Light 12: Neon

Welcome to the 2023 Advent Calendar, which this year is just a list of things that light up all pretty. Previous entries are here. If you enjoy this and want to encourage me to bang more things out on a keyboard, consider supporting my Patreon, or sending something off of my Christmas list. If you'd rather support my spoiled pets, their Ratmas list is here. If you want to spend money but not on me, you can direct your donations to Mainely Rat Rescue, who handles rescue and foster operations for rats, mice, gerbils, guinea pigs, and other small mammals in the New England area, or the MSPCA, where my critters got their medical care before I found a good exotics vet, and where I picked up Koda and Yogi. 

Enjoy your trip through the cavalcade of things that go blinky-blink in the dark!

Few things are as attention-getting as a neon sign. "Neon" like the element, a noble gas that was found to emit a vibrant orange light under current, the lights actually employ a number of different gases and gas mixtures to get the different colors. Hydrogen is used  for purple and carbon dioxide for bright white, and even helium can give either yellow or a rather charming pink, depending on the exact setup. 

Fluorescent bulbs are just neon lights with one extra step: An electrical current prompts mercury to emit a light so brightly blue it ventures into the ultraviolet, which in turn prompts a phosphor coating on the interior of the bulb glass to glow... well, that sickly industrial greenish-white we all know and loathe. Later coating formulations used in compact fluorescent bulbs cast less terrible colors, but there's still a reason I never turn on the ceiling fixture in my bedroom.

The main draw of neon lamps is the relative weakness of the interior vacuum. Incandescent bulbs require as near to hard vacuum as you can manage, for the longevity of the filament, but neon bulbs only have to be between about 3 and 20 Torr. This means the lamp glass can be blown into virtually any shape -- tubes became popular for their ability to be bent into legible words, but you can make neon lamps in any form you like, as long as it keeps the gas inside. The first working gas discharge tubes were demonstrated by Georges Claude at the 1910 Paris Motor Show, and they looked pretty much exactly like a neon tube today. They were an immediate hit, which was fortunate for Claude, as he happened to have a huge amount of neon lying around as a byproduct of his main business, liquefying air.

Neon lamps in tube and bulb form have served a number of practical purposes, from signage to illuminating electronic displays before LEDs were a thing. They are also used in a lot of interesting art. Boston has a series of long-term arts installations in the stations of the Red Line Extension. Some are wall murals, some sculpture, and some actually poetry etched into the brick floors of the platform. One of the piece at Alewife is "The End of the Red Line", several hundred red neon tubes suspended delicately above one of the tracks, swaying gently with the arrival and departure of the trains.