The Spinning Magnet

by Alanna Mitchell

  Brunhes never published on the magnetic field again, although he continued to research it. On Sunday, May 8, 1910, he had just returned to Clermont-Ferrand from a trip to the Cantal, where he had been taking measurements in some mines. The weather was foul, and it was snowing heavily. Despite the snow and his own fatigue, he left the Rabanesse tower near midnight to find out the results of a civic election in a nearby town. Shortly after, police officers making their rounds in the ancient streets near the tower found a man unconscious on the ground. It was Brunhes. They took him home, but he’d had a massive stroke. He died at noon on Tuesday, May 10. He was forty-two.

  He did not live to see his grand new observatory, Les Landais, which opened two years later. He did not live to see the vindication of his outrageous theory of reversal, or to discover that the Earth’s magnetic direction had flipped not just once but hundreds of times in its history. He would never know that this current magnetic phase of the Earth’s history is named after him. The man who traveled by mule and horse did not live to see all the new data from satellites orbiting Earth showing that its field is becoming daily more disturbed, and that part of it in the southern hemisphere has already changed direction. He could not have known that a century after his death scientists would be debating whether the poles are gathering strength to reverse once again. Or that the vast electromagnetic infrastructure humans have built will be in danger when the poles switch places. He could never have foreseen that scientists are struggling to understand what such a reversal could mean for life on Earth, the great spinning magnet that is our world, or the likelihood of it being utter catastrophe for human civilization.

  PART II

  current

  Our physics, therefore, will no longer be a collection of fragments on motion, on heat, on air, on light, on electricity, on magnetism, and who knows what else, but with one system we shall embrace the world.

  —Hans Christian Ørsted, 1803

  CHAPTER 10

  experiment in copenhagen

  The Niels Bohr Institute in Copenhagen, birthplace of modern physics, was festooned with a modern art installation the day I arrived. The building was covered with an array of lights connected to CERN, the European nuclear research laboratory more than a thousand kilometers away, and they blinked to life whenever subatomic particles, ruthlessly torn apart in the magnetic field within its underground Large Hadron Collider, bashed into one another. Which of the LED lights became bright, and how fast and for how long, depended on which particles were hurtling toward one another in CERN’s engineered replica of the primordial cosmos. It was, said the artists who conceived it, as if the music of the universe’s birth were being transposed into a symphony of light on the building’s dun façade.

  This stately, red-roofed set of laboratories and offices was built in honor of the Danish physicist Niels Bohr in 1920. Bohr won the Nobel Prize two years later for developing the first simple image of the atom’s internal architecture: electrons buzzing around a nucleus that is fashioned of protons and neutrons clinging together. Bohr peered into the heart of matter for the first time, and his institute became a mecca for theoretical physicists from all over the world in the sensitive era between the two world wars when physicists were wrestling with the potential of splitting those nuclei to make the atomic bomb. Even the institute’s address, Blegdamsvej 17 (17 Bleaching Pond Road, named after the nineteenth-century Copenhagen laundrymen who wet linen in designated ponds and then let it bleach in the sun), is evocative to the physics community, much as London’s 221B Baker Street is for fans of Sherlock Holmes and detective fiction. The institute was named a historic site in 2013 by the European Physical Society for the sheer magnitude of breakthroughs in physics conducted within its walls.

  Andrew D. Jackson, a theoretical physicist with a wry sense of humor, met me at the door and welcomed me in. He was unfazed by the legend of the place. Grinning, he gestured upstairs. The bathtub of the German wunderkind physicist Werner Heisenberg, who won the Nobel Prize for his work in founding quantum mechanics, was upstairs. Did I want to see it? Jackson asked me, chuckling, before leading me into his office.

  Jackson, whose voice still bears the trace of his New Jersey upbringing, normally works with some of the more obscure—and sometimes purely conceptual—pieces of the atom that did not figure into Bohr’s original image. He has written about mysterious subatomic bits such as skyrmions and about wave packets known as solitons. But a few years ago, one of those curious coincidences that skitter through science propelled Jackson and his Danish wife, Karen Jelved, a scholar of English literature, into the sphere of the nineteenth-century Danish scientist Hans Christian Ørsted, whose work provided a piece of the electromagnetic puzzle that irrevocably changed physics.

  In the summer of 1993, the Harvard University historian of science Gerald Holton was in Demark visiting a friend who owned a medieval castle south of Copenhagen. On its library shelves, which had been filled with books purchased by the meter, Holton came across a rare first edition of a work by Ørsted, who died in 1851. As it turned out, Holton had been awarded the prestigious Ørsted Medal for teaching physics in 1980, and as a result had given a talk decrying the invisibility of Ørsted. For one thing, Ørsted wrote mainly in Danish and German and few of his works were translated into English. For another, by the time he died, Ørsted’s ideas were wildly unfashionable. Yet his work tracked the tectonic shift from Romanticism to modernism in science during the nineteenth century. How fitting it would be, therefore, to introduce the world to Ørsted’s immensely important works, Holton mused to his host. She, in turn, was a friend of the physicist and science historian Abraham Pais, a colleague of Albert Einstein who had once been Bohr’s assistant, and she told him about her dreams for broadcasting Ørsted’s legacy. Pais and Jackson had lunch together every day, and Pais knew that Jackson and Jelved were looking for a new project that could make use of their skills in both language and science. Pais talked to Jackson. And that, as they say, was that.

  Jackson and Jelved have become known as the English voice of Ørsted, publishing his works on science, literature, poetry, and philosophy. Few understand him better. (“It’s my experience that most good scientists are romantics, and it’s pretty lonely,” Jackson told me as he tried to help me understand Ørsted’s life.) They helped translate a key volume of his selected scientific works, as well as plowing painstakingly through the letters he wrote home during eight journeys within Europe in the first half of the nineteenth century. Ørsted wrote his letters in a Gothic script, using a quill pen and paper so punishingly thin that the ink soaked through. Worse, he frequently underlined words for emphasis. At one point, worried about the money he was spending on postage, he decided to start writing just as much, only half as big, Jackson told me, groaning slightly.

  Not only that, but Ørsted’s daughter, Mathilde, who published a short, heavily edited version of his letters in 1870, eradicated evidence of her father’s aborted first engagement. In 1801, Ørsted had pledged to marry his mentor’s household employee, Sophie Probsthein. Ørsted finally married Mathilde’s mother, Inger Birgitte Ballum, known as Gitte, in 1814. The attempt to blot out evidence of the relationship succeeded until Jackson and Jelved pieced together evidence of the hidden love affair.

  Ørsted’s travel and professional life coincided with the heady decades of the first half of the nineteenth century, which have since been called the Danish golden age. In the few years straddling the beginning of that century, Copenhagen, then home to about one hundred thousand, had suffered through two widespread fires and two devastating bombardments by British forces. The city needed to be rebuilt and the process spawned a creative surge that spanned architecture, literature, music, visual arts, and finally science. Hans Christian Andersen, who wrote the beloved fairy tales, was among the most famous figures of the age and was a close friend of Ørsted.

  Ørsted took the golden age at a canter, and the letters show him using his j
ourneys and growing fame to try to raise Denmark’s status within Europe. He was an inveterate name dropper, Jackson confided, and he met nearly everyone of any consequence. One of the highlights of his life was meeting his idol, Sir Walter Scott, on July 4, 1823, in Edinburgh.

  His travels also introduced him to some of the magnetic ideas floating around Europe at that time. During the 1823 trip abroad Ørsted made measurements of the Earth’s magnetic field and, later, on his final journey in 1846, traveled by steamship down the River Thames from London to Greenwich—under the arches of Waterloo Bridge, Blackfriars Bridge, and London Bridge, he recounted with obvious delight in a letter home—to visit its famous magnetic observatory.

  In 1827, he journeyed to Altona, near Hamburg, Germany, then under Danish control, to take part in a meeting of the finest magnetic minds in the world. The peripatetic Alexander von Humboldt, who had set up the first system of relative measurements of a magnetic field’s intensity based on readings from a village in Peru, was there. So was the brilliant mathematician Carl Friedrich Gauss, who later worked out how to measure the field’s absolute intensity. Along with Ørsted and others, they proposed the establishment of the first global network of magnetic measurements. The meeting resulted in the formation of the Magnetic Union of Göttingen, which launched in 1834 and was the first international scientific collaboration and the forerunner of CERN.

  It wasn’t just measurements the Altona group wanted. They also pushed for a plan to finally pinpoint the location of the Earth’s magnetic north pole. Just four years later, on June 1, 1831, it happened. The Arctic explorer James Clark Ross, stuck with his small ship and crew in the ice, discovered it near the very northern tip of what is now mainland Canada using a magnetic needle suspended from a silk thread. He built a cairn out of stones to mark the spot, raised the British flag, and called the area British. It was a rich piece of luck that he discovered it at all. The pole had been on a lengthy trip south and was near its most southerly point in centuries. It has been heading north nearly ever since, now veering away from Canadian territory and into Russia.

  Ørsted is not invisible in the way that France’s Bernard Brunhes is. Rather, it’s the breadth of his achievements that has slipped from public memory. He is a cherished figure in science for a single experiment he did in 1820, not for his decades of scientific exploration. On the basis of that one experiment, conducted in public, he is considered Denmark’s scientific genius of the nineteenth century just as Bohr is the genius of the twentieth. Today, a park in Copenhagen is named after Ørsted and his famous younger brother Anders Sandøe (who was an architect of the Danish constitution); a university he founded is the international home base for a set of satellites tracking the Earth’s magnetic field; a satellite named after him is still in the skies; the Ørsted law is a centerpiece of the physics of steady electrical currents and the Ørsted unit of measurement is part of the scientific description of magnetism; and physics prizes and a coveted fellowship are awarded in his name even now.

  His grand finding? In 1820, after having thought about it for the better part of two decades—and against the reigning scientific doctrine of the day—he conducted an experiment showing that magnetism and electricity are physically connected. The find galvanized research across Europe, leading the British physicist Michael Faraday to create the prototype of an electrical generator the following decade. That inadvertently sparked the Second Industrial Revolution. (There is a tale—likely apocryphal—that, when asked by Britain’s Chancellor of the Exchequer, or finance minister, how electricity could possibly be practical, Faraday quipped: “One day, sir, you may tax it!”) Over time, Faraday’s findings led others to develop the mathematic equations that describe electromagnetic theory. Ørsted’s discovery was one of those rare moments in scientific history that change everything that comes after. I was in Copenhagen hoping that Jackson would help me understand why.

  CHAPTER 11

  a very intimate relationship

  For almost the entire time that scientists have been examining electricity and magnetism, they have believed that the two were different. But actually, magnetic and electrical phenomena are not just connected, they are facets of the same thing. That’s why physicists now call this fundamental force of the universe the electromagnetic force. “Magnetism and electricity are not independent things . . . they should always be taken together as one complete electromagnetic field,” Richard Feynman said. The two, he said, waxing lyrical, have a “very intimate relationship.”

  To understand the electrical force, we have to go back to electrons and protons. The electron is negative. The proton is positive. These electric charges are the sources of the electrical field. Like the magnetic and other fields, the electrical field is the stuff of the universe, stretching out through it in fluidlike lines that can move in peculiar ways. Electric and magnetic field lines tend to go hand in hand. But there are a few differences between the two fields. While magnetic field lines run in unending loops, electrical field lines can end. And while electric charges can exist as solo particles that are either negative or positive—like electrons and protons—every magnet known in nature has two poles, north and south, just as Petrus Peregrinus discovered in the thirteenth century. No matter how small a magnet gets, those two poles are always present. (Scientists keep looking for a magnetic monopole but have not yet found one.) That means there are no independent magnetic charges.

  So where does the magnetic field come from, if not from magnetic charges? Here’s where things get a little more complicated than the unpaired spinning electron. It turns out that the magnetic field depends on electrical charges. While the Earth is the source for the Earth’s gravitational field and electrically charged particles are the source for the electrical field, it’s the electrically charged particles themselves that create the magnetic field, but only when they are moving. In other words, a stationary charged particle makes an electrical field but not a magnetic one. A moving charged particle makes an electrical field and an electrical current, which makes a magnetic field. That can mean a bunch of moving charged particles in a current, or it can be the spin of an electron within an atom. You can take the idea down to the scale of a single atom of iron. Its negatively charged unpaired spinning electrons are creating a tiny circulating electrical current. That means the atom itself is also creating a tiny magnetic field. If you put enough of these atoms together so that the tiny magnetic fields arrange themselves to amplify one another instead of canceling one another out, you get a magnetic substance. In effect, as Feynman said, all magnetism is produced from currents of one sort or another.

  Albert Einstein realized that what constitutes “movement” here depends on one’s frame of reference. If you are at rest with respect to an electrical charge, you will see an electrical field. If you are moving with respect to the same electrical charge, you will see a moving charge, which is producing an electrical current as well as a magnetic field. The same is true when you are stationary with respect to an electrical charge that is moving. It’s all about perspective. It’s all, as Einstein would say, relative.

  The journey to entwine electrical and magnetic forces culminated with Einstein. But it has scampered across thousands of years, winding through myth, dogma, experimentation, and, finally, mathematics. The fact that these phenomena are facets of each other came as a surprise. Consider this: The name “electromagnetic,” one of the many words that Ørsted coined, contains within it William Gilbert’s cranky christening five hundred years ago of the word “electricity” from the Greek word for “amber” as well as Homer’s telling of the tale of the ancient hero-king Magnes nearly three thousand years ago, patched onto the evolution of those ideas in the centuries since. Were we to magically erase all that rich history and metaphor embedded in the current label and name the electromagnetic force anew, knowing what we know about physics today, we would give it a label that clearly indicates that magnetism and electricity are the same thing.


  The electromagnetic force is one foundation on which the whole universe rests, at play in each single small piece of each atom. The electromagnetic field can manifest itself as waves, or vibrations, that can be any length. We see some of the tiny waves in the form of light and color, which means, by definition, that light is also electromagnetic. By a pleasing symmetry of nature, the charges all seem to balance one another out most of the time, making the universe electromagnetically neutral. Most of the time, we aren’t even aware of the electromagnetic force that is so powerfully at work.

  So, the electrical force is produced by charged particles. Electricity, on the other hand, is electrons in motion. The earliest forms of electricity that scientists became aware of were what today we would call static electricity. A spark is static electricity, and so is lightning and so is the emanation from rubbed amber that attracts a piece of fluff, the phenomenon that led Gilbert to name electricity in the first place.

  You’re making static electricity when you rub a balloon on your hair. The balloon steals a few electrons temporarily from your hair, making the balloon slightly negatively charged and your hair slightly positively charged. If you hold the balloon overtop your head, your hair will fly up to meet it. The hair’s positive charge wants to be reunited with the balloon’s negative, and the force between them is strong enough to lift your hair. Eventually, the electrons drift away from the balloon and the hair falls back down. The rubber in the balloon is called an insulator because it doesn’t easily conduct electrical charges. Insulators used to be called “anti-electrics,” and include other things such as glass and wood and plastic. When insulators capture extra electrons, they store them, like the balloon does, rather than pushing them somewhere else. Insulators can also isolate pockets of opposite charges from one another.