The Spinning Magnet

by Alanna Mitchell

  Electrons have strong preferences when it comes to inhabiting their orbitals. They fill them up in highly regimented ways. In fact, they have a rigid code of conduct that can be broken only in exceptional circumstances, filling up one shell of orbitals before moving on to another. Going back to the image of the baseball stadium, it’s a little like filling up seats at ground level close to the diamond first, and then, if there are enough electrons, moving higher up and farther away, section by section, row by row.

  Electrons strongly prefer not to be in pairs. They’d rather have a solo slot in an orbital. Pairing is a last resort. But they’ll do it before spending the energy to move to a higher shell, or level in the stadium, where they could have a slot all to themselves.

  A rather unselfconscious university chemistry teacher, perhaps remembering a beer-soaked baseball game from his youth, once described it this way: Imagine you have six young men who urgently need to urinate, and only three urinals. Each of the first three men in the line will naturally take a separate urinal. At that point, each of the others will ask to share one of the urinals. They don’t show up two to a urinal when there are empty ones. They prefer to have one to themselves. And when even the second spot at each urinal is taken, the knee-clenching next men in line are forced to go upstairs to another bathroom.

  But while each orbital has an even number of slots—two—each atom does not have to have an even number of electrons. That means sometimes electrons have a slot in the orbital all to themselves. They are unpaired. The French call them “celibate.”

  This is where magnetism comes in. When a material is made up of atoms with one or more unpaired spinning electrons, the atom itself creates a tiny magnetic field. But in some unusual substances, a majority of those solo electrons can be made to spin in the same direction, lining up, magnifying the field in a larger material, making a sphere of influence greater than themselves. In most substances, that field is weak and passing and can be measured only by sensitive instruments. In some, the fields within a substance organize themselves in such a way as to cancel each other out instead of amplifying each other. But a few atoms can retain a strong magnetic field. The most common are iron, cobalt, and nickel. The iron atom has four unpaired electrons in its outermost rank of filled orbitals. Cobalt has three and nickel, two. When those elements combine with others to make such materials as magnetite or terracotta or basalt, the magnetic field within the material can last a very long time.

  Because unpaired electrons spinning in the same direction create a magnetic field, it makes sense that a magnetic field itself flows in a direction. It does. As with the orbitals, scientists use everyday planetary imagery to describe this phenomenon. They say that a magnet has a north and south pole, where the field is strongest, and that the field travels from north to south.

  Magnetic fields moving in the same direction repel each other and those moving in the opposite direction attract. It’s the same idea as the positive and negative charges of the protons and electrons within the atom’s structure: Opposite charges attract, like charges repel. So when you try to stick a south-facing magnet to a north-facing one, they click together, making the field bigger, magnifying it. But try to put two souths or two norths together and the magnets push each other away. They resolutely refuse to join. This is the fundamental push and pull of the magnet. It is their strong, invisible fields that are doing the pushing and pulling, the same fields that the universe is made of.

  Along with direction, a magnet also has a strength or intensity. As you can imagine, if you have a single atom, the field is pretty weak, no matter how many unpaired spinning electrons there are. Gathering a lot of atoms with unpaired spinning electrons together makes a stronger, or more intense, field. So a larger magnet is stronger than a small one. And joining two magnets together, like the south- and north-facing ones we just talked about, creates a more powerful magnet. It makes sense. You’ve got more of those unpaired spinning electrons all pulling in the same direction.

  To fully describe a magnet, or the field it creates, it follows that you need to be able to talk about both direction and intensity. Mathematicians call something made up of two components a vector. We use the language of vectors when we talk about velocity, which is direction as well as speed. So, the car’s velocity is 100 kilometers an hour to the northeast. That’s different from saying that the car is traveling northeast (just direction), or saying that the car is traveling 100 kilometers an hour (just speed).

  The big picture is that if the universe had been created without the fundamental force of electromagnetic interactions, it would be a profoundly, unimaginably different place, right down to the structure of every atom.

  CHAPTER 3

  parking in the shadow of magnetism’s forgotten man

  Kornprobst was walking around the perimeter of the property on rue de Rabanesse, savoring Brunhes’s role in transforming the science of magnetism. But he wanted to make it clear that he was not an expert on magnetism, just on Brunhes. I was not fooled. There is a tradition among scientists to disavow knowledge of a field unless they have published scores of papers on it. Kornprobst knew much more about magnetism than all but a few hundred people on the planet.

  As a young scientist, he fell in love with the Earth’s mantle, the thickest of the planet’s four layers. It is named after a cloak because it encloses the spherical outer core and inner core. Most of the mantle is enclosed in its turn by the rocky crust. There are a few exceptions where it pokes through. “It was Morocco,” Kornprobst said, sighing, a dreamy look in his eye. “There is a splendid piece of mantle there.”

  The mantle is a highly pressurized mass of silicon-based material—the same element we use to make computer chips—heated by radioactive energy. It moves sedately all the time, more slowly than the core. And the crust, formed of hard tectonic plates, moves yet more slowly still over the top of it, shifting the continents and oceans millimeter by millimeter. Occasionally, the plates rip apart or suck each other under, which can result in earthquakes or volcanic eruptions. Like the inner and outer cores, the mantle’s job is to get rid of some of its heat, which is the point of volcanoes and earthquakes. That impulse to shed heat is also the agent behind the Earth’s own magnetic field, the one generated within the core. The planet’s heat moves from the inside out: from the inner core to the outer core and into the mantle and then the crust. To understand the mantle is, therefore, to have some understanding of the core and of the magnetic force itself.

  When Kornprobst was head of the geology department at Université Blaise Pascal in Clermont-Ferrand in the mid-1980s, he established a research center on volcanism and magnetism that put the university at the forefront of the field globally, part of the long love affair French academics have had with the discipline. For ten years, ending in 1998, Kornprobst was the director of l’Observatoire de Physique du Globe in Clermont-Ferrand. It’s the same job Brunhes held when he lived in this tower on rue de Rabanesse in the first years of the twentieth century. And this tower was the original Observatoire de Physique du Globe of Clermont-Ferrand.

  At the base of the tower was a thick plank door, so low as to encourage stooping. Brunhes must have entered his home and observatory by that door, walked up the six flights of stairs; he must have stood behind the railing of that round turret and thought about both the stars of the universe and the roiling of the planet’s core. Some of the trees still standing on the land looked old enough to have lived there when Brunhes and his family did.

  A sign hung from the fence. Despite the fact that the structure had been designated a French historic monument in 2009, the property had been sold and was slated for redevelopment into forty-two housing units. Kornprobst set his mouth in a straight line. Again the chin jutted out. He had already helped to organize a student protest about the plan. He wasn’t about to stand still for the desecration of Brunhes’s first observatory.

  The slender Rabanesse tower in Clermon
t-Ferrand started out as a link in a European chain to gather information about weather and atmospheric conditions, Kornprobst explained. Originally, it had nothing to do with magnetism or with changing the course of science.

  It was connected by telegraph line to the world’s first mountain meteorological observatory on top of the Puy de Dôme volcano outside Clermont-Ferrand. The volcano is the most famous in the ancient chain of volcanoes scattered through central France, so steep and forbidding that it once formed part of the route for the Tour de France bicycle race. Even today, it is an overwhelming presence in the city, an all-seeing giant. On a clear day, you can see the observatory perched on the volcano’s summit, still collecting data about atmospheric conditions.

  In turn, Rabanesse was joined to Paris, forming a network of meteorological observations from the mountain to the plains to the capital and from there to Europe. But Brunhes was not only interested in meteorology. Born in 1867, he came from a remarkable family, the oldest of seven intellectually gifted children, according to a short biography of him published in 1999. Perhaps he wanted to make his own mark.

  His father, Julien, was the son of a master shoemaker in Aurillac, about two hours’ drive south of Clermont-Ferrand. Julien made the leap from the trades into academia, eventually studying in Paris and becoming a physics professor and then dean of science at the University of Dijon.

  Both Bernard Brunhes and his younger brother Jean followed their father into the sciences. In fact, after Julien died in 1895, Bernard took his place on the Dijon faculty. But it is Jean, a geographer, who is the better-known brother, famous for inventing the term and discipline of “human geography”—a social science that examines humans’ interaction with the environment.

  The impression that emerges of Bernard Brunhes from his published papers and the biography is of a frail but driven man, a fervent Roman Catholic and an idealistic social reformer. He and Jean traveled to Rome to meet Pope Leo XIII at the Vatican in 1892, part of a delegation of young Christian socialists. The brothers were inspired by the 1891 papal encyclical Rerum Novarum (About New Things), the first to explore the conditions of the working classes. It is the foundation for the modern Catholic understanding of social justice and climate change, including the work of Pope Francis. Motivated by the encyclical, the Brunhes brothers gave night courses to blue-collar workers.

  Academically, Bernard Brunhes was a polymath, like so many scholars of his era. His interests ranged from optics to acoustics, from electricity to thermodynamics to X-rays, from horticulture and botany to what today would be called environmentalism. But in 1900, after he was named director of the observatory in Clermont-Ferrand, as well as a professor of science, he enthusiastically switched gears: The emerging discipline was geophysics. It’s a broad field, taking in the shape and structure of the planet and its atmosphere. But it also encompasses seismology, gravity, volcanism, and magnetism.

  Brunhes renovated the observatory on the Puy de Dôme, making it bigger, installing a gas motor to run electricity—a brave innovation—and sending his apprentice Pierre David to live there full-time. As for the Rabanesse tower, Brunhes reckoned that it was in the wrong place to produce the best meteorological data, so he devised a plan to build a magnificent new building several kilometers away.

  Brunhes’s ardor, as he sifted through weather data, ran the Rabanesse tower, and renovated the mountain observatory, turned to the magnetism of rocks. Basic questions were unclear. How did rocks get a charge and hold on to it? How could you tell when they had become magnetic? What did magnetic rocks tell you about the workings of the planet?

  By this point in our day’s schedule, Kornprobst was driving his little Renault toward the empty parking lot of Les Landais. This was the grand building Brunhes commissioned early in the twentieth century to be built on what is now the main campus of Université Blaise Pascal. He leapt out of the car, looked around possessively, and slowly filled his lungs with the scent of cherry blossoms. Les Landais is a handsome two-floor red building with banks of windows surrounded by a bewildering assortment of cherry trees and a couple of outbuildings. Opened in 1912, it was a dramatic step up from the tiny Rabanesse tower downtown. Kornprobst had been director at this building for nine years, and it was the scene of many of his own triumphs: a Doppler radar that could determine the speed of particles in volcanic clouds, and a seismological observatory with one of France’s dozen seismometers, providing up-to-the-minute measurements freely available to the public and scholars in case anyone wanted to track potential earthquake activity.

  The main building had been turned over to the French geological survey—the Bureau de Recherches Géologiques et Minières (BRGM)—which collects information about such things as water levels, boreholes, and seams of coal, lead, and uranium in the region. Its latest director had started there only a handful of weeks earlier and Kornprobst, with his customary efficiency, had called ahead to inform her of his visit. He marched up to the door. “Kornprobst,” he declared when she arrived. She looked startled at his vehemence, but showed him around.

  He was taken aback, perhaps horrified by all the renovations in his former office. The luxury! A wide desk. Magnificent views. From her office, he pointed to the next stop on our itinerary: a huge new building just across a field, with hardly any parking at all. We would leave the car in the parking lot of Les Landais and walk, he said.

  Now the director was soothing. Surely Kornprobst could brave the parking stress? We went back to the car. He drove up to the imposing modern cement complex and, rather defiantly, parked in front of it in an illegal spot. It was the third and current home of l’Observatoire de Physique du Globe de Clermont-Ferrand, Kornprobst’s pride and joy.

  He can trace the observatory’s history from the Renaissance tower to Les Landais to this cement behemoth. Among all the physicists who have ever lived in France, just Kornprobst and Brunhes have held the same two important roles: directors of l’Observatoire as well as the guiding minds behind building more modern incarnations of it.

  That affinity has led Kornprobst on this quest to make sure the world—or at least the observatory’s students and staff in Clermont-Ferrand—remembers Brunhes. It’s a strangely hard slog. The scientific memory is usually precise and generous. Kornprobst gestured to an imposing stand-alone panel directly in front of the building. This was the panel he had written about in Eos. It was made of brilliant turquoise-colored enameled lava—the lava part is an in-joke among volcanologists and the paleomagnetism crowd—set on two sturdy legs. It celebrates the centenary of Brunhes’s find in sharp white script, featuring a side-view portrait of Brunhes in relief.

  Brunhes is depicted as a slender man with a carefully trimmed, pointed beard, long neck, and crisp, high collar reminiscent of the fin-de-siècle. This panel and a plaque inside the building featuring the same portrait are, so far, the only two formal monuments in France to Brunhes. Despite Kornprobst’s efforts, Brunhes is still a forgotten man of physics.

  Gleefully, Kornprobst motioned to the depiction of a compass in the panel’s bottom right-hand corner. Four arrows, one pointing to each of the four ends of the Earth. Except in this version, east and west are just where you’d expect and north and south have changed places. It is a puckish reminder of what Brunhes found but also a little-known modern scientific truth: Today’s north is actually in the south. That’s because in magnetic nomenclature, the pole from which the magnetic field flows is its north. The receiving pole is south. Today, the field flows from what we call the South Pole.

  For the entire time Homo sapiens has been trying to unravel the mysteries of magnetism, those magnetic poles have been on the opposite sides of the Earth from what we imagined.

  CHAPTER 4

  into whose embrace iron leaps

  Because magnetism is ultimately about how the planet, its geological features, and even its species came to be, new findings have often kicked up against religious orthodoxies. Frequen
tly, as Brunhes found out, they have challenged scientific ones too. Some of the investigators have put reputation, jobs, freedom, and even their lives in jeopardy when their discoveries called into question the teachings of the day. For generations, it has taken a countercultural imagination to puzzle out the meaning of magnetism.

  The very name “magnet” has ancient roots in the arts. It goes back to the classical Greek poet Homer, who wrote his famous epics, The Iliad and The Odyssey, in about the eighth century BCE. Those epics, in turn, were based on the tales of oral poets whose work came even before the invention of the alphabet. Homer writes about the mythical hero Magnes, a son of the Greek god Zeus, who was king of a region of Thessaly in central Greece. It was named Magnesia after him and his people, the Magnetes. One of the minerals common in the lands of the Magnetes was a substance that came to be called magnetite, after the people, their land, and their hero king.

  Magnetite, an iron oxide, is a naturally occurring permanent magnet, which means that enough unpaired spinning electrons in its molecules stay lined up in the same direction to keep its field strong. For centuries, magnetite has also been known as lodestone, a word that has crept into literature as a metaphor for a power that guides one’s life, or a moral reference point. Modern analysis shows that Thessaly, in Greece, is home to rare pure compounds of magnetite, which means that they were unusually strong natural magnets.

  Another tale, told by the Roman author Pliny the Elder in his first-century encyclopedia Naturalis Historia, or Natural History, is that a shepherd named Magnes discovered the charged stones when the metal in his shoes and staff stuck to them on a mountain in either Asia Minor or Crete. His name became the name of the substance “into whose embrace iron leaps,” Pliny writes.

  But why does the iron leap? Early Western philosophers toyed with two main explanations, as the historian A.R.T. Jonkers chronicles. One camp held that magnets were drawn together, just as living creatures were, by an affinity or sympathy for each other. The other believed that the attraction was mechanical, born of actual particles or emanations or “effluvia.”