Now the great Bear and Pleiades where earth moves
Are drawing up the clouds of human grief,
Breathing solemnity in the deep night.
Who can decipher
In storm or starlight
The written character of a friendly fate—
As the sky turns, the world for us to change?
But if the horoscope’s bewildering
Like a flashing turmoil of a shoal of herring,
Who can turn skies back and begin again?

—Montague Slater, libretto for Peter Grimes, Act I, Scene 2

We who awaken with the sun and sleep beneath the stars, we whose busily earthbound lives can still be pulled up short by the sudden sight of a full moon, even we know that our existence is patterned on the movement of the heavens. In some senses, moreover, we are no closer to understanding those patterns than the Pharisees and Sadducees so famously challenged by Jesus in the Gospel of Matthew:

When it is evening, ye say, It will be fair weather: for the sky is red. And in the morning, It will be foul weather today: for the sky is red and lowering. O ye hypocrites, ye can discern the face of the sky; but can ye not discern the signs of the times?

(Matthew 16:1–3)

The fact is that, with our scientists and weathermen, we are still unable to carry out the work of discernment with perfect precision, any more than the Pharisees, Sadducees, astrologers, fortunetellers, scribes, philosophers, and magi of Roman-ruled Palestine could do so two thousand years ago. Always, however, it has been an inveterate human temptation to connect these different kinds of discernment, to believe that somehow the face of the sky is the sign of the times.

Remarkably, one of the most cataclysmic upsets in our own reading of the heavens occurred before the invention of the telescope. Nicolaus Copernicus (1473–1543) published his On the Revolutions of the Heavenly Spheres in 1543, half a century before Galileo Galilei ever pointed a telescope at the moon and sketched its pockmarked countenance. During the sixteenth century, the two sciences that focused specifically on reading the face of the skies, astrology and astronomy, began the separation proceedings that would eventually lead to their divorce. In Copernicus’s day both of these starry pursuits involved highly complex studies based on intimate observation of the heavens. Their difference lay in how their practitioners interpreted the same data.

Girolamo Cardano (1501–1576), for example, was an astrologer, a younger contemporary of Copernicus who sought information about the stars just as avidly as his Polish counterpart. Anthony Grafton’s new biography, Cardano’s Cosmos: The Worlds and Works of a Renaissance Astrologer, accords Cardano all the respect the crusty Italian’s industry and intelligence once warranted without question. As Grafton says, “I wanted to do justice to both the rationalism and the irrationality of Renaissance astrology, to both its traditional and its novel contents, to both its ancient sources and its modern social role…. Above all, I wanted to be surprised.” Happily, his book delivers satisfaction on all these accounts.

Some of the irrationality of Cardano’s astrological enterprise originated in the man himself, a self-absorbed, eccentric polymath who openly admitted at least some of his own flaws: “I lack piety and have an uncontrolled tongue, and my temper is so quick that I am sick with the shame it causes me.” But then Cardano, like so many outstanding figures of the European Renaissance, was a self-made phenomenon who overcame illegitimate birth and its attendant poverty to become a figure of international renown. He did so by exploiting his many-faceted ingenuity, his pen, and the power of the printing press. Still, as Grafton shows with great empathy, the process was never easy.

In his own day Cardano was regarded as an expert on medicine and astrology—linked disciplines—along with mathematics, palmistry, and anatomy (his two manuscript works on this subject, he alleged, were spoiled by an incontinent cat). An inveterate gambler, he parlayed his vice into one of the earliest essays on statistics, The Book on Games of Chance. He wrote an introspective autobiography in Latin, On His Own Life, and an oft-reworked volume On His Own Books. But Cardano’s most revealing métier, as Grafton’s biography proves by example, was always the delicate blend of psychology, fortunetelling, astronomical observation, and publicity-mongering that went into the profession of astrology in the mid-sixteenth century.

After some years spent as a country doctor in the hinterlands of Padua and Milan, Cardano began to pursue his true calling in the 1530s, the very years when Copernicus was drafting his own dryly mathematical description of the cosmos through a series of numerical tables. Copernicus told his readers how the heavens moved; Cardano, working from a traditional earth-centered perspective, told them what those movements meant. His first published effort was a cheap pamphlet of predictions, the Pronostico (Prognostication) of 1534. In this work, a good example of an extraordinarily popular form of literature in the mid-sixteenth century, he offered inside information on the long-term trends of history and detailed reports on forthcoming weather, all based on reading the face of the heavens: “I say in general that men must become worse than they are now, so far as the faith is concerned,” but, he said, the Church would begin to improve in 1764; a planetary conjunction in 1564 “denoted the renovation of all the religions, the Christian and the Muslim.”


According to Cardano, Emperor Charles V was doomed to perish (instead he thrived); Francesco Sforza, duke of Milan, to thrive (instead he perished); drought would strike between July 6 and August 9 of 1536, fog and storms on August 25, 1537. Aiming at a popular readership, Cardano wrote his little almanac in Italian vernacular, with enough of an erudite sprinkling of Latin to lend him academic credibility, and he made sure that he acquired clear-cut privileges, the forerunner of copyright, for the work in both Milan and Venice. It was a modest start, and it sank virtually without notice.

Four years later, however, Cardano, writing in Latin this time, hit his stride. His Two Little Books of 1538 displayed both his grasp of astronomical theory and his practical ability at prediction, that is, at astrological reasoning. Unlike most of his fellow astrologers, he drew up his own tables of planetary motion from which to produce the data allegedly showing influences on human character and behavior; at the same time he performed such eminently astrological operations as tracing the origins of modern religion to the former action of the stars on ancient peoples. Furthermore, Grafton tells us, he used the dedication of the Two Little Books to curry the favor of a well-placed patron, the Milanese-born governor of Rome, while aiming at a patron still more august, the Pope.

During the rest of his life Cardano tried to improve his observational skills, in medicine, mechanics, and mathematics as well as in following the movements of the stars. He made predictions that balanced optimism with calamity without erring too egregiously. He lambasted his rivals and found well-heeled sponsors for his work. In all of these efforts he succeeded splendidly, traveling as far as Paris and Edinburgh to cast the horoscopes of important clients (in Scotland it was that country’s last Catholic archbishop), writing books that sold well, eventually teaching, as Grafton writes, “with some success and considerable notoriety” at the universities of Pavia and Bologna.

He came to the attention of the Inquisition, but defended himself effectively against its inquiries. Cardano’s brand of astrology, based in careful astronomical observation, still managed to bridge what were rapidly becoming two cultures of stargazing. It is Anthony Grafton’s special gift to show in patient detail how reasonably the system to which Cardano devoted much of his long, energetic life emerged from its basic premises. Furthermore, Grafton’s pithy writing finds its ideal object in Cardano’s eternally challenging life. Here is his account of the astrologer’s family troubles:

As an old man, Cardano played the part of the hero of a tragedy or opera—perhaps a Lear. He raged and mourned when his older son, Giambattista, a gifted doctor in his own right, was arrested, tried, convicted, and executed for murdering his wife with a focaccia laced with arsenic, and when his younger son, Aldo, turned out to be a ne’er-do-well and petty thief.

The combination of telling detail and intellectual sweep in Cardano’s Cosmos is irresistible, and it shapes Grafton’s book as Cardano once shaped his disparate empirical data into system. We do not accept the system now, but Cardano himself, as his biographer makes movingly clear, still “deserves to be heard.”

A figure no less complex and no less cantankerous than Cardano, Giordano Bruno (1548–1600) also resists modern definitions of science and nonscience, rational and irrational. In 1576, the year Cardano died, Bruno fled his Dominican convent in Naples rather than face the Inquisition for his rebel-lious behavior. His subsequent travels would take him through much of northern Europe, to Geneva, Paris, London, Wittenberg, Frankfurt, Prague, and at last to Padua and Venice, where the Inquisition finally caught up with him in 1592. Extradited from Venice to Rome in 1593, imprisoned for another six years, he was sentenced to death for “obstinate and pertinacious heresy” and burned at the stake as part of the festivities for the Jubilee Year of 1600. Four hundred years later, Bruno has continued to pose an obstinate and pertinacious problem for the present pope, whose fate it has been to preside over another Jubilee; most obviously, how shall the contemporary Catholic Church reconcile the philosopher’s ghastly death with its Jubilee message of forgiveness?


Nearly as thorny, moreover, is the question of what Bruno actually stood for. We have only an approximate idea of the exact reasons for which he was convicted of heresy, because the records of his Roman trial were looted by Napoleon, carted to Paris, and lost in transit either en route or on their return journey around 1816. Bruno’s writings, banned by edict of the Roman Inquisition as part of his sentence, have been partially lost. What remains, and it is a good deal, was composed between 1582 and 1591. It turns out to be as complicated as the man himself.

Bruno, like most of his educated contemporaries, wrote in two languages. His Latin was a soberly scholastic product of his Dominican education; he spent most of fourteen years in the very Neapolitan convent, San Domenico Maggiore, that had once housed that master of theolog-ical precision, Thomas Aquinas. Yet Bruno’s vernacular comedy, The Candlemaker of 1582, presents an obscenely, savagely picaresque vision of the brawling Neapolitan street life that still teems just outside San Domenico’s walls. His six Italian Dialogues (1584–1585), written in Elizabethan London as the result of what Bruno himself might have called a furore eroico, share something of Shakespeare’s variety of tone and linguistic invention: in their pages we can find the kin of Prospero, Falstaff, Hamlet, the Sonnets.

This itinerant sage, “academic of no academy, called ‘the Disgusted,’ joyous in gloom, gloomy in joy,”1 mustered both his dense Latin and his exuberant Italian, both poetry and prose, to proclaim ideas that exploded Cardano’s cosmos with all the force of the Big Bang. Bruno believed with Copernicus that the sun formed the center of our planetary system, but he counted the sun as only one in an infinity of solar systems whirling in an infinite universe pervaded by a single, all-embracing world soul. Neither Kepler nor Galileo, both of whom obviously read Bruno carefully, could ever quite face a cosmos of this magnitude. Neither, at the time, could the institutional Church.

Yet for all his prescience, Bruno combined his infinite vision and its companion belief in atomic theory with an utter disdain for empirical research. The dialogue in which he claims to defend the Copernican system, The Ash Wednesday Supper of 1584, gets Copernicus wrong. There are certainly strong reasons not to consider Giordano Bruno a scientist in any modern sense, although late-nineteenth-century historians usually regarded him, like Galileo, as a martyr for scientific thought, a martyr, furthermore, who had his contemporary political uses. In the wake of Italy’s unification, a statue of Bruno, endowed in part by the students of the University of Rome and in part by an international subscription, was erected in the Campo de’ Fiori, the Roman piazza where he met his death. Conceived as a standing taunt to the papacy, Ercole Ferrata’s brooding bronze Bruno of 1888 is probably one of the most successful pieces of public art ever created; it has become a kind of secular shrine within the Eternal City, the recipient of annual wreaths from the mayor and constant offerings of flowers from Bruno’s many admirers.

Now, with persuasive force, a new book by the historian of science Hilary Gatti, Giordano Bruno and Renaissance Science, presents a bold argument for Bruno’s inclusion not only within the sphere of Renaissance science but also within the sphere of science as it is practiced at the present time. As she puts it:

Was it necessary to see Bruno’s sixteenth-century science as in all respects a prelude to the classical mechanical science that would dominate European culture from the early seventeenth century up to the end of the nineteenth? Might not some aspects of his thought seem closer to an age of post-Einsteinian relativity and quantum mechanics, with their theoretical justifications of scientific approximations rather than logical certainties and indisputable truths?2

Her answer, as one might suspect, is affirmative, while recognizing that Bruno must always be seen within the context of his own era. A sixteenth-century man no less than Girolamo Cardano, Bruno likewise devoted much of his time to pursuits that are no longer associated with scientific practice, including astrology and magic. He believed as well in the authenticity and hoary antiquity of the mystical books attributed to the Egyptian sage Hermes Trismegistus, a younger contemporary of Noah whose wisdom was thought to have influenced both Moses and Plato, and whose reputation would be definitively sunk in 1614 by a French scholar who argued with scathing acuity that the books of Hermes had been written in Roman times. This aspect of Bruno’s work was the subject of a well-known book by the English scholar Frances Yates).3

Nor are Bruno’s most modern-sounding ideas ever really couched in the terms of empirical science. When he declared that the universe was made of atoms, he had no new evidence to prove his claim; he had only the precedent of the Greek phil-osopher Democritus and the Roman philosopher-poet Lucretius, and his own intuitions. When he declared that the cosmos had no center, no edges, and no end, he used no more than his eyes to plumb the starry depths and the writings of the fifteenth-century cardinal-philosopher Nicholas of Cusa to back his contentions. And yet none other than Johannes Kepler, writing to Galileo in the first flush of excitement over the revelations of the telescope, would assert in 1610 that compared with their own discoveries, Bruno’s theoretical insights were more truly the work of genius—or as Kepler said, more godlike:

For the glory of this world’s Architect greatly exceeds that of the contemplator of such glory, however ingenious. The former, after all, drew the principles of its creation from within Himself, whereas the latter, after great effort, scarcely recognizes the expression of such principles in that same creation. Certainly those who can conceive the causes of phenomena in their minds before the phenomena themselves have been revealed are more like Architects than the rest of us, who consider causes only after they have seen the phenomena. Do not, therefore, Galileo, begrudge our predecessors their proper credit…you refine a doctrine borrowed from Bruno….4

Despite Bruno’s burning devotion to what he named the “Nolan philosophy,” after his native city in the hinterland of Mount Vesuvius, his surviving work supplies no clear explanation of exactly what constituted that Nolan philosophy. In person, he had a tendency to explode with impatience at his slow-witted listeners, while as a writer he had an equally well-developed tendency to change his mind. Gatti describes the “acentric labyrinth” of Bruno’s thought with precision and skill, bringing her own command of medieval philosophy, Renaissance science, and modern physics to bear on her recalcitrant target.5 The author of a witty translation of Bruno’s Ash Wednesday Supper, Gatti also has an unusually clear sense of Bruno’s language, that “large and copious vein of long, flowing, great and solid prose” that so frequently becomes an end in itself, as when he claims to speak plainly in the preface to his dialogue “Expulsion of the Triumphant Beast”:

Here Giordano speaks the common language, he names names freely,…he calls bread bread, wine wine, a head a head, a foot a foot, and other parts by their proper name, he calls eating eating, sleeping sleeping, drinking drinking…. He holds miracles as miracles, prodigies and marvels as prodigies and marvels, truth as truth, doctrine as doctrine, goodness and virtue as goodness and virtue, impostures as impostures, deceptions as deceptions, knife and fire as knife and fire, words and dreams as words and dreams, peace as peace, love as love. He regards philosophers as philosophers, pedants as pedants, monks as monks, ministers as ministers, preachers as preachers, bloodsuckers as bloodsuckers, ne’er-do-wells, mountebanks, charlatans, triflers, barterers, actors, parrots as that which they are called, show themselves to be, are; workers, benefactors, sages and heroes as themselves.6

One name that probably no longer applied to this defrocked Dominican at the end of his life was “Christian.” Gatti faces this vexed issue with characteristic levelheadedness, pointing out where he explicitly deviates from standard Christian doctrine. Here again, Bruno himself is extraordinarily difficult to pin down, especially because most of his explicit opinions on Christian theology, both doctrinaire and defiant, come from the surviving records of his interrogations by the Venetian and Roman Inquisitions. In the course of seven years’ imprisonment, Bruno twice offered to retract his heretical pronouncements (the second time perhaps after torture) and then retracted his retractions. It is his peculiar if not entirely lapsed Christian faith that ultimately determined the way in which Pope John Paul II, through Vatican Secretary of State Angelo Cardinal Sodano, would pronounce upon Bruno’s fate just before the four hundredth anniversary of the philosopher’s immolation on February 17, 2000:

In reality, on the basis of recent researches…it seems to be agreed that…[Bruno’s] thought, developed in the context of a rather eventful existence and against the background of an unfortunately divided Christianity, led him to intellectual choices that progressively revealed themselves on some decisive points as incompatible with Christian doctrine…. It is not our place to express judgments about the conscience of those who were involved in this matter…. Objectively, nonetheless, certain aspects of these procedures and in particular their violent result at the hand of civil authority, in this and analogous cases, cannot but constitute a cause for profound regret on the part of the Church.7

As Cardinal Sodano issued this painfully careful statement, an immense and motley crowd of radicals, anarchists, Masons, freethinkers, scholars, and neighbors covered Ercole Ferrata’s statue in Rome with flowers, poems, and candles as if Giordano Bruno were a secular saint, briefly cordoning off the surrounding neighborhood to declare it a “Pope-free zone.” The event showed how insistently Bruno continues to rankle authority—and how elusive the reality of the man and his Nolan philosophy still remain. Hilary Gatti has raised provocative questions about where this strange genius fits in the history of European thought, but also about the very process of science itself, and particularly about the pattern of its development. Her book could not be more timely.

Tragically, Bruno probably returned to Italy in 1592 in order to press his candidacy for a professorship of mathematics at Padua. The position went instead to a young Tuscan named Galileo Galilei. The shock caused by Giordano Bruno’s death shortly thereafter may well have helped to preserve Galileo’s life when the cantankerous astronomer faced the Inquisition in his turn, first in 1616, when he was released, and again in 1633, when he was forced to recant on his knees and sentenced to life imprisonment, later commuted to house arrest in his villa outside Florence.

With Galileo, of course, there has never been any doubt about whether his work should be described as astrology or astronomy, magic or science; nor has there been any doubt, on the part either of the Church itself or of his secular contemporaries, that he was a devout Catholic. He quoted the Bible in support of his own positions as freely as his clerical opponents drafted the same scripture to serve their own ends, although he suggested, following the lead of Giordano Bruno, that it was better used for moral guidance than for mapping the heavens. Galileo’s great error was to provoke a pope, his fellow Tuscan and longtime friend Urban VIII, by making fun of him on the very last page of his 1632 Dialogue on the Two Chief World Systems. Urban’s reaction powered the trial of Galileo; the human toll it exacted on the defendant comes through poignantly in the letters he received from his daughter as the proceedings dragged on to their depressing end.

These letters have now been translated by the science writer Dava Sobel in her absorbing Galileo’s Daughter: A Historical Memoir of Science, Faith, and Love. Sister Maria Celeste Galilei (1600–1634) was “born in fornication” in Padua as Virginia, the first of Galileo’s three children by his mistress Marina Gamba. Aristocratic, selfish, hopeful of an eventual professorship back in Tuscany, Galileo had no intention of marrying his companion, although he freely acknowledged their children as his own; Virginia, for example, was named after Galileo’s sister. When he finally obtained a position at the University of Pisa, he left his son with Marina (who promptly married a local man of her own social standing), and brought the girls to Florence. Sobel suggests that his own poor health—kidney trouble, rheumatic disease, quartan fever, hernia, eye infections brought on by his obsessive stargazing—and his stormy professional circumstances must have prompted him to put the two sisters in a convent and pledge them to religious life when they were not yet adolescents.

Aside from his own travails, the stigma of illegitimacy blighted their prospects for marriage. In the case of Galileo’s younger daughter, the odd, depressive Livia, who took her vows as Sister Arcangela, we might say today that she was institutionalized, and she may have needed the constant care of a supervised life. But what of Virginia, who took the appropriately cosmological name of Maria Celeste, the one child of Galileo’s who seems to have shared her father’s intellectual spark? It would have cost Galileo a great deal of money to put her with an order of nuns like the Benedictines in Florence, with their emphasis on education and comfortable living; in seventeenth-century Italy, brides of Christ, like brides of mortal men, required substantial dowries. Instead, dowered with a far smaller investment, Sister Maria Celeste, a woman of rare mind and spirit, eked out a life of bare subsistence among the Franciscan nuns known as Poor Clares, not in the city itself, but in the hamlet of Arcetri on the outskirts of Florence.

As her letters to Galileo show, her impressive intellect was often occupied with the minutiae of the cloister, which she gently transformed into occasions for reflection, as in this letter from December 19, 1625:

Most Illustrious and Beloved Lord Father,

As for the citron, which you commanded me, Sire, to make into candy, I have come up with only this little bit that I send you now, because I am afraid the fruit was not fresh enough for the confection to reach the state of perfection I would have liked, and indeed it did not turn out very well after all. Along with this I am sending you two baked pears for these festive days. But to present you with an even more special gift, I enclose a rose, which, as an extraordinary thing in this cold season, must be warmly welcomed by you. And all the more since, together with the rose, you will be able to accept the thorns that represent the bitter suffering of our Lord; and also its green leaves, symbolizing the hope that we nurture (by virtue of this holy passion), of the reward that awaits us, after the brevity and darkness of the winter of the present life, when at last we will enter the clarity and happiness of the eternal spring of Heaven, which blessed God grants us by His mercy.

And ending here, I give you loving greetings, together with Suor Arcangela, and remind you, Sire, that both of us are all eagerness to hear the current state of your health.

Most affectionate daughter, S.M. Celeste

Like many nuns who took vows of extreme poverty, she did not last long. She died of dysentery, not quite thirty-four, during the first bitter winter of Galileo’s confinement to his villa, a short distance from her convent of San Matteo. It is hard not to see this Tuscan nun’s talents as callously wasted and her cloistering as a sentence to house arrest, under far more arduous conditions than Galileo’s own. Indeed, following the dictates of contemporary society, Galileo lavished money and attention on his wastrel son, and although he sustained the struggling nuns of San Matteo as best he could, his best was never quite sufficient to keep an entire community in good physical and spiritual health.

Dava Sobel tells this troubling story with haunting empathy for both Galileo and Sister Maria Celeste, judging their actions by the standards of their own times rather than ours. It is a book aimed at a general audience; some reviewers have complained that it presents “nothing new,” but a story well told is always new, and this one is delivered by a master narrator, its most devastating impact reserved for the book’s last two sentences:

Even now, no inscription on Galileo’s much-visited tomb in Santa Croce announces the presence of Suor Maria Celeste. But still she is there.

Eventually, of course, the Church came to accept the structure of the universe, and sooner than anyone was willing to admit openly. Pope Urban’s nephew, Cardinal Francesco Barberini (who along with two other cardinals out of ten had refused to sign Galileo’s sentence), kept a set of Copernican armillary spheres in his palazzo until 1633 when he felt obliged to have them removed. A letter from one of his acquaintances in 1637 urges him to put them back because they are too well made to go to waste:

In your library I saw certain [globes with] Copernican Systems where the earth is mobile, made in Holland; afterwards they told me that Your Eminence ordered them taken away, so that you would not appear to follow an erroneous and condemned opinion. But it seems to me that you could preserve them for the exquisite craftsmanship with which they were made and attach a label that alerted the spectators and said “The false and lying Copernican system with a mobile earth.”8

Jesuit astronomers like Christoph Clavius, who first invited Galileo to lecture in Rome, and Galileo’s adversary Christoph Scheiner were both Copernicans, according to yet another Jesuit astronomer, Athanasius Kircher, whose report that these reverend fathers professed orthodoxy only under pressure surely described Kircher’s own position as well (Kircher’s own armillary sphere had a pop-out center that could make it Copernican or orthodox at will):

The good father Athanasius… could not restrain himself from telling us…that Father Malaperti [Charles Malapert, another Jesuit astronomer] and Father Clavius themselves in no way disapproved the opinion of Copernicus—indeed they would have espoused it openly had they not been pressed and obliged to write according to the premises of Aristotle—and that Father Scheiner himself did not comply except under compulsion and by obedience.9

Galileo was officially exonerated by Pope John Paul II in 1992, but as J.L. Heilbron points out in The Sun in the Church: Cathedrals as Solar Observatories, the Vatican itself sanctioned the printing of Galileo’s banned Dialogue on the Two Chief World Systems in 1741 with a few minor adjustments (including forty insertions of the phrase “supposed” before “motion of the earth”). Furthermore, he reports: “In 1712 the Holy Office decided, without telling anyone, that it would not make objections to the teaching of heliocentrism as a hypothesis.”

The Church, as Heilbron reminds his readers, had a vested interest in keeping track of the heavens; an accurate calendar meant an accurate date for Easter and all the other festivals of the Christian year. To this end, the Gregorian calendar had been put in place by Pope Gregory XIII in 1582 with Christoph Clavius serving as chief adviser. Heilbron brings a great deal of biographical information about church-based astronomers to illustrate what many historians of seventeenth-century Europe are beginning to recognize, namely that the chief result of Galileo’s condemnation in the Catholic world may have been to erect an elaborate apparatus of double-speak, in Italy above all. Meanwhile, as Heilbron shows, from the mid-sixteenth century, in the immediate aftermath of Galileo’s condemnation, to the mid-eighteenth century and the full-blown Enlightenment, Catholic churches were the best solar observatories in the world.10

One of those observatories, the Torre dei Venti, or “Tower of the Winds,” sits atop the Vatican Palace itself. There the sixteenth-century Dominican astronomer Egnatio Danti (who had worked with the Jesuit Christoph Clavius to devise the Gregorian calendar) installed a meridian: a tiny hole in the tower’s floor admitted a beam of sunlight at high noon, whose progress could be tracked across the floor as the seasons made their annual round (see illustration on page 29). Churches, in fact, with their soaring vaults and spacious floors, proved the best possible settings for meridians that monitored the movements of the sun with unprecedented accuracy, and many of sunny Italy’s great cathedrals, as Heilbron shows in rich detail, were outfitted with these precision instruments between the sixteenth and eighteenth centuries. Unfortunately, neither the earth’s shifty crust nor the cosmos have stood still since then, and by now the sunbeam cast by Danti’s meridian in the Tower of the Winds conspicuously misses the elaborate inlays in the floor that were once designed to meet it.

Heilbron’s study is unabashedly mathematical, filled with diagrams and equations to bring home the principles whereby the astronomers of early modern Europe designed their indoor meridians and installed them in cathedrals, not only because these were the largest enclosed spaces available, but also because, as the Psalmist declared: “The heavens declare the glory of God, and the firmament sheweth His handywork.”

The Sun in the Church is also filled with information about such figures as Julius Caesar (as promoter of the Julian calendar) and such works as the 1989 Italian novel by Vanni Ronsisvalle, Gli astronomi (The Astronomers), which describes intrigues among astronomers who worked in a Sicilian observatory in the late nineteenth century. The innumerate reader will learn much from Heilbron’s book, and may come away with a different appreciation of the stars above us.

From his prison cell in Venice, Giordano Bruno could still see those stars, for Inquisition records report that he would call his cellmates to the window and began to speak about what he saw:

In his conversations, [Bruno] asserted that there were many worlds, and that the world was a star, and that this world appeared as a star to the other worlds, just as the other worlds shine down on us as stars.

Looking from his confinement onto what he called “those lights and writings sculpted in the firmament,” he may have read the face of the heavens better than anyone alive.

This Issue

February 22, 2001