What magnetism’s mysteries mean (and don’t) for Earth
Every author hopes that their book release will make a splash, and Alanna Mitchell’s new book has certainly done so. That’s the good news. The bad (or, at least, awkward) news is that after the first wave of coverage, there was a second, smaller splash, in which Mitchell was taken to task over the validity of one of the book’s central themes, namely that a reversal of Earth’s magnetic field could wreak havoc with life on our planet.
Let’s look briefly at this initial media splash. In January, Mitchell wrote an article summarizing some of the main ideas in the book for Undark, a (very good) online science magazine. (Disclosure: Mitchell helped organize a book event where she and I both spoke, in Winnipeg, some years ago.) After the Undark article appeared, numerous media outlets picked up the story, almost all of them (as far as I can tell) playing up the doomsday angle. Sample headlines include: “Earth’s magnetic poles could be about to flip—with serious consequences for humanity” (International Business Times); “Earth’s magnetic poles might be gearing up for a long-overdue flip—leading to a planet-wide blackout” (Newsweek); “Earth ‘under attack from within’ and could face ‘blackouts for decades’ as the poles flip” (London Express).
On the website of Canada’s own Quirks & Quarks radio program, the headline was even more over-the-top: “When our magnetic field flips, say goodbye to modern life.”
The rebuttals quickly followed. An article appeared on National Geographic’s website with the headline, “No, we’re not all doomed by Earth’s magnetic field flip,” while a post on the Science 2.0 blog carried the headline, “NO NO NO—a magnetic pole flip will not make parts of Earth uninhabitable.”
Clearly Mitchell, like every non-fiction writer, has struck a balance between the need for accuracy and the urge to provoke. (Note the book’s subtitle, “The Electromagnetic Force that Created the Modern World—and Could Destroy It.”) Mitchell constantly teases the reader with the notion that Earth’s magnetic poles are overdue for a flip, and highlights the harm that this may cause; on the other hand, she also makes it very clear, especially toward the end of the book, that there’s no need to panic. It’s probably safe to say that most of the media outlets that ran panic-oriented stories didn’t read the book to the end—in fact, they likely just relied on the Undark piece.
This is a book about the mysteries of magnetism, and, especially, the peculiarities of Earth’s magnetic field. The effects of magnetism have been known since antiquity; certain rocks, known as lodestones—we now know them as the mineral magnetite—were seen to attract small bits of iron; as well, if suspended from a thread, a lodestone would line up roughly along a north-south line (the key to the magnetic compass, used for navigation for millennia). But exactly how lodestones worked, and the nature of magnetism in general, remained an enigma for centuries; the structure of Earth’s own magnetic field, meanwhile, was another mystery.
A good chunk of this book, then, concerns the history of science—it is the tale of how we’ve come to know what we know about magnets and magnetism. We meet thinkers such as William Gilbert, the English physician and natural philosopher who wrote the first modern treatise on magnetism around the time that Shakespeare was writing Hamlet. In the 19th century, key figures include Hans Christian Ørsted, Michael Faraday, and James Clerk Maxwell; the work of each of these scientists added to the growing mass of evidence linking magnetism to electricity. (It was Maxwell who gave this electricity-magnetism link a solid mathematical basis—we now call this single force “electromagnetism”—paving the way for Einstein’s work on relativity early in the 20th century.) We also meet more obscure figures like Bernard Brunhes, a French geophysicist. His study of a peculiar outcropping of rock in south-central France, in the early 20th century, led him to believe that Earth’s magnetic field had once pointed in the opposite direction. He was right, though it took half a century before the scientific community took the idea seriously. Acceptance of the book’s key idea—that such “flips” have happened numerous times over history, and will at some point happen again—also came slowly.
We also meet an eclectic array of living scientists. Among them is Jacques Kornprobst, an affable French geologist and volcanologist who introduces himself by yelling “Kornprobst!” whenever he enters a room. Kornprobst feels that Brunhes ought to be more of a household name, and to that end he takes Mitchell on a road trip through rural France, in search of the particular hillside where Brunhes found his telltale oppositely magnetized rocks more than 100 years earlier. This kind of storytelling is Mitchell’s strength. She’s not a scientist herself, but that’s okay: She has found the geologists and physicists who know this stuff, she’s asking them the right questions, and she’s letting us come along for the ride.
There are occasional bumps along the way, sometimes involving the history, sometimes the science. Mitchell’s gloss of the historical relationship between science and religion (and especially the Catholic Church) skews toward a portrait of unending conflict, a picture that modern historians would dismiss as simplistic. One might note, for example, that Jesuit astronomers were Europe’s leading observers of the night sky, and that astronomical knowledge was essential for calculating the date of Easter. And while the Italian thinker Giordano Bruno was indeed burned at the stake for heresy, this was not, as Mitchell suggests, primarily for his scientific views. She puts Belfast in “Ireland,” rather than Northern Ireland—not a trivial distinction. And, at the risk of nitpicking, she describes Victor Frankenstein as a “doctor,” even though Mary Shelley never describes her protagonist as such. On the science side, photons are particles, not “extremely short electromagnetic waves.” And Mitchell’s definition of the three-body problem is a bit muddled: “It goes like this,” she writes. “You have three particles (or heavenly bodies, originally) moving in space, connected by their gravitational pulls. You know where they are now. Tell me exactly where they will be in the future.” She ought to add that we are given the bodies’ initial velocities; if we don’t have that information, then we cannot tell how one body will move, let alone three. Again, Mitchell is a journalist, not a scientist; that by itself isn’t a problem, but there is a certain lack of precision that occasionally crops up. For example, she refers to the sun “entering the critical phase of its summer solstice” in mid-June. It’s a peculiar phrasing—solstices don’t have “phases”—but presumably it’s a way of saying that the solstice was just a couple of weeks away.
And what about the central claim? As Mitchell explains, Earth’s magnetic field protects us from deadly radiation of various kinds, including high-energy particles from the sun (as well as cosmic rays from outer space); if and when the magnetic poles flip, there may be a prolonged period of lower-than-normal field strength, and this, in turn, may allow dangerous radiation to blast our planet with increased intensity. This radiation could interfere with radio transmissions, damage satellites, and disrupt power grids; it can also boost cancer rates and perhaps lead to the extinction of species, though the science behind that last claim is much more controversial. As Mitchell admits, none of the scientists she spoke with “knows what the start of a [magnetic field] reversal looks like. There are theories. There is no consensus.” Nor, she adds, do we know what actually causes these reversals. One of the scientists says that a reversal “would be a leisurely process taking many hundreds or a few thousand years.”
Is the book overly alarmist? Perhaps it’s just alarmist enough. No, a flipping of the planet’s magnetic field is probably not imminent; nor, when it happens, is it likely to spell the end of life on Earth. But the more we understand about the physics at play beneath our feet, the better. If readers gain some insights into a field of science that’s rarely in the spotlight, and learn some interesting history along the way, then Mitchell’s entertaining book is most welcome.