Cosmology in the Middle Ages

ASTRONOMY 9: HISTORYOF COSMOLOGY Handout #12 Cosmology in the Middle Ages I. Early Middle Ages (approx. 200 1200 AD) Background - Rise in power of Christianity as state religion - Instituted b?- E~nperorConstanti~le (324 AD) - Roman Empire divided into 13:est (Latin) and East (Greek, Byzantine) - ,Time of great tur~noil(invasion. social decay. corruption ...) - Attempts to repulse Gernlanic and Persian invaders fail; Rome falls in 400s, start of European "Dark Ages" - Catastrophic, fatalistic world-views mirrored in salvational themes of Christianity Greek curiosity about nature and love for reason are lost Natural philosophy no longer of interest. concern onl?- with abstract theological questions l:er?; few Greek writings survive Plato's Timaeus still widely read, also enc?-clopedic works of Latin compilers (Pliny. IlIacrobius. Capella, Chalcidius) Literal interpretation of scripture generally the final authority on cosmology Scholarly works all in Latin, knowledge of Greek fades Loss of Greek knowledge near total; from about 300 1000 AD, no st "educated" western Europeans believe in flat Earth! Neo-Platonis~ngenerally dominates during this period St. Augustine (334 43U) - Leads a wild, pleasure-seeking life until age 31. then adopts Christianit?- after tr?-ing man?other philosophies - Philosophy seen as mere handmaiden to theology, not a distinct path to truth - Strongly influenced by Platonic ideas - Division of world into For~ns vs. imperfect, shadowy reality, parallels the Christian "Fall': from grace - Plato's ideas wedded to Christian dogma - The Confessions: a~nplifies Plato's distrust of knowledge gained through the senses - Curiosity about the world, knoaledge for its own sake, seen as an inherently sinful pleasure - Ideas further amplified by Augustine's follomrers St. Lactantius - Demolishes "pagan" idea of spherical Earth in Dinine Institutions (written 30% 323) - Earth believed flat for first time in almost lUU0 years! - Argues against possibility of the antipodes Cosmas - First detailed description of early medieval cos~nological s?-stem. in Christian Topography (written 535 547) - Cosmos as a giant Tabernacle r I\tuch like earlier BabylonianlHebren, views r Earth as flat rectangle or disc at the bottom of the universe r Cos~naswas widel?- traveled, should ha\-e known better! r Earth surrounded by waters, also celestial waters above r Heavens are not spherical because Isaiah says God "laid them out like a tent" r Earth is tilted so the sun can go literally "down" r Tabernacle divided into two Aristotelian zones by firmament r Angels carry stars daily below the firmament Philoponus (6th c.) - Argues against the c o ~ l l ~ l labuse o ~ i of scriptures to prove non-spherical heavens - Ideas have little influence on dominant Church Isidore (570 636) - Bishop in western Church - Also mentions spherical heavens and earth, going against the orthodosy Bede (appros. 673 735, English monli) - Another unorthodox teacher of spherical Earth - Moves Earth from cos~llic bottom back to center - Influenced by Pliny Virgil or Fergil (8th c., Irish ecclesiastic) - ,Threatened mritli expulsion from Church for teaching of spherical Eartli - But not much happens; co~iden~nation of cos~llologicalheresy not at all strict Gerbert - Noted scliolar and astronomer, becomes Pope Sylvester I1 in 999 AD - Spherical Eartli n o r firmly reinstated Immutability of tlie Heavens - Like Aristotle, believed in perfect, unchanging celestial realm for 1LIoon and above - Appearance of supernovae in 1006 and 1054 barely even noted, though 1006 as bright as quarter Moon! - As evidence of celestial change, clashed with medieval viorld-view - Chinese astronomy reached high-point, left records of many celestial events including the SNe By 1000, European knowledge roughly same as 500 BC Greece! 11. Cosmic I~inovatio~i in Arabia (approx. 7UU 125U AD) Preservation and translation of man?- important Greek works (Ptolemy, Aristotle. Euclid, ...) Significant contributions to mathematics (algebra, numerals, sin function, ...) Re-introduction of Greek texts to Europe via Islanlic Spain starting in 1200s Sparked rebirth of scientific curiosity in Europe at end of Middle Ages Built large, organized observatories for new tables of planetary motion A) Adalusian school (Iberian peninsula) Followers of Aristotle's physics: uniform, geocentric, circular motion is only natural possibility Rejected Ptolemaic equant (non-uniform), epicycles and eccentric (not geocentric) as against physical principles Reverted to Aristotelian model with concentric spheres Predictions for planets off by up to 21'1 B) hfaraglia school (Persia) Desired to improve accuracy of Ptolemaic model with new data and mathematical tricks alLTusi ( d . 1274) invented 'Tusi couple - Combination of two circles. one smaller inside tlie other - Can produce variety of motion, even linear! Ptolemy's eccentric and equant replaced with Tusi couples Back to uniform circular motion, w-ith little loss of accuracy 111. Late I\tiddle Ages and Early R.enaissance (approx. 12UU 15UU) By mid 1200s, translations of Aristotle and Ptolem?- come to Europe 7-ia Arabia and Spain Philosophers comnlent on ancient Greeks, add few- new ideas Aristotle's influence eclipses Plato's St. Thomas Aqunias ( l 2 2 i 1274) - Marriage of Aristotelian ideas and Christian dogma Revelation still nlost important source of knowledge, but natural philosophy recognized as a distinct path to truth, followed w-hen not directly contradicting scripture - Aristotelian physics instituted as dogma, not challenged - Believed Aristotle already contained all that could be know-n about the world, nothing left to discover! - Problems uniting .iristoile with Christianit?-: A) Eternal vs. created cosmos B) Only one world a limit on God's power? Roger Bacon (1214 1294) - Unlike most, did not follomr Aristotle as dogma - Stressed use of experiment as path to truth - Establishment of scientific method - Iniprisoned for tw-o years for prornoting "dangerous novelties" Dante (approx. 1300) - Divine Comedy presents dominant medie\-a1 view of cosmos - Hierarchical chain of being, walled-in, finite cosmos - Aristotelian lunary/sub-lunary dil-ision subdivided into man?- concentric shells - Outer shell is most perfect, angelic; Lucifer a t center of Earth Nicolas of Oresme (1323 1382, France) - Wrote Book of the Heanens and the World - Familiar with Heraclides' idea of rotating Earth - Notes rclatiuc nature of notion - Argues rotation of Earth more natural than rotation of heavens! - Refutes his own ideas at the end of the work - . . . . . Nicolas of Cusa (1401 1464, France) - Argues for unbounded, eternal universe in On Learned Ignorance - Earth moves! - Forced to w-rite apolog?., quotes ancient philosophers Regiomonta~~us (1436 14i6) - Completes Peuerbach's translation of Ptolemy's Almagest from original Greek - Discovers errors up to 2' in planetary motions. eclipse ends one hour early Colunlbus (1492 trans-Atlantic voyage) - Did not have to convince anyone of spherical Earth (fiction invented by American writer TVashington Irving) - Knea of accurate 9th c. Arabic conlputation of circumference - Got value 25% too small by assuming Arabic mi = Ronlan mi - Wrong Ptolemaic geography, thought Asia extended far east - Used to justify vo?-age - Europe not a t cosmic center