stephen c. mccluskey 1998 cambridge university press …fverbunt/iac2011/medieval.pdf · stephen c....

Astronomies and cultures in early medieval EuropeStephen C. McCluskey 1998 Cambridge University Press

A summary

Frank Verbunt

16th February 2007

A summary (Frank Verbunt) Astronomy in early medieval Europe 16th February 2007 1 / 32

Outline

1 IntroductionLegacies: Greek astronomyLegacies: Celtic

2 Early Medieval astronomyWhy should a Christian study astronomy?Astronomical problems in the BibleDivision of the yearEaster computusMonastic TimekeepingAstronomy in the liberal arts

3 Later Medieval astronomyFusion of traditionsEncounter with Arabic astronomyThe rebirth of Ptolemaic astronomy


Legacies: Greek astronomy

Greek astronomy: PtolemyBooks by Ptolemy:

Megale Syntaxis (Almagest):self-contained overview ofastronomy

Planetary Hypotheses:physical model of system ofspheres (>al-Farghani)

Handy Tables: expandedtables from Almagest, withinstructions for use

All of this is lost in early medievaltimes

Plinius Maior Historia NaturalesQualitative, i.e. no computations

book 2: the Earth is a spherewithin nested spheres of planets& stars; motion of spheres

book 6: length of (longest) dayas function of latitude

book 18: stellar calendar insome detail, regional variation)

Plinius knows about inclination ofecliptic, retrograde motion of planets,and the 233 months eclipse cycle


Practical Astronomy: time of year

Time of year from the Sun

length of day (impractical)

length of shadow(impractical)

locus of rising/setting

Time of year from stars

first appearance of star

last appearance of star

Yearly motion of Sun on horizon (Ayiomamitis 051221)


Celtic Astronomy: Calendar of Coligny


Celtic Astronomy

Calendar of Coligny

four festivals

(+92 d:) 2 Rivros

(+91 d:) 4 Cutios

(+93 d:) 2 Equos

(+91 d:) 4 Cantlos

possibly these festival days aremid-quarter days:

Samhain, beg. Nov

Imbolc, beg. Feb

Beltaine, beg. May

Lughnasa, beg. Aug


Celtic influence of festive days

Samhain and ImbolcSamhain is end of Summer,when for 1 day the living anddead are in contact > AllSaints, Nov. 1 (798)

Imbolc festival of 3 sistersBrigit who did poetry,medicine, metalwork > St.Brigit, Feb. 1 midwife

Beltaine and Lughnasa

Beltaine fertility festival (Mayday) > Blessed Virgin, May2,3 (800-902)

Lughnasa festival of Lugh‘the shining one’ (Sun),bringer of plenty, wargod >king St. Oswald, Aug. 5(Northumbria 390-467) orbishop St. Justus (Lyons =Lugdunum 642-685)


Why should a Christian study Astronomy? Topics

Why should a Christian studyastronomy?

for practical matters(Augustine, Bede)

also to comtemplate theperfection of the creator(Hrabanus Maurus 780-856)

Hence astronomy is part ofclerical education (Christian ofStavelot d.>880)

Topicsproblems in the Bible

division of year in 4 equalparts

Easter computus

monastic timekeeping

geometrical astronomy inquadrivium


Astronomical problems in the Bible

Astronomical problems withthe Bible = Vulgate

world as a perfect creation vs.disturbances wrought by God

1 Christmas star2 darkening of Sun at

crucifixion (i.e. passoverwhen Moon is full)

3 Joshua lets Sun stand still4 Isaiah moves back the

shadow of a sundial

Discussed by:

Jerome ( 327-420)

Augustine (fl.396-430)

Theodore of Mopsuestia (d.428)

Cassiodorus ( 490-583)

Gregorius Magnus ( 540-604)

One solution: men’s knowledge isimperfect: the apparent irregularitieswere planned by God at beginningContra astrology: planets and starsare created objects, hence cannotdetermine things


Astronomical problems with the Bible: Christmas star

Vulgate

2:1 Cum ergo natus esset Jesusin Bethlehem Juda in diebusHerodis regis, ecce magi aboriente venerunt Jerosolymam,2:2 dicentes: Ubi est qui natus estrex Judaeorum? vidimus enimstellam ejus in oriente, et venimusadorare eum.

St. James Bible Matthew2:1 Now when Jesus was born inBethlehem of Judaea in the daysof Herod the king, behold, therecame wise men from the east toJerusalem,2:2 Saying, Where is he that isborn King of the Jews? for wehave seen his star in the east,and are come to worship him.


Astronomy in the Bible: additional remarks

Additional remarksMithras is often depicted withtwo assistants; these turnedinto the three sages inChristianity, to illustrate thatMithras bowed to Christ

Bede of Jarrow comparesIsaiah’s extra day to theabsence of sunset in Thule

(tradition:) creation atequinox, with full Moon: day(Sun) as long as night(Moon)

Mithras


Division of the year

Julian calendar365.25 days to year

solstices/equinoxes at 25March, 24 June, 24 Sep, 25December

seasons start halfway these:7 Feb, 9 May, 7 Aug, 7 Nov(Bede)

Obviates need for astronomicalobservations to determine time ofyear!

Important Christian dates

Easter (⇒ computus)

births and conceptions ofChrist and John atequinoxes and solstitia

Christmas either on Dec.25 (solstitium; Rome336), or 12 days(1/apostle) later: Jan. 6

saints as markers ofeveryday life


Easter Computus

Jewish Passoverselect a lamb on Nisan 10,eat it at following full Moon,then fast (unleavened bread)

Nisan is first month of year

month begins with newMoon: full Moon is Nisan14/15

BibleMatthew, Marc, Luke: lastsupper Nisan 14

John: crucifixion at Nisan 4

Conversion to Easterearly jewish Christians:Easter = Nisan 14

Rome: Easter on 1st Sundayafter Nisan 14

computation always in Julianyear, using cycles

councils of Arles (314),Nicea (325): Easter on sameday everywhere (no methodgiven)

19 yr = 235 m -0.06 d East84 yr = 1039 m +1.28 d West95 yr = 1175 m -0.31 d


Easter Computus: choices and conflicts

Easter choicesequinox date: Mar 25 =Annunciation (Rome) orMar 21 (Nicea)

cycle of 19 y or 95 yr(Alexandria) or 84 y (West)

allowed Easter date on Nisan15-21 or on Nisan 16-22

Pope Leo notes in 451 that thisleads to different computer Easterdates in 455: study required

Victorius of Aquitane, 45795 y, Mar 25 equinox

both dates given whenEaster on Nisan 15 or 22

tables from 28 to 559

Dionysios Exiguus, 52595 y, Mar 21 equinox

Easter on Nisan 15-21

tables until 626

extended by Anonymous forextra 95 y


Easter Computus: England

English computus

664 King Oswiu ofNorthumbria organizessynod at Whitby monasteryto solve Easter date conflictwith queen.

Bede of Jarrow collectsbooks from Rome: Pliny,Virgil, Isidore, Macrobius

results in book De temporumratione

Bede De temporum rationerelation postion Sun inzodiac and length of day

equinoxes and solstitia set atdegree 8 of signs (< Pliny):25 Dec, 21 Mar, 24 Jun, 24Sep

observe (!) sunset nearequinox to determine need ofleap year: full Moon risesdue east on equinox


Monastic Timekeeping

Foundation of MonasteriesMartin of Tours (∼316-397)founds first Monasteries in West.Rules given by

Cassian Institutes ∼420

Benedict Rule ∼480-550

‘the Master’ Rule

require prayers at night, henceneed of timekeeping. AfterCassiodorus (∼490-580)Introduction to divine and humanreadings Monasteries areintellectual centers

Methods of timekeeping

Gregory of Tours (∼573) seebelow

Petrus Damian 1067: singingpsalms

monastery Fleury, 10th cy:clepsydra

Pacificus of Verona 776-844:position of Polaris star withrespect to 5th mag star nearpole


Monastic Timekeeping: Gregory of Tours

Gregory of Tours, ∼573

mentions Martianus Capella,Virgil

invents Christianconstellation names (e.g.Cygnus > Cross above Aand Ω)

rejects astrology

accepts comets as badomens

De cursu stellarumlength of day increases1 h/month from 9 h in Dec to15 h in Jun, and back (OK forMediterranean, not forTours!)

visibility Moon increase by1 h/day (or 0.5 hr/day)

correlation list of rising starswith time to sunrise (visibilityof horizon! effect onarchitecture/location ofmonasteries?)


Astronomy in the liberal arts: Astronomy for poets

Known books on astronomy

Latin version of Ptolemy’sHandy Tables translated∼530: Praeceptum canonisPtolomei, used after ∼ 1000

Cicero Phaenomena, Dreamof Scipio

Macrobius (∼360->422) onPlato Timaeus.

Chalcidius (early 4th cy)Comments on Timeaus

New books on astronomy

Martianus Capella (fl.410-439) Marriage ofPhilology and Mercury

Boethius (∼580-524)Consolation of Philosophy

Cassiodorus (∼551)Introduction to divine andhuman readings mentionsPtolemy

Isidore of Seville (∼570-636)De natura rerum


Astronomy in the liberal arts: items

Earth is sphere, climate zones

planets in platonic order (i.e. Sunimmediately above Moon) > largesize of universe e.g.dSaturn= 46646dMoon

non-uniform notion of Sun andplanets (i.e. epicycles, qualitatively)e.g. 32 d for Gem, 28 d for Sag

19 yr cycle of Moon

vague idea of eclipses

No explanations, often wrong in details:e.g. each zodiacal sign rises in 2 hr

Gossuin de Metz, 13th Cy.


Fusion of traditions: Court of Charlemagne in Aachen

Charlemagne correspondswith Alcuin (student of Bede)on calendar, motion Sun andMoon in Zodiac

Computus, not beyond Pliny

Dungal of St. Denis usesaverage time betweeneclipses in Pliny to compute2 eclipses in 810

collection of computus texts(e.g. Bede De temporumratione) and tables:calendars, positions Sun inzodiac

excerpts of Pliny, Macrobius,Capella

descriptions of constellations:‘star catalogues’, i.e. pictureand number of stars (nocoordinates)

distances and latitudes ofplanets (not connected toperiods)

length of day from linearinterpolation

qualitative earth-sky geometry:diagram positions sunrise atsolstitia, equinoxes


Fusion of traditions: Charlemagne and successors

Charlemagne

Charlemagne has ‘Silver table ofcelestial sphere, stars, course ofplanets’

Louis le Pieux‘Leiden Aratus’

positions of planets observed(!) at equinoctial full moon

planet periods, apogea,perigea, exaltations (fromPliny)

comets seen as omen

Leiden Aratus: Cassiopeia


Mantle descriptio tocius orbis of Henry II

(personified) Sun, Moon; Christ, St.John, Mary; constellations; celestialcircles; and some astrology: ‘When Scorpio rises, deaths increase’

earlier mantles with stars: Mithras, Aaron (in Bible)


Fusion of traditions: Rise of astrology

Astrology: Hrabanus Maurus(∼840)

various forms ofprognostication: planetpositions at day (geneathlicastrology) or hour (horoscopicastrology) of birth, apparentlyfor king or state

condemns fear for eclipse

(average) positions Sun, Mooncomputed, planets observed

conversion sky to horizonbeyond capability

Computus textbooks

Hrabanus Maurus (820)

Helperic of Auxerre (end 9thcy) suggests to determinesolstices by projectingsunbeam through slit on wallat sunrise

Abbo of Fleury (∼978)heliacal/cosmic rising/settingof stars; planet periods6,12,18,24,30 y (!) purenumerology, 2 h rise time ofsigns


Encounter with Arabic astronomy

Topics

Calendar of Cordoba

Zij of al-Khwarizmi

Astrolabe

Islamic astronomers understoodPtolemy fully from 8th century.

Psalter of Blanche of Castille,mother of Louis IX⇒


Calendar of Cordoba: Kitab al-anwa’; Zij al-Khwarizmi

written by Bishop Recemund ofElvira and ‘Arib ibn Sa’d.

anwa’ (sing.: naw) times ofheliacal/cosmical rising/settingof constellations

duration of day, computedgeometrically for Cordoba

four different dates for vernalequinox (Sindhind, Greekmedicine, measuremental-Battani 882) > underminesbelief in western calendars

reaches west via John of Gorze (inCordoba 953-955)

Zij al-Khwarizmi (‘algorithm’)many copies survive

translation Petrus Alfonsi(1116): no tables

translation Adelard of Bath,emended ∼1150 Robert ofChester: tables based onSindhind for average positionand corrections to actualpositions Sun & planets

tables of Toledo re-computedfor Marseille by Raymond<1450


Astrolabes and Manuals for Astrolabes

Astrolabequantitative measuringinstrument

model of the Universe

for determination of time in(un)equal hours from Sun orstars

western addition: eccentriccircle for location of Sun inZodiac

IntroductionsLupitus of Barcelone (fl.975-995, rejects astrology)

Gerbert of Aurillac (∼945-1003)(also teaches unequal hoursfrom Martianus, withoutunderstanding)

(unknown author) manuscript inReichenau ∼1000

Fulbert of Chartres (∼960-1028)menomic rhyme with 8 arabicstar names

no geometric understanding


Astrolabes: Better understanding

Hermann of Reichenau(1013-1054) De mensuraastrolabii

instructions for constructionof astrolabe

coordinates for 27 stars

equinox at Mar 18 (fromLatin martyrologies)

Problem of date of equinox nowclear and acute

Walcher of Great Malvern1092: first recorded westernmeasurement with astrolabe

measures and collectseclipse times, compares withhis own tables

re-discovers unequal motionMoon

claims trepidation ofequinoxes

praises astrology for medicin


The rebirth of Ptolemaic astronomy: Translations

Arabic authorsAbu Ma‘Shar GreaterIntroduction to astrology John ofSeville (1133), Hermann ofCarinthia (1140)

Ibn al Muthana, principlesunderlying tables of alKhwarizmi, tr. Hugh of Santalla(1119-1151)

simpler: al-Farghani On thescience of the stars (dimensionsof spheres, rise times of signs)John of Seville (1135), Gerardof Cremona (∼1135)

Greek authorsEuclid Elements Adelard(>1113)

Ptolemy Almagest arabictext, tr. Gerard of Cremona(1144)

Ptolemy Almagest greek textpresented to Roger of Sicilyby Manuel Commenus, tr.student of medicine (∼1160)


The rebirth of Ptolemaic astronomy: Education

Corpus astronomicum

Education from monasteries touniversities (cathedral schools).Many new books, often based onal-Farghani, collected in CorpusAstronomicum

computus: tables of Sun inecliptic, based on newtechiques

algorismus: basics ofastronomical calculations

theorica planetum:qualitative explanation ofepicycles

Simpler books:

John Sacrobosco (∼1130)De Sphaera

John Pecham (∼1215)Tractatus de Sphaera areepicycles real? Yes! theydo’nt break the spheres? (cf.al-Bitruji)

Roger Bacon Compotus


The rebirth of Ptolemaic astronomy: Education

Grosseteste (∼1215)De Sphaera

general geometry

equation of time

orbit of Moon with Ptolemy’seccentric

altitude of star as function oflatitude

Computus correctorius

change of equinox dependingon length of year al-Battani isbest (Christ born at equinox)

Much used text: AnonymousTheorica planetarum (∼1250)

geometry of Ptolemy’s theory,including complex Mercury

use tables to compute positionof planet

adapt tables for other latitude

Campanus of Novara (1261-1264 )

all major points of Ptolemy

Planetary Hypotheses: starsat 73,387,747+10/66 miles

builds and uses equatorium

Demands on students are low, but good books are available


The rebirth of Ptolemaic astronomy: William of St.Cloud

calender based on accuratearabic numbers (with PeterNightingale, 1190s): no useof 19yr cycle, hence notperpetual.

date of entry of Sun in eachsign

observes Sun, Moon, Mars,Jupiter, Saturn between1285 and 1292 to test andimprove tables

importance lunar phase forphysicians

confirms al-Battani precessionof 1/66 y i.e. no trepidation

obliquity from noon-shadow atequinoxes: 2334′ (correct:2331′53′′)

suggests to show change indistance to Sun from measuringdiameter with pinhole throughyear

measures conjunctions of Mars,Jupiter, Saturn, Moon with stars.


Summary

Early Middle Ages

incorporation pagan festivalsinto Christian calendar

struggle with Bibleastronomy

struggle with Eastercomputus

night time from stars

These topics enter monasticeducation

Recovering astronomy>800 improved schools: bookson astronomy

first based on late-Latin authors:simplistic

revival of astrology (also formedicin)

>1100 gradual introduction ofarabic knowledge

gradual introduction of newobservations


stephen c. mccluskey 1998 cambridge university press …fverbunt/iac2011/medieval.pdf · stephen c....

Documents