The CopernicanmythsMano Singham

The real story of how the scientific and religious establishments greeted^ e Copernican revolution is quite different from the folklore. And it̂ s a lotmore interesting.

Mano Stngham is director or the University Center for Innovation in Teaching and Education and adtunct associate prphysics at Case Western Reserve University in Cleveland, Ohio.

Perhaps the most famous of all sdentiHc revolutions isthe one associated with Nicolaus Copernicus (1473-1543).The popular version of the story goes as follows:

The ancient Greeks, although they were greatphilosophers and good at mapping the motionsof stars and planets, tended to create models ofthe universe that were more influenced hy philo-sophical, aesthetic, and religious considerationsthan by observation and experiment. The ideathat Earth was the stationary center of the uni-verse, and that the stars and planets were em-bedded in spheres that rotated around Earth, ap-pealed to them because the circle and the spherewere the most perfect geometric shapes.

In the Christian era, the model also pleasedreligious people because it gave pride of place tohuman beings—God's special creation. The pres-tige of Greek philosophers like Aristotle was sogreat, and commitment to religious doctrine sostrong, that many scholars stubbornly tried to re-tain Ptolemaic astronomy even though increas-ingly complicated epicycles had to be added tomake the system work even moderately well.

So when Copernicus came along with the cor-rect heliocentric system, his ideas were fiercelyopposed by the Roman Catholic Church becausethey displaced Earth from the center, and that wasseen as both a demotion for human beings andcontrary to the teachings of Aristotle. Thereforethe Inquisition persecuted, tortured, and evenkilled those who advocated Copernican ideas.

Because of the church's adherence to philo-sophical and religious dogma, scientific progresswas held back for a millennium, It was the laterwork of Tycho Brahe (1546-1601), Johannes Kep-ler (1571-1630), Galileo Galilei (1564-1642), andIsaac Newton (1642-1727) that finally led to theacceptance of heliocentrism.

Variations on this breezy version of the Copernicus storyare common in science textbooks.' How much of the storyis true? Apart from the final sentence, not much. But it's agood illustration of how scientific folklore can replace actualhistory.

Let us start with the myth that the Copernican modelwas opposed because it was a blow to human pride, de-throning Earth from its privileged position as the center of

the universe. Der\nis Danielson, in his fine article on the sub-ject,' shows how widespread that view is by quoting the em-inent geneticist Theodosius Dobzhansky. With Copernicus,Dobzhansky contends, "Barth was dethroned from its pre-sumed centrality and preeminence." Carl Sagan describedCopemicanism as the first of a series of "Great Demotions..,delivered to human pride." Astronomer Martin Rees haswritten, "It is over 400 years since Copernicus dethroned theEarth from the privileged position that Ptolemy's cosmologyaccorded it." And Sigmund Freud remarked that Copernicusprovoked outrage by his slight against humankind's "naiveself-love."

The squalid basementDanielson, however, points out that in the early 16th century,the center of the universe was not considered a desirableplace to be. "In most medieval interpretations of Aristotelianand Ptolemaic cosmology. Earth's position at the center ofthe universe was taken as evidence not of its importancebu t . . . its grossness,"

In fact, ancient and medieval Arabic, Jewish, and Chris-tian scholars believed that the center was the worst part ofthe universe, a kind of squalid basement where all the muckcollected. One medieval writer described Earth's location as"the excrementarj' and filthy parts of the lower world." Wehumans, anotlier asserted, are "lodged here in the dirt andfilth of the world, nailed and rivetted to the worst and dead-est part of the universe, in the lowest story of the house, andmost remote from the heavenly arch." In 1615 CardinalRobert Bellarmine, a prominent persecutor of Galileo, saidthat "the Earth is very far from heaven and sits motionless atthe center of the world/'-

In Dante Alighieri's Vte Divine Comedy, hell itself isplaced in Earth's innermost core. Dante also speaks of hell inways consistent with Aristotelian dynamics—not full offlames, which would be displaced skyward by the heavierEarth, but as frozen and immobile.

By contrast, heaven was up, and the further up you went,away from the center, the better it was. So Copernicus, by put-ting the Sun at the center and Earth in orbit around it, wasreally giving its inhabitants a promotion by taking themcloser to the heavens.

When and why did the history become distorted?Danielson doesn't pinpoint when the erroneous view gainedsupremacy. But he says that trom 1650 onward one can findsome writers making this revisionist claim. By the late 18thcentur}' it had taken hold completely. Johann Wolfgang von

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Goethe (1749-1832), for example, wrote: "Perhaps no dis-covery or opinion ever produced a greater effect on thehuman spirit than did the teaching of Copernicus. No soonerwas the Earth recognized as being round and self-contained,than it was obliged to relinquish the colossal privilege ofbeing the center of the world." Here Goethe managed topropagate another major distortion: the notion that beforeCopernicus (and Columbus) it was not known that Earth wasa sphere.^^

Aristotle's cosmologyEven Aristotle did not believe Earth to be the center of theuniverse. He thought it rather to be at the center. This finedistinction was not driven by religious dogma or human self-impurtance but by physics arguments: In Aristotle's cosmol-ogy the universe was finite and the heavens existed beyondits outermost sphere. The universe had a center—defined asthe center of the large outer sphere in which the stars wereembedded — and matter was d rawn to that center. In that cos-mology, "up" and "down" were well defined. "Down" wastoward the center of the universe and "up" was away fromit, toward the sphere containing the stars.

The elements were earth, air, water, and fire, and eachelement had its natural affinity for a location in the universe.As could be seen from the fact that rocks fell to the ground,earth, being heavy, was drawn to the center. Flames leapingupwards showed that fire, being light, was drawn towardsthe heavens. The model explained many things, such as whyobjects fell to the ground when released from any point andwhy Earth's surface was spherical. It also explained whyEarth was motionless at the center. For it to move, there

Nicolau5 Copernicus (1473-1543) [Courtesyof AIP Emilio Segre Visual Archives.)

would have to be something that took itaway from the center. And no such agent wasin evidence.

In his book The Copernican Revolution, his-torian Thomas Kultn ptiinted out that Aris-totle was clearly saying that Earth was at thecenter of the universe not because it was es-pecially important but simply because it wasmassive: "It so happens that the Earth and theUniverse have the same center, for the heav-enly bodies do move towards the center of theEarth, yet only incidentally, because it has itscenter at the center of the universe."^

Problems with heliocentricityCopemicus's heliocentric model, on the otherhand, created all manner of difficulties. It re-quired Earth to be in motion, but it did notsay what caused it to move away from thecenter. If Earth was not stationary at the cen-ter but was midway in the sequence of plan-etary orbits around the Sun, how could youdefine "up" and "down"? Why would ob-jects fall "down" if Earth were not at the cen-ter of the universe? How could objectsthrown upward fall back to the same point ifEarth was not at rest? Earth was still believedto be the most massive object in the universe.So if it was not drawn to a fixed point at thecenter, did that mean that the universe hadno center? Could that mean that the universe

was infinite?Kuhn argues that there were thus excellent reasons for

rejecting the upstart Copernicus and retaining Aristoteliancosmology and its elaboration in Ptolemaic astronomy. Ac-cepting Copernicus would not simply replace one astronom-ical model with another. It also meant that a whole class ofphysics problems that had been considered solved were nowsuddenly unsolved. Therefore much of the initial resistancecame from within the physics and astronomy contmunitiesrather than from the church.

In fact, awareness of Copemicus's work was at firstlargely restricted to the community of astronomers. Onlythey were interested in improving the calculation of plane-tary motions. Copernicus was widely respected as one of Eu-rope's leading astronomers, and reports about his work, in-cluding his heliocentric hypothesis, had been circulatingsince 1515. So when his Df RcvoluHonibu? Orbium Coelcslium(On the Revolutions of the Celestial Spheres) was published28 years later, it was hardly a surprise to other astronomers.They accepted it as the most comprehensive account of ce-lestial motions since Ptolemy.

But most astronomers also felt that the Ptolemaic system,although complicated, could ultimately he made to work. Sowhile they hailed Copemicus's work and used his tables andmethods, they were skeptical of his central idea of a movingEarth. They dismissed it as an ad hoc trick (much as MaxPlanck's quantum hypothesis was initially viewed centurieslater) that turned out to be a useful tool for calculations. Tlieidea that the motion described by some artificial model wasa convenient fiction was not unprecedented. Ptolemy himselfhad said that not all of his epicycles had to be considered

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Initially, however, the Copernican system did not givebetter numerical rosults than the I'tolemaic. Part of the prob-lem was that some of the existing astronomical observationswere simply erroneous, a problem that plagued Ptolemaicand Copemican astronomy alike. Although better observa-tions soon eliminated some ot̂ those problems, other prob-lems remained obdurate for a long time. Furthermore, at thelevel of accuracy available to Copernicus, the introduction ofellipses in place of circular orbits would not have helped.What Copernicus needed to do, as historian Owen Gingerichputs it, was to "treat Earth and MercT.iry the same way as theother planets."

Kuhn says of Copernicus: "His full system was little ifany less cumbersome than Ptolemy's had been. Both em-ployed over thirty circles; there was little to choose betweenthem in economy. Nor could the two systems be distin-guished by their acairacy. When Copernicus had finishedadding circles, his cumbersome sun-centered system gave re-sults as accurate as Ptolemy's, but did not give more accurateresults. Copernicus had failed to solve the problem of theplnnots.'"'

AdvantagesThe Copernican model did have some aesthetic and qualita-tive advantages. It provided a more natural qualitative ex-planation for the zigzag motion of planets like Mars as ob-served from Earth, and it answered some importantquestions about the ordering of the planets. That's why he-

Frontispiece of a 1566 edition of Copernicus's De Revolution-ibus Orbium Coeiestium, published in Basil, Switzerland. Thework was first published o few months before the author'sdeath in 1543.

Johannes Kepler (1571-1630) at age 39. (Courtesy of theKremsmunster Observatory.)

liocentrism was eventually accepted. As Kulin puts it, "DeRei'olutionibus did convince a few of Copemiais' successorsthat sun-centered astronomy held the key to the problem ofthe planets, and these men finally provided the simple andaccurate solution that Copernicus had sought.'"^

That's an important point about scientific revolutions. Atthe start, the new theory rarely gives convincingly better re-sults than its predecessor. What usually happens is that it hassome appeal, often aesthetic, that attracts others to workwithin the new model. And if, over time, the new modelproves fruitful in resolving many puzzles, it gains adherents."

The success of the Copernican model was aided by thework of the Danish astronomer Tycho Brahe, who died a fewyears before the invention of the telescope. Tycho is consid-ered the greatest of the naked-eye observers. His wide-ranging and accurate observations had an em>rmous impact.

Although Tycho's pivotal role is recognized, what is It'sswell known is that he, like most astronomers at the time, re-jected Copernicus's ideas of a moving Earth. It created more

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problems, he thought, than it solved. But despite Tycho's op-position, his observations provided two major benefits for theheliocentric model: They got rid of some erroneous old datathat had plagued all the earlier models and thus helped to re-move some of the anomalies that the Copernican systemcouldn't explain. More important, the precision of Tycho'sdata provided puzzles that enabled Kepler, a convert toCopemicanism, to come up with the key idea that the mo-tions of the planets were not circular—as Ptolemy, Coperni-cus, and Tycho had all assumed— but elliptical.

In the folklore that surrounds Copernicus, the introduc-tion of elliptical orbits is rightly recognized as a crucial de-velopment that led to ultimate acceptance of his model. Thepre-Keplerian astronomers, however, are unfairly character-ized as insisting on circular motion because of aesthetic con-siderations, slavish adherence to the authority of the Greeks,and so forth. But at the time, the reasons for assuming circu-lar motions were quite sensible. Because there were no goodtheories of force or gravity, one needed to have an explana-tion of motion. Circular motion could be explained by a plau-sible hand-waving argument. One could say that it was aninitial condition —that once an object had been set in circularmotion it would, if undisturbed, continue circling forever.

More complicated motions like elliptical orbits wouldmean that the planets' speeds and distances from the Sunwere constantly changing. But that required a dynamical the-ory that simply did not exist in those pre-Newtonian times.Just introducing the idea of a moving Earth created all kindsof unsolved problems for the physical theories of the day.Adding noncircular motion would have compounded thoseproblems, providing even stronger grounds for rejectingCopernicus.

Kepler's innovative idea of elliptical orbits, coupled withhis law of areas, did let the Copernican model dispense with

Galileo Galilei (1564-1642) as drav/n byOttavio Leoni around 1624.

cumbersome epicycles. But his accurate RudolyhincTables for planetary motion, published in 1627, weredifficult to use. It was Newton's theories of motionand gravity, not published until 60 years later, thatsealed the scientific case in favor of Copernicus byputting his model on a firm theoretical footing.

Religious objectionsriie actual religious reaction to the heliocentric modelalso differs from the folklore. For one thing, Copemi-cus did not seem to fear religious opposition to hisideas. After all, he was a reputable cleric himself. Heeven dedicated his bixik to Pope Paul 111 witli a letterin which he apologized for the seeming outlandish-ness of his suggestion that the Earth moved. He ex-plained that he was forced to tliat hypothesis by theinadequacy of the Ptolemaic .system for constructingcalendars and predicting the positions of stars. A car-dinal and a bishop were among those who urged himto publish his book. In fact, for 60 years after Coper-nicus's death just two months after its publication, DcRevoiutionihm was read and at least partially taughtat leading Catholic universities.

In 1600 the church did bum at the stake thephilosopher Giordano Bruno, an adherent of Coper-nicus, for heresy. But Bnmo was condemned forother heresies against Christian doctrine rather than

explicitly for being a (Topernican. However, the fact thatBruno had been an advocate and popularizer of heliocen-trism may have led to the later perception that he was the firstmartyr of the new science.

For many years after the publication of De RevohtHonibus,while Copernicus's ideas remained within the mathematicalastronomy community, authors of more popular books on as-tronomy and cosmology were either unaware of his work orchose to ignore it. A few nonastronomers did ridicule it—notfor being heretical but for promulgating the patently absurdidea of a moving Earth.

It was through popularizers, some of them poets, thatCopemicus's ideas eventually became more widely known andbegan to spark religious opposition. But here too, Uie actual his-tory is surprising. Opposition arose initially among Protestantgroups rather than from the Roman Catliolic Church.

Kuhn suggests that this was because Martin Luther(1483-1546) and other leaders of the Reformation were em-phasizing the Bible as the fundamental source of Christianknowledge and authority. And there were manifest contra-dictions between the Bible and Copemicus. The CatholicChurch, by focusing more on doctrinal issues, actually hadgreater flexibility in dealing with science.

Luther spoke out against heliocentrism in 1539, sayingthat the idea of a moving Earth going around a stationary Sunclearly went against the account in the book of Joshua thatsays Joshua commanded the Sun to stand still. Luther'sdeputy Philipp Melanchthon followed up by finding otherbiblical verses that described Earth as stationary.

The conflict between scripture and Copemicanism wasnot limited to verses that involved the motion of Sun or Earth.The realization was growing that acceptance of Copemican-ism raised other profound theological difficulties as well. AsKuhn points out, the problems just kept multiplying:

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When it was taken seri-ously, Copernicus' pro-posal raised many giganticproblems for the believingChristian. If, for example,the Earth were merely oneof six planets, how werethe stories of the Fall andof the Salvation, with theirimmense bearing onChristian life, to be pre-served? If there were otherbodies essentially like theEarth, God's goodnesswould surely necessitatethat they, too, be inhabited.But if there were men onother planets, how couldthey be descendants ofAdam and Eve, and howcould they have inheritedthe original sin? . . . Again,how could men on otherplanets know of the Saviorwho opened to them thepossibility of eternal life?Or, if the Earth is a planetand therefore a celestialbody located away fromthe center of the universe,what becomes of man's in-termediate but focal posi-tion between the devilsand the angels? If the Earth, as a planet, partici-pates in the nature of celestial bodies, it cannotbe a sink of iniquity from which man will long toescape to the divine purity of the heavens. Norcan the heavens be a suitable abode for God ifthey participate in the evils and imperfections soclearly visible on a planetary Earth. Worst of all,if the universe is infinite, as many of the laterCopemicans thought, where can God's Thronebe located? In an infinite universe, how is man tofind God or God man?''

As time went on, Copemicus's Ideas were seen as seri-ously disturbing to Christianity; they had to be countered.Soon the Bible became the main weapon used against Coper-nicus. Protestant and Catholic derics in the 17th centurystarted combing through it for ammunition. People startedcalling the Copemicans infidels and atheists and urged theirrepression. But the new Protestant churches did not have thepowers of suppression and enforcement that the long-established Catholic Church had.

Kuhn argues that it was probably the menace of bur-geoning Protestantism that caused the Catholic hierarchy in1616 to switch abruptly from tolerance of Copernicanism torepression. "Copemican doctrines were, in fact, condemnedduring the Counter Reformation, just when the Oiurch wasmost convulsed by internal reforms designed to meet Protes-tant criticism. Anti-Copernicanism seems, at least in part, oneof these reforms. Another cause of the Church's increasedsensitivity to Copernicanism after 1610 [the year Galileo firstturned a telescope to the heavens] may well have been a de-layed awakening to the fuller theological implications of theEarth's motions. In the I6th century those implications hadrarely been made explicit.'"'

Giordano Bruno, burned at the stalce as a heretic in1600, was honored in 1 887 with the erection of thisstatue at the site of his execution in Rome's Campodei Flori. Although Bruno was condemned by the In-quisition primarily br theological heresies ratherthan for his advocacy of heliocentrism, he iswidely regarded as the first martyr of the scien-tific revolution.

The ide.i ot the Copernicanmodel being a demotion for hu-manity probably first developedaround 1650, after tlie scientificcommunity had already acceptedheliocentrism. Religious bodies un-dertook what was essentially apropaganda war against Copenii-cus. What probably happened wasthat after the heliocentric model hadbeen well established, the liKation ofthe Sun did come to be perceived asa privileged place. So people readback into history the newly believedexcellence of the center and attrib-uted that belief retrospectively to thepre-Copernicans. The demotionidea may have been introduced aspart of the effort to rally nonscien-tific religious people to tum againstCopernicanism by appealing totheir pride as human beings.

The Protestant churches aban-doned their opposition to Copemicanism fairly quickly whenit became clear that the evidence in favor of a Sun-centeredsystem was overwhelming. But the Catholic Church, being amuch larger and more tradition-bound and bureaucratic in-stitution, was left clinging to its anti-Copemican views for along time. Its ban on Copernicus remained until 1822, and hisbook remained on the forbidden list until 1835. In fact it wasonly in 1992 that Pope John Paul II lifted the edict of inquisi-tion against Galileo. Thus the Roman Catholic Church is nowgenerally regarded as the principal villain in perhaps themost notorious episode in the history of science.

What can we learn from all this? The story of the Coper-nican revolution shows that the actual history of science oftenbears little resemblance to the popular capsule versions thatare learned in school or college or portrayed in textbooks andthe popular media. Steven Weinberg calls them "potted his-tory." TTie true story is much more complicated, but it's alsoa tot more interesting.

My thanks to Ouvn Gingerich for an enlightening discussion andmany helpful suggestions.

ReferencesL See, for example, P. Fishbane, S. Ga.siorowia!;, S. Thomton, PJri/s/cs

for Scientists and Engineers, 2nd ed., I'rentice Hdll, Upper SaddleRiver, NJ (19%), pp^ 1, 320, 321.

2. D. R. Danieison, Airi.}. Phys. 69, 1029 (2001).3- M. Singham, Phi Delta Kapyan 88, 590 (2007).4. J. B. Russell, hiventing the Flat Earth: CDlumhu^ and Modem Histori-

ans, Praeger, New York (1991).5. T Kuhn, TIte Copernican Rei>clulioii: Phinctary Aatrononiy in the

De^vlopment of Western Thought, Harvard U, Press, Cambridge,MA (1957).

6. I. Lakatos, The Methodology of Scientific Research Programmes, Cam-bridge U. Press, New York (1978). •

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