The scientific community is working on the replacement:
Known as the Avogadro Project, the plan is to bring together enough atoms of one substance – silicon – to make a kilo.
Attention has focused on silicon because:
- its characteristics are very well understood
- a single crystal of the right size can be grown
- its atomic structure is extremely uniform
- its widespread use in the computer industry means it can be obtained with relative ease at high purity and resonable cost.
A spherical shape was chosen because a sphere has no edges that might get damaged and only one dimension has to be measured in order to calculate its volume.
> A spherical shape was chosen because a sphere has no edges that might get damaged and only one dimension has to be measured in order to calculate its volume.
Surely every dimension needs to be checked, to ensure that it's a perfect sphere? (Which I assume is harder than checking a cuboid has six flat sides joined at right angles)
If you build an apparatus for measuring a sphere's diameter, it's possible to measure it in any orientation. If their test mass were cylindrical, they'd need the ability to measure both the diameter and the length to the requisite precision. I believe it is in this sense that 'dimension' was used.
The Avogadro project isn't the only horse in this race. The electromechanical approach, known as a Watt balance, is underway in several national standards labs around the world.
Known as the Avogadro Project, the plan is to bring together enough atoms of one substance – silicon – to make a kilo.
Attention has focused on silicon because:
- its characteristics are very well understood
- a single crystal of the right size can be grown
- its atomic structure is extremely uniform
- its widespread use in the computer industry means it can be obtained with relative ease at high purity and resonable cost.
A spherical shape was chosen because a sphere has no edges that might get damaged and only one dimension has to be measured in order to calculate its volume.
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http://www.csiro.au/content/ps35k
http://www.youtube.com/watch?v=ZMByI4s-D-Y