1. Foundations of Astronomy Part 4 Get Mastering Astronomy account set up Get your iClicker Registered

2. Star Trail Applet – Star Motion facing South Star Trail Applet

3. Pre-Tutorial Question Imagine you are standing in the northern hemisphere. Looking directly north, you see a star just above the horizon. A little later you notice that it has shifted position slightly. Which way did it move? a)to the right, (east) b)to the left, (west) c)up, (rising) d)down, (setting)

4. The Motion of the Moon The Moon has a cycle of "phases", which lasts about 29 days. Half of the Moon's surface is lit by the Sun. During this cycle, we see different fractions of the sunlit side. Which way is the Sun here?

5. See Tutorial on book’s website for animation.

6. Cycle of phases slightly longer than time it takes Moon to do a complete orbit around Earth. Cycle of phases or "synodic month" Orbit time or "sidereal month" 29.5 days 27.3 days

7. a)the same phase in 24 hours. b)different phases in 24 hours. c) a lunar eclipse once a month. d) different sides of the Moon. Considering the Moon ’ s phases, everyone on Earth sees Question 12

8. a)the same phase in 24 hours. b)different phases in 24 hours. c) a lunar eclipse once a month. d) different sides of the Moon. Considering the Moon ’ s phases, everyone on Earth sees Question 12 The Moon goes through its cycle of phases in about 30 days; the Earth rotates once in only 24 hours. So everyone has a chance to see the same phase!

9. Eclipses Lunar Eclipse When the Earth passes directly between the Sun and the Moon. Sun Earth Moon Solar Eclipse When the Moon passes directly between the Sun and the Earth. Sun Earth Moon

10. Solar Eclipses Total Diamond ring effect - just before or after total Partial Annular - why do these occur?

11. Lunar Eclipse

12. Why don't we get eclipses every month?

13. Moon's orbit tilted compared to Earth-Sun orbital plane: Sun Earth Moon Moon's orbit slightly elliptical: Earth Moon Side view Top view, exaggerated ellipse Distance varies by ~12% 5.2 o

14. Types of Solar Eclipses Explained

15. Certain seasons are more likely to have eclipses. Solar “eclipse season” lasts about 38 days. Likely to get at least a partial eclipse somewhere. AnimationAnimation It's worse than this! The plane of the Moon's orbit precesses, so that the eclipse season occurs about 19 days earlier each year.

16. Recent and upcoming total and annular solar eclipses

17. Eratosthenes Determines the Size of the Earth in about 200 B.C. Syene Alexandria Sun's rays 7.2 o S N Earth

18. He knows the distance between the two cities is 5000 "stadia". From geometry then, 7.2 o 360 o Earth's circumference 5000 stadia = => circumference is 250,000 stadia, or 40,000 km. So radius is: 40,000 km 2p = 6366 km (very close to modern value, 6378 km!)

19. Lecture Tutorial in Introductory Astronomy Motion – Pages 1-6

20. POST-Tutorial Question You are looking toward the north and see the Big Dipper to the right of Polaris. Fifteen minutes later, the Big Dipper will appear to have moved in roughly what direction? a)east (to your right) a)west (to your left) c)up (away from the horizon) c)down (closer to the horizon)

21. POST-Tutorial Question How much time is there between when a star rises and when it sets? a)less than twelve hours a)about twelve hours a)more than twelve hours d) it depends on the star

22. Sun rise and sunset – variance with seasons Demonstration