Ch. 4 Medieval Latin Astronomy

Ch. 4 Medieval Latin Astronomy

Chronology of Medieval Latin Astronomy Burning of library at Alexandria 400 AD 600 800 1000 1200 1400 Sack of Rome Macrobius, Commentary on Dream of Scipio MartianusCapella, Nuptials Philology & Mercury Boëthius, Consolation of Philosophy Venerable Bede, On the Divisions of Time; computus Fall of Toledo to Christians Bologna first university Gerard of Cremona: Latin trans. Almagest, Toledo Tables University of Paris Sacrobosco, Treatise on Sphere Thomas Aquinas, Summa Theologica ProfatiusJudaeus: astrolabe quadrant Anon., Theory of the Planets Buridan, Oresme: impetus Gutenberg Bible (movable type) Peurbach, Regiomontanus: New Theory of the Planets, Epitome Bernhard Walther: observatory Fall of Constantinople to Turks Copernicus, On the Revolutions Reinhold, Prutenic Tables

Early Latin Astronomy

MartianusCapella, Nuptials of Philology and Mercury • Elaborate allegory from early fifth century AD about the courtship of Philology (personifying learning and having been made immortal by the gods) by Mercury (personifying intelligent and profitable pursuit) • First two books accompanied by seven more dedicated to the liberal arts, handmaidens to the bride: Grammar Dialectics (metaphysics and logic) Rhetoric Geometry Arithmetic Astronomy Music (including poetry) Early Latin Astronomy

MartianusCapella, Nuptials of Philology and Mercury • Referred to by one modern commentator as “… an immense mass of learning, but the materials are ill-selected, ill-arranged, and ill-digested, though from amidst much that is dull and frivolous, we can occasionally extract curious and valuable information ...” • Was much admired during the Middle Ages and frequently copied (by hand, of course!) • Consequently accumulated a vast number of copying errors, with sometimes interesting results (next slide) • Originally included idea attributed to Heraclides that Mercury and Venus go around Sun, not Earth; quoted by Copernicus Early Latin Astronomy

MartianusCapella, Nuptials of Philology and Mercury Mercury and Venus’s orbits intersect! Early Latin Astronomy

Macrobius, Commentary on Cicero’s ‘Dream of Scipio’ • Included handbook on astronomy • Cosmology presented based on Plato and Pythagoreans – number as basis • Spherical Earth with size according to Eratosthenes, seven planetary spheres, celestial sphere • Placement of Sun ambiguous Early Latin Astronomy

Macrobius, Commentary on Cicero’s ‘Dream of Scipio’ Universe with Earth at center, seven planetary spheres, and celestial sphere divided into twelve houses of zodiac Early Latin Astronomy

Macrobius, Commentary on Cicero’s ‘Dream of Scipio’ Diagram of solar eclipse Diagram of lunar eclipse Early Latin Astronomy

Boëthius, Consolation of Philosophy • Written while under house arrest just prior to his execution for treason by order of Theodoric the Great, King of the Ostrogoths • Is dialogue between author and Philosophy, personified as wise and compassionate lady • Has themes of transitory nature of fame and wealth, wheel of Fortune affecting everyone; consolation found in things of the mind, knowledge that God is the source of all good Early Latin Astronomy

Boëthius, Consolation of Philosophy • Has been described as “thesingle most important and influential work in the West on Medieval and early Renaissance Christianity, and is also the last great Western work that can be called Classical” (Wikipedia) • Was widely copied, edited, translated, and commented upon throughout the Middle Ages Early Latin Astronomy

Boëthius • Apart from Consolation, aimed at preserving classical knowledge and especially Aristotle and Plato by translating Greek into Latin with comments • Plan largely unfulfilled; covered mostly mathematics and logic  influenced Scholastics in universities • Organization of mathematical studies into what later became the quadrivium– arithmetic, harmony, geometry, and astronomy (not much about latter) Early Latin Astronomy

Date of Easter • Historically tied to Jewish observance of Passover – beginning 15th day of month Nisan • Early church: Pascha (Easter) on Nisan 14 • Independent of local Jewish observances, same for entire Church – First Council of Nicaea (325 AD): Date = first Sunday after first ecclesiastical full Moon following “vernal equinox” (actually Mar. 21; equinox often on Mar. 20) Early Latin Astronomy

Date of Easter • Ecclesiastical full Moon ≠ astronomical full Moon; based on day number for Moon’s age (14) with months of 29 or 30 days (synodic month) – see rightmost column in Farmer’s Almanac (+1) • Like Jewish calendar, based on Metonic 19-year cycle -- lunisolar • Look for cycle that includes both lunisolar cycle and the day of the week (Easter must be Sunday) Early Latin Astronomy

Date of Easter • Solution in Venerable Bede, On the Divisions of Time • Julian calendar: common years 365 days ÷ 7 = 52 remainder 1  day of week advances by one each year (Jan 1. on Mon. – next year on Tues.) • Leap years every fourth year: remainder 2 instead of 1  every four years add 5 days • In seven cycles of four years go through exactly 5 weeks, end up same day of week (28 years) Early Latin Astronomy

Date of Easter • Metonic cycle for tropical year and lunar phase, 28-year cycle for day of week  19 × 28 = 532 years • (Western Christianity later switched to Gregorian calendar; more complicated – three of four century years omitted) • Latin name for calculation of date: computus Early Latin Astronomy

Translations from Arabic to Latin • Gerbert of Aurillac (later Pope Sylvester I) studied astrology at Barcelona, wrote book on astrolabe (ca. 1000 AD) • Athelhard of Bath went to Middle East; translated zij of al-Khwarizmi (1126), introduced ideas of algebra to West • Translations often had awkward combinations of Latin and Arabic words Islamic Influence

Translations from Arabic to Latin • After Toledo captured by Christians (1085), numerous works translated into Latin, spread through Europe • Gerard of Cremona: Toledo Tables; later Almagest (1175; other translations elsewhere, some from Greek) • Gerard’s other translations included Aristotle’s On the Heavens, Euclid’s Elements, and al-Khwarizmi’s Algebra – 87 works in all! Islamic Influence

Astrology in the Christian West • Astrology in precarious position, as in Islam – regarded by some as superstitious • At same time, established as part of medicine, based on Aristotle’s microcosm-macrocosm analogy (Chaucer quote in Hoskin) • Aristotle’s ideas themselves initially considered heathen, banned at University of Paris Medieval Astronomy

Astrology in the Christian West • Later, astrology reconciled with Christianity to some degree: influence of stars not rigidly deterministic but only tendency • Man imbued with free will by the Creator, capable of resisting influence • Aristotle’s ideas themselves were completely reconciled with Church doctrine by Thomas Aquinas at University of Paris in Summa Theologica (1274) Medieval Astronomy

Universities • Some grown from cathedral schools; all tied to Church -- faculty clerical (some minor orders); faculty and students all under canon (church) law, not civil law • First chartered university Bologna (1088); second Oxford (1096) • Most distinguished medieval university Paris (1200) Medieval Astronomy

Universities Organization of faculty in descending order of status: • Theology • Medicine • Law • Arts (liberal arts) Function of university originally was teaching, not research. Students of Arts were very young, typically 13 or 14 and sometimes younger. Medieval Astronomy

Medieval Arts Curriculum Theology or Metaphysics HIGHER PHILOSOPHIES Moral Philosophy, Natural Philosophy Quadrivium: Arithmetic, Harmony (Music), Geometry, Astronomy Trivium: Grammar, Rhetoric, Logic (Hoskin, Cambridge Illustrated History) Medieval Astronomy

Medieval Christian Cosmology • Illustration from Nuremberg Chronicles (1493) • Aristotelian with added Christian features • Earth at center with four elements, planetary spheres, sphere of fixed stars = firmament (precession), crystalline sphere (trepidation), and Prime Mover (daily) • Empyreum = Heaven with God and angels on outside of all (Hoskin)

Medieval Christian Cosmology • Illustration from Peter Apian’sCosmographia (1539) • Aristotelian with added Christian features • Earth at center with four elements, planetary spheres, sphere of fixed stars = firmament (precession), crystalline sphere (trepidation), and Prime Mover (daily) • Empyreum = Heaven with God and angels on outside of all

Astronomy Textbooks • Need for simplified textbooks on astronomy for Arts students – Almagest far too hard! • Sacrobosco (John of Holywood) in 13th century: • Computus – introduction to time-reckoning • Algorismus – arithmetic used in astronomy • Tractatus de sphaera = Treatise on the Sphere – celestial sphere (stuff we did at beginning of course); comprised four parts: Celestial sphere with Earth at center, daily motion Celestial equator, ecliptic and zodiac, meridian, altitude of celestial pole Rising and setting of celestial bodies, length of day and night at different latitudes Motions of Sun, Moon, planets; outline of eclipses Medieval Astronomy

Astronomy Textbooks • Part IV completely unsatisfactory • Most popular replacement: anonymous Theory of the Planets fairly soon (later 13th century) • Hipparchus’s model for Sun • Ptolemaic-like models for Moon, Mars, Jupiter, and Saturn • Models for Venus and Mercury • Treatment of eclipses not entirely satisfactory Medieval Astronomy

Universities Beginning of new thought – research? -- in universities, not just teaching ancients University of Paris in 14th century – concept of impetus in connection with Aristotle’s theory of violent or forced motion Medieval Astronomy

Aristotle • Sublunary (terrestrial) region: • everything consisting of varying proportions of four elements (taken from Empedocles) – earth and water (heavy) and air and fire (light) • mutability (change) is endemic • natural motions are vertical – down (heavy elements) and up (light elements) • Superlunary (celestial) region: • only one element = “fifth” element or quintessence • immutability = no change • natural motion is uniform circular motion Motion other than natural is “violent/forced motion”

Universities Development of impetus concept -- • Jean Buridan: effect of air resistance on motion • Nicole Oresme: impetus as “incorporeal force” (like fuel) initially infused into body, then used up (also anticipated Descartes with analytic geometry) • Albert of Saxony: projectile’s trajectory in three stages: impetus dominates; impetus exhausted and gravity becomes important; gravity dominates Medieval Astronomy

Universities Oresme, Commentary on Aristotle’s On the Heavens • Impetus allows one to evade the argument of fall against the Earth’s rotation • Arrow is imparted impetus in forward direction by Earth’s rotation before it is released • Arrow moves eastwards as it rises and falls • Conclusion: One cannot tell if Earth rotates or is at rest. Medieval Astronomy

Aristotle • Earth does not rotate around an axis: Argument of fall: If Earth rotates, an arrow shot vertically will fall to the west of the archer; instead it falls on the archer’s head unless he moves away. (Actually, the arrow does fall to the west, but by an extremely small amount.)

Instruments of Late Medieval Old Quadrant foresight curves for finding time of day angular scale for altitude backsight plumb line Medieval Instruments (Hoskin, Cambridge Illustrated History)

Instruments of Late Medieval New Quadrant = Astrolabe Quadrant ecliptic from rete of astrolabe, folded twice angular scale for altitude backsight foresight Medieval Instruments

Instruments of Late Medieval New Quadrant = Astrolabe Quadrant • Invented by ProfatiusJudaeus (Jacob benMahir) • Both quadrants more efficient than astrolabe: for given size, baseline is twice as long for angular scale (radius vs. diameter) • Like astrolabe, new quadrant is both demonstration instrument and measuring instrument Medieval Instruments

Instruments of Late Medieval Cross-Staff (Hoskin) Medieval Instruments

Instruments of Late Medieval Cross-Staff • Invented by Levi benGerson = Gersonides in first half of 14th century • Observer sights across top of cross-piece at one object, then across bottom at the other, adjusting the position of the cross-piece to do so simultaneously • Long piece is marked so that distance of cross-piece from eye can be measured Medieval Instruments

Instruments of Late Medieval Cross-Staff • Cross-staff (also known as Jacob’s staff) had two uses: • (Could also be used to measure Sun’s altitude with eye protection, but was replaced by backstaff, which uses a shadow, and later sextant) Measuring angular separation between two objects, as with the star and the Moon in the illustration Measuring the altitude of an object as angular distance above the horizon; if Polaris, estimates latitude for navigation Medieval Instruments

Instruments of Late Medieval Nocturnal Little Dipper sighting hole (Polaris) Big Dipper pivot arm handle • Sight through hole on Polaris • Line up pivot arm on pointer stars – Big or Little Dipper Medieval Instruments

Instruments of Late Medieval Nocturnal • Use reading to correct for displacement of Polaris from true North Celestial Pole • Use reading to tell sidereal time of night; correct to solar time by using scale for days of year Medieval Instruments

Instruments of Late Medieval Mechanical Clock (Hoskin, Cambridge Illustrated History) Medieval Instruments

Instruments of Late Medieval Mechanical Clock • Mechanical clocks for time of observation --not yet accurate enough for precision time measurement • Richard of Wallingford – astronomical clock replica medieval universe: Moon’s phases and eclipses, variable motion in longitude • Giovanni de Dondi – astrarium at Padua; geared Ptolemaic mechanism (Remember Antikythera Mechanism?) Medieval Instruments

Instruments of Late Medieval Astrarium of de Dondi (1364) Venus dial Moon dial Medieval Instruments Modern reproduction from detailed plans

Prague Astronomical Clock (1410) Medieval Instruments

Instruments of Late Medieval Prague Astronomical Clock, complete view astrolabe face calendar face Medieval Instruments

Instruments of Late Medieval Astronomical Clock of Strasbourg Cathedral (1354) astrolabe face Medieval Instruments

Astronomy Textbooks • Printing using moveable type introduced to Europe by Gutenberg, 1450 – two major effects: • More rapid and wider dissemination of ideas • Elimination of copying errors (but more important to proofread!) • Georg Peurbach (sometimes Purbach), professor at University of Vienna; gave private lectures on Ptolemaic system • Lecture notes written up, published posthumously 20 years later by protegé Johannes Müller, known as Regiomontanus – New Theory of the Planets (1474)

Ch. 4 Medieval Latin Astronomy