Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Common mistakes when using the metric system

nayuki.io

Post reply on HN
Print view View original

71–80 of 100 posts

Re: Common mistakes when using the metric system

#71

Post by kkfx »

poulpy123 wrote: post #55
ikari_pl wrote: post #14

I was surprised to see "L" as the "only correct" (though as minor mistake) abbreviation for a liter, being certain "l" or "ℓ" is the way to go, as that's how I was taught so far. Turns out that SI actually allows both "l" and "L", but I would only ever use the uppercase if it's a sans-serif font in a non-prefixed unit ("L" as opposed to "ml"). I've never seen any can or bottle using "mL" or "cL". Some of the examples…

gr. is not uncommon in france. Not in formal publications, but in day to day life you may find it. I know that I use it sometimes

Also avoid confusion with gravity acceleration :D

Re: Common mistakes when using the metric system

#72

Post by setopt »

PinguTS wrote: post #39
setopt wrote: post #17

Earlier quoted context omitted.

Note: The official SI unit “liter” was written “l” until a couple of decades ago, when they changed it to “L” due to frequent legibility issues (l/I/1). Some old texts use the old convention.

Changed? I never have seen the captial L for liter anywhere from daily use to scientific papers. It is always used in small caps.

I don’t know which field you work in, but I do research in physics and chemistry and L is the dominant convention in the papers I read. I also teach intro physics at the university level and the textbook uses L.

In high school (~2008) we were taught that this was the correct new abbreviation for liter in chemistry, but I remember that at the time lower-case l (or sometimes \ell) was still normal as well. These days, I rarely see that.

(Off-topic: “Small caps” is not the same as “lower case”.)

Re: Common mistakes when using the metric system

#73

Post by USiBqidmOOkAqRb »

immibis wrote: post #54
tkgally wrote: post #32

I thought this looked like good advice until I got to: > Mass/weight distinction > Incorrect: He weighs 70 kg; Correct: His mass is 70 kg > Incorrect: She weighs 50 kg; Correct: She weighs 490 N on Earth Really?! We’re not supposed to use kilograms to describe a person’s weight? And to describe someone’s weight, we have to use newtons and specify what planet they’re on? Good luck enforcing those rules.

It's all pedantry. Physics makes a distinction between mass, a (mostly) invariant property of an object, and weight, the force proportional to your mass and the planet you're standing on divided by the square of the radius. Only physicists care about this distinction.

I would like to believe engineers care too. A simple action like standing up or being on a bus that's taking a curve will make items on your person weigh more.

Re: Common mistakes when using the metric system

#74

Post by ndsipa_pomu »

kkfx wrote: post #70
ulbu wrote: post #28

Earlier quoted context omitted.

yea, reads like "grains"

People do not know much about old cartridge powder measures though :D

"Grains" are still used for measuring out powder/chemicals (also arrows). If I saw "gr", I'd interpret that as grains rather than grammes as "g" is definitely grammes, so the extra "r" must signify something.

Re: Common mistakes when using the metric system

#76

Post by ndsipa_pomu »

LinAGKar wrote: post #18
Hadarai5 wrote: post #3

I've never seen Mtr, sqm or gr. Even as a child, I knew the short of those unit names.

I have seen usage of kvm (kvadratmeter) in Sweden

Like we need another overload of "kvm"

(Kernel Virtual Machine in Linux or Keyboard Video Monitor in server switching kit)

Re: Common mistakes when using the metric system

#78

Post by ndsipa_pomu »

tkgally wrote: post #32

I thought this looked like good advice until I got to: > Mass/weight distinction > Incorrect: He weighs 70 kg; Correct: His mass is 70 kg > Incorrect: She weighs 50 kg; Correct: She weighs 490 N on Earth Really?! We’re not supposed to use kilograms to describe a person’s weight? And to describe someone’s weight, we have to use newtons and specify what planet they’re on? Good luck enforcing those rules.

The issue is that it's very common for people to use weight when they're referring to mass. We get away with it as our weight doesn't change very much when on Earth, but if we start populating other planets, then we're going to have to become more precise.

Re: Common mistakes when using the metric system

#79

Post by ndsipa_pomu »

consp wrote: post #20
ikari_pl wrote: post #14

I was surprised to see "L" as the "only correct" (though as minor mistake) abbreviation for a liter, being certain "l" or "ℓ" is the way to go, as that's how I was taught so far. Turns out that SI actually allows both "l" and "L", but I would only ever use the uppercase if it's a sans-serif font in a non-prefixed unit ("L" as opposed to "ml"). I've never seen any can or bottle using "mL" or "cL". Some of the examples…

> either calling spelling I'd never see a "common mistake" (like "gr." for grams) Almost all cooking books I have do this (sample size is not big though, and with almost all I mean all except one). I don't know why though, maybe it's an old abbreviation which stuck in certain text types?

I've got a serious bugbear with recipes using "cups" as a measure - it infuriates me. Who in their right mind uses a volume measurement for foods that can vary hugely in their size according to how long they've been sitting around?

Re: Common mistakes when using the metric system

#80

Post by physicsguy »

qwery wrote: post #64
physicsguy wrote: post #60

Lots of these are country dependent in terms of what is familiar to people. To some degree that matters if your primary communication is not international but domestic. For e.g. in the UK sqm is very common, particularly when looking at property. On RightMove which is the most popular property website here, for e.g. you can see here that the default is `sq ft` with `sq m` given underneath: https://www.rightmove.co.uk…

> I think the things chosen are a bit strange. I've never seen anyone write '15070 grams', it'd almost always be given as 1.507 kilograms. I'm sure it's just a typo, but 15,000 grams is 15 kilograms. So: 15.07 kg. I don't think they arrived at some of the more extreme examples by accident, but I could only speculate on the intent behind them.

Definitely a typo :D I'd not had my morning coffee!
Post reply on HN