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About the naturalness of a system of units

The main reason to reject the seconds pendulum was ``to have a unit of length that does not depend on any other quantity''[2]. Now we think exactly the other way around, and prefer a system with a minimal number of units connected by physical laws, as it was suggested first by Burattini in 1675 (see Appendix B). Besides cultural aspects, that make change `what is perceived as natural' with time,40 we find a certain contradiction in the use of the naturalness concept expressed in the Rapport[2]. Why not to extend it also to the weight unit, instead of binding, as it is known, this unit to the unit of length and to the density of water?

A similar comment applies to the right angle as the ``natural angle'' to justify the quarter of meridian (see Guedj's quote in subsection 7.2): the right angle is certainly the natural one for a square or a rectangle, but why should it be natural for a circle, where there are no angles? (At most, if there were an angle to be considered natural, that would be the radiant, as all those who use trigonometric functions of computer scientific libraries know).


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Giulio D'Agostini 2005-01-25