Jacques Kornprobst, the man who can read the secrets of the rocks, was agitated. He had arrived twenty minutes early to pick me up at the hotel in Clermont-Ferrand, an ancient French university town perched on an annealed crack in the planet’s crust. He had the entry code at the ready to get into the free parking lot behind the building. The code had failed him.
Some drivers cruise the streets nonchalantly, certain that the perfect parking spot will open up at just the right time. Kornprobst was not among them. Parking in this city of 150,000 had become troublesome over the decades he had lived there, and as he had mapped out the day’s tightly choreographed itinerary he had made intricate plans about where to park. And now, the first parking spot of the day had fallen through.
Inside the hotel he sprinted, red-faced, fingertips frigid in the spring chill.
“Kornprobst!” he rapped out as he met me for the first time. Then he turned swiftly to the reception desk to let off a stream of injured French, explaining to the bewildered woman sitting there—she had been so friendly earlier, solicitous about replenishing the croissant basket and tinkering with the café-au-lait machine—about the affront. He had called the day before to secure the code. And now, today, he said, chin thrust slightly forward, it was malfunctioning.
Abruptly, she left through a back door. He darted out front to a tiny blue Renault car that was parked haphazardly on a curve at the corner, performed a roundabout U-turn through the city’s tortured roads, and then nosed up to the gate with its uncooperative code. The receptionist stood there, punching in numbers, shivering. He drummed his fingers on the steering wheel. Finally, the barrier began to rise and the receptionist, without so much as a glance behind her, returned inside to her desk. Kornprobst smiled grimly, thrust the little car into gear, gunned the engine, and zoomed triumphantly into a parking spot.
He was watching the clock. He was on a mission to memorialize the life and work of Bernard Brunhes, a French physicist who, along with his research assistant Pierre David, made an astounding, violently unsettling, and controversial find at the turn of the last century. Brunhes, whose name is pronounced “brune,” discovered that the planet’s two magnetic poles—north and south—had once switched places. In the decades following his discovery, his colleagues, originally aghast at Brunhes’s finding, proved that the poles have reversed not just once, but many times on an unpredictable, or “aperiodic,” schedule. The last time was 780,000 years ago.
But despite the fact that our current magnetic epoch is named after him, Brunhes has largely slipped out of the scientific memory. He does not even rate his own entry in the Encyclopedia of Geomagnetism and Paleomagnetism, the bible of the discipline of reading patterns in the Earth’s magnetic fields. Nor is he lionized in France, usually so careful to honor its own. In fact, he’s all but unknown even in his homeland, along with his grand scientific finding that the poles can switch places, that up can become down.
Kornprobst, a fellow physicist, felt that he must right this wrong. He was so committed to Brunhes’s memory that some years ago he took the trouble to find the spot in the countryside where Brunhes hacked a piece of crumbly terracotta rock—similar to the stuff of Greek vases—out of a roadcut and made his great discovery. Kornprobst painstakingly pieced together the clues about where it could be and is one of a handful of people in the world who can usually find it. The first time he made the pilgrimage to the site, he left frustrated, having failed to identify the right seam of rock. He’s found it several times since, but it’s so overgrown, so unmarked, that success is always touch and go.
Kornprobst thought that Brunhes should at least have a commemorative panel at the university in Clermont-Ferrand, so he sweated through a couple of years writing to geological agencies and eminent physicists all over the world jostling their elbows about Brunhes’s contribution to science, raising the money to erect it. Then he arranged for a ceremony and lecture to accompany its inauguration at the university in 2014. It was through that ceremony that I found Kornprobst. He wrote an article about it for Eos, a journal of the American Geophysical Union. I read it and sent him an email asking him if he would help me understand why Brunhes was so important and maybe even find that seam of terracotta. He wrote back thirteen minutes later to say he would be delighted. I was at the hotel in Clermont-Ferrand two weeks later.
Sporting a thick, off-white cable-knit sweater the same hue as his rakish hair, Kornprobst left the car in the lot and we set off briskly on foot from the hotel through the back streets of Clermont-Ferrand. It is one of the oldest cities in France, founded more than two millennia ago on the site of what was then a sacred grove of trees. And so we were marching through time, across the history of science. Up the road named after Pierre Teilhard de Chardin, a Jesuit priest and paleontologist who deeply offended the Vatican for asserting that the book of Genesis is more allegory than fact. Past the geology department of the downtown campus of Université Blaise Pascal, named after the seventeenth-century mathematician and physicist whose seminal experiment on barometric pressure was conducted a few kilometers outside the city by a brother-in-law (“There is the belief that Pascal experimented with pressure here,” Kornprobst declaimed, pointing vigorously down the street, “but it’s not true!”). Across a road named after the nineteenth-century zoologist Karl Kessler. And finally, to rue de Rabanesse, named after the tiny pale stone Renaissance castle that was Brunhes’s home and first observatory.
Kornprobst gestured to it triumphantly, eyebrows raised, as if it explained a great deal.
It looked like nothing out of the ordinary. It was standing forgotten on an overgrown patch of land across the street from a busy art school, surrounded by two layers of forbidding wire fence. Many of its lower windows—once elegant—were partially filled in with cement blocks. The parging that had covered the volcanic fieldstone that made up its walls had decayed, leaving gaps along the seams so you could see how it had all been fitted together. Its turret, where Brunhes collected meteorological information beginning in 1900, was still sturdy, reaching six floors into the sky, fifteenth-century iron fretwork still robust.
This observatory is where the tale of Brunhes begins. And where the tale of Brunhes begins, so too does the story of the discovery of the planet’s long string of pole reversals. And that story, in turn, contains the tale of the mysterious magnetic organism in the core of the planet and how it has become deeply disturbed once more, yet again deciding whether to reverse.
It was here that Brunhes, whose name means “brown” in the Occitan language of the ancient troubadours of this land, began to dream of understanding magnetism, the Earth’s secret power. We never feel it and rarely see it, but all the same, scientists and philosophers have been trying to understand it for thousands of years. For most of that time, people have imagined it to be local and transient. Magic, even. And fickle magic at that. In fact, magnetism is one of the few essential powers of the universe. To understand it, you have to go back in time to the birth of the universe, to see how the universe is arranged. And you have to do that in the company of theoretical physicists, who have developed the most precise mathematical laws so far to describe reality.
CHAPTER 2
the unpaired spinning electron
Today, magnetism is properly known as electromagnetism, one of the universe’s four fundamental physical forces. A fundamental force is one that simply exists. It is a never-ending characteristic. If you compare it to mathematics, it’s conceptually akin to a prime number—like 3 or 13—that can’t be divided into any combination of whole numbers except itself and 1. A fundamental force can’t be reduced into a more basic force; it simply is.
In theory, there are an infinite number of prime numbers. But in the universe today, there are only four fundamental physical forces—at least that we know of: gravity, strong nuclear interactions, weak nuclear interactions, and electromagnetism. (Caveat: scientists continue to look for a mysterious fifth force and
make occasional, highly contested claims that they have found it. Stay tuned.) Each of these forces is intrinsic to the workings of the universe, indispensable, inescapable. They were born along with the universe, the sun, stars, moon, and skies.
Gravity is the force that made Isaac Newton’s apple fall to the ground and that keeps you from falling off the face of the Earth as it spins. It governs bulk matter and attracts but doesn’t repel. It is the weakest of the forces but stretches to infinite space. The nuclear interactions govern the insides of atoms but nothing larger. Strong nuclear interactions hold the cores of atoms together. Weak ones (called weak because their sphere of influence is even smaller than strong nuclear interactions) allow atoms to fall apart and metamorphose into other types of atoms. That makes the weak nuclear force the ultimate alchemist. It is responsible for radioactive decay. The energy of our sun, which makes Earth the warm, livable place it is, is the result of both types of nuclear forces. As you read this, the weak interaction is allowing hydrogen protons to shed enough energy to become heavy hydrogen (deuterium) and then the strong interaction allows the atoms that result to fuse together into helium atoms.
So what is electromagnetism? It is the force that holds matter together. Apart from gravity, which holds us down on Earth, everything we see around us is due to magnetic and electric forces, explained the American theoretical physicist Sean Carroll. It is the basis of the structure of the atom, holding electrons in place and allowing atoms to link up into molecules. But where did the structure of the atom come from? From the birth of the universe itself.
So, Big Bang, about 13.7 billion years ago. The universe is created. What makes up the universe and everything in it? Is it atoms and the elements they form? To quantum field theorists, the answer can be stripped back to something more fundamental than atoms. To them, the universe is fashioned of fields: a field for each of the fundamental forces and thirteen other fields governing matter. A field is simply a mathematical way of talking about fluidlike substances that are spread out everywhere throughout the universe and have a value everywhere in the world. They ripple and sway. It’s a difficult concept. In his famous physics lectures to undergraduates at the California Institute of Technology, the late American physicist Richard Feynman said he had never been able to develop a mental image of the electromagnetic field: “How do I imagine the electric and magnetic field? What do I actually see? What are the demands of scientific imagination? Is it any different from trying to imagine that the room is full of invisible angels? No, it is not like imagining invisible angels. It requires a much higher degree of imagination to understand the electromagnetic field than to understand invisible angels.”
Some portions of the electromagnetic field can be discerned. A wave of light is a bump in the electromagnetic field that travels through space. A particle, on the other hand, exists in only one location and nowhere else. But, like light, a particle is still a facet of a field, a little wave tied up into a bundle of energy. And particles make up atoms, or the stuff we can see and feel. The most basic particles, for our purposes here, are electrons and two kinds of quarks: up and down. Each of them has its own field. If you were to think about it in biological terms, they are like the base pairs of DNA that are the foundation of every living thing on Earth. The magic of the universe is that, conceptually, any of these quarks could be exchanged for any other quark. The same goes for electrons. They and their fields are the building blocks of all matter, including you.
The inevitable implication of this, to a theoretical physicist, is that what we observe is only a portion of what is there. What we normally think of as empty space is filled with this powerful electromagnetic force field that gives matter its concreteness, as well as the other forces and fields. To physicists, this is humdrum reality.
By the time the universe is a few millionths of a second old, it has cooled down enough for quarks to join together to create protons and neutrons, the bits that will eventually form the cores of atoms. (The word “atom” comes from the Greek meaning “indivisible.” Wrong, as it turns out.) Electrons don’t join up to make anything bigger; they remain solo. These particles aren’t forming atoms at this point; the universe is still too hot. They’re just bits.
At about the 100-second mark in the life of this new universe, things have cooled down enough for some protons and neutrons to link up and make the heavy centers, or nuclei, of helium atoms—two protons, two neutrons. Give it another 380,000 years and now it’s cool enough that some of those simple nuclei have got electrons in the space around them. The electrons are negative. The protons are positive. They are responding to the maxims of the electromagnetic field: Opposite charges attract and like charges repel. So the negative electrons are drawn to the positive protons. That attraction keeps the electrons inhabiting the space around the nucleus. Neutrons, as the name suggests, are neutral. Why are protons positive and electrons negative and neutrons neutral? No one has satisfactorily explained that; they seem simply to have been born with those differences and we happened to endow them with that nomenclature. Why do opposite charges attract? Again, it just seems to be part of how the fields showed up.
Most of the atom’s weight is in its center, in the protons and neutrons that are the nucleus. The electrons are lightweights, usually in motion. Some chemists like to say that if the whole atom were the size of a baseball stadium, the nucleus would be about the size of a baseball in the middle. That means most of an atom is what the early theorists of atomic structure used to think of as empty space. Today we know that it is filled with invisible fields. Because atoms create matter, that also means that most matter, not just space, is invisible fields. That includes the matter that makes up your body. I sometimes imagine what it must have felt like for the scientist who figured that out. I imagine him looking at his hand with renewed intensity, trying to peer through it.
It’s the arrangement of these three main components of an atom—electrons, protons, neutrons—that determines which type of atom is which. If you can wade through a few more points here, you’ll get to one of the ideas that lies at the heart of magnetism.
The number of protons is key. That number determines which element it is. In other words, an element’s very identity is controlled by the number of protons in its nucleus. So is its order in the periodic table of elements, because the periodic table is arranged by ascending atomic number, from hydrogen on up.
When the number of protons changes—for instance, during radioactive decay or nuclear fusion—then the name of the atom changes as well. So hydrogen is hydrogen because it has only one proton in its nucleus. When immense heat forces a hydrogen nucleus to fuse with another hydrogen nucleus, the atom that emerges has two protons, and therefore it is helium. As goes the number of protons in a nucleus, so goes the name of the element.
By contrast, the number of neutrons and electrons in an atom can shift around without changing the atom’s name. So carbon, for example, the sixth element on the periodic table, will always have six protons. But sometimes, in nature, it has different numbers of neutrons. Those variations are called isotopes. Too many neutrons, and an atom becomes radioactive and unstable and wants to metamorphose into a different, more stable element.
It’s the electrons, which inhabit the space around the nucleus, that provide one of the secrets to the puzzle of electromagnetism. Just over a century ago, when electrons were discovered, scientists imagined them as little planets moving in a fixed track, or orbit, around a home star, or nucleus, just as the Earth does around the sun. They even used that imagery in the names they gave things, like orbits.
Today, they say instead that electrons move in orbitals, which are mathematical expressions of where electrons probably are. To me, it sounds like gobbledygook. But it just means that electrons are not in a track but somewhere in a pretty well-defined three-dimensional cloud around the nucleus. Probably. You can’t point to a spot and say that’s exactly where an electron is right now
. And it’s not necessarily in an orbit. Orbitals have many theoretical shapes, some spherical, others complicated three-dimensional figure eights or dumbbells, others far more complex.
The basic, extremely counterintuitive, but absolutely critical idea is that the electron and other particles operate as both a fluidlike component of a field and as a single physical particle at the same time. They are components of the fields that form the universe. For example, when electrons jump from one orbital to another, they are acting as individual physical entities. But when they are incapable of being in a single identifiable place at any time, they are acting like a wave or a field. To understand electromagnetism, we have to live with the complexity of this.
There’s a little more. While the planetary language to describe electron behavior is now obsolete, it is still helpful as a mental image. So is the fact that the orbitals are arranged in groups of concentric rings or layers or shells around the nucleus. That simplification makes them a little easier to visualize. A central point is that the farther away from the nucleus the electron is, the more energy it has and the more apt it is to be able to be persuaded to move away from an atom’s influence.
The idiosyncrasies of these electrons in orbitals provide one way to create a magnetic field. With some exceptions, every electron in the universe is held in one of these orbitals or is in the process of moving into one. But one of the unbreakable rules of the universe is that each orbital has room for only two electrons—a pair—and the electrons in a pair must spin in opposite directions. Confusingly, here the metaphor to describe direction comes from watchmaking: If one in the pair spins clockwise, then the other must spin counterclockwise. The point is that one movement must offset the other in order to reach balance. In addition, each orbital is contained within a shell, or grouping, that can hold a fixed number of pairs of electrons.
The Spinning Magnet Page 2
