The tubes also served as a milestone on the way to the invention of the neon sign, in 1910, and decades after that, the Nixie. Scientists used Geissler tubes to understand the nature of electricity, and they were sold as decorative curiosities. Applying a direct current of a few thousand volts ionized the gas and caused it to emit light. Air was evacuated from the bulb, which was then filled with neon, argon, or some other gas some tubes were filled with conducting fluids, minerals, or metals. The tube consisted of a simple glass bulb with an electric terminal on each end.

The earliest application of gas discharge was the Geissler tube, invented by the German physicist Heinrich Geissler in 1857. The color of the light depends on the gas: Neon ions emit a red-orange light hydrogen emits bluish purple nitrogen gives a spectacular purple and krypton glows whitish blue. The same basic process produces the glow of neon signs and the northern and southern lights. The ions, excited to higher energy states, shed the excess energy as photons of light. The speeding particles collide with the gas atoms or molecules, ionizing them and creating an energetic plasma of charged ions and electrons. This phenomenon occurs when electrically charged particles, typically electrons, move through a gas at a high velocity-roughly 2 percent of the speed of light. Nixie tubes operate through a process called gas discharge. It was also the culmination of a long line of breakthroughs. But if you think about what was technologically possible in the middle of the 20th century, you soon realize it was the most logical and reliable option available. The Nixie tube may seem like an unnecessarily complicated invention for something as straightforward as displaying a number. It's a classic story of 20th-century innovation, complete with a quirky genius, shrewd corporate maneuvering, and brilliant flashes of insight. But some glimmers, at least, of its enduring appeal emerge from the tubes' colorful history. We may never fully understand why this quirky technology, out of innumerable others, has been plucked from obsolescent obscurity. Nearly two decades later, the movement is still going strong, and Nixies now inhabit a unique niche as ultracool retro tech aimed at discriminating consumers. But their extraordinary resurgence didn't really begin until around 2000, when a small but devoted cadre of hobbyists, collectors, and aficionados began searching out and buying old, never-used tubes and designing clocks around them. Some Nixies lingered on in legacy equipment, of course. The tubes might have died the lonely death of countless other obsolete devices-and yet they did not. In the 1970s, Nixies were eclipsed by LEDs, which were not only much cheaper to make and use but also more versatile. Remarkably, it continues to do so, even for people who, like Farny, grew up long after the tubes had faded from common use. For many people, the warm glow of the Nixie came to evoke an era of unprecedented scientific and engineering achievement, of exciting and tangible discoveries, and of seemingly limitless progress.

Born in the basement of a German-American tinkerer in the 1930s and later commercialized by the business equipment maker Burroughs Corp., Nixies displayed data vital to NASA's landing on the moon, lit up critical metrics for controlling nuclear power plants, and indicated the rise and fall of share prices on Wall Street stock exchanges, among thousands of uses. These neon-filled glow lamps were ubiquitous in the late 1950s and 1960s, illuminating numbers, letters, and symbols in scientific and industrial instrumentation. In 2012, Farny began working to revive the manufacture of a display technology called the Nixie tube, the last commercial examples of which were produced when he was still a child. Carefully, almost lovingly, he unloads crate after crate of heavy equipment and supplies-an industrial glass lathe, a turbomolecular vacuum pump, and glass. He puts on some heavy gloves, steps out of the truck, and opens the back hatch. On a cold December morning in the Czech village of Březolupy, a man stops his truck in front of a 17th-century castle.

Nixie clock