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.
Where’s Bon Scott when we need him?
But we do have Laura Ingraham.
Hey, if Hillary buys these, she can give Bill’s back to him.
“For the first time in over a century, europe will be in possession of a pair of balls.”
LOL! Did you write that?!
I can understand the spherical part giving it the ability to weigh consistently in any position.
I can understand the need for a physical safeguarded reference of measure for political reasons.
What I can’t understand is the reference that a physical object is needed to count the atoms. Weights and measures are already determined and digitized and equally in referenced and scaled measure atoms have specific weight which has also been determined and digitized.
So I see a mathamatical equation complicated by substance, shape, temperature and location. But it’s still just a math problem.
But I guess a pair of perfect balls is nothing to laugh at.
I was having the same thought - pi is irrational and goes on forever. Why not make the object a cube?
The answer may be the delicacy of the shape. They're looking for something that doesn't erode or deteriorate and that will maintain its mass to an exquisitly precise standard, so durability is a requirement, and the sphere is smooth and resistant to accidental damage. The cube or other block shape would have extremely sharp and delicate edges. I'm thinking of knocking the corner off a concrete block vs chipping a piece from a cannonball.
And the sphere is defined by ONE dimension.... radius.
So instead of screaming about his strawberries, he’ll be screaming about his balls?
I don’t think that’s an improvement.
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Perfect silicon sphere to redefine the kilogram The Age, Australia - A CSIRO scientist examines a silicon sphere, similar to one that will be used to determine the exact atomic weight of a kilogram. ... |
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Perfect spheres to redefine the kilogram ABC Science Online, Australia - Scientists are hoping to redefine the kilogram by counting the number of atoms in the roundest objects ever made. So for the first time, a kilogram would ... |
"In the Garden of Eden lay Adam,
Complacently stroking his madam,
And loud was his mirth,
For on all of the Earth,
There were only two balls,
And he had 'em."
Possibly because a bar has many factors that influence its volume: flatness of each side, parallelism of edges and sides, sharpness of each edge and corner, length of each side, etc. A "perfect" sphere has only one factor, its radius.
Too easy.
Sure we do. It's just that very few politicians have anything that even comes close.
Ahh, but the strawberries!
Then what are they grinding? A figment of their imagination? Hallucinations?
Serious science? When scientists start making more intelligent sounding statements, then it will be easier to take science seriesly.
OK, for the confused:
They are making reference objects that can be put on precise scales to calibrate the scales.
You can’t do that by making something, and rubbing off bits until it weighs the right amount, because you need a scale to weigh it, and that scale needs to be calibrated.
So you make something of a material that of a known density, and make it to a known volume. You choose a sphere because its volume can be measured by only one measurement (diameter).
Of course, you need to calibrate the “”calipers” you measure it with, but that kind of calibration is absolute, with devices that use known wavelengths of certain atomic vibrations. They count the number of wavelengths across the diameter.
Then, you put the ball on the “mother” scale, and cabibrate the scale. That can be used to weigh test items that are sent in from other precision scale owners, so they can be told how much their sample weighed. Or, the balls may be taken on tour, rented out. (Precision instrument calibration is a big business.)
You see, brilliant scientists and engineers rarely do things that are dumb. It’s just that news reporters can make smart stuff sound dumb with inadequate reporting. Like here, when they take down other people’s quotes and explanations, instead of actually explaining the concept.
And when they say that the standard won’t depend on a physical object, they mean that they will no longer have an uncertain lump in a glass case that is arbitrarily defined as a “kilogram.”
They have an object that is known to have a kilograms’s worth of Silicon atoms And atoms are of known mass by definition, with a known number of subatomic particles in each.
Essentially, “mass” is just a way of saying how many atoms are in a thing.
Not quite. They're also ensuring that the mass of the sphere is exactly 1 kg.
As the article said, the idea is to be able to define the kilogram in terms of atoms. Since they know the volume and the mass, they would know the density. And because they're using a near-perfect crystal, they can translate the density to the number of atoms in the sphere.
At that point, the definition of "kilogram" becomes "the mass of N atoms of silicon-28."
I’m not confused, just sarcastic.
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