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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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To: spunkets

So it is global warming?


61 posted on 09/12/2007 3:32:35 PM PDT by decimon
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To: decimon

gravity was weak that day.


62 posted on 09/12/2007 3:32:46 PM PDT by jdub
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To: decimon

Quick! Someone get Algore!!!


63 posted on 09/12/2007 3:32:55 PM PDT by JRios1968 (Faith is not believing that God can. It is knowing that God will. - Ben Stein)
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To: JRios1968
Quick! Someone get Algore!!!

He could use the weight loss.

64 posted on 09/12/2007 3:34:24 PM PDT by decimon
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To: decimon
"So it is global warming?"

Nah. Processing...

65 posted on 09/12/2007 3:34:26 PM PDT by spunkets ("Freedom is about authority", Rudy Giuliani, gun grabber)
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To: spunkets
The Pt-Ir alloy has a stable crystal structure. 50 µg of mass is worth 4.5*109J of energy. An entropy change is a configurational energy change at some temp T. See the problem?

uh... no..? :-)

66 posted on 09/12/2007 3:35:49 PM PDT by Ramius (Personally, I give us... one chance in three. More tea?)
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To: capt. norm

Only if they can find a way to blame humanity, cripple capitalism while sucking up tons of money for a handfull of left-wingers.


67 posted on 09/12/2007 3:36:39 PM PDT by FreeAtlanta (Search for Folding Project - Join FR Team 36120)
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To: decimon
It must be due to 'shrinkage'...

 

Jerry and George talking in Jerry's room.

George: Did she do it on purpose?

Jerry: It was my fault, I told her the wrong door.

George: I was supposed to see her. She wasn't supposed to see me.

Jerry: So what?

George: Well ordinarily I wouldn't mind. But...

Jerry: But...

George: Well I just got back from swimming in the pool. And the water was cold...

Jerry: Oh... You mean... shrinkage.

George: Yes. Significant shrinkage!

Jerry: So you feel you were short changed.

George: Yes! I mean, if she thinks that's me she's under a complete misapprehension. That was not me, Jerry. That was not me.

Jerry: Well, so what's the difference?

George: What if she discusses it with Jane?

Jerry: Oh, she's not gonna tell Jane.

George: How do you know?

Jerry: Women aren't like us.

George: They're worse! They're much worse than us, they talk about everything! Couldn't you at least tell her about the shrinkage factor?

Jerry: No, I'm not gonna tell her about your shrinkage. Besides, I think women know about shrinkage.

George: How do women know about shrinkage? (They see Elaine walking down the hall) Elaine! Get! (She enters) Do women know about shrinkage?

Elaine: What do you mean, like laundry?

George: No.

Jerry: Like when a man goes swimming... afterwards...

Elaine: It shrinks?

Jerry: Like a frightened turtle!

Elaine: Why does it shrink?

George: It just does.

Elaine: I don't know how you guys walk around with those things.

68 posted on 09/12/2007 3:48:41 PM PDT by The Electrician ("Government is the only enterprise in the world which expands in size when its failures increase.")
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To: Red Badger
Local gravity may have changed slightly..............

Hmm. Interesting point. There's a standard kilogram locked away in a box, but how do you lock away a standard g?

69 posted on 09/12/2007 3:57:05 PM PDT by Vroomfondel
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To: Ramius
Entropy is defined as S = k*ln(Ω). Where k is Boltzman's constant and Ω is the number of ways the Pt and Ir atoms can be arranged in the crystal. The Pt-Ir alloy has a regular crystal structure where the atoms appear in the lattice in a fairly regular way. They can migrate and diffuse around somewhat, but you'll never get 4.5*109J out of that. That's the amount of energy that must be lost to account for the loss of 50 µg, from E=mc2. That's a huge amount of energy. That's the equivalent of the output of a 10kW generator for 5.2 days.

I suspect witches. ...or a magnetic effect from absorbed hydrogen. Don't know yet boss...

70 posted on 09/12/2007 4:05:35 PM PDT by spunkets ("Freedom is about authority", Rudy Giuliani, gun grabber)
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To: decimon; Millee; TrueKnightGalahad; blackie; null and void; Larry Lucido; Eric Blair 2084; ...
Yet down through all the ages... the foot has stayed the same!

Gadzooks! Now that... scares me

71 posted on 09/12/2007 4:11:19 PM PDT by Bender2 ("I've got a twisted sense of humor, and everything amuses me." RAH Beyond this Horizon)
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To: decimon
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


72 posted on 09/12/2007 4:27:51 PM PDT by mikrofon (Electrolux)
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To: Bender2

Arch, is that you?


73 posted on 09/12/2007 4:39:56 PM PDT by decimon
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To: mikrofon

Duh, lights are in refrigerators, not vacuums.


74 posted on 09/12/2007 4:41:33 PM PDT by decimon
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To: decimon
Re: Arch, is that you?

Is that you... Meathead?

75 posted on 09/12/2007 4:46:30 PM PDT by Bender2 ("I've got a twisted sense of humor, and everything amuses me." RAH Beyond this Horizon)
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To: Petronski
Doesn’t everybody’s Gram get smaller

Cold showers is one shrink factor.......

76 posted on 09/12/2007 5:02:13 PM PDT by Hot Tabasco (No tap dancing allowed in this restroom facility)
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To: decimon

Not even the Metric System wants to use itself.


77 posted on 09/12/2007 5:02:41 PM PDT by Duke Nukum (He burns at the center of time and he sees the turn of the Universe.)
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To: Recovering_Democrat
(Why did you ever choose THAT name?) :)

Well...my last boss before I retired from the Marine Corps was an aviator (attack pilot) and everyone who worked for him either already had a call sign (because they were aviators too) or was assigned one based on some "quaint" foible or telling incident. I'm a fairly big guy, broad shouldered, wear glasses, and I can occasionally be kind of stubborn and short-tempered when provoked, so "Rhino" was sort of a natural fit, you might say. (In good fun afterward, the colonel sometimes used to kid me by asking if I'd felt the urge to charge any jeeps lately...)

I was a Captain at the time, so later, when I needed a screen name...

I have since had conversations with retired aviators about how these call signs get assigned (usually toward the end of flight school or at your first squadron). You don't ever get to pick your own. And if you try to change it, brother, standby!

Anyway, all I can say is that the gods of call signs were smiling down on me that day because it could have been far, far worse.

78 posted on 09/12/2007 5:07:23 PM PDT by Captain Rhino ( Peace based on respected strength is truly peace; peace based on weakness is ignoble slavery)
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To: Oberon
Did they let a Frenchman touch it? They can be very acidic.
79 posted on 09/12/2007 5:11:27 PM PDT by mad_as_he$$ (Remember Mustang 22 and her heroes.)
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To: lesser_satan

They should check for some escaping neutrons!


80 posted on 09/12/2007 5:48:02 PM PDT by GregoryFul (how'd that get there?)
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