>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Jinx
>Sent: 15 June 2007 14:06
>To: pic microcontroller discussion list
>Subject: [EE] The grind's almost over to forge two perfect spheres
>
>
>http://www.nzherald.co.nz/section/story.cfm?c_id=82&objectid=10445968
>
>"Using a single crystal of silicon-28 grown by Russian and 
>German scientists over three years, a team of Sydney 
>scientists and engineers will grind and polish two silvery 
>balls, each weighing precisely one kilogram, with 
>imperfections of less than 35 millionths of a millimeter"
>
>All very clever and nice but I don't understand why if -
>
>"The aim is not to change the value of the kilogram, but to 
>ensure its stability for all future times," Giardini said. "It 
>will no longer depend on an actual physical object and this is 
>going to allow us to relate the mass to the individual atoms."
>
>and
>
>"On completion, the spheres will be measured for volume in 
>Australia, Germany and Japan, then measured for mass. Belgian 
>scientists will look at the molar mass of the crystal used to 
>calculate the number of molecules in each sphere."
>
>they can't work out how many molecules without building them. 
>And how are they weighing them ? Why isn't *that* the standard ?

What a load of old balls.

It does say the current 118 year old standard held ina French valut is degrading.  Garlic errosion perhaps?

Now I can understand wanting to make a nice standard that is impervious to oxidisation etc. but why does it need to be a sphere?  Surely that is just making things difficult for themselves.  Not only would it be easier to make something with flat sides, you could put it on a table without it rolling off and smashing itself it bits.

Mike

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