David Dameron wrote: > 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. >
David You may find this link somewhat amusing http://www.sizes.com/units/miners_inch.htm If one moved around the various mining fields one could become somewhat confused by this unit of measurement. Bruce _______________________________________________ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
