Warp schrieb:

>> That's because the /initial/ definition of the kilogram was one liter of 
>> pure water at /zero/ degrees celsius.
> 
>   At zero? I don't think so. At zero celsius water freezes, after which one
> litre of it weights a whole lot less than one kilogram.

I was indeed slightly mistaken: The original definition was for water at 
the /melting point/, which is a bit above 0 degrees C (something like 
0.01 degrees C, IIRC).


>> And yes, a /change/ of 0.003% would be a /tremendous/ catastrophe.
> 
>   To what?

To everyone requiring such a precision in /any/ physical unit derived 
from the kg.

I already mentioned how small the "drift" of the Prototype is - and yet 
scientists are worried about this, so /someone/ seems to be relying on a 
precision in that order of magnitude.

And after all, there is no reason whatsoever to redefine the kg in a way 
that "breaks backward compatibility": Whatever phyiscal properties you 
base it upon, you can always add some factor to the new definition to 
make it match the previous definition.

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