Hi all, I just realized that a meter is defined by the speed of light., see http://physics.nist.gov/cuu/Units/meter.html It is only to 9 significant digits, so if the speed of light (in some controlled environment) is measured more precisely than this, the meter and all other derived length units will change?
(I was taught that 1 meter was 39.37 inches, to define the inch , but now I see more of 1 inch = 2.54 cm, as someone just referred to.) I find the standard for the Ampere, mentioned in the nist pages above more difficult, as 2 infinite wires to measure the force between cannot be found! Was the coulomb the standard before? Does anyone have other web pages to recommend? (Am still learning about the 1948 changes to electrical units, international and absolute volts, etc. Before finding this list, did not think much about the differences, about 500 ppm., with a 3 1/2 digit dvm.) David D. >Oh, is that SI Inch or US Metric act Inch? There is about 2 ppm of difference >you know (we are time-nuts after all, right?). It was actually C E Johansson >that tricked the world into beleiving the Inch was 25.4 mm and when they found >out the US motor industry was running of Johanssons version of the Inch and >refused to change. _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
