THE VIEW FROM EARTH

1. THE VIEW FROM EARTH

2. EARTH IN MOTION

3. Rotation: Period = 24 Hours • 2. Revolution: Period = 365.2564 Days • 3. Precession: Period  26, 000 years • 4. Motion of Solar System relative to nearby stars • 5. Solar System orbits center of Milky Way: • Period  230 million years • 6. Milky Way Moves within Local Group ‘Swarm’ • 7. Local Group partakes of Expansion of Universe

4. Rotation 750 mi/hr at State College! North Pole

5. Night & Day Night Day To Sun Twilight Zone

6. One way to get rotation period . . .

7. 67,000 mi/hr! Revolution 1 AU View from above Earth’s north pole.

8. Orientation of Earth in Space I North I = 23.5o Orbit Plane (‘Ecliptic Plane’) Equatorial Plane

9. Gravity Precession Top

10. Gravity of sun & moon try to change direction of Earth’s rotation axis – Earth Precesses.

11. Rotation axis fixed in space – over short intervals. p. 20

12. Motion relative to nearby stars p. 22

13. 500,000 mi/hr Orbit about center of Milky Way p. 23

14. Motion within Local Group 3,000,000 ly Milky Way 180,000 mi/hr M31

15. Collision of Milky Way & Andromeda Spiral (M31)

16. Expansion of the Universe

17. Before Baking After Baking ‘Raisin Cake’ Model p. 24

18. LATITUDE, LONGITUDE & ALL THAT

19. L The Meaning of Latitude N L  Latitude Earth

20. 90o N Terminator 66.5oN 23.5o N 0o N p. 33

21. Longitude p. 33

22. Earth’s Grid State College, PA Latitude = Longitude = p. 33

23. CELESTIAL SPHERE: A MODEL OF THE SKY

24. RISING & SETTING

25. Earth seen from above north pole 4 hours later

26. Meridian A locale in the northern hemisphere.

27. Rising or setting? (Looking west or looking east?)

28. South Celestial Pole Anglo-Australian Observatory Circumpolar Stars

29. Circumpolar 35o N Lat p. 33

30. THE SKY & YOUR LATITUDE

31. Z A NCP Horizon N A = latitude of observer

33. At a Mid-Northern Latitude

34. At the North Pole

35. At the Equator

36. Position of NCP relative to stars shifts due to precession.

37. DIFFERENT STARS IN DIFFERENT SEASONS

38. November September July

39. CONSTELLATIONS

40. Greco-Roman Tradition 18th Century “Traditional”: Person, animal, object depicted by pattern of stars. e.g., Cygnus – Swan Ursa Major – Big Bear Scorpius – Scorpion Boötes – Herdsman Antlia– Air Pump p. 28

42. Orion - Hunter “Modern” (from 1928): Well-defined region of celestial sphere. * 88 modern constellations.

43. Winter Triangle

44. Orion

45. Milky Way p. 30