Models of the Solar System, Gravitation and the motion of the Planets A.K.A DEAD WHITE GUYS WEEK! 1/28/14

Transcription

1 Models of the Solar System, Gravitation and the motion of the Planets A.K.A DEAD WHITE GUYS WEEK! 1/28/14

2 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.

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

4 Pythagorean Universe time: about 550 bc first recorded attempt at rational explanation of heavens formed foundation for Greek astronomy

5 Philosophical Ideas The heavens represent perfection. The heavens are immutable. The circle is the perfect shape. All heavenly motions must be circular.

6 Pythagorean Model stars reside on stellar sphere stellar sphere rotates about axis once a day Sun follows path called ecliptic going around Earth once in one year accounts for most observations!!...but not all

7 BUT - THERE WAS A COMPLICATION. There were stars that appeared to move across the sky without staying in their respective constellations WANDERING STARS (Greek word for wanderer is planete`)

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21 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.

22 Planets were often called wandering stars because they seem to slowly move from one constellation to the next. East South West

23 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.)

24 Ptolemy tried to create a model that would account for retrograde motion.

25 Ptolemy s Epicycles Epicycle Deferent Earth

26 Ptolemy s Epicycles

27 Ptolemy s Epicycles

28 Ptolemy s Epicycles

29 Ptolemy s Epicycles

30 Ptolemy s Epicycles

31 Ptolemy s Epicycles

32 Ptolemy s Epicycles

33 Ptolemy s Epicycles

34 Ptolemy s Epicycles

35 Ptolemy s Epicycles

36 Ptolemy s Epicycles

37 Ptolemy s Epicycles

38 Ptolemy s Epicycles

39 Ptolemy s Epicycles

40 Ptolemy s Epicycles

41 Ptolemy s Epicycles

42 Ptolemy s Epicycles

43 Ptolemy s Epicycles

44 Ptolemy s Epicycles

45 Ptolemy s Epicycles

46 Ptolemy s Epicycles

47 Ptolemy s Epicycles

48 Ptolemy s Epicycles

49 Where is retrograde motion occurring? Planet s Path Ptolemy s Epicycles

50 Ptolemy s Epicycles Where is retrograde motion? Planet s Path

51 Mars retrograde Motion (Ptolemic View)

52 On the Ptolemaic system: A system of this sort seemed neither sufficiently absolute nor sufficiently pleasing to the mind. --Copernicus Copernicus developed the first Sun centered model of the Solar System or Universe. He was a priest and a lawyer.

53 Mars retrograde motion (Copernican View) 53

54 Mars retrograde motion (Copernican View)

55 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)

56 Tycho Brahe ( ) Had artificial wooden and silver noses (lost his nose in a duel) Rumored to have died when his bladder burst The world s best naked eye astronomer - he did not use a telescope!!

57 Brahe s observations of Supernova Brahe observed SN 1572 Proved that this object was in the realm of the stars -- the heavens do change!

58 Tycho showed the Supernova was in the realm of the heavens using something called PARALLAX

59 Scientists use parallax to measure distances.

60 Parallax Brahe proved the SN was not in Earth s atmosphere by parallax When viewing an object from different positions, one sees the object in different positions relative to things behind it The variation in angle when viewing an object from two different positions is called parallax The further the object, less parallax

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62 Parallax Angle 62

63 Parallax If distance is measured in parsecs then d = 1 PA Where PA is the parallax angle, in arcsec NOTE: The distance from the Sun to the Earth is called the Astronomical Unit (AU) A parsec= AU 63

64 Lecture Tutorial(s): The Parsec (p. 37) Parallax & Distance (p. 41) 64