On Monday 18 October 2010 15:16:24 Pat Naughtin wrote: > Dear All, > > From time to time I read the line (in various sources) that goes > something like: > > The metre has never changed in length, only the definition has been > rewritten to provide better accuracy and precision. > > This poses the question, "Which is the metre we use?" > > A brief chronology goes like this: > 1790 May 8 The French National Assembly decides that the > length of the metre will be equal to the length of a pendulum with a > half-period of one second.
The length of the pendulum in standard gravity is 993.621 mm. The difference between that and the meter bar would be immediately obvious to the metrologists of the time, whereas the difference between the fraction of the meridian and the meter bar is less than a millimeter. (a(1) means arctangent of 1.) 9.80665/(a(1)*4)^2 .99362138556613170634 Dunkirk to Barcelona is about 1/40, not 1/10, of the earth's circumference. Btw, my father said Calais to Perpignan; any idea where that rumor started? Pierre -- The Black Garden on the Mountain is not on the Black Mountain.
