On Sat, 13 Jul 2002, Joseph B. Reid wrote: > ... > The resolution that Gene refers to goes on to say > "*Watt* (unit of power) -- The watt is the power which in one second gives > rise to energy of one joule." > > >From that statement I deduce that the joule is a watt.second, which is > equivalent to a newton.metre = m2.kg.s-2
Joe, The distinction I am trying to make is that "realization" of SI units from their *definitions* requires an ordered progression of operations. Otherwise, circularity results (dog chasing its own tail). e.g. If a new laboratory had only a 1 kg mass standard and an accurate atomic clock, and tried to construct and calibrate other SI unit standards from scratch, but failed to reconstruct the meter correctly, the newton meter (joule) would be in error, and the joule/second (watt) would also be in error. The watt second could not generate a better value for the joule because the watt itself was not accurately calibrated. In other words, the newton meter must be considered a more "fundamental" definition of the joule (flowing directly from the SI base units) than the expression of the joule as a watt second, which is merely the identity: joule = watt second = (joule/second) second = joule; in an endless circle. Gene.
