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Shrinking kilogram bewilders physicists
Associated Press | Sep. 12, 2007 | JAMEY KEATEN

Posted on 09/12/2007 2:47:48 PM PDT by decimon

By JAMEY KEATEN, Associated Press Writer 6 minutes ago

PARIS - A kilogram just isn't what it used to be. The 118-year-old cylinder that is the international prototype for the metric mass, kept tightly under lock and key outside Paris, is mysteriously losing weight — if ever so slightly.

Physicist Richard Davis of the International Bureau of Weights and Measures in Sevres, southwest of Paris, says the reference kilo appears to have lost 50 micrograms compared with the average of dozens of copies.

"The mystery is that they were all made of the same material, and many were made at the same time and kept under the same conditions, and yet the masses among them are slowly drifting apart," he said. "We don't really have a good hypothesis for it."

The kilogram's uncertainty could affect even countries that don't use the metric system — it is the ultimate weight standard for the U.S. customary system, where it equals 2.2 pounds. For scientists, the inconstant metric constant is a nuisance, threatening calculation of things like electricity generation.

"They depend on a mass measurement and it's inconvenient for them to have a definition of the kilogram which is based on some artifact," said Davis, who is American.

But don't expect the slimmed-down kilo to have any effect, other than possibly envy, on wary waistline-watchers: 50 micrograms is roughly equivalent to the weight of a fingerprint.

"For the lay person, it won't mean anything," said Davis. "The kilogram will stay the kilogram, and the weights you have in a weight set will all still be correct."

Of all the world's kilograms, only the one in Sevres really counts. It is kept in a triple-locked safe at a chateau and rarely sees the light of day — mostly for comparison with other cylinders shipped in periodically from around the world.

"It's not clear whether the original has become lighter, or the national prototypes have become heavier," said Michael Borys, a senior researcher with Germany's national measures institute in Braunschweig. "But by definition, only the original represents exactly a kilogram."

The kilogram's fluctuation shows how technological progress is leaving science's most basic measurements in its dust. The cylinder was high-tech for its day in 1889 when cast from a platinum and iridium alloy, measuring 1.54 inches in diameter and height.

At a November meeting of scientists in Paris, an advisory panel on measurements will present possible steps toward basing the kilogram and other measures — like Kelvin for temperature, and the mole for amount — on more precise calculations. Ultimately, policy makers from around the world would have to agree to any change.

Many measurements have undergone makeovers over the years. The meter was once defined as roughly the distance between scratches on a bar, a far cry from today's high-tech standard involving the distance that light travels in a vacuum.

One of the leading alternatives for a 21st-century kilogram is a sphere made out of a Silicon-28 isotope crystal, which would involve a single type of atom and have a fixed mass.

"We could obviously use a better definition," Davis said.


TOPICS: Miscellaneous; News/Current Events; Technical
KEYWORDS: kilogram; stringtheory
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I was going to go for iridium siding but now I don't know.
1 posted on 09/12/2007 2:47:50 PM PDT by decimon
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To: decimon

It’s evolving.


2 posted on 09/12/2007 2:49:02 PM PDT by RightWhale (Stop Change while it is perfect.)
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To: decimon

Would it be too far fetched to say this demonstrates entropy?


3 posted on 09/12/2007 2:49:40 PM PDT by Recovering_Democrat ((I am SO glad to no longer be associated with the party of Dependence on Government!))
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To: decimon

The Guiness diet?


4 posted on 09/12/2007 2:49:50 PM PDT by mnehring (What does the Ron Paul Rorschach test say about you?)
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To: decimon

mice


5 posted on 09/12/2007 2:49:51 PM PDT by nuconvert ("Terrorism is not the enemy. It is a means to the ends of militant Islamism." MZJ)
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To: dighton; martin_fierro; jdm; cyborg; Tijeras_Slim

Doesn’t everybody’s Gram get smaller as she ages? It’s usually osteoporosis.


6 posted on 09/12/2007 2:50:16 PM PDT by Petronski (Cleveland Indians: Pennant -11)
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To: decimon
50 micrograms is roughly equivalent to the weight of a fingerprint.

You don't suppose that's the answer right there, do you?

7 posted on 09/12/2007 2:50:57 PM PDT by Oberon (What does it take to make government shrink?)
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To: decimon

Next time don’t allow trace amounts of tofu in your metal castings!


8 posted on 09/12/2007 2:51:09 PM PDT by ikka
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To: Recovering_Democrat
Would it be too far fetched to say this demonstrates entropy?

That was my first thought.
9 posted on 09/12/2007 2:51:26 PM PDT by JamesP81
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To: decimon

That’s 0.005%. Give me a break. Pierre miscalibrated the scale when he was measuring it.


10 posted on 09/12/2007 2:51:57 PM PDT by stm (Fred Thompson in 08!)
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To: decimon
Since global warming is doing a "Titanic", this would give the libs a whole new scare:

Global Shrinking.

Are you sure you're not getting small?


11 posted on 09/12/2007 2:53:23 PM PDT by capt. norm (Be thankful we're not getting all the government we're paying for.)
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To: decimon

I thought my last bottle for french wine looked a little short. This explains it.


12 posted on 09/12/2007 2:53:44 PM PDT by UglyinLA
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To: decimon

The last guy who used it dropped it and nicked off a corner?


13 posted on 09/12/2007 2:54:00 PM PDT by FatherofFive (Choose life!)
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To: decimon

The copies have probably oxidized a bit and gained weight—sort of like I have.


14 posted on 09/12/2007 2:54:06 PM PDT by Cruising Speed
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To: RightWhale

Like the definition of 6 inches?


15 posted on 09/12/2007 2:55:15 PM PDT by SmithL (I don't do Barf Alerts, you're old enough to read and decide for yourself)
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To: decimon

The NIST was working on a replacement for the Kilo-gram a few years back involving magnetic energy force. I guess they’re still working on it..........


16 posted on 09/12/2007 2:56:01 PM PDT by Red Badger (ALL that CARBON in ALL that oil & coal was once in the atmospere. We're just putting it back!)
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To: Logophile

“We could obviously use a better definition,” Davis said.

I thought you might appreciate this thread : )


17 posted on 09/12/2007 2:56:34 PM PDT by LeGrande (Muslims, Jews and Christians all believe in the same God of Abraham.)
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To: decimon

Sometimes there’s a silver lining to the cloud. A similar weight discrepancy led a researcher to hypothesize that carbon might have a different configuration in nature than Diamonds, C-6, C14, and others, so he generated C-60 and C-72 to account for the weight discrepancy and we now have buckyballs. There could be something here worth researching.


18 posted on 09/12/2007 2:56:39 PM PDT by Kevmo (We should withdraw from Iraq via Tehran. And Duncan Hunter is just the man to get that job done.)
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To: Recovering_Democrat

Local gravity may have changed slightly..............


19 posted on 09/12/2007 2:57:19 PM PDT by Red Badger (ALL that CARBON in ALL that oil & coal was once in the atmospere. We're just putting it back!)
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To: decimon

Global Shrinking! Bush’s fault!


20 posted on 09/12/2007 2:57:45 PM PDT by PhatHead
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