World’s Roundest Object!


Can I hold it? Only if you promise to be really, really careful. I promise I will be so incredibly careful.
I will be incredibly careful with it. I promise. So, it’s slippery, be careful.
Alright, are we ready? I’m about to touch a 1kg sphere of silicon-28
atoms. There are about 2.15×10^25 of them. It feels absolutely incredible. Wow, that
is amazing. Besides its creators, I am one of only a handful
of people ever to hold this sphere. The raw material used to make it was worth
1 million Euros but now that it has been so precisely sculpted — How much is that worth? It’s priceless. … This you are looking at
now is the roundest object in the world. How can you say for sure it’s the roundest
object? I mean the Earth is pretty round, isn’t it?
If this was the Earth… If this were the Earth then the highest mountain
to the lowest valley would be… about 14m apart. That is shocking. That is shockingly round. But why would you invest one million Euros
and thousands of man-hours perfecting a pure, polished silicon sphere? Well the answer is grave. Or rather ‘grave’
as it would have been pronounced in the original French. You see the grave was the original name for
the base unit of mass in the metric system, which became the Systeme International d’unites
or SI units. In 1793, a commision which included notable scientist and aristocrat Antoine Lavoisier,
defined the base unit of mass as the weight of a cubic decimeter of water at the melting
temperature of ice — essentially just a litre of ice water. The name grave came from the
Latin gravitas, meaning weight. But it wasn’t to last. It sounded too similar
to the aristocratic title ‘graf’ — which is the equivalent of an earl or a count. And
with the French revolution in full swing with the rallying cry of equality for all, you
couldn’t exactly have one unit nobler than the others. At this Lavoisier lost his head,
literally, not because he helped devise one of the greatest systems of measurement of
all time, but because he was collecting taxes as a nobleman. So things really were grave. The new republican government believed a grave
would be too big for the things they wanted to measure anyway and and so they settled
on the gramme, which was just a thousandth of the grave. But soon they realized that a gram was too
small and so they returned to the grave, but since they couldn’t call it that, they invented
the kilogram — a thousand grams. And that is why out of the seven base SI units, the
kilogram is the only one to have a prefix in its name. In 1799 the kilogram definition was refined
to be the mass of a litre of water at 4 degrees Celcius — the temperature at which it is
densest. But water itself is obviously not the most sensible thing to use as a mass standard.
So a pure platinum cylinder was created to have the same mass as the water definition
and it was declared Kilogram of the Archives. Now it’s important to note at this point the
kilogram is no longer tied to the mass of a volume of water — the kilogram of the archives
is by definition THE kilogram. 90 years later, in 1889 the kilogram was upgraded
to a platinum-iridium alloy cylinder. Now it was much harder than the original but was
otherwise basically identical. And to this day, it remains the definition of the kilogram.
It is officially called the International Prototype Kilogram, though it’s affectionately
known as Le Grand K — or Big K. Oh, and it’s about this big… It is the only thing in the entire universe
with a mass of exactly one kilogram because it IS the kilogram. It is also the only SI
unit that is still defined by a physical object. It sits under three bell jars, next to six
sister kilograms, in a climate-controlled vault locked by three independently controlled
keys, in the basement of the International Bureau of Weights and Measures on the outskirts
of Paris. Now if you were able to break into the vault
and tamper with Big K, you would be changing the definition of the kilogram, a definition
on which many of our measurements rely, and so you would throw the world into chaos! Well
no, not actually– but how would anyone ever know if the mass of Big K changed? Well when it was first created, 40 identical
replicas were also made. Well they weren’t quite identical – they had a mass which was
slightly different to Big K but those offsets were recorded. Now these replicas were sent
out to countries around the world to serve as their national standards. In 1948 the kilograms were reunited for a
weigh-in. And this is when the problems started. Because even though all the cylinders were
made of the same alloy and stored under virtually the same conditions, their masses had diverged
over time. The mass of Big K wasn’t even the same as the six sister cylinders stored with
it. And to make matters worse when they were brought together again forty years later,
their masses had further diverged, up to about 50 micrograms – that’s about the weight of
a fingerprint. But fingerprints were not the culprits since the kilograms were carefully
washed before their weigh-ins. So some physical process must have actually
changed the mass of the cylinders, but how that exactly works remains a matter of speculation.
One this is for certain, the mass of a platinum-iridium cylinder is not stable over time. And this
is a big problem. You can’t have a unit which changes its value.
And the fallout isn’t limited to measurements of mass since of the seven base SI units,
four of them depend on the mass of the kilogram, not to mention all the derived units like
Newtons, Joules, Volts and Watts. At this point those of you in countries that
have not adopted the metric system–yes I’m speaking to you Liberia, Burma, and the US–you
may be feeling rather smug that your unit of mass, the avoirdupois pound, is no longer
defined by a physical object. No, instead it is defined as precisely 0.45359237 kilograms. Sucked in. So clearly something needs to be done to eliminate
the kilogram’s dependence on a physical object and this is where the silicon sphere comes
in, but how exactly does that help? Here you have a physical object and it’s beautiful
but you know it’s still a physical object. You’re trying to get away from that.
We’re trying to get away from the physical object but what we’re doing with this particular
object is counting how many atoms are in there. You can’t actually count how many are in there
can you? You can’t count how many are in there but
you can calculate how many are in there because this material is silicon, there’s no voids
or dislocations. So this is like a perfect crystal of silicon.
That’s right. Not only is it pure silicon, it contains only
one isotope of silicon, silicon-28, and that explains why the original material was so
expensive. And why a sphere?
Well, a sphere is a pretty simple object. If you know the diameter of the sphere you
can characterise the entire dimension of the object.
Well that explains why the sphere has to be the roundest object ever created, but how
do you actually make something that round? We actually start with an oversized sphere.
So it was about two millimetres larger in diameter and then we just grind it progressively
finer and finer using abrasive. It’s actually massaging atoms. You’re down at that level
of trying to control the shape of an object down at the atomic level.
But making the sphere is only half the battle, then you need to accurately measure its diameter.
The diameter is actually measured via a laser. So you’re actually measuring having the sphere
in the centre of a cavity and a laser is hitting both sides and you’re actually measuring the
gap. By knowing the diameter you can determine
its volume. And since the atom spacing in silicon is known to high precision, you can
the calculate how many atoms make up the sphere. This allows you to redefine Avogadro’s constant.
At the moment, Avogadro’s constant is defined based on the kilogram. It is equal to the
number of atoms in twelve grams of carbon 12. But using this approach, the number of
silicon atoms in the sphere would be used to fix Avogadro’s constant, which would then
define the kilogram. So even if the silicon spheres were lost or
damaged, it would have no effect on the definition of the kilogram because it would be defined
not by a physical object but by a concept. You would like to see the official definition
of the kilogram say “a kilogram is the mass of 2.15×10^25 silicon-28 atoms”
Yes. Is it – is it going to happen?
There’s a likelihood, a high likelihood that it’s going to happen.
But there is another approach to redefining the kilogram which involves fixing Planck’s
constant and it’s done using something called a Watt Balance. These two approaches are complimentary.
Each one provides a check on the other, and if they show good agreement and are able to
bring their uncertainties down to about twenty micrograms they may redefine the kilogram
as early as 2014. And then the kilogram finally will be an unchanging unit, no longer defined
by a physical object in the basement vault of some place in Paris.
Now if the kilogram was originally intended to be the mass of a litre of water at its
densest temperature then how well did we do? Well if you look at a litre of water at nearly
four degrees Celcius it has a mass of 999.975 grams. So I guess you could look at this two
ways. On the one hand you could say the kilogram is slightly heavier than it should be, but
on the other hand 214 years ago, scientists were able to create an artifact that was correct
within the margin of error of a grain of rice. Now that is truly remarkable. Now if you want
to hear more about the Watt Balance, let me know in the comments and I will see what I
can do. It does seem to be the frontrunner in terms of redefining the kilogram, so we
will have to wait and see what happens. One last thing, I should point out that it took
an international collaboration of scientists to create the silicon sphere but don’t you
think that the scientist who originally conceived of silicon as an element should receive some
of the credit. Well in 1787, that was none other than Antoine Lavoisier. So he’s been
involved in the definition of a kilogram from start to finish or from cradle to grave.

100 thoughts on “World’s Roundest Object!

  1. This is the sort of nonsense that goes on in the EU. A cylinder of this material would be easier and cheaper to produce.

  2. Sometimes when hes explaining stuff he sounds like hes trying to imitate a British and an Australian accent at the same time.

  3. Feeling pretty smug with Liberia, Berma & the US @ 6:52..
    Until: Zero point four five three five nine two three seven…. Kilograms 😂 😂 😂

  4. It looks like the ball is not moving at all and his hand is just spinning round it and the ball is completely still

  5. Please, just one question. What is the raw material called? That is used for this sphere, that makes it worth 1 million euro, just as a raw material. The lady scientist, saying that the sphere is priceless. That i can understand since it is one of a kind. But still, could someone just tell me the NAME of the material, without geting all scientific in the answer. Thanks, uppfront.

  6. If human civilization allows us to literally create a sphere correct to the atom, I wonder if this kind of video would ever exist anymore #_#

  7. The weights and measures sphere is made in a centraphuge that is used to make 95% subcritical enriched weapons grade uranium, the core of nuclear bombs of which there are approximately 14,000 bombs and 30,000 cores in existence, many of which have degraded and are in permanent disposal storage or have been melted down and reprocessed for various purposes.

    There are around 30,000 of these spheres in existence, only 100 or so are not radioactive.

  8. No no no, what you should do is make the object way smaller, Then count it's atoms and simply multiply it by a million, or what ever adds up to the right weight, That way you can be sure and just keep the tiny samples that all have the same number of atoms and then weigh in again in a decade to see if the number of atoms have changed

  9. I just noticed that the video was made in 2013. The new defintion of Kilogram came into force only on 20 May 2019. Now, we don't need that sphere to define a kilo.

  10. Very interesting, chapeau! What I didn´t get is: what for is the physical sphere needed, when you yust calculate the number of atoms?! This could be done without forging that thing, and then never need it again? spooky …

  11. Hey can you do a video about straight objects? I always wondered how they got the first straight object, every current straight object is made from another straight object. For example you use a ruler to draw a straight line, the ruler is cut on a saw which was made by a mill which was made by another mill, how did they make the first straight line to make the saw that made the mill that made the tool to make the ruler?

  12. No…The longest running problem in measurement is gravity differential. Earth's gravity is not completely constant from one location to the next… And thus you will have errors regardless of how you define the kilogram.

  13. So if I touch a piece of paper everyday…

    One day it will be as big as an elephant since fingerprints has weight…

  14. I dont believe you , time space is in constant movement , simply moon orbiting earth change its gravitational pull so it change mass of the sphere or the "the kilo" even on earth there are places with higher and lower gravity , to be funnier the kilo moves all the time , the earth orbit sun , solar system moves in the milkyway galaxy and the galaxy moves in the universe , simply transporting the kilo from place to place changes its weight slightly not to mention that touching changes its weight…

  15. THE ABSOLUTE, CLEAR, SIMPLE, AND IRREFUTABLE MATHEMATICAL PROOF THAT ELECTROMAGNETISM/ENERGY IS GRAVITY:

    OVERLAY what is THE EYE in BALANCED RELATION to/WITH what is THE EARTH. THE EYE is representing the DOMED, semi-spherical, translucent, QUANTUM GRAVITATIONAL, AND BLUE SKY as what is a TRULY BALANCED and equivalent electromagnetic/gravitational form, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. ALL of SPACE is NECESSARILY electromagnetic/gravitational IN BALANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. THE EARTH is ALSO BLUE, AND THE DOME of a person's EYE is ALSO VISIBLE (as WATER). LOOK down at what is the fully visible EARTH/GROUND. The BALANCE of being AND EXPERIENCE is ESSENTIAL. BODILY/VISUAL EXPERIENCE is invisible AND VISIBLE IN BALANCE, AS ALL of SPACE is NECESSARILY electromagnetic/gravitational (IN BALANCE); AS ELECTROMAGNETISM/ENERGY IS GRAVITY. This NECESSARILY represents, INVOLVES, AND DESCRIBES what is possible/potential AND actual IN BALANCE. E=mc2 is DIRECTLY AND FUNDAMENTALLY DERIVED FROM F=ma, AS ALL of SPACE is NECESSARILY electromagnetic/gravitational IN BALANCE; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. THOUGHTS ARE INVISIBLE. THINK !!! INSTANTANEITY is, in fact, FUNDAMENTAL to the full, BALANCED, and proper UNDERSTANDING of what is physics/physical experience.

    GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. The stars AND PLANETS are POINTS in the night sky. A PHOTON may be placed at the center of THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the SPEED OF LIGHT; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE. F=ma AND E=mc2 prove that ALL of SPACE is NECESSARILY electromagnetic/gravitational (IN BALANCE), AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. "Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent with/AS what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT !!!

    There is no outsmarting the GENIUS of dreams. Dream experience is/involves true/real QUANTUM GRAVITY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Dream experience is always that of the BALANCED MIDDLE DISTANCE in/of SPACE. Dream experience GROWS/INCREASES. MOST IMPORTANTLY, in dreams, BODILY/VISUAL EXPERIENCE is invisible AND VISIBLE IN BALANCE. BALANCE AND completeness go hand in hand. Gravity IS ELECTROMAGNETISM/ENERGY. Dream experience is possible/potential AND actual IN BALANCE. Dreams make thought MORE LIKE sensory experience in general, thereby improving upon memory AND UNDERSTANDING. The ability of THOUGHT to DESCRIBE OR RECONFIGURE sensory experience is ULTIMATELY dependent upon the extent to which THOUGHT IS SIMILAR TO sensory experience. THOUGHTS ARE INVISIBLE. Dreams combine, BALANCE, and include opposites. THE EYE IS THE BODY. THINK !!!

    Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black.

    By Frank DiMeglio

  16. U know it’s really round when u turn the ball but it looks like the ball is staying put and you fingers r moving round it 0:34

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