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JAUNTY MUSIC PLAYS

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This is the story of an artefact.

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No-one knows quite how many
artefacts have been created

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in the history of mankind,

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but needless to say that there
have been a great many of them.

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From little Tommy Price's favourite
catapult,

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and Mrs Mirandes' decisively
demonstrative damask doily...

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..to young Pepina Peshlakai's
perfect pre-teen pin-up.

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Each is an ideal version
and definitive example

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of something truly important
to its creator.

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An object against which all
others can be measured.

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However, there are only a handful
of artefacts that have been used

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as references by everyone,

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standards so essential that their
very existence

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underpins the functioning of our
world.

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Some were used to define
lengths or volume or time.

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Most have come and gone.

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But the one that defines what things
weigh - their mass - still remains.

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Secured in an underground vault,

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locked by three separate keys,

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hidden from view -

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an unchanging constant in an
ever-changing world...

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..until now.

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History is about to be made.

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Representatives of over 100 nations,

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from Indonesia to Egypt,

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are here to solve a crisis.

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They put in millions
of hours of effort

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accomplishing engineering feats more
complex than the moon landing.

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These humble men and women aren't
business leaders or politicians,

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but their actions here will
fundamentally change every aspect

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of our lives,
from economics to medicine.

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Today, they will literally redefine
the world as we know it.

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We're trying to get rid
of a kilogram.

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But to understand
what the kilogram actually is

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and why they're so keen to get rid
of it,

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we should start this
story at the beginning.

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LAUGHTER

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From the moment of our conception,

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through every aspect of our lives,

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from the inconsequential,

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to the life-determining,

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the high points...

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..and the low,

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right up to the very end...

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BEEP

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..everything about our existence
is weighed and measured.

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We're a species obsessed
with quantifying things,

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because objective measurements
ensure everyone is dealt

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a fair hand in life.

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But that's a lot easier
said than done.

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Luckily for us,

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there are hundreds of people

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in different countries

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spread out across the globe

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working out the best ways to weigh
and measure everything.

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They are normal people with hopes,
dreams, hobbies and desires,

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just like you and me,

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but with one
minor difference.

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These men and women are the tellers
of time,

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the masters of mass,

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the safeguarders of standards.

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They are metrologists.

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Metrology is really very,
very important

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for industry and the society.

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If there were no metrologists,
we would have no measurement system.

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And we do crazy stuff.

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We measure glossiness of cats.

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CAT MEOWS

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We measure the acoustical
crunches of biscuits.

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We measure the fastest speed...

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WHOOSHING AND TICKING

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CLICK

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..and we measure the smallest
distance...

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..and we measure the largest volume.

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Metrology is the science
or the art of measurement.

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It means measuring things as in
normal life,

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but pushing this measurement
to the limits of technology.

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For centuries, metrologists
have been working away

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around the clock to ensure
that there are, in fact,

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accurate clocks to work around.

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And consistent rules to measure
with.

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And equitable masses to weigh.

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I think our motto should be,

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"We worry about it
so you don't have to."

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But there is a problem that
metrologists are worried about.

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The weight of everything
on the planet has been changing.

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The change is so small
few would even notice -

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less than the weight of a grain
of sand -

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but they have.

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No-one really knows why it was
happening.

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So that means no-one can stop
it, really.

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That's alarming.

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It doesn't sound important
but with pharmaceuticals,

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that could be the difference
between helping someone

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or hurting them.

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So, now it's up to the world's
finest pathologists

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to shoulder the heavy burden.

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Together, they need to redefine the
weight of the world,

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fix it for all time.

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But time...

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..is not on their side.

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The clock is ticking.

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In just over a year, hundreds of
delegates from around the world

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will travel to the General
Conference On Weights and Measures

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in Versailles, expecting a solution
to this weighty problem.

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It's not enough to work
day and night.

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It's a scramble, it will be tight
for us hitting the deadline.

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To succeed, they need to complete
one of the most difficult

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experiments in the world,

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ranked second only to the search
for the infamous God particle.

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I think it's fair to say that the
number of people that are involved,

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it's ridiculously
hard and it's really great work

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over many, many years.

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But to solve this problem,

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they'll need to shift the foundation
of our entire measurement system.

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To understand why requires
a trip back to Paris.

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More specifically, to an
intergovernmental organisation

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known as BIPM,

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or the International Bureau
of Weights and Measures.

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BIPM, we are one of the oldest
technical international

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organisations in the world.

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We're here in France,
but we're not French.

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It's led by director
Martin Milton,

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assisted by a team of staff,

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including Dr Estefania de Mirandes

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and Dr Richard Davis.

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The BIPM uses its impartial status
to act as an international guardian

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of metrology, ensuring measurements
are consistent,

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accurate and fair for all.

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And they are the curators of a truly
extraordinary achievement

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of mankind.

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A list - or, rather, a system
of definitions.

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Le Systeme International.
Or the SI for short.

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It's a simple list, distilling
all the essential properties

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of our world into just seven
definitions of base standard units.

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It's because we share this system
of units that it gets its power.

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It means we can compare things
in all the countries on Earth

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easily, transparently.

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The metre,

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the second,

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the mole.

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These are the essential standards
to which all our rulers,

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clocks, thermometers and scales
can be calibrated.

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That provides the basis
for all the types of measurement

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that one needs for science
and society and for quality of life.

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I love the SI. I really love it.

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And the reason I love it is

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because it has humanity stamped
all over it.

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Do you know how many languages
are spoken on our planet?

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Do we have a feeling of that?

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Huh?
300. 300?

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No, 3,000.

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3,000 different languages.

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And it is very complicated for one
group of people

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to communicate with
another group of people.

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And so, to have a universal
language in measurement,

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that's a...that's a global story

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and that's very, very beautiful.

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But there is a problem
with the SI.

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One hidden in plain sight.

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The kilogram,

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a fundamental unit of the SI,
is simply defined as...

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"The mass of a kilogram is equal to

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"the mass of the international
prototype of the kilogram."

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Mass is still tied to a single...

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..a single artefact in the world...

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..to a hunk of metal in Paris.

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The International Prototype
of the Kilogram,

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or IPIK,

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Le Grand K,

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The Last Artefact.

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The hunk of metal has many names,

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yet it is utterly unique and
absolutely irreplaceable.

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It's an object that literally
defines the weight of everything

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else in the world.

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Few ever get the chance to see
something this priceless.

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Except on a day like today.

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CHATTERING

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A small platinum iridium cylinder,

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standing only 39 millimetres tall,

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it's not a particularly
impressive object to look at.

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You have all these bell
jars which surround it.

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So you see this little, little thing
just in a safe.

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From one side you are excited,

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and on the other side,
it's just a piece of metal.

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I mean, it's a strange thing.

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How do you get excited about a small
piece of metal in that way?

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But it's what it stands for.

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Anything that you weigh,

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from an apple in a grocery store
to drugs at a pharmacy,

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eventually goes back to this
prototype in Paris,

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and it's an elaborate system

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of traceability that we have to that

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that enables us to get accurate
weights for everything that we use

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and buy and sell in the world.

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Held in vaults across the world

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are hundreds of copies of the
kilogram.

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None are exactly identical,

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but all are calibrated
precisely against the original.

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So, for example, if you stand
on a scale,

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it will give you a weight

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and you need to know if that weight
is the right weight.

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So, that scale has been calibrated
against another scale,

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which in turn has been calibrated
against another scale,

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and it runs all the way back.

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And the top scales will be
calibrated against the kilogram.

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And that kilogram, in turn,
is calibrated and measured

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against the IPK
kept in BIPM...

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..which is THE kilogram,

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which is the standard that all
standards are compared to.

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And this is the source of our
weight-related problems.

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This is what the kilogram -
THE kilogram,

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the International Prototype
of the Kilogram - looks like.

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Now, I'm handling it with my hands.

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By definition, the mass of the
International Prototype Kilogram

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is the definition of the kilogram.

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That means if you put a fingerprint
on it, it's still a kilogram

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and everything else in the universe
has less mass.

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That's a...

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That's a ridiculous
situation to be in.

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That's not the only issue.

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It's a man-made object -
so, an artefact.

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Everything that humans make,
as a standard, decays.

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Everything, as soon as it's made,
it's beginning to decay

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and change and evolve.

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Everything is decaying.

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Since it was forged, the IPK
and its replicas have deviated

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from one another by about
50 micrograms,

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or the mass of a single
eyelash,

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shifting the world's weight
with them.

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We do not know whether
the prototype, the artefact,

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is losing its weight or it's
accumulating its weight.

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There's a fundamental problem with
having an artefact that defines

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the standard against which
everything else

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in the world is compared.

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You want it to be isolated and kept
separate,

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but as the source of all the
weighings in the world,

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you want it to be used practically.

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In order to solve the problem
of the world's shifting weight,

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there is only one solution.

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So, we're dumping the lump.
We're changing the system.

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But that's not as easy as it sounds.

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The kilogram is a fundamental,
interlinked part of the SI units,

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which means to redefine it,

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you have to redefine the SI.

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You have to change the way the world
measures almost everything.

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I always feel like if humanity
is going to change something...

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..go big.

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To understand how we got into this
situation in the first place,

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and how we can fix it,

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we should really start this
story at the beginning.

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LAUGHTER

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No,
the beginning of civilisation.

255
00:18:01,400 --> 00:18:04,720
Measuring is a really simple idea,

256
00:18:04,720 --> 00:18:08,200
and humans have been doing
it since time immemorial.

257
00:18:17,160 --> 00:18:20,480
If we go back to antiquity,
thousands of years ago,

258
00:18:20,480 --> 00:18:25,040
people measured things with stones
and grains to make standards.

259
00:18:27,920 --> 00:18:33,000
These consistent measuring
references revolutionised fair trade

260
00:18:33,000 --> 00:18:36,440
and, naturally, people gravitated
toward standards

261
00:18:36,440 --> 00:18:40,240
everyone can access,
that were also close at hand,

262
00:18:40,240 --> 00:18:44,200
like a hand or an eye.

263
00:18:44,200 --> 00:18:47,200
Or arm.

264
00:18:47,200 --> 00:18:49,880
But these seemingly democratic
standards

265
00:18:49,880 --> 00:18:52,920
have their own potential for
short-changing.

266
00:18:52,920 --> 00:18:56,400
If you measure a horse,
you can measure in hands.

267
00:18:56,400 --> 00:18:58,800
If you measure a horse
and I measure a horse,

268
00:18:58,800 --> 00:19:01,520
we're going to get
a different size horse.

269
00:19:01,520 --> 00:19:03,040
HORSE NEIGHS

270
00:19:04,400 --> 00:19:07,880
So, many ancient rulers
created empire-wide,

271
00:19:07,880 --> 00:19:10,280
stable standards of measures.

272
00:19:11,440 --> 00:19:14,040
So, for example, in ancient Egypt,

273
00:19:14,040 --> 00:19:16,280
the cubit
was the length of measure,

274
00:19:16,280 --> 00:19:19,440
and that was the distance
between the elbow and the tip,

275
00:19:19,440 --> 00:19:21,760
or sometimes between the elbow
and the tip of the finger,

276
00:19:21,760 --> 00:19:23,600
plus a hand.

277
00:19:23,600 --> 00:19:26,640
But those guys realised this wasn't
going to let them build

278
00:19:26,640 --> 00:19:30,400
the pyramids to the kind of accuracy
that they needed to do,

279
00:19:30,400 --> 00:19:32,720
so they made a standard.

280
00:19:32,720 --> 00:19:36,400
Standardised artefact measures,
like cubits,

281
00:19:36,400 --> 00:19:42,920
allowed those in power to better
build, govern and tax their empires.

282
00:19:42,920 --> 00:19:47,160
Where you can compare something
measured in one place with something

283
00:19:47,160 --> 00:19:50,040
measured at another time,
in another place,

284
00:19:50,040 --> 00:19:54,960
and then measurement becomes
really, really powerful.

285
00:19:54,960 --> 00:19:59,560
But over centuries, these
measurement standards multiplied

286
00:19:59,560 --> 00:20:01,720
and massively muddled metrology

287
00:20:01,720 --> 00:20:05,440
through the creation of more
and more units.

288
00:20:05,440 --> 00:20:07,840
Pounds, ounces...
Pile, Charlemagne...

289
00:20:07,840 --> 00:20:09,080
A yard...

290
00:20:09,080 --> 00:20:10,520
Avoirdupois.
Shaku.

291
00:20:10,520 --> 00:20:12,080
Pint. Ls.

292
00:20:12,080 --> 00:20:13,200
Miles. Feet.

293
00:20:13,200 --> 00:20:15,520
Cun.
A shekel. The inch.

294
00:20:15,520 --> 00:20:19,400
By the 18th century,
the list was so long

295
00:20:19,400 --> 00:20:23,760
that some traders were dealing with
800 different units of measurement

296
00:20:23,760 --> 00:20:27,120
and a quarter of a million
definitions for them,

297
00:20:27,120 --> 00:20:30,000
many of which weren't comparable.

298
00:20:32,840 --> 00:20:37,720
And these inequities stirred up some
serious discontent among the masses.

299
00:20:41,520 --> 00:20:44,080
We know of the role that tea
and taxes played

300
00:20:44,080 --> 00:20:48,000
in the American Revolution,

301
00:20:48,000 --> 00:20:51,840
but it could also be said that
baguettes and bakers

302
00:20:51,840 --> 00:20:56,640
played a role in the French
Revolution just a few years later.

303
00:20:56,640 --> 00:21:00,960
One of the very worst things
that the revolutionaries

304
00:21:00,960 --> 00:21:03,080
were concerned
about in revolutionary France,

305
00:21:03,080 --> 00:21:07,000
they were concerned about a lack
of fairness with measurements.

306
00:21:08,760 --> 00:21:13,720
Bread was the main component
of the French working class diet.

307
00:21:13,720 --> 00:21:17,120
The average 18th century worker
spent half

308
00:21:17,120 --> 00:21:20,400
their hard-earned dough on it.

309
00:21:20,400 --> 00:21:23,640
It was so important, the king
controlled all aspects

310
00:21:23,640 --> 00:21:27,800
of bread production, including the
price of loaves.

311
00:21:29,600 --> 00:21:32,160
With France in the middle
of a historic famine,

312
00:21:32,160 --> 00:21:35,600
and different standard units of
measure in each village,

313
00:21:35,600 --> 00:21:38,200
weights could be fiddled,

314
00:21:38,200 --> 00:21:41,280
so people were often paying the same
for less

315
00:21:41,280 --> 00:21:45,320
and the poor had no way to prove
this was happening.

316
00:21:45,320 --> 00:21:47,160
The peasants were hangry...

317
00:21:47,160 --> 00:21:49,760
..and revolting.

318
00:21:49,760 --> 00:21:54,920
France was in turmoil. It began
with the execution of the king

319
00:21:54,920 --> 00:21:59,040
and ended with the accession
of Napoleon.

320
00:22:00,600 --> 00:22:04,520
Obviously, the causes of the
revolution were far more complicated

321
00:22:04,520 --> 00:22:06,840
than the price of bread,

322
00:22:06,840 --> 00:22:10,520
but it's fair to say it rather
brought things to a head.

323
00:22:12,880 --> 00:22:17,640
CHEERING AND APPLAUSE

324
00:22:19,680 --> 00:22:21,680
When the revolutionaries took over,

325
00:22:21,680 --> 00:22:25,160
it was recognised that one of their
priorities would be to put in place

326
00:22:25,160 --> 00:22:28,840
a measurement system that was going
to be fair.

327
00:22:28,840 --> 00:22:32,160
On April 7th, 1795,

328
00:22:32,160 --> 00:22:33,920
true to their word...

329
00:22:33,920 --> 00:22:37,160
A tous les temps,
a tous les peuples.

330
00:22:37,160 --> 00:22:40,320
"At all times,
to all peoples."

331
00:22:40,320 --> 00:22:44,240
The metric system was formally
enshrined in French law.

332
00:22:46,520 --> 00:22:48,120
This idea of

333
00:22:48,120 --> 00:22:50,160
a Democratic approach
to measurement,

334
00:22:50,160 --> 00:22:54,160
this wasn't tied to the length
of the king's foot

335
00:22:54,160 --> 00:22:56,800
or something like that.

336
00:22:56,800 --> 00:23:01,280
Instead, they turned back
to constants found in nature,

337
00:23:01,280 --> 00:23:05,560
but in a much more scientific
and global way.

338
00:23:05,560 --> 00:23:09,880
They were going to
use the Earth itself.

339
00:23:09,880 --> 00:23:12,680
Anybody could access
the circumference of the Earth

340
00:23:12,680 --> 00:23:16,920
and nobody could change
the circumference of the Earth.

341
00:23:16,920 --> 00:23:19,680
For example, a metre
would be a fraction

342
00:23:19,680 --> 00:23:22,240
of the planet's circumference.

343
00:23:22,240 --> 00:23:24,680
But at the time, this proved too
difficult

344
00:23:24,680 --> 00:23:27,120
to measure precisely and
consistently.

345
00:23:30,760 --> 00:23:34,080
So they decided to create
physical points of reference

346
00:23:34,080 --> 00:23:39,160
for these new units - they made
artefacts.

347
00:23:42,280 --> 00:23:45,440
The original artefacts
of the Metric Revolution

348
00:23:45,440 --> 00:23:48,440
are now locked away in
the Archives Nationales.

349
00:23:51,200 --> 00:23:54,320
SPEAKING FRENCH

350
00:23:54,320 --> 00:23:59,840
One of the first decisions of the
National Assembly

351
00:23:59,840 --> 00:24:03,200
was to create first the metre

352
00:24:03,200 --> 00:24:06,200
and then the kilogram.

353
00:24:07,720 --> 00:24:11,240
They defined a new unit of mass -

354
00:24:11,240 --> 00:24:14,640
that was the mass of a litre
of water -

355
00:24:14,640 --> 00:24:17,480
and they called
that the kilogram.

356
00:24:19,960 --> 00:24:25,040
And this is the first prototype
of what we call

357
00:24:25,040 --> 00:24:27,680
le Kilogramme des Archives.

358
00:24:27,680 --> 00:24:31,200
It was made at the end of the
18th century,

359
00:24:31,200 --> 00:24:33,680
fabricated in platinum.

360
00:24:35,080 --> 00:24:38,440
Under the French Revolution,

361
00:24:38,440 --> 00:24:43,400
citizens could be involved in the
decision-making process of the unit.

362
00:24:43,400 --> 00:24:45,800
It's a kind of democracy.

363
00:24:45,800 --> 00:24:49,200
Among the things that people were
thinking about was...

364
00:24:49,200 --> 00:24:53,160
..liberte, egalite, fraternite.

365
00:24:53,160 --> 00:24:56,240
And part of this was that the system
of measurement

366
00:24:56,240 --> 00:24:59,600
should be something that should be
accessible to everybody.

367
00:24:59,600 --> 00:25:03,360
And that has been the mass system
that we've maintained for years.

368
00:25:03,360 --> 00:25:04,840
And it has worked.

369
00:25:04,840 --> 00:25:06,480
It has served us well.

370
00:25:07,880 --> 00:25:11,760
So, if it's not broken, why fix it?

371
00:25:11,760 --> 00:25:15,120
Well, apart from the possibilities
of damage to

372
00:25:15,120 --> 00:25:17,760
or theft of an irreplaceable
artefact,

373
00:25:17,760 --> 00:25:21,840
metrologists are thinking
about the future.

374
00:25:21,840 --> 00:25:26,440
Redefinition allows us many
things - two that come to mind.

375
00:25:26,440 --> 00:25:33,560
One is we freeze any potential
drift in the mass of this artefact.

376
00:25:33,560 --> 00:25:36,400
Then it allows us to go
from the quantum level

377
00:25:36,400 --> 00:25:40,600
to the cosmic level without
changing scales or units.

378
00:25:40,600 --> 00:25:41,880
PHONE RINGS

379
00:25:41,880 --> 00:25:47,440
Most science and a lot of technology
is developed when we solve

380
00:25:47,440 --> 00:25:49,760
a measurement challenge.
MOBILE RINGS

381
00:25:49,760 --> 00:25:52,400
Having better access to better
definitions

382
00:25:52,400 --> 00:25:57,120
and better measurement techniques
actually propels the rest of society

383
00:25:57,120 --> 00:25:58,960
and its scientific progress forward.

384
00:25:58,960 --> 00:26:00,280
SMARTPHONE CAMERA SHUTTERS

385
00:26:00,280 --> 00:26:05,200
And that brings us to the next step,
which is to replace the present

386
00:26:05,200 --> 00:26:09,720
definition of the kilogram
with something that's not an object.

387
00:26:09,720 --> 00:26:12,800
Something that doesn't change
with time,

388
00:26:12,800 --> 00:26:14,720
that doesn't get destroyed.

389
00:26:14,720 --> 00:26:18,760
Something that you can reproduce
everywhere, anywhere in the world.

390
00:26:22,640 --> 00:26:28,200
We have faced this kind of situation
repeatedly in metrology.

391
00:26:28,200 --> 00:26:35,320
It used to be that a second was
1/24 x 60 x 60 of a day.

392
00:26:35,320 --> 00:26:39,160
The trouble is that by the early
20th century,

393
00:26:39,160 --> 00:26:43,120
it was clear that a day
was not a constant thing.

394
00:26:43,120 --> 00:26:46,480
And that realisation meant
that we had to change

395
00:26:46,480 --> 00:26:48,880
the definition of time.

396
00:26:48,880 --> 00:26:52,240
And they did this by using what
metrologists call

397
00:26:52,240 --> 00:26:55,480
fundamental constants.

398
00:26:55,480 --> 00:26:58,200
Fundamental constant doesn't change.

399
00:26:58,200 --> 00:27:01,240
It's universally constant.

400
00:27:01,240 --> 00:27:05,400
Today, the definition of time is
based on atomic standards,

401
00:27:05,400 --> 00:27:09,800
it's based on the unchanging
frequencies of atoms.

402
00:27:11,640 --> 00:27:15,560
And, like the second, fundamental
constants have been used

403
00:27:15,560 --> 00:27:18,160
to redefine other units of the SI.

404
00:27:19,720 --> 00:27:23,400
Originally for the metre, it used
to be a metre stick.

405
00:27:23,400 --> 00:27:27,880
Now it's based on the speed of light
in a vacuum...

406
00:27:27,880 --> 00:27:31,240
Which sounds like it isn't a
profound change,

407
00:27:31,240 --> 00:27:35,360
but it actually is
an incredibly profound change.

408
00:27:35,360 --> 00:27:40,040
This moves the reference for
objective reality away

409
00:27:40,040 --> 00:27:44,440
from a man-made artefact
and onto an unchanging constant

410
00:27:44,440 --> 00:27:46,480
of the universe.

411
00:27:46,480 --> 00:27:49,000
In the case of the kilogram,
we're moving from an artefact

412
00:27:49,000 --> 00:27:50,840
to basically an equation.

413
00:27:54,240 --> 00:27:56,600
But, unlike the speed of light,

414
00:27:56,600 --> 00:28:01,440
there's no obvious fundamental
constant to redefine mass.

415
00:28:02,760 --> 00:28:06,160
Cue two obscure but promising
contenders -

416
00:28:06,160 --> 00:28:07,840
one from chemistry,

417
00:28:07,840 --> 00:28:10,000
the other from physics.

418
00:28:10,000 --> 00:28:12,560
The teams representing each

419
00:28:12,560 --> 00:28:16,640
are tackling the same
kilogram-sized problem,

420
00:28:16,640 --> 00:28:20,560
but a bit of friendly
competition never hurts.

421
00:28:20,560 --> 00:28:24,720
It's very challenging
and then it's competitive, too.

422
00:28:24,720 --> 00:28:26,760
There is national pride at stake.

423
00:28:26,760 --> 00:28:31,000
Everyone wants to be the lab that
changes the face of the kilogram.

424
00:28:31,000 --> 00:28:33,840
One group set out to define
the kilogram

425
00:28:33,840 --> 00:28:36,600
using the Avogadro constant.

426
00:28:36,600 --> 00:28:38,040
Of course there is competition.

427
00:28:38,040 --> 00:28:42,600
Of course that is the power who
brings us further.

428
00:28:42,600 --> 00:28:45,640
The other, using
the Planck constant.

429
00:28:45,640 --> 00:28:47,880
One of the things that makes
metrology unique

430
00:28:47,880 --> 00:28:51,480
is we rely on other people
repeating our measurements.

431
00:28:51,480 --> 00:28:54,320
Rivalry in metrology is
extremely useful.

432
00:28:54,320 --> 00:28:56,800
People will go out of their way

433
00:28:56,800 --> 00:28:59,240
to think of new ways of doing
things.

434
00:28:59,240 --> 00:29:01,280
And some of them will survive,

435
00:29:01,280 --> 00:29:03,840
some of them won't.

436
00:29:03,840 --> 00:29:08,440
Both routes would push the team
to the limits of what's possible.

437
00:29:13,280 --> 00:29:17,240
The first candidate is a fundamental
constant from chemistry,

438
00:29:17,240 --> 00:29:19,160
the Avogadro constant.

439
00:29:20,800 --> 00:29:27,280
Named after the early 19th century
Italian scientist Amedeo Avogadro,

440
00:29:27,280 --> 00:29:30,520
the Avogadro constant is currently
defined by the SI

441
00:29:30,520 --> 00:29:33,840
as the number of atoms in one mole.

442
00:29:33,840 --> 00:29:36,240
No, not that kind of mole!

443
00:29:37,880 --> 00:29:41,640
The "mole" is a unit that describes
the amount of substance

444
00:29:41,640 --> 00:29:47,360
that's equal to the number of atoms
in 12g of carbon-12.

445
00:29:47,360 --> 00:29:49,480
This is currently calculated to
be...

446
00:29:49,480 --> 00:29:54,320
602 sextillion 214 quintillion...

447
00:29:54,320 --> 00:29:58,880
..85 quadrillion 774 trillion atoms.

448
00:30:01,640 --> 00:30:06,680
To put that in perspective,
that's 80,000 times more atoms

449
00:30:06,680 --> 00:30:09,960
than there are grains of sand
in all the beaches,

450
00:30:09,960 --> 00:30:13,320
deserts and sandpits
in the entire world.

451
00:30:16,080 --> 00:30:18,320
To further complicate things,

452
00:30:18,320 --> 00:30:21,720
those 12g are still defined
by the IPK.

453
00:30:23,480 --> 00:30:27,760
So why, then, posited scientists,
can't we do the reverse -

454
00:30:27,760 --> 00:30:31,360
use Avogadro's constant to define
the kilogram?

455
00:30:37,320 --> 00:30:42,440
One of the teams tackling
this is the...

456
00:30:42,440 --> 00:30:45,360
..in Germany.

457
00:30:45,360 --> 00:30:51,360
The PTB is a very
accurate, organised little machine.

458
00:30:51,360 --> 00:30:52,640
Not that little.

459
00:30:55,560 --> 00:30:58,360
It's home to team members

460
00:30:58,360 --> 00:31:01,360
including PhD student Edyta Beyer,

461
00:31:01,360 --> 00:31:06,560
physicist and fossil hunter
Ingo Busch,

462
00:31:06,560 --> 00:31:11,720
and physicist, engineer and
precision marksman Arnold Nicolaus.

463
00:31:15,280 --> 00:31:19,360
They're working with the National
Metrology Institute of Japan

464
00:31:19,360 --> 00:31:23,880
to build cutting-edge technology to
crack this Avogadro endeavour.

465
00:31:28,000 --> 00:31:30,760
PIANO PLAYS

466
00:31:30,760 --> 00:31:35,840
Here, team members, including prime
senior researcher, and pianist,

467
00:31:35,840 --> 00:31:38,000
Kenichi Fujii,

468
00:31:38,000 --> 00:31:41,960
surface and nano-analysis group
physicist, and flower arranger,

469
00:31:41,960 --> 00:31:44,280
Lulu Zhang,

470
00:31:44,280 --> 00:31:47,640
mass standards group leader,
and weightlifter,

471
00:31:47,640 --> 00:31:49,840
Naoki Kuramoto,

472
00:31:49,840 --> 00:31:53,560
are led by director general,
and avid motorcyclist,

473
00:31:53,560 --> 00:31:56,080
Takashi Usuda.
REVS ENGINE

474
00:32:01,480 --> 00:32:04,960
When I'm hearing a great symphony,

475
00:32:04,960 --> 00:32:08,920
it encourages me
to invent something new.

476
00:32:08,920 --> 00:32:13,680
PIANO PLAYS

477
00:32:13,680 --> 00:32:15,280
FADES

478
00:32:17,800 --> 00:32:22,800
Both teams are aiming to redefine
the kilogram as an equation

479
00:32:22,800 --> 00:32:26,880
by measuring the value of Avogadro's
constant more precisely

480
00:32:26,880 --> 00:32:29,080
and more accurately than ever
before.

481
00:32:31,080 --> 00:32:35,200
And they custom-make the perfect
tools for the job.

482
00:32:36,400 --> 00:32:40,400
I'm working with the roundest object
on the Earth,

483
00:32:40,400 --> 00:32:45,320
which is made from the purest
silicon on the Earth.

484
00:32:45,320 --> 00:32:48,360
And machining them
is no walk in the park.

485
00:32:51,080 --> 00:32:53,800
Mechanical engineer Rudolf Mees

486
00:32:53,800 --> 00:32:57,240
has spent years
perfecting the process.

487
00:32:57,240 --> 00:33:02,000
The first steps, we remove several
grams per hour,

488
00:33:02,000 --> 00:33:07,480
but in the end, the removal rate is
just one nanometre per minute

489
00:33:07,480 --> 00:33:11,040
and takes three months
to produce a sphere.

490
00:33:15,120 --> 00:33:20,760
The result is an almost perfect
sphere of almost perfect purity

491
00:33:20,760 --> 00:33:26,360
and a price tag of several
millions of dollars per sphere.

492
00:33:26,360 --> 00:33:29,120
CASH REGISTER DINGS

493
00:33:29,120 --> 00:33:33,520
Luckily for the Avogadro team,
these spheres aren't irreplaceable

494
00:33:33,520 --> 00:33:37,080
artefacts like the IPK.

495
00:33:37,080 --> 00:33:42,680
Rather, they're just astoundingly
accurate, if expensive, tools.

496
00:33:42,680 --> 00:33:46,880
The silicon sphere is much
more than just a mass standard,

497
00:33:46,880 --> 00:33:51,440
it's a counting machine
for atoms.

498
00:33:51,440 --> 00:33:54,080
New spheres can be made.

499
00:33:54,080 --> 00:33:57,040
But their perfection is priceless.

500
00:33:57,040 --> 00:34:01,640
It allows them to be measured
to previously unfathomable precision

501
00:34:01,640 --> 00:34:04,160
and determine the exact number
of atoms

502
00:34:04,160 --> 00:34:06,440
inside each one.

503
00:34:08,200 --> 00:34:12,440
But there are so many atoms
inside that if you could count them

504
00:34:12,440 --> 00:34:15,160
at a speed of ten million atoms per
second,

505
00:34:15,160 --> 00:34:19,480
it would take you 68 billion years.

506
00:34:19,480 --> 00:34:23,400
Or about five times longer
than the universe has existed.

507
00:34:32,000 --> 00:34:36,200
So they use their sphere's
remarkable shape and structure

508
00:34:36,200 --> 00:34:40,840
to calculate Avogadro's constant
instead.

509
00:34:40,840 --> 00:34:44,240
Imagine we have a truck full
of oranges.

510
00:34:44,240 --> 00:34:49,320
So we measure the truck,
that's the volume of the sphere.

511
00:34:49,320 --> 00:34:51,600
We measure the volume of an orange,

512
00:34:51,600 --> 00:34:54,320
that's the volume of the atom.

513
00:34:55,560 --> 00:35:00,200
And together with the information
about the inside organisation

514
00:35:00,200 --> 00:35:04,080
of the oranges, we know
exactly how many oranges

515
00:35:04,080 --> 00:35:09,160
are inside and we can determine our
Avogadro constant.

516
00:35:09,160 --> 00:35:12,680
With their perfect spheres and
meticulous measurement,

517
00:35:12,680 --> 00:35:16,200
the Avogadro project aren't
pulling their punches.

518
00:35:16,200 --> 00:35:19,240
But there's another heavyweight
contender competing

519
00:35:19,240 --> 00:35:22,560
in the kilogram redefinition ring...

520
00:35:22,560 --> 00:35:25,640
..the Planck constant.

521
00:35:29,640 --> 00:35:32,720
Named after the German physicist
who discovered it,

522
00:35:32,720 --> 00:35:36,920
Max Karl Ernst Ludwig Planck,

523
00:35:36,920 --> 00:35:40,160
it's a fundamental constant
that even top metrologists

524
00:35:40,160 --> 00:35:43,240
have trouble summing up.

525
00:35:43,240 --> 00:35:45,760
If you go...
Well, let's see how I can do this.

526
00:35:45,760 --> 00:35:48,440
How would I...? I've got to think
about this a bit more

527
00:35:48,440 --> 00:35:50,280
cos that's a hard, hard question
to explain

528
00:35:50,280 --> 00:35:51,800
what Planck's constant is.

529
00:35:51,800 --> 00:35:54,640
Oh, God, jeez. Erm...

530
00:35:54,640 --> 00:35:57,680
Did we want to try and describe what
Planck's constant is?

531
00:35:57,680 --> 00:35:59,200
Erm, no.

532
00:36:02,800 --> 00:36:05,720
The actual constant may be hard
to explain,

533
00:36:05,720 --> 00:36:07,960
but the concept is easy enough.

534
00:36:10,280 --> 00:36:14,120
In the late-1800,
physics was facing a crisis.

535
00:36:14,120 --> 00:36:17,800
Physicists were trying to model
atomic vibrations,

536
00:36:17,800 --> 00:36:20,440
but they kept getting it wrong.

537
00:36:20,440 --> 00:36:24,360
They'd assumed that atomic
vibrations were continuous.

538
00:36:24,360 --> 00:36:28,400
That is, they could vibrate
at any frequency.

539
00:36:28,400 --> 00:36:31,600
Planck came up with a kind
of a crazy idea.

540
00:36:31,600 --> 00:36:34,720
He said it's not a continuous
process.

541
00:36:34,720 --> 00:36:37,160
It's always in little packets of
energy,

542
00:36:37,160 --> 00:36:39,680
that today we call photons.

543
00:36:39,680 --> 00:36:42,280
Think of it like your morning
coffee.

544
00:36:42,280 --> 00:36:44,400
When you order your Americano,

545
00:36:44,400 --> 00:36:47,480
you can add sugar in two different
ways -

546
00:36:47,480 --> 00:36:49,640
as a continuous stream

547
00:36:49,640 --> 00:36:51,320
or as cubes.

548
00:36:54,040 --> 00:36:57,440
Planck postulated that you could
only change energy

549
00:36:57,440 --> 00:36:59,000
in minimal increments,

550
00:36:59,000 --> 00:37:01,680
like sugar cubes.

551
00:37:01,680 --> 00:37:04,360
And the field of quantum mechanics
was born.

552
00:37:06,400 --> 00:37:11,960
It was a surprise to everyone
that energy was quantized,

553
00:37:11,960 --> 00:37:16,880
and it changed our understanding
of physics entirely.

554
00:37:18,320 --> 00:37:21,600
And because Planck's constant
relates to energy,

555
00:37:21,600 --> 00:37:27,400
you can link it to an object's mass
via Einstein's relativity equation,

556
00:37:27,400 --> 00:37:32,400
energy is equal to mass times
the speed of light squared,

557
00:37:32,400 --> 00:37:36,600
using Planck's constant
to redefine the kilogram.

558
00:37:41,520 --> 00:37:46,000
But first, metrologists
have to measure it.

559
00:37:46,000 --> 00:37:49,600
Doing the heavy lifting for the
Planck constant are labs like

560
00:37:49,600 --> 00:37:51,640
the National Research Council,

561
00:37:51,640 --> 00:37:53,200
in Canada.

562
00:37:56,120 --> 00:37:57,600
CHATTERING

563
00:37:57,600 --> 00:38:00,400
We spent a lot of hours,
a lot of long, long hours.

564
00:38:00,400 --> 00:38:03,200
Physics runs on coffee
for the most part.

565
00:38:03,200 --> 00:38:07,680
Team members including research
offices in electrical measurements

566
00:38:07,680 --> 00:38:13,080
Carlos Sanchez and Barry Wood,

567
00:38:13,080 --> 00:38:18,840
and dedicated dad and team leader
in mass metrology Richard Green,

568
00:38:18,840 --> 00:38:24,760
are led by Canada's
chief metrologist Alan Steele.

569
00:38:24,760 --> 00:38:27,360
Intense, dedicated.

570
00:38:27,360 --> 00:38:29,320
You know, no
fear of taking things apart

571
00:38:29,320 --> 00:38:31,680
and putting them back together over
and over and over again

572
00:38:31,680 --> 00:38:32,920
until you get it right.

573
00:38:36,400 --> 00:38:40,960
The NRC are joined by yet another
set of Planck pioneers...

574
00:38:40,960 --> 00:38:44,360
O SAY, CAN YOU SEE PLAYS

575
00:38:44,360 --> 00:38:49,760
..from the National Institute
of Standards and Technology,

576
00:38:49,760 --> 00:38:52,040
in the United States of America.

577
00:38:58,680 --> 00:39:01,520
PLAYS BLUES GUITAR

578
00:39:01,520 --> 00:39:05,160
Team members include chief of the
Quantum Measurements Division,

579
00:39:05,160 --> 00:39:09,120
and string-strummer,
Jon Pratt.

580
00:39:09,120 --> 00:39:11,280
It's certainly a common stereotype,

581
00:39:11,280 --> 00:39:14,720
but I feel like it's a little bit
of truth -

582
00:39:14,720 --> 00:39:18,480
the US tends to be a little bit more
freewheeling

583
00:39:18,480 --> 00:39:20,200
on these types of things.

584
00:39:20,200 --> 00:39:22,640
"Ha, that's a great new idea!
Let's go do that!"

585
00:39:22,640 --> 00:39:26,920
Leader of the Mass and Force Group,
and coffee aficionado,

586
00:39:26,920 --> 00:39:29,320
Zeina Kubarych,

587
00:39:29,320 --> 00:39:34,000
Mass and Force Group physicist,
and technical tinkerer,

588
00:39:34,000 --> 00:39:35,600
Patrick Abbott,

589
00:39:35,600 --> 00:39:39,320
and Fundamental Electrical
Measurements Group physicist,

590
00:39:39,320 --> 00:39:44,360
and should-be prizewinning pretzel
maker, Stephan Schlamminger.

591
00:39:44,360 --> 00:39:46,160
I think we have a very strong team.

592
00:39:46,160 --> 00:39:50,080
I think there's almost no technical
problem that we can't solve.

593
00:39:54,280 --> 00:39:57,520
To derive the most precise
and accurate possible value

594
00:39:57,520 --> 00:40:01,760
of Planck's constant, both teams
are measuring a readily available

595
00:40:01,760 --> 00:40:04,320
supply of calibrated kilograms

596
00:40:04,320 --> 00:40:08,200
in an electromagnetic device called
a watt balance.

597
00:40:09,680 --> 00:40:16,280
The watt balance is simply a clever
device that can weigh a mass

598
00:40:16,280 --> 00:40:18,720
using only electrical measurements.

599
00:40:20,240 --> 00:40:22,560
The watt balance's basic
principle is

600
00:40:22,560 --> 00:40:26,880
you're comparing a gravitational
force to electromagnetic force.

601
00:40:28,720 --> 00:40:33,160
Think of it like an electromagnet
in a scrapyard.

602
00:40:33,160 --> 00:40:36,800
Larger cars have a greater
gravitational force pulling on them,

603
00:40:36,800 --> 00:40:38,600
making them heavier,

604
00:40:38,600 --> 00:40:43,800
so more electrical current is
required to overcome gravity

605
00:40:43,800 --> 00:40:45,760
and lift a heavier car.

606
00:40:47,000 --> 00:40:49,640
CHILD LAUGHS

607
00:40:52,000 --> 00:40:55,000
Except, instead of pulling an object
upwards,

608
00:40:55,000 --> 00:40:58,320
the watt balance electromagnet
pushes it up

609
00:40:58,320 --> 00:41:02,800
against the force of gravity until
the electrical force equals

610
00:41:02,800 --> 00:41:05,320
the mass of the now balanced object

611
00:41:05,320 --> 00:41:08,360
without the need to compare it to
anything

612
00:41:08,360 --> 00:41:10,120
on the other side of the scale.

613
00:41:12,040 --> 00:41:16,600
This gives the watt balance the
ability to link electrical energy

614
00:41:16,600 --> 00:41:21,760
and its base unit, Planck's
constant, to the mass of an object.

615
00:41:25,800 --> 00:41:31,000
But devising a device to measure
the quantity of this force exactly

616
00:41:31,000 --> 00:41:33,880
required the genius of
Dr Bryan Kibble,

617
00:41:33,880 --> 00:41:38,320
who cracked the engineering of the
world's first watt balance...

618
00:41:39,640 --> 00:41:42,600
..at the
National Physical Laboratory

619
00:41:42,600 --> 00:41:44,440
in the United Kingdom.

620
00:41:48,640 --> 00:41:53,080
This laboratory was where the
watt balance was born.

621
00:41:53,080 --> 00:41:56,680
Bryan Kibble and I built the
first one here.

622
00:41:56,680 --> 00:42:00,480
Today, the balance is also called
the Kibble balance,

623
00:42:00,480 --> 00:42:02,440
in honour of its inventor.

624
00:42:03,760 --> 00:42:07,800
His legacy lives on through the work
of the lab's many contributors,

625
00:42:07,800 --> 00:42:12,400
including electrical measurement
specialist Ian Robinson

626
00:42:12,400 --> 00:42:16,640
and research scientist
Perdi Williams.

627
00:42:16,640 --> 00:42:18,640
I don't think you could get
a more British place

628
00:42:18,640 --> 00:42:20,600
than this crazy British lab.

629
00:42:21,760 --> 00:42:25,480
We have tea parties in the office
and there's a grand piano.

630
00:42:25,480 --> 00:42:26,480
Cheers.

631
00:42:29,680 --> 00:42:33,560
I described the basement lab
as Ian's brain

632
00:42:33,560 --> 00:42:35,920
has just thrown up in a lab.

633
00:42:37,400 --> 00:42:41,120
Some of the most ground-breaking
science is done in a messy,

634
00:42:41,120 --> 00:42:46,320
unorganised shed in the basement
of a massive stately home.

635
00:42:47,560 --> 00:42:51,880
Whilst the NPL are no longer
in the business of weighing kilos,

636
00:42:51,880 --> 00:42:54,720
they are leading the world in
building affordable

637
00:42:54,720 --> 00:42:58,080
miniature Kibble balances for the
masses.

638
00:42:58,080 --> 00:43:00,600
We're now in the lucky position of
being able

639
00:43:00,600 --> 00:43:03,120
to build a generation of balance

640
00:43:03,120 --> 00:43:06,840
that should take the balance out and
make it egalitarian.

641
00:43:06,840 --> 00:43:09,560
Everybody in the world should be
able to access

642
00:43:09,560 --> 00:43:13,120
this technology and contribute
to the world mass scale.

643
00:43:15,360 --> 00:43:19,520
And they're lending their expertise
in watt balance building

644
00:43:19,520 --> 00:43:22,720
to a devilishly difficult task
for good reason.

645
00:43:22,720 --> 00:43:25,800
Measuring the Planck constant
to the level that we need

646
00:43:25,800 --> 00:43:27,480
is extremely difficult.

647
00:43:31,440 --> 00:43:34,880
Working with the watt balance is,
I would say,

648
00:43:34,880 --> 00:43:36,960
an emotional roller-coaster.

649
00:43:36,960 --> 00:43:38,760
Bring it down and have a look.

650
00:43:38,760 --> 00:43:40,880
And building this thing was
exhausting

651
00:43:40,880 --> 00:43:43,120
and kind of, "Oh, my God, is it
going to work?" You know?

652
00:43:43,120 --> 00:43:45,320
Can you see it? Stop it there.

653
00:43:45,320 --> 00:43:48,960
The watt balance is a really, really
hard experiment.

654
00:43:48,960 --> 00:43:52,400
These instruments tend to have a
certain character to them

655
00:43:52,400 --> 00:43:57,040
that only the people who built them
can really make them work the way

656
00:43:57,040 --> 00:43:59,560
that they're supposed to work.

657
00:43:59,560 --> 00:44:04,200
We need to consider about 100
different effects that affect

658
00:44:04,200 --> 00:44:05,920
the measurement.

659
00:44:05,920 --> 00:44:08,040
From noise, temperature,
magnetic fields,

660
00:44:08,040 --> 00:44:11,240
we need to measure all those things
and to a level

661
00:44:11,240 --> 00:44:14,040
that we haven't been able to measure
before.

662
00:44:14,040 --> 00:44:15,920
This is a big change
we're proposing.

663
00:44:15,920 --> 00:44:18,400
We'd like to get it right.

664
00:44:21,480 --> 00:44:25,120
After years of painstaking trial
and error,

665
00:44:25,120 --> 00:44:28,880
a decision has to be made about
which fundamental constant

666
00:44:28,880 --> 00:44:33,120
would redefine the kilogram.

667
00:44:33,120 --> 00:44:36,800
In 2011, the metrological community
decrees Planck,

668
00:44:36,800 --> 00:44:40,520
and its ability to link all
electrical units in the SI,

669
00:44:40,520 --> 00:44:43,000
as their constant of choice.

670
00:44:44,760 --> 00:44:46,680
But there's a twist

671
00:44:46,680 --> 00:44:49,880
which means that the work of the
Avogadro teams

672
00:44:49,880 --> 00:44:53,000
can still contribute to the
redefinition effort.

673
00:44:53,000 --> 00:44:57,200
The Avogadro constant and Planck's
constant are very closely related

674
00:44:57,200 --> 00:44:58,920
to each other.

675
00:44:58,920 --> 00:45:02,080
If you have one of these two
constants,

676
00:45:02,080 --> 00:45:05,120
you will get the second
constant for free.

677
00:45:07,280 --> 00:45:13,160
And that's the way Planck's constant
occurs in the silicon sphere.

678
00:45:13,160 --> 00:45:15,600
That's it.

679
00:45:15,600 --> 00:45:18,240
The challenge now becomes
that the Planck values

680
00:45:18,240 --> 00:45:20,880
from both experiments must match.

681
00:45:20,880 --> 00:45:25,600
So if both projects result in the
same numbers,

682
00:45:25,600 --> 00:45:31,720
then I think there is no doubt
to redefine the kilogram.

683
00:45:31,720 --> 00:45:35,400
If they don't, then something
has gone very wrong.

684
00:45:42,320 --> 00:45:44,720
Today is one of the most important
meetings

685
00:45:44,720 --> 00:45:47,280
of the
Consultative Committee for Mass.

686
00:45:49,680 --> 00:45:54,240
Today is the deadline for the teams
to get their results in.

687
00:45:56,360 --> 00:45:59,360
Everybody is coming up with their
answers at the very last minute,

688
00:45:59,360 --> 00:46:01,840
Canada's was just accepted about a
week and a half ago.

689
00:46:01,840 --> 00:46:05,280
The German Avogadro number came
about three or four days ago.

690
00:46:05,280 --> 00:46:07,720
The NMIJ one came out about two
days ago.

691
00:46:07,720 --> 00:46:11,120
Just yesterday, I think
it was, from the United States.

692
00:46:11,120 --> 00:46:17,440
Today, they decide if the data is
good enough to be put to the vote.

693
00:46:17,440 --> 00:46:20,040
The CCM put up some conditions

694
00:46:20,040 --> 00:46:24,160
which should be fulfilled in order
to go for redefinition.

695
00:46:24,160 --> 00:46:26,560
We want to all have agreement on
what the value

696
00:46:26,560 --> 00:46:30,800
for Planck's constant is,
and a new value has come online

697
00:46:30,800 --> 00:46:35,480
which is controversially
maybe possibly a little bit out.

698
00:46:35,480 --> 00:46:38,560
Some countries think that the
criteria have been met and others

699
00:46:38,560 --> 00:46:39,960
think they have not been met.

700
00:46:39,960 --> 00:46:45,480
And this is now an intense
discussion on how we should proceed.

701
00:46:45,480 --> 00:46:48,320
If they cannot reach an agreement,

702
00:46:48,320 --> 00:46:52,120
the whole redefinition
could be called off.

703
00:46:52,120 --> 00:46:55,280
For us, it would mean four more
years of digging for uncertainties.

704
00:46:55,280 --> 00:46:58,080
And I don't think we can...

705
00:46:58,080 --> 00:47:00,920
I don't want to do that.
I want to move on to other science.

706
00:47:00,920 --> 00:47:02,960
As the debate becomes more heated,

707
00:47:02,960 --> 00:47:06,120
it continues behind closed doors.

708
00:47:06,120 --> 00:47:08,120
One year ago, I would have said

709
00:47:08,120 --> 00:47:10,640
everything's set for the
redefinition.

710
00:47:10,640 --> 00:47:14,440
Now, in the recent times, I'm not
certain if the current status

711
00:47:14,440 --> 00:47:16,560
of knowledge will be considered
to be enough

712
00:47:16,560 --> 00:47:18,000
by the general conference.

713
00:47:23,760 --> 00:47:26,760
But in the always exciting
world of metrology,

714
00:47:26,760 --> 00:47:29,200
nothing is ever straightforward.

715
00:47:29,200 --> 00:47:32,920
The teams are being given just two
months to publish values

716
00:47:32,920 --> 00:47:35,840
in closer alignment for Planck's
constant

717
00:47:35,840 --> 00:47:39,360
or risk putting next year's
redefinition vote in jeopardy.

718
00:47:39,360 --> 00:47:41,120
Right now, we should be writing.

719
00:47:41,120 --> 00:47:42,800
And we're still not writing our
article,

720
00:47:42,800 --> 00:47:44,600
instead we are still doing
measurements.

721
00:47:44,600 --> 00:47:46,080
So I think it will be a close call.

722
00:47:46,080 --> 00:47:49,960
I think we have a whole bunch
of all-nighters to get it done.

723
00:47:49,960 --> 00:47:51,440
Once the papers are in,

724
00:47:51,440 --> 00:47:54,000
the Avogadro and Kibble balance
teams

725
00:47:54,000 --> 00:47:58,200
will average their numbers to obtain
the lowest possible uncertainty

726
00:47:58,200 --> 00:48:01,600
for the final fixed value of
Planck's constant.

727
00:48:01,600 --> 00:48:04,520
Uncertainty is always sort
of this measurement of how confident

728
00:48:04,520 --> 00:48:07,160
you are in that number.

729
00:48:07,160 --> 00:48:10,440
The worst thing a metrologist can do
is have a number that turns out

730
00:48:10,440 --> 00:48:12,320
to be outside their uncertainties.

731
00:48:12,320 --> 00:48:16,240
And that's...that's our idea
of hell, I think.

732
00:48:16,240 --> 00:48:20,520
We still have some problems to
solve.

733
00:48:20,520 --> 00:48:25,280
And I think the pressure
is too big for the redefinition

734
00:48:25,280 --> 00:48:27,880
and for the redesigning of the SI.

735
00:48:29,840 --> 00:48:32,920
I'm sympathetic
to the conservatives,

736
00:48:32,920 --> 00:48:36,520
but I'm also a US guy and I'm just,
like, let's change.

737
00:48:40,240 --> 00:48:44,000
The final agreed numbers for
Planck's constant roll in,

738
00:48:44,000 --> 00:48:46,480
fixing its value in the
kilogram equation.

739
00:48:47,680 --> 00:48:51,640
There's nothing more the teams
can do but wait.

740
00:48:51,640 --> 00:48:56,320
It's now up to the metrological
community of the world to vote

741
00:48:56,320 --> 00:48:59,960
on whether their consensus value
for Planck is good enough

742
00:48:59,960 --> 00:49:02,040
to redefine the kilogram.

743
00:49:02,040 --> 00:49:04,600
TENSE MUSIC PLAYS

744
00:49:09,960 --> 00:49:13,600
We're going to Versailles
to go and watch the vote!

745
00:49:14,600 --> 00:49:16,280
We'd better redefine the kilogram.

746
00:49:16,280 --> 00:49:18,240
We've done too much work
not to do it.

747
00:49:18,240 --> 00:49:22,400
Today's vote will determine
whether the kilogram will become

748
00:49:22,400 --> 00:49:25,440
an equation using Planck's constant,

749
00:49:25,440 --> 00:49:27,360
or if it will remain an artefact.

750
00:49:28,800 --> 00:49:31,320
The fact we've got multiple
experiments, multiple labs,

751
00:49:31,320 --> 00:49:34,560
means that we're pretty sure we've
got the right answer.

752
00:49:34,560 --> 00:49:37,960
Well, not "pretty sure" -
we've GOT the right answer.

753
00:49:43,200 --> 00:49:46,800
Now we're really getting close
to a win-win-win situation,

754
00:49:46,800 --> 00:49:48,520
so it's...nobody loses.

755
00:49:48,520 --> 00:49:51,240
So why would anybody want
to delay?

756
00:49:52,960 --> 00:49:55,600
It's way past time to re-define.

757
00:50:01,040 --> 00:50:04,880
You don't want science to ever be
limited by one particular artefact

758
00:50:04,880 --> 00:50:07,440
or one particular laboratory
or one particular experiment.

759
00:50:07,440 --> 00:50:10,400
And now we're ready.

760
00:50:10,400 --> 00:50:12,280
I think it's...it's time.

761
00:50:22,160 --> 00:50:27,120
Ladies and gentlemen, you have heard
that the proposal for the revision

762
00:50:27,120 --> 00:50:31,360
of the SI is that it
should be based on constants,

763
00:50:31,360 --> 00:50:33,240
on fundamental constants.

764
00:50:33,240 --> 00:50:36,320
Mr President, I think we're ready
to propose the vote.

765
00:50:36,320 --> 00:50:38,480
Thank you. Each country will be
called

766
00:50:38,480 --> 00:50:41,840
and you will say yes or no.

767
00:50:41,840 --> 00:50:43,160
Canada.

768
00:50:43,160 --> 00:50:45,160
SPEAKS FRENCH

769
00:50:45,160 --> 00:50:46,320
Oui.
Oui?

770
00:50:46,320 --> 00:50:47,360
Well, come here!

771
00:50:47,360 --> 00:50:48,920
APPLAUSE

772
00:50:48,920 --> 00:50:51,000
Kenya.
Yes.

773
00:50:51,000 --> 00:50:53,240
And India.
Yes.

774
00:50:53,240 --> 00:50:55,240
Japan.
Yes.

775
00:50:55,240 --> 00:50:56,560
CHUCKLES

776
00:50:56,560 --> 00:50:59,400
United States of America.
Yes.

777
00:50:59,400 --> 00:51:00,720
Korea.
Yes.

778
00:51:00,720 --> 00:51:01,920
Iran.
Yes.

779
00:51:01,920 --> 00:51:03,320
China. Yes.

780
00:51:03,320 --> 00:51:08,240
Yes. Yes.

781
00:51:08,240 --> 00:51:09,640
Yes!

782
00:51:09,640 --> 00:51:10,640
CHUCKLING

783
00:51:13,600 --> 00:51:20,520
The definition of the kilogram
is free from the artefact.

784
00:51:20,520 --> 00:51:22,320
We've redefined the kilogram.

785
00:51:22,320 --> 00:51:24,520
The vote was unanimous.

786
00:51:24,520 --> 00:51:26,200
Thank you so much.

787
00:51:26,200 --> 00:51:30,880
APPLAUSE

788
00:51:39,680 --> 00:51:42,960
To witness a historic moment like
that and be a part of it,

789
00:51:42,960 --> 00:51:46,600
I know that this is something
I will remember forever.

790
00:51:56,600 --> 00:51:59,360
It was the ride of my life,
you know? It was a lot of fun.

791
00:52:03,760 --> 00:52:07,040
We measured Planck's constant, but
what people really want to see...

792
00:52:07,040 --> 00:52:09,680
Are the tattoos.
..are the tatts.

793
00:52:09,680 --> 00:52:13,360
My tattoo in no way resembles
my job role,

794
00:52:13,360 --> 00:52:16,760
but I have Keeper Of The Kilogram
tattooed on my back.

795
00:52:16,760 --> 00:52:19,200
The idea of the French,

796
00:52:19,200 --> 00:52:23,520
that it would be a system of units
for all people for all times,

797
00:52:23,520 --> 00:52:27,560
I think we're really a lot
closer to that now.

798
00:52:27,560 --> 00:52:31,280
You know, I'm just overwhelmed
with the community that was built

799
00:52:31,280 --> 00:52:36,880
and come to consensus and make
progress...

800
00:52:38,240 --> 00:52:41,360
..real progress...

801
00:52:41,360 --> 00:52:44,000
..for mankind.

802
00:52:54,440 --> 00:52:58,040
In a monumental metrological moment,

803
00:52:58,040 --> 00:53:01,480
a Democratic equation anyone
can access at any time

804
00:53:01,480 --> 00:53:05,720
takes its place as the definition
of the kilogram.

805
00:53:10,000 --> 00:53:13,240
While metrologists get
back to work,

806
00:53:13,240 --> 00:53:17,040
the rest of the world continues
unaware.

807
00:53:18,720 --> 00:53:22,680
OK, so what's going to change
when we change the kilogram?

808
00:53:22,680 --> 00:53:26,120
How is that going to affect
the average person?

809
00:53:28,000 --> 00:53:32,160
When the kilogram is new-defined
and when we do a good job,

810
00:53:32,160 --> 00:53:35,400
no-one will notice it.
But that's good.

811
00:53:38,040 --> 00:53:40,800
When the person on the street
will start seeing differences

812
00:53:40,800 --> 00:53:44,600
is when new technologies start
getting built into better science

813
00:53:44,600 --> 00:53:46,080
or better products.

814
00:53:46,080 --> 00:53:48,440
I think that might happen in
individualised medicine

815
00:53:48,440 --> 00:53:50,840
or cellular medicine or
pharmaceuticals.

816
00:53:52,520 --> 00:53:55,520
The better we get at measuring
something,

817
00:53:55,520 --> 00:54:00,600
the bigger the world of opportunity
for scientific exploration becomes.

818
00:54:02,320 --> 00:54:04,880
There's a new undiscovered land.

819
00:54:04,880 --> 00:54:08,160
You know, we have wiped out all the
maps and said,

820
00:54:08,160 --> 00:54:10,680
"OK, something completely new."

821
00:54:14,880 --> 00:54:18,440
Some people think metrology is dull.

822
00:54:18,440 --> 00:54:22,880
They think it's some kind
of accountancy.

823
00:54:22,880 --> 00:54:25,720
That completely misses the point.

824
00:54:25,720 --> 00:54:28,840
Metrology is looking closer
and closer at things,

825
00:54:28,840 --> 00:54:32,080
seeing their form more perfectly,

826
00:54:32,080 --> 00:54:35,720
seeing them more clearly
in themselves,

827
00:54:35,720 --> 00:54:40,200
and just appreciating
the full wonder

828
00:54:40,200 --> 00:54:43,120
and beauty of the world
we have around us.

829
00:54:52,120 --> 00:54:55,240
WARM PIANO PLAYS

830
00:55:01,720 --> 00:55:06,200
So, Le Grande K
isn't really going away.

831
00:55:06,200 --> 00:55:09,400
It's going to be in that vault,
but it's still going to be with us

832
00:55:09,400 --> 00:55:15,880
because its mass at the time
of redefinition

833
00:55:15,880 --> 00:55:19,400
is essentially built into the
Planck's constant.

834
00:55:19,400 --> 00:55:21,880
It's immortalized, if you will.

835
00:55:26,240 --> 00:55:30,040
I feel quite weirdly protective
over a lump of metal.

836
00:55:33,800 --> 00:55:36,240
And, I mean, if they do want to get
rid of it one way,

837
00:55:36,240 --> 00:55:39,040
I'm happy to take it home
and look after it.

838
00:55:40,760 --> 00:55:43,760
PIANO PLAYS