Gilbert was jubilantly aware of how much at odds his new theory was with that of the ancient Greeks. He called it “our doctrine magnetical” and crowed that it was “at variance with most of their principles and dogmas.” Gilbert’s main aim in spending his time and fortune on magnetic experiments was to topple Aristotelian natural philosophy, replacing it with one he himself had devised. Gilbert’s magnetic doctrine lay at the heart of the even broader philosophy he was working on when he died of the plague in 1603. That work, De Mundo (About the World), was not published until 1651 and has not been translated into English. De Magnete reads like a technical appendix to De Mundo, according to one scholar who has plowed through the later work.
Implicit in Gilbert’s findings was an endorsement of the heliocentric work of the Polish astronomer Nicolaus Copernicus from several decades earlier. Copernicus wrote that the Earth spins on its axis and that the Earth also spins around a fixed sun. Gilbert concluded (wrongly, as it turns out) that the Earth spins because of its magnetic force. While Gilbert didn’t expressly endorse the heliocentric philosophy, it was embedded in his work. He was a closet Copernican.
These were dangerous ideas. They ran against a seminal teaching of the Bible and, therefore, against the word of God himself. It is difficult today to comprehend how uncritically citizens, not to mention church fathers, of that time viewed the tales in the Bible. They took each story as infallible information. Several decades before Gilbert published De Magnete, for example, the Flemish anatomist Andreas Vesalius had published his groundbreaking work De Humani Corporis Fabrica (On the Fabric of the Human Body). Based on Vesalius’s many dissections of human corpses, some directly from the gallows, he declared, among many other findings, that the male and female bodies had the same number of ribs. It was a scandal. It ran against the story of creation in the Book of Genesis, in which God took one of Adam’s ribs to form Eve. To prove his point, Vesalius mounted resoundingly controversial public lectures throughout Italy to show the crowds what he had found.
Heliocentrism was just as monstrous. According to contemporary interpretations of the Bible, the Earth was the core of God’s creation. That meant everything else had to revolve around it. To claim anything else was to claim that the Bible was wrong. Heresy. A few years before De Magnete was published, the Italian Dominican friar and philosopher Giordano Bruno tried to enhance Copernicus’s ideas by arguing that each star was a sun with its own roster of planets surrounding it. He was brought before the Inquisition, a court set up to defend the Roman Catholic Church from heretical thought. The Inquisition condemned him and, the same year Gilbert’s book came out, Bruno was burned at the stake in Rome.
It didn’t matter to the keepers of Christian doctrine that new observations of the stars and planets were showing a different truth from the one they thought the Bible told. Theology and science were indistinguishable from each other. Within a decade of the publication of Gilbert’s De Magnete, the Florentine astronomer Galileo Galilei was peering into the heavens with his homemade telescope, finding four new moons circling around Jupiter and exploring our galaxy, the Milky Way. In the years following, his telescopic investigations of the skies convinced him that the Earth and other planets revolve around the sun—just as Copernicus had argued in 1543—and Galileo published this idea in 1632 in the form of a dialogue.
The Inquisition took note, as it had with Bruno. Galileo found himself summoned to Rome to face questioning. The fact that Galileo had read and approved of Gilbert’s De Magnete became one of the four proofs of guilt presented against him. (Copies of Gilbert’s book from that era have been found with the Copernican bits chopped out, likely as directed by Inquisitional censors.) Galileo was condemned in 1633, forced to confess his sad errors and then endure the banning of his book. He returned to Florence to live out his remaining few years under strict house arrest.
Gilbert didn’t face those same risks. The fact that he didn’t overtly embrace Copernican ideas was likely because he was a conservative society doctor rather than evidence of his fears of official prosecution. This was, after all, England, where the Reformist Queen Elizabeth I was head of a Protestant Church. She was not as apt to be concerned about revolutionary ideas as the twitchy Catholics, who were in the process of trying to staunch the flow of defectors to the apostate faith. But at that time, holding an unfashionable view, while not necessarily criminal, could torpedo a lucrative medical career. Gilbert’s colleague William Harvey unhappily discovered as much in 1628, when he published his revolutionary finding that the heart pumps blood around the body. Harvey’s well-heeled clientele evaporated, despite his status as royal physician.
Gilbert escaped that fate. But he didn’t have an easy time of it. He had predicted the fallout in his typically pointed tone:
Why should I, I say, add aught further to this so-perturbed republick of letters, and expose this noble philosophy, which seems new and incredible by reason of so many things hitherto unrevealed, to be damned and torn to pieces by the maledictions of those who are either already sworn to the opinions of other men, or are foolish corruptors of good arts, learned idiots, grammatists, sophists, wranglers, and perverse little folk?
The Jesuits led the attack. Gilbert’s offense was imagining the primacy of the sun over the Earth. That, they vigorously disputed. The contention that the Earth is a giant magnet was not nearly as controversial. In fact, the Jesuits embraced the idea, even pressing it into service to refute heliocentrism. They said the Earth’s own magnetism held it at the heart of the Maker’s creation.
For a time, Gilbert’s work figured in the burning longitude question. He had decided that declination, or the angle of difference between the geographic North Pole and the magnetic pole, could never change because the continents, which pulled the compass away from the pole, were immutable. Therefore, if you measured declination once, it would always be the same, no matter how often you went back to the same place to measure it. His finding helped propel the drive to measure declination all over the globe, once and for all.
But it was only a matter of decades before that part of his magnetic theory was proven incorrect. In fact, the magnetic force that Gilbert had correctly deduced lay inside the Earth’s core was not immutable. Rather, it was, and is, protean.
CHAPTER 7
voyage into the underworld
The electric train to the top of the Puy de Dôme, the sleeping giant of a volcano that overlooks Clermont-Ferrand, was packed with high school students from Brittany. Kornprobst looked around at them, the flower of French youth on a field trip to the mountain observatory that both he and Brunhes had once ruled over. He would be amazed if any of them had a clue who Brunhes was, he confided to me.
We were nearing the end of our first long day retracing Brunhes’s historic steps. We had already made a dispiriting detour to Laschamp, a dot on the map a few kilometers from Clermont-Ferrand. This was where, after sampling more than fifty volcanoes in the area in the 1960s, the PhD student Norbert Bonhommet discovered the Laschamp excursion, or near-reversal, from about 40,000 years ago, the last time the Earth’s magnetic field was in disarray. For a while, it was thought to be evidence of the last full reversal. Kornprobst’s colleague Jean-Pierre Valet has linked the timing of the excursion to the demise of the last Neanderthal. Kornprobst and I had trudged through the snow with a compass, trying to find the spot where Bonhommet had taken his sample. No luck. We finally gave up and went for lunch: a rich local specialty called truffade, made of sliced potatoes and lots of butter and even more melted cheese, served with red wine.
Now Kornprobst was keen to play host at the scientific laboratory up on top of the Dôme. Brunhes had spent vast amounts of time there, arduously riding up the switchbacking old Roman road to its summit by mule, fascinated with the ruins of a monumental, multi-tiered temple to the travelers’ god Mercury built here in the second century CE. It was one of the largest religious sanctuaries of the Roman Empire, visible
from the road the Romans built far below.
The temple had been forgotten for centuries, rediscovered in 1872 when workers began excavating the volcano top for construction materials to build the observatory. To Brunhes, who arrived nearly thirty years after that, the discovery represented a potential wealth of information on the magnetism of the large rectangular slabs of pale Dôme lava used to make the temple. His assistant, Pierre David, tested four, finding mainly that they had held their magnetic memory—an important confirmation of their laboratory technique. The two colleagues vowed to do more tests.
But whenever you go up to a volcano’s peak you also go down into its terrifying inner reaches, whether you are there for science or worship or art. Nearly half a million visitors a year flock to the top of the Dôme, at least partly because standing on the lip of a volcano, however long dormant, is like standing at the maw of hell. You’re not sure what terrors could be right below, waiting to pounce. It is catching a glimpse of the unknowable forces deep within the Earth that hold the power to erase the world.
The Romans likely knew that it was an old volcano. That’s probably why they built their sprawling temple to Mercury there, so far above the road. Even today, with the train, you have to want to get there in order to make the trek. To hike back down would take a vigorous hour and a half. But the knowledge that this was once a volcano got lost after the Roman era, along with the memory of the temple. For more than a thousand years, this volcano was thought to be a worn-down mountain like the others in this area. The menace was a faint memory.
Then, in 1751, the French naturalist Jean-Étienne Guettard climbed to the top of the Dôme and saw immediately that it was one of about ninety volcanoes that run across 30 kilometers (nearly 20 miles) of the Auvergne region of central France. He warned that they might wake from slumber and explode again. Modern volcanologists concur. It caused a sensation to find a string of old volcanoes hidden in plain sight in a part of Europe that had been settled for thousands of years. The subsequent intense interest in the volcanoes, known as the Chaîne des Puys, marked the birth of the formal study of volcanoes. Volcanologists made pilgrimages from all over Europe, trying to understand what made the volcanoes spew their lava and when it had last happened, trying to peer down into the bowels of the Earth and back into time.
Like so many elements of geophysics, volcanology represented a challenge to theology. The age of the Earth was of critical, abiding interest to theologians, partly because they believed that if they knew when the world began, they would also know when it would end. Apart from that, to their way of thinking, God had created the world, and his chronicle of that creation was contained within the Bible itself.
This philosophy reached its logical conclusion in the seventeenth century, when James Ussher, the archbishop of Armagh in Ireland, painstakingly went through the Old Testament books to reckon precisely how long before the birth of Christ major events had taken place. He famously put the birth of the planet at early Saturday evening, October 22, 4004 BCE, needing two thousand pages of Latin to explain how he came to that date. Other scholars calculated it to roughly the same period, meaning that they thought the Earth was not quite 6,000 years old. (Modern scientific calculations put it at about 4.6 billion years old.) By the beginning of the eighteenth century, annotated versions of the King James Bible included Ussher’s dates in the margins beside the relevant passages, supporting the idea that the Bible was a reliable chronology. The supposed birth date of the Earth wasn’t academically debunked until the late nineteenth century, and was still debated into the late twentieth century, long after the field of volcanology had begun, after paleontologists had begun digging up ancient human fossils, and after the British naturalist Charles Darwin published On the Origin of Species, outlining the theory that creatures had evolved over time from common ancestors.
On top of that, naturalists of the eighteenth century had dueling theories about what made the material the volcanoes spat out. They were divided between water and fire. The Neptunists, named after the Roman god of the sea, were convinced that basalt, or swiftly cooled lava, was formed at the bottom of the sea as sediment. Volcanoes were formed by underground explosions, perhaps of tar or brimstone. Their rivals, named Plutonists after the Roman god of the fiery underworld, thought lava was molten rock that built up underneath the Earth’s surface and finally let loose. Both Neptunists and Plutonists visited the Auvergne to see the Dôme and the other old volcanoes, each faction trying to use evidence found there to prove its theory. The Plutonists eventually won the day.
But there was still the thorny question of when the eruptions of the Dôme had happened. Modern analysis says the lava began to form about 100,000 years ago 30 kilometers (18.6 miles) below the surface at the top of Kornprobst’s beloved mantle, partly the residue of heat in the core. It was primordial molten basalt, so superheated that it needed an escape valve, migrating inexorably up to a magma chamber underneath the Auvergne until, about 10,800 years ago, the pressure became too great. The magma chamber burst open, loosing the seething lava, which surged to the top of the volcano and exploded into the air. The blast was so powerful that it destroyed the vast east flank of the Dôme, spilling lava into the countryside. And then, 1,600 years later, after the Dôme had partly grown back, came another massive outpouring from a magma chamber fed by primitive mantle basalt. Some scientists believe there could be prehistoric communities buried in the countryside beneath the ancient lava of the Auvergne, just as there were below Mount Vesuvius.
Today, this dome within a dome is grown over, capped by the Temple of Mercury and, at the very tip, the laboratory, itself topped with instruments resembling giant white fluorescent tubes that can be seen for miles. Kornprobst and I were making our way slowly past the temple, onward to the lab, over the treacherous ice. It was late March, a week before Easter, but the cold pierced to the bone. Kornprobst’s cheeks were ruddy, hair windswept. Small piles of snow lay on the ground surrounding the temple’s outer walls. Its pale gray slabs—Brunhes’s assistant, David, must have tested their neighbors—stood out against the whitened sky. We were in an icy cloud, suspended over portending fire.
I could see why a string of religions across time and space have paid homage to the volcano and the underworld it connects to. Vulcan, the Roman god of fire, gave his name to the volcano and its study. He was the disabled god of the forge, son of Jupiter and Juno, who symbolized both life and death, making thunderbolts for his father. Japan’s Mount Fuji, which last erupted in 1708, is a spiritual lodestone, the sacred symbol of Japan itself. Pilgrims climb it at night in order to bear witness from its summit to the sun rising.
That awe has spilled over into the long literary tradition of imagining the inner Earth, a forbidden land of sin and suffering poised for the unleashing. From Dante Alighieri’s fourteenth-century Inferno of punishment to John Milton’s seventeenth-century Paradise Lost to Jules Verne’s nineteenth-century adventure tale Journey to the Center of the Earth. Verne’s heroes descend to the hellish core of the planet through an exhausted two-domed Icelandic volcano, dodging death at every turn, only to ride to the surface again on the boiling plume of a Mediterranean volcano. Or there’s a more recent iteration, the American cult television show Buffy the Vampire Slayer, whose star spent seven fraught seasons trying to keep the Hellmouth, aka Sunnydale, California, closed so the evils wouldn’t come out and destroy civilization.
Kornprobst and I made it to the final stretch of the path around the temple, and then up the slippery outdoor stairs to a single locked door. He rapped on it and a head eventually poked out. Kornprobst introduced himself. He had once been in charge of the whole works and was here to look around.
This scientist was one of the eight or ten who were working in the lab—some temporarily living there—taking samples of the air. It was a far more modern, far-ranging, and technologically intensive process than when Brunhes had run things with his single gas motor. Today, the mountain
observatory is part of the World Meteorological Organization’s Global Atmosphere Watch, a network of observatories to monitor humanity’s effect on the global atmosphere. Jean Brunhes, Bernard’s brother, the inventor of human geography, would have approved of the research.
Because the Dôme is the highest of the Auvergne volcanoes and because there is so little heavy industry between the Atlantic Ocean and it, the air quality is unusually pure, Kornprobst told me. The young scientist explained in fluent detail how one of the machines worked, and showed us a raft of that day’s findings. One number stood out: The greenhouse gas carbon dioxide was present at 403.197 parts per million—a shockingly high concentration compared to the preindustrial figure of 280. A marker of climate change, this was one of the figures Bernard Brunhes could never have imagined would be so important just a century later.
The Spinning Magnet Page 6
