Tracking Sputnick

Tracking Sputnik

Brilliant excerpt from Steven Johnson’s book “Where Good Ideas Come From“.

The cafeteria at the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, had long been a site of productive shoptalk between the physicists, technicians, mathematicians, and proto-hackers who worked there. But the Monday lunchtime chatter on October 7, 1957, was unusually heated, thanks to the weekend headlines announcing the Soviet launch of Sputnik 1, the first man-made earth-orbiting satellite. Two young physicists, William Guier and George Weiffenbach, found themselves in a spirited discussion about the microwave signals that would likely be emanating from Sputnik. After canvassing some of their colleagues, it appeared that no one had bothered to come in over the weekend to see if Sputnik ’s signals could be picked up by the APL’s equipment. Weiffenbach, as it turned out, was in the middle of a Ph.D. on microwave spectroscopy and had a 20 MHz receiver sitting in his office.

Guier and Weiffenbach spent the afternoon hunched over the receiver, listening for Sputnik’s audio fingerprint. To combat the doubters, who would inevitably question whether the whole launch was an elaborate hoax, a product of communist propaganda, the Soviets had engineered Sputnik so that it would transmit an unusually accessible signal: an unbroken tone broadcast within 1 kHz of 20 MHz. By the end of the afternoon, Weiffenbach and Guier had a clear lock on it. The sound itself was a staccato pulse of electronic bleeps, but the context transformed it into the most marvelous music the two men had ever heard. It seemed unbelievable: sitting in a room in suburban Maryland, listening to man-made signals coming from space. Word began to spread through the APL that the young physicists had captured Sputnik’s signal, and a steady stream of visitors appeared at Weiffenbach’s door to eavesdrop on the satellite’s warble.

Realizing that they were listening to history, Guier and Weiffenbach hooked up the receiver to an audio amplifier and began recording the signal on audiotape. They included time stamps with each recording. As they listened and recorded, the two men realized that they could use the Doppler effect to calculate the speed at which the satellite was moving through space. First observed more than a century before by the Austrian physicist Christian Doppler, the Doppler effect describes the predictable way a waveform’s frequency changes when the source or the receiver is in motion. Imagine a speaker playing a single note, let’s say the A above middle C, which sends out sound waves with a frequency of 440 Hz. If you mount the speaker on the hood of a car and have it driven toward you, the waves stack up on top of each other, making the interval between each of them shorter. When those compressed waves arrive in your eardrum, their perceived frequency is higher than 440 Hz. When the car backs up, the Doppler effect reverses, and the perceived note drops below A. You can hear the Doppler effect at work every time an ambulance drives past you with blaring sirens; as it passes you by, the sound of its siren appears to slide down in pitch.

The Doppler effect has proved to be a remarkably versatile concept: it has been used to detect the expansion of the universe, to track thunderstorms, and to perform ultrasounds. Because Sputnik was emitting a signal at a steady frequency, and because the microwave receiver was stationary, Guier and Weiffenbach realized that they could calculate the movement of the satellite based on the small but steady changes in the waveform they were capturing. Late that night, they remembered an additional mathematical trick: by analyzing the slope of the Doppler shift, they could determine the point in Sputnik’s orbit that was closest to the APL laboratories. Almost by accident, they had hit upon a technique not just for calculating the satellite’s speed, but for actually mapping the trajectory of its orbit. In a matter of hours, the two young scientists had gone from listening to measuring to tracking the Russian satellite.

Over the subsequent weeks, a loose network of scientists at APL coalesced around Guier and Weiffenbach’s hunch, filling in details, researching the theoretical literature on orbiting bodies, and proposing technology improvements. Eventually, the APL’s director approved funds to run the numbers on the lab’s new UNIVAC computer. Within a few months of that first transmission, they had a complete description of Sputnik’s orbit, inferred entirely from that simple 20 MHz signal. Guier and Weiffenbach had embarked on a quest that would define their professional careers, the “adventure of their lives,” as they later called it. In the spring of 1958, Frank T. McClure, the legendary deputy director of the Applied Physics Laboratory, called Guier and Weiffenbach into his office. McLure had a confidential question to ask the men: If you could use the known location of a receiver on the ground to calculate the location of a satellite, McClure asked, could you reverse the problem? Could you calculate the location of a receiver on the ground if you knew the exact orbit of the satellite? Guier and Weiffenbach ran the logic through their heads for a few minutes, and then answered in the affirmative. In fact, deducing the location from a known orbit—instead of a stationary ground position—would make the results significantly more accurate. Without explaining his ultimate interest in the question, McClure told the two men to run a quick feasibility analysis. After a few furious days of crunching the numbers, Guier and Weiffenbach reported back: the “inverse problem,” as they called it, was eminently solvable.

Soon, Guier and Weiffenbach would learn why the inverse problem was so important to McClure: the military was developing its Polaris nuclear missiles, designed to be launched from submarines. Calculating accurate trajectories for a missile attack required precise knowledge of the launch site’s location. This was easy enough to determine on land—say, for a missile silo in Alaska—but it was fiendishly difficult in the case of a submarine floating somewhere in the Pacific Ocean. McClure’s idea was to take the ingenious Sputnik solution and flip it on its head. The military would establish the unknown location of its submarines by tracking the known location of satellites orbiting above the earth. Just as sailors had used the stars to navigate for thousands of years, the military would steer its ships using the artificial stars of satellite technology.

The project was dubbed the Transit system. Just three years after Sputnik’s launch, there were five U.S. satellites in orbit, providing navigational data to the military. When Korean Air Lines Flight 007 was shot down in 1983 after drifting into Soviet airspace thanks to faulty, ground-based navigation beacons, Ronald Reagan declared that satellite-based navigation should be a “common good” open to civilian use. Around that time, the system took on its current name: Global Positioning System, or GPS. Half a century later, roughly thirty GPS satellites blanket the earth with navigational signals, providing guidance for everything from mobile phones to digital cameras to Airbus A380s.

If you wish to see firsthand the unpredictable power of an emergent platform, you need only look at what has happened to GPS over the past five years. The engineers that built the system—starting with Guier and Weiffenbach—created an entire ecosystem of unexpected utility. Frank McClure recognized that you could harness Guier and Weiffenbach’s original insight to track nuclear submarines, but he had no inkling that fifty years later the same system would help teenagers to play elaborate games in urban centers, or climbers to explore treacherous mountain ranges, or photographers to upload their photos to Flickr maps. Like the Internet itself, GPS has turned out to have immense commercial value, and many for-profit firms were involved in building out the infrastructure that made it a reality. But the ideas at the foundation of GPS—the notion of a satellite itself, the atomic clocks satellites rely on for accurate timing, and, of course, Guier and Weiffenbach’s original insight with Sputnik—all came out of the public sector. The generative nature of the GPS platform nicely mirrors the original environment that gave birth to it. When Guier and Weiffenbach were asked to explain how they had hit upon their Sputnik revelation, they credited the intellectual habitat of the Applied Physics Lab more than their own particular talents:

APL was a superb environment for inquisitive young kids, and particularly so in the Research Center. It was an environment that encouraged people to think broadly and generally about task problems, and one in which inquisitive kids felt free to follow their curiosity. Equally important, it was an environment wherein kids, with an initial success, could turn to colleagues who were broadly expert in relevant fields, and particularly because of the genius of the Laboratory Directorship, colleagues who were also knowledgeable about hardware, weapons, and weapons needs.

In its own small way, the APL was a platform that encouraged and amplified hunches, that allowed those hunches to be connected with other minds that had relevant expertise. Out of that dense network, one of the most generative technological platforms of the twenty-first century took root. The APL was not a purely open platform, of course. There were military secrets involved, after all; and even if Guier and Weiffenbach had wanted to share their Sputnik discovery with the world, it was much harder to distribute that breakthrough in an age when the hot new computer—the UNIVAC—took up an entire room. But behind those closed doors, William Guier and George Weiffenbach were the beneficiaries of an environment that encouraged the chance collisions between different fields, an environment that let two “kids” stumble across an idea at the cafeteria and build an entire career around it.

Most hotbeds of innovation have similar physical spaces associated with them: the Homebrew Computing Club in Silicon Valley; Freud’s Wednesday salon at 19 Berggasse; the eighteenth-century English coffeehouse. All these spaces were, in their own smaller-scale fashion, emergent platforms. Coffeehouse proprietors like Edward Lloyd or William Unwin were not trying to invent the modern publishing industry or the insurance business; they weren’t at all interested in fostering scientific advancement or political turmoil. They were just businessmen, trying to make enough sterling to feed their families, just like those beavers constructing lodges to keep their offspring safe. But the spaces Lloyd and Unwin built turned out to have these unusual properties: they made people think differently, because they created an environment where different kinds of thoughts could productively collide and recombine.

Or, you can listen to Steven Johnson tell the story at TED:

You Might Also Like