Roundest Object In the World Created

holy_calamity writes "An international research group has created the most perfect spheres ever made, in a bid to pin down a definition of the kilogram. It should be possible to count exactly the number of atoms in one of the roughly 9cm silicon spheres to define the unit. Currently the kilogram is defined only by a 120-year-old lump of platinum in Paris, but its mass is changing relative to copies held elsewhere. Other SI units have more systematic definitions."

Comments

Re:What's the problem?

[multi io]

That is what they are doing. They are defining the kilogram as X silocon atoms.

And why do they have to actually create a silicon sphere for that? Couldn't they just define some reasonable X and then derive the actual weight of the kilogram from theoretical models?