Aside from its usefulness, it's a beautiful object.
Posted on 06/14/2007 10:36:36 PM PDT by anymouse
They will be the earth's roundest spheres, crafted by Australian scientists as part of an international hunt to find a new global standard kilogram.
Ever since scientists discovered that the current standard -- a bar of platinum and iridium held in a French vault since 1889 -- was slowly deteriorating, the search has been on for a replacement.
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.
"We are doing everything to really create a perfect object. It's not only near-perfect in roundness, but also the crystal purity, the atomic species and so on," project leader Walter Giardini told Reuters on Friday.
"Silicon is a very nice material to use that we understand well, makes good crystals and can be worked," said Giardini, from Australia's National Measurement Institute.
The two balls will take 12 weeks to create and, because they are made from a stable element, they will not fall victim to moisture, corrosion and contamination like the current kilogram standard, known as the International Prototype.
The spheres will be a step along the perfect kilogram road, with the project's ultimate aim to re-define the kilogram in terms of numbers of atoms, rather than an object open to damage from earthquake or environmental changes.
"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."
The project is a collaboration involving scientists from Russia, Germany, Italy, Belgium, Japan, the United States and Australia, in cooperation with the International Bureau of Weights and Measures.
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.
Australian scientists have the most expertise in grinding near-perfect spheres, having been turning them out for clients including NASA since the early 1990s.
"We have developed technology so that we can see what we are getting, whether they are slightly oval or flat. We are trying for an accuracy of two parts in 100 million," Giardini said.
Cubes are not optimal for this. First off, the edges of the cube would be ragged. You'd get great deal of uncertainty.
Second, physical, solid cubes are not really cubes -- they deform under stress. (I had a professor derive this mathematically back in college -- I cannot recall the details.) So the volume computation would be a lot more complicated than you've laid out.
Aside from its usefulness, it's a beautiful object.
Grow a pair
When they're perfected, they ought to mass produce them and hand them out in pairs to just about all the Republican Senators and Congressmen down in D.C.! - John
Indeed, (the ones that are held for pleasure are the ones that I like best......)
8^)
My first though as well.
BUT corners and edges chip. A sphere is far more mechanically robust.
Do you have her number???
Clackers
“A “perfect” sphere has only one factor, its radius.”
Actually, a sphere has not one, but rather it has innumerable sides, the exact number of which depends on the resolution of your measurement system. It is far more difficult to make a perfect sphere than it is to make a perfect cube or bar because of the difficulty in measuring and referencing the location of all points on a sphere. One can measure a flat-sided surface fairly easily because it is far easier to reference a flat surface than to reference a sphere. It is also easier to shape and polish a flat surface than to shape and polish a sphere.
If they are forged, will they be fake but accurate?
I know, I know. I should have asked before I posed as the model for them.
Yes, but:
"...with imperfections of less than 35 millionths of a millimeter."...it is NOT perfect. Close to perfect, but not exactly.
(God must be getting a good chuckle out of this endeavor!)
Why didn’t they just call me?
Never mind.
Thank you.
And on a related note, I really wish the US would have adopted the metric system. Seriously! It just makes sense.
Can we use those as a Standard of Measurement for GOP candidates in 08? “Here are two perfect balls, of silicon, how do YOUR balls measure up?”
Can we?? Hua? Please?
YES!
Silicon is stable, unlike Noble Metals, and doesn't oxidize---that is why I always have to dump a truck load of SiO^2 outta my shorts & shoes whenever I go to the beach.
Silicon is stable, unlike Noble Metals, and doesn't oxidize--that is why I have a collection of agates, agatized fossil shells, & petrified wood, formed when SOLUTIONS of SiO^2 invaded....
Won't mention all the other various classes of silicates, except to say we would be missing an enormous amount of our rocks & soils without them.
I blame the reporter/editor, not the scientists; and I expect these to be kept in controlled conditions i.e. relatively normal temperatures, humidities, pressures, & atmosphere, that precludes reaction.
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