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WorldWeird: Precision spheres in push to re-define kilogram

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      CommentAuthorWillow Bl00
    • CommentTimeJul 15th 2009 edited
     (6376.1)
    sphere

    The kilogram, the unit of mass in the International System (SI), is one of seven base units used in science, commerce and everyday life. It is the only one still defined by a physical object.
    A kilogram is currently defined as: ‘that mass which is equal to the International Prototype’. The International Prototype being a cylinder of platinum and iridium kept in a vault at the International Bureau of Weights and Measures (BIPM) near Paris, France.
    All the other SI units are defined in terms of a fundamental constant of nature so that anyone, anywhere can reproduce them and they don't change over time.
    Around the world, scientists are working on new ways to define the kilogram.
    Background to the Avogadro project
    The international scientific community, under the auspices of the BIPM, decided to focus on two methods, and CSIRO was involved in one of them.
    Known as the Avogadro Project, the plan is to bring together enough atoms of one substance – silicon – to make a kilo.


    [via Make and csiro]

    So my awesome uncle, who's been involved with this project, also tells me that what's extra cool about this is that the more refined silicon is, the more efficient it is at solar power. Each additional nine of purity (99.9% is three nines, 99.999% is five) pulls an additional percentage point out of the energy hitting it. And in order to have a perfect sphere you also have to have only that one element present because of the way the atoms bond. So perfect shapes are leading to perfect harvesting of energy.

    (edited for formatting)
  2.  (6376.2)
    The quest for the perfect sphere.
    How very Plato of them!
  3.  (6376.3)
    All around the world, a kilo is a measure.
    A kilo is one thousand grams, it's easy to remember.

    Seriously though, the extra info relating to solar panels is cool. I didn't actually know that "in order to have a perfect sphere you also have to have only that one element present because of the way the atoms bond". Makes sense, but I had never heard that piece of information before.
  4.  (6376.4)
    It's also very pretty to look at.
  5.  (6376.5)
    I do remember that spheres that had a ridiculous amount of smoothness and curvature (10^-18 millimeters) were supposed to be used to detect gravity waves, but I don't know if they ever made those or not.
    • CommentAuthor/
    • CommentTimeJul 16th 2009
     (6376.6)
    So does this indicate that perfect symmetry leads to perfect thought/energy, therefore possibly perfect action?
  7.  (6376.7)
    So does this indicate that perfect symmetry leads to perfect thought/energy, therefore possibly perfect action?
    Plato's metaphysical mumbo-jumbo is actually kinda true? Well, I'll be the descendant of an ape-like creature!
    • CommentAuthor/
    • CommentTimeJul 16th 2009
     (6376.8)
    Who's this Plato guy? I got that from a Bruce Lee book...
  9.  (6376.9)
    Who's this Plato guy? I got that from a Bruce Lee book...
    Never mind. I talk like a fag and my shit's all retarded.
    • CommentAuthor/
    • CommentTimeJul 16th 2009
     (6376.10)
    Don't you just hate it when that happens?
    •  
      CommentAuthorsillypunk
    • CommentTimeJul 16th 2009
     (6376.11)
    that is so shiny....

    also: fun fact. the meridian expedition that set out just prior to the french revolution to come up with the standard meter, didn't actually become the standard for the meter. as you were.
  12.  (6376.12)
    Don't you just hate it when that happens?
    I've been told that there are plenty of 'tards out there living really kick ass lives. My doctor's first wife was 'tarded. She's a pilot now.
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      CommentAuthorJon Wake
    • CommentTimeJul 16th 2009
     (6376.13)
    Call me old fashioned, but I like my units of measurement to be based on something a little less arbitrary. If the length of the King's forearm was good enough to build the pyramids, its good enough to design a nanomachine with.
  14.  (6376.14)
    Call me old fashioned, but I like my units of measurement to be based on something a little less arbitrary. If the length of the King's forearm was good enough to build the pyramids, its good enough to design a nanomachine with.
    Ironically enough, the Imperial units of measurement have been officially defined using meters and kilograms for over 100 years now.
    •  
      CommentAuthorJon Wake
    • CommentTimeJul 16th 2009
     (6376.15)
    My car gets eighty leagues and a cubit and that's the way I likes it.
    •  
      CommentAuthormister hex
    • CommentTimeJul 16th 2009
     (6376.16)
    @ Jon Wake - If you empty the trunk of all non-essentials, you might get another furlong and a span.
  17.  (6376.17)
    I was raised to measure everything in aams and that is how I'll die.

    Likely of wine poisoning.
    •  
      CommentAuthortim12s
    • CommentTimeJul 16th 2009
     (6376.18)
    I'm surprised no-one's mentioned that the entire coke industry might be up in arms over this.
    • CommentAuthorKosmopolit
    • CommentTimeJul 17th 2009
     (6376.19)
    There are four basic units in the SI system: mass, length; time and energy.

    All the other measurements are derived from them: so velocity in length by time.

    The problem up until now has been that the measurement of the other basic units were defined much more accurately than the kilogram so the accuracy of experiments was limited by the uncertainty in the weight measurements.

    Now the kilogram can be defined nearly as precisely as the other units.
  20.  (6376.20)
    The kilogram is already defined precisely. It is defined as the mass of the Prototype.

    Precision is not the goal. The kilogram lags behind the other six SI base units (meter, mole, second, kelvin, ampere, candela) in being assigned a definition based on a fundamental physical property. The other units are defined in terms of universal and replicable points of arbitrarily agreed-upon physical conditions. For example, the kilogram was upon conception defined as "the mass of a cubic decimeter of water at 4 degrees C", a replicable physical condition, but one which could not be replicated with suitable consistency. So the Prototype was created (and later replaced) as a functional replacement. Although the Prototype itself changes in real mass due to air-contamination (and attempted compensation by "cleaning", which makes it temporarily more unstable), a kilogram is always defined as what the mass of the Prototype is as of last measurement. The silicon sphere is an attempt to revert the kilogram back to a universal property definition. What matters is proving replicability (not a word).

    These definitions are formed by agreement (most have been worked out backwards from less universal original definitions) and they can be changed by the Weirdos Who Decide This Stuff when better, more accurately replicable definitions come along. Perfect concistency of replication is not the goal. There is always a measure of innacuracy in actually executing SI definitions: they are all only nearly-accurate in practice. But no one has yet given the kilogram a new system that is as acceptably nearly-accurate as the others.

    Example of acceptable inaccuracy: the kelvin (equal in per unit scale to the degree Centigrade) is currently defined as 1/273.16th of the absolute temperature of water at its triple point. The triple point of any substance is a factor of pressure and temperature, and in actual practice the temperature in a lab setting will vary according to all the Back-of-Jeff-Goldblum's-Hand shit that goes on: accurate reproduction of the required pressure, smoothness of the surface of the container, and the purity and isotopic makeup of the substance measured. Triple-point thermometer calibrations thus require 99.9999% purity of substance and, in the case of water, a defined isotopic ratio called Vienna Standard Mean Ocean Water (I am not making this shit up). But as long as these requirements are met, the results are extremely consistent, and a kelvin can be calculated from scratch in any lab setting.

    The kilogram's current "definition" is thus as or more precise in physical determination as any other SI Base unit. But it fucks shit up, in two ways. First, it is not replicable from scratch, so instrument calibrations are based upon numbered prototype-copies, which themselves change mass based on air-absorption and wear-from-use (since they are brought out of storage more routinely), and all do so at different rates than the Prototype, and thus are employed with qualifiers: a kilogram is this replica, K20, +?39 µg -- etc. Second, many other unit definitions have conditions based on mass, including one of the SI Base Units, the candela (luminosity), which is defined as a factor of watts, which are defined as a factor of newtons, which are defined as a factor of kilograms: and the kilogram equals an object that changes in mass over time.

    Thus, sexy silicone balls.

    Disclaimer: I may have here written some erroneous details; I don't work with science and this essay is just the result of slumming-it with Wikipedia.

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