forty thousand kilometers, give or take

why is the metric system like that? — by mati ★

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if you've ever wondered what the circumference of the earth is, you've probably googled the number. and, if you're not an american who uses imperial instead of metric (like us normals do; i'm joking with saying "normals" but it's half-serious too), you will have noticed that the number is like, conspicuously round: if you go around the earth along the equator, you get 40 075.017 km, which is okayishly round, but the real surprise comes when you measure it passing through the poles, because in that case, the circumference of the earth is 40 007.863 km.

i want you to take a look at that number again. by a small margin of just seven kilometers, that number is basically forty thousand. it's one of those numbers that when you look at it, it feels too round to be true. if someone told me the circumference of the earth was 40 thousand km, i would say that they were making it up, because that's not the kind of number you see in the wild. even my chemistry teacher from high school used to know this; he once told the class that if you want to lie with numbers, you just add some random decimals. if you say the distance from new york to tokyo, for example, is "10 000 km", people are going to be like, no way you know that, you just made that up, and they would google it to fact-check you right in your face. but the conversation is completely different when you say that it's not 10 000, but 11 209. no one is going to think that you made up those decimal places, everyone is just going to accept what you say as fact — after all, if they know it with five-digits precision, there's no way they made that up, right? (well, i did just make that number up; the actual distance is 10 848 km.)

but, i'm here to tell you that that number is not made up. it's completely real, and it's really that round and that close to 40 000 by design. but to understand that, we have to start with the history: who decided a meter would be the size it is?

wait, why is this about math? i thought you wrote about linguistics...

well, i like other stuff as well. marticles is mostly for my linguistics thoughts, because that's my main area of interest. i do like other topics as well though — i really like this one specifically, and i feel like i'm qualified enough to write about it. honestly, you should've expected that i like math after having read some years can jump, which is about calendars. i hope you have fun reading this one, though!


scientific™ units for a scientific™ age

[to do]

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Pub: 03 Jun 2024 04:31 UTC
Edit: 03 Jun 2024 04:41 UTC
Views: 113