Aristotle, Galileo, Kepler and Aristotle, Galileo, Kepler and CompanyCompany

Attempts to describe Attempts to describe heavenly motionheavenly motion

Realism vs. InstrumentalismRealism vs. Instrumentalism

Instrumentalism: an idea is judged Instrumentalism: an idea is judged bases on it’s usefulness, regardless bases on it’s usefulness, regardless of it’s ultimate correctnessof it’s ultimate correctness Id, Ego and SuperegoId, Ego and Superego

Realism: an idea is judges based on Realism: an idea is judges based on the accuracy of its description of the accuracy of its description of realityreality

ParadigmParadigm

Set of background beliefs that Set of background beliefs that govern allowable ideasgovern allowable ideas Can change over times in “revolutions”Can change over times in “revolutions”

Renaissance: God made and Renaissance: God made and governs universe. God is all powerful governs universe. God is all powerful and miracles are possible. Universe and miracles are possible. Universe in unpredictible.in unpredictible.

Modern Paradigm: Natural Laws Modern Paradigm: Natural Laws make for a predictable universe, no make for a predictable universe, no miracles, only natural causesmiracles, only natural causes

Aristotle’s Basic IdeasAristotle’s Basic Ideas

Aristotle constructed his view of the Aristotle constructed his view of the Universe based on a intuitive feeling Universe based on a intuitive feeling of holistic harmony. of holistic harmony.

Central to this philosophy was the Central to this philosophy was the concept of teleology or final causation. concept of teleology or final causation.

Objects, being solid like earth, would tend Objects, being solid like earth, would tend to clump together with other solids to clump together with other solids (earth), so objects tend to fall to earth, (earth), so objects tend to fall to earth, their natural place. Thus, falling is a their natural place. Thus, falling is a natural motion.natural motion.

Aristotle’s Basic IdeasAristotle’s Basic Ideas

Universe is perfect Universe is perfect and unchangingand unchanging..

Contrast with Contrast with imperfect, imperfect, changing earthchanging earth

Aristotle’s UniverseAristotle’s Universe

Now all is in harmony, the earth is at Now all is in harmony, the earth is at the center of the universe and the the center of the universe and the cosmos revolves around us in perfect cosmos revolves around us in perfect contentment contentment Geocentric Cosmology and the Earth is Geocentric Cosmology and the Earth is

Immobile. Immobile. Stars and planets on perfect crystalline Stars and planets on perfect crystalline

spheres that rotate around the Earth. spheres that rotate around the Earth. Universe is perfect and Changeless Universe is perfect and Changeless

Pythagorean ConstraintsPythagorean Constraints

Mathematics shows universal design Mathematics shows universal design and express perfection of godand express perfection of god

Universe must follow mathematical Universe must follow mathematical ConstraintsConstraints All motion is in Circles, the perfect shapeAll motion is in Circles, the perfect shape All motion must take place at a constant All motion must take place at a constant

rate , a reflection of unchanging rate , a reflection of unchanging HeavensHeavens

All motion around a common pointAll motion around a common point

Problems in Describing Problems in Describing Heavenly MotionHeavenly Motion

Motion of the SunMotion of the Sun Daily east to westDaily east to west Monthly relative to stars and moonMonthly relative to stars and moon

What time does the moon rise?What time does the moon rise? Yearly from north to south and back Yearly from north to south and back

(seasons)(seasons) Motion of the planetsMotion of the planets

Nightly East to westNightly East to west Retrograde motion and variation in Retrograde motion and variation in

brightnessbrightness Temporary backwards motionTemporary backwards motion

Sense Observations to support GeocentrismSense Observations to support Geocentrism

Stationary earth- no rotationStationary earth- no rotation we don’t feel it movewe don’t feel it move No constant wind from east to westNo constant wind from east to west Arrow goes up and comes down in same Arrow goes up and comes down in same

placeplace

Stationary earth – no Stationary earth – no revolution around sunrevolution around sun

No parallax: No parallax: apparent shift in apparent shift in position due to position due to motion of observermotion of observer Could be explained if Could be explained if

Universe is very large, Universe is very large, or if the earth didn’t or if the earth didn’t movemove

““waste of space”waste of space”

Early Greek Models-- GeocentricEarly Greek Models-- Geocentric

Earth at the Earth at the Center – Center – immobileimmobile

Sun and all Sun and all heavenly bodies heavenly bodies circle the earthcircle the earth

Simple circles Simple circles do not explain do not explain retrograde retrograde motionmotion

Early Greek: Circles and more circlesEarly Greek: Circles and more circles

Epicycles and Epicycles and Equants: circles Equants: circles revolving around an revolving around an invisible revolving invisible revolving pointpoint

Greek Models: HeliocentricGreek Models: HeliocentricHeraclitus – partial heliocentric (sun at center, earth revolves around sun, all else aroudn the earth

Aristarchus – completely heliocentric

Summary of Greek ModelsSummary of Greek Models

All were seen All were seen instrumentallyinstrumentally

Aristotle supported Aristotle supported geocentric as more geocentric as more reasonablereasonable

Geocentric improved Geocentric improved by Ptolomyby Ptolomy Used over 80 circlesUsed over 80 circles Gave predictions Gave predictions

(sunrise, seasons, etc) (sunrise, seasons, etc) accurate to about 1%accurate to about 1%

Situation in the RenaissanceSituation in the Renaissance

Ptolomy is still Ptolomy is still dominant modeldominant model St. Thomas Aquinas St. Thomas Aquinas

worked to unify Catholic worked to unify Catholic theology with Aristotletheology with Aristotle

Earth (man) at center of Earth (man) at center of the universe: logical the universe: logical spots for heaven and spots for heaven and hellhell

Columbus and Magellan Columbus and Magellan navigated oceans using navigated oceans using PtolomyPtolomy

Situation in the RenaissanceSituation in the Renaissance

Copernicus (1475-Copernicus (1475-1543) reintroduces 1543) reintroduces HeliocentricismHeliocentricism

Added Information for CopernicusAdded Information for Copernicus Copernicus was Polish cannon (religious Copernicus was Polish cannon (religious

man)man) Thought Ptolomy was too awkward; God Thought Ptolomy was too awkward; God

wouldn’t make such a systemwouldn’t make such a system Neo-Platonism: Wanted physical symbol Neo-Platonism: Wanted physical symbol

(sun) to represent God as the center of the (sun) to represent God as the center of the universe universe

Calculations were Easier: System used Calculations were Easier: System used 48 circles instead of 80, accuracy was 48 circles instead of 80, accuracy was no better than for Ptolomyno better than for Ptolomy

Book published posthumously. Preface Book published posthumously. Preface stated it was to be seen instrumentally, but stated it was to be seen instrumentally, but Copernicus probably though it was realCopernicus probably though it was real

Reaction to CopernicusReaction to Copernicus

““Then spake Joshua to the Lord . . . and Then spake Joshua to the Lord . . . and said in the sight of Israel, Sun, stand thou said in the sight of Israel, Sun, stand thou still upon Gibeon; and thou, Moon, in the still upon Gibeon; and thou, Moon, in the valley of Ajalon.valley of Ajalon.

““And the sun stood still, and the moon And the sun stood still, and the moon stayed, until the people had avenged stayed, until the people had avenged themselves upon their enemies. . . So the themselves upon their enemies. . . So the sun stood still in the midst of heaven, and sun stood still in the midst of heaven, and hasted not to go down about a whole day.”hasted not to go down about a whole day.”

Joshua 10: 12-13 Joshua 10: 12-13 KJVKJV

Augustine’s AxiomAugustine’s Axiom

When a demonstrated When a demonstrated scientific fact scientific fact contradicts a literal contradicts a literal interpretation of interpretation of scripture, the scripture scripture, the scripture should be interpreted should be interpreted metaphoricallymetaphorically

Was the Copernican Was the Copernican Cosmology a Cosmology a “demonstrated fact”?“demonstrated fact”?

Galileo Galilei (1564-1642) Galileo Galilei (1564-1642)

1592 Professor of 1592 Professor of Mathematics at Mathematics at PaduaPadua

Did studies in Did studies in Astronomy and Astronomy and Engineering Engineering

Designed and built Designed and built best telescope of best telescope of the timethe time

What Galileo Saw With His TelescopeWhat Galileo Saw With His Telescope

Mountains and valleys on the moon, not a Mountains and valleys on the moon, not a sphere of perfect crystalsphere of perfect crystal

Sunspots on the sun: inconsistent with Sunspots on the sun: inconsistent with unchanging heavensunchanging heavens

Four moons orbiting Jupiter showed that all Four moons orbiting Jupiter showed that all things didn’t orbit around the earththings didn’t orbit around the earth

Galileo’s FindingsGalileo’s Findings

All these were consistent with Copernicus, All these were consistent with Copernicus, and not with Aristotle – but they were not and not with Aristotle – but they were not conclusiveconclusive

Conclusive evidence would have been Conclusive evidence would have been showing parallax– his telescope wasn’t good showing parallax– his telescope wasn’t good enough.enough.

Parallax would have proven that “the earth Parallax would have proven that “the earth moved”moved”

Parallax wasn’t shown until over 200 years Parallax wasn’t shown until over 200 years later, when better telescopes were developedlater, when better telescopes were developed

Giordano Bruno (1548-1600)Giordano Bruno (1548-1600) Dominican monk in NaplesDominican monk in Naples Bruno defended the heliocentric Bruno defended the heliocentric

theory of Copernicus.theory of Copernicus. He He argued that the universe was argued that the universe was infinite, that it contained an infinite, that it contained an infinite number of worlds, and infinite number of worlds, and that these are all inhabited by that these are all inhabited by intelligent beings. intelligent beings.

1592-1600 –”questioned” by 1592-1600 –”questioned” by inquisitioninquisition

Refused to recant, burned at Refused to recant, burned at the stakethe stake

Tycho Brahe (1546-1601)Tycho Brahe (1546-1601)

Danish Royal Danish Royal AstronomerAstronomer

Assembled most Assembled most accurate data on accurate data on heavenly motionheavenly motion

Revised and Revised and proposed partial proposed partial heliocentric heliocentric (heraclitus) model(heraclitus) model

Brahe’s model about as easy to use as Brahe’s model about as easy to use as CopernicanCopernican

Didn’t go against Scripture or reason Didn’t go against Scripture or reason Earth still didn’t seem to be movingEarth still didn’t seem to be moving

Brahe didn’t worry about Neoplatonic Brahe didn’t worry about Neoplatonic idealsideals

Brahe was a protestant, so inquisition Brahe was a protestant, so inquisition wasn’t an issuewasn’t an issue

Johannes Kepler (1571-1630)Johannes Kepler (1571-1630)

Worked with Tycho Worked with Tycho Brahe, and inherited his Brahe, and inherited his datadata

Protestant mystic and Protestant mystic and neoplatonistneoplatonist

Considered all theories to Considered all theories to crude for a perfect Godcrude for a perfect God

Found Galileo’s Found Galileo’s astronomy astronomy “uninteresting”“uninteresting”

Kepler’s SystemKepler’s System Rejected Pythagorean Constraints of Rejected Pythagorean Constraints of

circular motion and constant speedcircular motion and constant speed Planets move at varying speed in Planets move at varying speed in

elliptical orbits around the sunelliptical orbits around the sun

Elliptical vs Circular MotionElliptical vs Circular Motion

Summary of ModelsSummary of Models

Ptolomy: Earth at center, 80 circles, Ptolomy: Earth at center, 80 circles, epicycles etc. and accurate to about 1%. epicycles etc. and accurate to about 1%. Very difficult to useVery difficult to use

Copernicus: Sun at center, 48 circles, Copernicus: Sun at center, 48 circles, epicycles etc. and accurate to about 1%. epicycles etc. and accurate to about 1%. Easier to use.Easier to use.

Kepler: Sun at center, 7 ellipses (one for Kepler: Sun at center, 7 ellipses (one for each planet), much more accurate and each planet), much more accurate and easier to use than others. This one is “real”easier to use than others. This one is “real”

Church and the AstonomersChurch and the Astonomers

Aristotle fit traditional theology, place for Aristotle fit traditional theology, place for heaven and hell . .unchanging celestial heaven and hell . .unchanging celestial heavensheavens

Theology: man made in God’s image, so Theology: man made in God’s image, so we’re in the center of the universewe’re in the center of the universe

Protestant Reformation: Protestant Reformation: Attack on authorityAttack on authority Priesthood of all believersPriesthood of all believers Authority comes from “God’s Word”, not passed Authority comes from “God’s Word”, not passed

down through Popes, so words very importantdown through Popes, so words very important

Council of Trent: April 1546Council of Trent: April 1546 No private interpretation of Scripture No private interpretation of Scripture

(watch out Galileo)(watch out Galileo) Siege Mentality – see enemies where Siege Mentality – see enemies where

there are nonethere are none Jesuits founded to defend the FaithJesuits founded to defend the Faith

Result: most Catholics and Result: most Catholics and Protestants chose conservative Protestants chose conservative approach, resisted heliocentricismapproach, resisted heliocentricism

Many scientists also were Many scientists also were conservative and resisted conservative and resisted Copernician ideasCopernician ideas