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kg definition calculated using constants not standard weight comparison.


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I used to think (because we were told this in school) that the standard definition of a kilogram was the mass of 1 litre of water at stp.  I guess this definition could be ambiguous anyway what with isotopes in the water and the accuracy of measuring the litre exactly.

They have apparently got a way to calculate 1 kilogram and to define it with that calculation from Plank's constant. I did not see the derivation in this New Scientist article. I'll try to look it up sometime unless anyone knows what the relationship is between Plank and the kilo and can post it?

Here is their headline anyway:




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18 minutes ago, Strange said:

We had a thread on this a while ago

yea - I thought there might have been...  I did a quick search to try to find it because I thought I'd read something... but couldn't find it.

Please feel free to delete this or merge with the other.  My question still stands though.  Does anyone know the mathematical relationship between the kilogram and plank's constant?  I might try to look for it later when not at work....


....aaaaand it's in your link already  -  thanks.

Edited by DrP
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