Writing on the history of science in 1953 Alfred North Whitehead remarked that ‘In the year 1500 Europe knew less than Archimedes who died in the year 212 BC.’[1] What, then, caused and enabled Copernicus to turn the scientific world on its head? It is necessary to see what Copernicus inherited and what he contributed.
Briefly, his intellectual inheritance included: Aristotle's scientific world-view surviving more-or-less in its original form and also in degraded mystical forms (Dionysius the Areopagite); observations based on Ptolemy's tables were continuing to throw up anomalies (Peuerbach and Regiomontanus); a critical tradition which sought a fuller and better understanding of the Revelation which had been developed within the Church (William of Auvergne, Buridan, Oresme); and, a new approach to knowledge had been developed which can best be described as ‘aesthetic economy’ (William of Ockham)[2].
In cosmology[3] Whitehead's assertion is certainly a seductive point of view, but does not allow for the Arabic[4] and medieval developments in far-ranging detail which brought together after 1500 provided the springboard for Kepler, Galilei and Newton. What is supportable is that Copernicus may be considered to have retrieved the situation regarding the place of the Sun at the centre of the universe which had been put forward by Aristarchus (c310-c230 BC)[5]
An earlier system proposed by Heraclides (c390-c310 BC, and a pupil of Plato) was that Venus and Mercury rotated around the Sun, which in turn circled the earth; and that the Earth turned on its axis[6]. The system of Aristarchus was fully in favour of a central Sun and as a necessary consequence the Earth rotated on its axis thereby providing diurnal motion. These two motions of the earth — annual and daily — obviously (today) go together, but such was not thought to be essential in earlier times when even one motion of the earth ran counter to the prevailing world-picture. It seems that the Greeks were not immune to religious persecution for Plutarchus (c331 - c232 BC) stirred up a popular campaign against Aristarchus accusing him of sacrilege for ‘displacing the Hearth of the world’[7]
These Greek systems were never in the mainstream which was dominated by the Pythagorean/Platonic system, dating from the 6th to the 4th centuries BC, with the Earth a stationary globe at the centre of a swirling universe of homocentric spheres. This was encapsulated in the cosmology of Aristotle (4th century BC) and supported by the mathematical interpretations of observations by Ptolemy (AD c100-c168) who in turn had developed his work from that of Hipparchus (c190-c120 BC).
Whilst the Romans are perceived as taking over the Greek empire, this is a western or Mediterranean view. The Romans expanded into a relatively empty and scientifically primitive western Europe. But from an eastern aspect Greek, along with other cultures, actively survived in continuance of the fragmentary network grown out of the empire of Alexander (356-323 BC) in the Near and Middle East: survived and developed.
The Hindu and Persian peoples particularly made highly significant contributions to scientific thinking which were grafted by the Arabs onto the Greek tree of knowledge. Baghdad, Byzantium (Constantinople after AD 330) and Alexandria were cultural capitals unmatched by Rome and they prospered as Arab centres despite the intrusion of the Roman military into their affairs.
Apparently without exception, the Arabic astronomers (pre- and post-Islamic) retained the geocentric concept without question and for similar (that is, theological) reasons to the Greeks. Additional reinforcement was provided by the account of the ‘nocturnal ascent’ of the Blessed Prophet (Muhammad, AD c570-c632) from Mecca to Jerusalem and then vertically through all the states of being to the Divine Throne itself, all of which is described and (thereby sanctified) in the Holy Book of Islam — the Quran. The journey of the Prophet Muhammed is at once a return to the Source and a delineation of the cosmos which became fundamentally embedded in Islamic thought by the descent of the Holy Quran[8]. The literally explicit Revelation to Muhammad of the cosmos was totally binding on Muslims and brooked no challenge, being the direct word of God to man. But Islam also encouraged the intellectual exploration of the Revelation, and perhaps being unaware of the potential for conflict of ideas and fully confident in their own beliefs, the seeds of the limitations of Islamic science were already sown from the very start. This wedge was fortified by the incorporation within Arabic culture — but not within Islam — of highly influential Jews, Persians, Syrians, Armenians and other peoples of the Near Easts who served or existed within the Islamic empire.
Whilst the Muslims (that is, after the early 7th century AD were completely of the geocentric persuasion this must not overshadow their extensive and positive contributions to astronomy (and science and technology more generally also). It is not possible here to expand on this but it is appropriate to mention that in their need to know the qibla, where Mecca was located relative to their personal position on the planet (and many were nomads), much astronomical work was induced and put to practical use. Furthermore, biblical chronology and the fixing of dates for religious festivals also stimulated astronomical investigations — just as they did in Christian Europe. If for no other reason Christians, from Bede (AD 673-735) onwards, in their search for more and better information looked to Arab sources in science — and cosmology in particular.
In AD 641 the library at Alexandria was sacked with immeasurable loss of manuscripts. The surviving scholars went to Baghdad and Constantinople in the main, where such knowledge was valued. When the Islamic empire spread over north Africa and crossed into Spain in AD 710 the scholars were not long in following and brought with them texts in Greek and Hindu, and other languages of the Near and Middle East. By the ninth century science was flourishing in Arabic Spain, the most important centre being Toledo where most of the ancient texts were translated into Arabic, including the works of Aristotle and Ptolemy. By about 1050 all the significant scientific works of the Hellenistic period were available in Arabic[9].
Following the fall of Toledo to the Vikingsin 1085, access to this established and astonishing centre of translation and extensive archives was provided to scholars who had been alerted to its growing presence in about 1000 by Gerbert of Aurillac (c930-1003, the later Pope Sylvester II). Between about 1125 and 1280 virtually all these manuscripts were translated into Latin by European scholars who visited and worked in Toledo initially and later elsewhere. The work of Gerard of Cremona (1114-87) who translated from Arabic to Latin, and William of Moerbeke (c1215-c1286) from Greek to Latin alone would have sufficed to transform western science and natural philosophy[10]. But the works of neither Aristotle nor Ptolemy could be said to have been known directly north of the Pyrenees before about 1200; a date roughly coinciding with the founding of the universities (as distinct from the cathedral schools such as at Chartres) of Paris, Bologna, and Oxford.
The Caliphate of Cordoba continued in the southern half of Spain into the 1200s when successive wars during that century against the Moors, together with the Christian hostility towards Islam expressed in the crusades (1096-1270), had the effect of shifting the centre of Arabic science back to the lands of the eastern Mediterranean. Astonomical work progressed in several newly conceived observatories, notably at Isfahan (11th century), Maraghah (13th century), and Samarkand (founded 1420). The location of these renowned observatories unparalleled in western Europe until the time of Tycho Brahe (1546-1601) should be noted as being within the ambit of Constantinople and the trade routes established by the Vikings to the Baltic by way of Kiev and the plains of central Europe. When the eastern Roman empire fell in 1453, dispersion of texts and scholars from Constantinope are usually thought of as being transferred directly to Italy; most no doubt were, but there remain the largely unresearched and possible (probable?) connections along the northern, inland trade routes[11].
Without Islamic science and culture it is hard to envisage western Europe being capable of taking up Greek science and philosophy after the Dark Ages, for the inheritance from Rome was scientifically quite inadequate.
The heliocentric theory did, however, survive in post-Roman Empire though not in a really scientific form, rather in commentaries or derivative texts from the Pythagorean/Platonic tradition. In the hands of the Neoplatonists the ideas were kept alive (barely) but without any scientific support. Chacidius (early 4th century AD translated Plato's Timaeus into Latin enablin the scholars of the early Middle Ages to become familiar with Plato's cosmology (geocentric) and with that of Heraclides (geo-heliocentric). Macrobius (c400 AD) and Martianus Capella (c470 AD) both mention the Heraclidean system but not by name. Other encyclopedic authors of the fourth to eighth centuries — Boethius, Cassiodorus, Isidore of Seville — did not expound on astronomical science though Bede explored calendrical matters possibly with influence from early Arabic sources.
The Neoplatonic ‘school’ was elaborated by the so-called pseudo-Dionysius (Dionysius the Areopagite, probably early sixth century AD) who exercised great influence on medieval thought by way of his treatises On the Heavenly and Ecclesiastical Hierarchies. Here he describes the upper reaches of the ‘chain of being’ with a fixed hierarchy of angels attached to the crystal spheres to keep them in motion:
The edicts against Aristotle's commentators during the thirteenth century in Paris had two effects. The first was to clamp down on scientific research and the second to stimulate it. By setting out the banned propositions the issues were clarified and lent themselves to being treated coherently, whereas prior to this the problems were uncoordinated and randomly spread among many authors' works. Thus, those of a conservative nature went to ground whilst those of a more radical nature were prompted to enquire further, albeit cautiously, using primary source material rather than relying on the commentaries. The radical or critical tradition, if it can be so called[13], began as soon as the scientific works of Aristotle began to be available in the Latin west around 1200. But the prevailing current of thought was in favour of the Aristotelian world-view in whatever form — scientific or mystical — it was all things to all men.
An early instigator of the radical tradition was William of Auvergne (c1180-1249), professor of philosophy at the University of Paris and bishop of Paris 1228-49. He aimed to integrate classical Greek and Arabic philosophy with Christian theology and in using non-Christian philosophy from the Arabs (mainly Ibn Sina, or Avicenna, the Persian philosopher and physician 980-1037) ran foul of a Church authority which at that time was driving the Moors out of Spain and warring with Islam in the crusades to the Holy Land (1096-1270). William of Auvergne helped to ‘banish’ angels from the Avicennian universe, preparing the way for a less theological interpretation of the cosmos[14]. But angels make good subjects for paintings and sculptures — a fact not lost on renaissance artists — and which may help to explain the persistence of angelology.
One of the mosts influential of the medieval philosopher-scientists was William of Ockham, the Oxford theologian; a Franciscan, he was firmly against the civil excesses of the papacy. He was in constant conflict with the papal authorities, being tried for heresy at Avignon and excommunicated in Bavaria (1328). His stricture that explanations should not be sought outside of what can be known has affinities with later scientific thought and is a watershed in approaches to understanding the natural world.[15]. William's trenchant attacks on Aristotelian philosophy and ideas concerning force and movement of bodies went largely unheeded in medieval times[16]. However his more general critique of Aristotelian science stimulated others, including Jean Buridan and Nicole Oresme — two outstanding Paris masters of mathematics and physics of the fourteenth century.
Jean Buridan (c1290-c1360) treated the question of diurnal rotation, followed even more convincingly by his former pupil Nicole Oresme (c1320-1382). The vehicle for their thought was provided by the scholastic method of posing and commenting on questions on traditional texts — in this case Aristotle's De Caelo.
Linking terrestrial with celestial notions concerning movement of bodies (mechanics in present-day terms) Buridan recognized that the daily motion of the stellar sphere could be ‘saved’ by the assumption of a stationary heaven and a rotating Earth, or the reverse. He gives the example of a moving ship passing another at rest in the middle of the ocean. If the observer on the moving ship imagined himself at rest, the ship actually at rest would appear to be in motion. Likewise, if the sun were actually at rest and the Earth turned, the appearance to earth-bound eyes would be of the reverse. In strictly astronomical terms the phenomena could be ‘saved’ by either model, and mathematical astronomers who were solely concerned with celestial appearance could employ whichever suited best. But scholastic philosophers were caught up in religious dogma which approved of Aristotle's concept of the universe which included the principle that rest is a more ‘noble state’ than motion. Buridan proposed therefore that it would be more appropriate for the noblest sphere of fixed stars to be at rest and the most ignoble body, the Earth, to rotate. He further assumed that in ‘saving the phenomena’ the simplest means possible would be more desirable; thus if the fixed stars moved they would have to career around the heavens at an astounding speed whereas if the comparatively minuscule earth rotated the relative speed would be immeasurably less. So far, so good.
This argument was reiterated in its essentials by Oresme, Copernicus, and Galilei, but neither Buridan nor Oresme could shake off their cultural inheritance and chose the traditional and theologically acceptable notion of a stationary Earth.
The reason Buridan and Oresme adduced for this was that if an arrow were to be shot into the air vertically it falls to earth at the same spot from which it was loosed; according to his theory of impetus the arrow should fall well to the west. The argument was that the arrow, the air, the Earth, and the observer all moved together due to the rotary motion of the whole system thereby concealing the circular path of the arrow. But Aristotle's concept of impetus did not allow this combination; for Buridan and Oresme, the impetus impressed upon the arrow should enable the arrow to resist the lateral motion of the air as it rotates in concert with the Earth. But experience showed that the arrow did in fact fall at the point of departure; therefor the conclusion must be that the most probable solution was that the Earth was at rest. This was reassuring as it fitted in with the prevailing theological interpretation of the revelation; thus, faith and reason were combined in harmony. All seemed well with the world.
It is characteristic of much of scholastic science that whilst the analysis can be seen to be sound the conclusions often seem irrational or fanciful due to the intervention of external considerations, or not strictly relevant criteria. In this case Buridan employed physics rather than astronomy to resolve the matter — but it also happened to fit in with the Church's approved views.
Whilst most of the ideas of Cardinal Nicholas Cusanus (1401-64) were swept up in the great upsurge of the seventeenth century, his insightful work in science was a stimulant to his successors. Often referred to as a precursor to Copernicus because of his non-geocentric views, his cosmology was a strange mixture of science and mysticism whcih led him to the conclusion that the ‘whole machine of the universe is a sphere which has its centre everywhere, but its circumference nowhere’. Oddly reminiscent of Hoyle's ‘steady-state universe’ of the mid-twentieth century.
But what of observational astronomy in western Europe after the Arab astronomers left Spain? Until the fifteenth century systematic observations were very rare, of negligible importance, and were not conducted in observatories as know to the Arabs[17]. Not until Georg von Peurbach (1423-61), court astrologer to Frederick III, Duke of Austria, followed by his pupil Johannes Müller (1436-76, known as Regiomontanus), also working in Vienna, were any serious contributions made to observational astronomy in western Europe. Although both died young their main, and considerable, achievements were in clarifying Ptolemy's system and demonstrated beyond reasonable doubt that it was incompatible with empirical facts. Thus the technical ground was laid for Copernicus.
If any single contribution is to be thought most highly of in the work of Copernicus (1473-1543) it was that he stood back and looked coolly over the available evidence and drew conclusions from it, stunning in their simplicity. The reason for including the length preamble is that it is as nothing compared to the confusion and complexity that Copernicus had to deal with. From his Revolutions it is clear that he was fully informed of the scientific, mystical and theological literature; and with a clear mind set about disentangling myth from fact, fancy from hard evidence.
When the finished printed book arrived in Copernicus' hands tradition has it that it was as near a posthumous work as it could be, for Copernicus was on his deathbed. Although 1543 is the date of publication, the production of Revolutions had been underway for many years. In the Letter of Dedication (presumably written 1541-42) he refers to having kept hidden the work for ‘not merely nine years but already four times that period.’ Thus, in 1533 his ideas were discussed at the papal court in a friendly atmosphere, partly under the patronage of Cardinal Nicholas Schönberg who had known Copernicus since 1518. Schönberg is first among the dedicatees, after Pope Paul III to whom the Preface is addressed[18]. In 1507-08 Copernicus had produced in manuscript what amounts to a first version of his astronomical thought. This work was the Commentariolus and it sets out his heliocentric theory in an undeveloped way; he provides the criticism of the existing world-views and outlines his proposals, but saves ‘mathematical demonstrations, reserving these for my larger work’[19].
Copernicus' duties as Canon at Frombork[20] in the service of the Church involved considerable work as administrator, lawyer and physician to the bishop. Until his death in 1512 the Bishop of Ermland was Copernicus' uncle, Lucas Waczenrode, and Copernicus served several subsequent bishops and chapters in this Catholic outpost surrounded by Protestant territory. Tiedemann Giese was a member of the chapter for over twenty years before he was mad Bishop of Kulm; Giese was the second dedicatee. But it was not entirely weight of work which restrained Copernicus in completing and publishing the Revolutions.
Being of a modest disposition he was aware of the probability of being scorned by the ignorant, and pointed in his Letter of Dedication to the example of the Pythagoreans who did not publish their work for this reason. However, the main cause probably lies in that he felt that he had not altogether adequately proved the proposition other than by, or from, circumstantial evidence — but this, after all, is all there was. He required encouragement and/or persuasion to publish and this came from the twenty-five year old Protestant professor of mathematics, one Georg Joachim known as Rhaeticus from his place of birth, the Austrian Tyrol. Vienna was still (after Peuerbach and Regiomontanus) virtually the only place in western Europe engaged in observational astronomy and a further connection is that Regiomontanus began the astronomical institute in Nuremburg during 1471-75. Philip Melancthon had selected Rhaeticus to be professor at the age of twenty-two at the recently founded University of Wittenberg, the hotbed of Protestantism. Martin Luther, of course, was professor of Biblical Exegesis also at the small-town University of Wittenberg, from 1512 to 1546.
Rhaeticus arrived unannounced in Frombork in the spring of 1539 to seek-out Copernicus and obtain more and better particulars of the new astronomical system of which he had received reports. He brought with him several newly published scientific works which Copernicus did not possess though he may have seen earlier. Immediately Rhaeticus set to work on the manuscript which Copernicus had already produced by that date. in 1540 Rhaeticus had published, with the consent of Copernicus the First Account (Narratio prima), which was a resumé dealing solely with the motion of the Earth. Only at about this time, it appears, did Copernicus decide to publish his larger work, possibly encouraged by the reception of the First Account, and he asked Rhaeticus to see it through the press. When Rhaeticus left Frombork in the autumn of 1541 he took with him the complete, though unedited manuscript by Copernicus. The signs of haste in the manuscript are due to last minute completion or re-writing rather than of the complete writing in a short space of time[21].
Printing by Johannes Petreius in Nuremburg was delayed until the spring of 1542, probably because of reservations expressed to Rhaeticus by Melancthon, and additionally by Rhaeticus taking on the demanding duties of dean at Wittenberg. Later that year Rhaeticus had to leave Nuremburg and Wittenberg for Leipzig where he had obtained another post as professor of mathematics; thus the business of supervising publication was left to a colleague. In this way Andreas Osiander, one of Luther's ‘inner circle’[22], became involved with the publication, though he had corresponded with Rhaeticus and Copernicus in 1540. His impact on the book was significant, for he appended an anonymous Preface which went entirely against what Copernicus had set out to achieve[23].
Copernicus had bitten the bullet and put forward the heliocentric theory and all its implications as substantive fact. But Osiander considered that because an astronomer cannot ‘attain to the true causes’ he must ‘conceive and devise the causes of [these] motions or hypotheses’, and ‘these hypotheses need not be true or even probable’. Nowhere did Copernicus mention ‘hypothesis’ in connection with his own system, and his language is non-inflammatory in favour of heliocentricity. Maybe when Copernicus read the book on his deathbed it was this treachery that hurried him to his grace.
Osiander was correct, however, in that the evidence available to Copernicus was not sufficient in itself to completely overthrow the conventional system. And caution, he felt, would be prudent. Interestingly, though, it was not fear of the Catholic Church that prompted this action (for Copernicus' work already had actual or tacit approval from that quarter), but the Protestant reaction. Osiander probably knew of Luther's and Melancthon's reservations concerning the proposed motion of the Earth which went counter to the biblical record. These qualms were nothing to do with the failure of the Aristotelian world-view, nor with the lack of consonance in the astronomical observations held together in the Ptolemaic tables; it was all to do with biblical exegesis, and this was Luther's professional subject.
The book comprises the letter from Schönberg to Copernicus urging publication, the Letter of Dedication to Pope Paul III, two Prefaces (one by Copernicus and the anonymous one), and the work itself in six ‘books’ or sections, each divided into chapters.
In his own Preface, Copernicus explains to the Pope the reasons for putting forward his ideas. The chief one is that Aristotle's theory was vague and was not supported by observation or mathematical tables showing planetary movements; whereas Ptolemy's theory based on his tables (even as brought up to date by Peuerbach and Regiomontanus) was internally contradictory and contravened the laws of physics. As two, clearly unsatisfactory, theories were already being entertained there could be no objection in indicating a third, superior system. The final reason was that the calendar needed reforming, about which Copernicus had been consulted by the papacy in 1514.
The contents may be briefly summarized:
For a scientific theory to carry weight it must not only show up the errors or faults of earlier theories, but make proposals for new and better. In his critique, Copernicus refers to all the objections to Aristotle and Ptolemy provided by Buridan, Oresme and others (whom he names), but breaks free of their self-imposed constraints which led them back to the Revelation of God as an Aristotelian experience. He also mentions the explorers of Spain and Portugal destroying Ptolemy's geographical description of the world (for example, it was found that people did indeed live in the equatorial regions).
In support of his system, Copernicus calls upon earlier astronomers from ancient Greece — including Philolaus the Pythagorean, Heraclides, and Aristarchus. He mentions all the Roman literary contributions and includes Plutarch, Cicero, and Virgil, for good measure. He stays clear of any Arabic citations. But it would be too strong a conclusion to say that Copernicus was prompted by ancient astronomy towards his conclusions. The reading of his text suggests that whilst he is pleased to have found their support he had arrived at the same conclusions on the basis of the physical evidence he had to hand. Ancient Greek authorities obviously would carry great weight in the early days of the scholarly renaissance and it is natural that he should have brought them to line up with him against the:
‘babblers who, although completely ignorant of mathematics, nevertheless take it upon themselves to pass judgement on mathematical questions and, improperly distorting some passage of Scripture for their purpose, dare find fault with my system and censure it, I disregard them even to the extent of despising their judgement as uninformed.’[24]
Introducing the analogy of the universe as a machine (machina mundi) Copernicus goes on to say that the followers of Ptolemy can have only a partial picture of the universe which is ‘more like a monster than a man’ because whilst the individual limbs are shaped beautifully they are without correspondence one with another. This refers to Ptolemy's scheme which required a separate diagram for the motion of each planet; Copernicus reduced this to a single diagram for the entire universe. This gestalt approach finds echoes in other innovators such as Alberti in architecture writing in about 1450, but published in 1485. Simplicity and order was the programme of the times in the explanatory sciences and creative arts, and perhaps this assists in explaining how Renaissance Man could switch from one of C.P. Snow's cultures to another so readily.
With medieval resonances, but with his new system in mind Copernicus writes:
‘Every observed change of place is caused by a motion of either the observed object or the observer or, of course, by an unequal displacement of each. For when things move with equal speed in the same direction, the motion is not perceived as between the observed object and the observer, I mean. It is the earth, however, from which the celestial ballet is beheld in its repeated performances before our own eyes.’[25]
It would take a longer essay than this to present the astronomy of Copernicus in any detail. Its main conclusions are well enough known, but there was much still to do in order to bring the system into a recognizably modern form. Most notably, Copernicus clung onto the Pythagorean idea of circles; and just as the adherents of Ptolemy's system had to do, he found it necessary to incorporate secondary motions of the planets to accord more closely with observation. Even so the orbit of Mars was not satisfactorily provided for and it was this feature that led Kepler to make the next jump in concept development. This was the idea that the orbits were elliptical and swept out equal areas in equal times. It was in compensating for ellipticality that both Ptolemy and Copernicus found the need to provide the ‘wandering’ planets with secondary motions based on non-fixed centres. There was still much to do, but Copernicus made a fresh start.
But why Copernicus, and not someone else? Perhaps his particular circumstances were influential. In addition to a clear and inquisitive mind, allied with intellectual courage the facts of his religious convictions and cultural context were surely significant. He was of the Church but not in holy orders; he was a devout Catholic, some distance from Rome and surrounded by Protestants, many of whom he knew well enough to recognize fellow-feeling; he was extremely well-read and did not have to parade his obedience in public sermons. Had he been born and brought up in an entirely Catholic area, or had he been a Protestant in Protestant Germany, would he have made the same contribution to cosmology?
A.N. Whitehead, Science and the Modern World, (Cambridge, 1953), p15.
D. Hill, Islamic Science and Engineering (Edinburgh U.P. 1993), pp 1-14.
E. Grant, Planets, Stars and Orbs: The Medieval Cosmos, 1200-1687 (Cambridge U.P., 1994), p 13.
Dante, Convito, ii. 6. Quoted by Koestler, The Sleepwalkers (Arkana edition, 1989 [1959], p 98.
K. Popper, Conjectures and Refutations (Routledge and Kegan Paul, London, 1974 [1963]), ch 4.
S.H. Nasr, Islamic Cosmological Doctrines, revised edition (Thames & Hudson, London, 1978 [first Harvard 1964]), p 185.
Entia non multiplcanda praeter necessitem — entities are not to be multiplied without necessity.
Pope Paul IIIis considered to have been intelligent, humane, and scholarly. Copernicus felt secure in dedicating the book to him.
Usually referred to in the literature of science as a ‘local Lutheran clergyman’.