An Ocean of Air

by Gabrielle Walker

  He wasn't surprised. The day after Sputnik was launched, he had written a series of comments in his field notebook, under the previous night's jottings. "Brilliant achievement!" was the first, followed swiftly by "?? Where do we stand now on Vanguard?"

  Hastily he wired back his assent. Yes, the instruments could be transferred to the Jet Propulsion Laboratory with his very good will, to be readied for a launch in the spring. The Glacier had almost completed its mission now, and by early November was steaming into Lyttleton Harbor, New Zealand. Van Allen gathered his bags and hurried home to Iowa.

  Van Allen had been delighted when the job came up at the University of Iowa. He had been born and raised in the state and was happy to go back after his stint in the East, at Johns Hopkins. His wife, Abigail, hadn't been so sure. She was an easterner; he'd met her in Baltimore—bumped into her quite literally while he was driving one day to his lab. (It was at a stop sign. The damage to the cars was minor, but the effect on the drivers was rather longer-lasting, since they got married six months later.)

  Abigail had been west of the Mississippi only once, and was convinced that she might as well go to the moon as far as culture was concerned. The family had arrived on a frigid New Year's Day seven years earlier in an old station wagon, pulling an even older trailer. Van Allen himself admitted that their first tiny apartment there "presented a challenging problem in heat transfer." But things were better now. The family was settled, Abigail was happy, and the work had been going well even before the satellite world had heated up so dramatically.

  Trained as a physicist, Van Allen had been a naval officer during the war, but it was afterward, with the chance to experiment with captured German V-2 rockets, that his scientific sights soared. From then on, he could only look up, to the outermost reaches of Earth's air. He wanted to know what filled these tenuous threads. Perhaps there were particles from outer space that pinged periodically onto the planet's outer skin—messages, as it were, from the cosmos. Of late, at the University of Iowa, Van Allen had been pioneering an instrument that he dubbed a "rockoon," in which a balloon lifted a rocket up some 50,000 feet before the rocket fired and shot up another 200,000. By this means in 1953 he had discovered negatively charged particles, electrons, in the sky and wondered whether they had something to do with making the auroras.

  But the satellite was the most exciting scientific prospect he had ever encountered. He had designed an instrument that would ride as high as humans could imagine reaching; it would bear a simple Geiger counter, an instrument for measuring radioactivity. Cosmic rays were simply a form of radioactivity, and Van Allen's Geiger counter would be able to fly through them, crackling as it encountered each one and telling him something about their history. And now it was to fly, under the guise of the army Jupiter C program, which had been renamed Explorer I. That was perfect. Because Sputnik (Russian for "satellite") had simply flown. Explorer I, however, would explore.

  On the morning of Friday, January 31, at Cape Canaveral, the countdown began. Launch would be at 10:30 that evening. All went almost embarrassingly smoothly. At 9:45 P.M. somebody noticed a leak in the rocket's tail, but fixing it delayed the flight by only fifteen minutes or so. At 10:48 P.M., the Jupiter C rose on its haunches and launched itself into the sky.

  There were four stages to this behemoth: the first, a liquid-fueled rocket for propulsion; the second, a cluster of eleven motors; the third, three more motors; and the final stage, a single motor, and the home of the clinging payload. As they watched each stage ignite in its chosen succession, the engineers noticed that stage four looked a little fast. The satellite had certainly gone somewhere, but they didn't yet know where. True, it hadn't crashed back to the ground, but it might have been thrown like a slingshot to another ignominious patch of earth. Until someone received its signal, no one would know if it had worked.

  Van Allen had calculated when he should expect the news. One full orbit ought to take ninety minutes. The satellite should then be beeping over northern Mexico, where plenty of stations from Southern California would pick it up. If, that is, it was there. For the next hour he stood with the other nervous guests of the Pentagon War Room, which was now the satellite's center for communications. A few amateur sightings trickled in, none of them especially credible. More coffee, more waiting. Another half hour passed, and now even desultory attempts at conversation had ceased. The expressions were stricken, the mood was disappointed and dazed. Then the telephone rang. Almost two hours after launch, news had arrived from professional radio stations in Earthquake Valley, California, with these magical words: "Goldstone has the bird."

  The room exploded with elation. Van Allen, von Braun, and the Jet Propulsion Laboratory's director, William Pickering, were immediately taken by army car to the National Academy of Sciences and smuggled in through the back door to make their report. Then came the press conference. Van Allen was amazed to find that the room was packed, even though it was now 1:30 in the morning. He later described the meeting as "spirited." Pictures of the three men, Van Allen, Pickering, and von Braun, brandishing a full-scale model of Explorer I above their heads, were soon beamed around the world. The two rocket men could scarcely contain their smiles. Van Allen looks quietly pleased, if perhaps a little tired.

  In the days that followed, there was scarcely time to analyze the trickle of numbers coming in from Explorer I. There did seem something odd about them, though. Some of the time, the Geiger counter aboard was picking up the odd cosmic ray blips, just the numbers you might expect. But once in a while the number dropped to zero, as if the machine were periodically malfunctioning. The trouble was, the method for beaming the numbers back wasn't working very well, and they couldn't get a continuous orbit.

  Explorer II should have been better, but unfortunately she expired on the launch pad thanks to a faulty fourth stage on the rocket. But Explorer III was up in no time, on March 26, 1958, and confirmed what Van Allen was beginning to suspect. Either something was wrong with his instrument, or something was very strange about the sky.

  Shortly after the launch of Explorer III, Van Allen flew to Washington, D.C. A receiving station in San Diego had downloaded an entire orbit of measurements from the satellite as it zipped overhead. Van Allen wanted the numbers. He picked up the tape from the Vanguard data center on Pennsylvania Avenue and took it back to his hotel. Until 3:00 in the morning he worked, making calculations with his slide rule and plotting the results on a piece of graph paper with ruler and pen.

  As he studied the graph, Van Allen realized why the Explorer I data had been so erratic: They had been receiving readouts from different bits of the cycle. But even though he now had the entire record laid out in front of him, it was still baffling. At low altitudes, the Geiger counter registered a modest fifteen to twenty hits per second, just what you'd anticipate for impinging cosmic rays—judging from his previous experiments with the highest-altitude rocket balloons. But then the instrument flatlined. It was as if the higher up you got, the fewer cosmic rays you saw. That simply didn't make sense.

  Van Allen packed up his results and went to bed. The next day, he went straight into the office and brandished his graph at two of his colleagues, Ernie Ray and Carl McIlwain. What, he wanted to know, did they make of that?

  McIlwain, too, had been busy. He had spent the previous day testing the prototype Geiger counter, and he had momentous news. Of course the machine would flatline if it had no signal. But it would also flatline if it had too much signal. It would saturate at a count of 25,000 hits per second. The other two stared at him. That meant the intensity was ten thousand times what they had expected.

  "My God," said Ray. "Space is radioactive."

  And not just any old space, but the stuff on the fringes of our own atmosphere, right above our heads. It was as if they had just discovered a mushroom cloud perpetually menacing us all from on high.

  But if that was true, why don't we all fry? The explanation was already there, it turned out. A young scientist
had proposed it in Norway more than sixty years earlier, though few outside the country had believed him.

  FEBRUARY 6, 1903

  THE FESTIVAL HALL

  ROYAL FREDERIK UNIVERSITY, KRISTIANIA, NORWAY

  The university's most ornate room was always an impressive sight: all Corinthian pillars, marble arches, and polished wooden floors. But tonight, an unusually distinguished audience graced its long curving benches. Under the bright chandeliers, the cream of society in Kristiania (as Oslo was then known) was murmuring expectantly. There were industrialists, men from the worlds of banking, shipping, and mining. The Minister of Defense was there. Indeed there was a particularly military flavor to the crowd, with the head of the Norwegian army also in attendance, not to mention various commanders in chief and the more martially minded members of Parliament; right at the front were representatives of Armstrong and Krupp, one of Europe's biggest weapons forgers. There was also a smattering of university professors, and assorted Kristiania intelligentsia. Many of the men's wives had come, too, for this was a cold night in the middle of Norway's interminable winter, and to citizens tired of the musical recitals, theatrical plays, and the odd'séance that were the town's only other diversions, it promised to be an entertaining evening.

  Kristian Birkeland was standing at the apex of the hall, the point toward which all the curved benches focused their attention. A slight, pleasant-looking man, he was wearing round wire-rim glasses, his ears perhaps a little larger than he would have liked, their size only accentuated by the thinning wisps of hair that clung to his temples. At least some hair remained there. Though he was still a young man, much to his chagrin, the crown of his head had been bald as an egg for years. He was immaculately dressed, as always: long black frock coat, waistcoat, snowy shirt, well-shined shoes, and black bow tie.

  Birkeland waited for the crowd to settle down. He loved giving demonstrations and his talent for them, coupled with his evident ability in physics, had induced his alma mater, the Royal Frederik University, to take him on as a lecturer. Now, at the age of thirty-six, he had been a full professor for five years, though appointees to this illustrious position usually had to wait until they were fifty or older.

  That's one reason he had managed to persuade the university authorities to let him use their precious banqueting hall for what was really a private enterprise. For the assembled industrialists and military experts were here not to be impressed by developments in physics, but to see Birkeland's latest invention—and more importantly, to decide whether it merited their investment.

  The demonstration would require a vast amount of electricity, which meant an equally vast generator. There was no room for this gargantuan machine in the hall, and besides, it didn't really look the part, so Birkeland had installed it outside in the university gardens. But its cables fed to the real star of the show: a brand-new "electromagnetic cannon."

  The gun took center stage. Its barrel had a bore of more than two inches, but the mysterious windings of copper coils that encircled it made it seem much larger. More impressive still, it was a full twelve feet long, robustly bolted to a large white frame. Inside the barrel, a hefty iron "bullet" weighing some twenty pounds was poised ready to strike its target—a solid plank of wood five inches thick. Trial runs had gone well; a flick of the switch and the projectile had repeatedly zoomed out of the barrel and slammed into the bull's-eye.

  The technology behind the gun was close to Birkeland's heart. He was fascinated by the burgeoning new science of electromagnetism. Earlier in his career he had studied in Paris with Henri Poincaré, one of the world's most famous scientists. And there, he had come across a set of extraordinary equations.

  These were the same equations that had inspired Heinrich Hertz, and were even now electrifying Oliver Heaviside over in his rural English retreat. Back in 1873, when Birkeland was only six years old, Scottish scientist James Clerk Maxwell had produced a set of fundamental laws for how electricity and magnetism were entangled. He had put together all the discoveries about these two forces that had been trickling out over the previous decades. Electricity, it seemed, somehow affected magnets: If you hold a compass near a wire that is conducting electricity, the compass needle will lurch. The opposite also holds true: Take a simple piece of copper wire and move it past a magnet and an electric current will immediately begin to flow through the wire, even when there's no battery or power source in sight. Electric fields somehow beget magnetic ones and vice versa, and this is what Maxwell's equations had captured.

  The relationships embedded in Maxwell's equations also meant that electric and magnetic fields could reproduce each other in endless serpentine waves. That's what electromagnetic waves like light and radio waves were made of, all simply squeezed or stretched variants of the same interweaving fields.

  As well as advances in physics, the equations presaged plenty of inventions: Marconi's telegraph, Bell's telephone, and also electric dynamos and motors. Because another aspect of Maxwell's equations showed that if you put a conducting object in a magnetic field, the object would move.

  That's what had given Birkeland the idea for his cannon. What if, instead of using gunpowder, you could blast projectiles through the air with the power of electromagnetism? Surely that would be worth a fortune.

  The money was what he was really after. Though Birkeland was entertained by his technological tinkerings, he was engaging in them to fund his true but expensive passion. He had become riveted by the question of what causes the northern lights.

  Back in the 1890s, when he had begun his university research, Birkeland had been investigating a recently discovered phenomenon: cathode rays. These were invisible rays that streamed from a hot cathode into a vacuum, announcing their presence only when they hit the glass wall of the chamber, which had been coated with fluorescent paint and would glow a ghostly purple or green. (This is exactly the same principle used in televisions, before the flat-screen revolution. The normal bulky box of the "tube" contains a hot cathode, which pours invisible rays through an evacuated chamber to paint an image when they hit the inside of the screen.)

  When Birkeland started working on cathode rays, neither he nor anyone else knew exactly what they were. Like many of Maxwell and Hertz's electromagnetic waves, cathode rays were invisible and energetic. But in one crucial respect they were very different. Put a magnet near x-rays, or light, or wireless waves, and nothing happens. Their own inbuilt magnetic fields swamp anything the magnet can do, and the waves plough on undisturbed.

  But cathode rays are different. When Birkeland put one of his magnets anywhere near them, the cathode rays slewed around and headed for the magnet's poles. This gave him an idea. He coated a magnetic object with fluorescent paint and sent a beam of cathode rays heading straight for it. As he had anticipated, the invisible rays suddenly appeared, dancing in glowing sheets of light over the magnet's north and south poles. They looked a bit like the aurora borealis, the "northern lights."

  The phenomenon of sheets of ghostly green, red, and white curtains billowing over the poles had been known for centuries, and attempts at explaining these lights were as bizarre as they were numerous. But staring at his glowing magnet in the vacuum chamber of his lab, Birkeland became convinced that the truth was, if anything, even stranger. The sun was hurling beams of cathode rays in our direction. Earth's own magnetic field then captured these beams and directed them to the poles, where the air soaked them up and glowed with their energy.

  A year after Birkeland came up with this idea, in 1897, British scientist J. J. Thomson discovered something else important about cathode rays. They weren't rays at all, or at least not steadily moving waves. Instead they were streams of tiny negatively charged particles—what we now know as electrons.

  This would turn out to be most significant. Because if Birkeland was right, the sun was flinging electrons and perhaps other positively charged particles toward Earth. These charged particles are a form of something we have learned to fear: the menacing ra
diation also created in a nuclear explosion. Though he didn't know it, Birkeland's suggestion was about much more than what creates the auroras. His hunch would lead to the discovery of exactly how our atmosphere protects us from the radioactivity that fills the rest of space.

  Immediately, Birkeland had decided to set about trying to prove his hunch. However, what he had in mind would be very expensive: polar expeditions, new auroral stations, measurements, and a laboratory the likes of which King Frederik University had never seen. Even though Birkeland was already receiving a large share of the university's research budget, he would need much, much more. So he decided to turn to his own inventiveness to supply the missing funds.

  Birkeland enjoyed inventing things almost as much as he enjoyed figuring out physics. By the end of his life he would hold more than sixty patents for items as diverse as electric blankets, mechanical hearing aids, and a technique for hardening whale oil to make solid margarine. But of all Birkeland's inventions, he had the highest hopes for his electromagnetic cannon. Also in the Festival Hall was a certain Mr. Gunnar Knudsen, an engineer and member of Parliament who was one of the five partners in the Birkeland Firearms Company. Birkeland had written to Knudsen two years earlier, inviting him to join the company he was forming:

  I have just recently invented a device with which it seems possible to use electricity instead of gunpowder as a propellant ... Colonel Krag, who has witnessed my experiments, has proposed that a company be formed, consisting of a few men who will furnish capital to build a small gun according to my plans ... Naturally, it would mean playing a lottery, but the contribution would be comparatively small, while I believe the chances are good for significant gains.

  Knudsen knew and liked Birkeland, and had already supported some of his basic research. He replied good-naturedly: "I accept with pleasure your invitation to participate in your invention, and promise, even if the big lottery does not appear, to keep smiling." Under the circumstances, that was to be just as well.