On Wed, 1 May 2002, Marcus Berger asked for: > ... *official* references for...(especially the inch); when and > why the decision was made by English speaking countries to "standardize" > ... 25.4 mm value for the inch?
See NBS Miscellaneous Publication 247 issued 1963 October, page 20: "As a result of many years of preliminary discussion, the directors of the national standards laboratories of Australia, Canada, New Zealand, South Africa, the United Kingdom, and the United States entered into agreement, effective July 1, 1959, whereby uniformity was established for use in the scientific and technical fields. The equivalents 1 yard = 0.9144 meter (whence 1 inch = 25.4 millimeters) ..." > And finally why prefixes cannot be considered conversion factors?... Each prefix is an exact alpha-beta *substitute* for a power of ten numerical multiplier. That is, a setter (placer) of the decimal marker. Simply setting the location of the decimal marker without changing any numerical digits is rarely thought of as applying a conversion factor. One could avoid prefixes entirely by using the "E notation" of pocket calculators. e.g. A 10 km race is a 10 E3 m race is a 1.0 E4 m race, etc. and use *only* purely coherent SI units, a good practice when working on complicated numerical problems. Gene.
