Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   According to wikipedia, one liter of pure water at 4 degrees celsius (the
> > standard temperature for measuring SI units) is 0.9999720 kilograms.

> It may be that it's too difficult to measure "pure water" at "exactly 4 
> degrees celsius" for modern measurement precision.

  Not more difficult than measuring the exact speed of light (which is needed
to define the unit of length) or an exact magnetic force (which is needed to
define the unit of electric current).

> Plus, of course, if you make *everything* circular, then you have nothing. 
> If a kilogram is the weight (well, mass) of a liter of water, and a liter is 
> 1000 cubic centimeters, and a centimeter is the length of one gram of carbon 
> atoms lined up (or some such) then the whole thing falls down.

  But a centimeter is not defined like that. It's defined from the speed of
light in vacuum. There's no circle.

> Given that a cm is defined in terms of the speed of light, and time is 
> defined in terms of a cesium atom at rest at 0K, I guess we already have 
> unusable base metrics, tho.

  Unusable base metrics?

> >   If they changed the definition of kilogram back to its original form, the
> > change would be less than 0.003% from the currently accepted value. Would
> > that be a huge catastrophe?

> Only for scientists working on 15 digits of precision in their scientific 
> experiments. Kind of like "would it really make a difference if we skipped a 
> leap-second every 3 to 5 years?"

  Given that the object which is currently the measurement of 1 kg changes
weight every time it's measured, does it really matter? It would simply be
one more change, but then it would be fixed, and that's it.

-- 
                                                          - Warp

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