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Chapter 1
Patience
Aix-en-Provence, 1635
It is four in the morning and the moon is full. Along with a steady rain, a yellowish light falls on a handful of bustling men standing on the rooftop of an aristocrat’s house, measuring and recording. A local priest and a bookbinder are among them, taking turns looking up at the night sky through a long brass telescope, while another group is frantically working the lever of an enormous quadrant, gauging the altitude of various stars. In one corner, a paragon of calm, sits an artist with his sketchbook and charcoal, drawing the moon as a shadow begins to smudge it. The eclipse is finally starting.
The conductor of all this activity is late, but he’s slowly making his way up a stepladder, groaning. His stomach is burning, as it always seems to be, and his eyesight is so poor he can see only a few feet in front of him. Yet he refuses help. This is Nicolas-Claude Fabri de Peiresc, master of this house, natural philosopher, and, most important, a connector of Europe’s greatest minds. In this instant, he is also a sickly old man who has been waiting for the past two decades for this very moment.
He can’t really enjoy it, though. Peiresc is not someone to relish a realized dream. He is all self-discipline, even down to his food and clothes. He never wears silk. If he drinks wine, it is white and heavily watered down. The only food he allows himself in excess are melons, and even these he argues have health benefits. He is filled with doubt about this ambitious experiment. It involves dozens of amateur participants, hundreds of miles apart, simultaneously observing a celestial phenomenon and accurately recording what they see. He has enlisted each one himself, corresponding with them over months, moving them past their apprehensions and insecurities, convincing them of the importance of their larger purpose: to collect data that, when gathered, will offer a correct measure of longitude. If it works, they’ll be redrawing the map of the known world.
But failure seems likely, even to him. The proof comes through his spyglass. Peiresc had instructed three local men to climb a nearby hill outside Aix-en-Provence to log the night’s events. They were to signal their arrival by lighting a fire. As the eclipse progresses, he looks over and sees not even the slightest flicker in the distance.
His mind goes to all the other observers. There is Father Michelange de Nantes on a rocky summit in Syria; a diplomat, François Galaup de Chasteuil, in Lebanon; another missionary, Agathange de Vendôme, in Egypt; Thomas d’Arcos, a former captive of Barbary pirates turned Muslim convert, in Tunis; and on the Continent, an array of scholarly friends in Italy, France, Germany, and the Netherlands. A Jesuit priest in Quebec is even taking part. What if they too fail to show up?
Later that morning in his overstuffed study, layered in crimson rugs and somber oil paintings, Peiresc turns to the activity that sustains him, even in dark moments: he writes a letter. As often in his solitary life, quill, ink, paper, and some quiet allow him to reenter an ongoing exchange with his dozens of friends, many of whom he has never met and will never meet in person. He enumerates his reasons for anxiety to Pierre Gassendi, the scholar-priest who is one of his main collaborators. The night was too cloudy. His team was not ready. Because of their “haste,” his group on the roof had even “looked at the wrong side of the quadrant to take the numbers.” And as for the men on the hill, he has since learned what happened: “The rain came, and frightened by thunder and lightning, they retreated to a hermitage without having the courage or inclination to return to indicate at least the setting of the moon.” The venting continues, he dips his quill and scratches the words onto yellowed paper. “All the preparation was in vain.”
The printing press, not even two hundred years old then, is seen today as the revolutionary medium of Peiresc’s era. The ability to reproduce pamphlets and books made it possible for a dissident priest like Martin Luther to broadcast his opinions and quickly gain a following, each printed text a whisper into the ear of a potential convert. But the post offered a quieter revolution. For hundreds of years, letters were an advanced technology. They were the first instance of thought traveling distance, disassociated bodily from thinker. But from Cicero until the early modern period, they moved from one place to another so slowly and so erratically that they often read more like alternating speeches than the volley of a conversation. This changed in Peiresc’s time once the post became fast and relatively reliable. The possibility of regular correspondence now allowed for collaboration, for theories to be shared and disputed. For the slow accretion of knowledge that comes from the friction of two people trading ideas and observations.
For Peiresc, letters were units of intellectual exchange. Sitting in his study like a contented spider in the middle of an expansive web, he wrote and dictated about ten a day. They were also his only legacy, which is part of the reason his name is lost to us. He published no books, but when he died, two years after the eclipse, he left behind 100,000 pieces of paper in the form of dispatches, memoranda, and reading notes, which represented his life’s work.
These were thoughts in process. Letters were good for teasing out concepts, which made them especially valuable to a man who spent his life testing established dogma. The seventeenth century was not a time to do that in one giant leap—not unless you wanted to end up like Giordano Bruno. Only three decades before, the Italian Dominican friar had been stripped, tied to a stake, and burned alive on the Campo de’ Fiori in Rome for suggesting that our planet might not occupy the center of the universe. Others could take these risks, blast trumpets if they wanted. That wasn’t Peiresc’s approach. His ego wasn’t immune to the desire to have a book to his name, and he had plans for many. But mostly out of caution, and also because he was so restless, letters became his mastered form.
This eclipse experiment, though elegant in his own mind, stretched the power of letters to its limit. He was attempting a group observation among scattered correspondents who had never so much as bothered to wonder about the moon before, or even what longitude meant. Peiresc had spent hundreds of hours writing to them—countless pages of instructions, sent along with diagrams and crude measuring instruments. He believed that the mechanics of the natural world would be grasped cumulatively, over generations, a process of verification and correction and further verification. “The brevity of human life does not allow that one person alone is sufficient; it is necessary to adopt the observations of a good number of others from the past centuries and future ones to clarify that which fits better,” he once wrote. But still, when it came to the most far-flung of his collaborators, geographically and intellectually, it was an agonizing task just coaxing them to practice proper notation, let alone to trust the authority of their own eyes.
The eclipse itself was not the point. It was only a marker of time—a giant clock in the sky, visible from everywhere. But Peiresc hoped this clock would help him complete at last one of his many, many lifelong projects, a partial list of which included an investigation of ancient weights and measures, a study of the Roman calendar of 354 (whose oldest surviving copy he had in his study), a catalog of gemstones that he and the Flemish painter Peter Paul Rubens had been compiling together, the publication of all the Samaritan versions of the Pentateuch in Hebrew, Aramaic, and Arabic, and an exhaustive history of Provence. But it was the longitude project that was perhaps his most idiosyncratic endeavor. For one thing, it was ambitious; there was no way he could do it alone. But also, his obsession with longitude had a particularly practical purpose: to calculate the length and width of the Mediterranean Sea.
He loved that body of water and anything to do with the people and cultures that encircled it. No detail was uninteresting to him. On the rare occasions when he left Aix, it was to visit the port of Marseille. There he would take in the salt air and all the humanity marching down the wooden docks. He was as curious about the customs of the Muslims, Samaritans, and Eastern Christians as he was about the ancient Greeks. He once heard the singing of galley slaves on a docked ship, and he found a musician to help him transcribe the tune into musical notation so he could capture the song of the “black Moor.” But for Peiresc and everyone else, the sea’s exact dimensions had remained elusive. For generations, sailors had been poorly navigating from the Strait of Gibraltar around the Cyclades and to the coast of the Ottoman Empire with little more than an inherited familiarity with the coastline, an astrolabe, and fifteen-hundred-year-old drawings.
For accuracy, longitude was needed, but calculating it had evaded astronomers and cartographers for so long that in 1598 Philip III of Spain even offered a perpetual pension to anyone who could figure it out. The problem was logistical. Though latitude could be gauged by measuring the height of the noonday sun, longitude required simultaneous observation—people in at least two different locations watching some fixed phenomenon in the sky and marking precisely when they had each seen it.
