| ??? 03/23/07 21:11 Read: times |
#135708 - k-m-s Responding to: ???'s previous message |
Steve M. Taylor said:
The Metre is equally "arbitrary", being conveniently 10% bigger than a yard, like 1 kilo is 10% bigger than 2 lbs or 1 litre is 10% bigger than 2 English pints.
...and metre as one ten-millionth of the length of the Earth's meridian along a quadrant (the distance from the equator to the north pole) Now this is demagogy :-) Metre was established from something those people (closely related to Voltaire & co, alias the encyclopedists) believed to be firm and stable, so it can be remeasured later. They actually took the pain to measure half of the meridian which crosses Paris (this was somewhat easier than to go along the 0th meridian - and more politically correct for French who did the work that time) - but they did not go to North pole (which was "visited" some 100 years later for the first time); so they went quite down to Africa. When this work was finished, the etalon (with X-cross section) was prepared and stored in Sevres, and the definition of metre was equal to length of that rod (two marks on it, actually). Later they realized that it wears out very quickly and changes length due to temperature, that's why the definition was changed several times. Litre is one cubic decimetre. One kilogram is the weight of one litre of water, but actually they made an ethalon for that one, too. Makes quite a nice story. JW |
