Aristotle, Galileo, Kepler and Company

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Aristotle, Galileo, Kepler and Company

• Attempts to describe heavenly motion

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Realism vs. Instrumentalism

• Instrumentalism an idea is judged bases on its
  usefulness, regardless of its ultimate
  correctness
• Id, Ego and Superego
• Realism an idea is judges based on the accuracy
  of its description of reality

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Paradigm

• Set of background beliefs that govern allowable
  ideas
• Can change over times in revolutions
• Renaissance God made and governs universe. God
  is all powerful and miracles are possible.
  Universe in unpredictible.
• Modern Paradigm Natural Laws make for a
  predictable universe, no miracles, only natural
  causes

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Aristotles Basic Ideas

• Aristotle constructed his view of the Universe
  based on a intuitive feeling of holistic harmony.
  
• Central to this philosophy was the concept of
  teleology or final causation.
• Objects, being solid like earth, would tend to
  clump together with other solids (earth), so
  objects tend to fall to earth, their natural
  place. Thus, falling is a natural motion.

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Aristotles Basic Ideas

• Universe is perfect and unchanging.
• Contrast with imperfect, changing earth

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Aristotles Universe

• Now all is in harmony, the earth is at the center
  of the universe and the cosmos revolves around us
  in perfect contentment
• Geocentric Cosmology and the Earth is Immobile.
• Stars and planets on perfect crystalline spheres
  that rotate around the Earth.
• Universe is perfect and Changeless

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Pythagorean Constraints

• Mathematics shows universal design and express
  perfection of god
• Universe must follow mathematical Constraints
• All motion is in Circles, the perfect shape
• All motion must take place at a constant rate , a
  reflection of unchanging Heavens
• All motion around a common point

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Problems in Describing Heavenly Motion

• Motion of the Sun
• Daily east to west
• Monthly relative to stars and moon
• What time does the moon rise?
• Yearly from north to south and back (seasons)
• Motion of the planets
• Nightly East to west
• Retrograde motion and variation in brightness
• Temporary backwards motion

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Sense Observations to support Geocentrism

• Stationary earth- no rotation
• we dont feel it move
• No constant wind from east to west
• Arrow goes up and comes down in same place

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• Stationary earth no revolution around sun
• No parallax apparent shift in position due to
  motion of observer
• Could be explained if Universe is very large, or
  if the earth didnt move
• waste of space

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Early Greek Models-- Geocentric

• Earth at the Center immobile
• Sun and all heavenly bodies circle the earth
• Simple circles do not explain retrograde motion

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Early Greek Circles and more circles

• Epicycles and Equants circles revolving around
  an invisible revolving point

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Greek Models Heliocentric
Heraclitus partial heliocentric (sun at center,
earth revolves around sun, all else aroudn the
earth Aristarchus completely heliocentric
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Summary of Greek Models

• All were seen instrumentally
• Aristotle supported geocentric as more reasonable
• Geocentric improved by Ptolomy
• Used over 80 circles
• Gave predictions (sunrise, seasons, etc) accurate
  to about 1

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Situation in the Renaissance

• Ptolomy is still dominant model
• St. Thomas Aquinas worked to unify Catholic
  theology with Aristotle
• Earth (man) at center of the universe logical
  spots for heaven and hell
• Columbus and Magellan navigated oceans using
  Ptolomy

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Situation in the Renaissance

• Copernicus (1475-1543) reintroduces
  Heliocentricism

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Added Information for Copernicus

• Copernicus was Polish cannon (religious man)
• Thought Ptolomy was too awkward God wouldnt
  make such a system
• Neo-Platonism Wanted physical symbol (sun) to
  represent God as the center of the universe
• Calculations were Easier System used 48 circles
  instead of 80, accuracy was no better than for
  Ptolomy
• Book published posthumously. Preface stated it
  was to be seen instrumentally, but Copernicus
  probably though it was real

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Reaction to Copernicus

• Then spake Joshua to the Lord . . . and said in
  the sight of Israel, Sun, stand thou still upon
  Gibeon and thou, Moon, in the valley of Ajalon.
• And the sun stood still, and the moon stayed,
  until the people had avenged themselves upon
  their enemies. . . So the sun stood still in the
  midst of heaven, and hasted not to go down about
  a whole day.
• Joshua 10 12-13 KJV

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Augustines Axiom

• When a demonstrated scientific fact contradicts a
  literal interpretation of scripture, the
  scripture should be interpreted metaphorically
• Was the Copernican Cosmology a demonstrated
  fact?

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Galileo Galilei (1564-1642)

• 1592 Professor of Mathematics at Padua
• Did studies in Astronomy and Engineering
• Designed and built best telescope of the time

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What Galileo Saw With His Telescope

• Mountains and valleys on the moon, not a sphere
  of perfect crystal
• Sunspots on the sun inconsistent with unchanging
  heavens
• Four moons orbiting Jupiter showed that all
  things didnt orbit around the earth

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Galileos Findings

• All these were consistent with Copernicus, and
  not with Aristotle but they were not conclusive
• Conclusive evidence would have been showing
  parallax his telescope wasnt good enough.
• Parallax would have proven that the earth moved
• Parallax wasnt shown until over 200 years later,
  when better telescopes were developed

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Giordano Bruno (1548-1600)

• Dominican monk in Naples
• Bruno defended the heliocentric theory of
  Copernicus. He argued that the universe was
  infinite, that it contained an infinite number of
  worlds, and that these are all inhabited by
  intelligent beings.
• 1592-1600 questioned by inquisition
• Refused to recant, burned at the stake

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Tycho Brahe (1546-1601)

• Danish Royal Astronomer
• Assembled most accurate data on heavenly motion
• Revised and proposed partial heliocentric
  (heraclitus) model

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• Brahes model about as easy to use as Copernican
• Didnt go against Scripture or reason
• Earth still didnt seem to be moving
• Brahe didnt worry about Neoplatonic ideals
• Brahe was a protestant, so inquisition wasnt an
  issue

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Johannes Kepler (1571-1630)

• Worked with Tycho Brahe, and inherited his data
• Protestant mystic and neoplatonist
• Considered all theories to crude for a perfect
  God
• Found Galileos astronomy uninteresting

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Keplers System

• Rejected Pythagorean Constraints of circular
  motion and constant speed
• Planets move at varying speed in elliptical
  orbits around the sun

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Elliptical vs Circular Motion
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Summary of Models

• Ptolomy Earth at center, 80 circles, epicycles
  etc. and accurate to about 1. Very difficult to
  use
• Copernicus Sun at center, 48 circles, epicycles
  etc. and accurate to about 1. Easier to use.
• Kepler Sun at center, 7 ellipses (one for each
  planet), much more accurate and easier to use
  than others. This one is real

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Church and the Astonomers

• Aristotle fit traditional theology, place for
  heaven and hell . .unchanging celestial heavens
• Theology man made in Gods image, so were in
  the center of the universe
• Protestant Reformation
• Attack on authority
• Priesthood of all believers
• Authority comes from Gods Word, not passed
  down through Popes, so words very important

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• Council of Trent April 1546
• No private interpretation of Scripture
• (watch out Galileo)
• Siege Mentality see enemies where there are
  none
• Jesuits founded to defend the Faith
• Result most Catholics and Protestants chose
  conservative approach, resisted heliocentricism
• Many scientists also were conservative and
  resisted Copernician ideas

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And now, A Word from Zukowski