you ever think about, like, how we learned about infrared?

so there's this dude, ol' bill herschel. german immigrant to britain, ends up becoming basically the king's astrologer.

He wants to look at the sun through a telescope

He's like "Well, different colors of glass will let through different amounts of light, but what about heat? Do different colors of light have differences in heat transference? Would that make it less difficult to look at the sun through this telescope?"

he's off to a brilliant start

So he sets up this thing with, like. A board with a slit to let some light through, twp thermometers to measure local temperature in the dark, one thermometer to measure the light coming through the slit, and a prism to let light through.

oh, he hasn't even started to illuminate this yet

So he goes through and he measures all of the colors of the rainbow for temperature, comparing against his control thermometers. Finds out that from violet to red, you get an increase in temperature. Violet light isn't very hot, red light transfers a lot of heat.

He looks at this, realizes that there's a curve upwards, and goes "hold up, what if it doesn't stop there?"

So he sets up another board with three thermometers positioned on top, and marks off five lines beyond the edge of the prism's rainbow

Measures them with the thermometers again. (I forgot to meantion that he spent ten minutes in each color, to make sure he had the measurement right, and the thermometer bulbs were painted black.)

He finds out that the bars of color (each about an inch thick) increased temperature as he went towards red, and then, after the red, kept increasing for an inch and a half. And then they stopped warming off and started going back to room temperature.

He's like

"So there's an invisible light that's unfit for vision."

publishes a paper on this in, like, 1800.

As with every scientific discovery in the 19th century, people threw fits and had to test it themselves. Some replicated his results, some didn't, so he does some more tests and publishes more paper. Figures out that no matter how he tries to make the light more powerful, the invisible light doesn't become visible.

Ends up with

(this ends up being a bit of a flawed chart, but that's not important at the moment.)

(It's still v. close.)

Anyhow, his stuff is eventually accepted. Seventy years later, someone, no one knows who, starts using the term infrared to describe it.

funnily enough, the discovery of ultraviolet light has nothing to do with the discovery of infrared.

(For a while they were calling infrared 'heat rays', which makes my sci-fi loving heart gleeful.)

omg, that's amazing

oh that is super interesting 👀