Every other Friday, the Outside/In team at NHPR answers a listener question about the natural world. This week's question comes from Gretchen, who called in while thru-hiking the Appalachian Trail. She was wondering about the red light setting included on many headlamps.
“When did this become a standard thing on headlamps? And when did it become common etiquette to use that setting? Or . . . am I just in the thru-hiking bubble?
Producer Marina Henke looked into it.
Marina Henke: To figure out when headlamps started to use red light, you have to know when humans started to use headlamps. That story starts in a place darker than any hiking trail.
Eric Nystrom: The kind of profound darkness of some place underground is difficult to describe.
Marina Henke: This is Eric Nystrom, a history professor at University of Nevada, Reno. He’s talking about mines. That’s because miners were the first people to use headlamps. But these were way lower tech than what you might see today.
Eric Nystrom: Really you trace the first ones to candles.
Marina Henke: Candles! But since miners needed their hands to mine, those candles had to go somewhere.
Eric Nystrom: Some folks would take a dot of clay and sort of affix it to the crown of their hat.
Marina Henke: Except, this was dangerous because an open flame could cause a methane explosion. Or it could just go out.
Eric Nystrom: You know you think about what a flame on your head goes through when you move your head around. . . .There's wind, there's movement, there's jostling. And that flame is your light. And it might be your ability to get out of the mine.
Marina Henke: Needless to say, it was a big deal when a new technology came onto the scene: carbide lamps.
Eric Nystrom: Carbide is a manufactured product. It's discovered in the late 1890s and then pretty quickly they figured out that when it comes in contact with water it generates acetylene gas. Acetylene burns with a bright white flame.
Marina Henke: Carbide lamps took advantage of this reaction. Separated by two chambers, water would drip over dry carbide. Cue the acetylene gas, and then by strike of a flint: Presto! Light! This flame was about 10 times brighter than a singular candle.
Eric Nystrom: You can just imagine it's a revolution.
Marina Henke: But the revolution didn’t end there. With the development of batteries, electric headlamps entered the mining world in the 1930s. But the early models looked . . . well kind of like a Victorian torture device. And the batteries? Gigantic!
Eric Nystrom: You take one of those biographies of a president or something like that? It's the size of one of those things.
Marina Henke: So yeah, these early headlamps weren’t quite ready for your weekend hikes. But they did make their way into another pocket of outdoor recreation.
ARCHIVAL CLIP: Up in the alps, some cavers from Grenoble have beaten their previous record of minus 933 meters of their exploration of the Gouffre Berger.
Marina Henke: Caving. In 1973, as batteries were getting lighter and lighter, a caver named George Petzl had an idea. Could an elastic band carry the weight of both the bulb and the battery pack? Welcome, the Petzl headlamp. Petzl, by the way, is still one of the most popular brands of lighting gear today.
As these headlamps became popular among your weekend warriors of the 80s, red light was already pretty common in a different realm: the military. That’s because red light allows you to see in the dark without ruining your night vision.
Eric Nystrom: You see in the First World War — and really certainly by the Second World War — the development of flashlights that have a replaceable lens cover. This is so that you can filter your light if you wanted to have it temporarily useful for night vision.
Marina Henke: But as always, military tech takes a while to make its way to the public. Recreational headlamps wouldn’t offer that handy red light setting until the early 2000s.
Now, as far as the etiquette question, I don’t know when this became a thing. But it does seem like a nice way to avoid blinding hikers going the other way. And besides, you know who also hates bright white lights? The animals whose home you’re kind of crashing.
If you’d like to submit a question to the Outside/In team, you can record it as a voice memo on your smartphone and send it to outsidein@nhpr.org. You can also leave a message on our hotline, 1-844-GO-OTTER.
