I have heard that the meter was once defined as a certain percentage of the distance from the pole to the equator. There was a rod that was used to be a meter and all other meters are based off the rod locked in the vault. Then it was decided that the rod might be changing and a set definition of the distance traveled during a certain time at the speed of light was used…Ok fair enough but then why cant we do a similar thing for the kilogram? I understand that a weight is still used and locked in a vault. Wouldnt a set definition be better then a tangible object?
Just to be annoying, let me be the first to point out that the kilogram is a unit of mass, not weight.
The move to such a standard is already underway - see the section titled “The Avogadro Project”
Particularly interesting from beowulff’s link is the section Stability of the International Prototype Kilogram, which talks about variation in mass of the Prototype Kilograms. The International Prototype Kilogram is just one of 40 replicas, that was selected (arbitrarily?) as The International Prototype Kilogram.
I believe NIST is working on an electronic kilogram. I suspect other national labs are probably working on something similar.
1/10,000th.
Thre was a fascinating article, I think in the summer of 07, about polishing silicon spheres for the Avogadro project. It appeared in Scientific American.
No, it was 1/10,000,000th. If it were 1/10,000th, then it would be 10,000 metres, or about 6 miles, from the Equator to one of the poles.
10,000 km rather, I’d say.
Which was Giles’ point, right?