Re:Why scientists are redefining the kilogram
by kazinator on Thursday October 26, 2017 @03:17PM
(#15562106)
I guess that the problem with Avogadro's number (and others such, like the Coulomb) is that they are approximations and not specific counts.
The difference between the Avogadro Number and the new Avogadro Constant is that they will define it as a concrete integer value: 6.02NNNN... x 10^23. When the digits are agreed upon, I think the idea is that all subsequent digits are going to be defined as zero, making it a precise integer.
So then if it is a precise integer, we can then try construct objects with exactly that many particles (silicon atoms) and then weigh them, and so forth: masses can be tied to precise counts.
It's kind of analogous to declaring that an inch is exactly 2.54 mm: 2.54000000... not 2.5400XXX for some unknown X that is somehow empirically measured.
The difference between the Avogadro Number and the new Avogadro Constant is that they will define it as a concrete integer value: 6.02NNNN... x 10^23. When the digits are agreed upon, I think the idea is that all subsequent digits are going to be defined as zero, making it a precise integer.
So then if it is a precise integer, we can then try construct objects with exactly that many particles (silicon atoms) and then weigh them, and so forth: masses can be tied to precise counts.
It's kind of analogous to declaring that an inch is exactly 2.54 mm: 2.54000000... not 2.5400XXX for some unknown X that is somehow empirically measured.