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Technology Science

Big Test Coming Up For Kilogram Redefinition (ieee.org) 127

szotz writes: Electromechanical balances have got to be better than an aged lump of platinum and iridium right? Teams are working to get kilograms measured and shipped to Paris in time for a test to see whether the technology (along with another that uses ultrapure silicon spheres) is now ready to redefine the kilogram. Why is this redefinition interesting? Because it's about using physics to overcome one problem with weight standards based on tightly held exemplars in standards bodies' inner sanctums: the mass of those exemplars can change, however subtly, introducing uncertainty and confusion. From the article: The world's metrologists aim to change this state of affairs in 2018 by fixing the kilogram to the Planck constant, a fundamental physical constant. That shift would, at least in principle, allow any laboratory to "realize" the kilogram from scratch with a series of experiments and specialized equipment. But for that scheme to work, the kilogram derived by one laboratory must be the same as those derived by others.
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Big Test Coming Up For Kilogram Redefinition

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  • So really... (Score:2, Offtopic)

    by houstonbofh ( 602064 )
    So really it is just a global scientific test of who's is bigger.
  • so (Score:3, Funny)

    by slazzy ( 864185 ) on Wednesday February 24, 2016 @02:25AM (#51573077) Homepage Journal
    Sounds like they won't be needing that kilo of platnium anymore... Send it to me please.
  • hey, that's cool. the planck constant can not and will not ever, ever possibly change. right, literally everyone alive now and in the foreseeable future?

    *hell freezes over*


    • by aliquis ( 678370 )

      Shouldn't it be the "general" definition? Fuck the metal weight - 1 kg is 1 liter of (distilled/pure) water (at 1 atmosphere pressure)? The amount of heavy hydrogen messes it up? 1 atmosphere of pressure isn't the same at all places on the earth due to varying gravity?

      • Re: (Score:3, Insightful)

        by Anonymous Coward

        Yes. How many atoms are there in 1 liter? I guess you could go more 'general' and say how many drops of water? But then, how big are the drops of water? What about the absorbtion rate of the material, can it only be measured in glass? is this deformed at 1 atmosphere pressure? evaporation rates?

        Then you get to mineral/chemical impurities, atmospheric disturbances, etc.

        Maybe 1 kg vs 0.999997 kg doesn't mater to you but there are many cases where it will. And calibrating our scales to allow that fine-grained

      • by stevelinton ( 4044 ) <sal@dcs.st-and.ac.uk> on Wednesday February 24, 2016 @06:17AM (#51573707) Homepage

        Whatever standard you adopt needs to be reproducable within the limits of the best current measurements by any other technique. Otherwise when people want a stable reproducible result they will use the other technique and the standard won't have worked. Measuring volume of water, purity, temperature and pressure is just not precisely reproducible enough

      • Actually - it would make more sense to define that one the other way around. If you have an atomic-accuracy measurement for mass, then it's much more sensible to define volume from mass than the other way around: so you would instead define liter as "the volume of a kilogram of water when these conditions are all at these specific values".

        • by aliquis ( 678370 )

          But we already have one for the liter?
          "1 liter = 1.18101066 Ã-- 10^(-51) cubic light years"
          (that one likely rounded off but you get the idea.)

          "Add one 6 Ã-- 10^(-54) cubic light years of tea-leaves per cup."

      • except your 1 atmosphere is 101325 Pa, a Pa being 1 newton per square meter, a newton being defined as force needed to accelerate *1 kilgram* at 1 meter per second squared

        do you see any problem?

        • by aliquis ( 678370 )

          The idea was that 1 atmosphere would be the the pressure of 10 meters of water (where?! :D) and it would all be solved out by having the same water and the same light-speed.

          Bwah, imperial is better:
          One liter = "The volume of the brain-substance you easily can scrape out with some residues left in the skull." ;D

      • by Goaway ( 82658 )

        This was the definition for a few years in the eighteenth century, before it was quickly changed.

        It's such a bad definition, it was not worthy using even back then.

    • by eyenot ( 102141 )

      (people, my point was that if the universe is contracting or expanding, something as co-involved as Planck's constant could easily change and we wouldn't be able to measure it as all of our measuring devices and things they're measuring would be contracting or expanding simultaneously. sheesh. how i got downvoted to 0 on a subject that sprang so much discussion is typical slashdot and yet completely beyond me.)

  • by penguinoid ( 724646 ) on Wednesday February 24, 2016 @03:30AM (#51573249) Homepage Journal

    This is a massive development.

    • by aliquis ( 678370 )

      This is a massive development.

      So low:

      This announcement came down like a ton of bricks on the physics department.

    • by AmiMoJo ( 196126 )

      It's hard to underestimate the gravity of this weighty decision.

    • by Falos ( 2905315 )
      There it is again! "Heavy"! Why is everything heavy? Has something gone wrong with the Earth's gravitational pull in the future??
  • by worf_mo ( 193770 ) on Wednesday February 24, 2016 @03:34AM (#51573259)

    Weight Watchers International weighted in on the discussion requesting the new kg to be defined at twice the weight of the current kg ("Yes Sandy, I lost half of my weight in the blink of an eye!"), while grocers all over the planet petitioned to divide the current value by four.

  • by SharpFang ( 651121 ) on Wednesday February 24, 2016 @04:12AM (#51573365) Homepage Journal

    All kilograms are equal

    but some are more equal than others.

  • by thisisauniqueid ( 825395 ) on Wednesday February 24, 2016 @04:43AM (#51573447)
    I bet they're going to change the definition from 1 kg = 1024 grams to 1 kg = 1000 grams. And we'll probably have to write "kig" too to make sure we don't get confused about the old definition.
    • I bet they're going to change the definition from 1 kg = 1024 grams to 1 kg = 1000 grams. And we'll probably have to write "kig" too to make sure we don't get confused about the old definition.

      Was gonna mod this "Funny" but unfortunately there choice is via a drop-down list which confuse CMD people like myself. To make it worse there's no "undo". So I'll just post to take any mods away. Boo.

      • Use the D1 discussion system. It still works just fine, and it has both a dropdown and a "confirm" button. Find it in your account options under 'Discussion'.

    • If it were really about marketing, laptop manufacturers should have started using 1024 g = 1 kg so they could say their laptops were lighter.
  • The unit formerly known as the "pound" shall now be called the "kilogram". The prices will be adjusted accordingly.

  • So it'll be 999.000000001 grams or something?

    Maybe they'll redefine gram one of these days

  • ...the Imperial system of weights and measures is bad because it's "arbitrary".

  • by Anonymous Coward

    The US approach is silly. The apparatus must be isolated from the environment to such a degree that it is impractical. Oner must monitor and dissuade wildlife a quarter mile away from the apparatus to get useful measurements. In essence the US approach is not to make a standard but a very impractical scale. The German approach is not so touchy. There is nonsense about only one Australian guy being able to form the spherical reference but that is ridiculous cult of personality. The German approach is both de

    • you are missing the point, these experiments are being done to ascertain the superiority of one approach over the other. You are trying to argue without lack of experimental support, but those involved in this test are doing things scientifically.

  • by rossdee ( 243626 ) on Wednesday February 24, 2016 @10:51AM (#51574681)

    It should be defined by Pope Francis
    He used to be a chemist, and is infallible.

    • Except that his kilogram will differ from the Orthodox kilogram by some obscure Aristotelian philosophical disagreement, every Protestant scientist will feel obliged to determine his or her own kilogram from personal inspiration, and it'll get even worse as we get to other religions. The Muslims will want it defined in terms of Muhammed's body parts, and the Buddhists will insist it's all illusory anyway.

  • It's more than 2.2 times better..

Your program is sick! Shoot it and put it out of its memory.