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1. Astronomy The study of the motion of the heavens.
4. The Big Horn Medicine Wheel: Located in the Big Horn Mountains about 45 miles west of Sheridan, Wyoming, this is a sacred site to many Plains tribes, including the Absaroke, Blackfoot, Lakota, and Cheyenne; it is made of stones and is approximately 70 feet in diameter.
5. The Greeks: Observations Give Rise to . Science
7. OK, if we are on a spherical Earth .. How Can We Know How Big It Is?
11. Pythagorean Universe time: about 550 bc
first recorded attempt at rational explanation of heavens
formed foundation for Greek astronomy
12. Philosophical Ideas The heavens represent perfection.
The circle is the perfect shape.
All heavenly motions must be circular.
13. Pythagorean Model stars reside on stellar sphere
stellar sphere rotates about axis in 23 hours 56 minutes
Sun follows path called ecliptic going once around in one year
accounts for most observations!!
25. Ptolemys Epicycles
26. Ptolemys Epicycles
27. Ptolemys Epicycles
28. Ptolemys Epicycles
29. Ptolemys Epicycles
30. Ptolemys Epicycles
31. Ptolemys Epicycles
32. Ptolemys Epicycles
33. Ptolemys Epicycles
34. Ptolemys Epicycles
35. Ptolemys Epicycles
36. Ptolemys Epicycles
37. Ptolemys Epicycles
38. Ptolemys Epicycles
39. Ptolemys Epicycles
40. Ptolemys Epicycles
41. Ptolemys Epicycles
42. Ptolemys Epicycles
43. Ptolemys Epicycles
44. Ptolemys Epicycles
45. Ptolemys Epicycles
46. Ptolemys Epicycles
47. Ptolemys Epicycles
48. Ptolemys Epicycles
49. Ptolemys Epicycles
50. Ptolemy to the Renaissance Ptolemys work kept alive by Arab astronomers
last major incarnation in 13th c
DOMINATED FOR NEARLY 1500 YEARS!
52. The Copernican Model heliocentric (sun-centered)
stars are very far away
Earth rotates on axis
Earth revolves around Sun
53. Old model Copernicus did not like.Old model Copernicus did not like.
59. Epicycles? Problem: Copernicus still could not predict the planets positions accurately with circular orbits.
Solution: Re-introduce epicycles!
Question: Is this any simpler?
60. Tycho Brahe (1546-1601) born just after publication of Copernicus work (1543)
worlds best naked-eye astronomer
created an enormous catalog of exact planetary positions night after night
Danish Nobleman
a bit of an eccentric fellow!!
62. Tychos Work built first modern observatory
amassed records of planetary positions from 1576 to 1591
observations were 2.5 times more accurate than any previous records
devised his own model of the Universe
65. Data Driven Models used Tychos library of observational data
let observational records (data) dictate the orbits instead of philosophy
found non-circular orbits
planets out of orbital plane
A planets speed depends on distance
68. Orbital Eccentricity
69. What is the shape of Earths orbit around the Sun? Earth, e = 0.017
78. THIRD LAW The size of the orbit determines the period of revolution
planets that orbit near the Sun orbit faster than planets that are far from the Sun
80. Review One of the consequences of Keplers third law is that
Jupiter takes longer to orbit the Sun than does the Earth.
planets near the Sun take longer to go once around the Sun.
Earth is moving faster when close to the Sun.
83. The hammer and the feather
95. Newton observed: all objects fall at the same rate near the Earth
orbital motion is just high speed falling
98. LAW OF GRAVITY Describes mathematically how the strength of gravitational attraction depends on mass and separation.
99. HUGE POINT: Newton was able to start with the law of gravity and show that Keplers laws were an inevitable consequence!
The physics dictates the orbits!!!!!
