PreCopernican Astronomy

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PreCopernican Astronomy

• NOT COVERED IN BOOK

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Summary of Celestial Motions

• Fixed Stars
• Uniform daily motion around the NCP.
• The Sun
• Daily motion around the NCP.
• Eastward motion along the Ecliptic over a year
• The Moon
• Daily motion around the NCP.
• Eastward motion in the Zodiac over a month (From
  day to day Moons own motion is toward the East
  opposite its daily motion)

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Planets in the Sky

• Planets were the Greek wanderers
• Objects that wandered through the
  constellations Mercury, Venus, Mars, Jupiter,
  Saturn (Also Sun Moon)
• Did not know about Uranus and Neptune (cant be
  seen by the naked eye
• Planet Motion
• Daily motions around the NCP.
• Normal eastward motion in the Zodiac

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The Famous Greeks (c. 400 B.C.)
Plato
Aristotle
Hipparchus
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Plato Solar System Description

• Four inviolate assumptions
• Geocentric Everything orbits the Earth
• Earth does not rotate
• Orbits are perfect circles
• Objects move at a uniform speed

Based on Philosophy, Perfection in the Heavens,
and Spherical Symmetry
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Aristotle Empiricist

• Father of Logic after all
• Correctly explained
• Phases of the Moon
• Eclipses (Lunar and Solar)
• Earth casts circular shadow gt Earth Spherical
• Still obeyed Geocentric assumptions

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Hipparchus An Observer

• Naked-eye on Island of Rhodes
• Star catalog, star coordinates, and brightness
  classifications
• Reported Retrograde Motion of planets
• Reversal of the slow, normal (west-to-east)
  motion of the planets among the constellations
• How can geocentric models explain this?

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Retrograde Motion
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Mars Retrograde MotionAugust 2003
Photo by Turkish amateur astronomer Tunç Tezel
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Historical Events

• Alexander the Great conquers everything.
• Center of intellectual thought shifts from Athens
  (Academy) to Alexandria (Library)
• Ptolemy was an Egyptian when Egypt was a
  territory of the Roman Empire

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Ptolemy (c.100 A.D.)
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Ptolemys Model Complex Geocentric

• Kept all four Greek Assumptions (roughly
  speaking)
• Inelegant, awkward, ad hoc, but could explain
  retrograde motion
• Model had epicycles to account for retrograde
  motion

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The Great Interruption

• Much classical knowledge was lost after the fall
  of Rome in c. 400 AD.
• Bubonic plague wipes out 1/4th of Western Europe
  Population
• The rise of Islam c. 750AD led to survival of
  classical learning in Arabic translation
• Systematic translation into Arabic of surviving
  classical texts
• Islamic scholars advanced mathematics
  astronomy, invented algebra, did fundamental
  work in geography, optics, and medicine.

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Rediscovery in Europe

• Spain became the center for translation of Arabic
  texts into Latin in the 11th century.
• Primarily Jewish scholars working between the
  Christian and Islamic worlds.
• Principal centers were Toledo Córdoba.
• Europeans rediscovered their heritage
• Aristotle Ptolemy rediscovered in the 12th
  century
• Christian scholars (Aquinas) reconciled these
  with Christian dogma (13th c.)

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Naming Stars

• Brightest star in constellation Taurus
• Greek name a Taurus
• Arabic name Aldebaran
• Al Debarren
• The Follower
• (of the Pleiades)