Alanna Mitchell - The Spinning Magnet: The Electromagnetic Force That Created the Modern World--And Could Destroy It

Night had set in by the time the green lights started dancing in the skies. I was in a canvas tent, trying to sleep in the bone-chilling cold of the late Arctic summer, worried about hungry polar bears. The cries of my fellow travelers roused me and I cursed, pulling on snow pants, boots, and a warm jacket before facing the night air.

The aurora borealis, or northern lights, were coursing through the black heavens, pulse after pulse of neon green against the scatter of stars, so near it was as if the curtain of light embraced us. They would fade away. We would hold our breath. And then back they would swoop, suffusing the sky. The heavens writhed with the otherworldly green rays, on and on, as if they held sway not just over our planet but over time too.

Watching those neon northern lights, I was closer than I knew to some of those who shared my impulse to understand the planets magnetic force. My camping spot was on King William Island in the Canadian Arctic, about 100 miles or so from the Boothia Peninsula, where the British explorer James Clark Ross first pinpointed the Earths magnetic north pole in 1831. His discovery of it was part of the magnetic crusade, the most sustained and impassioned scientific campaign the world had seen until then. At that time, the might of nations depended on naval prowess and efficient trade on the seas. And that depended on the magnetic compass. There was a trick to seafaring navigation, though. Knowing where you were depended on being able to adjust for the difference between magnetic north, where the compass pointed, and geographical north. The scientific world was united in an obsessive effort to figure out a formula that would allow sailors to know their coordinates more exactly. That required understanding the strange force that pulled the compass. And that demanded information from the top and bottom of the Earth, where the force showed itself most strongly.

King William Island itself resonates with a grisly piece of the magnetic quest. It is where the British explorer Sir John Franklin vanished in the 1840s along with his 128 men and their two ships. They were trying to complete the Northwest Passage, the quick sea route over the top of North America that would connect the wares of the Orient with the markets of Europe. But Franklin was also a player in the magnetic crusade. The ships in his Arctic adventure, HMS Erebus and HMS Terror, carried enough equipment to set up a state-of-the-art magnetic observatory in the Arctic, one of dozens that were being established all over the world as scientists tried to decode the secrets of the magnet. Franklin himself orchestrated the setting up of a magnetic observatory on the island we now know as Tasmania, off the Australian mainlands south coast.

But when his Arctic ships got stuck in the ice and Franklin died, along with many of his men, the survivors abandoned ship and took to the frozen island in their leather-soled shoes and navy cloth greatcoats in a bid to walk to safety with the Earths magnetic field as their trusted guide. Some resorted to cannibalism. All died. Few of their skeletons have been recovered. It was the worst disaster to hit Arctic exploration. The Inuit who live on King William Island say the sailors ghosts haunt the place still. Among the relics recovered from the sailors doomed march was a brass pocket compass, currently in the collection of the National Maritime Museum in Greenwich, England. The men were trying to read their magnetic position even in those grim final days. It was their last hope to get home.

Franklin, Ross, and other Victorian explorers, stuck for years on end in the Arctic, undoubtedly saw the northern lights. But they could not have known how the compass, the magnetic poles, and the auroras fit together. Today, we know that they are facets of one another. The Earth is a giant magnet with its own two poles, north and south. Stretchy magnetic field lines leave the surface of the Earth at the south magnetic pole; run around the planet, where they interact with the magnetic fields of the sun and the galaxy; and then reenter the Earth at the north magnetic pole in unending, erratic loops.

Our magnetic field is generated in the Earths most secret inner reachesits hot, yet frozen, metal inner core surrounded by a liquid metallic outer core. That heat, a remnant of the planets violent birth, is the secret to the planets magnetic power. The core has been on a multibillion-year quest to get rid of that heat from the inside out and is shedding it through convection. Convection generates electrical currents in the molten metal of the part of the core that is not yet solid, and those currents produce a magnetic field. Phoenix-like, that field is continually being created and destroyed. It stretches out for thousands of miles into space, our planets giant defense system against the lethal invisible rays and charged subatomic bits that would otherwise rip through living tissue and tear away the Earths atmosphere. Consider that our sister planet, Mars, lost its atmosphere, water, and likely any life forms when its internal magnetic field died billions of years ago.

A compass, with its magnetized needle, is responding to the Earths magnetic field. And the auroras? To humans, the magnetic field is invisible and imperceptible. We see the