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Roundest Object In the World Created
holy_calamity writes "An international research group has created the most perfect spheres ever made, in a bid to pin down a definition of the kilogram. It should be possible to count exactly the number of atoms in one of the roughly 9cm silicon spheres to define the unit. Currently the kilogram is defined only by a 120-year-old lump of platinum in Paris, but its mass is changing relative to copies held elsewhere. Other SI units have more systematic definitions."
Did anyone else read "An international research group has created the most perfect spheres ever made" and think boobs?
"Quote me as saying I was mis-quoted." -Groucho Marx
No mere human will never be able to accomplish what God did with Jennifer Lopez's ass.
SJW: Someone who has run out of real oppression, and has to fake it.
Does anyone here want to inform CmdrTaco that boobs shouldn't be perfectly spherical, and in fact, it's preferable if they're not?
This guy's the limit!
No one will be able to claim that a game of pool, snooker or soccer was won because the ball wasn't round enough...
Summation 2
Doesn't gravity's effect imply that a perfectly round object could only exists in "gravity-free" (outer) space?
Of course, I'm no experimental physicist, but if I were to guess, I might suggest the fact that the binding energy (and thus the mass) might change with force-field fluctuations in the vicinity, but I think that problem should be solvable by defining the proper environment for measuring.
Does anyone know?
Is there a reason for it to be a sphere? Easier to determin the weight?
The picture in the article shows the sphere being handled in what obviously isn't a cleanroom. Won't that mess up its surface?
"I bless every day that I continue to live, for every day is pure profit."
These spheres look an awful lot like the ones featured in the ray-traced version of quake wars...
In a press release today, Sir Mix-A-Lot is quoted as saying that, by viewing this object, "You get sprung", as well as "[wanting to] pull up tough" because of the perfect shape of the object.
He was later quoted as saying that "I like'em round and big, And when I'm throwin a gig, I just can't help myself". Clearly, he is an aficionado for perfectly round objects.
* my captcha was "beating", which is what I deserve for the 90's reference.
In other news... these same scientists are hosting the BEST GAME OF PONG EVER this weekend!
"Insanity in individuals is something rare - but in groups, parties, nations and epochs, it is the rule."
Covered this before on slashdot.
http://science.slashdot.org/article.pl?sid=07/06/15/0541230
That article was amount this (they were planning). This article is about them actually completing the task. Almost a dupe, not quite. Random stuff I remember from the last discussing. The sphere works be calculating the amount of silicon atoms that would weigh one kilogram (I'm guessing the kilogram as defined by the Paris Standard), and then using the crystalline structure of silicon to find the exact dimensions of a sphere containing that amount of atoms, and then they would go and mill the perfect sphere. By defining it as a precise number of silicon atoms, people can in theory completely recreate the kilogram if every standard was destroyed. As it stands now, if we lost the Paris standards, all the scales in the world would lose precision, and a kilogram here would not be a kilogram there.
Mass scales have to have something physical to be calibrated against, so even if they defined kilogram as so and so many natural constants (Plank mass?), there would still have to be some sort of stable physical thing to calibrate the scales with (hence this badass sphere).
So the metric system, which is touted as being so much more accurate than the measurements we here in the U.S. know and love is has a measurement that is based on a disappearing lump of metal? The only logical conclusion one can draw from this disclosure is that the metric system is magic, and should be burned at the stake.
It sounds like a load of balls to me.
http://science.slashdot.org/article.pl?sid=07/09/13/2234236
http://science.slashdot.org/article.pl?sid=07/06/15/0541230
Government cannot make man richer, but it can make him poorer. - Ludwig von Mises
I guess silicone is the solution for everything that deforms. What? Oh, silicon...
Next up for them is creating 10 perfect (but miniature) bowling pins. This is all part of a misguided effort to bowl a perfect 300 game. Have to applaud the effort though.
Seriously, isn't this just a stopgap effort to mitigate some of the problems with the current standard? It sounds like the Watt balance technique mentioned in TFA is a much better idea. Hopefully the techniques used in the sphere effort can also be used elsewhere.
It should be possible to count exactly the number of atoms in one of the roughly 9cm silicon spheres to define the unit.
That has got to be the most tedious, boring job ever!
Pamela Andersen was not available for comment on the perfectly round silicon spheres.
So I'm not getting fatter, it's the kilogram that's getting slender!
Personally - I'm trying to get everyone to convert to decimal time. under decimal time: 1 day = 10 hours 1 hour = 100 minutes 1 minute = 100 seconds That means a day would have 100,000 seconds, making each second equal to about 0.86 of the currently defined second. This would make my life much easier, although my wife might be dissapointed that I'd only be good for a little over 1 minute.
"First we create a perfect sphere, then we count the number of atoms exactly - and we get a kilogram standard!"
"Alright... so how big do we make this sphere?"
"Oh you know.. roughly 9 cm, give or take."
Done.
I actually thought "Extremely high precision Inertial sensor", the kind that is put in space probes or satellites, since perfect spheres are required for the gyroscopes IIRC.
why not just define a kg as 1 Liter of pure H2O at 4deg C?....it is that way anyway.
Your balls may always rotate
Deiseil or widdershins
What matters is their smoothness
Reflects what's on your chins.
Burma Shave
Get thee glass eyes, and, like a scurvy politician, seem to see things thou dost not.--King Lear
Does this also pin down the value of pi? I mean, they know exactly how many silicon atoms are on the surface of the sphere, and they know exactly how many atoms there are from the center to the surface.
hmm.
It should be able to play the perfect Skiball game.
A kilogram is defined as exactly 2.20462262 pounds of pure water at pressure of 100 kPa (1 bar) and a temperature of 273.15 K. :)
The roundescht object in the world isch your mother, Trebek.
Colin Dean Go a year without DRM
You mean George Michael's butt. Look at it!
Well, it's sorta like this: a standard is only useful if you have some effective way to reproduce it or measure with it.
1. time. You can essentially just make a MASER, which means basically a cavity which resonates at that frequency. The nice part is that it can be tuned, and even continuously tuned, by just measuring the amplitude of the signal. When you've reached the maximum power, the thing is tuned to that frequency.
2. length. It's measured by Interferometry, so you have a meaningful way to transform a wavelength into any given distance.
At any rate, the transition for these two only happened when someone build a device which could actually measure one second or one metre that way.
3. mass. Well, that's the tricky one. Saying that you define a kilogram as one bazillion silicium atoms is useless unless you can somehow actually produce a lump with that many atoms. As long as we can't actually be sure how many atoms are in there, it would be a useless standard.
These guys claim to have been able to do just that: say with a high degree of confidence that, yep, their spheres contain exactly that many atoms. If they're right, then we're finally ready to move the kilo to that standard.
A polar bear is a cartesian bear after a coordinate transform.
I think that Gravity Probe B has the most perfect spheres and they are much smaller that the Kilogram sphere.
Kilogram Silicon Spheres
"If you were to blow up our spheres to the size of the Earth, you would see a small ripple in the smoothness of about 12 to 15 mm, and a variation of only 3 to 5 metres in the roundness"
Gravity Probe B Spheres
http://www.nasa.gov/mission_pages/gpb/index.html
"If these ping pong-sized balls of fused quartz and silicon were the size of the Earth, the elevation of the entire surface would vary by no more than 12 feet"
We are Dead Stars looking back Up at the Sky
Would you care to explain how a system that was in existence BEFORE the metric system was devised is "based on"it?
You and the post above yours seem to be confusing "is equivalent to" with "based on".
No mere human will never be able to accomplish what God did with scarlett johansson's ass.
"its mass is changing relative to copies held elsewhere"
I've heard this before but no-ones been able to explain it to me. What exactly is happening to the mass of the platinum spheres and why?
Sigger than your average
They should have visited this guy's website
http://www.kyokyo-u.ac.jp/youkyou/4/english4.htm?
making spherical mud balls. I've had this bookmarked in del.icio.us for a long time
"If you were to blow up our spheres to the size of the Earth, you would see a small ripple in the smoothness of about 12 to 15 mm, and a variation of only 3 to 5 metres in the roundness,"
Common only 5m accuracy??? Even GPS is better than that....
Still not as round as Karl Pilkington's head...
from TFA "To shape the spheres, the Australian Center for Precision Optics pulled optical engineer Achim Leistner out of retirement. Leistner, who has been creating precision spheres for decades, considers these final two to be his masterpieces"
Great. What happens when this guy kicks the bucket?
I'll see your hokum and raise you a boondoggle.
Is this really the reason why it's a sphere? Crystals don't PRECISELY grow into a sphere do they? Won't they still need to shave or polish it to get it to the exact radius? And then they'll need to calculate the number of atoms using Pi, an irrational number!
Why don't they make it a cube and find a length that is close enough (cubed) to give them the approx. right number of atoms and then make THAT the standard? They'll then have an EXACT number of atoms making up each length. It should be easier to cut or shave off the requisite number of atoms to maintain it, a (perfectly) flat surface seems much easier to maintain than a 3D curved surface. In fact if they make it just a little too small they could probably even ADD to the cube in single atomic layers using vapor deposition!
Obviously brighter minds than mine have thought this through more thoroughly, so really, I'm curious: why is it a sphere?
By the way, maybe this is a good use for the ISS, to keep the 1kg reference MASS somewhere it won't be distorted by gravity, not kept at any particular country for measurement and you can keep it in a high quality vacuum for free! (A little expensive to get to though).
Slashdot. News for the amnesiac. Stuff that mattered.
Main Entry:
equivalent Listen to the pronunciation of equivalent
"Pronunciation:
\-lnt\
Function:
adjective
Etymology:
Middle English, from Middle French or Late Latin; Middle French, from Late Latin aequivalent-, aequivalens, present participle of aequivalre to have equal power, from Latin aequi- + valre to be strong -- more at wield
Date:
15th century
1: equal in force, amount, or value; "
Next time, get a dictionary when you try to argue, that way you won't be wrong again.
I read that article before I posted, and all you did was demonstrate that I was right, they are equivalent. That a pound equals a certain amount of grams is intended to show what exactly? It always equaled some amount of grams, stating so has nothing to do with my question.
You did not answer my question, and you did not prove your point.
I thought in the relativity era mass was actually defined in electron volts - is this not the mass equivilent to definig time by Cs 133 oscillations?
Why does it have to be a sphere? I'd think a cube would be much easier to make (and measure)?
"Easy. At some point in time some people decided to base the US system on the metric system."
You said that already, restating it doesn't answer my question.
Comment removed based on user account deletion
"You can't take a pound and get an exact number of kilograms (especially from a legal perspective)."
Which has nothing to do with equivalent. More to point, equivalence doesn't rquire "an exact number" of anything.
Have a nice day.
...has created the most perfect spheres ever made...
...roughly 9cm...
That precise eh?
That is exactly what I was looking for.
Too many people think that defining equivalence is the same as basing the number on the kilo.
And it still has nothing to do with equivalent. Again, equivalence doesn't require "an exact number" of anything, I don't know why you think that applies at all.
Have a nice day.
If you were a theoretical physics student, you'd probably assume boobs were spheres.
Avogadros aren't even remotely spherical, more sort of pear shaped.
At the bottom of the
Depends. Actually, no "perfectly round" object (made of atoms) can exist anywhere, only an approximation, but I guess that you mean deformation, in which case my answer is: Depends, on the method of creation (including material and build process). But of course it would be nice to store the ball (in case gravity deformations are showing on a ball of silicone, maybe they're also negligible) on a space station/satellite without artificial gravity.
3M [formerly Minnesota Mining and Manufacturing] beat them to it, about 50 years ago. Scotchlite (TM) reflective material (featured in traffic signs, etc.) is made by spraying molten glass through nozzles into the top of a tall tank. The fine droplets of the spray (about 0.1mm) form spheres that harden as they fall.
Why make these standard unit samples out of matter at all? A single sample of matter is going to be irregular, and it's going to change over time. Why not make them all samples of energy, which is much more consistent in its state? E = mc^2 is a simple conversion for the matter equivalents, even if the equivalent matter is nanoscopic or smaller - we can also easily multiple by powers of 10.
As for "roundness", matter is even worse in that measure. "Round" and "straight" are idealized qualities that matter does not possess. Again, energy is much more consistent, as in its inverse square law that can be measured as "round" to a much higher precision than knobby, crude matter.
Why do we have a simple, metric and relativistic physics, if we can't refer to it as the basis of that physics?
--
make install -not war
For the specification they are trying to achieve, even a little chip from a corner would be a tremendous error. It's a lot tougher to damage a sphere that way. Of course you can damage both from dropping them.
I too think eventually this physical weight will be replaced by a known voltage/wattage on a scale to counteract a force, although for practicality purposes, having a physical object is probably much easier to use in daily situations.
..........FULL STOP.
There was a very nice article in American Scientist, which suggested that instead of defining this number of atoms, you could define the constant of Avogadro instead. Since this is linked to the gram via the weight of a carbon atom, this definition is equivalent. Since you are free to pick any number within the error bars of the current definition, they suggest to pick a nice number instead, just like the speed of light was defined as an integer. Their funny requirement was that it should be a perfect cube, since this would define one mole as a cube with an integer number of atoms on its side. This leaves essentially only one number: define N_A as the third power of 84.446.888!
karma police: arrest this man, he talks in maths; he buzzes like a fridge, he's like a detuned radio. [radiohead]
And I thought some gamer types were weird.
Why not some regular prismatic solid, whose flat surfaces would (I speculate) be easier to make? The dimensions would be measurable using interferometry just as with the spheres, ditto with X-ray for lattice parameters.
...is most definitely an absolute adjective... Come on, you make this most easiest.
The current standard kilogram is a cylinder with equal height and diameter, this minimizes the surface area / volume ratio (within the world of cylinders). The new standard takes this one step further by venturing outside of the universe of cylinders.
I never liked the metric system. Oh, sure it's all based on tens and is good for science, but I find the English system more practical.
There's no metric unit that's close to feet. Either you've got a lot of centimeters or parts of a meter.
And say I want to measure something. According to the standard a meter is the distance light travels in a vacuum during 1/299,792,458 of a second. How am I suppose to measure something with that? Put it in a vacuum and see how many seconds it takes light to get from one end to the other?
Coder's Stone: The programming language quick ref for iPad
... lochnar!
There's a shortage of perfect breasts in this world. It would be a pity to damage yours.
Just a small correction, the kilogram is defined by a platinum-*iridium* alloy artifact. The addition of iridium was important to guarantee the best possible stability
From the article:
The problem with defining the kilogram as the mass some arbitrary physical object is that all the measurement equipment in the world has to be calibrated and traceable to that object. If a non-physical standard could be developed, we could one day have extremely accurate balances that self-calibrate using that standard.
If all women had scientifically 'perfect' breasts then those perfect breasts would get pretty boring
Where has your penis gone? Breasts getting boring? What kind of silly, nonsensical, jibber-jabber is that?
Breasts NEVER get boring! I love my wife's breasts as much today as the day I married here!
Actually, come to think of it, it'd be pretty awesome for all women to have the same sized breasts. That's a whole level of insecurity that men wouldn't have to deal with any longer.
Give a man a fire and he'll be warm for a day. But light a man on fire and he'll be warm for the rest of his life.
Just define the KG in terms of pounds at 1 G. Do Americans have to solve all of France's problems for them?
I often don't like the choices people make, but I like the fact that people make choices. That's why I'm a conservative.
I don't know, 260 posts about silicon spheres and no one has mentioned Horta eggs. Kids these days, now get off my lawn.
it's = it is
its = belonging to it
I have two questions...
1. If these two spheres are touching each other, how many atoms from each sphere are "touching?"
2. At the touching edge, what is the difference to the touching atom, from the one side where it is "touching" to the other side which is part of its own sphere?
Well, that sure is one round sphere. Golly gee whiz, what an important milestone!
I immediately thought of the sculpture, paintings and drawing of Hindu goddesses.
They are totally stacked.
Does this mean I'm tolerant of other faiths, appreciative of classical art of other cultures...or just a perv?
I didn't think the house band in Hell would play this badly.
The answer is none.
None more round.
... DEEZ NUTS!
Sorry sorry sorry, I'll go write "I will not talk about my nuts" 500 times on the chalkboard now.
I think the reason why they made it a sphere is because a sphere is defined by one parameter only, its diameter. To make a perfect sphere all you need is to make sure it has exactly the same curvature everywhere. Now, let's see what it takes to make a perfect cube:
1) each of its six faces must be perfectly plane
2) each of its twelve edges must have exactly the same length
3) each of its twelve angles must be exactly ninety degrees
Just to illustrate how difficult this is, I once read this anecdote about Wernher von Braun: when going through his mechanical engineering course in Germany, one of the professors gave each student an irregular lump of iron. The assignment would be to create a cube, as perfect as possible, from that lump. The size of the resulting cube didn't matter but, naturally, if it was a very small cube it meant the student had a tough job getting it right.
It's 1024 grams, right? Easy definition.
Will it blend ?
why should it be perfect 'sphere'? how about 1L of water in a atom perfect 10cm x 10cm x 10cm inside of the box? minus the weight of the box? and in a perfect laser cut controlled temperature and pressure? and without any vibration around it? or have the box enclosed?
According to the video, they started out by milling two silicon hemispheres. How did they bond them together?
Happiness is like peeing yourself. Everybody can see it but only you can feel its warmth.
Platinum was originally used because it was thought to be totally unreactive in air. That turns out not to be the case over several decades.
Silicon will react with air almost instantly. There's already a layer of oxygen and water contamination on those things, which will vary with temperature, humidity and time. I remember reading somewhere that they had accounted for this, but I don't remember if it just turns out to be a fudge factor, below the current measurement error or what. It seems to me that relating mass to some easily defined electromagnetic force would be better in the long run.
They used to do this with the meter as well. There was a stick that was the definition of a meter. They then changed that definition after they found exactly what the speed of light was. Basically, it was 299,792,458.xxxxxx meters per second. I have no idea what the decimal was, but it doesn't matter anymore, because they redefined the meter as the distance light travels in a vacuum in 1/299792458ths of a second. Didn't change it much, but gave it an unwavering standard. You can use the meter and water to define a kilogram exactly, since another definition of the kilogram is the amount of water at STP (Standard Temperature and Pressure) that fills 1000 cubic centimeters. Reproducable anywhere without using the 'original' weight for measurement. Only real benefit of using a solid is that you can place it in a vacuum to eliminate any buoyancy caused by air. Still cool that they made such finely machined spheres.
This is a serious question, not trolling.
I was wondering why you worked so hard to make a sphere when maybe a cube would be easier? (if it's not forgive me for being dumb, but I don't remember being told making a cube was harder than a sphere)
As a rock-in-roll Physicist once said, No matter where you go, there you are.
You'd think a cube would be able to be fashioned more accurately than a sphere. I guess the atoms must fall off the edges or something that make it unsuitable.
"It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
Than the spheres in the gyros of the GP-B?
The Extraordinary Technologies of GP-B
(NSFW)
http://images.fok.nl/upload/050701_30560_howtodrawboobsfok.jpg
Just a wild question..
Assuming the LHC successfully detects the Higgs boson and improves our understanding of the Higgs filed's mass bestowing properties, could that lead to a fundamental definition of the kilogram?
(Eg the weight 'exchanged' by each of a pair of Hogsheads of Higgs ??)
This idea that the mass of supposedly identical objects is changing for no known reason sounds like a fascinating puzzle to be explored. Unfortunately the article seems more interested in ways to work around the problem rather than understanding it.
"It's the height of ridiculousness to say for those 9 lines you get hundreds of millions."
I am a physicist at the UK's National Physical Laboratory and I am involved in the redefinition of another unit - the unit of temperature. The work concerning the redefinition of the kilogram is >much more philosophically fraught and technically difficult. I understand many of the rather skeptical comments expressed here The current situation is unsatisfactory because the mass of the kilogram is changing, albeit by a small amount - a few micrograms in 1 kg - i.e. a few parts in 10^9. The aim of the work is to replace this artefact with (essentially) a procedure. Effort onne (using the silicon sphere) is essentially trying to build a link between a macroscopic mass, and the microscopic masses which we expect to be fixed. The other effort not mentioned here is called the watt balance which is a machine which can exhibit the same inertial mass as a kilogram - or any other weight. At the moment the two watt balances disagree with each other and they both disagree with the silicon sphere result. There is still a lot of work to do on both approaches. Incidentally, the reason is it is a sphere rather than a cube is because of edges. Edges are amazingly fragile, hence the sphere. ALl the best M
Yet another artifact of the french revolution (circa 1793) but it didn't catch on then...
Personally, I think that this would be great. Since in the Republican calendar scheme, each 30-day month got divided into 3 10-day weeks in this scheme, 40 hour/weeks would be a breeze... If you got paid monthly, the 5 (or 6) day "leap" month every year would be a pretty good bonus too.
They want to have the standards bureau to define the kilogram this way. This is is only one possible redefinition. From what I have read, there is another strong contender which is based on electromagnetic force.
The new paper proposes that the next General Conference on Weights and Measures adopt either one of two definitions for the kilogram to effectively fix its value by selecting a specific value for either the Planck constant or the Avogadro constant. Two types of experiments are leading the effort to realize either of these definitions. The first one measures a kilogram against the amount of magnetic force required to balance a 1-kilogram mass against the pull of Earth's gravity. The experimental apparatus used to make the measurement is called a watt balance. A kilogram mass is placed on a balance plate that is surrounded by a coil of copper wire, which in turn is surrounded by a coil of superconducting wire. Magnetic fields produced by sending electricity through the coils push on the balance plate to offset the artifact's weight. The amount of electric current and its voltage then is used in defining a kilogram. Electrical power can be related to the Planck constant, defined as the ratio between the frequency of an electromagnetic particle such as a photon of light and its energy. This experimental method of defining the kilogram relies on selecting a fixed value for the Planck constant, which is currently determined experimentally based on the fixed value of the kilogram artifact.
This comes from here. Here is another article that talks about the same thing. TFA also links to an article that talks of this (I assume), but that article requires a subscription.
These articles also talk about why it is good to redefine the standard -- basically, by doing so, a bunch of other measurements/definitions immediately have less uncertainty.
Yo mommas ass !
Just a shot in the dark, but... if you have a sphere, you'd have one contact point with the surface used to measure? Whereas a cube would be a large flat surface... if they are getting this exact tollerance then they may not want friction playing a role in it. Besides, I think they can spin the silicon sphere to be almost completely not touching a surface. (Air streams in a round chamber) that would effectively levitate it while measureing (xray I guess from article) the # of atoms, etc...
But just a guess, so I may be WAY off base. Seriously for once....
BTW, in 2005, Gravity Probe-B project, created the perfect sphere:
http://einstein.stanford.edu/
Don't know who actually wins, I'm looking for #'s now...
--- Relax, that mass muderer is just trying to reduce our carbon footprint, one fetus at a time...
Edges wear off. And what kind of edge do you want? Sharp? Rounded?
A sphere avoids the whole problem.
Insert
...would it be a molecule? There's got to be _something_ holding it together...
Of course the more important question is: if it is, can they use the same technology to build spaceship hulls?
Aren't black holes the most perfectly round objects in the world ? (much more than any man-crafted artifacts)
My logic is that it would be far easier to make a ONE GRAM sphere, then multiply the results by 1000.
What am I missing here? Harder to detect flaws?
And ANOTHER thing.
Why are they not just using a computer simulation, considering the weight of ONE silicon-28 atom is known? Mathematically construct one, then, if capable of producing a PERFECT sphere(which apparently, they are not), spend the million bucks.
Just seems, to me, like they are putting the cart in front of the donkey.
I thought a kilogram was 1000 grams. A gram, I learned, was the mass of one cubic centimetre of water at sea level which has a volume of one mL.
Is this not accurate?/p?
I thought according to quantum mechanics the position (and hence the number) of atoms can't be determined due to the Heisenberg uncertainty principle.
"Size matters not. Look at me. Judge me by my size, do you?" --Yoda {whips out green light saber}
I mean, americans are always getting fatter, right?
If you quote this signature there'll be 72 copies of Windows ME waiting for you in Heaven.
The Kg of platinum was no doubt the nerdy show-off in its day that the silicon boobs, i mean perfectly round spheres of silicon, are today. Of what possible consequence can the substance or shape of the mass matter?
Unless you just want to show-off. BTW a kilogram is just that, 1,000 grams. But I guess a 1gram sphere of silicon wouldn't be a boob, it'd be a testicle. And what nerd wants to show off his testicals?
Slashdot never fails to amaze me at the amazingly strange leaps of discussion that occur...
An Australian mining company, no less: http://www.eromangauranium.com/
Sounds like they could have been from Uranus, too..
Or are you such a nerd that you actually prefer Silicon boobs?
I thought the gram was defined as the mass of 1 cubic centimeter of water. Not the case?
I've built up so much character I have an alter-ego
It's easy to remember.
Whoever got the kilos got the candy, man.
Remember that scientists are naturally skeptical. To claim something is exactly 1KG takes balls.
This story broke last year and has already been discussed here.
Sure, there has to be a finite number of atoms in any given object, but doesn't the Heisenberg principle mean that ultimately you won't be able to count the atoms because you would be interfering with the energy state by doing so, thus making their location indeterminate. If you can't find them, then you can't count them.
"Charlie, here, I want you to take this perfect sphere and count the number of atoms in it. Better do it twice just to be accurate. Here's a pencil and paper and a magnifying glass. Have it on my desk tomorrow morning."