The History and Philosophyof Astronomy (Lecture 4: Middle Ages I)Instructor: Volker BrommTA: Amanda BauerThe University of Texas at AustinAstronomy 350L (Spring 2005)Medieval Astronomy and Cosmology• Middle Ages I (Jan. 27)- Decline of Western (Mediteranean) Civilization- Early Middle Ages (“Dark Ages”): 500 – 1000 AD- Ascendancy of Islamic Astronomy (800 – 1400 AD)- Preservation and transformation of ancient knowledge• Middle Ages II (Feb. 1)- Recovery of European Civilization- High and Late Middle Ages (c. 1000 – 1450 AD)- Setting the Stage for the Copernican Revolution - Recasting of the Ancient TraditionThe Fall of Rome• “Barbarians” (Germanic tribes/Huns) at the gateThe Fall of Rome• “Barbarians” (Germanic tribes/Huns) at the gateThe Fall of RomeQ: Why did it happen?(Edward Gibbon, 1737-94)• Gibbon’s Decline and Fall of theRoman Empire:- decadent society - economical pressure- constant threat of invasion- corrupt governmentThe European Dark Ages• Early Christianity initially hostile towardpagan learning, especially astronomy/astrology• Loss of libraries and ancient texts• Greek language was largely forgottenonly simplified Latin • Life was brutish and short, primitive economic level• a tremendous decline in cultural sophisticationA Rescue Attempt: Boethius (480-524 AD)• “The Last Roman”• Court official underTheoderic, King of theOstrogoths (ruler of post-Roman Italy)• executed for treason• The Consolation of PhilosophyA Rescue Attempt: Boethius (480-524 AD)• His (hyper-ambitious) program:AristotlePlatoGreekLatintranslateLogical works• ran out of time: most texts lost for Latin West!• only rescued Plato text: Timaeus (trans. Calcidius)• (Greek) works of astronomy forgotten for centuries!Kosmas Indikopleustes (6thcent. AD)• Repudiating the idea that Earth is a Sphere!Kosmas Indikopleustes (6thcent. AD)• Very low standard of secular learning!• Re-accept spherical Earth only 500 years later!• Universe is tabernacle!The Ascendancy of Medieval Islam• Emergence of vibrant and tolerant civilization!Islam: The Need for Astronomy• religious requirements:- predict beginning of month- altitude of Sun (hours of prayer)• establish office of muwaqqit(mosque timekeeper)Astronomers respected position in society!The House of Wisdom in Baghdad (9thcent. AD)• Vigorous effort to translate Greek texts into Arabic- Caliph al-Mamun (Abbasid dynasty, 750 – 1258)• Translating Ptolemy:Greek: Syntaxis Arabic: AlmagestPtolemaic System within Islamic AstronomyAlmagest• No fundamental modificationto Aristotelian-Ptolemaic cosmology!• Improvements in precision- building of major observatories!- improved mathematical methods!• Discussion of doubts about Ptolemy!Precision Astronomy: Great ObservatoriesUlugh Beg (d. 1449)Samarkand- Grandson of Tamerlane- Great mural sextantUlugh Beg’s Star Catalogue• first major new catalogueof stars since time ofHipparchus (2ndcent. BC)• high-precision (> 1000 stars)• unknown in EuropeThe Astrolabe: Universal Astro-calculator• invented by Greeks, butperfected by Arabs• measure altitude (height)of stars (or Sun)• predict position of stars/Sun at given timeCritiquing Ptolemy• Averroes (1126-98 AD)• lived in Moorish Andalusia• “The Commentator”of Aristotle• philosophical purist:found contrived modelof Ptolemy (deviation fromuniform spherical motion)inelegantCritiquing Ptolemy• Nasir al-Din al-Tusi (1201-74 AD)• lived in Persia• adviser to Mongolconqueror Hulagu Khan• one of greatest astronomersduring Islamic PeriodAl-Tusi’s Observatory at Maragha• 12 years of intense effort: Planetary Tables (“zij”)Al-Tusi’s Attack on Ptolemy• Copernicus did the same: Did he know of al-Tusi?• eliminate un-Platonic equant with double epicycle!equantdouble-epicycleLegacy of Islamic Astronomy• Preserved ancient Greek astronomy / philosophy• Improved mathematical methods• Diligent observers (astronomical tables)• Attitude towards Ptolemaic Framework:- no fundamental change!- improved precision (Great Observatories)- raising of doubts- elimination of Ptolemaic