1 00:00:00,720 --> 00:00:05,520 Okay. Thank you for coming, everybody. I'm Richard on the East Coast, director of this week's module. 2 00:00:06,000 --> 00:00:10,890 And as part of the week we've organised a seminar and delighted to introduce Dr. Martin Saini, 3 00:00:11,280 --> 00:00:14,790 Deputy Chief Executive of the National Physics Laboratory. 4 00:00:15,240 --> 00:00:22,380 And I think his talk will make clear why I was so keen that somebody from a physics laboratory should come and talk on a medical science program. 5 00:00:23,560 --> 00:00:35,700 Okay. So yes, thanks for the introduction and what I'm going to try and do in the next three quarters of an hour or so is three things. 6 00:00:35,730 --> 00:00:42,360 One, I want to give you some idea about why having trusted measurements is quite so important. 7 00:00:42,990 --> 00:00:46,799 The second thing is I want to tell you about how it is, what it is, what, 8 00:00:46,800 --> 00:00:52,800 what exist globally to ensure that we can all have confidence in the measurements that we make or the measurements get made on our behalf. 9 00:00:53,370 --> 00:00:58,049 And the third thing I want to do is to explain to you why 2019 is possibly 10 00:00:58,050 --> 00:01:03,480 the most exciting year in the science of measurement for at least 140 years, 11 00:01:03,480 --> 00:01:09,900 and potentially is the culmination of a project that started in 1791 during the French Revolution. 12 00:01:10,590 --> 00:01:14,400 So measurement is something that we probably all take for granted. 13 00:01:14,440 --> 00:01:21,560 It's something that has been part of human society for at least 5000 years. 14 00:01:22,380 --> 00:01:28,770 Almost certainly what happened was that soon as humans started to interact outside their family groups or their very local groups, 15 00:01:29,100 --> 00:01:34,379 they realised they needed to have some means of exchange for two reasons. 16 00:01:34,380 --> 00:01:39,360 Firstly, for trade and this is some of the earliest archaeological evidence for measurement. 17 00:01:39,360 --> 00:01:44,760 These are church weights that come from the Indus Valley somewhere between two and a half thousand and 3000 BCE. 18 00:01:45,510 --> 00:01:53,430 And they are an illustration of people's obsession with ensuring their very accurate obsession with ensuring that trade was fair, 19 00:01:53,460 --> 00:01:55,110 that you got what you paid for. 20 00:01:55,500 --> 00:02:02,900 The second thing that people probably needed to have measurements for very early on was construction building projects. 21 00:02:02,910 --> 00:02:06,570 Again, as soon as those projects went outside of the local family group. 22 00:02:06,750 --> 00:02:13,320 This is probably the most obvious example of that. The pyramids are a remarkable feat of of construction. 23 00:02:14,190 --> 00:02:21,210 And the way that it worked was the work was distributed by very through a very large number of groups of masons. 24 00:02:21,810 --> 00:02:29,370 Each of those masons had a wooden standard, which was a copy of one of these. 25 00:02:29,370 --> 00:02:33,270 This is a copy. This is a reproduction of the Egyptian cubit. 26 00:02:33,750 --> 00:02:37,800 It was the distance between here and the fingertips of the pharaoh. 27 00:02:37,950 --> 00:02:41,610 I will pass this around to see if I don't. I don't match up to a ferret. 28 00:02:43,080 --> 00:02:45,810 But if you want to pass this around, you can see if you match up to a fairer. 29 00:02:46,080 --> 00:02:57,540 And in order to ensure in order to ensure that these all to ensure that this consistent measurement was used and was being maintained, 30 00:02:58,290 --> 00:03:07,860 every full moon, the heads of the different mason yards had to return and compare their standard to the Master Cubit. 31 00:03:08,340 --> 00:03:15,660 Failure to do so was punishable by death. They took consistent measurement pretty seriously. 32 00:03:16,440 --> 00:03:26,430 Congratulations in in the UK, one of the first places that you have real documented evidence of how important measurement is, 33 00:03:26,580 --> 00:03:29,399 is this document Magna Carta 1215. 34 00:03:29,400 --> 00:03:35,969 In the English speaking world, it's looked back to as one of the documents that the roots of the freedoms that we have. 35 00:03:35,970 --> 00:03:39,420 So in here comes the first habeas corpus. 36 00:03:39,660 --> 00:03:45,420 In here comes a real requirement of people to be trialled by their peers, a whole host of freedoms. 37 00:03:45,420 --> 00:03:49,740 But about two thirds of the way down somewhere down here are these words. 38 00:03:50,460 --> 00:03:53,550 I have to realise that just as important as other things, 39 00:03:54,090 --> 00:04:01,560 having consistent measurement and having confidence in the measurements that being made was important for the functioning of a society. 40 00:04:01,740 --> 00:04:08,590 And I also like and I also think it's interesting that the priorities are wide I'll 41 00:04:09,000 --> 00:04:18,150 and corn and some things don't change today measurement is part of everyday life. 42 00:04:18,450 --> 00:04:23,370 There's lots of pictures up here where we come across measurement and probably take it for granted. 43 00:04:23,850 --> 00:04:27,210 Sometimes we wish it wasn't quite as accurate as it could be on the scales. 44 00:04:28,320 --> 00:04:32,040 Does anybody know who the lady in the top is? Top in the middle there? 45 00:04:32,060 --> 00:04:36,000 I didn't know that lady. Ellie Simmons. 46 00:04:36,000 --> 00:04:48,690 Absolutely right. That's Ellie Simmons. And in 2016 at she in the Paralympics she got a world record for the 200 metre Im six swimming and that 47 00:04:48,690 --> 00:04:59,610 was 2 minutes 59.8 1 seconds now for her and for her competitors and the predecessors and the successes. 48 00:05:00,170 --> 00:05:12,020 In Olympics, it is important that it really was 2.50 9.81 and 2 minutes, 59.8 1 seconds, so that a world record at 2 minutes, 49 00:05:12,020 --> 00:05:20,090 59.80 will be absolutely confidently achieved if that happens in the next time we have these Olympics. 50 00:05:20,930 --> 00:05:26,120 So those are examples where it's pretty obvious that we are involved in a measurement and we're taking a 51 00:05:26,120 --> 00:05:33,680 measurement and it's and we can see how important it is to our lives and the lives of individuals and and so on. 52 00:05:34,430 --> 00:05:42,350 But most of the time, the measurements that are going on around us in our developed society are probably completely hidden. 53 00:05:42,530 --> 00:05:47,510 There's an enormous iceberg of measurements on which we all depend. 54 00:05:47,750 --> 00:05:56,450 Every single day, 3600 billion cubic metres of gas is traded annually was 2017. 55 00:05:56,450 --> 00:06:02,390 That was the figure. 3600 billion cubic metres of gas was traded across the world in 2017. 56 00:06:03,320 --> 00:06:07,700 It's traded not on volume, it's traded on calorific value, 57 00:06:07,700 --> 00:06:13,670 which is a combination of accurate measurement of volume and accurate measurement of the constituents of the gas. 58 00:06:14,030 --> 00:06:18,530 And over the last 25 or 30 years, there have been an enormous amount of very detailed, 59 00:06:18,530 --> 00:06:25,190 very complex, very technical, very scientific research done to help have the standards. 60 00:06:25,610 --> 00:06:30,200 So you can do calorific value with all the different constituents of gas from across the 61 00:06:30,200 --> 00:06:34,970 world at the accuracy you need for trade so that it's completely transparent to us. 62 00:06:36,470 --> 00:06:41,050 Similarly, building construction. This is a Rolls-Royce, Trent 1000 engine. 63 00:06:41,060 --> 00:06:49,340 It has 18,000 components. The 18,000 components come from across the world when they arrive either at Derby in the UK or Singapore, 64 00:06:49,340 --> 00:06:54,290 whether they have assembly plants, these and all those different parts have to fit. 65 00:06:54,290 --> 00:06:59,389 They have to be the right size. They have to be the right shape. They have to have the right materials properties. 66 00:06:59,390 --> 00:07:04,400 They have the right electrical properties. And that doesn't happen by accident. 67 00:07:04,580 --> 00:07:11,270 It is amazing and something that we take for granted that global manufacturing can do this kind of thing across the world. 68 00:07:11,390 --> 00:07:16,010 The other thing about these engines is that Rolls-Royce no longer sell engines. 69 00:07:16,520 --> 00:07:21,409 Rolls-Royce sell power by the hour. So you buy power from the engine. 70 00:07:21,410 --> 00:07:30,739 So when the engine is on, the amount of power you generate is what Rolls-Royce build the aircraft companies for literally thousands of measurements, 71 00:07:30,740 --> 00:07:36,950 a second being taken from this engine. And they are all either downstream immediately or more likely download it when it 72 00:07:36,950 --> 00:07:43,070 lands back to the Rolls-Royce company so that they can do their both billing. 73 00:07:43,520 --> 00:07:51,080 But all the diagnostics on how the engine is performing. We take weather forecasting for granted. 74 00:07:51,680 --> 00:07:55,850 Interestingly, we make a lot of fun of it. The UK Met Office is either number one or number two. 75 00:07:55,850 --> 00:08:01,840 Whenever this any assessment is done in the most accurate forecasting organisations in the world. 76 00:08:02,120 --> 00:08:10,609 The Rolls-Royce, the the Met Office has its headquarters in Exeter and it has two of the largest supercomputers in the company, 77 00:08:10,610 --> 00:08:16,660 has two just in case one breaks down and they both run in parallel four times a day. 78 00:08:16,880 --> 00:08:19,910 A global atmospheric model in order to predict the weather. 79 00:08:20,150 --> 00:08:27,950 That global atmospheric model sucks in 125 million measurements every day from across the globe. 80 00:08:28,940 --> 00:08:30,889 Those measurements have to be consistent. 81 00:08:30,890 --> 00:08:38,360 So one degree in Sydney, one millibars in Toronto has to be the same as one degree in Slough, one millibars in Paris. 82 00:08:38,690 --> 00:08:42,440 Without that consistency, a quite a high accuracy with confidence. 83 00:08:42,770 --> 00:08:46,460 Then the global atmospheric model would just turn out gibberish. 84 00:08:49,100 --> 00:08:53,390 We all take this for granted. We all have satnav in our pocket. 85 00:08:53,720 --> 00:08:59,360 If I bet that most of you us are pretty certain just about everybody has sat nav in their pocket. 86 00:09:00,830 --> 00:09:09,650 Again, something we take for granted that wherever you are in the world, you can find out your position to within a few metres to tens of metres. 87 00:09:11,180 --> 00:09:15,739 That is possible because orbiting the earth are at least 24 satellites. 88 00:09:15,740 --> 00:09:22,340 I think there's 26 at the moment. There has to be at least 24 satellites in the global positioning system constellation. 89 00:09:23,240 --> 00:09:26,840 Those satellites each have on them an atomic clock. 90 00:09:27,620 --> 00:09:32,269 That clock is accurate and synchronised with the others. 91 00:09:32,270 --> 00:09:40,310 Two within 100 nanoseconds, 100,000,000,000th of a second of the global, the universal, coordinated time for the globe. 92 00:09:40,640 --> 00:09:50,090 That is an astonishing feat of measurement on which we all depend when we open up our phones and we take it for granted. 93 00:09:53,650 --> 00:10:02,110 This is the of the table in a radiotherapy clinic in the UK, 330,000 people a year are diagnosed with cancer. 94 00:10:02,320 --> 00:10:08,710 Approximately half of them will have radiotherapy. And if you from a medical background, you'll know better than I. 95 00:10:09,190 --> 00:10:12,240 Radiotherapy in concept is very simple. 96 00:10:12,250 --> 00:10:19,209 You deliver enough dose to the tumour to kill it without delivering too much 97 00:10:19,210 --> 00:10:22,540 dose to the surrounding tissue and compromising the health of the patient. 98 00:10:23,290 --> 00:10:30,550 It is the most demanding application for measurement of ionising radiation. 99 00:10:31,180 --> 00:10:44,650 You need to be able to measure and deliver in the patient on the table in the clinic every time, ideally to within about 3% of your target dose. 100 00:10:45,010 --> 00:10:49,450 That is an astonishingly challenging measurement to have to do. 101 00:10:50,620 --> 00:10:56,680 But I can tell you that if you or anybody you know is ever unfortunate enough to lie on a table like this in the UK, 102 00:10:56,740 --> 00:11:02,050 the dose in the UK is delivered more accurately and more consistently than anywhere else in the world. 103 00:11:02,350 --> 00:11:10,329 And that's the result of about 30 people who work at my institution and their predecessors who have been working with medical physicists, 104 00:11:10,330 --> 00:11:19,210 equipment manufacturers, professional bodies to put in place the infrastructure to ensure that people's lives get saved every single day. 105 00:11:19,220 --> 00:11:25,780 So just a few examples of the fact that beneath the surface of our everyday life, 106 00:11:26,470 --> 00:11:31,240 our economy, our quality of life and in situations like this are very lives, 107 00:11:31,240 --> 00:11:37,570 depend on confidence in measurement that either we make or more often than not is made on our behalf. 108 00:11:38,230 --> 00:11:42,370 So how is that confidence assured? 109 00:11:43,660 --> 00:11:52,270 Well, in 1791, the French Revolution was just underway starting in 1789. 110 00:11:52,270 --> 00:11:59,770 In 1789, there were it was the start of about 100 years, almost 100 years of turmoil in France. 111 00:12:00,760 --> 00:12:07,270 At least two monarchies were deposed, one dictator in the middle, an incredible amount of turmoil. 112 00:12:08,350 --> 00:12:13,690 And this picture, which the famous picture painted by Dell'acqua in the middle of that to celebrate 113 00:12:13,690 --> 00:12:20,079 the the bringing down of Charles the 10th called liberty leading the people. 114 00:12:20,080 --> 00:12:29,600 And in France this is seen as one of the pictures that kind of really summarises and is an icon of that turbulent time of the history. 115 00:12:30,100 --> 00:12:35,139 But at the beginning of that, in 1791, these people, a group of people, 116 00:12:35,140 --> 00:12:39,970 including these two famous mathematicians whose names you've probably come across if you've got a mathematical background, 117 00:12:40,510 --> 00:12:47,760 wrote a paper to the French Academy of Science, and I would leave you for 15 or 20 seconds to read what they said. 118 00:13:00,480 --> 00:13:03,460 Their vision was that you could set up. 119 00:13:04,920 --> 00:13:16,950 They talked only about length here, but they were trying to set up a system of measurement that was for all time and for all people. 120 00:13:19,170 --> 00:13:25,680 I suspect that the somewhat turbulent times that went on between then and the 1870 121 00:13:26,610 --> 00:13:31,410 was one of the reasons that starting to really do something about this was delayed. 122 00:13:31,800 --> 00:13:42,300 But in 1875, 17 nations signed the metre, the Treaty of the Metre Convention. 123 00:13:43,620 --> 00:13:54,090 This is the UK copy. Interestingly, the UK didn't sign in 1875 because the UK was very, very suspicious of European projects. 124 00:13:57,960 --> 00:14:10,980 We signed in 1879 and this set up a framework, the international measurement system, which has continued to evolve since then when it was set up. 125 00:14:11,940 --> 00:14:23,340 They, the French, offered some headquarters for this international measurement system, and they offered it very, very generously in Paris. 126 00:14:23,880 --> 00:14:33,570 And the international community who had signed this said they would contribute to making this this this headquarters fit for purpose. 127 00:14:35,040 --> 00:14:39,030 So this was the building that the French offered to the international community. 128 00:14:39,810 --> 00:14:46,230 It was in a little bit of an I suspect to the international community, was a bit shocked about quite how much they had to spend. 129 00:14:46,740 --> 00:14:49,760 This is what it looks like today. It's on the outskirts of Paris. 130 00:14:49,770 --> 00:14:54,060 It has several servers, probably more famous for its porcelain than it is for measurement, 131 00:14:54,150 --> 00:14:58,110 but it overlooks a server, a factory, server, porcelain factory. 132 00:14:58,110 --> 00:15:01,139 And it's the Bureau Internationale de Marzio, 133 00:15:01,140 --> 00:15:09,840 and it's the headquarters of probably the single largest science and technology cooperative activity on the planet. 134 00:15:11,040 --> 00:15:18,660 So this is how we ensure that there is some confidence in measurements that we make or get made on our behalf. 135 00:15:19,410 --> 00:15:24,690 If you want to make a measurement, if you're a business or government and society and you want to make a measurement in which you can have confidence, 136 00:15:24,870 --> 00:15:28,260 there are three or four things that you need. You need to calibrate an instrument. 137 00:15:29,610 --> 00:15:32,990 Unless it's trivial, you need an agreed procedure. How are you going to make the measurement? 138 00:15:33,000 --> 00:15:37,709 And again, unless it's trivial, you need a trained practitioner about making that measurement. 139 00:15:37,710 --> 00:15:40,830 And if it has any regulatory component to it, you need a fourth thing. 140 00:15:40,830 --> 00:15:49,560 You probably need some kind of verification or accreditation. There are two fundamental concepts that enable that to happen. 141 00:15:49,710 --> 00:15:57,300 The first is called traceability, and that is an unbroken chain of calibration from the measurement that's being 142 00:15:57,300 --> 00:16:03,510 made back to special institutes in the in the members of the data convention, 143 00:16:04,290 --> 00:16:06,359 national metrology institutes and images. 144 00:16:06,360 --> 00:16:17,249 And in the UK, NPL where I work is the National Metrology Institute for the UK and we are that top of that chain for most measurements, 145 00:16:17,250 --> 00:16:25,170 certainly all physical measurements. There is an organisation called LGC who are the top of the chain for chemistry measurements designated for them. 146 00:16:25,380 --> 00:16:28,650 And there's an organisation in Scotland who at the top of the chain for flow measurements, 147 00:16:28,650 --> 00:16:35,729 but to a large part that one organisation, the enemy responsible for this. 148 00:16:35,730 --> 00:16:37,680 Now these chains can be quite long. 149 00:16:37,980 --> 00:16:44,760 If you take a ruler and you measure the width of an alcove in your house so that you can order a couple of the internet and be sure it fits. 150 00:16:45,000 --> 00:16:51,360 There's probably half a dozen steps between your ruler and the National Metrology Institute, 151 00:16:52,410 --> 00:16:58,620 but if you lie on that table in a radiotherapy clinic, there's nobody between you and NPL. 152 00:16:58,650 --> 00:16:59,940 We collaborate directly. 153 00:16:59,940 --> 00:17:05,849 We interact directly, partly because there's not much difference between the uncertainty that we can get and the uncertainty they need. 154 00:17:05,850 --> 00:17:13,920 And partly because it's absolutely life critical and the thing that sits at the top of the chain on national or primary standards, 155 00:17:14,160 --> 00:17:24,930 they are realisations, they are artefacts or ways of realising the measurement at a national level or at an 156 00:17:24,930 --> 00:17:32,610 international level that are demonstrated to be at the highest and highest accuracy. 157 00:17:32,700 --> 00:17:39,570 Now, how do you the second concept is called equivalence, and that's coordinated by the headquarters of the international measurement system. 158 00:17:40,140 --> 00:17:43,680 And it's the domain solely of these national metrology institutes. 159 00:17:43,800 --> 00:17:48,090 It's a complex set of calibrations and checking of quality systems, 160 00:17:48,300 --> 00:17:57,000 of comparisons to demonstrate that the top of the chain in each of these countries is comparable equivalent within the uncertainties of the. 161 00:17:57,110 --> 00:18:02,870 Quote, some countries, quote, higher uncertainties than others. But the uncertainties have to be able to be demonstrated. 162 00:18:03,080 --> 00:18:10,549 The measurements have to be equivalent within the uncertainties. I said these are complex, these comparisons because of the checking, 163 00:18:10,550 --> 00:18:13,580 because of the importance, because of the complexity, because they are done at the most. 164 00:18:13,580 --> 00:18:20,000 The highest level of measurement can take years, sometimes a decade, to complete and demonstrate that that is the fact. 165 00:18:20,210 --> 00:18:25,280 And so there's constantly a rolling cycle of these measurements across the whole of the system. 166 00:18:26,240 --> 00:18:29,810 And above that, there is the general conference of the meta convention, 167 00:18:29,990 --> 00:18:34,700 which is the the meet the conference that happens every four years and is when all of the member 168 00:18:34,700 --> 00:18:40,010 states to get together to make significant decisions about the global measurement system. 169 00:18:40,190 --> 00:18:41,360 Between the conference, 170 00:18:41,360 --> 00:18:48,589 they delegate the running of the global measurement system to the International Committee of Weights and Measures Caps Committee, 171 00:18:48,590 --> 00:18:50,750 International Diplomas Year in French. 172 00:18:51,110 --> 00:18:59,089 And that's 18 people who are responsible for operating and overseeing the global measurement system between conferences. 173 00:18:59,090 --> 00:19:02,300 And I'm privileged to be one of the people sitting on that committee. 174 00:19:02,690 --> 00:19:09,950 Now, if there were no new activities that humans undertook, 175 00:19:09,950 --> 00:19:14,209 if there was never any new science and technology, if there were never any new global challenges, 176 00:19:14,210 --> 00:19:23,570 this system could be set up and it would run like clockwork, and national laboratories would just be engaged in this. 177 00:19:23,570 --> 00:19:28,660 And indeed, there's a large percentage of the national laboratories, 178 00:19:28,670 --> 00:19:33,829 national metrology institutes in the world who just do this for their nation, particularly in the emerging nations. 179 00:19:33,830 --> 00:19:38,150 Nothing else. But there are new challenges. 180 00:19:38,600 --> 00:19:41,720 There are new activities. There are new problems. 181 00:19:42,500 --> 00:19:49,010 There's new science and technology. So the most advanced national metrology institutes of which I'm pleased one. 182 00:19:49,430 --> 00:19:53,750 Work with academia and business to futureproof the system. To put in place new science, 183 00:19:54,080 --> 00:20:03,500 new technology to verify data and to have world leading facilities so that as science and technology and global challenges appear, 184 00:20:03,830 --> 00:20:07,520 the measurement system is there, ready to assist. 185 00:20:10,640 --> 00:20:22,380 And at the heart of this whole system is the set of base units, the set of units that enable you to have consistent measurement around the world. 186 00:20:22,400 --> 00:20:28,180 There are seven of those. The number increased slowly over a period of time. 187 00:20:28,190 --> 00:20:33,049 But since 1971, there have been seven kg, the unit of mass mater, the unit length. 188 00:20:33,050 --> 00:20:43,190 Second, the unit of time and per unit of current. Okay, the unit count kelvin the unit of temperature mole, the unit of quantity of matter, 189 00:20:43,550 --> 00:20:51,860 and Candela about which I will say very little in this because it's a very, very curious unit that is solely related to human perception of light. 190 00:20:53,030 --> 00:21:00,739 However, these are the units and all measurements within the system can be expressed in combinations of those. 191 00:21:00,740 --> 00:21:04,010 So we will probably be familiar with velocity metres per second. 192 00:21:04,280 --> 00:21:12,200 Energy, which has a special note in the joule is actually kilogram metre, second metre squared second to the most to resistance. 193 00:21:12,200 --> 00:21:15,740 The ohm is kilogram metre squared, section two minus three up to minus two. 194 00:21:15,950 --> 00:21:25,670 And for those who are chemists, Catholic activity, concentration, whatever that is, kettles per cubic metre is this mile per second per cubic metre. 195 00:21:26,510 --> 00:21:31,790 So those enable you that, that framework enables you to have a way of measuring everything. 196 00:21:31,790 --> 00:21:37,729 And the PSI is incredibly successful. There are 60 member states of the convention. 197 00:21:37,730 --> 00:21:40,250 There are 42 associate members of the metre convention. 198 00:21:40,460 --> 00:21:46,790 And then through regional organisations, the the different regional organisations you can see on this picture, 199 00:21:47,090 --> 00:21:52,970 there are other nations who are aspiring to be part of the metre convention who are engaged at a regional level as well. 200 00:21:53,780 --> 00:22:00,620 So 98 point something percent of GDP of the global GDP is encompassed for the PSI system. 201 00:22:00,620 --> 00:22:03,799 So it is an incredibly successful system. 202 00:22:03,800 --> 00:22:12,530 It's very nearly utterly lipophilic for all people, but it's a bit messy. 203 00:22:14,600 --> 00:22:18,079 We don't really need all those units if you really if you just wanted to measure anything, 204 00:22:18,080 --> 00:22:24,170 if you are a mathematician or a physicist and you were saying, we really don't need all of these, what's the minimum number of units we need? 205 00:22:24,920 --> 00:22:29,749 We there are three and we really don't need the Candela is how bright the lights appear to humans. 206 00:22:29,750 --> 00:22:30,830 That's what it's measuring. 207 00:22:31,070 --> 00:22:37,639 It's a unit based on human perception, and it's basically defined at one wavelength of like near the sensitivity of the eye. 208 00:22:37,640 --> 00:22:46,070 And it's just a conversion factor from a measured measurement of light intensity per the radiant 209 00:22:46,850 --> 00:22:53,660 to how it appears to the human eye in terms of how candles appeared in Victorian times. 210 00:22:55,430 --> 00:23:01,700 It's a very strange unit. It's really important for the lighting in the health and safety industry, but it is a strange unit. 211 00:23:02,120 --> 00:23:05,030 The mole basically links chemistry to the PSI. 212 00:23:05,270 --> 00:23:11,090 It's the number of it's an avogadro number of elementary entities and it's the number of atoms in 12 grams of carbon 12. 213 00:23:11,450 --> 00:23:16,549 It basically links what's going on atomic scale to what's going on in a macroscopic scale. 214 00:23:16,550 --> 00:23:24,230 It's incredibly useful and it's absolutely embedded in the whole of chemistry and increasingly in biology, but in principle, you don't need it. 215 00:23:25,460 --> 00:23:28,520 And finally, Kelvin, temperature is a fascinating measurement. 216 00:23:29,330 --> 00:23:38,150 Temperature was measured before anybody really knew what it was, as temperature is actually the average energy of molecules, 217 00:23:38,540 --> 00:23:42,950 the average molecular energy of the molecules interacted in an object. 218 00:23:43,820 --> 00:23:54,500 And so you you can measure average energy, but because temperature is something again that you want to have macroscopic, 219 00:23:54,620 --> 00:24:00,199 this is a way of linking a macroscopic measurement down to a microscopic activity. 220 00:24:00,200 --> 00:24:05,990 The energy of molecules and the scale is set at the moment by one point, the triple point of water, 221 00:24:06,650 --> 00:24:13,100 which is just defined as 273.16 Kelvin and the whole of the scale bootstraps off of that. 222 00:24:13,100 --> 00:24:19,850 So it's a bit messy. However, it's completely impractical to abolish those unnecessary units. 223 00:24:19,850 --> 00:24:26,600 They are all embedded. The whole of global manufacture, global trade, science, technology, 224 00:24:27,260 --> 00:24:31,850 everything has these things so embedded in them that it's impractical to get rid of them. 225 00:24:32,330 --> 00:24:35,570 More serious problem is that some different. 226 00:24:35,580 --> 00:24:39,600 Missions explicitly limit how you can realise a primary standard. 227 00:24:39,600 --> 00:24:44,129 Those things that sit at the top of the chain and are the absolutely most accurate way that you could 228 00:24:44,130 --> 00:24:51,180 move with measurements below which all the other measurements are flow from them and are less certain. 229 00:24:52,260 --> 00:24:57,660 Some definitions limit how you can realise a primary standard the most accurate measurements. 230 00:24:58,290 --> 00:25:04,440 And one definition is an artefact. And I'll tell you why that's a real problem at the moment. 231 00:25:05,580 --> 00:25:11,940 But these things, one or both of those create an absolute limit to reducing the uncertainty of measurement. 232 00:25:12,300 --> 00:25:15,720 So that can limit the applications of science and technology and trade. 233 00:25:15,960 --> 00:25:24,090 We can find that these limitations on measurement are actually a barrier to science moving forward or technology moving forward, 234 00:25:24,540 --> 00:25:27,600 or people being able to address global challenges. 235 00:25:27,960 --> 00:25:35,310 So a little bit about that more in a moment. So the kilogram is one artefact left, 236 00:25:35,310 --> 00:25:43,440 and it illustrates both of these things about both about the problem with an artefact and the problem of you can only define it in one particular way. 237 00:25:43,650 --> 00:25:46,830 This is the definition of the kilogram and this is it. 238 00:25:50,400 --> 00:25:54,090 This is how big it can't get a sense of scale. So I brought one that's not a real kilogram. 239 00:25:54,330 --> 00:25:57,809 So because they're made of platinum, iridium, so it's a stainless steel plank. 240 00:25:57,810 --> 00:25:59,730 But if that's to give you an idea of the size. 241 00:26:00,720 --> 00:26:06,480 And certainly nobody would let me loose with anything that's even close to one of the copies of the copies of the kilogram. 242 00:26:07,890 --> 00:26:13,950 But this is the master KG. It's it's held at the headquarters of the International Measurement System in Paris. 243 00:26:14,910 --> 00:26:22,290 It's in a safe in a vault in the basement of a building. 244 00:26:22,650 --> 00:26:31,380 And at least once a year, there's a very strange ritual where the president of the committee, the international committee UPM, 245 00:26:31,770 --> 00:26:42,419 the rector of the laboratory by PM and somebody from the French Academy of Science bring their three independent keys and they open the this, 246 00:26:42,420 --> 00:26:50,100 they open the basement, they open the vault and they open the safe, and they confirm that the kilogram is being kept. 247 00:26:50,820 --> 00:26:56,310 And last year I was at this it's a it's a very interesting table. 248 00:26:56,580 --> 00:27:03,299 So I saw the kilogram sitting in. There also are these six, which were six copies made very early. 249 00:27:03,300 --> 00:27:09,180 And they're the ones that get used. The kilogram gets used maybe once every ten years because it is the definition of the kilogram. 250 00:27:09,480 --> 00:27:12,870 So if it gets scratched, we all weigh more. 251 00:27:15,680 --> 00:27:20,910 That's. And the other problem with artefacts is they're not for all time. 252 00:27:21,480 --> 00:27:23,460 So this is an interesting graph. 253 00:27:24,030 --> 00:27:34,439 This is 1889 when the kilogram was created with a kilogram and there were some copies made that in 1946, a couple of other copies were made. 254 00:27:34,440 --> 00:27:41,580 So there are now these official copies one, two, three, four, five, six, and they are regularly into compared. 255 00:27:42,990 --> 00:27:49,440 And so because the kilogram is the definition of the kilogram, it's always right. 256 00:27:50,760 --> 00:27:54,690 So this is how far over a period of time in 2014 was the last time it was done. 257 00:27:54,870 --> 00:28:04,980 You can see. So they've drifted apart by around 60, just over 60 micrograms now because the kilogram has to be right. 258 00:28:05,130 --> 00:28:11,610 It's got a be. But so all these things really for all time there's a that's a problem about artefact 259 00:28:11,610 --> 00:28:16,080 even one that's kept and controlled and looked after in the way that the kilogram is. 260 00:28:16,920 --> 00:28:20,310 The second problem is those traceability chains that I talked about, 261 00:28:20,610 --> 00:28:28,800 the fact that you have to have an unbroken chain of calibration from a primary standard in order for something to have confidence in the measurement. 262 00:28:30,630 --> 00:28:38,970 If the only definition of the kilogram is a particular artefact, that chain, every single chain has to start ultimately with that. 263 00:28:39,150 --> 00:28:44,210 And every time you make a comparison, you add uncertainty to your measurement. 264 00:28:44,220 --> 00:28:50,220 So even here where you are comparing the copies to the kilogram, 265 00:28:51,540 --> 00:28:56,850 you've got an uncertainty of five parts in ten to the eight, which isn't a problem for mass measurement. 266 00:28:57,930 --> 00:29:07,079 But if you want to measure something really small down here, but a milligram because the traceability chain to get there is so long, 267 00:29:07,080 --> 00:29:10,620 you are already at five in ten to the four at one milligram. 268 00:29:10,770 --> 00:29:14,270 That is now. Hasn't been in the past. 269 00:29:14,270 --> 00:29:20,210 That's now starting to get significant for some applications of measurement. 270 00:29:20,660 --> 00:29:27,950 Drug companies are making measurements down at micrograms and want to ensure they're traceable and consistent globally. 271 00:29:28,760 --> 00:29:34,250 So these are stuff that's just starting to get a problem further. KG So what's the solution? 272 00:29:34,310 --> 00:29:40,040 What's the solution to this problem of having units defined in these strange ways, including one that sits there as an artefact? 273 00:29:40,040 --> 00:29:44,600 Well, the solution is to lock all the units to unchanging properties of the universe. 274 00:29:45,140 --> 00:29:52,070 What Lagrange and Laplace thought was a good idea in 1791 to lock them to the universe, 275 00:29:52,070 --> 00:29:55,460 not to an artefact, not to a definition, to lock them to the universe. 276 00:29:56,990 --> 00:30:06,830 But because, as I said earlier, the whole of our lives are dependent on confidence and consistency of measurement. 277 00:30:07,130 --> 00:30:12,980 You have to do it without any perceptible step change in any application. 278 00:30:13,640 --> 00:30:15,350 That is a massive challenge. 279 00:30:16,310 --> 00:30:23,660 You need to select a suitable set of universal concerts that cover all the seven units and measure them with a small enough uncertainty. 280 00:30:24,050 --> 00:30:29,540 So you use the existing measurement system to measure fundamental constants. 281 00:30:29,900 --> 00:30:34,010 Then you fixed the value of the constants and let them define the units. 282 00:30:35,150 --> 00:30:49,550 This project, which was conceived either in 1791 or in 1875 when the convention was signed or really in earnest in 1960, has been absolutely mammoth. 283 00:30:50,570 --> 00:30:55,430 It makes finding the Higgs boson like falling off a log. 284 00:30:55,610 --> 00:31:03,890 It has an absolutely enormous challenge, and it was achieved in 2018 for implementation this year. 285 00:31:04,670 --> 00:31:07,610 So how do you do it? Let me explain how you do this. 286 00:31:08,570 --> 00:31:17,990 And the first step on the journey is 1967, when the second was defined by reference to a particular transition, 287 00:31:17,990 --> 00:31:22,610 a microwave transition in the Season 133 item in the 1950s. 288 00:31:22,610 --> 00:31:27,080 Example, Lewis. Lewis created the atomic clock. We've all got used to the atomic clock. 289 00:31:27,290 --> 00:31:33,740 Instead of using a pendulum or a fruit or a vibrating material of some kind that uses as its pendulum, 290 00:31:34,130 --> 00:31:40,940 the vibrations or the oscillations of a particular in this microwave transition. 291 00:31:40,940 --> 00:31:45,319 So you get a microwave and you use that and you count the number of oscillations that microwaves. 292 00:31:45,320 --> 00:32:00,320 So the second was defined in 1967 as 9,192,631,770 periods of the microwave emission from the hyper fine transition of the ground status. 293 00:32:00,320 --> 00:32:03,650 Caesium 133 You probably won't do that, but I just robot did. 294 00:32:05,270 --> 00:32:13,970 And so you are locking the second to a property of caesium atoms that is the same everywhere for all time as far as we know. 295 00:32:15,110 --> 00:32:20,599 This was really interesting because there was some argument from the astronomers who wanted it all still locked to the earth in some way, 296 00:32:20,600 --> 00:32:31,940 but they gave in and this second was defined in 1967, and that unleashed scientific research and applications in the most amazing way since then. 297 00:32:32,420 --> 00:32:41,300 Onto five Nobel prizes have been physics have been won by people researching ways in which you can improve this kind of measurement and apply it. 298 00:32:43,640 --> 00:32:50,180 Not only GPS is the outcome of this, but all of telecoms, all of the Internet, 299 00:32:51,020 --> 00:32:56,270 all absolute relies on the fact that we can make measurements really, really quite accurately. 300 00:32:56,420 --> 00:32:59,569 This picture here is Ampere's primary clock. 301 00:32:59,570 --> 00:33:04,940 So this is our clock. This is where we capture and we hold stationary caesium atoms. 302 00:33:05,150 --> 00:33:08,930 We interrogate them and we lock microwave radiation onto those. 303 00:33:08,930 --> 00:33:15,170 We lock the frequency of a microwave onto the caesium atom. And then we use that to, to define our second. 304 00:33:15,410 --> 00:33:20,389 And we can this clock is accurate to one second in 168 million years. 305 00:33:20,390 --> 00:33:23,210 So that's a reasonably accurate clock. 306 00:33:24,500 --> 00:33:35,840 So that's the second the next part of the story came in 1983 when once you defined the second, if you can measure the speed of light, 307 00:33:36,680 --> 00:33:42,980 which is believed to be a fundamental constant in the universe, you can measure the speed of light accurately, then you can define the metre. 308 00:33:46,060 --> 00:33:56,050 From reference to how far light travels in a second. So then the metre becomes part dependent on the caesium frequency and the speed of light, see. 309 00:33:56,170 --> 00:34:02,470 And so this is a speed light was measured. This is this rather fuzzy because this is a 1970s picture again from NPL. 310 00:34:02,620 --> 00:34:07,680 There were experiments like this done in earnest in the US and in various other places all across the world. 311 00:34:07,690 --> 00:34:14,320 They all had to agree. The guys who did this sort of story, the mist finished theirs just about a month before these guys finished theirs, 312 00:34:14,770 --> 00:34:22,930 and they were so worried about consistency and no chance of conclusion next sent them their results. 313 00:34:23,620 --> 00:34:29,979 No internet or anything nice, sent them their results in a brown paper envelope and they sealed it and put it in the director's 314 00:34:29,980 --> 00:34:35,470 office and would not look at it until they had their number and the number numbers agreed fortunately. 315 00:34:36,880 --> 00:34:41,500 So 299792458 metres per second is the speed of light. 316 00:34:41,620 --> 00:34:47,410 And so the second was defined like this. The Ampere is a really interesting one. 317 00:34:47,440 --> 00:34:54,820 The Ampere that is something that's literally only just been well only redefined in 2019. 318 00:34:55,180 --> 00:34:59,080 The Ampere is one over either charge on the electron. 319 00:34:59,530 --> 00:35:04,780 So again, you need time which you can get from the caesium and you need the charge on the electron. 320 00:35:04,840 --> 00:35:13,060 And the ampere is defined as the number of electrons per second one over e the charge in the electron electrons per second. 321 00:35:13,420 --> 00:35:16,540 You can't actually measure, you can't actually do this yet. 322 00:35:16,720 --> 00:35:22,990 This is really interesting. You can't actually measure what may this year for the first time in a couple of labs, 323 00:35:22,990 --> 00:35:29,979 including ours, be able to realise this unit by counting the number of electrons per second. 324 00:35:29,980 --> 00:35:37,180 But fortunately there are a couple of Nobel Prizes 1973 and 1985 that enabled you to have 325 00:35:37,180 --> 00:35:45,850 quantum realisations of the Volt and the Volt and the Resistor Neo so you could create 326 00:35:45,850 --> 00:35:51,969 situations in which you absolutely knew what the voltage across a junction was from the 327 00:35:51,970 --> 00:35:56,890 Josephson Junction or the resistance of a piece of material from the Von in effect, 328 00:35:56,890 --> 00:36:08,890 the Quantum Hall effect. So you could have and they were dependent on A and C upon the speed of light and upon the charge on the electron. 329 00:36:09,280 --> 00:36:17,830 So actually you were able to create the directly you're not able to measure the ampere by counting electrons, 330 00:36:18,130 --> 00:36:21,610 but you can definitely relate it back to the charge on the electron. 331 00:36:23,380 --> 00:36:29,540 The biggest challenge by far is this one replacing IP. 332 00:36:29,650 --> 00:36:38,200 Okay, the kilogram. That was the single biggest challenge in the whole of this exercise of there's two ways that you can do it. 333 00:36:39,040 --> 00:36:52,390 Option one is you create an artefact of known mass because if you remember the muscle, 12 grams of the number of atoms of carbon, 12 and 12 grams. 334 00:36:54,820 --> 00:37:00,310 So you could see that you could link by counting atoms, you could link back to the kilogram through there. 335 00:37:00,430 --> 00:37:03,969 And option one was a recipe for creating artefacts and in mass. 336 00:37:03,970 --> 00:37:10,750 Fortunately, the semiconductor industry can create really ultrapure silicon 28 not quite pure enough for this experiment, 337 00:37:10,750 --> 00:37:16,810 so they had to do even more work on that. And then you build a sphere, you build a sphere, and then you measure it size. 338 00:37:17,830 --> 00:37:24,310 This, these few objects were the most accurately measured objects on the planet. 339 00:37:25,030 --> 00:37:29,079 Just so you get some sense of scale. That's the kind of scale of them I've held. 340 00:37:29,080 --> 00:37:33,819 I've held a one of the first ones, but I've not held one of the edge. 341 00:37:33,820 --> 00:37:37,690 They don't let anybody hold one of these because you can't get anything on the outside at all. 342 00:37:37,930 --> 00:37:44,590 So you have to know exactly its dimensions. You have to understand surface properties and oxygen and oxidation of surface. 343 00:37:44,830 --> 00:37:54,100 It's an incredibly complicated thing, but this was the Avogadro project and that was one way of measuring the the kilogram, 344 00:37:54,370 --> 00:37:59,800 the other way of measuring the kilo with measuring mass in terms of something else, something other than masses. 345 00:38:00,460 --> 00:38:13,450 And this guy here, Brian Keppel, who sadly died in 2016, if he hadn't died, he would have been a candidate for the Nobel Prize. 346 00:38:14,170 --> 00:38:16,780 You can't win the Nobel Prize posthumously. 347 00:38:18,070 --> 00:38:29,440 He came up with the mechanism that is that was the most practical way of realising the kilogram by measuring the gravitational force. 348 00:38:29,440 --> 00:38:30,819 So if you can about imbalance, 349 00:38:30,820 --> 00:38:39,220 that's got a gravitational force measuring it in terms of electrical forces and the electrical forces could be related to fundamental constants C, 350 00:38:39,490 --> 00:38:44,350 A and H. So I said C and D speed like the electron charge. 351 00:38:44,420 --> 00:38:51,730 Already defined for the metre and the impasse he bootstrap from that a new just need h now bought Planck's constant. 352 00:38:51,740 --> 00:38:56,330 Now I'm just going to try and I'm just going to click this if it works. 353 00:38:56,330 --> 00:39:03,229 Yes, it will. I can't explain very in the time available exactly how the cable balance works, 354 00:39:03,230 --> 00:39:10,820 but I can give you a clear idea of how you might think mass and this thing Planck's constant could be related together. 355 00:39:11,270 --> 00:39:16,850 This is the most famous physics equation in history. See my only equations in the whole of the talk. 356 00:39:17,870 --> 00:39:21,110 So equals M.C. squared. Where is the energy of an object at rest? 357 00:39:21,650 --> 00:39:25,760 M is the mass of the object and C is the speed of light. 358 00:39:26,420 --> 00:39:30,020 I imagine everybody in the rooms see this equation before. 359 00:39:32,610 --> 00:39:36,530 A slightly less famous physics equation equals HSF. 360 00:39:36,540 --> 00:39:43,739 So the energy of a light quantum, the photon is Planck's constant times, 361 00:39:43,740 --> 00:39:51,180 the frequency of light and this constant Planck's constant like speed of light appears to be a fundamental property of the universe. 362 00:39:53,550 --> 00:40:00,240 If you combine those two equations, you end up with an equation that looks like this m equals h.f. obasi squared. 363 00:40:00,480 --> 00:40:15,960 So a change in the mass of a particle when it emits a photon a frequency f is that so you can see how frequency which is time, speed of light and h. 364 00:40:17,640 --> 00:40:24,360 So if you've already locked frequency to the second and speed of light to the metre, 365 00:40:25,290 --> 00:40:30,750 then h is the only the constant that gives the whole system locks it into mass. 366 00:40:32,550 --> 00:40:39,450 An interesting thing this this equation at the top here equals empty squared was of course, Einstein's famous equation. 367 00:40:40,020 --> 00:40:42,659 This equation, although it's got Planck's name associated with it, 368 00:40:42,660 --> 00:40:47,760 the first time it was ever used by anybody was by Einstein for the photoelectric effect. 369 00:40:47,760 --> 00:40:51,089 And that's actually what he got his Nobel Prize for. He didn't get his Nobel Prize for this. 370 00:40:51,090 --> 00:40:57,210 He got his Nobel Prize for understanding the photoelectric effect and coming up with an equation like that. 371 00:40:58,410 --> 00:41:04,170 So so in order to do that, you have to have this balance, 372 00:41:04,170 --> 00:41:09,930 this device that can compare weighing with incredibly accurate measurements of electrical forces. 373 00:41:09,930 --> 00:41:18,509 It is a fiendishly complex experiment. There are people who have spent 40 years their entire career doing this experiment. 374 00:41:18,510 --> 00:41:21,870 There was a guy, an apple, who worked with Brian Kebble. 375 00:41:22,170 --> 00:41:26,430 This guy has been working 30 years. Brian Cable was working ten or 15 years before him. 376 00:41:26,850 --> 00:41:34,890 It is fiendishly complicated because you have to do it all to get an uncertainty of one part in ten to the eight. 377 00:41:34,980 --> 00:41:39,059 And it's a mechanical and electrical experiment at one part in 100 million. 378 00:41:39,060 --> 00:41:47,610 It is fiendishly complicated. And in 2017, when I sat down with the CPM, this was the data that we were shown. 379 00:41:48,270 --> 00:41:54,509 So I'll try and explain this graph. This graph are all the experiments that have been done since 1990. 380 00:41:54,510 --> 00:42:01,589 There were more before that, but they have bigger error bars. These are all experiments done since 1990 and these are all measurements of H. 381 00:42:01,590 --> 00:42:08,010 So taking that CPU balanced measurements or those silicon sphere measurements and because 382 00:42:08,010 --> 00:42:12,719 of the way work worked all locking it all back on to we're measuring h Planck's constant. 383 00:42:12,720 --> 00:42:16,770 These are the measurements from all of that time this scale here. 384 00:42:17,730 --> 00:42:27,630 There was a, there was an assessment of what Planck's constant was in 2014 by the Global Physical Constants Group, the co data. 385 00:42:27,840 --> 00:42:35,700 And so this scale along here is parts in ten to the eight away from the previous definition of eight. 386 00:42:35,700 --> 00:42:37,079 So you could see they all cluster. 387 00:42:37,080 --> 00:42:46,440 And there was I can tell you there was 3 hours of discussion at the consulting committee on units and then at least half a day of discussion at 388 00:42:46,440 --> 00:42:57,420 CPM about whether we really believed that this was consistent enough to lock finally locked the last of the units to a fundamental constant. 389 00:42:58,290 --> 00:43:00,149 And this was the number we came out with. 390 00:43:00,150 --> 00:43:09,870 That's Planck's constant, because this was this was go no go for the whole conference to say yes or no to doing this. 391 00:43:09,870 --> 00:43:13,050 And it was an interesting discussion, but we did say yes. 392 00:43:14,580 --> 00:43:23,520 So we have seven units and seven constants. The second related to that fundamental, that constant of nature, we could have chosen another atom, 393 00:43:24,030 --> 00:43:29,010 but caesium the metre was related to that caesium property and speed of light. 394 00:43:29,280 --> 00:43:38,550 The ampere again for the caesium property and the electron to the electron, the kilogram to the speed of light, 395 00:43:38,820 --> 00:43:46,590 the caesium transition and Planck's constant, the Boltzmann constant is a scaling constant. 396 00:43:46,590 --> 00:43:51,540 The Boltzmann constant is the constant, that is the scale between temperature and average energy. 397 00:43:52,350 --> 00:43:56,340 In order to get that constant, there have to be some of the most accurate measurement, 398 00:43:56,350 --> 00:44:02,850 one of the most accurate measurements of temperature ever done at about 20 laps around the world. 399 00:44:03,810 --> 00:44:07,290 The Candela is a technical constant. As I said, that hasn't changed. 400 00:44:07,290 --> 00:44:11,910 That's just this relationship between light energy and how we perceive it. 401 00:44:12,420 --> 00:44:16,829 And the Avogadro constant, which came out of the silicon sphere and other things was fixed. 402 00:44:16,830 --> 00:44:21,660 So this is seven constants, seven units, this was the end of the project. 403 00:44:22,470 --> 00:44:31,220 And so from next year it was agreed last year from 20th of May 2019, the anniversary of the signing of the original beach convention 20. 404 00:44:31,310 --> 00:44:36,560 As of May, the site will be the system of units in which the following constants have exact values. 405 00:44:36,920 --> 00:44:42,290 So these are now fixed, these have zero uncertainty, these are exact numbers. 406 00:44:42,950 --> 00:44:48,830 And so you infer units of measurement from those rather than measure these with units of measurement. 407 00:44:52,040 --> 00:44:58,430 So we have a new size. So there was a historic and a unanimous vote on the 16th of Ember 2018. 408 00:45:00,200 --> 00:45:04,400 This was it in Paris. I've never known so much press. 409 00:45:05,720 --> 00:45:10,070 I guess everybody probably heard about the KG finally being pensioned off. 410 00:45:11,210 --> 00:45:17,300 If you work in metrology used to people not knowing what measurement is or how important it is, and it's just kind of goes on under the surface. 411 00:45:17,300 --> 00:45:21,140 But this was mopped, literally mopped by the press, this conference. 412 00:45:21,140 --> 00:45:30,650 It was bizarre, but this is a once in a generation moment to futureproof the system and to enable and catalyse new science, 413 00:45:30,650 --> 00:45:34,520 technology and applications. Because when you can measure things more accurately, 414 00:45:34,760 --> 00:45:42,140 you get that synergistic relationship between more accurate measurement and people drawing on that to improve technology, 415 00:45:42,440 --> 00:45:45,259 which in turn can help you to make more accurate measurements, 416 00:45:45,260 --> 00:45:50,930 you get a synergy between the two that has developed and created some of the most astonishing technology we have today. 417 00:45:51,050 --> 00:46:00,709 So everybody was very excited about this. And this was a video that was created about how excited I was about 130 years groundbreaking 418 00:46:00,710 --> 00:46:07,280 science and the agreement from the world's scientific community that tells it's impossible, 419 00:46:07,640 --> 00:46:19,550 accurate, precise measurements. Anytime, anywhere, fast, we can identify that the atmosphere you're going to get to see a body, one missing. 420 00:46:19,700 --> 00:46:25,180 The line rolled down on my knees. 421 00:46:25,270 --> 00:46:36,170 Yeah, but it was on me. You know, I'm really trying to come up with my thought, you know, how hard is that? 422 00:46:36,460 --> 00:46:41,910 And now? So it was clear that itself. 423 00:46:42,380 --> 00:46:50,090 But I thought, I'm going to have to fly through this country. 424 00:46:50,690 --> 00:46:56,770 Oh, yeah. Well, I made a point to show off my work. 425 00:46:57,410 --> 00:47:01,280 How? My I'm. Oh, very special. 426 00:47:01,640 --> 00:47:09,200 Congratulations. So there we go. 427 00:47:10,010 --> 00:47:23,810 For all time and for all people. Maybe the first one I talked to you about was the second locked to the hyper fun transition to the season 133 up. 428 00:47:24,890 --> 00:47:31,640 Because it's a microwave emission, it puts an absolutely fundamental limit on how accurately time can be measured. 429 00:47:31,640 --> 00:47:38,930 It's still a measurement that is defined where the realisation is implicit in the way it's defined. 430 00:47:39,890 --> 00:47:48,830 So across the world at the moment there are a large number of people trying to create clocks that instead of relying on a transition, 431 00:47:48,830 --> 00:47:56,420 a microwave transition, that particular micro transition in caesium can be locked to optical transitions. 432 00:47:56,420 --> 00:48:03,530 This is the MPL, one of the Ampere clocks, and this is the heart of it. 433 00:48:03,710 --> 00:48:11,540 And in here we can hold a single atom, a single atom of strontium 90, we can call it to absolute zero with lasers, 434 00:48:11,780 --> 00:48:20,719 and then we can probe it and lock a clock to its frequency of that emission that will 435 00:48:20,720 --> 00:48:25,700 enable measurements with an accuracy of one second in the lifetime of the universe, 436 00:48:26,170 --> 00:48:31,460 and probably in 2026 the site will be tweaked again. 437 00:48:32,240 --> 00:48:36,470 But that shouldn't take away from the excitement of luck year. So I'll finish.