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GE 150 Astronomy

GE 150 Astronomy. Week #5 February 14, 2013. Science in the News. Asteroid flyby: 50 meters wide Closest Approach: Feb 15, 2:25 PM EST 17,150 miles Science.nasa.gov Live broadcast @ 2 PM. Exam Results. Average was 41 +/- 6 B- Printed exams available next week.

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GE 150 Astronomy

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  1. GE 150 Astronomy Week #5 February 14, 2013

  2. Science in the News • Asteroid flyby: 50 meters wide • Closest Approach: • Feb 15, 2:25 PM EST • 17,150 miles • Science.nasa.gov • Live broadcast @ 2 PM

  3. Exam Results • Average was 41 +/- 6 • B- • Printed exams available next week

  4. Which of the following groups of Moon phases can be above the horizon at 4AM? • Full Moon, Waning Crescent, and New Moon • New Moon, First Quarter, and Waxing Gibbous • Waxing Gibbous, Full Moon, Waning Gibbous • Waxing Crescent, Third Quarter, Waxing Gibbous • None of the above phases are visible at 4 AM

  5. Which of the following describes one reason that the northern and the southern hemispheres have different seasons at the same time? • The energy received at Earth from the Sun changes throughout the year providing more energy to one hemisphere than the other. • The Earth is closer to the Sun during summer in the southern hemisphere and is farther from the sun during winter in the northern hemisphere. • The Earth is tilted, so the Sun is closer to one hemisphere than the other, which causes one hemisphere to be in winter and the other in summer. • During the time of the year when the Sun is high in the sky in the northern hemisphere it will be low in the sky in the southern hemisphere. • None of the above

  6. 9 PM 3 AM 3 PM West East • At what time will Star B be located high in the Northwestern sky? • 11:00 pm • 9:00 pm • 11:00 am • 6:00 am • 6:00 pm

  7. Imagine that Earth moved 1 million miles closer to the Sun during its orbit than it currently does, and 6 months later it moved 1 million miles further away than it currently does. How would this affect the seasons? • We would no longer experience a difference between the seasons. • We would continue to experience seasons in essentially the same way we do now. • We would still experience seasons, but the difference would be much more noticeable. • We would still experience seasons, but the difference would be much less noticeable.

  8. Imagine you see Mars very low in the west at 3am. Six hours earlier what direction would you face (look) to see Mars when it was highest in the sky? • toward the north • toward the south • toward the east • toward the west • directly overhead

  9. Motions of the Planets

  10. Cosmogony • A cosmogony is theory about ones place in the universe. • A geocentric cosmogony is a theory that proposes Earth to be at the center of the universe. • A heliocentric cosmogony is a theory that proposes the Sun to be at the center of the universe.

  11. Which is the geocentric cosmogony and which is the heliocentric cosmogony? geocentric (Earth-centered) heliocentric (Sun-centered)

  12. Pythagorean Universe • Time: about 550 BCE • First recorded attempt at rational explanation of heavens • Formed foundation for Greek astronomy

  13. Philosophical Ideas • The heavens represent perfection. • The heavens are immutable. • The circle is the perfect shape. • Therefore: all heavenly motions must be circular.

  14. Pythagorean Model • Stars reside on stellar sphere • Stellar sphere rotates about an axis in 23 hours 56 minutes • Sun follows a path called the ecliptic, going around Earth once in one year • Accounts for most observations!!

  15. North Star Stellar Sphere Axis of Rotation How the Greeks modeled the heavens

  16. Polaris Northern Horizon

  17. North Star Stellar Sphere Axis of Rotation How the Greeks modeled the heavens

  18. Planets • “Special” stars appeared to move across the sky without staying in their respective constellations • WANDERING STARS • (Greek word for wanderer is planete) • Mercury • Venus • Mars • Jupiter • Saturn • Earth was not considered a planet

  19. Everything revolves around the Earth on tilted “crystalline spheres” Geocentric Model

  20. Philosophical Ideas • The heavens represent perfection. • The heavens are immutable. • The circle is the perfect shape. • All heavenly motions must be circular • From Plato’s “dictum” - all movements in the heavens can be explained by “uniform circular motion”

  21. BUT - There was a COMPLICATION ….

  22. Planets were called wandering stars because they appeared to slowly move East West South

  23. Prograde and Retrograde Motion • Prograde Motion (normal motion) – The apparent West to East motion of objects (over many nights) as compared to the stationary background stars.

  24. Rising and Setting

  25. Prograde and Retrograde Motion • Prograde Motion (normal motion) – The apparent West to East motion of objects (over many nights) as compared to the stationary background stars. • Retrograde Motion - The apparent East to West motion of objects (over many nights) as compared to the stationary background stars.

  26. Planets were called wandering stars because they appeared to slowly move East West South

  27. Prograde and Retrograde Motion • Moon and Sun: from one day to the next the motions of both the Moon and the Sun against the background stars are west-to-east (Prograde) • Planets: from one day to the next motions of the planets can be either Prograde or Retrograde relative to the stars (more to follow) However: the daily/nightly motions are similar to stars

  28. Retrograde MotionLecture Tutorial p99-100 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. 2nd Edition 97-98

  29. A planet moving in retrograde motion will, over the course of one night with respect to the stars, appear to • move east to west. • move west to east. • not move at all, as planets do not move with the stars. • move randomly, as planets move differently than the stars.

  30. A planet is moving in retrograde motion. Over the course of several nights, how will the planet appear to move relative to the background stars? • east to west • west to east • It will not move at all, as planets do not move with the stars. • It will move randomly, as planets move differently than the stars.

  31. How many days was this planet in retrograde motion? a) 10 b) 12 c) 15 d) 17 e) 32

  32. On which date would the planet appear to rise in the west? a) March 1 b) March 31 c) April 5 d) April 12 e) Never

  33. Retrograde Motion • Models of the Universe MUST adequately describe this retrograde motion!!!

  34. The astronomer must try his utmost to explain celestial motions by the simplest possible hypothesis; but if he fails to do so, he must choose whatever other hypotheses meet the case. -Ptolemy of Alexandria (140 A.D.)

  35. Ptolemy was : Polish Danish Italian German Greek

  36. Ptolemy tried to create a model that would account for retrograde motion. He placed the planets in orbits (deferents) on orbits (epicycles) all around the Earth

  37. Ptolemy’s Epicycles Epicycle Planet Deferent Earth Sun

  38. Ptolemy’s Epicycles

  39. Ptolemy’s Epicycles Where is retrograde motion occurring? Planet’s Path

  40. On the Ptolemaic system: • “A system of this sort seemed neither sufficiently absolute nor sufficiently pleasing to the mind.” • --Copernicus • (ca 1530)

  41. Why heliocentric NOW (16th Century)?? • Renaissance • Art • Literature • Medicine • Exploration

  42. Copernicus (1473 – 1543 AD) was : Polish Danish Italian German Greek

  43. Copernicus (1473 – 1543 AD) is known for : First observations of the sun The first comprehensive sun centered model of the solar system The world’s best naked-eye astronomical observations in history Creating first a theoretical model to explain planetary motions Creating first a theoretical model for explaining gravity

  44. Copernicus (1473 – 1543 AD) Probably died a virgin Was a priest and lawyer Had artificial wooden and silver noses Rumored to have died of a bladder burst Was labeled a heretic by the church

  45. Retrograde motion is an apparent motion caused when one planets moves from being behind another planet to being in front of the other planet. Copernicus devised the first comprehensive heliocentric cosmogony to successfully explain retrograde motion

  46. Let’s watch a movie of this motion. Copernicus devised the first comprehensive heliocentric cosmogony to successfully explain retrograde motion

  47. The Real Motion of the Planets link

  48. To demonstrate that the appearances are saved by assuming the Sun at the center and the Earth in the heavens is not the same thing as to demonstrate that in fact the Sun is in the center and the Earth in the heavens. I believe that the first demonstration may exist, but I have grave doubts about the second. --Cardinal Bellarmine (1615)

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