Re: Metric Time (was Re: Why not 13 months? (Was La Systeme Metrique))

Markus Kuhn (
17 Oct 1995 14:56:12 +0100 writes:

>In article <>, (Mike Fee) writes:
>>Consider also, Whayn; a "metre", and that is exactly how the French spell it
>>(they should know), is a thing about 1 650 763.73 times the wavelength (in
>>vacuum) of a particular electronic transition in the element Krypton. It is

>Once again, thats no longer the definition of a meter. It is
>defined in terms of the speed of light. Check your facts.

Here is the official specification from International Standard ISO
1000:1992(E), Annex B:

metre: The metre is the length of the path travelled by light in
vacuum during a time interval of 1/299 792 458 of a second.

kilogram: The kilogram is the unit of mass; it is equal to the mass of
the international prototype of the kilogram.

second: The second is the duration of 9 192 631 770 periods of the
radiation corresponding to the transition between the two hyperfine
levels of the ground state of the caesium-133 atom.

[and there are also such definitions for ampere, kelvin, mole and
candela ...]

Alle Angaben wie immer ohne Gew€hr. ;-)

BTW: There is some work going on on replacing the definition of the
kilogram by one which does not depend on a prototype. Does anyone know
the status of this? I have also heard that the second might some day
be defined using a oscillation of a mercury isotope, which can be
measured even more precisely.

If you are interested in having a copy of ISO 1000 (aka the metric
system), I highly recommend to get the book

Quantities and units,
ISO Standards Handbook,
International Organization for Standardization,
345 pages, 3rd edition, Geneva, 1993,
ISBN 92-67-10185-4.

For ordering information, check <> or mail to I guess, every good bookshop will also be able to
order it, as is your national standards body (ANSI, DIN, AFNOR, etc.).


Markus Kuhn, Computer Science student -- University of Erlangen,
Internet Mail: <> - Germany
WWW Home: <>