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MOTIONS IN THE SKY

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  1. MOTIONS IN THE SKY

  2. Summary of easily visible motions of celestial objects

  3. Summary of easily visible motions of celestial objects

  4. Summary of easily visible motions of celestial objects

  5. The Trick: apparent motions in the sky are compound and relative, not absolute • They can have two entirely different causes: • Intrinsicmotions of the objects themselves • Motions of the platformfrom which we observe them --- namely, the Earth: • Earth is a spherical, spinning, tilted body in orbit around the Sun

  6. Today: Platform Effects • Effects of Earth's SPIN • Effects of Earth's MOTION IN ORBIT around the Sun • Effects of the TILT of Earth's rotational axis

  7. Today: Platform Effects • Effects of Earth's SPIN: westward diurnal motion • Effects of Earth's MOTION IN ORBIT around the Sun: eastward motion of Sun, planets • Effects of the TILT of Earth's rotational axis: N/S motion of Sun, Moon

  8. Today: Platform Effects • Effects of Earth's SPIN • Effects of Earth's MOTION IN ORBIT around the Sun • Effects of the TILT of Earth's rotational axis Earth’s motions are almost entirely imperceptible to us

  9. Timelapse Videos of Night Sky • Time lapse video, South Australia, Alex Cherney Check YouTube & Vimeo

  10. A flat, stationary Earth?

  11. First ever image of whole earth, Apollo 8 mission, 22 Dec 1968

  12. ISS-video, YouTube • ISS-video, HuffPost • ISS-video-2

  13. Horizon plane

  14. Solar System Orbits to Scale

  15. Inner Orbits From Above:Small Ellipticities

  16. Earth's Orbit

  17. Stars visible at night change as Earth'slocation in its orbit changes

  18. Stars visible at night change as Earth'slocation in its orbit changes What name is given to this set of constellations?

  19. Stars visible at night change as Earth'slocation in its orbit changes The Zodiac

  20. Puzzlah # 14 Consult the diagram of the Earth’s orbit and Zodiacal constellations above. What constellation is the Sun projected against today? [Hint: the Earth moves in the direction of the arrow during the year.] A) Virgo B) Scorpio C) Capricorn D) Gemini

  21. Animation: Sun's Path Along Zodiac

  22. Change in Sun’s “declination”(angular distancefrom celestial equator) caused by polar tilt Key Dates 2014 3/20 Vernal Equinox 6/21 Summer Solstice 9/22 Autumnal Equinox 12/21Winter Solstice

  23. Because of axis tilt, daylight hours vary with date and latitude

  24. Animation: Origin of Seasons • Animation: Variation in Flux of Sunlight

  25. Ex,Supp,Alt

  26. Summary of easily visible motions of celestial objects

  27. Essential tool for disentanglingcelestial motions: Greek geometry Athens, ca 400 BC

  28. Results of Earth’s Spin (Star trail photos)

  29. Results of Earth’s Spin (Star trail photos) Star trails show the "diurnal" motion: the apparent continuous westward motion of the sky caused by the Earth's spin on its polar axis

  30. Are We Stationary or Moving?

  31. Are We Stationary or Moving?

  32. Are We Stationary or Moving?

  33. Both Spin. But which is right?

  34. Both Spin. But which is right?

  35. Earth’s polar axis is tilted withrespect to orbital plane

  36. Because of axis tilt, daylight hours vary with date and latitude

  37. Change in Sun’s “declination”(angular distancefrom celestial equator) caused by tilt

  38. Earth from Moon, Apollo 8