figure 2 – What it would look like if you were the observer in Figure 1 Aquarius Pisces Capricornus Aries 1 day Sagittarius Taurus Scorpius 365 days Libra Gemini Virgo Cancer Leo Figure 1 For more practice at this – Look back at Part I of the “Seasonal Stars” Lecture Tutorial

4. Post Tutorial Question • One night, you see the star Sirius rise at exactly 7:36 PM. The following night it will rise A) slightly earlier. B) at the same time. C) slightly later.

5. Post Tutorial Question • One evening at midnight, you observe Leo high in the southern sky at midnight. Virgo is to the east of Leo and Cancer is to the west. One month earlier, which of these constellations was high in the southern sky at midnight? A) Leo B) Virgo C) Cancer

6. How do we define what time it is? What time is it now? http://www.jgiesen.de/SiderealTimeClock/index.html

10. How do we define what time it is? What time is it now? http://www.jgiesen.de/SiderealTimeClock/index.html

11. How do we define a day?

12. Tutorial: Solar vs. Sidereal Day p.11 • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both 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 me for help.

13. Which takes longer to complete?A) one solar day.B) one sidereal day.C) Both take the same amount of time.

14. Image that Earth begins orbiting the Sun twice as fast while maintaining the same rotationrate. It now orbits once around the Sun every 6 months. In this case, what happens to thelength of the solar day? A) It gets slightly longer. B) It does not change. C) It gets slightly shorter. D) It is cut in half. E) It doubles.

15. The changing position of the Sun during the year!

17. How can we describe the motion of the sun in the sky? meridian X Zenith or overhead east south west

18. How can we describe the motion of the sun in the sky? meridian zenith LUNCH!! PM or post meridian AM or ante meridian east south west

19. Where is the Sun at noon today? hereorthere? zenith east south west

20. Where is the Sun at noon today? zenith What about tomorrow at noon? there east south west

21. What about the path of the Sun? zenith What about tomorrow at noon? JUST A LITTLE LOWER !! there east south west

22. Where is the Sun throughout the year? June 21 Summer Solstice Mar 21 (Vernal) and Sept 21 (Autumnal) Equinox Dec 21 Winter Solstice zenith east south west

23. The time for the sun to go from being highest in the sky at noon, to lowest and back to highest again is… ONE YEAR zenith east south west

24. Where would the Sun be on your birthday?

25. Rising Setting Hour by hour of path of sun from the southern hemisphere!

26. Position of the Sun when photographed during the day of the winter and summer solstice

27. Shadow Paths Sundial Time Lapse

28. Path of the Sun when photographed from Phoenix, the Mars rover, up near the north pole of Mars.

29. Sun at the exact same time of the day over the course of a full year. The shape is called an analemma. This picture shows every 10 days.

30. Altitude of the Sun Animation • Note where the sun rises and sets • Note how the altitude of the sun changes during a day and over the course of the year. • Note how the shadow changes during a day and over the course of the year. http://astro.unl.edu/naap/motion3/animations/sunmotions.swf

31. Tutorial: Path of the Sun p.87 Tutorial: Seasons p.91 • Work with a partner! • Read the instructions and questions carefully. • Discuss the concepts and your answers with one another. • Come to a consensus answer you both 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 me for help.

32. 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 0/0

33. 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.

34. For an observer in the continental U.S., which, if any, of the x’s (a – e) in the figure belowcorrectly shows the position of the Sun’s shadow at noon? Choose all that could be correct.Note that the position of the Sun’s shadow at noon on the Winter and Summer Solstices areshown.

35. NORTH x x Shadow plot A x x x x x Shadow plot B x x x x x x WEST EAST x x x x x x x x x Shadow plot C SOUTH 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 More than one of the plots are possible, on different days of the year. None of the plots are possible.

36. Time? • What causes Seasons?

37. Angular Momentum • If something is spinning, the axis of rotation resists a change in direction.

38. Precession

39. 26,000 years

41. Time? • What causes Seasons?

42. Rising Setting Hour by hour of path of sun from the southern hemisphere!

43. 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.

44. 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.

45. 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.

46. 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.

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

48. The tilt of Earth’s axis of rotation produces longer (or shorter) hours of more (or less) direct sunlight Which positions (1, 2, 3, or 4) correspond with which seasons (fall, summer, spring, winter) for the northern hemisphere? What about the southern hemisphere? 1 4 2 3

49. Sunlight Sunlight a c d 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. Looking at the images below, which letter (a-e) best represents winter in the United States?

50. 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 1, 2, 3, and 4? 1 4 2 3