International System of Units overhauled in historic vote • Hacker News Board

Re: International System of Units overhauled in historic vote

#341

Post by int_19h » Sat, Nov 17, 2018, 3:07 AM UTC

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…

Base 12 is more convenient than base 10. But that argument really only works if numbers were written in base 12. They're not, though, and that isn't changing any time soon. As a result, Imperial has to deal with two bases - the units themselves are defined base 12 (more or less; it's not really consistent e.g. with volume), but then you still have to do arithmetic in base 10.

So, until such time as we switch to base 12 for all numbers, metric is superior, because it is simpler.

Re: International System of Units overhauled in historic vote

#342

Post by sib » Sat, Nov 17, 2018, 3:07 AM UTC

zjaffee wrote: post #305

blhack wrote: post #232

Earlier quoted context omitted.

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…

While I agree that in many ways imperial is better than metric in the way that you mention. It is absolutely atrocious when it comes to weight and volume. A gallon is still a base 10 unit of measure of water (10 pounds of water). Then only after that, is it in base 8 rather than maintaining that base 12 consistency. Then if you look at imperial units of weight, it deviates away from base 12 again. It counts upwards f…

>> "A gallon is still a base 10 unit of measure of water (10 pounds of water)."

Not sure what you are getting at here. A gallon is about 8.3 lbs (3.8kg).

A gallon is 128 oz, a nice base-2 number.

Re: International System of Units overhauled in historic vote

#343

Post by int_19h » Sat, Nov 17, 2018, 3:11 AM UTC

max76 wrote: post #252

ZainRiz wrote: post #201

Earlier quoted context omitted.

Now can we redefine 1 pound to equal 1 kg? (the opposite of https://xkcd.com/2073 )

Can you imagine the confusion? Having the same word mean a different amount of something would cause a lot of misunderstanding. Saying "This car weighs 2200 poundsm" have two different meanings depending on the year you said it sounds awful. The new metric definitions work because they don't change the actual amount, they just change the way the amount is defined. (Natural constant vs reference weight)

We could gradually redefine pound to be closer and closer to kilogram, say, over a century, so that people don't notice. ~

Re: International System of Units overhauled in historic vote

#344

Post by AngryData » Sat, Nov 17, 2018, 3:12 AM UTC

Waterluvian wrote: post #192

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... )

So it's fair to rib my American friends with the fact that Imperial is implemented using metric?

Only if we can rib on you for using imperial machining standards and imperial pipe thread forms.

Re: International System of Units overhauled in historic vote

#345

Post by garmaine » Sat, Nov 17, 2018, 3:16 AM UTC

Zarel wrote: post #233

garmaine wrote: post #176

Earlier quoted context omitted.

Read the OP. It is now a fundamental constant. (But you’re right if you’re referring to the status quo before).

No, it's not. Avogadro's number is a constant, but it's not fundamental - the only difference is that it's defined in terms of fundamental constants (namely, the Planck constant) now. It's still an arbitrary number defined in terms of the mass of a gram.

Nope, it is fixed to be N_A = 602,214,076,000,000,000,000,000 exactly (6.02214076x10^23 to units precision).

It used to be the case that the mole was an experimental value equal to the number of atoms in a certain mass of a certain something. That is no longer the case with this revision. It is a fixed, never changing integer constant.

This does mean that 1 mole of carbon-12 is no longer exactly 12 grams. But it is approximately 12.0000000 grams, which is within the best we can experimentally measure today, so nothing changes in practice as a result of this update except first chapter of an introductory chemistry textbook (good excuse to push out a 9th edition for $250!).

Therefore it is accurate to say now that whereas before the Avogadro's number was experimentally determined based the exact expressed mass of a carbon-12 atom relative to a platinum-iridium cylinder in Paris (the old kg), it is now the case that the expressed mass of the carbon-12 atom must be measured relative to the a kg definition based on Planck's constant.

(I say "expressed mass" because this situation is a little confusing... I'm talking about the numbers we write down expressing the mass as a multiple of some standard kilogram. That reference mass changed, not the actual inertial mass.)

EDIT: Or you can just read the draft of the agreement that was voted on. The definitions are on the first page:

https://www.bipm.org/utils/en/pdf/CGPM/Draft-Resolution-A-EN...

Re: International System of Units overhauled in historic vote

#346

Post by int_19h » Sat, Nov 17, 2018, 3:18 AM UTC

thaumasiotes wrote: post #229

mbreese wrote: post #193

Earlier quoted context omitted.

I think this is exactly the rationale. But, from a more practical perspective... If instead of g/mol, we referred to molecules/g -- we would end up populating tables and charts with really big numbers. This would make lookup tables hard to read, difficult to publish, and hard to work with. Imagine if you had to do math with a bunch of 10^23 exponents all of the time. Instead, it was agreed to effectively pull out a c…

> Even for this SI overhaul, we didn't really even need to redefine the mole, except for the fact that it was previously defined in terms of the old kg. This was just "fixing a glitch". I came to complain about the article calling the mole a "base unit of the SI", and this seems like an appropriate thread. Why is the mole a defined unit at all? As far as I understand things, "one mole" is the same thing as Avogadro's…

The new definition of mole is exactly that - it's just 6.02214076×10^23 items of whatever, and no longer depends on kilogram.

Re: International System of Units overhauled in historic vote

#347

Post by redial » Sat, Nov 17, 2018, 3:22 AM UTC

kbenson wrote: post #293

megablast wrote: post #279

Earlier quoted context omitted.

No matter what is suggested, no matter how much better the alternative, there will always be a group of contrary people. Look at flat earthers. Look at anti-vaxers.

There are actual benefits to some imperial units when working in small amounts. They can often be subdivided much more easily into amounts that are harder to handle (or at least require going to another order of magnitude to do accurately). For example, dividing a foot into thirds or fourths is trivial, but for a meter it requires either going two orders of magnitude (25/100ths for a quarter) or simply cannot perfect…

> but for a meter it requires either going two orders of magnitude (25/100ths for a quarter) or simply cannot perfectly represent the amount (1/3).

What? you switch to metric and suddenly fractions are not a thing any more?

1/3 m is just that, one third of a meter, perfectly. How is that so complicated? It can also be 333.3mm. And no one would write it as 333/1000 to make it seem more complicated than it is.

Re: International System of Units overhauled in historic vote

#348

Post by fnordsensei » Sat, Nov 17, 2018, 3:25 AM UTC

Just_Smith wrote: post #325

naikrovek wrote: post #319

Earlier quoted context omitted.

I can cut 1/3 of a meter just as accurately as you can cut 1/3 of a yard. Not being a whole number does not make it harder to find where it is.

Ha! I'm happy for your apparent virtuosity, but the whole of America's construction industry is quite a few years into disagreeing with you.

So THAT'S why U.S., Liberian and Myanmar architecture is centuries ahead of the rest of the world.

By the way, why isn't your currency base 12? All the purported benefits that apply to length would certainly apply to money as well.

Re: International System of Units overhauled in historic vote

#349

Post by mbroncano » Sat, Nov 17, 2018, 3:26 AM UTC

blhack wrote: post #274

mbroncano wrote: post #265

Earlier quoted context omitted.

Most probably because you grew up with it. I’m pretty sure you think the same about your religion, nation, race ... but be sure eveybody else in the world may think the same of their own. And they’d be right too. What I personally find disturbing is how irrational positions such as yours are commonly accepted in a supposedly advanced society. It leads to a pretty bumpy road, time and time again.

Well I actually grew up with the metric system. I'm also not the religion I was raised. I do love my nation, which is easy because I'm American and there is a lot to love. Imperial units are just better for humans to use. I would love if somebody could give me a redeeming quality for metric, but so far nobody has.

That’s usually called the zeal of the convert. First generation immigrants are quite adept at it.

Re: International System of Units overhauled in historic vote

#350

Post by philistine » Sat, Nov 17, 2018, 3:31 AM UTC

deelowe wrote: post #262

devindotcom wrote: post #241

Earlier quoted context omitted.

I hadn't thought of some of these advantages. Some are subjective, but it's hard to deny the intuitive nature of others. I say bring back the span and the rod as well.

Go walk a job site with a tradesman and youll see why imperial is so useful and natural to them. They walk off long distancrs, use knuckles for small ones and do complex division with ease.

Because they have to since they're stuck using imperial. The imperial system does not make people better, it forces people to use fractions.