The proposal which will be put to the CGPM late next year is that Planck constant and the Avagadro number will both be defined as an having an exact value and that the kilogram and mole will be back-calculated from those definitions, in much the same way as the speed of light is deemed to have an exact value and the metre is calculated form that. For a fuller description, http://en.wikipedia.org/wiki/Proposed_redefinition_of_SI_base_units.
From: owner-u...@colostate.edu [mailto:owner-u...@colostate.edu] On Behalf Of mechtly, eugene a Sent: 08 June 2013 19:41 To: U.S. Metric Association Cc: mechtly, eugene a Subject: [USMA:52898] RE: World's Roundest Object! - YouTube The sphere of silicon 28 is only an intermediate step to "calculating" the number of atoms inside the sphere of precisely measured diameter, and precisely calculated volume. The precise number of atoms inside this volume would then *correct* (refine) the numerical value of Avagadro's Number which would then lead to a more direct redefinition of the kilogram. The redefinition would then *become* independent of the artifact itself which, of no further use, might be placed in a museum to gather dust. A decision on the choice of the silicon sphere *or* the watt-balance is forecast for the next meeting of the CGPM in 2014. There seems to be a preference by the experts at this moment for the watt-balance. Uncertainties in replication of experimental results is still delaying a clear and unambiguous choice. There is *no prospect* that both will be chosen to establish "two standards" simultaneously for a redefinition of the kilogram. _____ From: Kilopascal [kilopas...@cox.net] Sent: Saturday, June 08, 2013 10:58 AM To: U.S. Metric Association Subject: Re: World's Roundest Object! - YouTube Do we know to what extent the scientific community has reached that they can make a decision as to the redefinition of the kilogram. Can it be possible to have two standards, such as the silicon ball and the watt balance? The silicon ball is actually still a physical artifact that can change with time just like the cylinder. The watt balance is more in line with a non-physical device, but with the watt-balance, the coulomb and the volt become basic natural constants and the kilogram is derived. From: mechtly, eugene a <mailto:mech...@illinois.edu> Sent: Friday, 2013-06-07 13:33 To: Kilopascal <mailto:kilopas...@cox.net> ; U.S. Metric Association <mailto:usma@colostate.edu> Cc: mechtly, eugene a <mailto:mech...@illinois.edu> Subject: RE: World's Roundest Object! - YouTube If you want to learn more about the silicon-28 sphere as a contendor for the redefinition of the kilogram search for CSIRO, the Australian Commonwealth Scientific and Industrial Research Organization. From: Kilopascal [kilopas...@cox.net] Sent: Thursday, June 06, 2013 10:06 PM To: U.S. Metric Association Subject: World's Roundest Object! - YouTube Very interesting video on the kilogram. http://www.youtube.com/watch?v=ZMByI4s-D-Y No virus found in this message. Checked by AVG - www.avg.com Version: 2013.0.3343 / Virus Database: 3199/6390 - Release Date: 06/06/13
