Astronomies and cultures in early medieval EuropeStephen C. McCluskey 1998 Cambridge University Press
A summary
Frank Verbunt
16th February 2007
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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
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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
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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)
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Celtic Astronomy: Calendar of Coligny
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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
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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)
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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
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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
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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.
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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
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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
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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
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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
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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
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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
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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?)
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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
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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.
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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
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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
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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)
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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
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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⇒
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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
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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
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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
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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)
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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
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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
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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.
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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
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