From the Wall Street Journal – By JEANNE WHALEN
In a vault beneath a 17th-century pavilion on the outskirts of Paris sits a platinum cylinder known as Le Grand K. Since 1889 it has been the international prototype for the kilogram, the standard against which all other kilos are measured.
But over the years, scientists have noticed a problem: Le Grand K has been losing weight. Weigh-ins at the International Bureau of Weights and Measures show that the bar has shed approximately 50 micrograms—roughly equal to a grain of sand.
The problem has vexed scientists who monitor the kilo the way tabloids track the waistlines of Valerie Bertinelli and Kirstie Alley. The stakes, however, are weightier.
“It’s a scandal that we’ve got this kilogram hanging around changing its mass and therefore changing the mass of everything else in the universe!” Bill Phillips, a Nobel Prize winning physicist, exclaimed at a scientific summit in London this week. No one knows for sure what went wrong with Le Grand K, but some theorize it lost weight from being cleaned.
Dr. Phillips and other mandarins of metrology were gathered at Britain’s Royal Society to debate an urgent question in the science of measurement—how to re-define the basic unit of mass, as well as other measurements such as the second, ampere, kelvin and mole.
The aim is to tie each to a widely accepted property of nature, rather than to a lump of metal or some other imprecise benchmark. The meter, for instance, was once measured as the distance between two notches on a metal bar. It is now defined as the distance light travels in a vacuum in 1/299,792,458 of a second.
The new definitions are “as big a change as the introduction of the metric system during the French Revolution,” says Terry Quinn, a dapper Briton who organized the seminar and once served as director of the International Bureau of Weights and Measures, which ensures world-wide uniformity of measurements. Frequent clashes about the best approach mean the temperature of debate has at times “risen quite high,” he added, without specifying by how much.
Full story at the Wall Street Journal
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From the image:
Let me be the first to say … Watt?
.
Terry Quinn may be dapper but he’s hyperbolic. The French Revolution standardized and rationalized a lot of measures. These changes are incremental, and a very tiny one at that. Nice, though; I’ll give ’em that.
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Phil’s Dad says:
January 28, 2011 at 5:55 pm
Not to be pedantic but if this is “the standard against which all other kilos are measured” how do they know it is losing mass?
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Or (gasp) maybe it’s gaining mass.
It’s time to take a vote.
We need a consensus!!!
I`ve never been a fan of `napoleon` measurements anyway….he lost didn`t he?
I`ll put my faith in the iron ulna
If it aint broke….
http://www.megalithicsites.co.uk/Mensuration1.html
But in 16th century Scotland the people had to do with James V’s pronouncement;
“Tak’ the meesure of a sma’ maun’s nose to his finger-tip. Tak’ the same from a reeg’lar maun, and a meikle maun. Combine all and divide by three. Yon is yi’r Yaird.”
Simples!
Is the premise that the fundamental behavior of nature/reality does not vary over time and space just a convenient assumption? Is it the ultimate null hypothesis?
John
Here is something for some poor slob of a PhD student to waste their life on: Assume neither energy or matter is created. Assume that the universe is expanding. The vacuum energy is known to exist and has mass equal to E=Mc^2. Since the total percentage of the volume of the universe occupied by the masic kilo is decreasing the amount of vacuum energy it contains is decreasing,. This is equalvalent to a decrease in its mass. You may now work on this for the next 10,000 years and still not come up with a good thesis to publish. But don’t say I didn’t warn you.
I thought a kilogram was defined as the mass of a litre of water. A litre is 1/1,000 cubic metre and we know how to define a metre now (i.e. light travelling in 1/299,792,458 of a second), so what’s the problem?
There is a radioactive isotope of Pt which is 0.014% abundant and is an alpha emitter. The half life is absurd… 6.5 x 10^11 years, but after nearly 200 years and with 1 kg of material, it is reasonable that 50 micrograms of helium would be lost from the sample from alpha emission. (The exponent value in the half-life equation is 0.999999999.)
Alternatively, this sample of platinum could already have helium inside of it and it could be lost over 200 years through slow diffusion.
Serves them right for picking something with a radioactive isotope.
French also tried to make metric time and metric calendar… Fortunately it was so inconvenient that it did not last long.
Steve in SC says:
January 28, 2011 at 4:53 pm
The big reason the US never went on the metric system is that Jefferson found out everything would be administered by the French and he said NO WAY JOSE!
At least 80% of their electrical generation is nukes. Not to shabby.
Chris Reeve says:
January 28, 2011 at 6:35 pm
There exists no enigma within the Electric Universe paradigm…
It testifies to the growing scientific illiteracy that such nonsense can be uttered.
REPLY: I agree, and I have removed that very long and nonsensical comment as it has no place here whatsoever. Mods, please tighten up to prevent such off-topic ridiculae. – Anthony
I’m amazed what I learn from WUWT. Until a few days ago I did not know that metrology was the science of measurements, but I learned that from your post on the metrology of thermometers. That’s a lot to learn for a know it all.
Maybe the missing mass turned into dark matter…
Smokey says: “In space, an object still has mass, but its weight is zero.”
I like everything else you said, but I must quibble with this. Gravity doesn’t stop just because you are in space. In orbit the object would be “weightless” but that is because it is in freefall, not because gravity has stopped pulling on it. It would be just as “weightless” in an elevator that is in freefall.
Michael says: “I thought a kilogram was defined as the mass of a litre of water. ”
That was the original definition, but that has not been the official definition of a kilogram for a looooong time.
DocattheAutopsy says: “There is a radioactive isotope of Pt …it is reasonable that 50 micrograms of helium would be lost”
From your own numbers, we can look at the orders of magnitude: about 1 out of 10,000 atoms are radioactive, about 1 out of a billion radioactive atoms would have decayed, which would be on the order of 0.0001 micrograms of radioactive Pt have decayed. No way that would be a 50 microgram loss. .
“Jimash says:
January 28, 2011 at 5:23 pm”
Is 0.3mm resolution good enough for your shed building?
http://www-3.unipv.it/donati/papers/75d.pdf
The big reason the US never went on the metric system.
The US is tied firmly to the metric system. You guys have several verified kilograms and your weights are defined in terms of them. All your physicists, chemists etc use metric, because to do otherwise would be daft.
The resistance of the US to a convenient and international system is nothing to be proud of. It’s like those people proud of being illiterate – because they’d never seed the point of book lernin.
I thought a kilogram was defined as the mass of a litre of water.
Both hydrogen and oxygen have commonly occurring isotopes. That means a litre of water in one place has a different mass from a litre of water in another. You could define is at water of 1-H and 16-O, but it is hard to make that with any degree of purity.
Reply to Phil’s Dad (@5:55pm)
From the second-last para of the WSJ article:
“Several dozen copies of the original are stored at national laboratories around the globe. Once every 50 years or so, scientists carry the copies by hand to Sèvres, just outside Paris, in little boxes, to compare them to the original. At the most recent summit in 1989, they noticed that the kilos differed by an average of about 50 micrograms. This is often described as Le Grand K losing mass, though to be precise, it’s possible that the copies had gained mass.”
Up to now, that is all you can do … compare a whole bunch of ‘copies’. (Some say there are 80 copies.)
But Australia’s CSIRO has been co-operating in a long term international venture, the Avogadro Project, to redfine the standard of mass in terms of Avogadro’s number, using a series of precisely manufactured spheres of Silicon.
The basic idea is to control the isotopic form of the Si during the crystal growing process (thanks to semi-conductor technology), then create a series of ‘near-perfect’ Si spheres of a precise diameter (93.6 mm) and shape (diameter controlled to “35 nanometres”). See one of several relevant CSIRO articles.
Of the 14 spheres manufactured by CSIRO’s Australian Centre for Precision Optics (as at April 2008), 12 have ‘out-of-roundness’ varying from about 63 – 70 nanometres; the best two have no more than 35 nanometres ‘out-of-roundness’.
Just think about that; that is equivalent to less than 5 mm ‘out-of-roundness’ on a sphere the size of the earth! (If only somebody would pay so much attention to averaging its temperature!)
Correction to my previous post: “5 mm” should be “500 mm” (unless I’ve made another mistake!).
Can the rules on discussing gravity and mass be clarified?
Am I being prevented from discussing how another framework would explain the same observation? What is the problem? Do you want me to explain it in my own words?
In the prior thread I participated in, I did not see a single complaint. Everybody seemed content to hear about it.
I’m surprised those sneaky conniving metrologists didn’t just get together and figure out a way to hide the decline….
We now know the speed of light in a vacuum exactly.
Incidentally, we ARE indirectly on the metric system now.
http://en.wikipedia.org/wiki/Inch
“Effective July 1, 1959, the United States and countries of the British Commonwealth defined the length of the international yard to be exactly 0.9144 meters.[1] Consequently, the international inch is defined to be equal to exactly 25.4 millimeters. “
Hmm, about 50 ppb over a long period. I would agree a cleaning operation sounds likely as the source of removal. Could there be a small evaporation rate, Pt sublimation or diffusion into the supporting material?
So the tension between deposition and evaporation goes on. I presume they have to clean it, or it “gains” weight as surface layers accrete from the air, as tightly controlled as it may be. But if they clean it it loses material… sounds like a tough job.
John Brookes says:
January 28, 2011 at 8:11 pm
You’re confusing metrologists with climatologists John
The English foot qualifies then:
http://chiefio.wordpress.com/2009/06/13/making-an-english-foot/