Numbers In A Bottle

A nixie tube clock.

The Fifties were painted with neon. Motel entrances to theater marquees to diner windows crackled with bright lettering and logos and pictograms in pink and gold and ruby and apple-green.

If the outdoors were bathed in a polychromatic fizzy halo, then the electronics of that era, from voltmeters to desk calculators, were lit with the pleasing orange of the nixie tube.

A seven-segment display.
A seven-segment display.

Today, be it the pedometer or the thermometer or the clock on the cable-box, numeric messages are created by slim panels that display numbers, by illuminating different combinations of segments on what’s known as a “seven-segment display,” a roughly rectangular grid, composed of seven glyphs.

But back in the 1950s and 1960s, they were conveyed by solid numerals, made of metal.

The nixie tube is a sealed glass bulb that has a stack of wire digits—0 to 9—placed one in front of the other. Each is a cathode (a negative terminal.) Wrapped around the bunch is a wire-mesh, which is an anode (a positive terminal.) The bottle is filled with a pocket of neon.

A nixie tube.
A nixie tube.

This component, unlike a standard light bulb or a neon lamp, doesn’t produce light as a byproduct of heat.

Its cathodes remain relatively cool, rarely exceeding 104 Fahrenheit. Which is why, such a tube is described as a “cold cathode,” even though it’s mildly warm.

When a stream of electricity is passed through the circuit, the gas—kept at a very low pressure, at one-hundredth of normal atmospheric pressure—turns into plasma (a mixture of positively charged ions and negatively charged electrons.)

The electrons dash to the anode. The ions race to the cathode. The glow is a result of an atomic mêlée in which neutral, non-charged atoms absorb energy, and then release it as photons.

In the 1970s, the graceful nixie tubes were eclipsed by lackluster successors.


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