Slashdot Mirror
Perfect Silicon Sphere to Redefine the Kilogram
MrCreosote writes "The Age reports optical specialists at CSIRO are helping create a new standard for the kilogram, based on a precise number of atoms in a perfect sphere of silicon. This will replace the International Prototype, a lump of metal alloy in a vault in Paris."
I found some alternate theories that are also attempting to precisely measure the kilogram at everything2. They look pretty interesting, here's a small excerpt:
Hey wait, TFA skims over what they're going to do with the Silicon ball once its made. Again, from everything1:
I can explain it for you, but I can't understand it for you.
Women are perfect, and they're physical objects. Or at least they've always told me that...
... no sphere made of atoms will ever be a perfect one.
Second, if that rusty lump in Paris defines what a kilogram is, in no way is this sphere gonna change that.
My 0.02 cents
No, it's impossible. What they -really- mean is that it'll be perfect as far as we are able to measure it. And it has absolutely nothing to do with what is really important here: They are counting the atoms of silicon in a kilogram and will use that measurement as the basis for the kilogram, instead of some lump of metal in a vault.
The kilogram will not change, only a proposed scientific definition of it.
The sphere doesn't mean -anything- except that it'll weight exactly a kilogram and be amazingly round.
There's either a lot of media spin, or someone's attempt to get his work recognized and used. From what I can see, there's not a single soul that has dedicated to USING this new scientific definition, other than those directly involved with the project.
"If you make people think they're thinking, they'll love you; But if you really make them think, they'll hate you." - DM
Ok... now.. does it have to be a sphere at all, why not cube? Hey silicon spheres.. perfect for implants!
--------- Cheng Ee well well
Well, at the end of the day you can't build with physical objects, even as tiny as atoms, a perfectly spherical shape. So this point is moot anyway. They probably meant "more precise than ever created".
Global warming is a cube.
is because they are embarrassed of the fact that a T-rex managed to steal the original one and now they need a replacement.
Monstar L
Hey c'mon. It's gotta be easier than flying to paris and going through security to get into that vault every time you want to weigh something.
..but how can they make sure the new kilogram weighs a kilogram? :)
"but can you ever really get a perfect anything?"
The whole notion of "silicon balls" sounds fake to me!
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
May God have mercy on your soul if you ever attempt to call a woman a physical object to her face.
Because it's 'scientific' that way. This is apparently someone's pet project and they are acting like the world has asked them to do it.
I'm not against the project, and I think it'll be nice to have a more scientific definition, but it doesn't change -anything-. A kg is still a kg. There is no scientific theory being used to create the 'perfect weight system' or anything like that. They are merely measuring what already exists and using it.
"If you make people think they're thinking, they'll love you; But if you really make them think, they'll hate you." - DM
(1 000 / 28.09) * 6.02 * (10^23) = 2.14311143 × 10^25
Why does redefining 1 kilogram to be one kilogram important? or is SI an abbreviation for silicon?
And funny how a silicon 'sphere' is to be the 'roundest object ever'
# cat
A kilogram was equal to 1000 millilitres of water and that 1000 millilitres of water would fit into a space 10cm cubed.
If they've already defined the metre using constants, isn't something like this the best way of defining a kilogram.
thank God the internet isn't a human right.
The point of having a physical object is that it can be used as a root for calibrating devices. From there you can calibrate more devices on each other. The further you get, the less likely you are to be precise, but the chances are pretty good that little deviations up and down will cancel out overall. But it's absolutely important to have an exact starting point, and a physical object is the only way to do that.
It's a lot easier to measure a large object than a small one and multiply it, since a small error will also multiply out. What I don't get is how they intend to build an exact number of atoms into the sphere. You would need some other exact measurement, like number of electrons for calculating precise electrolysis procedures.
Sam ty sig.
Except for the challenges of making one, what's it useful for? You can't use it to calibrate anything, the wear and tear caused by the friction of handling would eventually change it's mass and defy it's purpose. Is the actual "finished product" good for anything else than sitting in another vault somewhere?
.: Max Romantschuk
Of course you've already heard about this in the EU. Slashdot is a primarily US focused site, and as we all know the US is stuck with retarded imperial measurements. No wonder we lag behind the rest of the world in education, jobs, and I see now we've dropped in broadband penetration as well.
>May God have mercy on your soul if you ever attempt to call a woman a physical object to her face.
Especially if he compares her to a perfect sphere.
A perfect sphere, down to the atom, of 1 kg silicon would require pi to what precision?
Dan East
Better known as 318230.
"Why do we have to have an actual object to define a weight?"
Kinda like asking: why do we need space to define distance? - The reason is that only physical objects posses mass (to be pedantic you also need the planet Earth to define weight).
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Didn't David Bowie have a few of these the institute could borrow instead of making new ones? Just keep them away from baby sitters.
Jonathanjk.com
It's important enough for laboratories in Germany, Italy, Belgium, Japan, Australia and USA to invest a great deal of time and effort.
The spheres are being made by CSIRO's Centre for Precision Optics. They've been making precision spheres for research since the late '80s, and have all the recognition they need from anyone who has a clue.
Have a look here; http://www.tip.csiro.au/IMP/Optical/spheres.htm. It might help you understand the project better.
"I've got more toys than Teruhisa Kitahara."
We have a LOT of Pi now don't we?
I don't know if we have enough now, but surely if we DO have enough pi that any errors in the count introduced from the inaccuracy of pi are significantly less than 1 atom, then it would be sufficient, oder?
Want pie now!
I've lived all my life in countries that use the metric system, so I have to ask... does the pound have an "official reference" like the kilogram?
So say we all
Mass is constant (assuming it is at rest), and has nothing to do with the force of gravity on an object. The mass times gravitational acceleration is the weight, often reported in lbs or Newtons. In other words, a kilogram here is a kilogram everywhere.
BTW, in the English measurement system, mass is measured in stones.
That's a lotta light!
Vote monkeys into Congress. They are cheaper and more trustworthy.
It makes the calculations simpler.
How do they account for different isotopes? Or do they just get a sphere that weighs the same as N many atoms of pure silicon 28 would weigh?
I rarely criticize things I don't care about.
Funniest comeback, eva!
And did you exchange a walk on part in the war for a lead role in a cage? - Pink Floyd.
Its not hard to change. We did it in the early '70's here in Australia. That would have been the ideal time, right after the Apollo program ended with everybody upbeat about the future. It just takes a will to change.
http://michaelsmith.id.au
A lot of units can be defined using physical properties : a second is 9,192,631,770 periods of a precise physical reaction (transition between the two hyperfine levels of the ground state of the caesium-133 atom according to the wikipedia), a meter is the distance travelled by light in a 1/299,792,458 of a second and so one, Volts, Joules, etc... are defined this way. Mass, however, was not yet related to physics constants. So there is a "yardstick" for kilograms. A platinium cylinder was made a century ago, the closest we could get to what was considered a kilogram at this time and it was proclaimed "the exact measurement of a kilogram is the mass of this particular object". It is stored somewhere in Paris. I am sure that modern scientists will manage to conceive an experiment with a great precision to transform the kilogram unit into the abstraction it is supposed to be.
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
And at this level of precision the location of the measurement may be very important. I don't think you could take this sphere to a different latitude and get an accurate calibration.
http://michaelsmith.id.au
The CSIRO project is about determining how many silicon atoms are equivalent in mass to the current standard kilogram. Once that number is established the actual kilogram in Paris is redundant. If it gets lost or destroyed we can reconstruct the kilogram by counting out 'n' silicon atoms. It also means anyone can construct their own kilogram by counting out 'n' silicon atoms, without having to go to Paris to do a comparison.
It is a separate (but related) project to figure out the second part of the project: how to easily count out 'n' silicon atoms, so creating a universally available standard. One way might be to make a silicon sphere, like the CSIRO, but most people don't have the ability to do that.
I guess it would be used to calibrate a (limited by wear and tear, yes) number of "second generation" reference weights. Which would obviously not be quite as accurate, but still good enough to serve as reference to calibrate commercially weights and weighing machines.
The great advantage of this approach is that you can reproduce the original reference weight if necessary, while the loss of the current prototype would mean a much bigger problem.
C - the footgun of programming languages
silicon spheres will define the standard ... will they be coming in pairs by any chance?
Would you rather a square? =)
Reminds me of a story - a friend had gotten a boob-job and we were all out for dinner one night. Another common friend of ours hadn't known this and the first time he saw her, he burst out - "You've grown three dimensionally!"
OK, someone's going to have to explain this for me. Why do we have to have an actual object to define a weight?
:) It's also mentioned that a similar approach was taken to defining the meter, based on an absolute definition of the speed of light.
You don't. That's just the way we've done it in the past. I read a really interesting article a couple months ago in American Scientist magazine called An Exact Value for Avogadro's Number that addresses exactly this question. In the past, Avogadro's Number (6.02andchange x 10^23) was defined experimentally, based on the reference kilogram. These scientists propose reversing that -- defining the number absolutely, based on the number of atoms of a particular element that fit within a sphere of a certain size. It's sort of similar to what they're doing with the silicon sphere, but it's all done on paper, rather than by actually manufacturing an artifact.
The advantage of this, they say, is that the number will remain constant and not be affected over time as refinements in building and measuring such "reference kilograms" change the accepted mass of a kilogram. They make several other arguments, as well, but it's much better if you just read the article.
Jenna Jameson do your part for science.
an atom might have an diameter of about 0.1 nm, they say they have a perfect sphere which is just 35nm from being perfect, what ever that means. So you don't need that many positions of PI at all..
One horsepower is the power of the reference horse in an archive in Paris.
Swedish plasma phys. PhD student; MSc EE; knows maths, programming, electronics; finance interest; seeks opportunities
No, we can just keep calculating it further and further until we get enough accuracy to get the correct number of atoms (since there will be an integer number of atoms, the inaccuracy will be lost in the rounding).
Yes, the fact that we only know pi to a couple billion digits will certainly make this definition completely useless!
That's why you use beer. I liter of cold beer will be one kilo. Actually you add one sip to compensate for the bubbles which as as a salt and therefore increase the density.
I prefer Flambe as apposed flamebait.
Ok, people are giving snarky answers here, but I'll try to give you a more straight answer.
The only way we have to keep a standard unit is to have an object with that unit and call that the standard. Let's say you were building some sort of a scale that would measure weight in kilograms; you'd have to calibrate it first. This means that you'd have to find an existing weight that was one kilogram, put it on the scale, and mark that this weight is a kilogram. But then how do you find a 1 kilogram weight? You have to measure it on some scale that's already calibrated correctly. This chain continues, and has to end somewhere.
So the two questions I anticipate are:
To answer the first question, a scale would be harder to maintain accurately. It could break, and calibrations don't hold forever. You'd have to re-calibrate it every so often, and how do you do that without an object known to be exactly 1kg?
The answer to the second question (which I imagine might have been your question all along) is a little more complicated. Let's imagine that we have no exact 1kg object stored anywhere that we use as the standard. So one guy in a lab is using an iron ball as his 1kg weight, calibrating scales with it, and selling scales to others. The iron ball slowly rusts over time, and the weight of the ball changes a little. Someone takes one of the scales calibrated with the rusty balls and does the same thing, but this time with his own hunk of iron, but the environmental conditions in this guy's lab aren't as controlled, and he tends to get water condensation on his iron ball, meaning it rusts faster and each calibration varies depending on how much water has collected.
Now, imagine it keeps on like this for 75 years, with different guys selling scales, getting their original measure from someone else, and then using their less-than-perfect means to continue calibrating and making scales. After 75 years, there are some drastically different "kilograms" floating around I buy a scale, measure out 1 kilogram, take it to a different scale and get 1.5 kilograms, while another says .75 kilograms. In this case, who's kilogram is "correct"? When the issue was raised, people would say, "Oh, if only we had a standard "kilogram" to compare them to!"
And so we have someone keep a physical reference object under very controlled conditions and of materials that will prevent corrosion or other corruption to the material.
No it's not. I really wonder what the deal is with mass and weight that it gets everyone confused like that. Mass is the resistance of a body to accelleration (or gravity, which if you subscribe to the strong equivalence principle is really the same thing). It is measured in kilograms. Weight is the force that gravity exerts on a body, measured in Newton. They are related via the gravitational constant, which is not really constant.
Pathman, Free (as in GPL) 3D Pac Man
So why not invoke relativity and define the kilogram to be the mass-equivalent of the energy contained in umpty-ump photons of some wavelength of light?
Standards for weights, mass, distance or any other measure, are critical in the calibration of instruments. This calibration provide the means that to compare product specifications and research results.
? ttype=2&tid=6345/
This particular effort is a very interesting set of challenges. It requires the use of single isotope of silicon; calibrations for distance and roundness, and a sophisticated means to to count the atoms. This last step requires the silicon to be perfectly crystalline.
Measurement is itself a very interesting study bordering on metaphysics and philosophy. The desire to measure things has been at the heart of a lot of scientific investigation, economics and other areas of study. Ref "Abstract Measurement Theory" by Louis Narens https://mitpress.mit.edu/catalog/item/default.asp
"If all the American people want is security, let them live in prisons." Eisenhower
Talk to one some time ;)
Silicon is radioactive now?
Actually, the official unit of mass in FPS system is the "slug".
I am not a crackpot.
Very simply: it is very difficult to define mass in terms of something else. With distance, time, etc, it has been fairly easy to define these as so many wavelenths or so many vibrations, but measuring out a specific mass of something (by counting atoms, in this case) has until very recently been impossible. Metrology (the science of measuring) is a subject area rather taken for granted, but it does underpin everything else we do. How else do you know your voltmeter/light meter/kitchen scales/power supply/ruler is accurate enough to do the job you need it to do?
[FUCK BETA]
???
The kg is a unit of mass, not weight.
I am not a crackpot.
Yup. I am an idiot. Please disregard my nonsense. Move along!
Weird. I read about this in an exam I took last week. It stated that the present standard kilogram is a mass of platinum and iridium kept at STP underground, and asked what factors might affect the mass of the standard kilogram when it is measured. I answered if any isotopes of platinum or iridium decay, or if the standard kilogram had a velocity close to the speed of light.
You are being very dense here.
TODAY: 1kg = the mass of the "rusty lump" in Paris. We don't know how many atoms of Ir and Pt the "rusty lump" have. So, if the "rusty lump" changes mass (and it changes with time because of being rustier all the time) AND because the "rusty lump" is used to calibrate scales all over the world, the kilogram is effectively changing with time. This is BAD.
WHAT THE GUYS ARE DOING: they are trying to make the most perfect silicon sphere possible that weights the same as the "rusty lump". Once they get to do that, they will count the atoms of silicon on the sphere, using interferometry. Suppose the # of atoms of the shpere is M.
WHAT WILL WE GOT THEN: 1kg = M atoms of silicon. This definition will never change, and if the silicon spheres rust or break or change weight by any circunstances, we make new ones with M atoms and we have a forever-constant definition of a kilogram. This is GOOD.
Got it? They did the a similar thing with the meter -- the original was a rod roughly 1m in size, then they did some measurements and said (*) "oh, one meter is the length that the light takes 1/299,792,458 of a second to go through in vacuum." and now they can do as many calibrating rods as needed, provided they make them the length that the light takes 1/299,792,458 of a second to go thru.
(*) actually the meter had an intermediate definition of "1,650,763.73 wavelengths of the orange-red emission line in the electromagnetic spectrum of the krypton-86 atom in a vacuum", but the new definition has the advantage of setting the light speed at exactly 299,792,458 m/s.
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
My broadband gets 400000000 gils per fortnight, and that's the way I likes it!
I am not a crackpot.
She'll get over it when she finds the perfecltly useful gram of coke on the coffee table.
I'd prefer A non-perfect sphere of Silicone .
Nothing sucks like a Vax, nothing blows like a PowerMac G4
No, it's widely accepted as a necessary step towards being able to define the unit of mass in terms of a specific number of carbon 12 atoms. Look, it would be a lot better for this discussion if you made the effort to learn what the project was for.
Just because you personally don't understand it doesn't make it "media spin" or otherwise redundant. There's more information here http://www.npl.co.uk/mass/avogadro.html, including an FAQ which might clear up some of your misconceptions.
"I've got more toys than Teruhisa Kitahara."
Defining mass buy by sherical objects is not new. The British Standard Apple has a mass of 102 grams. Thus under a standard gravity there is a force of 1 Newton.
As far as i can remember, in my physics or chemistry classes at school, 1Kg was always defined as a number of carbon-12 atoms... 1/12*1000*Na*atoms of C12. Looking it up on the net it seems to be project Avogrado. By the way first time i was given that definition at school was in the late 80's.
we don't know how many silicium atoms there are in one standard kilogram. The thing they are doing is to measure exactly that, so they can proclaim after: "1 kg is X silicium atoms."
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
They don't. What is important is to know the mass of the sphere preciesely not for the sphere to be precisely one kilogram.
and it's not weight, is mass... but I digress... today, we do have an actual object defining what is 1kg of mass. We want to escape that, so we are doing the most perfect possible silicon sphere with 1kg of mass, we will count the number of silicon atoms on it, and we will proclaim that 1kg = the mass of X silicon atoms.
It's better to be the foot on the boot than the face on the pavement. ~~ tkx Kadin2048
It's true I tell you, feller at work's next door neighbour read it in the paper.
A new standard is needed because the "standard kilogram" held in France has been slowly losing mass, about 50 micrograms in the last 100 years, compared to other reference masses. It's not known how this has occurred.
2 7/023252
Wikipedia - Kilogram
http://en.wikipedia.org/wiki/Kilogram
Slashdot: The Changing Definition of 'Kilogram'
http://science.slashdot.org/article.pl?sid=03/05/
Paid Q&A/Research
The real purpose of the project is to produce a reproducable standard. If something was to happen to the lump of metal that currently defines a kilogram, there is no reliable way to reproduce it. You can make another lump of metal and weigh it, but even the most precise scale we have been calibrated back to the original lump of metal plus or minus the error of the machine. The problem is that the errors are cumulative. If we have to replace the lump of metal several times, it will be less and less precise. If however we can base the weight on a physical constant, then we can use that physical constant to calibrate future scales on. There will be errors based on the precision of the machine, but they are no longer cumulative. If you build a more precise machine, you get a more precise measurement.
Yup. I am an idiot. That was pre-first-cup-of-coffee. D=M/V not W=M/V.
.....I can't possibly be the only alpha geek out there who immediately associates a perfect silicon sphere with this:
http://www.dcs.gla.ac.uk/~hwloidl/htg-all.html
(see #48)
The problem with quotes on the internet, is that nobody bothers to check their veracity. -- Abraham Lincoln
"Zut alors! Pierre, le sphere parfait - ou est-ce que tu le placer?
"C'etait sur le table, Jean-Claude"
"Merde, il avait roller sous le sofa encore!"
----------------------------------- My Other Sig Is Hilarious -----------------------------------
Actually, this happened 220 years ago and the Americans fought the British over this. Then George Washington went to the Queen and this conversation ensued
GW: You're British...call your 'kilogram' something else...
Queen: How about you do it?
GW: Well, my kilogram is correct... you 'kilogram' is wrong
Queen: Really?
GW: Yeah! Put yours against mine on a scale...See? You don't have a kilogram iron ball.
Queen: Aw shucks! sorry about the war man... Alright, since I am British, we call my kilogram a 'pound'. Kind of like an English 'kilogram'... like an English Unit
GW: Ok...that's cool... so we call the war off?
Queen: Sure!
GW: Ok listen... I'll be embarrassed if I tell these guys that I took them to war over this instead of clearing this misunderstanding like we just did.
Queen: And I'll be embarrassed if my guys find out that we've been using a wrong kilogram
GW: How about you give me the continent and I'll let you use our kilogram?
Queen: That's cool, but then I am losing a continent...
GW: Ok... how about this? I'll use your 'English Units' so that you can make fun of us later...
Cheers! -- Vig
Atheist: Buddhist in a Prius
I wonder why they use a sphere. To me it seems more logical to use a silicon crystal of known dimensions. Crystals are guaranteed to have integer number of atom planes whereas sphere is somewhat diffuse on the edges.
I remember a small magazine (called Science Digest, IIRC) I read in the mid 80's. It was short little science articles, probably a couple hundred words each (at most)...not unlike RSS feeds today, perhaps.
One article was about scientists making the most perfect sphere to date out of some crystal. It was measured to be so perfectly round that if you scaled it up to the size of the earth, it's highest peak would be 12 feet higher than it's lowest point.
I'm sure the technology for this thing has improved a lot in 20 years.
I mean, come on, would you Australians to define scientific standards? I won't!
For starters, those guys believe the South is on the top and North is at the bottom of the maps! I feel upside down just thinking of it. And on which side of the road are they driving already? North or south? See: you cannot trust those guys!
Second, the issue with "the" current "reference" in Paris (there are three cylinders in fact) is that is loses atoms sometimes, so its mass diminishes. I mean it is still The Kilogramme but the kilogramme is not what it was some years ago when the grass was greener and the boys were nice and, hum! Anyway, how would that be different with yet another physical object? Wouldn't it lose some random atoms from time to time?
Third, it is well known that international standards are defined in Paris: the internationnal skirts lenght association, the general contest of retreat speed and the cheese-smelling index are all defined in my city and everybody agrees with that. M. Sarkozy has just battled staunchly with M. Puttin to assert our rights on those essential fields.
Finally, I suspect that the kilogramme may be re-defined in October 2007 in Paris (http://fr.wikipedia.org/wiki/Kilogramme): a meeting of the Bureau Internationnal des Poids et Mesures (BIPM, Internationnal Weights and Measures Bureau in French) is scheduled this year.
Best kisses from Earth.
I am not Remy Mouton, unfortunately: http://remy.mouton.free.fr/art/
is going to be a crystal ball? Woo hoo!
Pffft! Metric system!
The King had it right all along...
C = 1'/ns
the speed of light = 0.983571056 feet per nanosecond
I'm sure we can come up with something similar for pounds and fahrenheit eventually.
Nouvelles de jeux et technologies en français. TC
Estimating the diameter of the spehere in the picture to around 12 cm and assuming the final spehere is the same approximate size: If the final sphere was magnified to the size of the earth, it would have surface variation of 9.5 cm in altitude. Pretty slick - although I bet that within a week at least one american will find a way to trip and sue them into oblivion.
There goes my confusion between English units and Imperial units again. Let's abolish them ALL in favor of metric!
A friend with a boob job? This is Slashdot so you're obviously not talking about a female (I'll ignore the "her" and assume it's a typo.). Who got the boob job? Is his name Robert Paulson?
Tiller's Rule: Never use a word in written form that you've only heard and never read. You will end up looking foolish.
Currently the kilogram is defined by the "lump in paris". As some the previous posters already pointed out this is a Bad Thing (tm).
Better would be to say the kilogram is the mass of n atoms of y. Problem is: how many atoms has one kg of y?
Actually you have to count them, and one good way to count it is to use a crystal with a well understood structure.
You simply grow a near perfect crystal, measure the size and you can calculate the number of atoms. That's what they build these silicon (=crystal) spheres for.
Now they just have to get the precision at least as good as the current definition (which means they have to be 10 times as precise), so noone will not notice the switch of the two definitions, and we don't need that "lump" in paris anymore.
Worse - you can't touch the Sphere of One-ness with anything.
... in a vacuum chamber ... at the bottom of a flight of stairs, in a disused lavatory with a sign on the door reading "prendre garde du léopard."
Q: May I put my greasy paws on it?
A: No. Fingerprints will alter the mass in a measureable way.
Q: White gloves?
A: Abrasive.
Q: Use a special cradle that's machined to exactly the same radius profile such that you won't scratch or deform the Sphere of One-ness?
A: Nope. That'll result in a molecular interference fit. You'll never get the two pieces apart.
So ultimately, they're building a very precise bauble that no one will ever be allowed to touch. I suspect that bouncing photons off the surface may displace an atom or two, so they'll keep it in a dark room
Well, back in the 18th century when the original system was set up using physical objects was about the best they could do. The meter was based on a percentage of the earth's meridian and the kilogram is derived from volume of water at maximum density. However that turned out to be a variable number, even using the same container, because of issues with pressure.
...you need the lump of iridium-platinum. And that measurement will be limited by the tiny change in mass that appears to be happening with no explanation.
In the late 19th century the iridium-platinum prototype was created that were accepted to be equal to the mass of a "kilogram" of water under the conditions expected at the time of definition. Actually, three of them were created and stored in different locations to provide a check against any mass drift in the prototypes. Multiple copies have been made over the years delivered to nations across the planet to provide their own base references. There is apparently some change in mass but no one can explain why, and this is important.
The problem is that in the interim the other units have been changed to something that can be derived. Time is based on a certain number of cycles in a cesium atom at absolute zero. Length is defined as the speed of light in a vacuum in one second. The kicker here is that as improved measuring devices appear, the accuracy of the meter and second only improve as the new measurements add extra digits off the decimal place. Anybody can do them, anywhere. Build an experimental chamber that gets closer to absolute zero and has more sensitive cesium detector = more accurate measurement of a second. Build an experimental chamber that gets closer to absolute vacuum and a more accurate measurement of a second = more accurate measurement of a meter.
To develop a more accurate measurement of a kilogram and
Once a kilogram is defined as X atoms of silicon, anyone with a silicon atom counter can make their own base unit for equipment calibration.
I've been on slashdot so long I'm starting to get out of touch with the cool stuff if it ain't on slashdot.
0.454 kg is defined as exactly 1 pound. ;)
we would be completly metric for year now if Reagan hadn't killed it. Yet another reason to pee on his grave.
The Kruger Dunning explains most post on
This example of the quantising effect of a superconducting ring is given early in Carver Mead's fairly straightforward text, Collective Electrodynamics.
Wikileaks, no DNS
But what abstraction is it supposed to be?
According to some googling.. 1000 times the mass of 1 cubic centimeter of water. But then that just comes back to the original problem with this definition. Pressure and temperature effect this definition.
So what are they aiming to set the kilogram as? Many SI units, and measurements we've made, are based around the international prototype.
Are they just trying to define the mass of the international prototype in terms of atoms?
I can't believe an AC is the only one to mention the Horta!
All the Trek geeks must be arguing over the poll question.
I know this is kind of weird...but I've always fantasized abotu sneaking into that vault in Paris and filing a little bit off the kilogram mass standard. And maybe just trimming down the end of the meter stick a bit. On some level I feel like if you could do this, the world would be plunged into chaos within a few weeks.
Please don't hurt the Horta!
Mass and weight are related by the accleration due to gravity, g. F = m*g This value varies with position. The Gravitaional constant, G, is a constant. This value is fixed throughout the universe. It can also relate mass and weight through the equation F = G(m1*m2)/(r^2)
I swear, those guys down there weigh my kilos short every time.
The goal is to get a measure as precise as possible of the international prototype and transform it into a definition that can have an arbitrary precision or at least a precision superseeding today's limitations like "a kilogram is the mass of X atoms of silicon".
The Wise adapts himself to the world. The Fool adapts the world to himself. Therefore, all progress depends on the Fool.
(since there will be an integer number of atoms, the inaccuracy will be lost in the rounding)
:D
We split the atom years and years ago, so thats not a problem; we'll just have a load of half/quarter/eigth atoms around the edge. In fact, there's probably a load of spare atom parts lying around somewhere that could be used for just such a purpose!
There IS NO exact Kg. Its only defined to a value with a limited number of digits.
Lets say the current kg is exact on 9 digits.
If you have any new definition, which has more digits (for example 22, as in the number of silicon atoms in one kg), it wont be the same number.
Of course its not, as its more accurate.
The new definition will be a NEW value for the kg, which is more precise, and within the uncertaincy of the old definition.
Thats the same way like when they changed the meter. It actually shrunk a few parts of Angström during the redefinition, but it didnt matter, as it wasnt reproducable to that extend before.
HI O WISE PRINCE. WHT TOOK U SO DAM LONG?
Does it look and feel like the real thing? /Sili-what? oh.
*slight crashing sound*
Weight is a force.
Gravitational attraction is an acceleration (see A. Einstien et al).
Therefore
Weight=mass times accelation
or
F=ma
It also matters from a philosophy-of-science perspective *to the metric system.* While in practical terms it's the usefulness of the metric system which stands as its ultimate justification, it also helps keep the metric system on the same page as good scientific practice if its basic postulates are somehow empirically verifiable. Imagine what it would be like if the metric system was based on the idea of the length of the staff of God, or on the number of angels who can dance on the head of a pin. It doesn't fit right with the rest of the scientific project -- it's like putting peanut butter in your spaghetti sauce. If the metric system *was* set up this way, one can imagine it feeling competitive pressure from a similarly efficient and congenial system of measure based on the empirically verifiable properties of middle-sized objects; e.g., spheres of silicon. Now, you might not think that much is gained by going from a chunk of platinum to a sphere of silicon, but science is all about incremental improvements, and (as the article and other posters point out) there are certain properties of a silicon sphere which make it a more reliable/stable proxy for the ideal kilogram. (Remember, the closer your empirically verifiable properties are to the ideal properties you postulate, the better your scientific theory.)
- undoware.ca
The point of this is to figure out the exact number of atoms in 1KG. Even if the sphere gets damaged, they should theoretically be able to check it for the number of atoms or just grow another using the same procedure.
What you say is true, but they still need the sphere because a standard for the kilogram already exists. This is a two step process.
Step 1: create a formula that defines mass in the abstract.
Step 2: calibrate that formula as closely as possible to the existing standard.
Step 2 is only necessary to ensure consistency between the new definition of the kilogram and the old (so that a kilogram doesn't suddenly weigh more or less than it used to). If they were creating an entirely new unit of mass, they wouldn't need the sphere, but because the current definition of a kilogram is an object, they need to create an object and count the atoms.
There's some sort of analog-to-digital metaphor involving OCR here but I can't figure it out.
They should be careful with this thing. I heard that if you go inside it, it will give you the ability to manifest your thoughts into reality! Usually situations like that just end up with giant squids attacking your underwater science labs.
Eek!
If they redefine the kilogram, what happens to coefficients that rely on kilograms? For example, for the equation for Universal Gravitational Energy [G=(coefficient)(m1xm2)/d^2)], is the coefficient going to change?
'A friend'
He didn't say girlfriend. I'm sure there are no shortage of losers stuck in the friend zone.
I've seen a number of perfect spheres of silicone, and they typically come in pairs.
As the silicon has a cace-centered cubic crystal structure, a sphere could not be the perfect shape.
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
The weight has been defined upon a lump of platinum since 19th century. ... weight so it depends upon that lump.
Atomic weight is
They will count the number of atoms in the sphere and will multiply it by the atomic weight of silicon.
The weight of the silicon ball will be correct if and only if is will weight the same as the platinum lump, not just because the number of atoms has been precisely defined.
I would prefer to stay with the platinum lump: less hassle!
Maybe Computers will never be as intelligent as Humans.
For sure they won't ever become so stupid. [VR-1988]
expecting something Tiffany Towers related. now_those_are perfect silicone spheres.
oh marmalade.
I don't know about all that, but I gathered the advantage of the silicon balls was that they could give a number of atoms in the sphere. If you base the kilogram on an arbitrary piece of silicon (whatever material you please) and you lose that silicon, then you can't easily replicate that weight again. However, if we posit that the weight of silicon atoms don't change, and you can measure the number of atoms in a silicon sphere, then we'd be able to say, "1 kg = x silicon atoms". Even if you lose that chunk, you can always make a new one.
Of course, I'm not sure I understand how they count the atoms. I'm also not sure how different isotopes of silicon are accounted for. (do they separating out one isotope and use it to make the sphere? Or are they assuming a certain mixture of specific isotopes?) But it seems like the big idea is to give a definition of the kilogram that references a more universal constant that could be replicated.
When you see the flash you count 'till there is the thunder.
When you take the number you counted and devide it by the distant of the thunder; you know exactly how fast you have counted.
If you mod this up, your slashdot background will turn into a beautiful sunset!
Haha. Love the Douglas Adams reference. Such a lead-in, too!
Seriously, though, photons of anywhere near visible frequencies won't displace the atoms; light bouncing is almost always a purely electronic transition thing. And if this thing is ultrapure silicon, atoms are NOT going to want to displace. No worries there.
The Borg haven't even been able to make a perfect sphere, so probably not.
Persistent Volume manager for Kubernetes - https://github.com/dwimsey/openshift-pvmanager
And you are you going to determine if you have x atoms? It will take a long time to count them out. That is the point of this project: to create an object, the sphere, whose number of atoms is known as precisely as possible. If it is a perfect sphere, its volume is precisely known. And if the crystal spacing of silicon is known (which it is, very well), then you have a very precisely known number of silicon atoms. This means that you have a macro-scale object, suitable for use in a balance or equivalent, whose mass is known in terms of unique natural substance rather than an arbitrary lump.
Consciousness is an illusion caused by an excess of self consciousness.
All I know is that thing would make one hell of a bitchin paperweight. I totally want one.
I read Usenet for the articles.
yuo have a sphere that is exceedingly round. They been very careful to make certain it is very precise but to calculate the volume of the sphere don't you depend on a transcendental number call Pi that can be calculated out to so many places but hasn't an end so you're end result for the volume of the thing is going the depend on how namy digits of Pi you decide to bring into the equation. How many digits along do you need to go to reach the point where one more digit of pi results in one half an atom's worth of volume?
Sorry for the stupid question, but I'm a foreigner. What is a "boob job"? Google's "define:boob job" didn't return any results.
This is the most perfect crystal ball ever! We can see the future better than ever before!
Consciousness is an illusion caused by an excess of self consciousness.
This isn't a kilogram; it's a mamogram.
Thank you.
... which weighs 1 Kg. But, alas, the new weight of Kg has been introduced yesterday, so I am afraid that the 1 Kg will now cost you 20% more.
;=)
Yes, you heard that right: for the new Kg is 20% more than the old one ! Don't you just love redefining the metric system ?
Slashdot: stuff for news, nerds that matter, matter for news, stuff that nerd
Yes, but when you try to weigh it, it keeps rolling off the scale.
Figure out how many atoms of carbon-12 are really in a kilogram, and fix Avagadro's number accordingly so 1 mole of carbon 12 had a mass of exactly 12 kilograms.
Use as many significant digits as you need so the current "standard" kilogram is within the margin of measurement error and zero-fill the rest of the number.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
Breast implants.
For future reference, the Urban Dictionary is a good, well, reference for slang terms.
--Glenn
Also, in a few hundred years (or a few hundred-thousand years), people won't have to redo precise (expensive) measurements that were made during the last 100 years, because the information recorded now will have the same meaning over time. Otherwise, people will have to try to guess what the mass of a "2007 kilogram" is compared to what they will be using in the future.
http://outcampaign.org/
> bringing the kilogram into line with other base units such as the metre and the second, which are all defined by physical constants...
One cubic centemeter of H2O is one gram, right? If a "metre" is based on a physical constant and a gram can be derived from it using a physical constant (the mass of water), what's the point of playing with the disco ball thingy?
... I've ever seen is a Horta egg.
Research shows that 67% of those who use the term "research shows", are just making shit up.
Personally, I think years of waiting for the right material and special grinding is a waste of money... I could of pointed them in the right direction if they only had asked. Here, looking for YOUR OWN silicon sphere:
P ACE-HI-TECH-BALL-2-D_W0QQitemZ260110751261QQihZ016 QQcategoryZ3225QQrdZ1QQssPageNameZWD1VQQcmdZViewIt em
:)
http://cgi.ebay.com/Siaz-SILICON-CRYSTAL-SPHERE-S
PS.. This is not my auction, I just KNEW it must exist on ebay if someone needed it.
--- Relax, that mass muderer is just trying to reduce our carbon footprint, one fetus at a time...
Thanks
Molecular interference fit? I should say something smarmy about people who do a poor job at feigning knowledge and expertise, but since there's no Wikipedia article on the phenomenon I'll let it slide. What you are talking about is optical contacting, and has nothing to do with molecular interference. (I'm not even sure what that means in this context.)
It's not a perfect sphere. If you zoom in really really close, it's got the jaggies.
"It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
I'm glad to hear they're making progress on it, this is something I've been looking forward to for a while. ... Yes, really. =) No, I'm not being sarcastic... =(
Slightly OT: Just read up on metric/imperial systems recently, apparently the only ones still really using Imperial are the US, Burma, and Liberia. Oh yeah that's a great crowd... Maybe, once the new measure passes muster, we can finally extricate ourselves from the "axis of incompetence". Or we could go on trying to figure out how many king's big toes are in a furlong...
I use Windows... like a two dollar wh.. why don't I just go ahead and not finish that sentence.
The picture shows a beautiful shot of the perfect silicon sphere. Out of curiosity, I looked very closly at the scene reflected by it's surface, thinking perhaps I might get a glimpse of the photographer. However, he was nowhere to be seen.
Then I got to thinking - it should be easy to reconstruct the scene that is portrayed in the reflection from the surface of the sphere. All that is needed is to cut out the image of the silicon sphere and paste onto the surface of a three dimensional sphere. Then we could rotate it this way and that and look around the scientist's lab. So I did this - using a software simulation. I cut out the silicon sphere from the article's photo, and used it as a texture on a spherical 3D mesh, and added a little code to rotate it back and forth so that I could look around the scientist's lab. Guess what - there is no sign of the photographer! What we see is a very messy lab, with a closed door on the right. There are florescent fixtures on the ceiling that are currently turned off. There is a large window at the end of the room. I do believe that the ceiling, though it meets the left wall at the usual 90 degree angle, curves down to the wall at the right - a very unusual space, as if it was crammed into to an attic. At the extreme right of the room I believe we see a curtain hastily thrown over whatever would have been on the right side of the view. If the photographer is in the room, as he must be, I think he must be kneeling to the left of the window about three-quarters of the way back, and using a telephoto lens.
I have made available the exe that I created on my web site so that you may take a look for yourself. The code is a hasty adaptation of Microsoft's DX3D mesh tutorial "Tut_06Meshes" from the DxSDK 9.0, which is also included. You can get the zip package here. Perhaps you could modify the code to produce an even better view, but unfortunately, the resolution of the original image is really too low to get much out of it. It was a lot of fun doing this, and if you come up with a better result than me I would like to hear from you.
But a sphere is round, so how do you keep it from rolling off the scale when you are trying to weigh it?
This is the best explanation in this whole discussion.
Patrick Doyle
I mod down every jackass who puts his moderation policy in his sig. Oh, wait a sec....
I don't know, but if we're going to steal it we're running out of time!
...but is it art?
because
In other words they want to show off their skillz and know some RA or post doc is going to be messing with it.
Which is really useful I mean knowing the solids never expand or contract with temperature.
If someone is passing you on the right, you are an asshole for driving in the wrong lane.
So, just because you can't find something on Wikipedia you're willing to impugn someone's knowledge and intellectual honesty?
Incidentally, Wikipedia does have an entry for "interference fit". You incorrectly parsed "molecular interference fit" as "molecular interference fit" rather than "molecular interference fit."
For the record I have no idea whether such a phenomenon actually exists but it sounds plausible enough to me that I'm not going to denounce it without doing more than a Wikipedia search.
1) Measure the size of the sphere.
2) Measure how far apart the individual silicon atoms are in the crystal lattice. Since the crystal is approximately perfect, that distance will be constant over the whole sphere.
Through 1 & 2, the number of Si atoms in the sphere is calculable, with nice and low error margins.
Isotope ratios can be calculated from another piece of Si from the same crystal the sphere is made of using mass spectrometry.
Your question demonstrates the rhetorical rationality of arguments *for* stringent immigration laws.
I know a guy that could get them a perfect kilo, seriously, this guy used to eyeball perfect quarter ounces with one eye closed !
Wanna fight ? Bend over, stick your head up your ass, and fight for air.
...my fellow countrymen will never accept the kilogram as a unit of measure until it is redefined as being equal to 16 oz.
At the risk of being pedantic, where did you put your referential, and why?
Rethinking email
All the other basic measurement units where redefined this way at the XX century. Only the kilogram is a troublemaker.
Rethinking email
me.
Gravity Sucks
Don't sweat it, I checked your profile and you aren't a friendless loser. You have fans, three of to be precise.
Article title: "Perfect silicon sphere to redefine the kilogram!"
Slashdot summary: "This will replace the International Prototype!"
Actual content of article: "...could help pave the way..."
Some day. Maybe. Unless one of the other alternatives (watt balance, ion counting, etc) is chosen.
Stop worrying about the risks of nuclear power and start worrying about the risks of not using nuclear power.
How rude
You make a great point about the use of water creating a circular reference (honestly, that was brilliant!), but don't discount the meter reference. Believe it or not, that standard was chosen because it made it easy to reproduce. Further (if I recall correctly), since the meter and the second are both related to the light emission properties of cesium, a competent physicist should be able to inexpensively reproduce either or both with things he already has around the lab. A sample of cesium, a handful of electronics no more complex than a microwave transmitter, an interferometer for the meter, and a mass spectrometer* for the second would do the job. Simple to understand, reproducible with techniques already in common practice (interferometry and mass spectroscopy), inexpensive to build - really, it's a much better standard than it seems at first reading.
*For the standards cognoscenti in the audience, I know that modern second standards don't use mass spectrometers. It would do the job, though, and most physicists have access to one in a pinch.
"Space Exploration is not endless circles in low earth orbit." -Buzz Aldrin
I didn't understand it as rude, but as funny.
Maybe because I'm not an immigrant, nor do I wish to become one. I feel fine on another continent.
He was being sarcastic. Welcome to the US of A :)
In orbir you ARE weightless. Just as you are in a free-falling elevator.
But you have mass. And this will transpose into weight when you, ummm.. decelerate at the bottom of the shaft.
- Ze Laws ov Termodynamics? BAH!
Kelvin vas a fool!
Mit Hydrogen + Pinoqachole ve can break zes laws anytime!