Stoic alternatives to Aristotelian cosmology: Pena, Rothmann and Brahe

24 Pages·2016·0.25 MB·English

by  Barker P.

STOIC ALTERNATIVES TO ARISTOTELIAN COSMOLOGY : PENA,
ROTHMANN AND BRAHE

Peter Barker

Armand Colin | Revue d'histoire des sciences

2008/2 - Tome 61
pages 265 à 286

ISSN 0151-4105
Article disponible en ligne à l'adresse:
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http://www.cairn.info/revue-d-histoire-des-sciences-2008-2-page-265.htm
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Stoic alternatives to Aristotelian
cosmology :
Pena, Rothmann and Brahe
Peter BARKER *
Résumé:LessavantsduXVIesiècleontutilisélesidéesstoïciennesen
philosophie naturelle contre Aristote. Je m’intéresse ici à celles sur la
substanceducieletlescausesdumouvementdesplanètesdepuisJean
deLaPènejusqu’àChristophRothmannetTychoBrahé.Jeconclusque,
avantJusteLipse,cespenseursontemployédesélémentsdustoïcisme,
maisnonlestoïcismecommesystèmephilosophique.
Mots-clés: Jean de La Pène; Christoph Rothmann; Tycho Brahé;
cosmologie;stoïcisme.
Summary: Sixteenth century natural philosophers used Stoic ideas
Do againstAristotle.Iconsiderideasonthesubstanceoftheheavensand n
cu the causes of planetary motion from Ioannes Pena to Christoph Roth- oli
m mann and Tycho Brahe. I conclude that, before Justus Lipsius, these C
ent té pthhiinlokesorsphuisceadlseylestmemen.ts of Stoicism, but not Stoicism considered as a mand
léc Ar
ha ©
rg Keywords:IoannesPena;ChristophRothmann;TychoBrahe;cosmo- 3.
é depu logy;Stoicism. 2 04h1
is 1
w 20
ww By the sixteenth century Aristotle’s account of the heavens had 03/
.c 2/
a sufferedvariousamplificationsandaccretions.First,medievalwri- 0
irn.in tershadmadeitacommonplacethatAristotle’sfifthessencewasto 98 -
fo bespokenofasaether,andhadthepropertiesoftri-dimensionality, 7.
- - - 93.94.177 ttPbmreeearoutnswtrsiboapeandaecsdrneheundtschoeyensd,mwoalatinodrwdditocsyr,ea.usllhciSdsauetdilcgnaoetgsennpidenep,rctalriauttfihenseeeidotthanthrvesya.eroSepiropooimiuccsasiyeticiotsnlriinaxtcesdteril–iteoninocotnkthrhinecfergeocPnmcotteourbnlrGeystrmeiwtcoharraii–gc-t o - - - 93.94.17
.9 nf
8 - 02 twrahdoilteioonf.tThheesspehseertiscaolfsohreblls,wcoenreceunsturiacllwyiathsstuhmeeEdarttoh,odcecsuigpnyattehde cairn.i
/0 w.
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/2 *PeterBarker,Departmentofthehistoryofscience,UniversityofOklahoma,Norman,OK, w
01 73019USA.Fax:(US)405-325-2363.E-mail:[email protected] s
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PeterBARKER
the sphere of a planet. Whether one accepted the detailed three-
dimensional model or not, it was accepted that planets did not
move themselves, but rather were moved by the orb or orbs in
which they were embedded « like knots in a board » to use a
commoncontemporaryphrase.Variousadditionalsphereshadalso
been added at the outer edge of Aristotle’s cosmos, notably a
« crystallineheaven »andadditionalspheresthataccountedforthe
precession of the equinoxes 1.
TychoBrahe’sroleintherejectionoftheseAristoteliantenetsiswell
known.IthasrecentlybeennotedthatChristophRothmann–mathe-
matician to the Landgrave Wilhelm IV of Hesse-Kassel – predated
Tycho Brahe in the rejection of celestial spheres with planets that
moved because they were embedded in them. Christoph Roth-
mann’s arguments derive from specifically Stoic sources, and origi-
nate in a context of direct opposition to Aristotelianism. By exami-
ning these arguments and how they were deployed, I hope to show
some of the ways in which sixteenth century natural philosophers
drew on Stoic ideas in the period before Justus Lipsius and suggest
D
o somepreliminaryanswerstothequestionswhy(andhow)sixteenth n
cum centurynaturalphilosopherscametorejectAristotelianverities2. Coli
ent té 1-On the properties of the celestial spheres according to medieval writers, see Edward mand
léc Grant,CelestialorbsintheLatinMiddleAges,Isis,78(1987),153-173.Ontheoriginof Ar
ha themultipleorbmodelofplanetarymotion,seeBernardR.Goldstein,TheArabicversion ©
rg ofPtolemy’splanetaryhypotheses,TransactionsoftheAmericanPhilosophicalSociety, 3.
é 1
depuis 5eaqn7ud/4iPv(oe1tce9ar6lB7so)a.rlikOdeinrt,yTtohhreehraaoprldpenlioecfsasRtiioontnhsmioxfatentehnnetihntectrhementdu«irscysrodylsiusttaciloulinsnsoieof»nthst,eosceteehleeBsehtrieanalavsredpnhRse.,rGeasno,dlBdrstihtteiesiinhr 12 04h
w Journalforthehistoryofscience,28(1995),385-403,esp.391-395.Inalaterarticle,The 20
w medievalcosmos:Itsstructureandoperation,Journalforthehistoryofastronomy,28 3/
w 0
.c (1997),147-168,EdwardGrantsuggestsa«gradualshift»fromfluidtosolidheavens 2/
airn.info bpReroogtbhinlmenmainnagnaeinsltartoh«neotemthoiircritaoe-decneoltslh’maccoeclnootgmuicroyod.aOezinolentehsia»sc,rsReuibvsijcsertcaittt,duisreesetodraoilapsoodeMCllaoigpfiueleorlnsoiAcfio.aG,:5rCa1hn(ra1ids9ta9o,6pI)hl, 7.98 - 0
- - - 93.94.177 2-7SAmMaOtn8.eenid9GcltlCàh-ar8Meahtd2ulnrie-8isgaPsl,udtiiConeeeaprils,nrhpheSAqi.fsRu.eL8opereG0ectorh5nreseam,oenmnrlnta,iaodonZdLet(noeaiMne,daMgiincElaaidlorcenenuDlTmoodysecea:flvbhrAuiakdtoinatsedeeBgsoaercb(sal:VopoohMeshueGmnèotsirumocheeeeleaseór,rinGg(dn1Ptioiic5acdloe3redie6lsAseel-t:nssed1stiBi5ionba1e3cal5al7itln8sate)ip.dt8stiohF,BL:eo2cearBro0etrtrks0asrumee2bngrs)oyeo,.(l1n,1oB9e9Bgr9ri9urac5a6nlo)h)o,d,enoi,tisep.nclR.l1ua1cosi;5ststhei.8Momci4nnoiagnansnund.ene1deal, o - - - 93.94.17
.98 - 0 Uscriseunsc,eRsöeseliPnet(eNraBpaorklie:r,BSitboliicocpoonlitsr,ib1u9ti9o6n)s.tOoneatrhlyemStoodicernbascckiegnrocue,nidnMtoaergaarlryetmJ.oOdselrenr airn.inf
2 (ed.),Atoms,pneumaandtranquillity:EpicureanandStoicthemesinEuropeanthought c
/03 (Cambridge:CambridgeUniversityPress,1991),135-154,andPeterBarkerandBernard ww.
/2 R. Goldstein, Is seventeenth century physics indebted to the Stoics?, Centaurus, 27 w
01 (1984),148-164. s
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StoicalternativestoAristoteliancosmology:Pena,RothmannandBrahe
In1555IoannesPena(JeandeLaPène)wasinstalledasprofessorof
mathematics at the Collège royal in Paris. He was the son of a
Huguenot family from Aix-en-Provence who came to Paris as a
student. According to Nicholas Nancel he became one of a small
circle of students working with Petrus Ramus (Pierre de La Ramée)
on new translations of classical authors in science and mathema-
tics. Petrus Ramus, of course, is famous for his opposition to
Aristotle,or,moreproperly,towhathebelievedtobethecorrupted
Aristotle of the Schools. Ioannes Pena was educated in an atmo-
sphereofhumanisticantischolasticism,andspecificallythecritical
scrutiny of Aristotle’s works by Petrus Ramus – one of the most
importantconversationswithAristotleduringthesixteenthcentury.
In a dedicatory essay (perhaps a version of his inaugural lecture)
prefacing his new translation of Euclid’s Optics Ioannes Pena
rejectedaseriesofAristoteliandoctrinesinnaturalphilosophy.His
ideasreappearintheworkofChristophRothmann,arecriticizedby
TychoBraheandhavetheirlastimportantairinginJohannesKepler.
The alternatives Ioannes Pena presents to Aristotelian natural phi-
losophyderivefromtwomainsources,theopticaltradition,andthe
Do doctrines of Stoicism 3. n
cu oli
m C
ent té Tsioxdteaeyn,tShtocicenctousrmy oreloagdyerissilteswsofaumldilhiaarvtehabneethnarteoafdAilryisatovtaliel,abbluetitno mand
léc Roman authors such as Marcus Tullius Cicero, Lucius Annaeus Ar
ha ©
rg SenecaandGaiusPliniusSecundus(PlinytheElder),whileaspects 3.
é 1
depu oAfdaSmtoaicnticuoss(mOoriggoenny) awnderePlumtaerncthiounseCdhaineroanuethnosirss(PlilkuetarOchri)g.eLnikees 2 04h
is w Aristotle’s cosmos the Stoic cosmos is spherical, but it has not 201
w alwaysexistedinthesamephysicalconfiguration.Initiallyasingle 3/
w 0
.c substanceconstitutesthewholeoftheStoiccosmos.Thesubstance, 2/
a 0
irn.info tseprimriteudsipnnLeautimn,aacincoGrdrienegktoisthveaarisopuescltyitdisesciognnasitdeedreidgnuins,deare.rThoer 7.98 -
- - - 93.94.177 3fcor-aupEPfnphetptysdem(r(eseBudraaps.)rnp,klRloeeiremkf,cJeeeoSnavfittne)o,rrPi1ienec3gnit(atsh1hm(9ae185tS52tp)od8,ir-e9c5o3ss8c-c:)1Sera0pine7bidn.deFdSeodetodrliaCctsnohpynehesdfyetisrteifiecoumnsncniaeandnt1tiadh9cem8tars4aile,nxlSstyneloaetuatanitobhtlhneocrsonueufnjtNbotutuischrrtyhnae,oainllnbaocsRufeNopsnahiaannillcsodeessHloa’ss-. o - - - 93.94.17
.98 - 0 bniiostgicraapLhoyvoanfiPeentsruias,R2a4m(1u9s7se5e),P1e6t1e-r2S7h7a.rrSaitnt,ceNtihcoislaeusssaNyawcealsiufisrsPteptrrieRseanmteidvi(tsae,eHnu.m55a-) airn.inf
2 ChristophRothmann’sdebttoIoannesPenahasalsobeennotedbyMiguelA.Granada, c
/03 Eliminazione delle sfere celesti e ipotesi astronomiche in un inedito di Christoph ww.
/2 Rothmann:L’influenzadiJeanPenaelapolemicaconPietroRamo,Rivistadistoriadella w
01 filosofia,52/4(1997),785-821. s
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PeterBARKER
ofcreation.ThusincontrasttoanyofAristotle’selements,theStoic
fundamental substance has two special attributes : it is intelligent
and it is alive. When the universe begins, the pneuma directs its
own differentiation into something like the four Aristotelian ele-
ments.Twoofthese,earthandwater,arecarriedtothecenterofthe
spherical cosmos, although they continue to be pervaded by the
fundamental substance. Living creatures are animated by its pre-
sence even when their bodies are largely earth or water. Air is a
denserorcoarserformofpneuma,whichbecomespurerandmore
like fire the higher one ascends. The heavens therefore contain a
continuous fluid substance that stretches from the surface of the
Earth to the sphere of fixed stars, which is the boundary of the
cosmos.Intheheavens,theplanetsandstarsarelivingcreaturesof
relatively pure fire. But the kind of visible fire that produces light
andheatrequiresfuel,intheformofheavierelements.Thefunda-
mentalsubstanceflowsinwardsfromtheboundaryofthecosmosto
thecenterandoutwardsagain.Theinwardflowincidentallycarries
celestial influences to the region of the Earth and gives a physical
basis for astrology. The outward flow carries with it traces of
D terrestrialelementsthatbecomefuelforthestarsandplanets.Asthe
o n
cu Earth is finite, this process erodes and ultimately eliminates the oli
m C
ent té ttehrereusntriivaelrpsearrteotfutrhnesctoosimtsoins.itWialhsetnatael,lathnedfutheelhwahsobleeecnyccolensbuemgiends mand
léc again. Thus, the Stoic cosmos, like the Aristotelian one, is eternal, Ar
harg but not static : it eternally repeats the sequence of differentiation 3. ©
é andconflagrationjustdescribed.Thisentireprocessisgovernedby 1
depu anintelligentagentthatpervadestheentirecosmos.Itmightthere- 2 04h
is fore be said that the entire Stoic cosmos is alive 4. 1
w 20
ww An overt appeal to Stoic doctrines is apparent at several places in 03/
.c 2/
a Ioannes Pena’s essay. He mocks the Aristotelians for gathering 0
irn.in together all the living fire that should be spread out through the 98 -
fo wholeuniverseinasingleplace,theregionabovetheelementair. 7.
- - - 93.94.177 HoacnapendtindctoeshntetoibemcesioltaknhyceplwuhAseariinyos.ontoPmstaeterhlaniaalotlnancxostpnoahtkbreisanredegrivcopatftlAiafiocrrnieess,toisanthnleodthwinheetthrheaaegltscitoohanseaermbgoeuiflleokcsyowmfwrotehamteys o - - - 93.94.17
.98 - 0 4-PDraevssid,E1.9H77a)h;mP,eTtheerOBarirgkienr,so«fPSntoeiucmcaos»maonlodg«y(SCtooilcuimsmbu»s,,iOnhWioil:bOurhiAopSptaletebaUunmive(ersdi.t)y, airn.inf
2 Encyclopedia of the Scientific Revolution from Copernicus to Newton (New York: c
/03 GarlandPublishingCo.,2000),510a-511aand620b–622;MichaelJ.White,Stoic ww.
/2 natural philosophy (physics and cosmology), in Brad Inwood (ed.) The Cambridge w
01 companiontoStoicism(Cambridge:CambridgeUniversityPress,2003),124-152. s
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StoicalternativestoAristoteliancosmology:Pena,RothmannandBrahe
moon. A variety of arguments contradict Aristotle’s account of
cometsasrelativelylonglivedfiresinthesameregion.PeterApian
had recently demonstrated that the tails of comets always lay on a
great circle away from the Sun. Ioannes Pena and several contem-
poraries concluded that the head of a comet was a spherical lens
and the tail was a pyramid of rays created when sunlight was
focused by the head. This required that the head be a transparent
substance denser than air, and not fire, which was incapable of
refracting sunlight. Additional arguments based on their relative
speed compared to other celestial objects suggested that at least
somecometswerepartoftheheavens.IoannesPenaalsoarguedfor
motionsoftheEarththatcannotoccurinanAristotelian–orindeed
a Copernican – cosmos 5.
InAristotle’suniversetheEarthisstationaryandinthecenterofthe
cosmosbecausethatisthenaturalplaceoftheelementearthitself.
If the Earth could, by some means, be removed from the center of
thecosmos,itwouldreturntothispositionassoonastheelementof
whichitiscomposedwasallowedtoundergoitsnaturalmotion.In
D theStoiccosmos,however,theEarthismaintainedatthecenterof
o n
cu the cosmos by currents of the pneuma flowing inward from the oli
m C
ent té pwerriitpinhgearyboauntd2o5u0twinaArdlexfraonmdriitas6c,etenltlesr.usA:chilles Tatius, probably mand
léc Ar
harg «[TheStoics]usethefollowingexampletoprovethestateofrestof 3. ©
é theEarth.Ifonethrowsagrainortheseedofalentilintoabladder 1
depuis ainndthbelmowidsdilteuopfbthyefibllliandgditewr.iItnhtahier,stahmeesewedaywtihllebeearrathiswedillanredmsatainy 12 04h
w stayinginthecenter,beingkeptinequilibriumbythepressureofthe 20
w 3/
w airfromallsides.Andagain,ifonetakesabodyandtiesitfromall 0
.c 2/
a sideswithcordsandpullsthemwithpreciselyequalforce,thebody 0
irn.info 5-EuclidisOpticaetCatoptrica,nunquamantehacGraeceaedita.EademLatineredditaper 7.98 -
- - - 93.94.177 6-qoSuI(No1putsoha9urentie9nenOrn3tsgle)tpey,hmstr1eai,rceet-1P2ef9OeePs5r7ne.trp5tateore)mda,reN9tBfoR5aeaet0aurigko,sgiereuP.erb.me,g.anTa(uPaMrhdeae(ras1r,ito5tshhH,p5ee1ti7misd5c)t.oaaa5Otrlt7iyect)nh.uooeImtffohota.eharyninHosncpoiaeistfeusipncctPhartoaeolmmenrthpeaaaeot’stsshos«ierpftryamvroeeomeafrfastyictccAieoeanpmulsDieiaaesecndstustuertrioomsenunK»IoIOo.oemaTappnyhnlteniencr(e,iNeassPspePPhpiweesyennsslYliaauasoeb,taris3nokde0dne-: o - - - 93.94.17
.98 - 0 «knToawtiunsa»smanayearlostoicbneothveelriests.uTlthoefcwoonrfkusninogwAacthtriilbleustethdetaosttrhoinsoamutehrowrimthaayncoothnetarianutohnolry, airn.inf
2 fragmentsbytheoriginalAchilles,fromaworkthatwasnotoriginallyacommentaryon c
/03 Aratus.Whetherornotthisiscorrect,bytheRenaissance,theauthoroftheworkknown ww.
/2 in Latin as Isagoge ad arati phaenomena is firmly identified as «Achilles Tatius» in w
01 editionsfromFlorence(1567)andParis(1630). s
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willstayandremaininitsplace,becauseitisdraggedequallyfrom
allsides7.»
Whateverdoubtswemayhaveaboutthefeasibilityofthisdemons-
tration,AchillesTatiusprovidesavividimageofthestructureofthe
Stoiccosmos.Thebladdercorrespondstothesphereoffixedstars.
The air corresponds to the pneuma flowing from the periphery of
thecosmostothecenterandbackagain,andthelentilcorresponds
totheEarth,whichissupportedbythisflow.Thecentralpositionof
the Earth is therefore a dynamic equilibrium – which might vary if
the equilibrium changed 8.
In his 1557 preface De usu Optices Ioannes Pena rejects Nicolaus
Copernicus’triplemotionoftheEarth,butheofferstwoarguments
for another motion that varies the distance of the Earth from the
fixed stars. First he suggests that modern estimates of the apparent
sizes of fixed stars are greater than ancient estimates for the same
stars,suggestingthatthedistancefromwhichtheyareobservedhas
changed.However,thisargumentmayberejectedbyrejectingthe
observationsonwhichitisbased 9.Anotherargumentisimpossible
D
ocu to reject. Since the time of Callippus of Cyzicus the motion of the olin
m fixed stars themselves (the precession of the equinoxes) has varied C
ent téléc fCrolamudoinues Pdteoglreemeyi’ns7ti2myeeaanrsd,tboaocknetodoegnreeedeegvreereyehvuenrdyr6e6dyyeeaarrssiinn Armand
ha thetimeofAlbategnius(al-Batta¯n¯ı).ThevalueinIoannesPena’sday ©
rg lies between these extremes. Accepting, from the principles of 3.
é 1
depu acsatnroonnolmyyb,ethuantdtherestmooodtioansoafvthaeriahteioanveinnstihseundiifsotarmnc,ethoifstvhaeriaEtairotnh 2 04h
is 1
w 20
w 7-AchillesTatius,Isagogeadaratiphaenomena,inDenisPetau,Uranologion,sivesystema 3/
w 0
.c variorumauthorum(Paris,1630),121-164,127E:«Iamquodimmobilisterraconsistat, 2/
airn.info mihnoaiicnceieabxteit;m.&pAildnoflceaounlmdliogduednmeti.nmEcteoepdnsuimamërseiteqcrouramis,upanleiduaent,ct,eulnianqtuufomelliiacnbusluuabëmlriemmpeiluigilr,saasn,euu&mleiinnntivcmeuseliadceiaoegrmlaibnerduaimtoa 7.98 - 0
- - - 93.94.177 8-easmaGTutephaisqpleqipluuraueoasSninpelt,Piodsrt1icleiiaict9ernut5teair.cu.d9b»os)Ao,sbTSmm1uyrea0toncRn9sueqes.nulpnwadeaatuimerittsshdesaaddiiaunnemnbcsSoceeaEradiwmatburaremuttihdtterelasrbmhsSieaiafl,qrmoiconuwubmtias,muimrntcsuheokanedyrydp,wiuabPqotsehuryeikaatsslpioircqaefcsruleiAaoobntcdfuitvhestehriumllelynebodsSylmaitTqotdeaeuinycteidntsuieass(fvNumimaeneinlicpowbdepuelmtYslqhaoeuetarunikllwrlti,i:bgosirnMtariakutbutamhoicmte-,f, o - - - 93.94.17
.98 - 0 sthcahtohoal.veEamrluiecrhSintocicosmamccoenpwteidthaArgriusmtoetlnets(sefoerHthaehmce,notpra.lcitiyt.iannnd.i4m,1m0o7b-i1l1it7y).oSfothmeeEthairnthg airn.inf
2 likethelatterviewmustpresumablybeattributedtoCleanthes,whoattackedAristachus c
/03 ofSamosforimpiety(seeAlexanderJones,TheStoicsandtheastronomicalsciences,in ww.
/2 Inwood,op.cit.inn.4,332). w
01 9-Pena(1557),op.cit.inn.5,aaiv(v°),l.1-9. s
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StoicalternativestoAristoteliancosmology:Pena,RothmannandBrahe
fromthecenteroftheuniverse 10.IoannesPenaconcludesthatthe
Earth moves and is not the center of the cosmos – a result possible
inaStoicuniverseconstructedinthemannerofAchillesTatius,but
not an Aristotelian one.
ThemainargumentthatIoannesPenabringsforwardtocontradict
the Aristotelian view of the constitution of the heavens depends
uponobservationsofatmosphericrefraction.Thedeflectionoflight
rays when they cross the boundary between two different media
had been recognized in Antiquity as potentially relevant to astro-
nomical observation. Specifically, if the substance of the heavens
was different from the substances found beneath the Moon in
Aristotle’sgeocentriccosmos,thenthelightfromtheSunorthestars
shouldbedeflectedbycrossingtheboundarybetweentheregions.
Hence, the apparent position of heavenly bodies might differ from
their real position. If, as Aristotle taught, immediately inside the
sphereoftheMoonisasphereoftheelementfirewhichisdistinct
from the sphere of air below it, then a further refraction should
occur at the boundary between these elements 11.
D
ocu Refraction is discussed in book V of the Optics attributed to olin
m ClaudiusPtolemy 12.IntheMiddleAgesAlhazen(Ibnal-Haitham) C
ent téléc aonbdseVrvitaetliloionsoffoSritlheesiayehaard1b4o8t9hBtreerantheadrdthWe saultbhjeercht,aadnndoitnedacshetano-f Armand
ha gesinthepositionsofstarsnearthehorizonduetorefraction 13.The ©
rg lawofrefraction(Snel’slaw)wasnotyetknowninitstrigonometri- 3.
é 1
depu ccarolsfsoirnmg baubtoituwndasarryecforogmnizaedrathreatmtheeddiuemflectotioan doefnasleigmhtebdeiuamm,, 2 04h
is 1
w decreased as the ray came closer to the vertical. If the ray was 20
ww perpendicular to the boundary it experienced no deflection at all. 03/
.c 2/
a So, a simple way to detect the presence of atmospheric refraction 0
irn.info 10-Pena(1557),op.cit.inn.5,aaiv(v°),l.10ff. 7.98 -
- - - 93.94.177 111132---ItsAIAObhsitnrlineyhadEeat.APh,nlzmrebegEebnl.esaisD,srur,ihO°tcr1h-aatvp9orbna°t5rki.nscP8ihsnsh)li,,,apilv2Atoioi7oisfs.1on5ot,hp5uonehrfa.ciOtcneh1adpe,bltaVoOiScnoiostpdkecatliiAiltecnitt.orsyiGM,bw,Our8aiett6rpheek/tdk2iIScnts(mostc1r,ioC9ixetd9hl.na5u6,cu4c)Pe,d.tti(5oiBoCu-lneesa7rmmPa.nnthyboda’rlsierCddmthgoWeyem,,oamsMrleyteehaonesMfstra,.vorO:iyrsHr,ubiTsaasreRlravrp.nvaCesarardotcichoeUteinponnetniisovas,neniornd-:f o - - - 93.94.17
.98 - 0 JtoohrqaunentoSc(Nhouerenmerbe(ergd,.)1S5c4r4ip),tafocll.a4ri4ssirm°i-m60athve°m, 5a2ticvi°M:.«IEosatnnnoistaRnedguimomqounotadnci,irdcea airn.inf
2 horizontem astra apparent propter radios fractos super horizontem, cum secundum c
/03 veritatemsintsubeo,quodinstrumentumarmillarumsensibilitersaepiusmihiapparuit ww.
/2 anteque perspectivas Alhacen & Vitelionis Turingi viderim, [...] » In a marginal note w
01 IoannesPenacitesVitellio,Optics,x.49. s
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PeterBARKER
wouldbetomeasuretheangularseparationoftwostarswhenthey
wereclosetothehorizon,andatthezenith.Withoneofthepairat
the zenith, and the other close to it, any refractive distortion of the
observeddistancebetweenthemshouldbeminimized.Closetothe
horizonthedistortionshouldbegreater,andappearasachangein
the angular distance between the stars 14.
In a book published in 1545 the Dutch physician and natural
philosopherGemmaFrisiusclaimedtohaveperformedtheseobser-
vations and to have found no effect. He reports his failure to find
atmospheric refraction in a work devoted to the use of the radius
astronomicus, which was adopted during the sixteenth century by
both terrestrial surveyors and astronomers to measure angular
separations 15.
In his preface to Euclid’s Optics Ioannes Pena aspires to demons-
trate the utility – indeed the supremacy – of optics as an arbiter in
matters of natural philosophy. He seizes on Gemma Frisius’ nega-
tiveresultasamajorexampleanddrawsconclusionsfromitthathis
D predecessorneverreaches.IfGemmaFrisiusiscorrectandthereis
o n
cu no atmospheric refraction, a result that Ioannes Pena reinforces by oli
m C
ent té ccleanimtuirniegs bthyatall«t[h..e.]fanmoothuisngmelinkewhthoishahvaes cbaereenfulslyeeonbsienrvaeldl tthhee mand
léc stars 16 »,thentherecanbenorefraction-causingboundariesinter- Ar
ha vening between the observer and the fixed stars. The medium in ©
rg 3.
é whichtheobserverisimmersedisair.Hence,negatively,therecan 1
depuis banednoposspihtievreelyo«ffithree,aorrtsopfhoeprteiscsofcothnechluedaevsetnhsa,tatbhoevseptahceeowbhseicrvheirs, 12 04h
ww between the Moon and the fixed stars is full of an airy spirit (hac 3/20
w.c aëris anima plenum est) : I repeat it differs in no way from air 17 ». 2/0
a 0
irn.in This is a devastating conclusion – and likely to be uncongenial to 98 -
fo - - - 93.94.177 11m54u--cRtFGPrreh.aeinnsGmiasuoolmas(lf1’dtasi5soIto5DFne7riaeni)os,ni(fruoenasptddh,e.sie.ocDs),irteFaPe.rslioreentarmvnodnania.naoo5nt’ms,capibsiaecPtbrsnooastvanr.oegoimtesmgiesiaenceonsoemtoeBaetseturtrgaindcetaiooisr,etmdicnienaRctlr.Jime.cG.oeLoceHllhnidbanesnetaerirchitns(Aa,B(CnseRttorewegpmgenerranesprhnk,ats1oga5eonn4nds5u:G)BU.peenFprmniovoamrerrrdaat- o - - - 93.94.177.
.98 - 0 16-sPietynaLi(b1r5a5ry7,),1o9p8.7c)i,t.1i6n7n-1.57,9a,a17ii3i,.ll.12-14:«[...]nectalequicquamtotseculis,totviris airn.inf
2 clarissimisassiduèsyderaobservantibusunquamapparuit.» c
/03 17-Ibid.,aaiiir°,ll.14-17:«Hisaccuratèexaminatis,concluditarsOptica,spatiumillud ww.
/2 quodinterLunametfixasyderamediumest(desummoenimcoelononhabeoquod w
01 dicam)hacaërisanimaplenumesse:abaëre(inquam)nihildistingui.» s
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