Kilo prototype mysteriously loses weight

[ZapperZ]

The http://news.yahoo.com/s/ap/20070912/ap_on_re_eu/shrinking_kilogram, but about 50 micrograms!

Look out everyone. We are all heavier! So much for me trying to lose weight!

Zz.

 

[Ivan Seeking]

The http://news.yahoo.com/s/ap/20070912/ap_on_re_eu/shrinking_kilogram, but about 50 micrograms!

Look out everyone. We are all heavier! So much for me trying to lose weight!

Zz.

..."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."

Wow! That is odd. Very slow radioactive decay?

 

[ZapperZ]

Wow! That is odd. Very slow radioactive decay?

I would vote on vacuum fluctuation!

:)

Zz.

 

[Jimmy Snyder]

Local effects of Hubble flow.

 

[turbo]

Iridium has two stable (?) isotopes ¹⁹¹Ir and ¹⁹³Ir. Suppose that there was a small admixture of unstable isotopes in the kilo prototype?

 

[NeoDevin]

How about innacurate measurements 118 years ago?

 

[Math Jeans]

Thats really cool. Although I don't understand half of the theories you guys put up, its still cool.

 

[turbo]

The prototype is losing mass with respect to later copies (and they are compared periodically), so perhaps ¹⁹³Ir can very slowly decay to ¹⁹¹Ir at a rate that must be measured in decades or centuries.

 

[tacosareveryyum]

I would vote on vacuum fluctuation!

I second this!

 

[Moonbear]

50 micrograms is roughly equivalent to the weight of a fingerprint.

So, out of curiousity, how do they know the standard is the one losing weight, and that the problem isn't that the ones kept under less stringent conditions aren't gaining weight from things like fingerprints and dust?

 

[dtl42]

I agree with Moonbear, but kind of find it hard to believe that carelessness like that would be overlooked. I think it could be some sort of extremely slow radioactive decay.

 

[turbo]

I agree with Moonbear, but kind of find it hard to believe that carelessness like that would be overlooked. I think it could be some sort of extremely slow radioactive decay.

Maybe not a radioactive decay, but a spallation process in which the heavier isotope is hit by high-energy particles, and goes to ¹⁹²Ir, which IS radioactively unstable and decays to ¹⁹¹Ir.

 

[moe darklight]

So, out of curiousity, how do they know the standard is the one losing weight, and that the problem isn't that the ones kept under less stringent conditions aren't gaining weight from things like fingerprints and dust?

I say a prankster went around touching all the replicas. This is a case for Gil Grissom.

 

[RetardedBastard]

The http://news.yahoo.com/s/ap/20070912/ap_on_re_eu/shrinking_kilogram, but about 50 micrograms!

Zz.

You forgot to mention which diet plan was followed?

 

[ZapperZ]

You forgot to mention which diet plan was followed?

That's because the article didn't mention any. But I bet it wasn't Atkins.

Zz.

 

[zoobyshoe]

50 micrograms is roughly equivalent to the weight of a fingerprint.

It's not clear whether the original has become lighter, or the national prototypes have become heavier...

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.

I suspect the copies have all simply picked up varying amounts of mass by contact with other things during transportation to and from the Institute.

 

[Mallignamius]

So, just picking one up would increase the weight?

Isn't it possible that during transport, the bumpy bumping bumps might have transferred something from/to the base it sits on?

 

[Astronuc]

The http://news.yahoo.com/s/ap/20070912/ap_on_re_eu/shrinking_kilogram, but about 50 micrograms!

Look out everyone. We are all heavier! So much for me trying to lose weight!

Zz.

5 parts per 100 million? I have to wonder about the uncertainty in the measuring system. Maybe someone cleaned it.

 

[Jimmy Snyder]

What to they do when they find such a discrepency. Do they lop off 50 micrograms of the material from the heavy ones? Do they just add a fudge factor when they use the heavy ones? To what use do you put a lump of metal that is a whopping 50 million picograms more than a kilogram?

 

[ZapperZ]

5 parts per 100 million? I have to wonder about the uncertainty in the measuring system. Maybe someone cleaned it.

Actually, 50 micrograms is HUGE because we can actually detect a change in mass when just one monolayer of atoms have been formed. Quartz crystal thickness monitor that is commonly used in monitoring thin film deposition can measure such change.

Zz.

 

[jtbell]

Maybe someone cleaned it.

Several years ago, the guy who used to be responsible for cleaning it retired. He apparently had just the right touch, and there was some concern about whether his replacement would be as good. Maybe now we know!

(what a coincidence... I was talking about the standard kilogram and the guy who cleaned it, just a half hour ago in my General Physics class.)

 

[Moonbear]

Actually, 50 micrograms is HUGE because we can actually detect a change in mass when just one monolayer of atoms have been formed. Quartz crystal thickness monitor that is commonly used in monitoring thin film deposition can measure such change.

Zz.

I recently received a whopping 30 micrograms of a protein...had to go a bit on faith that it was really in the vial it was shipped in...there was a tiny speck at the bottom, barely visible by eye. Just a bit of residue from dust or handling, or even from the cleaning solutions used to remove dust and fingerprints could quickly account for that much of a difference. I'm just not sure how you determine the direction of change when you're talking about THE standard. If that is THE standard, then by definition, the other replicates have gained weight, have they not? How could you determine otherwise if there is no back-up, untouched standard to compare it with?

How often are the standards checked and compared? If it was something like slow radioactive decay, you would see a very gradual divergence in the weights of the standards produced at different times, not a sudden divergence.

 

[Jimmy Snyder]

Here is an idea from Tim Sverduk, my friend and colleague. All particles in the universe are constantly losing mass. By traveling, the particles in the copies have 'lived' for a shorter time and thus have not lost as much mass. I doubt it is true, but I think it should be an interesting exercise to disprove it.

 

[vivesdn]

What about vapour pressure?

 

[RetardedBastard]

I'm just not sure how you determine the direction of change when you're talking about THE standard.

Well, according to one of the guys the article quoted says

the reference kilo appears to have lost 50 micrograms compared with the average of dozens of copies."

If that is THE standard, then by definition, the other replicates have gained weight, have they not? How could you determine otherwise if there is no back-up, untouched standard to compare it with?

Well, the guy who's the "senior researcher" says

"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."

How often are the standards checked and compared? If it was something like slow radioactive decay, you would see a very gradual divergence in the weights of the standards produced at different times, not a sudden divergence.

According to the "Journal of Research of the National Institute of Standards and Technolog"[1]

[T]he prototypes serving as national standards of mass must be returned periodically to the BIPM for calibration either on an individual basis, which could be done anytime, or as part of a simultaneous recalibration of all the prototypes known as "periodic verification." Since the existence of the prototypes there has been only three such periodic verifications. The latest one, the third periodic verification, took place between 1988 and 1992.

So, 3 verifications since 1879 (when the prototype was made) would be less than once every 40 years?

Picture of the international kilogram prototype

[1] Journal of Research of the National Institute of Standards and Technology, January-Febuary, 2001 by Z.J. Jabbour, S.L.Yaniv

 

[Danger]

That's a cool link, RB. It's quite a bit more complicated than I'd figured.
Any chance that the copies, being kept under less stringent quarantine, are slowly absorbing things like beta particles and neutrinos that the original isn't exposed to?

 

[Bystander]

The copies, being more recently manufactured, do NOT contain as many pits, fissures, slag and flux inclusions, and other flaws as the prototype. The fact that the mass of the prototype varies up and down has been recognized as a "weakness" of SI for some time; for at least the past thirty years (could be longer) there has been interest in retiring the prototype to museum status and redefining the kilogram as the average of the copy masses.

 

[Loren Booda]

The Earth burped.

 

[rewebster]

I think the original and really the original process in making the 'original' is the culprit. Who knows that micro-components were included in the original at the time it was created. There could have been small amounts of 'something' that could have evaporated or sublimated away, even if it could have been ever so slowly over the last 50 or 100 years to do.

 

[RetardedBastard]

That's a cool link, RB.

Thanks, thought so myself :)

 

[cybernomad]

To solve a mystery don't create new physics for one case.

 

[rewebster]

Part of the problem could be in the shape even; (I'm thinking that the loss could be from multiple reasons)--besides loss from evaporation and/or sublimation, the 'cylinder' shape may not help. Even if the 'weight' has only been 'picked up' three or four times, the shape adds to an 'amount' of friction along the sides for the size and weight. Someone has to have a strong grip to lift such a weight for the size, and the amount of grip on the sides has to have a microscopic 'sandpaper' effect to the sides of the cylinder.

A better shape may have been a mushroom shape where the lifting could be applied to the 'underneath' lip as to not apply any 'friction'.---and the metal atoms/molecules/alloy may have not the 'best' intra-bonding between them for the metal itself.

I think if there could have been found a strong dense crystal that had been 'found' in similar environmental surroundings as what they like to store the weight, and shape it like a mushroom/'lipped' design--that may have been better with a single atomic layer of 'something' to 'see' if there was any loss from the handling.--and put diamonds at the 'lift' points on the underneath side for diamond tipped lifting devices.

They could 'test' whether there is any loss by evaporation or sublimation by putting the 'cylinder' in a contained jar and test the air later for particulates, etc.

I'd set up three or four other 'test jars' to test the 'air' /'some other gas' for material used for/in the jars, and/or even in a vacuum to see if 'anything' gets 'sucked' out of the cylinder. Even if the original cylinder was 99.9999 % 'pure' (good old Ivory soap at 99 44/100ths), that still leaves room for 'impurities'.

 

[Ivan Seeking]

It has been determined that this is the fault of George Bush.

The universe can only sustain a finite amount of spin.

 

[billiards]

The Earth burped.

That's what I was thinking, if g changed slightly in Paris then the weight would change accordingly. The lowering of g could be achieved by a very slight amount of tectonic uplift.

Also: the kg should be standardized too a precise number of carbon atoms or something.

 

[Gokul43201]

That's what I was thinking, if g changed slightly in Paris then the weight would change accordingly. The lowering of g could be achieved by a very slight amount of tectonic uplift.

I think we can rule that out because any comparison of masses (or weights) would require both objects to be at the same place (eg: in Paris).

Also: the kg should be standardized too a precise number of carbon atoms or something.

And how would you go about counting these atoms?

 

[NeoDevin]

And how would you go about counting these atoms?

Have your grad student do it...

 

[billiards]

I think we can rule that out because any comparison of masses (or weights) would require both objects to be at the same place (eg: in Paris).

Oh right, I was not aware that they had carried out the calibration at the same location, although now I think about it I don't see how else they could have really done it. In this case I will go with the "mass changed due to handling" argument, because in order for the masses to be in the same place at once, it is necessary for them to be handled.

And how would you go about counting these atoms?

Counting them? No. I wasn't thinking aong those lines, I was thinking more along the "how would you tell an alien species what a kg was?" pattern of thought. You could specify a finite number of carbon 12 atoms and then they could interpolate the exact weight you meant by integrating knowledge of the weight of a carbon 12 atom (which should be universal) in terms of their own practical weighting system.

 

[Moridin]

Scientists have been trying to find a natural reference for the kilogram for quite some time - as it is the only one left (of the SI base units) that is defined by a man-made object. The atomic mass unit has been proposed but there are a few problems, as hinted above. We can compare objects of a human size with the standard kilogram quite well, and compare the mass of atoms and so on compared to the carbon-12 atom, but the tricky part is between the two.

 

[mgb_phys]

Have your grad student do it...

There is a project to do this with a silicon sphere and use x-ray crystalography to precisely measure the atomic spacing then use the size of the sphere to calculate the number of atoms present. ( details in my post above)

At the moment this looks like a better bet than the Planck balance.