An Ocean of Air

by Gabrielle Walker

  Birkeland was delighted with the spectacle. He wrote: "It will be easily understood that in addition to the purely scientific reasons for doing this, I have also a secondary object, which is to give myself the pleasure of seeing all these important experiments in the most brilliant form that is possible for me to give."

  From time to time Birkeland squeezed an audience into his lab to show off his artificial auroras, and few failed to be amazed. Here was a man who could make the northern and southern lights dance at will. What's more, he could explain why they appeared. And his experiments matched his theory with a faithfulness that was thrilling.

  Still, just because the lights dancing over Birkeland's terrellas looked like the auroras, that didn't necessarily mean he was right. To many, the notion of radioactive beams from space was absurd. Birkeland had to prove that what happened inside his vacuum chamber was also taking place out in the real world.

  He needed to show that when spots appeared on the sun, electric currents appeared in the northern skies along with the auroras. He couldn't measure the currents directly, since they would be too high up. But he could perhaps detect their influence on the magnetic field around them. So, Birkeland packed up his instruments and went north.

  For someone who was slight and relatively frail, Birkeland approached his polar expeditions with a zest that was almost reckless. Of course, he needed to be in the auroral zone, which meant the farthest north of Norway's provinces. Also, he had to go in winter—which, with its long, dark nights, was the best time to study auroras. But to make matters even harder, he had also decided to study his auroras from the top of a high mountain.

  One reason was to be as close to the lights as humanly possible. Indeed, some theories held that auroras came from electricity that leaked out of Earth via the point of a mountain, like an inverse lightning rod; even if, like Birkeland, you didn't believe this, there were many who thought that in northern Norway auroras came down so low that they touched the mountaintops themselves. True, this was because of rumors and legends rather than scientific data, though there was also the occasional eyewitness report. Some of the "close encounters" were described with amazing detail and poetry. This is from a boat trip at Talvik in Finnmark, as late as 1881:

  Immediately after nightfall the northern lights began to flame merrily in the sky. They gathered like a huge fire in the deep-blue vault of the heaven, and great pencils of rays, mauve, blue and green, united and danced in flaming witches' knots above the boat. We had just about reached the middle of Korsfjord when I suddenly noticed an aurora above Alta that had knotted itself right down on the surface of the water and was rushing across the fjord at high speed..."It will overturn the boat" shouted Jakob from the thwarts. And in the darkness I could see the men bend their backs and heave on the oars so that the phosphorescence shone about the blades ... I shut my eyes for an instant. When I looked around a moment later with the light penetrating my eyelids, I found we were in the midst of such a fantastic sea of light as I shall never forget. Flames of wonderful transparent color surrounded us, violet, blue and green, but without the slightest breath of wind ... That rare but lovely play of light passed us by in a few seconds. A moment later it was gone.

  Even if—as Birkeland suspected—these reports were spurious and the aurora didn't touch the ground, the chance of being engulfed by an aurora was irresistible, and a mountaintop seemed the surest way of trying. In February 1897, Birkeland headed off with two assistants to Finnmark, in the far north of Norway, on a reconnaissance trip, to seek out suitable mountain sites.

  At first, all went well. There was scarcely any daylight so far north at this time of year, but the moon shone brilliantly on the mountains' thick blanket of snow, lighting the way for the strings of reindeer that pulled Birkeland's team and equipment up the slopes. On February 9, the wind picked up a little, blowing the snow crystals along the ground like trails of smoke. But it was nothing much to be alarmed about, even if the temperature was a chilly –13 degrees Fahrenheit. There were only another sixteen kilometers to go to reach their destination, Lodikken Hut.

  However, as they pressed on with their Finnmark guide the wind grew stronger, always in their faces, blowing, it seemed, directly from the hut they were trying to reach. Birkeland began to be alarmed. The small team struggled on. They were no longer splendidly skimming over the snow in their sleighs. Their guide was now forced to lead the reluctant reindeer, and anyone foolish enough to sit in the sleigh would have been pelted with stones and shards of ice that had been whipped up by the wind.

  Eventually the reindeer lay down and refused to go farther, and the guide, his face now white with frostbite, climbed under his Finnish furs and similarly refused to budge. Nothing remained but to use the baggage and sleighs to build a barricade against the wind and then pitch a small tent behind it. This was supposed to be a trip of only a few hours, so aside from the emergency tent the team had little in the way of supplies—no food or fuel to melt water, even if they could have lit a stove in this appalling wind. For the next twenty hours, throughout the long, dismal polar night, the small team huddled in their sleeping bags, trying to ignore their gnawing stomachs and keep their tent from being buried by snow. When dawn finally came, though the wind had scarcely abated and Birkeland could still not see more than a few yards ahead of him, he decided their only chance for survival was to try to find a route back down the mountain.

  Gradually, grudgingly, the guide stirred to help break the miniature camp and set up the reindeer. But then, when he had thawed out a little, he proved his worth. Birkeland recalled, "The couple of hours spent in the descent were the most exciting I have ever gone through. It was now that our guide showed himself to be the adept that I had been told he was. It was wonderful to see the way he ran to the right or to the left, to find tracks or take a course, and how he drilled the reindeer when they became unmanageable and suddenly set off up in the face of the wind again."

  Thanks to this wild ride, the team arrived safely back at Gargia, thirty-one hours after they had left. It was a miracle that nobody had died. However, one of Birkeland's young assistants, twenty-year-old Bjørn Helland-Hansen, was suffering badly from frostbite. His hands were white and stiff from the tips of his fingers all the way to his wrists. While the others soaked up the warmth and comfort of the mountain hut, poor Helland-Hansen had to sit with his hands in iced water, waiting for the circulation to return—and with it the inevitable burning agony. He later lost the top joints of most of his fingers, and with them, his dreams of becoming a surgeon.

  But one good thing came out of this disastrous expedition. At ten minutes to six on February 5, Birkeland had seen something that left him spellbound. The weather was clear, the moonlight shining brightly on the snow, and then, suddenly, an even brighter light appeared in an arc that curved across the sky from east to west. At first it was narrow and intense but then it draped into shimmering curtains, and bundles like sheaves of corn. Birkeland watched, awe-struck, as the heavenly light show played itself out for more than an hour.

  And then, the next night, the same thing happened. At just after 6:00, the aurora returned, and passed through exactly the same set of arcs, curtains, and sheaves. To Birkeland this was almost an omen. Earth's daily twirl around its axis brings it back repeatedly to face the sun. So if the aurora could appear so consistently two days in a row, at exactly the same time, it surely had to be caused by something coming from the sun. His hunch from 1896 had to be right.

  In autumn that same year, Birkeland returned to the mountains of Finnmark, determined to try again. This time, he found exactly what he was looking for in the district of Haldde, on the west side of the Alten Fjord. Atop two adjacent mountains Birkeland set about building stone and cement huts, the world's first permanent observatories for studying the auroras. He was inordinately proud of them:

  In clear weather everything that takes place in the sky can be observed, from the point where it begins to that where it leaves off. The view is u
ninterrupted, and from both observatories, but especially the highest and northernmost, there is a panorama stretching from the sharp, blue peaks of the Kvaenang mountains in the west, to the softer outlines of the Porsanger mountains in the east, and from the precipitous cliffs of Lang Fjord and Stjerne Island in the north to the mountain plateau in the south, stretching inland in undulating lines as far as the eye can see, in towards the winter home of the mountain Lapps. And far below lies the fjord like a dark channel.

  By September 1899 the huts were finally ready. Birkeland took two teams up the mountain, aiming to spend the entire winter. They would be there until April 1900, passing the first day of the new century in conditions that were sometimes benign, more often appalling. The winds were phenomenal, often raging at more than one hundred miles per hour. "It sometimes roared so against the houses, that you would have thought you were sitting at the foot of a waterfall; and the floors trembled and everything shook. We soon got to be able to gauge relatively the storm outside by the noise within." When the storms rose, nobody could leave the hut for days; if anyone did try, it took all three men, with great effort, to close the door. Inside the hut, even with the door closed, water would sometimes freeze a few yards from the glowing stove, and a lamp was once blown out while sitting on the table in the middle of the closed room. "No one," said Birkeland, "who has not tried it can imagine what it is to be out in such weather."

  One person who repeatedly found himself caught out by these storms was the sturdy Finnmark postman who arrived once or twice a week with news of the outside world. "We were often afraid for him," said Birkeland, "but he was always alright, though sometimes so covered with ice when he arrived, that he was quite unrecognizable. I once asked him if he were never frightened when the weather was so bad. At first he did not answer, but sat quietly down to thaw; but a little while after he said: 'I'm too stupid to be frightened.'"

  In spite of the storms, the expedition was a huge success. The team had seen aurora after spectacular aurora, and Birkeland's most precious instruments—his magnetometers—had exceeded all expectations.

  The magnetometers had a room of their own in the stone hut. Before Birkeland entered, he would empty his pockets of coins, pocketknives, or anything else that might disturb the delicate magnet at the heart of the instruments. Even the buttons on his clothes were made from bone, and his round glasses were rimmed with nonmagnetic gold. All magnetic metals had been similarly banished from the room. The door hinges were made of brass, the nails were of copper instead of iron, and the heating pipes were ceramic.

  Each of the three magnetometers was continuously monitoring a different aspect of Earth's magnetic field. One recorded which direction the field pointed in, another the horizontal strength, and the third the vertical. They were housed in large boxes, each with a hole cut in the side. Inside each, a magnet dangled on a fine quartz thread, which also bore a mirror. Lenses focused the light from an oil lamp into a fine beam that entered the box, reflected off the mirror, and then exited to strike a roll of photographic paper. If the magnetic field overhead changed in any way, the magnet would swing in response, taking the mirror with it, and the reflected light would be deflected. Even if nobody happened to be in the room when this took place, any deflections would show up clearly as soon as the photographic paper was developed.

  Throughout their long winter, almost every time the teams spotted an aurora overhead the mirrors on the magnetometers swung, and the line tracing their path lurched. Just as Birkeland had anticipated, he was marking the overhead passage of electric currents, the cathode rays streaming in from the sun.

  It also became clear as the winter went on that the lights came nowhere near the surface, even of such lofty mountaintops. In one way, that was a shame; the bright-eyed Birkeland would have enjoyed the experience of being immersed in his precious lights. But at least it meant that his next expeditions could be closer to sea level.

  For Birkeland already knew that there would be many more expeditions. The movements of the currents were obviously complex. To trace their sinuous pathways, Birkeland realized he would need measurements from sites that were much farther afield. So he decided to extend his operations. As well as in Norway, he would set up observatories in Iceland, Russia, and the frigid northern archipelago of Svalbard. Meanwhile, data began flooding in from observatories around the world, a response to a circular Birkeland had sent out asking for magnetograms to be sent from any available station on the globe.

  And as he mapped out his measurements and pieced together the jigsaw puzzle, everything Birkeland saw confirmed his suspicions. Sunspots coincided with beams of electrons that shot out of the sun like searchlights. Some missed Earth; most glanced off the closed magnetic field lines that curved over the bulk of the globe's surface. The rest were directed safely to the poles by our protective magnetic field. He couldn't see the electrons themselves, but he could trace their jangling influence as they spiraled down the magnetic field lines over the North Pole. Then they hit a short-circuit. (Though Birkeland didn't know it at the time, this was the ionosphere, which as well as fielding incoming x-rays provided a handy horizontal conduit for the incoming electrons.) As the electrons passed horizontally above in great arcing currents, they were gradually absorbed by atoms and molecules of air, and yes, the northern lights glowed. Finally, any electrons that remained finished the loop by attaching themselves to new field lines, and spiraling harmlessly back up them and out into space.

  Over the next decade, Birkeland collected more and more data in support of his theory. He published it in a grand opus, two handsomely bound volumes that made him, if anything, even more famous in his native land. He wrote: "The knowledge gained, since 1896, in radioactivity had favored the view to which I gave expression in that year, namely, that magnetic disturbances on earth and aurora borealis, are due to corpuscular rays emitted by the sun." And: "It must ... be considered as certain that the cosmic rays which come vertically towards the earth in such a way as to form auroral rays, are entirely absorbed by the atmosphere."

  This should have been the prime of Birkeland's life and the apex of his success. But as he progressed though his forties, his earlier youthful vigor and optimism somehow turned sour. Since his early days in Paris he had occasionally been subject to depression, "nervous freezing attacks" that would send him to his bed for days on end. He was now experiencing such attacks increasingly often; with them came paranoia, despair, and ever-faltering health. He was also frustrated that his theory was not getting the international recognition he was sure it deserved. Part of the problem was that he had written in French. Not only was he a fluent speaker, but French had long been Europe's premier language of culture and natural philosophy. But this was the turn of the twentieth century, when the British Empire was at its peak and English was becoming the new lingua franca.

  Moreover, English scientists were primed to look askance at Birkeland's ideas. Back in 1892 the great Lord Kelvin, one of Britain's most famous and distinguished physicists, had pronounced: "There is absolutely conclusive evidence against the supposition that terrestrial magnetic storms are due to magnetic actions of the sun; or to any kind of dynamical action taking place within the sun ... the supposed connection between magnetic storms and sunspots is unreal and the seeming argument between the periods has been mere coincidence."

  Kelvin's views held great sway, because he was almost invariably right. Except, as it turned out, in this case. Still, British scientists stuck to Kelvin's guns. Birkeland, always an insomniac, was now having more and more trouble sleeping. To find any rest at all he became increasingly reliant on veronal, a sleeping agent that had the particularly important attribute of not adding to his mounting struggles with depression.

  He went to Egypt and became convinced that he was being tracked by mysterious—and sinister—foreign agents. He decided to return home and cabled that he would be back in Norway in time for his fiftieth birthday, on December 13, 1917. The First World War was now underway, a
nd he had to take a circuitous route via Tokyo. On the morning of June 16, 1917, one of the Japanese physicists Birkeland had stopped to visit found him dead in his Tokyo hotel room. He had taken ten grams of veronal, instead of the prescribed half gram, and his heart had failed. It was perhaps an accident.

  In his lifetime, Birkeland had received four nominations for the Nobel prize in chemistry and four in physics. An illustrious committee of Norwegian scientists was putting together what they believed was the strongest nomination yet for the physics prize when news reached Norway of his death. The project was quietly shelved.

  Because of the war, nobody could come from Norway for the funeral. Instead, Birkeland's Japanese hosts presided over a Christian ceremony and cremation. At the service, one said, "What Birkeland has achieved in the fifty years of his life is as brilliant as the dazzling waves of the aurora, which have exerted such a mighty attraction on him."

  For decades after Birkeland's death, his theory remained in limbo. Even when the ionosphere was discovered and it should have been obvious that this was the conduit for Birkeland's currents to sweep over the sky, few scientists accepted his argument. Only in the 1960s was he finally vindicated. For this was now the space age, the time when satellites could penetrate the world that Birkeland had simulated and monitored, but could never touch. Satellites had discovered that space was radioactive. And they were also about to discover just how right Birkeland had always been.

  ***

  MAY 1, 1958

  James Van Allen was presenting his findings to the world. The patch of space hugging the top of our atmosphere was mysteriously radioactive. That's what Explorers I and III had clearly shown. He still wasn't exactly sure what this meant, or why it would prove to be important, but that hadn't prevented him from laying out the results to assembled scientists at the National Academy of Sciences. More difficult was explaining them to the journalists at the press conference that followed. Van Allen struggled to find the words. The radiation they had discovered seemed to congregate in a giant cloud, shaped like a doughnut with Earth occupying the hole in the middle. It was corpuscular radiation—that is, charged particles—girdling the planet in a giant, well ... something like..."Do you mean like a belt?" one reporter demanded. "Yes, like a belt," Van Allen replied. And thus the "Van Allen belt" was born.