The History and Philosophy of Astronomy Lecture 7: Middle Ages. Islam. Presentation

Astronomy 350L (Fall 2006)

The History and Philosophy of Astronomy (Lecture 7: Middle Ages/Islam II)

Instructor: Volker Bromm TA: Jarrett Johnson The University of Texas at Austin

Medieva Med ievall Ast Astron ronomy omy and Cosm Cosmolo ology gy

• Mi Midd ddle le Age Ages s I (S (Sep ep.. 19) 19) - Decl Decline ine of Western Western (Medite (Mediterran rranean) ean) Civiliza Civilization tion (“Dark Ages”): Ages”): 500 500 – 1000 AD AD - Early Middle Ages (“Dark (800 00 – 14 1400 00 AD AD)) - Asce Ascendan ndancy cy of of Islam Islamic ic Astr Astronom onomy y (8 - Preservation and transformation of ancient knowledge

• Mi Midd ddle le Age Ages s II II (Se (Sep. p. 21 21)) - Reco Recovery very of Europe European an Civili Civilizatio zation n and Late Late Middle Middle Ages (c. 1000 1000 – 1450 AD) AD) - High and - Sett Setting ing the the Stage for for the Coperni Copernican can Revolut Revolution ion - Recasting of the Ancient Tradition

Europe Europ e Recovers: Later Middle Ages

(c.. 100 (c 1000 0 – 14 1450 50))

•• Roma Romanes nesque que: : e.g., e.g., Dome Dom ehedral in Speye in S peyer r (1030-1061) Gothic Got hic: : e.g., e.g., Chartres Char tres cathed cat ral (1145-1220)

Europe Europ e Recovers: Later Middle Ages

• Art in the Ag Age e of Ch Chiv ival alry ry

(c.. 100 (c 1000 0 – 14 1450 50))

Europe Europ e Recovers: New Spirit of Exploration

Marco Polo (1254-1324)

Journey to China: 1271-95

Rediscovery of Ancient Knowledge: Arabic Transmission

• mul multipl tiple e sources: sources: e.g. e.g.,, Spain, Spain, Crusade Crusades s

Rediscovery of Ancient Knowledge: - vi via a Moo Moori rish sh Sp Spai ain n • Tr Tran ansl slat atio ions ns:: Arabic Latin • La Late ter: r: di dire rect ctly ly Greek Latin • Tr Tran ansfe sferr of of kn know ow-ho -how: w: - computa tattion - astro rollabe bes s Alhambra, Granada

Rediscovery of Ancient Knowledge: - via Cr Crus usa ades

Siege of Antioch, 1098 AD

• Euro Europe pe becomes becomes aware aware of of high high level level of Islami Islamic c civilization

Rediscovery of Ancient Knowledge: Emergence of the University

Oxford University

• Uni Univers versiti ities: es: A Europe European an Inven Invention tion (12th and 13th cent.) • Objec Objective: tive: Understan Understand d ancient, ancient, redisc rediscovered overed texts!

Structure of Medieval University Seven Sev en lib libera erall Arts Arts (Sep (Septes tes Arte Artes s Lib Libera erales les): ): Triv Triviu ium m

Rhetoric

Logic (Dialectic)

Grammar

Structure of Medieval University Seven Sev en libe liberal ral Arts Arts (Sep (Septes tes Arte Artes s Lib Libera erales les): ): Quad Quadriv riviu ium m

arithmetic

music

geometry

astronomy

Scholasticism: inconsistencies in ancient astronomy • Ari Arist stot otle le and and Pt Ptol olem emy: y: - 500 yea years rs apar apartt in real real tim time e - scho scholasti lastics cs redisco rediscover ver it at same insta instant nt Fiction of unified body of “ancient wisdom”

• But But:: two sys system tems s are are incons inconsist istent! ent! - Arist Aristote otelian lian conc concentr entric ic sphere spheres s vs Ptolemy’s deferent/epicycle system - Ari Aristo stotle tle wan wants ts to expl explain ain real mechanism behind planetary motion (“physics’) - Ptol Ptolemy emy (“mathe (“mathemat matical ical astrono astronomy”) my”) wants wants to predict motions, but does not claim that planets really move according to his constructions!

Adopting Ptolemy’s Almagest: Sacrobosco • Jo John hn of Ho Holy lywo wood od (d. 1256) Sacrobosco

• ta taug ught ht in Par Paris is • wrote De Sp Spha haer era a (S (Sph pher ere) e) • st stan anda dard rd text textbo book ok for for 400 400 yrs • sim simpli plified fied vers version ion of Alm Almage agest st

The Christian Universe: Thomas Aquinas • St. Th Thomas (1225-74) • Do Domi mini nica can n mon monk k • Re Recon conci cile led d Ari Arist stotl otle e with Christian Theology • Summa Theologiae 

The Christian Universe: Thomas Aquinas

Aristotelian cosmology Christian cosmology

The Christian Universe: Dante’s Divine Comedy  • As Astr tron onomy omy = The Theol olog ogy y • Ce Centr ntral al Ea Earth rth bec becom omes es essential ingredient of Christian Theology

The Empy Empyrean rean:: Dant Dante e and Beatrice Beatrice behold behold Paradis Paradise e

Scholastic Critique of Aristotle: Motion of Projectile (Impetus Theory)

• Jean Bu Buridan (14th cent.) • ta taug ught ht in Par aris is • me memb mber er of Nom Nomin inali alist sts s • Buridan’s ass: The Tyranny of Choice Burida dan’ n’s s Ass

Projectile Motion: Aristotle’s Theory • Basic principle: heavy bodies (elements earth or water) are at rest or move straight to center of Earth (= center of universe) sling push

air

???

Center of universe

• To devi deviate ate fro from m Ari Aristo stotel telian ian natural motion: need external influence! • For proj project ectile ile:: infl influenc uence e come comes s from pushed-aside air bubble!

Proj Pr oject ectile ile Motion Motion:: Buridan’ Buridan’s s Th Theor eory y • Basic principle: heavy bodies are at rest or continue to move according to impetus  impetus initially initially imparted to them sling

impetus

gravity

• imp impetu etus s = (modern) (modern) momentu momentum m (Galileo (Galileo,, Newton) Newton) (mass x speed)

• cru crucia ciall step step in allo allowing wing Eart Earth h to move move!!

Scholastic Critique of Aristotle: Demonstrating Possibility of Earth’s Motion

• Nicole Oresme (14th cent.) • ta taug ught ht in Par aris is • pu pupi pill of Bu Buri rida dan n • de demon monst stra rate tes s lo logic gical al possibility of Earth’s motion

Nicole Oresme

Motion of Earth is possible: Nicole Oresme • Idea 1: Earth could move in circles around center of universe! then Earth would be a planet, one among many! Q: What would happen?

Aristotle:

1st Earth

2nd Earth

Two Earth’s would collide: Earth is unique!

center of universe

Motion of Earth is possible: Nicole Oresme • Idea 1: Earth could move in circles around center of universe! then Earth would be a planet, one among many! Q: What would happen?

Oresme:

1st Earth

2nd Earth

two different centers of gravity! Each heavy body (e.g., planet) has its own center of attraction: Earth could be a planet!

Aristotelian Argument against Earth’s Rotation:

• Basic principle: heavy bodies follow natural motion towards center of Earth = cent. of universe

Stone/arrow Observer

Aristotle argued: Stone would be left behind if Earth rotated!

Oresme’s Oresm e’s Argum Argument ent for Earth Earth’s ’s Rotati Rotation: on:

• Basic principle: impetus theory! - stone or arrow has sideways impetus

stone follows Earth

Stone/arrow No rotation:

Observer

With rotation:

Oresme Ores me arg argued ued:: Ston Stone e would would not  not be be left behind if Earth rotated!

Oresme’s Oresm e’s Argum Argument ent for Earth Earth’s ’s Rotati Rotation: on:

• two equivalent ways to understand daily motion of fixed stars! Fixed stars

Earth

A: Earth rotates!

B: Fixed stars rotate!

- Op Opti tica call re rela lati tivit vity: y: both models can explain appearance

A Unive Universe rse witho without ut limit: Nico Nicolaus laus of Cusa Cusa • Cusanus (1401-64 AD) • lived in Southern Germany • was a Cardinal of

Roman Catholic Church • Of Learned Ignorance  (De (D e Docta Docta Ig Igno nora rant ntia ia))

A Unive Universe rse witho without ut limit: Nico Nicolaus laus of Cusa Cusa • Basic principle:

Opposites coincide (become the same) in the process of going to infinity (coinc (coincide identi ntial al opposi oppositor torum) um)

- E.g E.g., ., cur curve ve and str straig aight ht line • But als also: o: Cente Centerr and and circum circumfere ference nce - Coincide in the limit of the absolute smallest

• The real realm m of the abs absolut olute e is God God!! - mat materi erial al unive universe rse canno cannott attain attain this this!!

Universe has no center and no edge! e dge!

Astronomy in the Middle Ages (Scholastic Period) • Reb Rebirth irth of intell intellectu ectual, al, scien scientif tific ic activit activity y • Redisc Rediscovery overy of ancient ancient texts texts (via Arabic transmi transmission) ssion) • Founding of Univers Universities ities (Schola (Scholastic stic Philo Philosophy) sophy) • Rec Recast asting ing of tradit tradition ion at Dawn Dawn of Copernica Copernican n Revol.: Revol.: - Aris Aristot totelian elian-Pto -Ptolema lemaic ic system system incorporated incorporated into into Christian theology opposes Copernicus! - Ne New w th theor eory y of mo motio tion n establ est ablish ishes es pla plausi usibil bilty ty of Earth’s motion crucial precondition for Copernicus!