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International System of Units overhauled in historic vote

npl.co.uk

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Re: International System of Units overhauled in historic vote

#571

Post by mastazi »

subroutine wrote: post #434
mastazi wrote: post #408

Earlier quoted context omitted.

> I suspect that only a minority of people in metric-using countries -- those with basic chemistry knowledge fresh in their mind -- know that This is not the case. This part: "one milliliter of water occupies one cubic centimeter, weighs one gram" is known by most people, even kids in primary school. In other words everyone knows that a litre of water weighs one kilogram, and that there are 1000 litres in a square me…

"Everyone knows there are 1000 litres in a square metre" ;)

Ooops :-(

Re: International System of Units overhauled in historic vote

#572

Post by NeedMoreTea »

atoav wrote: post #452
NeedMoreTea wrote: post #365

Earlier quoted context omitted.

Buy an imperial rule. There's some inches that are sub-divided into tenths (maybe 1/20), and others sub-divided into sixteenths (maybe 32nds or 64ths). Often with heavier markings on more significance. For easy division and fractioning of whatever it is you are doing. If it's imperial only (v. rare nowadays) there's usually a coarser scale or two for easier subdivision or when the 16ths and finer just don't matter. B…

As someone who does a lot of woodworking in a metric world: the common fractions (e.g. 1/3) are not a problem at all, they are periodic. Adjusting my saw to 333.33mm or 6.66mm is something I do quite often. If you use fractions often or work with weirder fractions anybody who is worth their grain of salt will build custom temporary rulers or helper systems anyways. And then it won't matter at all if your unit is hype…

That's actually my point. Whilst I use metric for almost all things, an imperial rule is, for me, a better temporary custom rule for actually doing stuff like centre finding or sub-dividing, than the metric ones. The units don't matter a jot, the markings and spacings do.

Which is why I keep one of each in the tool chest. :)

Re: International System of Units overhauled in historic vote

#574

Post by aylmao »

XorNot wrote: post #299
aylmao wrote: post #166

Earlier quoted context omitted.

I think what the commenter is referring to is why use Avogadro's number instead of say, just Sextillions or Septillions.

I mean that really comes back to the "practical units" thing (and that chemists were the ones doing the work) - a kilogram of anything in chemistry is a huge amount, whereas a gram is about right to make "a lot" of something (in synthesis research people get excited about gram-scale synthetic yields). So it's pretty much chosen to get integer-ish units with common things you work with like carbon - i.e. 1 mole of car…

Yeah, that makes sense (:

Re: International System of Units overhauled in historic vote

#575

Post by sonnyblarney »

MzxgckZtNqX5i wrote: post #516
sonnyblarney wrote: post #493

Earlier quoted context omitted.

All of your regular coffee cups are exactly 250ml. Regular people use them for basic baking all the time, like making pancakes. 'Cups' are still better measures than ml because even you, in your self-acclaimed ignorance have a sense of how much a cup is whereas people do not have any idea how much '300ml' is. Canadians have no clue what 10ml of anything is. Canadians will continue to use feet and pounds for personal…

How can you be sure that "all of your regular coffee cups are exactly 250ml"? And what about teaspoon? And everything else? Everyone here is obviously biased toward his/her own measurement system based on our experience, but the fact that "3 cups and a half of milk" is more precise than "875mL of milk" is clearly false.

I didn't say anything about Imperial being more precise.

I'm saying it's often more useful.

1 cup mix, 1 cup milk + 1 egg.

1 pint of beer.

1 teaspoon of sugar.

These are things everyone can understand.

You can put the ml on the side of the label.

"That guy is 6 feet tall, about 180 lbs."

Is better than metric for most people.

"I'll have a glass of wine" instead of "I'll have 240 ml of wine"

Any one of you who orders beer by the 'ml' can keep arguing with me, but I suspect you all order 'pints' in which case you should consider for a moment why you do that.

Re: International System of Units overhauled in historic vote

#576

Post by sonnyblarney »

DanBC wrote: post #517
sonnyblarney wrote: post #493

Earlier quoted context omitted.

All of your regular coffee cups are exactly 250ml. Regular people use them for basic baking all the time, like making pancakes. 'Cups' are still better measures than ml because even you, in your self-acclaimed ignorance have a sense of how much a cup is whereas people do not have any idea how much '300ml' is. Canadians have no clue what 10ml of anything is. Canadians will continue to use feet and pounds for personal…

> whereas people do not have any idea how much '300ml' is. No, you get a sense of this if you live somewhere that uses ml for things. One can of soda is 330 ml.

I live in Canada we use ml and nobody orders beer in ml.

5 grams of sugar? Nobody knows what that means.

They know what 5 tea-spoons is though.

I'll be $100 that if they put 'teaspoons of sugar' instead of grams, people would be shocked. There are videos showing how much sugar in a can of Coke, and it's largely because people are oblivious to the units on the label, which we can all technically read.

Re: International System of Units overhauled in historic vote

#577

Post by thefringthing »

blhack wrote: post #232
kibwen wrote: post #188

See, the US wasn't being stubborn in not adopting metric, it was just waiting patiently for it to progress from beta to 1.0. :) (Fun fact: all the US customary units have been officially defined in terms of their metric counterparts since 1893: https://www.nist.gov/sites/default/files/documents/pml/wmd/m... )

I'm one of the weird people that actually really likes imperial units. For instance: 1 foot -- base 12. This is a superior base to 10. It can be easily divided into 4ths, 3rd, and 2nds. Base 10 can only easily be divided into 2nds. 1 inch -- an easily identifiable unit of measure for smallish things. About the width of my thumb. A pretty good unit. For low precision, inches become 1/2, 1/4, 1/8, 1/6, 1/64, etc. Each…

You should be careful about the term "imperial". US customary units do not always match the old British "imperial" units. A US fluid pint is significantly smaller than an Imperial pint, for example.

Re: International System of Units overhauled in historic vote

#578

Post by Aunche »

maccam94 wrote: post #173
jackpirate wrote: post #153

Earlier quoted context omitted.

I think the GP is making the claim that Avogadro's constant should be 1 (effectively eliminating it), not that there's no need to count molecules.

An Avogadro's constant number of molecules is one mole. One mole of hydrogen has much less mass than one mole of iron. You have to choose an arbitrary mass of a single element as the base quantity. Hydrogen might be the best theoretically, it's just a proton and an electron, but it is tricky to work with because it's a gas at room temperature. So instead the mole has been defined as the number of molecules in a speci…

Why does it need to be based on the mass of an arbitrary molecule? Can't it just be 10^23 or 10^24? Most of the time, you're going to have to look up constants to convert moles to mass anyways.

Re: International System of Units overhauled in historic vote

#579

Post by wolf550e »

School-Cotton wrote: post #401
jameshart wrote: post #364

Earlier quoted context omitted.

You're right - imperial is far superior for precise building or manufacturing work. Take drill bits, for example. Obviously it's much easier to figure out that 11/32" is less than 3/8". Or is it more? No, I'm pretty sure I was right the first time. The metric ones with their 5.5mm, 6mm, 6.5mm sequencing are just too complicated to work with, in comparison. And half a millimeter isn't very precise - it's much bigger t…

Whether decimals or fractions are used is not necessarily related to metric vs. customary units. I just weighed myself on my bathroom scale -- 191.2 pounds.

People use "stones" for weight of humans. As if 14 pounds is a convenient amount.

Re: International System of Units overhauled in historic vote

#580

Post by gnopgnip »

edoo wrote: post #314
gnopgnip wrote: post #258

Earlier quoted context omitted.

The US officially adopted the metric system in 1975 with the Metric Conversion Act.

The act does not require the US to use metric in any capacity. It is optional. If it did kids would not be taught using the imperial system.

There are a lot of situations in the US where using dual measurements, or just using metric is required, like food labeling. Using customary units is optional in many cases
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