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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

#51

Post by lb1lf »

keketi wrote: post #11
xaduha wrote: post #6

> a cylinder of a platinum alloy stored at the BIPM in France, will now be retired. It will be replaced by the Planck constant – the fundamental constant of quantum physics. I thought they did that long time ago.

I wonder how much the cylinder will auction for.

I have already sent an email to the Norwegian bureau of standards to inquire about buying one of their secondary kilogram standards - presumably they'll want a couple for displays and museums, but it would make for a great letter weight. (Just hoping the secondary ones are NOT also made from platinum. That is a tad too extravagant, even for a measurement nut.)

I do happen to have the previous generation time standard in my garage, though, a HP 5061A Cs clock.

Re: International System of Units overhauled in historic vote

#52

Post by echodevnull »

ballenf wrote: post #35

Has a "metric" version of time ever been proposed? Seems odd to me that we're "ok" with divisions of 12 for time but not length. I guess for science seconds are basically the only measure of time that usually matters?

There has been a proposal during the French Revolution with 10 hours a day, 100 minutes an hour and 100 seconds a minute. But it has only been in use for a few years beginning in 1792: https://en.wikipedia.org/wiki/Decimal_time

Re: International System of Units overhauled in historic vote

#53

Post by weinzierl »

3pt14159 wrote: post #12

This is probably the dumbest thing I'll type on HN. In university I just gave up trying to understand why we even needed the Avogadro constant / mole as a fundamental constant. It still confuses me. Why have a difference between molar mass and mass? Why couldn't it just be "1" and everything else change around it?

leni536’s answer is the real answer but I’ll give you another more meta one:

Because the SI system is redundant anyway one constant more or less doesn’t matter much.

If you want a truly minimalist system you can use CGM or MKS.

Re: International System of Units overhauled in historic vote

#54

Post by reaperducer »

School-Cotton wrote: post #37
piano wrote: post #21

Earlier quoted context omitted.

They really should cut the middle man. What surprised me reading that wiki page is that apparently the metric system was opposed in the US based on religious reasons . That is mind-boggling.

Is there any compelling reason why the US should switch to the metric system for daily use? Metric is already used universally in science and engineering, which seem to be the main fields in which consistency across countries matters. I completely agree that in physics, chemistry, engineering, medicine, etc., it is important to use standard units. But what harm is it doing in practice if in everyday life, Americans s…

A good comparison is degrees Celsius, which are just as arbitrary/unscientific (the standard metric unit is the Kelvin). Somehow people around the world get along fine using Celsius.

You don't realize how arbitrary Fahrenheit and Celsius are until you try cooking at altitude. When I make breakfast in a particular town I frequent, it takes almost an extra minute to boil an egg.

Re: International System of Units overhauled in historic vote

#55

Post by ars »

piano wrote: post #21
throwaway2048 wrote: post #10

Earlier quoted context omitted.

It does actually, US measurements are legally defined in terms of metric units. https://en.wikipedia.org/wiki/United_States_customary_units

They really should cut the middle man. What surprised me reading that wiki page is that apparently the metric system was opposed in the US based on religious reasons . That is mind-boggling.

> is that apparently the metric system was opposed in the US based on religious reasons.

As you will discover people often use religion as an excuse for things they anyway want to do. Usually they are people who only pay lip service to their religion.

Someone didn't want to use Metric. Religion doesn't actually have anything to do with it.

> That is mind-boggling.

It shouldn't be. I assume you are surprised that religion is involved in this, but actually it is not. If they were Atheist they would have the same objection, just using different words.

Basically you need to distinguish between people being people, and people acting in a certain way because of religion. This is an example of the former.

Re: International System of Units overhauled in historic vote

#56

Post by reaperducer »

orblivion wrote: post #26

I guess the next redefinition will happen if and when there's detectable drift in "fundamental" constants?

I guess the next redefinition will happen if and when there's detectable drift in "fundamental" constants?

And until then, all the metric fanbois will constantly tell you that metric is superior to imperial because its measurements are immutable. Until suddenly they are.

Re: International System of Units overhauled in historic vote

#57

Post by macintux »

School-Cotton wrote: post #37
piano wrote: post #21

Earlier quoted context omitted.

They really should cut the middle man. What surprised me reading that wiki page is that apparently the metric system was opposed in the US based on religious reasons . That is mind-boggling.

Is there any compelling reason why the US should switch to the metric system for daily use? Metric is already used universally in science and engineering, which seem to be the main fields in which consistency across countries matters. I completely agree that in physics, chemistry, engineering, medicine, etc., it is important to use standard units. But what harm is it doing in practice if in everyday life, Americans s…

My Jeep is a bizarre combination of metric and SAE. ISS needs to have two sets of tools[0]. NASA lost the Mars Climate Orbiter due to confusion over the units of measure[1]. Patients are given the wrong dosages[2].

It seems safe to say it's a point of ongoing friction, especially on things like international trade.

[0]: https://space.stackexchange.com/questions/12391/iss-nuts-and... [1]: https://mars.jpl.nasa.gov/msp98/news/mco991110.html [2]: https://www.chihaklaw.com/Articles/Confusion-over-metric-mea...

Re: International System of Units overhauled in historic vote

#58

Post by titanomachy »

ballenf wrote: post #35

Has a "metric" version of time ever been proposed? Seems odd to me that we're "ok" with divisions of 12 for time but not length. I guess for science seconds are basically the only measure of time that usually matters?

Yeah, I don't think it's really an issue. Physicists only convert things to hours/days/years when disseminating results to a broader audience, when doing the actual physics everything is microseconds or megaseconds or whatever.

Re: International System of Units overhauled in historic vote

#59

Post by kozak »

ballenf wrote: post #35

Has a "metric" version of time ever been proposed? Seems odd to me that we're "ok" with divisions of 12 for time but not length. I guess for science seconds are basically the only measure of time that usually matters?

24 and 60 do make sense because they are highly composite numbers: https://en.wikipedia.org/wiki/Highly_composite_number

Re: International System of Units overhauled in historic vote

#60

Post by ars »

tpush wrote: post #47
School-Cotton wrote: post #37

Earlier quoted context omitted.

Is there any compelling reason why the US should switch to the metric system for daily use? Metric is already used universally in science and engineering, which seem to be the main fields in which consistency across countries matters. I completely agree that in physics, chemistry, engineering, medicine, etc., it is important to use standard units. But what harm is it doing in practice if in everyday life, Americans s…

> A good comparison is degrees Celsius, which are just as arbitrary/unscientific (the standard metric unit is the Kelvin). Celsius is literally the same scale as Kelvin, just shifted so that 0c = water freezing.

Celsius is a particularly bad metric unit. It doesn't have enough units in the range most commonly encountered by humans, and it goes negative, which is also to be avoided in a good unit.

So you end up needing negatives, and decimals.

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