Dear Mike, In the past the BIPM has always gone for exactly the same accuracy but with highly increased precision.
This means that the amount remained exactly the same while the range between the highest and lowest measurements were diminished usually remarkably. Another idea that the BIPM has encouraged is that the new definitions should be able to be recreated anywhere in the world. This is already done in the case of length measurements. Any country can use the definition of the metre to check whether length measuring equipment is accurate and is precise within the necessary range. You might like to start at: http://www.bipm.fr/en/scientific/length/former_prototype.html to get a feel for the way measuring standards have been dealt with previously. Cheers, Pat Naughtin PO Box 305 Belmont 3216 Geelong, Australia 61 3 5241 2008 Pat Naughtin is manager of http://www.metricationmatters.com an internet website that focuses on the many issues, methods and processes that individuals, groups, companies, and nations use when upgrading to the metric system. Contact Pat Naughtin at [EMAIL PROTECTED] On 2007 06 19 3:28 PM, "Mike Millet" <[EMAIL PROTECTED]> wrote: > So how will this affect all the stuff that is currently measured in kilos? > > Will they all have to redefine the scales and such and have a "new standard"? > On a digital scale this wouldn't be a problem as you could always just update > it and have a new value. Or will it be like the changes in the meter and other > measures have been where it's so small of a change there is no need for any > real recalibration? > > Mike > > > On 6/18/07, Pat Naughtin <[EMAIL PROTECTED]> wrote: >> Dear All, >> >> Here are two references to articles articles about the possibility of a new >> kilogram. The second reference is followed by the full story in case the >> newspapers have taken down the links to the references. >> >> http://www.theage.com.au/news/national/perfect-silicon-sphere-to-redefine-the >> -kilogram/2007/06/14/1181414466901.html >> >> http://www.smh.com.au/news/science/its-a-grind-finding-the-perfect-pair/2007/ >> 06/14/1181414469834.html >> >> Cheers, >> >> Pat Naughtin >> PO Box 305 Belmont 3216 >> Geelong, Australia >> 61 3 5241 2008 >> >> Pat Naughtin is manager of http://www.metricationmatters.com >> <http://www.metricationmatters.com/> an internet website that focuses on the >> many issues, methods and processes that individuals, groups, companies, and >> nations use when upgrading to the metric system. Contact Pat Naughtin at >> [EMAIL PROTECTED] >> >> >> It's a grind finding the perfect pair >> >> Richard Macey >> June 15, 2007 >> THEY will be the roundest balls on Earth. Sydney engineers and scientists are >> about to begin work on what may become the world's new definition of the >> kilogram. >> Since 1889 a bar of platinum and iridium, called the International Prototype >> and stored in a French vault, has served as the kilogram's global standard. >> But it is no longer considered satisfactory, and the International Bureau of >> Weights and Measures has been searching for better ideas. One involves using >> a near-perfect sphere made from a single crystal of pure silicon, a stable >> element. >> Just such a crystal will be delivered today to the CSIRO's Australian Centre >> for Precision Optics at Lindfield. >> Made by Russia and Germany, the crystal, which will arrive in two pieces, >> took three years to produce. With the help of the National Measurement >> Institute, which shares the Lindfield site, the CSIRO will grind and polish >> them, fashioning two gleaming 93-millimetre balls. >> Each will take 12 weeks to complete. From the bottom of their deepest valleys >> to the top of their tallest peaks will be just 35 millionths of a millimetre. >> "There is no doubt they will be the roundest objects in the world," Walter >> Giardini, project leader at the National Measurement Institute, said >> yesterday. Imaging instruments magnifying 180,000 times, making seemingly >> smooth spheres "look like potatoes", will be used to detect rough spots. >> A CSIRO team led by Achim Leistner has turned out at least a dozen >> near-perfect silicon balls since the early 1990s. The two new spheres will be >> even better. The earlier versions were made from natural silicon and >> consisted of three different silicon isotopes, all with their own atomic >> weights. As the new crystal is made from just one, silicon-28, scientists >> will be able to more accurately measure the ball's atomic weights. >> The CSIRO's Lindfield centre was "the only place in the world that has ever >> made objects so round", said Mr Giardini. >> Said Katie Green, a CSIRO optical engineer: "We are trying to make them to a >> certain roundness, and certain diameter, which correlates to a certain mass." >> Knowing the weight of one silicon atom, "we will know how many atoms there >> are in the sphere". >> Added Mr Giardini: "We are trying for can accuracy of two parts in one >> hundred million, about 10 times better." >> Between 1880 and 1980 the weight difference between the world's existing >> kilogram standard and several identical cylinders of the same age changed by >> up to 70 micrograms, thanks to moisture, corrosion and contamination. >> "If we don't believe the standard is stable," said Mr Giardini, "we don't >> have a stable standard for mass." >> > >
