Can you measure it? - A stimulating trip to the home of measurement science

How do we know exactly how much a kilogram weighs? Who changes the clocks when we move to British summer time? Who could you turn to during a food-safety dispute? How do you know if a radiotherapy machine is delivering the correct treatment dose?

You can find the answers to all these and more at the National Physical Laboratory (NPL) and National Measurement Laboratory(NML) based in Teddington, Middlesex. Last week, I visited as part of a trip organised by the Parliamentary Office of Science and Technology with whom I am currently undertaking a 3-month Fellowship. NPL and NML, the ‘home of measurement’, deliver world-leading solutions for governments, businesses, industry, the medical sector – just about anyone who measures anything. Our tour began at NPL, who help validate many of the fundamental units we use every day including the second, the ampere and the kilogram. One can imagine the chaos if these varied across the globe… (fun fact; the original Kg, against which all others have been measured, lies in a vault outside Paris). NPL’s work also covers more ‘trivial’ matters; for instance, checking that the balls in the National Lottery were of equal size and weight so that it is just that – a random lottery. Increasingly, their remit is including digital technologies: with AI advancing so rapidly, it is vital we can trust autonomous decisions made by algorithms, for instance in controlling traffic flows. One conundrum NPL is working on is being able to replicate machine learning, since this is effectively rescrambled with each run, creating issues with transparency. 

The National Physical Laboratory, based in beautiful Teddington (copyright National Physical Laboratory)

NPL also play a vital role in standardising medical treatments such as radiotherapy, which destroys cancer cells using high-energy radiation. As this can also damage healthy cells, it is crucial that the dose is the correct dosage and applied at the right area. So how can hospitals (safely) find out if their machines accurately scan their patients and then deliver the correct treatment? The answer: hospitals are sent a 3D-printed ‘phantom’ tumour, which they scan and treat before sending back to NPL to compare with the results from the reference scanner. Most of us only get to see the front-line of hospital treatment, so it was intriguing to learn more of the ‘back-end’ operations that keep them functional.

Besides their static laboratories, NPL also has mobile facilities which travel around the globe. Currently they are involved in Breathe London, an ambitious project to create a ‘hyperlocal’ dynamic air-quality map of London. Over 100 low-cost air quality sensors have been distributed across the city – but are they any good? NPL is calibrating these using two Google street cars which rove the city, checking the local sensors against an on-board reference, to ensure the measurements aren’t picking up other factors such as water vapour. If successful, this could pioneer similar systems in other cities across the world to deliver better air-quality management programmes.

Checking hospital radiotherapy equipment is just one of NPL's areas of work (copyright National Physical Laboratory)

On a bigger scale, the Differential Absorption LIDAR facility (essentially a laboratory contained within a lorry) has travelled the world to measure atmospheric composition. It works by firing lasers into the sky and measuring the pattern of laser light scattered by dust particles. Beams targeting specific gases are compared to a reference standard to decipher the proportions of different gases. Capable of scanning up to a Km away to a resolution of a few metres, this facility has detected harmful emissions from sites such as oil rigs and landfills which may otherwise have been missed. 

The groovy GoogleStreet cars used in Project Breathe (copyright National Physical Laboratory)

In the afternoon we toured NML, the designated institute for chemical and biological measurement, which works with global organisations to standardise measurement science. In the Organic and Inorganic labs, we awed over mass spectrometers costing over half a million pounds, capable of detecting compounds in parts per trillion. Since these are a tad bit pricey for the average police station, we also saw prototypes for cheaper, portable versions that could reduce drug detection times from days to seconds. In the brand-spanking new Molecular + Cell laboratories, we learnt of NML’s work in monitoring the spread of anti-microbial resistance, eradicating infection diseases and improving cancer treatments. Much of this relies on cutting-edge genetic techniques: accurate gene sequencing, for instance, can divide cancers into subtypes to allow more targeted treatment. But rigorous standards are needed to prevent false interpretations; a negative result, for example, could result either from the cancer not being present or an error in the sequencing process. On display were the latest in next-generation mini-sequencing machines: highly compact yet capable of doing in 2-3 days what it took the Human Genome Project 13 years and 20 countries to achieve.

NPL's impressive Differential Absorption LIDAR mobile lab (copyright National Physical Laboratory)

We then had a brief overview of the role of the Government Chemist, an independent arbitrator for disputes over spurious sample results. Although the role was originally established in 1842 to help prevent tobacco adulteration, the present responsibilities include solving disputes in the food and feed sector advising Government and industry on measurement science matters and conducting research. Currently one priority is validating the accuracy of personal data devices, such as apple watches, that promote the concept of ‘consumers as analysts’.

Over tea and some rather moreish coconut cake, we finished off with a round table discussion on how NPL/NML and POST could collaborate in the future. It will be exciting to see how both institutes can work together towards the shared aim of ensuring policy decisions are based on accurate science. Meanwhile, I have a whole new appreciation for measurement science, and realise how we truly take for granted that a second (or metre, or ampere, etc) is always the same, wherever we are in the world. With thanks to POST and NPL/NML for such a stimulating day out!