clipka <ano### [at] anonymousorg> wrote:
> With a liter of pure water at exactly 4 degrees celsius, one problem 
> you'll have is to exactly hit the 4 degrees celsius. Another problem is 
> to /get/ really pure water, and /keep/ it pure. Yet another problem is 
> that you'll have to define the exact isotopic composition of the water.

  I don't see how that is different from the current method, ie. measuring
the weight of that one object at 4 degrees celsius.

  Except that with water you don't have to rely on one specific object which
is unique and there exists only one in the world.

> Then there's the shape of the container. You need to make sure that it 
> /precisely/ holds 1 litre when it is at 4 degrees celsius /and/ filled. 

  Not much different from defining length in relation to the speed of
light. If you want to measure it, you need precise timing and precise
length measurements.

> >   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.

> Nobody /knows/ whether if it actually changes weight. All they know is 
> that the "primary copies" do change weight with respect to one another 
> and the Prototype.

  At least with the water the definition would be fixed to one single
weight. Then it's only a question of how accurately it can me measured,
which is no different from all the other units.

-- 
                                                          - Warp

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