- hace 3 meses
Categoría
📺
TVTranscripción
00:00This is the story of an artefact.
00:21No one knows quite how many artefacts have been created in the history of mankind, but needless
00:34to say that there have been a great many of them.
00:40From little Tommy Price's favourite catapult, and Mrs Miranda's decisively demonstrative
00:48damask doily, to young Pepina Peshlikai's perfect pre-teen pin-up.
00:57Each is an ideal version and definitive example of something truly important to its creator,
01:05an object against which all others can be measured.
01:09However, there are only a handful of artefacts that have been used as references by everyone.
01:20Standards so essential that their very existence underpins the functioning of our world.
01:28Some were used to define lengths, or volume, or time.
01:34Most have come and gone, but the one that defines what things weigh, their mass, still remains.
01:45Secured in an underground vault, locked by three separate keys, hidden from view.
01:55An unchanging constant in an ever-changing world.
02:01Until now.
02:25History is about to be made.
02:29The world's of over a hundred nations, from Indonesia to Egypt, are here to solve a crisis.
02:38They've put in millions of hours of effort, accomplishing engineering feats more complex than the moon landing.
02:48These humble men and women aren't business leaders or politicians, but their actions here will fundamentally change every aspect of our lives, from economics to medicine.
03:01Today, they will literally redefine the world as we know it.
03:07We're trying to get rid of a kilogram.
03:14But to understand what the kilogram actually is, and why they're so keen to get rid of it, we should start this story at the beginning.
03:24From the moment of our conception, through every aspect of our lives.
03:37From the inconsequential, to the life determining, the high points, and the low, right up to the very end.
03:52Everything about our existence is weighed and measured.
03:59We're a species obsessed with quantifying things, because objective measurements ensure everyone is dealt a fair hand in life.
04:07But that's a lot easier said than done.
04:20Luckily for us, there are hundreds of people, in different countries, spread out across the globe, working out the best ways to weigh and measure everything.
04:36They are normal people, with hopes, dreams, hobbies, and desires.
04:43Just like you and me, but with one minor difference.
04:47These men and women are the tellers of time, the masters of mass, the safeguarders of standards.
04:57They are metrologists.
05:04Metrology is really very, very important for industrial and the society.
05:09If there were no metrologists, we would have no measurement system.
05:13And we do crazy stuff. We measure glossiness of cats.
05:17We measure the acoustical crunches of biscuits.
05:22We measure the fastest speed.
05:28And we measure the smallest distance.
05:33And we measure the largest volume.
05:38Metrology is the science or the art of measurement.
05:43It means measuring things as in normal life, but pushing this measurement to the limits of technology.
05:50For centuries, metrologists have been working away around the clock to ensure that there are, in fact, accurate clocks to work around.
06:01And consistent rulers to measure with.
06:05And equitable masses to weigh.
06:08I think our motto should be, we worry about it so you don't have to.
06:13But there is a problem that metrologists are worried about.
06:23The weight of everything on the planet has been changing.
06:29The change is so small, few would even notice.
06:33Less than the weight of a grain of sand.
06:36But they have.
06:38No one really knows why it was happening.
06:41So that means no one can stop it really.
06:44That's alarming.
06:46It doesn't sound important, but with pharmaceuticals, that could be the difference between helping someone or hurting them.
06:59So now, it's up to the world's finest metrologists to shoulder the heavy burden.
07:05Together, they need to redefine the weight of the world.
07:10Fix it for all time.
07:15But time is not on their side.
07:27The clock is ticking.
07:33In just over a year, hundreds of delegates from around the world will travel to the General Conference on Weights and Measures in Versailles,
07:42expecting a solution to this weighty problem.
07:47It's not enough to work day and night.
07:51It's a scramble. It will be tight for us hitting the deadline.
07:54To succeed, they need to complete one of the most difficult experiments in the world.
08:03Ranked second only to the search for the infamous God particle.
08:09I think it's fair to say that the number of people that are involved, it's ridiculously hard.
08:14And it's really great work over many, many years.
08:17But to solve this problem, they'll need to shift the foundation of our entire measurement system.
08:30To understand why, requires a trip back to Paris.
08:44More specifically, to an intergovernmental organisation known as BIPM, or the International Bureau of Weights and Measures.
08:56BIPM, we are one of the oldest technical international organisations in the world.
09:03We're here in France, but we're not French.
09:09It's led by director Martin Milton, assisted by a team of staff, including Dr. Estefania de Miranda and Dr. Richard Davis.
09:28The BIPM uses its impartial status to act as an international guardian of metrology, ensuring measurements are consistent, accurate and fair for all.
09:43And they're the curators of a truly extraordinary achievement of mankind.
09:49A list, or rather a system, of definitions.
09:55It's a simple list, distilling all the essential properties of our world into just seven definitions of base standard units.
10:18It's because we share this system of units that it gets its power.
10:24It means we can compare things in all the countries on Earth easily, transparently.
10:33The metre, the second, the mole.
10:39These are the essential standards to which all our rulers, clocks, thermometers and scales can be calibrated.
10:49That provides the basis for all the types of measurement that one needs for science and society and for quality of life.
10:58I love the SI. I really love it.
11:01And the reason I love it is because it has humanity stamped all over it.
11:06Do you know how many languages are spoken on our planet? Do you have a feeling of that?
11:13300.
11:14300.
11:15No.
11:163000.
11:173000.
11:183000 different languages.
11:21And it is very complicated for one group of people to communicate with another group of people.
11:29And so, to have a universal language in measurement, that's a global story.
11:36And that's very, very beautiful.
11:43But there is a problem with the SI.
11:48One hidden in plain sight.
11:54The kilogram, a fundamental unit of the SI, is simply defined as the mass of a kilogram is equal to the mass of the international prototype of the kilogram.
12:10Mass is still tied to a single, a single artifact in the world, to a hunk of metal in Paris.
12:19The international prototype of the kilogram, or IPK, Le Grande Quai, the last artifact.
12:34The hunk of metal has many names, yet it is utterly unique and absolutely irreplaceable.
12:43It's an object that literally defines the weight of everything else in the world.
12:48Few ever get the chance to see something this priceless.
12:55Except, on a day like today.
13:00A small platinum iridium cylinder, standing only 39 millimeters tall, it's not a particularly impressive object to look at.
13:17You have all these belt jars, which surround it.
13:22So you see this little, little thing, just in a safe.
13:25From one side you are excited, and the other side, just a piece of metal.
13:28I mean, it's a strange thing. How do you get excited about a small piece of metal in that way? But it's what it stands for.
13:37Anything that you weigh from an apple in a grocery store to drugs at a pharmacy, eventually goes back to this prototype in Paris.
13:56And it's an elaborate system of traceability that we have to that, that enables us to get accurate weights for everything that we use and buy and sell in the world.
14:11Held in vaults across the world are hundreds of copies of the kilogram.
14:23None are exactly identical, but all are calibrated precisely against the original.
14:30So for example, if you stand on a scale, it will give you a weight, and you need to know if that weight is the right weight.
14:42So that scale has been calibrated against another scale, which in turn has been calibrated against another scale, and it runs all the way back.
14:53And the top scales will be calibrated against the kilogram.
14:59And that kilogram in turn is calibrated and measured against the IPK, kept in BIPM.
15:08Which is the kilogram, which is the standard that all standards are compared to.
15:15And this is the source of our weight-related problems.
15:22This is what the kilogram, the kilogram, the international prototype of the kilogram looks like.
15:27Now, I'm handling it with my hands.
15:31By definition, the mass of the international prototype kilogram is the definition of the kilogram.
15:36That means if you put a fingerprint on it, it's still the kilogram, and everything else in the universe has less mass.
15:43That's a ridiculous situation to be in.
15:49That's not the only issue.
15:52It's a man-made object, so an artifact.
15:55Everything that humans make as a standard decays.
16:00Everything, as soon as it's made, it's beginning to decay and change and evolve.
16:06Everything is decaying.
16:08Since it was forged, the IPK and its replicas have deviated from one another by about 50 micrograms.
16:19Or the mass of a single eyelash.
16:22Shifting the world's weight with them.
16:24We do not know whether the prototype, the artifact, is losing its weight or is accumulating its weight.
16:35There's a fundamental problem with having an artifact that defines the standard against which everything else in the world is compared.
16:42You want it to be isolated and kept separate, but as the source of all the weighings in the world. You want it to be used practically.
16:52In order to solve the problem of the world's shifting weight, there is only one solution.
17:02So, we're dumping the lump, we're changing the system.
17:06But, that's not as easy as it sounds.
17:11The kilogram is a fundamental, interlinked part of the SI units.
17:16Which means to redefine it, you have to redefine the SI.
17:23You have to change the way the world measures almost everything.
17:28I always feel like if humanity is going to change something, go big.
17:38To understand how we got into this situation in the first place, and how we can fix it, we should really start this story at the beginning.
17:50No, the beginning of civilization.
18:01Measuring is a really simple idea, and humans have been doing it since time immemorial.
18:08If we go back to antiquity, thousands of years ago, people measured things with stones and grains to make standards.
18:27These consistent measuring references revolutionized fair trade.
18:31And naturally, people gravitated towards standards everyone can access, that were also close at hand.
18:39Like a hand.
18:41Or an eye.
18:43Or arm.
18:45But these seemingly democratic standards have their own potential for short changing.
18:52If you measure a horse, you can measure it in hands.
18:55If you measure a horse, and I measure a horse, we're going to get a different size horse.
19:00So, many ancient rulers created empire-wide, stable standards of measures.
19:10So, for example, in ancient Egypt, the cubic was the length of measure.
19:14And that was the distance between the elbow and the tip, or sometimes between the elbow and the tip of the finger, plus a hand.
19:22But those guys realized this wasn't going to let them build the pyramids to the kind of accuracy that they needed to do.
19:29So they made a standard.
19:31Standardized artifact measures, like cubits, allow those in power to better build, govern, and tax their empires.
19:42Where you can compare something measured in one place with something measured at another time in another place.
19:50And then measurement becomes really, really powerful.
19:53But over centuries, these measurement standards multiplied, and massively muddled metrology through the creation of more and more units.
20:05Pounds, ounces.
20:06Piles.
20:07Charlemagne.
20:08Yard.
20:09Trois-voix-du-poix.
20:10Height.
20:11Elves.
20:12Miles.
20:13Feet.
20:14Corn.
20:15A shekel.
20:16The inch.
20:17By the 18th century, the list was so long that some traders were dealing with 800 different units of measurement.
20:23And a quarter of a million definitions for them, many of which weren't comparable.
20:32And these inequities stirred up some serious discontent among the masses.
20:41We know of the role that tea and taxes played in the American Revolution.
20:45But it could also be said that baguettes and bakers played a role in the French Revolution just a few years later.
20:54One of the very worst things that the revolutionaries were concerned about in revolutionary France, they were concerned about a lack of fairness with measurements.
21:07Bread was the main component of the French working class diet.
21:11The average 18th century worker spent half their hard-earned, er, dough on it.
21:19It was so important, the king controlled all aspects of bread production, including the price of loaves.
21:26With France in the middle of a historic famine, and different standard units of measure in each village, weights could be fiddled.
21:37So people were often paying the same for less, and the poor had no way to prove this was happening.
21:44The peasants were hangry and revolting.
21:47France was in turmoil.
21:50It began with the execution of the king, and ended with the accession of Napoleon.
21:59Obviously, the causes of the revolution were far more complicated than the price of bread.
22:05But it's fair to say it rather brought things to a head.
22:17When the revolutionaries took over, it was recognised that one of their priorities would be to put in place a measurement system that was going to be fair.
22:27On the 7th of April 1795, true to their word,
22:33At all times, to all peoples, the metric system was formally enshrined in French law.
22:42This idea of democratic approach to measurement, this wasn't tied to the length of the king's foot or something like that.
22:56Instead, they turned back to constants found in nature, but in a much more scientific and global way.
23:04They were going to use the earth itself.
23:08Anybody could access the circumference of the earth, and nobody could change the circumference of the earth.
23:15For example, a metre would be a fraction of the planet's circumference.
23:21But at the time, this proved too difficult to measure precisely and consistently.
23:26So they decided to create physical points of reference for these new units.
23:35They made artefacts.
23:41The original artefacts of the metric revolution are now locked away in the Archive Nationale.
23:47One of the first decisions of the National Assembly was to create first the matter and then the kilogram.
24:05They defined a new unit of mass that was the mass of a litre of water, and they called that the kilogram.
24:16And this is the first prototype of what we call the kilogram des archives.
24:25It was made at the end of the 18th century, fabricated in platinum.
24:34Under the French Revolution, citizens could be involved in the decision-making process of the unit.
24:42It's a kind of democracy.
24:44Among the things that people were thinking about was liberté, égalité, fraternité.
24:52And part of this was that the system of measurement should be something that should be accessible to everybody.
24:58And that has been the mass system that we've maintained for years, and it has served us well.
25:04So if it's not broken, why fix it?
25:10Well, apart from the possibilities of damage to, or theft of, an irreplaceable artefact,
25:17metrologists are thinking about the future.
25:20Redefinition allows us many things, two that come to mind.
25:25One is, we freeze any potential drift in the mass of this artefact.
25:31Then it allows us to go from the quantum level to the cosmic level without changing scales or units.
25:40Most science, and a lot of technology, is developed when we solve a measurement challenge.
25:48Having better access to better definitions and better measurement techniques
25:54actually propels the rest of society and its scientific progress forward.
25:58And that brings us to the next step, which is to replace the present definition of the kilogram
26:06with something that's not an object.
26:09Something that doesn't change with time, that doesn't get destroyed.
26:14Something that you can reproduce everywhere, anywhere in the world.
26:17We have faced this kind of situation repeatedly in metrology.
26:28It used to be that a second was 1 over 24 times 60 times 60 of a day.
26:33The trouble is, that by the early 20th century, it was clear that a day was not a constant thing.
26:42And that realization meant that we had to change the definition of time.
26:48And they did this by using what metrologists call fundamental constants.
26:53Fundamental constant does not change. It's a universal constant.
27:00Today, the definition of time is based on atomic standards.
27:04It's based on the unchanging frequencies of atoms.
27:08And like the second, fundamental constants have been used to redefine other units of the SI.
27:18Originally for the meter, it used to be a meter stick.
27:22Now it's based on the speed of light in a vacuum.
27:26It sounds like it isn't a profound change, but it actually is an incredibly profound change.
27:34This moves the reference for objective reality away from a man-made artifact
27:41and onto an unchanging constant of the universe.
27:45In the case of the kilogram, we're moving from an artifact to basically an equation.
27:53But unlike the speed of light, there's no obvious fundamental constant to redefine mass.
28:00Q2 obscure but promising contenders.
28:05One from chemistry, the other from physics.
28:09The teams representing each are tackling the same kilogram-sized problem.
28:15But a bit of friendly competition never hurts.
28:19It's very challenging, and then it's competitive too.
28:24There's national pride at stake.
28:25Everyone wants to be the lab that changes the face of the kilogram.
28:30One group set out to define the kilogram using the Avogadro constant.
28:35Of course there is competition. Of course there is the power that brings us further.
28:41The other using the Planck constant.
28:45One of the things that makes metrology unique is we rely on other people repeating our measurements.
28:49Rivalry in metrology is extremely useful.
28:53People will go out of their way to think of new ways of doing things.
28:58And some of them will survive, some of them won't.
29:01Both routes would push the team to the limits of what's possible.
29:06The first candidate is a fundamental constant from chemistry, the Avogadro constant.
29:19Named after the early 19th century Italian scientist Amadeo Avogadro.
29:26The Avogadro constant is currently defined by the SI as the number of atoms in one mole.
29:31No, not that kind of mole.
29:37The mole is a unit that describes the amount of substance that's equal to the number of atoms in 12 grams of carbon-12.
29:46This is currently calculated to be 602 sextillion, 214 quintillion, 85 quadrillion, 774 trillion atoms.
29:58To put that in perspective, that's 80,000 times more atoms than there are grains of sand in all the beaches, deserts and sandpits in the entire world.
30:12To further complicate things, those 12 grams are still defined by the IPK.
30:21So why then, posited scientists, can't we do the reverse?
30:27Use Avogadro's constant to define the kilogram.
30:30One of the teams tackling this is the Physikalisch-Technischer Bundesenstalt in Germany.
30:44The PTB is a very accurate, organized little machine. Not that little.
30:51Not that little.
30:54It's home to team members, including PhD student, Editha Beyer.
31:00Physicist and fossil hunter, Ingo Bush.
31:05And physicist, engineer and precision marksman, Arnold Nikolaus.
31:10They're working with the National Metrology Institute of Japan to build cutting-edge technology to crack this Avogadro endeavor.
31:22Here, team members, including prime senior researcher and pianist, Kenichi Fuji.
31:37Surface and nano-analysis group physicist and flower arranger, Lulu Zhang.
31:42Mass standards group leader and wakelifter, Naoke Kuramoto.
31:49Are led by director general and avid motorcyclist, Takashi Usuda.
32:01When I'm hearing, the great symphony encourages me to invent something new.
32:07Both teams are aiming to redefine the kilogram as an equation by measuring the value of Avogadro's constant more precisely and more accurately than ever before.
32:30And they custom make the perfect tools for the job.
32:33I'm working with the roundest object on the earth, which is made from the purest silicon on the earth.
32:44And machining them is no walk in the park.
32:50Mechanical engineer Rudolf Mies has spent years perfecting the process.
32:56In the first steps, we remove several grams per hour.
33:00But in the end, the removal rate is just one nanometer per minute and takes three months to produce a sphere.
33:10The result is an almost perfect sphere, of almost perfect purity, and a price tag of several millions of dollars per sphere.
33:23Luckily, for the Avogadro team, these spheres aren't irreplaceable artifacts like the IPK.
33:36Rather, they're just astoundingly accurate, if expensive, tools.
33:40The silicon sphere is much more than just a mass standard. It's a counting machine for atoms.
33:50New spheres can be made, but their perfection is priceless.
33:55It allows them to be measured to previously unfathomable precision, and determine the exact number of atoms inside each one.
34:04But there are so many atoms inside, that if you could count them at a speed of 10 million atoms per second, it would take you 68 billion years.
34:18Or about five times longer than the universe has existed.
34:21So, they use their spheres' remarkable shape and structure to calculate Avogadro's constant instead.
34:38Imagine we have a truck full of oranges.
34:43So, we measure the truck, that's the volume of the sphere.
34:48We measure the volume of an orange, that's the volume of the atom.
34:54And together with the information about the inside organization of the oranges, we know exactly how many oranges are inside,
35:03and we can determine our Avogadro constant.
35:08With their perfect spheres and meticulous measurement, the Avogadro project aren't pulling their punches.
35:15But there's another heavyweight contender competing in the kilogram redefinition ring.
35:21The Planck constant.
35:23Named after the German physicist who discovered it, Max Karl Ernst Ludwig Planck.
35:35It's a fundamental constant that even top metrologists have trouble summing up.
35:41If you go, well, let's see how I can do this.
35:45How would I, I mean, I gotta think about this a bit more, because that's a hard, hard question to explain what Planck's constant is.
35:51Oh, God, jeez.
35:53Did we want to try and describe what Planck's constant is?
35:57No, no.
36:01The actual constant may be hard to explain, but the concept is easy enough.
36:06In the late 1800s, physics was facing a crisis.
36:13Physicists were trying to model atomic vibrations, but they kept getting it wrong.
36:19They'd assumed that atomic vibrations were continuous.
36:23That is, they could vibrate at any frequency.
36:27Planck came up with a kind of a crazy idea.
36:30He said, it's not a continuous process.
36:33It's always in little packets of energy that today we call photons.
36:38Think of it like your morning coffee.
36:41When you order your Americano, you can add sugar in two different ways.
36:46As a continuous stream or as cubes.
36:49Planck postulated that you could only change energy in minimal increments, like sugar cubes.
37:00And the field of quantum mechanics was born.
37:05It was a surprise to everyone that energy was quantized.
37:11And it changed our understanding of physics entirely.
37:15And because Planck's constant relates to energy, you can link it to an object's mass via Einstein's relativity equation.
37:26Energy is equal to mass times the speed of light squared.
37:31Using Planck's constant to redefine the kilogram.
37:35But first, metrologists have to measure it.
37:44Doing the heavy lifting for the Planck constant are labs like the National Research Council in Canada.
37:56I spend a lot of hours, a lot of long, long hours.
38:00Physics runs on coffee for the most part.
38:01Team members including research officers in electrical measurements, Carlos Sanchez and Barry Wood.
38:11And dedicated dad and team leader in mass metrology, Richard Green.
38:17Are led by Canada's chief metrologist, Alan Steele.
38:22Intense, dedicated, you know, no fear of taking things apart and putting them back together over and over and over again until you get it right.
38:31The NRC are joined by yet another set of Planck pioneers.
38:41From the National Institute of Standards and Technology in the United States of America.
38:50Team members include chief of the quantum measurements division and strings drummer, John Pratt.
39:06It's certainly a common stereotype, but I feel like it's a little bit of truth.
39:14The U.S. tends to be a little bit more freewheeling on these types of things.
39:18Yeah, it's a great new idea. Let's go do that.
39:21Leader of the mass and force group and coffee aficionado, Zena Kubaric.
39:27Mass and force group physicist and technical tinkerer, Patrick Abbott.
39:34And fundamental electrical measurements group physicist and should be prize winning pretzel maker, Stefan Schlaminger.
39:42I think we are a very strong team. I think there's almost no technical problem that we can solve.
39:53To derive the most precise and accurate possible value of Planck's constant,
39:58both teams are measuring a readily available supply of calibrated kilograms in an electromagnetic device called a watt balance.
40:07The watt balance is simply a clever device that can weigh a mass using only electrical measurements.
40:18The watt balance basic principle is you're comparing a gravitational force to electromagnetic force.
40:28Think of it like an electromagnet in a scrapyard.
40:31Larger cars have a greater gravitational force pulling on them, making them heavier.
40:38So more electrical current is required to overcome gravity and lift a heavier car.
40:45Except instead of pulling an object upwards, the watt balance electromagnet pushes it up against the force of gravity
40:58until the electrical force equals the mass of the now balanced object without the need to compare it to anything on the other side of the scale.
41:09This gives the watt balance the ability to link electrical energy and its base unit, Planck's constant, to the mass of an object.
41:20But devising a device to measure the quantity of this force exactly required the genius of Dr. Brian Kibble,
41:33who cracked the engineering of the world's first watt balance at the National Physical Laboratory in the United Kingdom.
41:42This laboratory was where the watt balance was born. Brian Kibble and I built the first one here.
41:55Today the balance is also called the Kibble Balance in honour of its inventor.
42:00His legacy lives on through the work of the lab's many contributors, including electrical measurement specialist Ian Robinson and research scientist Purdy Williams.
42:15I don't think you could get a more British place than this crazy British lab.
42:20We have tea parties in the office and there's a grand piano.
42:24I described the basement lab as Ian's brain has just thrown up in a lab.
42:35Some of the most groundbreaking science is done in a messy, unorganised shed in the basement of a massive stately home.
42:46Whilst the NPL are no longer in the business of weighing kilos,
42:50they are leading the world in building affordable miniature Kibble balances for the masses.
42:57We're now in the lucky position of being able to build a generation of balance
43:02that should take the balance out and make it egalitarian.
43:06Everybody in the world should be able to access this technology and contribute to the world mass scale.
43:12And they're lending their expertise in watt balance building to a devilishly difficult task for good reason.
43:22Measuring the plank constant to the level that we need is extremely difficult.
43:26Working with the watt balance is, I would say, an emotional rollercoaster.
43:35Bring it down and let me look.
43:37And building this thing wasn't exhausting and kind of, oh my god, is it going to work, you know?
43:42Can you see here?
43:44The watt balance is a really, really hard experiment.
43:47These instruments tend to have a certain character to them that only the people who built them can really make them work the way that they're supposed to work.
43:58We need to consider about a hundred different effects that affect the measurement.
44:04From noise, temperature, magnetic fields, we need to measure all those things and to a level that we haven't been able to measure before.
44:11This is a big change we're proposing. We'd like to get it right.
44:20After years of painstaking trial and error, a decision has to be made about which fundamental constant would redefine the kilogram.
44:29In 2011, the metrological community decrees Planck and its ability to link all electrical units in the SI as their constant of choice.
44:43But there's a twist, which means that the work of the Avogadro teams can still contribute to the redefinition effort.
44:50The Avogadro constant and Planck's constant are very closely related to each other.
44:57If you have one of these two constants, you will get the second constant for free.
45:04And that's the way Planck's constant occurs in the silicon sphere.
45:11That's it.
45:13The challenge now becomes that the Planck values from both experiments must match.
45:20So if both projects result in the same numbers, then I think there is no doubt to redefine the kilogram.
45:30If they don't, then something has gone very wrong.
45:34Today is one of the most important meetings of the Consultative Committee for Mass.
45:49Today is the deadline for the teams to get their results in.
45:55Everybody is coming up with their answers at the very last minute.
45:58Candidates were just accepted about a week and a half ago.
46:00The German Avogadro number came about three or four days ago.
46:04The NMIJ one came out about two days ago.
46:07Just yesterday, I think it was, from the United States.
46:10Today they decide if the data is good enough to be put to the vote.
46:16The CCM put up some conditions which should be fulfilled in order to go for redefinition.
46:23We want to all have agreement on what the value for Planck's constant is.
46:26And a new value has come online, which is controversially or maybe possibly a little bit out.
46:33Some countries think that the criteria have been met, and others think they have not been met.
46:39And this is now an intense discussion, how we should proceed.
46:45If they cannot reach an agreement, the whole redefinition could be called off.
46:50For us, it would mean four more years of digging for uncertainties, and I don't think we can...
46:57I don't want to do that. I want to move on to other science.
47:00As the debate becomes more heated, it continues behind closed doors.
47:04One year ago, I would have said everything set for the redefinition.
47:09Now, in the recent times, I'm not certain if the current status of knowledge will be considered to be enough by the General Conference.
47:16But in the always exciting world of metrology, nothing is ever straightforward.
47:28The teams have been given just two months to publish values in closer alignment for Planck's constant,
47:34or risk putting next year's redefinition vote in jeopardy.
47:37Right now, we should be writing, and we're still not writing our article, instead we're still doing measurements.
47:43So I think it will be a close call. I think we have to pull a bunch of all-nighters to get it done.
47:48Once the papers are in, the Avogadro and Kibble balance teams will average their numbers
47:54to obtain the lowest possible uncertainty for the final fixed value of Planck's constant.
48:01Uncertainty is always sort of this measurement of how confident you are in that number.
48:05The worst thing a metrologist can do is have a number that turns out to be outside their uncertainties,
48:11and that's our idea of hell, I think.
48:16We still have some problems to solve, and I think the pressure is too big for the redefinition,
48:24and for the redesigning of the SI.
48:29I'm sympathetic to the Conservatives, but I'm also a US guy, and I'm just like,
48:34let's change.
48:39The final agreed numbers for Planck's constant roll in, fixing its value in the kilogram equation.
48:46There's nothing more the teams can do but wait.
48:50It's now up to the metrological community of the world to vote on whether their consensus value for Planck
48:57is good enough to redefine the kilogram.
49:09We're going to Versailles to go and watch the vote.
49:11We'd better redefine the kilogram. We've done too much work not to do it.
49:17Today's vote will determine whether the kilogram will become an equation using Planck's constant,
49:24or if it will remain an artefact.
49:26The fact we've got multiple experiments, multiple labs, means that we're pretty sure we've got the right answer.
49:33Well, not pretty sure, we've got the right answer.
49:35Now we're really getting close to a win-win-win situation, so nobody loses.
49:48So why would anybody want to delay?
49:52It's way past time to redefine.
49:54You don't want science to ever be limited by one particular artefact or one particular laboratory or one particular experiment.
50:06Now we're ready.
50:09I think it's time.
50:11Ladies and gentlemen, you have heard that the proposal for the revision of the SI is that it should be based on constants, on fundamental constants.
50:32Mr. President, I think we're ready to propose that.
50:36Each country will be called, and you will say yes or no.
50:41Canada.
50:42Same thing in French.
50:44Yes.
50:46Yes.
50:48Kenya.
50:50India.
50:52Japan.
50:53Japan.
50:55United States of America.
50:58Korea.
51:00Iran.
51:01China.
51:03Yes.
51:04Yes.
51:05Yes.
51:06Yes.
51:07Yes.
51:13The definition of the kilogram is free from the artefact.
51:20We've redefined the kilogram.
51:22The vote was unanimous.
51:24Thank you so much.
51:34To witness a historical moment like that and be a part of it, I know that this is something I will remember forever.
51:45It was the ride of my life.
51:56You know, it was a lot of fun.
52:02We measure planks constant, but what people really want to see are the tats.
52:06My tattoo in no way resembles my job role, but I have Keeper of the Kilogram tattooed on my back.
52:16The idea of the French that it would be a system of units for all people, for all times, I think we're really a lot closer to that now.
52:25You know, I'm just overwhelmed with the community that was built and come to consensus and make progress, real progress, for mankind.
52:41In a monumental metrological moment, a democratic equation anyone can access at any time takes its place as the definition of the kilogram.
53:04While metrologists get back to work, the rest of the world continues unaware.
53:18Okay, so what's going to change when we change the kilogram?
53:22How is that going to affect the average person?
53:27When the kilogram is new defined and when we do a good job, no one will notice it.
53:32But that's good.
53:37When the person on the street will start seeing differences is when new technologies start getting built into better science or better products.
53:45I think that might happen in individualized medicine or cellular medicine or pharmaceuticals.
53:52The better we get at measuring something, the bigger the world of opportunity for scientific exploration becomes.
53:59There's a new undiscovered land. You know, we have wiped out all the maps and say, okay, something completely new.
54:09Some people think metrology is dull.
54:20They think it's some kind of accountancy.
54:22That completely misses the point.
54:24Metrology is looking closer and closer at things, seeing their form more perfectly, seeing them more clearly in themselves.
54:33And just appreciating the full wonder and beauty of the world we have around us.
54:43So, La Grande Cave isn't really going away.
54:44It's going to be in that vault, but it's still going to be with us because it's mass.
54:45At the time of redefinition.
54:47It's going to be in that vault, but it's still going to be with us because it's mass at the time of redefinition.
54:48It's essentially built into the Planck Street.
54:51It's going to be in that vault, but it's still going to be with us because it's mass at the time of redefinition.
54:53It's essentially built into the Planck's constant.
54:54It's immortalized, if you will.
54:56The Planck Street is a state of the Planck Street.
55:01So, La Grande Cave isn't really going away.
55:05It's going to be in that vault, but it's still going to be with us because it's mass at the time of redefinition.
55:15It's essentially built into the Planck's constant.
55:19It's immortalized, if you will.
55:20if you will I feel quite weirdly protective over a lump of metal and I
55:33mean if they do want to get rid of it one way I'm happy to take it home and look
55:37after it
56:07I'm happy to take it home and look forward to it
Sé la primera persona en añadir un comentario