Four views of Venus; mezzotint from Francesco Bianchini’s Hesperi et Phosphori nova phaenomena sive observationes circa planetam Veneris

Linda Hall Library of Science, Engineering, and Technology, Kansas City, Missouri

Four views of Venus; mezzotint from Francesco Bianchini’s Hesperi et Phosphori nova phaenomena sive observationes circa planetam Veneris, 1728

No one in Rome would let Francesco Bianchini punch a hole through their ceiling. Bianchini wanted to measure the size of the solar system, which required the use of a sixteen-foot-long telescope—hence the hole. When he finally found a suitable place to mount his instrument and take measurements, tracking Venus and Saturn across the night sky on November 19, 1727, he used a trigonometric method to calculate the distance between the sun and Venus, the first step to measuring the whole solar system. He calculated a distance of about 53 million miles. He was short by some 14 million.

In 1726 Bianchini had rigged up an even more powerful seventy-eight-foot-long telescope, which magnified objects by a factor of 112. He must have borrowed a church garden for the night, or the gardens of the Palazzo Barberini, or a friend’s villa, where he could find the structural supports—a bridge, a high wall—required to prop up such a long tube. Through it he saw, for the first time, the face of Venus, “Mirror of Divine Beauty, the brightest of all bodies, the brilliant star of the morning.” Visitors flocked to peer into the telescope delicately cantilevered into Rome’s evening air. Since no one could replicate Bianchini’s prodigious instrument, skeptics emerged. In January 1728 Bianchini collected signed testimony from two priests, one professor, and three laymen who had pressed their eyes to the lens that night and seen the face of Venus. “Vidi et testo,” they wrote—“Seen and sworn.”

But what had they seen? Bianchini thought he had seen spots on the planet’s face. He mapped them; named Venus’s features after his generous patron, the Portuguese king João V, and after Portuguese colonizers; engraved them; and finally published his findings in a book titled Hesperi et Phosphori nova phaenomena sive observationes circa planetam Veneris (New Phenomena of Hesperus and Phosphorous, or Rather Observations Concerning the Planet Venus). Bianchini was surely his century’s version of Galileo, who had first mapped the terrain of the moon more than a hundred years before. But Venus, we now know, is covered in extremely dense sulfurous clouds, which reflect sunlight. The planet’s surface was invisible, in fact, to Bianchini’s telescope; the first visible-light images of Venus’s surface were captured by NASA’s Parker Solar Probe in February of this year.

So what did Bianchini see? A smudge on his lens? Was his telescope too long, subject to visual error or distortion? Was Venus’s cloudy atmosphere unusually calm that day, making all that gas appear as solid as Galileo’s moon rock? Was it a problem of representation: was Bianchini’s process of engraving too sure—the contrast of black ink on white paper too stark, the burin too sharp—to render in print something as ineffable as a swirling pattern of planetary clouds? Or did Bianchini see what he had desperately wanted to see—what had never before been perceived by human eyes, what could be mapped and named, a fitting culmination to a life lived in the pursuit of science?

In depicting Venus’s orbit, Bianchini had to make a choice. Either Venus circled the earth, in accordance with the system still defended by the Church and in agreement with Scripture, or it orbited the sun, as Copernicus and Galileo had it, and as Bianchini himself would have surely known to be correct. On a plate in the tragically wrong Nova phaenomena, Bianchini depicted a beautiful armillary sphere showing Venus’s orbit. The image avoided that most perilous question of early modern religion and science with tactful silence: there was nothing at the center. The planet circles empty space.

“The heavens declare the glory of God, and the firmament sheweth his handiwork,” the Psalms proclaim. For Bianchini, a deeply religious man, an aide to three consecutive popes, and a student of Galilean experimental science, astronomy was the science of describing God’s handiwork—of calculating dimensions, capturing the universe’s harmony, discovering and illuminating the arrangement of God’s firmament—not speculating about its causes or making any claims about “the unreachable truths of natural and human history,” as J.L. Heilbron writes in The Incomparable Monsignor, his fascinating biography of Bianchini. Those truths were for God alone. No matter how long the telescope, men would always view them through a glass, darkly.

Rome was Bianchini’s laboratory. He used his friends’ gardens and villas as scaffolding for his astronomical instruments, the city’s ruins as critical evidence to be sketched and included in his histories of ancient civilizations, its libraries and collections of antiquities as repositories to be plundered for authoritative information. Rome’s residents were his patrons, employers, colleagues, and co-conspirators in the Republic of Letters. Even Bianchini’s rooms at the Quirinal, the papal palace, were part of his grand experiment, stocked with books, telescopes pointed out its windows, and a sundial in the garden. He was provided with servants to launder his clothes, cook his meals, and clean his flat. As Heilbron writes, Bianchini and his celibate scholar peers “lived in a perpetual seminar” free from the obligations of domesticity, a life passed dashing between the academies and music chambers of early Enlightenment Rome.


Bianchini was especially well disposed to the pure life of the mind. He had been training for it since childhood. Born in Verona in 1662, he was favored early by the patronage of a family friend, Cardinal Pietro Ottoboni, who reigned as Pope Alexander VIII from late 1689 until his death in early 1691. At eleven Bianchini was sent to a Jesuit college in Bologna, where he became fluent in Latin and adept in Greek, and also learned grammar, rhetoric, logic, philosophy, and mathematics. Enrolling at the University of Padua to study theology, he was taught the Galilean fisicomatematica by Geminiano Montanari; in Montanari’s lectures, Bianchini learned about trigonometry, military architecture, experimental physics, the laws of motion, atomic theory, and how to praise Galileo without offending the Church’s inquisitors.

Montanari proceeded from the evidence of his eyes and his hands. He feared that theoretical science was inevitably prone to error, that “we all mislead ourselves when we want to discuss things that take place far from us, applying to them the same concepts we use for terrestrial things that we have in our hands.” Here is his fictional dialogue with his hero Galileo, on the nature of the infinite:

Galileo: Tell me, Prof. Montanari, whether you understand the infinite.

Answer: I understand only that I do not have the intellect to understand it.

Galileo: Excellent…You have learned everything that can be learned about infinity.

Bianchini, whose curiosity was matched only by his piety, was naturally sympathetic, in Heilbron’s account, to Montanari’s modest claims about the limits of experimental science. His notes on his teacher’s lectures say that most of what we want to know about nature is beyond our understanding.

At Padua in 1683, Bianchini made his first scientific discovery. Studying the night sky with Montanari, he compared what he observed with what was, at that time, the most complete atlas of the stars yet published, Johannes Bayer’s Uranometria (1603). He realized that, contrary to the writings of the ancients, the stars were not fixed in the sky but instead had a “genius for instability”: stars might vary in luminosity or even nearly vanish from the heavens altogether. As Heilbron writes, Bianchini overstated the scale of his findings (only two of the many unstable stars he identified were actually variable); what he really discovered was his own keen eye, the thrill of experimental science under the stars.

The following year Bianchini went to Rome. In 1688 he took up a post as Ottoboni’s librarian, overseeing a vast collection of manuscripts and printed books; these materials became sources for his Istoria universale, a history of the world from Creation to his own day. After Ottoboni’s death, Bianchini was supported by the late pope’s great-nephew, also named Pietro Ottoboni and also a cardinal. In 1699 Bianchini became a canon at Ottoboni’s church, San Lorenzo; in 1701 he was appointed cameriere d’onore, a top aide to Pope Clement XI, and moved into his rooms in the Quirinal. He took on new responsibilities, too, managing Rome’s water supply through ancient aqueducts, calculating the date of Easter, and overseeing ancient Latin inscriptions and monuments that were dug up across the city.

Though Bianchini was happiest peering through a telescope or concocting complicated numerological jokes for his friends’ amusement, he liked a bit of intrigue, too, and that was in no short supply at the Vatican. Rome was a partisan of the Catholic Stuart claim on the English throne. Bianchini acted as a papal diplomat, smoothing over the awkward conversations that followed the Old Pretender, James III, around Europe as he tried to gather the support of the Catholic powers for his doomed cause. The younger Pietro Ottoboni described Bianchini as possessing “the prudence of the serpent and the simplicity of the dove”; the same prudence and simplicity also came in handy for scholarly diplomacy. Bianchini counted among his friends Baron Philipp von Stosch, an apparently inspired antiquarian, spy, atheist, and pornographer. Bianchini saw what he wanted to see and closed his eyes to the rest.

Bianchini’s career as an astronomer, historian, and archaeologist culminated in the 1720s. He wrote on Rome’s ancient palaces, edited an authoritative ninth-century history of the early papacy, and saw those spots on the face of Venus. The Nova phaenomena was published in 1728. Bianchini died a year later, wearing his beloved hair shirt. He had been an aide to three popes and confidant to one Polish princess and an exiled king. Leibniz and Newton—who could never agree on much of anything—found common ground in their praise of him. Bianchini was, in Newton’s words, “a candid seeker of truth.”


What were the truths Bianchini sought? One was the precise date of Creation. By the early eighteenth century, scholars had calculated two hundred competing dates, based on scriptural evidence, scrutiny of ancient texts, astronomical data, and evidence from physical artifacts. How to account for the fact that the people of China and the Americas did not descend from Noah, or for the long and illustrious histories of Egyptian, Babylonian, and Chinese civilizations? Fixing the date of Creation would also fix the relationship between ancient civilizations and Judeo-Christian Scripture. Bianchini sought to provide a timeline and at the same time a theory of our deepest human past.

He approached the problem in Istoria universale, a chronological and comparative history of cultures and civilizations. His historical research was predicated on certain assumptions: that material evidence was critical in the pursuit of ancient chronology; that the Flood, a world-historical event, had obliterated prehistory and transformed it into mythology, and therefore that mythology could be used as historical evidence; and that all civilizations made equal progress in equal time, which gave him a firm foundation for the tricky work of periodization. Matching his prodigious research with his skill as an artist, Bianchini drew over 140 objects and arranged them into collages that symbolized each epoch. He issued some separately as an educational card game.

Bianchini found evidence for Creation wherever he looked, agreeing with Montanari that people across the world believed in it long “before the errors of those who called themselves philosophers threw it into doubt.” In his collage depicting the evidence of Creation, he included a drawing from an ancient Roman lamp showing Neptune separating the oceans, Egyptian hieroglyphs supposedly commemorating creation and renewal, and an image of a stag sacrificed every spring by the indigenous people of Florida. He urged fellow scholars to head to the foot of the nearest volcano and measure the dampness of the soil there, to fix once and for all the date of the Flood.

Design for a long telescope; drawing by Bianchini from Nova phaenomena

Governing Body of Christ church, Oxford University

Design for a long telescope; drawing by Bianchini from Nova phaenomena

Bianchini’s history showed the contemporaneous invention of agriculture, astronomy, and navigation across classical sources, Chinese records collected by Jesuit missionaries, and indigenous mythologies of the Americas. He copied out drawings of the constellations from a Chinese planisphere and the observatory of the eleventh-century BC ruler Chou Kung. With its principles of equal progress in equal time, symmetrical divisions of historical epochs, and emphasis on parallel and universal human development, Bianchini’s book was a testament to a deeply religious apprehension of the world that found evidence of God’s ordered and harmonious Creation across sources, cultures, and epochs, from Pompeii’s damp feet to the stars. The composite images of Bianchini’s Istoria inspired Giovanni Battista Piranesi’s archaeological fantasies of Roman ruins; its comparative historical method was an important predecessor of the one used by the philosopher Giambattista Vico in The New Science.

Chronology was a sacred art, and the pope entrusted it to Bianchini. The date of Easter is calculated as the first Sunday after the first full moon after the spring equinox; astronomical observation was therefore required to precisely identify it. For the jubilee year of 1700, Pope Clement XI commissioned Bianchini to construct a meridian line in the Roman church of Santa Maria degli Angeli. The meridiana transformed the church itself into a monumental scientific instrument. Bianchini put a hole through the roof and inlaid a 145-foot-long metal line into the church floor. The hole projected onto the floor a disk of sunlight, which swept across the meridian line at solar noon each day. As the sun moved across the sky between the summer and winter solstices, the disk tracked along the metal line. (The original iron was eventually replaced with brass.) The sun’s position on the line indicated with great precision the date of the two equinoxes.

Santa Maria degli Angeli was the perfect space to transform into a living instrument, with its vast expanse of smooth marble floor, high ceilings, and relatively few obstructions. (One architrave had to be removed.) And the meridiana was as much a work of art as a work of science, fitting for a church built by Michelangelo over the ruined Baths of Diocletian. Bianchini commissioned the painter Carlo Maratti to design zodiac symbols in marble and brass for the floor, patterned after the images of the Uranometria. He embedded medallions that commemorated important events of his time along the line, reflecting the sun’s position on those significant days.

Bianchini returned to his meridiana every other day for twenty-five years to record the information it revealed about the position of the sun. Visitors witnessed him “kneeling on the ground” in his clerical robes, “writing, calculating,” as the sun streamed down in a dust-flecked shaft; he took his last notes only eleven days before his death. His notebook records the visits of those who came to observe the great instrument and its designer at work, including Queen Maria Casimira Sobieski of Poland, who took pleasure in watching the sun glint off a medallion Bianchini had installed as a memorial to her late husband.

As Heilbron’s earlier book The Sun in the Church: Cathedrals as Solar Observatories (1999) explains, the meridiana exemplifies the religious zeal for scientific knowledge, the pursuit of ever more precise astrological instruments by the same cardinals and popes who could not countenance a Copernican revolution in their understanding of the stars. Bianchini explained: “In this single instrument not only astronomy but also sacred chronology and the Roman Catholic calendar may be seen independently and united by the rays of the celestial bodies.” The hole that he punched in the roof of Santa Maria degli Angeli provided testimony to the harmony of God’s created universe, beamed down onto the floor right beneath his feet.

In 1725, while measuring a ruined wall that had once been part of Domitian’s palace on the Palatine Hill, Bianchini fell through a hole. As he clung to the edge, his servants tossed him a measuring tape and winched him down slowly. Bianchini was on the hill as the head of the papal office that oversaw Rome’s antiquities, excavations, and ancient inscriptions, and was trying to piece back together the great palatial complex that stood ruined before him. As he had done when writing his Istoria universale, Bianchini proceeded from a few foundational assumptions: first, that good taste is eternal—the best design principles of contemporary Rome would have surely applied in the first century, too—and second, that perfect design is symmetrical. From these axioms Bianchini recreated the whole of Domitian’s palace, from its ornate entrance to its plumbing, published as the Palazzo de’ cesari. His was a creative history that, if not entirely accurate, brought the palace to life, humming with hidden servants and preening diplomats, with water flowing into the taps and sunlight streaming through the windows.

That same year, after some bandits dug up an ancient tomb complex on the Appian Way, Bianchini undertook a study of its urns and their inscriptions. The tomb contained the remains of more than three thousand slaves and free servants of Livia, the emperor Augustus’s widow. Bianchini studied and published over two hundred inscriptions that listed their names and employment: here lay cleaners, laundresses, custodians of the summer wardrobe and those of the winter one, doctors, midwives, women who oiled Livia and those who massaged her or drew her baths. Augustus employed a man to read to him when he was suffering from sleeplessness, one to remind him of his friends’ names when he was suffering from forgetfulness, and one (called a silentarius) just to shut people up when they were bothering him. All that dusty work with antiquities might suggest a man more at home in the silent company of things than of people, but Bianchini’s historical imagination was a sociable one: if his Istoria universale was a form of early cultural history, his reconstructions of ancient Rome were experiments in social history, imagining the lives of slaves and empresses.

Bianchini is a delight to spend time with, and Heilbron—the author of an authoritative biography of Galileo, as well as lives of the physicists Ernest Rutherford, Max Planck, and H.G.J. Moseley—is an erudite and witty guide to the monsignor’s world and his work. Through these two scholars, the doors to the most recondite Enlightenment circles are pried open: lens makers’ workshops, academy salons, the studies of collectors and popes. While Heilbron’s explanations of the trigonometric method for determining planetary parallax strained the abilities of this high school physics dropout, he nevertheless vividly describes just how exciting such work was in its time, approaching his ingenious subjects with an inviting blend of reverence and humor.

One of the great gifts of the book is the cast of minor characters who brightly orbit Bianchini. There is the winningly modest Montanari; Newton is here, valiantly attempting to identify when Jason and the Argonauts set sail. Lesser-known scientists appear, too. My favorite is Maria Clara Einmart, the daughter of an etcher and astronomer in Nuremberg, who looked through her father’s telescope and painted what she saw: moonscapes, comets, and aspects of Mars, Jupiter, and Saturn. She died in childbirth at thirty-one, but her scholarship lives on, incorporated into Donato Creti’s gorgeous nocturnal landscape paintings now hanging in the Vatican galleries.

Other scientists in Heilbron’s pages hawk wild schemes to put monumental globes in every city square or acoustic tubes in scholars’ flats so they can eavesdrop on neighbors, or designs for carriages that might drift up to the moon on inflatable spheres. A flock of Jesuits advise Bianchini not to sail to England in a boat full of Calvinists, lest he drown in the company of heretics. Charles (“I own I am a little mad”) Wogan, an Irish Jacobite and boy poet, engineered a dashing escape for a teenage princess, Maria Clementina Sobieski, so that she might marry the Old Pretender. With the princess imprisoned at Innsbruck through the machinations of King George I, who worried about her sizable dowry falling into the hands of the pretender king, Wogan convinced her servants to bundle her out of the castle under cover of darkness, dressed humbly with an apron full of jewels. Bianchini was ready in Rome to receive her with baskets of sweets.

For the scholars discussed in Heilbron’s book, knowing was not a matter of searching for the causes of things. They looked and looked well, whether through a telescope lens or into a cavernous ancient sepulcher; they measured and described what they saw in diagrams, in Latin and Italian, in etchings and in paintings. But they did not guess at what set it all in motion. As Newton wrote, “I feign no hypotheses.” His methods, Bianchini averred, “can be repeated at will by whoever loves to revere and contemplate the workings of Divine Wisdom in the disposition, immensity, and motions of the heavenly bodies.” This was a principle of reproducibility sustained not by the scientific method but by faith, a unifying way of seeing that valued the principles of harmony, symmetry, and immutability above all else. As Heilbron writes, there was no doubt in Bianchini’s mind how time began and how it would end. All that was left was to describe the middle.

An earlier version of this article misstated the distance between Venus and the sun.