81–90 of 589 posts
> 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.
Earlier quoted context omitted.
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…
> Just hoping the secondary ones are NOT also made from platinum They are. They are made identically to the primary.
Fingers crossed. :)
Is it anyone with a kibble balance can now certify calibrations? How do you know your kibble balance is as accurate as the next guy's kibble balance?
https://www.nist.gov/si-redefinition/kilogram-kibble-balance
Edit: Found some information explaining this from NIST: https://www.nist.gov/si-redefinition/kilogram-disseminating-...
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?
I can imagine that in 100-200 years we'll have to adjust some unit because our understanding of some constant was just slightly wrong.
Too bad US doesn't use them.
Fun (?) anecdote - metric apparently has been used in US engineering for quite a while; a petrolhead buddy of mine was puzzled as to all the fractions used on the drawings of his (I think) Chrysler Hemi V8 from the fifties - on a hunch, we converted a few to metric. Bingo. (Just making up a number here) 3.937" stroke? Why on Earth... Ah. 100.0mm. That's why.
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?
I don't know about trade, but kilo standards were deviating by tens of micrograms from eachother, some things are sold at prices which warrant accounting for those micrograms, so a completely stable international definition seems helpful. Certain types of scientific instrument will need to be recalibrated to meet the new definitions.
And if you buy a kilogram of something and they accidentally short you by a few micrograms, haven't you only overpaid by a few parts per billion? Even on a billion dollar order you've only overpaid by a few dollars...
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?
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?
Earlier quoted context omitted.
Heinlein's "Starship Troopers" has the space marines using "kiloseconds" and "megaseconds" conversationally, and it was always tricky for me to convert those to hours and minutes in my head accurately.
Odd choices... since 1000 seconds is ~17 minutes and 1M seconds is 4.6 hours.
$ units --verbose
Currency exchange rates from FloatRates (USD base) on 2018-10-25
3070 units, 109 prefixes, 109 nonlinear units
You have: 1 megasecond
You want: 1 day
1 megasecond = 11.574074 * 1 day
1 megasecond = (1 / 0.0864) * 1 day