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International System of Units overhauled in historic vote

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Re: International System of Units overhauled in historic vote

#91
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?

The French Revolution attempted a decimal calendar alongside their switch to metric. It's a fascinating artifact: https://en.wikipedia.org/wiki/French_Republican_calendar

Calendars are hard because you've got multiple inconveniently disparate sources of information you want to unite: universal constants on the one hand (such as the second being tied now to atomic vibration) and more "local" concerns such as the orbital position of the earth with reference to the sun, the moon, other neighboring objects in the solar system.

Vernor Vinge's novels, as one example, use metric prefixes and seconds exclusively (this is referred to as Metric time [1]), which is a fun thought experiment. The biggest complaints are that the units aren't necessarily great for human activities and definitely don't align well with minutes/hours/days/weeks/months.

Hectosecond is close to a minute, but slightly larger (1.666 minutes). Kilosecond is about 16.666 minutes long, which is the closest unit to an hour. It's almost a useful quarter-hour (but again it doesn't line up that well). But then you hit the order of magnitude wall and the next prefix up is Megasecond which is nearly, but not quite a fortnight (~11 days), and Gigasecond is just shy of 32 years. You long at that point for more prefixes between Kilo-, Mega-, and Giga- if you are using seconds as base unit at that point, especially living on Earth and trying to coordinate calendar weeks, months, years. (There are non-standard prefixes Myria- (10^5), also from the French revolution, and Hebdo- (10^7) which are almost useful enough here to beg them to be standardized.)

[1] https://en.wikipedia.org/wiki/Metric_time

Re: International System of Units overhauled in historic vote

#92

I get that this is a significant milestone but this seems extremely overstated: "the new changes will have wide-reaching impact in science, technology, trade, health and the environment, among many other sectors." Am I missing something?

With the old definitions, the values of the known constants were just approximations, but now that the unit is defined based on the constants, we can consider the constant as being the exact value, no matter how imprecise it was when it was measured using old definitions of the units.

Re: International System of Units overhauled in historic vote

#93

So...How many Planck's is one Kilogram then? >The mass of the international prototype of the kilogram m(K) is equal to 1 kg within a relative standard uncertainty equal to that of the recommended value of h at the time this Resolution was adopted, namely 1.0 × 10-8 and that in the future its value will be determined experimentally, Is the Planck simply the most standard deviation the kilogram can stray from now?

This wikipedia section breaks down the new definition nicely https://en.wikipedia.org/wiki/Redefinition_of_SI_base_units#...

Re: International System of Units overhauled in historic vote

#94

Earlier quoted context omitted.

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/msp…

I already made it clear that I totally agree metric should be standard in engineering or scientific applications. I wasn’t aware that this isn’t the case in the US — thanks for the info. I believe it is at least 95% the case in the US and I think we should make every effort to get that to 100%. I still stand by my argument that it does not matter much for everyday life.

Why have two separate sets of unit systems?

Re: International System of Units overhauled in historic vote

#95
post #68

Earlier quoted context omitted.

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.

As opposed imperial constants? How is a foot standardized anyway? I suspect most manufactures rely on SI metrics for that.

There are no other standards. Metrology is expensive and doing it over again would offer no benefit whatsoever. All prior standards in widespread use were abandoned during the 20th century in favour of defining the relevant units in terms of SI units.

Specifically the international yard equals 0.9144 meters and the international pound equals 0.45359237 kilograms

There literally isn't another definition, in the US when you say "100 yards" the only legal meaning that has is 91.44 metres, which is whatever CGPM / BIPM says it is.

Re: International System of Units overhauled in historic vote

#96
post #69
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?

Interestingly, a week can roughly be approximated as 10k minutes (with an error of less than 1%).

And a year is PI * 10^7 seconds (within 0.5%).

Re: International System of Units overhauled in historic vote

#98
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?

Yep.

In Vernor Vinge's fiction, spacefaring humans even measure time in kiloseconds and megaseconds. 1 ks is slightly more than a quarter of an hour; 1 Ms is about eleven and a half days.

Re: International System of Units overhauled in historic vote

#99
post #41

Earlier quoted context omitted.

Metric had time from the start. However it was work 4 days, 1 day weekend. However the loss of personal time was very unpopular so it never caught on. I'm not sure why a metric hour didn't catch on.

I think I'm missing the joke. Mind explaining it?

No joke, except I was referring to decmial time not metric time. https://en.wikipedia.org/wiki/Metric_time https://en.wikipedia.org/wiki/Decimal_time

a 7 day week gives two days weekends every 5 days, so you quickly lose personal time on the 4 day week.

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