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Science

The Changing Definition Of 'Kilogram' 964

Posted by timothy
from the jenny-craig-kilograms dept.
DrLudicrous writes "The NYTimes is reporting that the platinum-iridium standard mass for the kilogram is shedding at an appreciable rate -- at least compared to other reference masses. The Pt-Ir cylinder is kept in France, and measured annually, and the slight discrepancy is important because the kg is an SI base unit- thus other quantities such as the Volt are based on it. A new standard is being sought- the two frontrunners are counting the number of atoms in a perfectly spherical single crystal of silicon, and another technique uses a device known as the Watt balance."
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The Changing Definition Of 'Kilogram'

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  • Kilogram? (Score:5, Funny)

    by ihatewinXP (638000) on Tuesday May 27, 2003 @12:34AM (#6044681)
    Hey I live in America you insensitive clod! (but then again I alawys want to know how much they are lifting on Strongman Competition).
    • by PhlegmMaster (596165) on Tuesday May 27, 2003 @12:36AM (#6044692)
      Then maybe america should move out of the dark ages sometime.
      • Re:Kilogram? (Score:5, Informative)

        by el-spectre (668104) on Tuesday May 27, 2003 @12:45AM (#6044760) Journal
        It's not a matter of dark ages, it's a matter of infrastructure... while not the largest country in the world (the US is probably third or fourth, I'm not sure), we have by far the most technological infrastructure. It is not feasible to change all that in a short period of time.

        A friend is in construction, and guestimates that it will take over 100 years to replace all failing/obsolete tech with the versions in metric equivalents. It just does not make any economic sense to replace a set of, say, water pipes with the metric standard if the current ones will last 20 years. It'll have to be a gradual thing.

        Just to be difficult, though, I'd mention that most construction is done in 'tenths of feet', even the surveying equipment is marked this way. Has nothing to do with the metric system, it just makes the math easier...
        • Re:Kilogram? (Score:5, Insightful)

          by UniverseIsADoughnut (170909) on Tuesday May 27, 2003 @02:07AM (#6045202)
          " It's not a matter of dark ages, it's a matter of infrastructure... while not the largest country in the world (the US is probably third or fourth, I'm not sure), we have by far the most technological infrastructure. It is not feasible to change all that in a short period of time."

          Bingo! this is why the US has been working on the process so long. Granted the push hasn't been very great but it's happening. If you're a country of a few million and only are the size of a small new england state, the change is pretty cheap and easy. When your huge, there is a massive infastructure change cost. and trying to re-wire 300 million peoples brains to a new way takes a lot more work.

          I think places like Europe were also helped by war. They had to rebuild and start new with so much. So it was a perfect time to start fresh. The US is a pile of legacy ways. And nothing happens to change them.

          With that said I wish we would try harder to convert. Get a dual system going now and run it for 20 years. let people adjust. Teach school in 95% SI ( only enough english units stuff so the comprehend them).
          • Re:Kilogram? (Score:5, Insightful)

            by radish (98371) on Tuesday May 27, 2003 @03:11AM (#6045471) Homepage
            You do know the metric system is many hundred of years old don't you? In fact it's older than your country. The point is the US has had 200 years and they haven't even started the process. There's nothing saying you can't run in parallel - the UK has been doing so for years. It's absurd to say you have to rip out all the imperial pipes and replace them - you just have to keep 2 sets of tools around until those old pipes get replaced naturally. It really isn't hard, it's just the US can't be bothered.
            • Re:Kilogram? (Score:4, Insightful)

              by Dun Malg (230075) on Tuesday May 27, 2003 @10:35AM (#6047692) Homepage
              You do know the metric system is many hundred of years old don't you? In fact it's older than your country.

              As the poster below me said, you are quite wrong. [unc.edu]

              The point is the US has had 200 years and they haven't even started the process. There's nothing saying you can't run in parallel - the UK has been doing so for years. It's absurd to say you have to rip out all the imperial pipes and replace them - you just have to keep 2 sets of tools around until those old pipes get replaced naturally.

              No, you really don't get it at all. As it happens, most people who have tools ALREADY have the two sets of tools. What makes switching difficult is having two sets of PARTS. It's all well and good to say "from now on all parts/raw materials will be measured using the metric system", but what does one do about, say, electrical conduit fittings? There is an UNGODLY amount of installed bass there which is already in inches and adding on to it would require a complicated system of adapters and a complete recalculation of wire capacity. Name any other construction trade and you run into the same thing. How do you add on to an inches-and-feet house with metric lumber? What size metric ducting do I buy to add to a 12-inch heating plenum? Not saying that it can't be done, but there's a lot more to it than "keep[ing] 2 sets of tools".

              • Re:Kilogram? (Score:5, Interesting)

                by radish (98371) on Tuesday May 27, 2003 @10:48AM (#6047804) Homepage

                I do get it. This already happens in the UK, it's not a problem at all. We have lots of houses which are older than the metric system (and the USA for that matter). They use imperial stuff. We have lots of new houses - they use metric. And yet I can still call a plumber and he can figure out how to fix my pipe, and my electrician is able to fix a light. Amazing.

                If there was any will to do it you'd do it, which indicates there's no will. Which is fine, I don't give a toss what you measure your wooden houses in, but don't come over all "it's too haaaaaard" - you sound like a whinging kid.
      • -Then maybe america should move out of the dark ages sometime.-

        But honestly its (the kilo) as arbitrtary as any other unit we have come up with to describe reality (red, one second, a kilometer) so why rewrite the bible as it were and change something like this?
        I know the implications could be staggering, but why not chalk it up to having a leap year and other silly things about our units of measurment.

        • by Anonymous Coward on Tuesday May 27, 2003 @01:01AM (#6044851)
          It's not the arbitrariness, but the fact that metric is a decimal system.

          The only countries left that don't use metric are the US and Bhutan. Bhutan is a fundamentalist islamic country that doesn't even have any phones yet. I guess we can see what the US' technical level is.
      • by Tumbleweed (3706) on Tuesday May 27, 2003 @12:57AM (#6044827)
        > Then maybe america should move out of the dark ages sometime.

        Yeah, tell it to the Queen.
      • by Spooky Possum (80044) on Tuesday May 27, 2003 @01:23AM (#6044995)
        Consider the facts:

        Congress authorised the use of the metric system in 1866.

        The US signed the Treaty of the Meter in 1875.

        Congress passed the Metric Conversion Act in 1975.

        So clearly the US *is* on the metric system :).
      • by Anonymous Coward on Tuesday May 27, 2003 @01:46AM (#6045114)
        Moving to the metric system... inch by inch.
      • Re:Kilogram? (Score:5, Interesting)

        by sphealey (2855) on Tuesday May 27, 2003 @09:09AM (#6046883)
        Then maybe america should move out of the dark ages sometime.
        Funny how when the topic is software or food supplies, everyone jumps in with comments about the dangers of monoculture and the value of diversity in supply, but when the topic is the metric system there can be no deviation from the ONE TRUE FAITH.

        Personally, having gone through school at a time when the US was considering a change, and having spent some time in Europe, I have no problem with the metric system. It is more convenient from some tasks, particularly in the chem lab.

        But there is nothing inherently superior about a measurement system based on powers of 10. For many tasks, such as woodworking, metric measurements are far more difficult to work with than inches and 1/16th. In fact I would argue that the most "natural" base for a measurement system is 12 as it is evenly divisible by 2, 3, and 4; whereras base 10 is only divisible by 2 and 5. Thirds and fourths are very common divisions of stuff; fifths are not, so a base 12 system is more user-friendly.

        That's my 0.02 euro anyway.

        sPh

      • by squidfood (149212)
        ...move out of the dark ages sometime.

        America? Bah! All you primates should move out of the dark ages sometime. Base-12 is where it's at.

        We'll take our easily divisible Freedom Inches (tm) any day, thank you.

    • Re:Kilogram? (Score:4, Insightful)

      by LX.onesizebigger (323649) on Tuesday May 27, 2003 @12:40AM (#6044724) Homepage

      And since the inf^H^Hmperior^H^Hal system is now defined in terms of the metric system (an inch is 2.54 cm), your strange units change as well.

    • by AftanGustur (7715) on Tuesday May 27, 2003 @02:47AM (#6045375) Homepage


      Hey I live in America you insensitive clod!

      Ok, so for you it's "FreedomGram" then.

  • by craenor (623901) on Tuesday May 27, 2003 @12:35AM (#6044684) Homepage
    Everytime she steps on the scales...I would tell you what it was defined as last week, but kids may be reading this.
  • i'm not gaining weight, the kilogram is losing mass... so really, i stay the same weight, and they need more units to weigh me ;-)
  • I'm surprised that no one has tried until now to create a standard for the kilogram that could be repeated easily like atomic measurement of the length of a meter and the computation of a second of time based on the resonance frequency of a caesium atom.

    If they succeed, we can get a reference standard for a kilogram that can be easily generated for scientific research.
  • Solution? (Score:5, Funny)

    by The_dev0 (520916) <hookerbot5000.gmail@com> on Tuesday May 27, 2003 @12:38AM (#6044715) Homepage Journal
    Why couldn't they just take it down the shops and measure it against, say, 1kg of carrots or a kg of sugar?
  • Look here... (Score:4, Informative)

    by switched4OSX (668686) on Tuesday May 27, 2003 @12:40AM (#6044725)
    Here is a site that gives some reasons why the are thinking of replacing the standard: http://physics.nist.gov/News/TechBeat/9501beat.htm l. No registration necessary
  • Counting Si (Score:5, Interesting)

    by brokenbeaker (267889) on Tuesday May 27, 2003 @12:40AM (#6044728)
    The problem with the single crystal of silicon method, a few years ago, was that there were all these lattice vacany defects cropping up. The formation of such point vacancies is so entropically favoured that I don't think they can ever eliminate them...
    • by porp (24384) on Tuesday May 27, 2003 @12:53AM (#6044806)
      I think I can speak for everyone and say

      HUH?

      porp
    • Re:Counting Si (Score:5, Informative)

      by dhovis (303725) * on Tuesday May 27, 2003 @01:30AM (#6045033)

      Vacancies are not necessarily a problem. As you say, vacancies are entropically favored, but there is also a formation energy associated with a vacancy. So thermodynamics tells us there will be a balance between the energy required to create a vacancy with the entropy gained by creating one.

      Thus, there is an equilibrium number of vacancies in any crystal. As long as you know what the equilibrium value is for a given temperature and you maintain that temperature, then you will also know how many vacant sites you will have on the crystal lattice. I don't have any of my texts handy, but I'm sure someone can chime in with the numbers for silicon.

      To sum up. All crystals will have vacancies because vacancies are thermodynamically favored. However, the number of vacancies will tend towards an equilibrium value which allows them to be accounted for.

      • Re:Counting Si (Score:5, Informative)

        by neodymium (411811) on Tuesday May 27, 2003 @03:30AM (#6045523) Homepage
        If you really would try to build such a crystal, vacanies could very well be the problem. As you said, there is an equilibrium value of defects in any crystal. This equilibrium value is temperature dependant with a exp(-Eform/kT) law, where Eform is the formation enthalpy. High temperature means high rate of defects.

        Si single crystals are usually prepared at very high temperatures out of molten Silicon (1414C, Czochralsky method). Essentially, this will lead to a freezing of the defect structure at temperatures close to the melting point, because the lattice reorientation kinetics (point diffusion) also are thermally activated.

        You would have to temper the crystal for _very_ long times at temperatures of i.e. 300C to get a thermal equilibrium of defects at this temperature. These times could be >>years !

  • by HaloZero (610207) <protodeka.gmail@com> on Tuesday May 27, 2003 @12:43AM (#6044744) Homepage
    It's not my ass, it's just that the units are getting incrementally smaller. Ho ho! It's not me. *dances*

    Damned inreliable measure standards. *shakes fist*
  • by LX.onesizebigger (323649) on Tuesday May 27, 2003 @12:45AM (#6044759) Homepage

    My question is, how do they measure it? Using a non-decaying meter stick? How do you measure the definition of a measure?

  • by Midajo (654520) on Tuesday May 27, 2003 @12:47AM (#6044773)
    Scientists Struggling to Make the Kilogram Right Again
    By OTTO POHL


    RAUNSCHWEIG, Germany -- In these girth-conscious times, even weight itself has weight issues. The kilogram is getting lighter, scientists say, sowing potential confusion over a range of scientific endeavor.

    The kilogram is defined by a platinum-iridium cylinder, cast in England in 1889. No one knows why it is shedding weight, at least in comparison with other reference weights, but the change has spurred an international search for a more stable definition.

    "It's certainly not helpful to have a standard that keeps changing," says Peter Becker, a scientist at the Federal Standards Laboratory here, an institution of 1,500 scientists dedicated entirely to improving the ability to measure things precisely.

    Even the apparent change of 50 micrograms in the kilogram -- less than the weight of a grain of salt -- is enough to distort careful scientific calculations.

    Dr. Becker is leading a team of international researchers seeking to redefine the kilogram as a number of atoms of a selected element. Other scientists, including researchers at the National Institute of Standards and Technology in Washington, are developing a competing technology to define the kilogram using a complex mechanism known as the watt balance.

    The final recommendation will be made by the International Committee on Weights and Measures, a body created by international treaty in 1875. The agency guards the international reference kilogram and keeps it in a heavily guarded safe in a château outside Paris. It is visited once a year, under heavy security, by the only three people to have keys to the safe. The weight change has been noted on the occasions it has been removed for measurement.

    "It's part ceremony and part obligation," Dr. Richard Davis, head of the mass section at the research arm of the international committee.

    "You'd have to amend the treaty if you didn't do it this way."

    That ceremony has become a little sorrowful as the guest of honor appears to be, on a microscopic level at least, wasting away.

    The race is already well under way to determine a new standard, although at a measured pace, since creating reliable measurements is such painstaking work.

    The kilogram is the only one of the seven base units of measurement that still retain its 19th-century definition. Over the years, scientists have redefined units like the meter (first based on the earth's circumference) and the second (conceived as a fraction of a day). The meter is now the distance light travels in one-299,792,458th of a second, and a second is the time it takes for a cesium atom to vibrate 9,192,631,770 times. Each can be measured with remarkable precision, and, equally important, can be reproduced anywhere.

    The kilogram was conceived to be the mass of a liter of water, but accurately measuring a liter of water proved to be very difficult. Instead, an English goldsmith was hired to make a platinum-iridium cylinder that would be used to define the kilogram.

    One reason the kilogram has lagged behind the other units is that there has been no immediate practical benefit to increasing its precision. Nonetheless, the drift in the kilogram's weight carries over to other measurements. The volt, for example, is defined in terms of the kilogram, so a stable kilogram definition will allow the volt to be tied more closely to the base units of measure.

    A total of 80 copies of the reference kilogram have been created and distributed to signatories of the metric treaty. The sometimes colorful history of these small metal cylinders underscores how long the world has used the same definition of the kilogram.

    Some of the metal plugs were issued to countries that later vanished, including Serbia and the Dutch East Indies. The Japanese had to surrender theirs after World War II. Germany has acquired several weights, including the one issued to Bavaria in 1889 and the one that belonge
  • reproducibility (Score:5, Insightful)

    by nthomas (10354) on Tuesday May 27, 2003 @12:50AM (#6044793)
    Although it was mentioned in the article, I think it should be emphasized that the SI definition of the kilogram, unlike their definitions of the meter and second, cannot be reproduced -- or rather, reproduced exactly. This is quite important, as it is neccessary for the standards governing body in each country to have a very precise reference weight of their own.

    Since there is only one reference object for the kilogram, everything else is just a copy -- and even if it is a first generation copy, errors are bound to creep in.

    The redefinition of the kg is long overdue, mad props to the scientists working on this.

  • by SandmanWAIX (674838) on Tuesday May 27, 2003 @12:52AM (#6044801)
    nah .. they should throw out the whole kilogram concept and weigh everything according to a "library of congress". eg. that woman weighes 2.36 libraries of congress.
  • by Alien54 (180860) on Tuesday May 27, 2003 @12:55AM (#6044813) Journal
    I sort of like the idea of a universal unit of measure.

    One nominee that is amusing is to have the basic unit of distance based on the speed of light.

    One light nanosecond = roughly 11.1 inches, kinda close to a foot.

    I remember how Grace Hooper used to pass out wires that were that long, just to make the point.

    Any other nominees?

  • by DanThe1Man (46872) on Tuesday May 27, 2003 @12:56AM (#6044819)
    And all this time I just thought I was just getting used to cocaine.
  • by Helpadingoatemybaby (629248) on Tuesday May 27, 2003 @12:58AM (#6044832)
    give me imperial measurements any day

    Darn right! After all, it's easy enough to convert fortnights to stone with a Mayan calendar.

    We're going to in the future eventually. It's inevitable.

    I know it's 60 firesticks per 100 Watts, and 3000 Volts per staticy tomcat, but it might just be easier if we all just jumped in and switched to metric 144%.

    I mean picture doing 100 on the highway! Wouldn't that be great? And dozens of future Mars landers would actually land on Mars, instead of digging ideal tree planting holes and landscaping future martian neighbourhoods. ("Zyphod! Incoming! It's the Americans!")

    No more two sets of wrenches and lost sockets! Now you can have one set of sockets with half the sockets missing, instead of two sets of sockets with half the sockets missing. And no more asking for an 5mm and trying to make a 1 3/4" fit, rounding off the edges and carving a perfect turkey slice off your hand and gushing gallons of blood. It would be litres, which is less.

    And you get to tell women that you, sir, are endowed with twenty-two centimeters of man!

    Of course, the loss of the 25 cent piece will be a negative, since we'll have to pay for everything in dimes. But it's worth it dammit.

    Seriously, we all know this is going to happen. When are we on board? Are we that stubborn?

  • by sprprsnmn (619113) on Tuesday May 27, 2003 @01:08AM (#6044898) Homepage Journal
    One kilogram is equal to the weight of 1/256th of a VW beetle! Simple as that! Silly French.
  • Why not use diamond? (Score:5, Interesting)

    by Jeremy Erwin (2054) on Tuesday May 27, 2003 @01:08AM (#6044899) Journal
    Is there any physical reason (other than that small matter of cost ) that crafting a new kilogram (or more likely, gram) out of diamond would not be an ideal solution?

    BTW, theNational Physical Institute [npl.co.uk] has a FAQ on its Pl-Ir standard kilo.
    • by addaon (41825) <addaon+slashdot.gmail@com> on Tuesday May 27, 2003 @02:23AM (#6045269)
      Diamond spontaneously decays into graphite... no mass change, I suppose, but it has different absorption of gasses from the air, and different density (matters if they measure mass through weight in an atmosphere). Gold is much more long-lasting.
    • by Jeremy Gray (223298) on Tuesday May 27, 2003 @02:57AM (#6045417)

      The same problems are still there, regardless of material. Changing the composition doesn't change the fact that there is only one standard in only one laboratory, that stray particles and cleaning will affect its mass upon measurement, and that the standard may be damaged in some way.

      The other solutions presented as candidates to replace the standard rely on invariant physical constants, i.e. Avogadro's number. Distance and time standards are already defined in this way, from the speed of light and the frequency of a two-state cesium transition in the microwave region.

      This shifts the accuracy of the standard from it's care and maintenance to the measurement of constants, with the added benefit of any appropriately equipped laboratory being able to measure the standard.

  • by djupedal (584558) on Tuesday May 27, 2003 @01:12AM (#6044924)
    The only known quantity of Unobtainium (UB238) has gone missing.

    The 1 kilo square block was being held in Brussels awaiting return to Brazil, where it was originally unearthed.

    It was determined that the physical stability of the material was being affected by being moved from it's original location, that of being south of the equator. Investigators are anxious to reclaim the material in hopes of stabalizing it's rumored flux in mass. The UB238 was being packaged for transit, when it suddenly dissapeared from the shipping room counter. The rumor that it had created, and subsequently fallen into, a 'portable black hole' was discounted by investigators on the scene.

    Once the Unobtainium is recovered, and returned to Brazil, it can be weighed and certified as a replacement for the Pt-Ir cylinder that is kept in France [slashdot.org], and measured annually, representing the kilo standard for the world.

    MPEG at 11.
  • by toxic666 (529648) on Tuesday May 27, 2003 @01:12AM (#6044929)
    It seems they should just reference the kilogram to a standard, such as x,xxx,xxx,xxx Si (28 isotope) atoms. This would eliminate the complications trying to build a standard, duplicate it and correct for earth's gravitational variations at the time and place of checking physical reference mass (not weight, to which the article alluded). Keep in mind the kilogram is a measure of mass, and not weight. That is why maintaining a physical standard requires correcting for gravity at the location's, time, elevation, tide, (add geophysical conditions, ad nauseum) of measurement.

    If we are maintaing a physical chunk of alloy as the standard, it's time to decide on a more precise measurement, like we did with the meter long ago.
  • by Compenguin (175952) on Tuesday May 27, 2003 @01:26AM (#6045003)
    What i've never understood is since the kilogram is the base unit why didn't they just call it the gram?
    • by amorsen (7485) <benny+slashdot@amorsen.dk> on Tuesday May 27, 2003 @06:29AM (#6046136)
      At first the gram was the base unit. However, try deriving the other units from that, and you will see that units like Volt come out with inconvenient sizes for everyday measurements. So they changed to the kilogram without inventing a new name for it. This is quite unfortunate for several reasons, including the fact that everyone abbreviates it to just kilo. Also, what do you call 1000 kg? A kilokilogram? A megagram? No: A (metric) ton.

      Incidentally, there will always be some units that end up with inconvenient sizes. Try going to your local electronics store and asking for a 1F capacitor.

  • by Dhrakar (32366) on Tuesday May 27, 2003 @01:27AM (#6045016)
    The posted article, while interesting, is wrong about the volt being based on the Kilogram. Since about 1990, the volt is defined to be the voltage applied to a Josephson junction that produces a frequency of 483,597.9 GHz. This new standard was implemented in order to get away from relying on 'artifact' standards (such as the Kg cylinder). One quick source page on Josephson junctions (which completely revolutionized the field of Metrology back when I was a calibration tech in the AF) is:
    http://hyperphysics.phy-astr.gsu.edu/hbase/solids/ squid.html
    If I recall correctly, the eventual goal of the international standards organization was to find ways to define everything in terms of frequency/time since we can measure time so accurately/precisely.
  • huzzah! (Score:5, Funny)

    by madmarcel (610409) on Tuesday May 27, 2003 @01:40AM (#6045077)
    So I now weigh 75kg...give or take a bit :o

    Wait till I tell my fiance that her weight
    fluctuates on a weekly basis!
  • by SEWilco (27983) on Tuesday May 27, 2003 @01:41AM (#6045081) Journal
    a perfectly spherical single crystal

    These pseudoscience concepts are getting out of hand.
    I don't think we need "feel-good" physics.
    Now they want to base a standard on a crystal ball?

  • by jmoore2333 (592784) on Tuesday May 27, 2003 @01:57AM (#6045170)
    I've been waiting a while to tell my high school chemistry teacher that a Kilo is 1024 of anything, and I do deserve that A. ~JM
  • by Qender (318699) on Tuesday May 27, 2003 @02:21AM (#6045261) Homepage Journal
    "'It's certainly not helpful to have a standard that keeps changing,' says Peter Becker, a scientist at the Federal Standards Laboratory..."

    Wow, someone should tell the computer industry that.

    "Some of the metal plugs were issued to countries that later vanished, including Serbia and the Dutch East Indies. The Japanese had to surrender theirs after World War II. Germany has acquired several weights, including the one issued to Bavaria in 1889 and the one that belonged to East Germany."

    SURRENDER YOUR KILOGRAM!
  • by Dr. Spork (142693) on Tuesday May 27, 2003 @02:37AM (#6045330)
    We actually have a metric definition of mass that doesn't depend on anything in Paris. By convention, Avogadro's number of Carbon 12 atoms has a mass of 12 grams. This will remain true no matter what happens in Paris.

    However, maybe I'm implicitly assuming that we have settled exactly what Avogadro's number is. But if we haven't, if we are still holding out for more and more accurate measurements of Avogadro's number, then yeah, we need to really nail down what a kilogram is. But that seems weird to me, because Avogadro's number has no units. It's just a count of atoms, playing the same grammatical role as the word "dozen".

  • by stereoroid (234317) on Tuesday May 27, 2003 @03:53AM (#6045621) Homepage Journal
    I'm a Brit who grew up in South Africa, so I grew up Metric, and had to learn all about pounds etc. when I returned to the UK. (Ugh.) The thing that always bothered me about the Kilogram was: why was it a specific piece of metal, when the original design [www.bipm.fr] was based on the mass of a litre of pure water?

    Freezing water was a bad idea, since the volume of water changes as it freezes, and I'm sure I read that they switched to 20C. The litre is, of course, a cubic decimetre or 1/1000 of a cubic metre, and is thus derived from the standard metre.

    Whatever the reasons (practical?), the two standards were separated, but it's still quite easy to get a ballpark figure for the weights of fluids. Ten litres (2.624 gallons) of water weighs about ten kilograms (22.05 pounds). Some fluids will be less (gasoline), some more (beer, oils, mercury). There are other such shortcuts, too, so I ain't goin' back.

    PS: If you Yanks are wondering why it's easier to get drunk in the UK, it's because a UK pint is 20% larger than a US pint. Standards are great - that's why we have so many of them...

  • by KingRamsis (595828) <kingramsis&gmail,com> on Tuesday May 27, 2003 @04:26AM (#6045762)
    he kilogram is shedding at an appreciable rate

    you mean I'm actually losing weight without doing diets or a workout !!
  • by verbatim (18390) on Tuesday May 27, 2003 @05:06AM (#6045895) Homepage
    one point twenty-one jigawatts?
    That's almost a bolt of lightning by degrading metric standards.

    On a more serious note, does the declining metre have anything to do with the rising Canadian dollar? And they [torontostar.com] say that Canada doesn't matter. Humbug, I say. :)
  • by pete-classic (75983) <hutnick@gmail.com> on Tuesday May 27, 2003 @08:04AM (#6046468) Homepage Journal
    Uh, could it have something to do with it being (partially) made of iridium?

    -Peter
  • Silly artifacts (Score:3, Insightful)

    by jabber01 (225154) on Tuesday May 27, 2003 @10:18AM (#6047513)
    IIRC, the kilogram is the last basic unit of measure still expressed in terms of an artifact, as opposed to though an observable phenomenon + mathematics.

    IM(H)O, we need to do away with this, because artifacts exist in only one place. They can be stolen, damaged, or suffer from flaws and natural processes like the one we're seeing right now.

    Of course, the flip side of having everything in terms of observable phenomena creates the problem of measurement, and making tools sensitive enough to do that work. Philosophically, the problem goes circular here, for how do you make a set of calibration weights for a scale, if you have to measure things to the atom first...

    But in practice, there is no problem, because the measurement technology exists, and we're talking about the "standard" or "reference" units here.

    Imagine having to calibrate a scale on Mars, or Alpha Centauri. Getting that artifact to the "job site", to make sure the scale is true, would be a bit of a chore.

    A kilogram should be expressed not in terms of the number of atoms in a particular crystal, but rather in terms of the mass of X moles of standard substance Y.

    We can assume (if we can not, then all else is a lie) that a particular isotope of a particular element will have the same mass eveywhere in the Universe. We know the number of atoms in a mole. Problem solved.
  • by CERDIP (648784) on Tuesday May 27, 2003 @11:56AM (#6048513)
    The standard 1 kg block should be replaced by the 1 kg Christmas Fruit Cake. As everyone knows, it is indestructible, and only one exists in the entire world (people just keep mailing it around to each other every year).
  • The Volt (Score:3, Informative)

    by BluesGeek (160887) on Tuesday May 27, 2003 @03:11PM (#6050372)
    Just as a minor correction ... the volt is no longer defined in terms of the kg. The international definition of 1 Volt is now defined in terms of the "Josephson Effect" and is an effect observed in superconducting materials that are interupted by a normal metal.

    It turns out, that even without an applied voltage, there is still a current in the system, and after a voltage is applied, the current oscillates at a very predicable rate. Thus, the volt is now defined as the potential required to give a specific number of current osciallations in a Josephson Junction.

    Nit-pickey I know, but maybe of interest.
  • by Captain_Stupendous (473242) on Tuesday May 27, 2003 @03:18PM (#6050427) Homepage
    The watt balance solution seems to be linking the Kilogram (mass) with force (weight). This is not entirely desirable, since something that masses a kilo on earth will still mass a kilo in space, or on the moon, or on jupiter. It's mass doesn't change, only it's weight. The Watt balance then, would not only be impractical (imagine having to construct a "3-story structure" every time you want to accurately weight something?), but downright useless for many aerospace applications. Any system of measurement that's dependant on the phase of the moon for it's accuracy should immediately be discounted, in my opinion...

"But this one goes to eleven." -- Nigel Tufnel

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