Inspiration for worldbuilding is everywhere, and I was handed a particularly delightful source the other weekend by my father in the form of one of his college textbooks: Engineering Unit Conversions, by Michael R. Lindeburg, P.E.

I am not an engineer, Google can do measurement conversions, and I don’t need a book of conversions. But I love this book. Love it. It is a treasure trove full of history and politics and hints at the way human societies and brains work and I love it.

Can weights and measures tell you about a society? Oh boy.

I stopped on a random page and picked the first measurement I saw, just to see what I’d find. A “bougie decimale” can be converted into candles, carcel units, English sperm candles, hefner units, lumens/sterad, and pentane candles, so I’m guessing a bougie decimale is a way of measuring light. This is literally right: it’s French for ‘decimal candle,’ which is a unit of luminous intensity, defined in 1889 at the Second International Electrical Congress in Paris.

Already, we’ve got to stop here. There was an International Electrical Congress? More than one of them? Apparently so! For about two decades there were international meetings, started by the French, with the aim of developing standards for units of measurement in electrical engineering. They invited experts from various countries, so inevitably they also discussed advances in electrical engineering and science, like the telegraph.

You have to pause here to appreciate that different people are going to develop different ways of measuring things… and that they’re going to have to talk to one another, and understand what they mean. Not just for scientific reasons (“can a scientist from my country understand what you’re talking about”), or for engineering reasons (“if I get a lamp from your factory, will I have the fuel for it, in the right form”), but also for trade reasons (“if I buy a lamp from you, how will I know how bright it is, and if that will fulfill my lighting needs?”) Knowledge isn’t the only thing that people share across boundaries; so are trade goods. Inevitably, you’re going to have to understand each other’s names for things.

But to get back to our decimal candle… already we see that units of measurement were different across nations. The French defined their bougie decimale as 1/20th of a voile… which is the light put out by one square centimeter of glowing platinum at the temperature at which it freezes. What even is this exotic amazingness? And the voile, like many units of measurement, was named after a person, the French physicist who proposed that the incandescence of a metal at its freezing point should be considered a standard for measuring light.

So we have a French measurement… but wait, here come the Germans! A hefner unit is equal to the intensity of light put out by a lamp created by a German engineer, von Hefner-Alteneck. This lamp was… complicated. It burned amyl acetate, and the version used for the measurement had to have a specific flame height (40 millimeters). The carcel unit, it turns out, is another lamp-specific measurement… in this case, invented by a French watchmaker. So is the pentane lamp, which gives us the pentane candle measurement… not literally a candle, but a description of its output (candles, but from a pentane lamp, so: pentane candles).

And then there are the remaining candles: English sperm candles and international candles. The first was created from the crystallized wax harvested from the head cavity of whales, prized for its colorless and odorless brightness. John Adams (yes, the president, though he wasn’t at the time), tried to get the British to invest in them for their street lamps: “[T]he fat of the spermaceti whale gives the clearest and most beautiful flame of any substance that is known in nature, and we are surprised you prefer darkness, and consequent robberies, burglaries, and murders in your streets to receiving as a remittance our spermaceti oil.” Oof. Not very diplomatic there, sir.

The international candle was defined at that conference as a one-sixth-pound candle of sperm wax, burning at the rate of 120 grains per hour. The international candle was later redefined as the luminous intensity of a square centimeter of a blackbody radiator at the temperature molten platinum solidifies. (!). That was called the ‘new candle’ for a while. But then they went and renamed it the candela in 1948, and it is now formally defined as ‘1 lumen per steradian.”

That makes all these other measurements antiques: no one uses them anymore. So there’s another amazing concept: measurements can become irrelevant as society changes. Just looking at this one, specific measurement (brightness), we discover that society defined it initially as the light of the best candle they could find, and then various lamps they could design, and then they discovered that people from different countries had different ideas of what lamps and candles could do, so that necessitated an international discussion about how we could standardize measures. And as technology marched on, so did the reliability and consistency of the measurement.

And this is just one measurement! Everywhere you look in this book, there are hints of history. A barleycorn is a third of an inch, defined in England in 1300 as part of a statue at the time (the Composition of Yards and Perches, which wasn’t displaced until 1824 with the Weights and Measures Act). And yes, it was taken from… barleycorns (pulled from the center of the barley ear, not the top or bottom). But here’s the weird thing… shoe sizes are still measured in barleycorns in England. That’s what the mysterious ‘I am a size 9’ thing is about. (But why are they different in America? In Europe? Down the rabbit hole again…)

Just looking up some of these measurements is fascinating. A firkin? A liquid measure from the Gospel, when the water was turned into wine. It was assumed to be equivalent to a Hebrew bath, which is purportedly nine gallons. Or is it? Other sources claim it’s Dutch by way of Middle English ferdekyn, for a fourth of a barrel. The British ale definition of a firkin is eight gallons. Wander through the pages and you’ll discover how many people gave their names to measurements, securing their legacies—until those measurements fell out of favor. You find yourself asking questions, like why is a nautical mile different from a statue mile? (Oh, my, is that a deep, deep well of fascinating history, going back to Roman times.) What on earth is a miner’s inch? (I bet that’s a fascinating story.) Why do we need a measurement for cubic feet/mile2 (and how fascinating that the only thing it can be converted to is ‘inches of runoff’… a clue!).

The takeaway here is that all around you is stuff you take for granted… and that will almost always have a great deal of history beneath it, if you dig. Become as curious as cats, and learn to dig, poke, and prod at everything; assume there’s more beneath the surface than above it. There’s worldbuilding inspiration everywhere!

And now, I think I will return to perusing this book. I don’t yet know why kilometers can be converted into Gunter’s, or surveyor’s chains, as opposed to Ramsden’s, or engineer’s chains. I am imagining a feud between Gunter’s army of surveyors and Ramsden’s horde of engineers. That has got to be a good story.