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In his book ‘The French Revolution – A Very Short Introduction’ Professor William Doyle describes the Metric System as “the most complete triumph of any of the many trends and movements that the French Revolution began, its fullest and least ambiguous living legacy”. Whilst the origins of the Metric System were indeed in the 1790s following the social upheaval in France, it took until 20 May 1875 for international agreement on weights and measures to be achieved. This was the day that the Metre Convention was signed. This was a diplomatic treaty, still in existence, that established an international organization for member governments to act together on matters relating to units of measurement – the International Bureau of Weights and Measures. This agreement on units provided great benefits for trade and industry and thus over the years its membership has grown to encompass today countries responsible for more than 98 % of global economic output. On 20 May this year – World Metrology Day – the 150th anniversary of the signing of the Metre Convention will be celebrated at a special event taking place at UNESCO’s headquarters in Paris, emphasising the essential role that metrology – the science of measurement – has played, and will continue to play, in driving progress and innovation in science and in society through multilateral collaboration.
At the centre of this agreement on measurement is the International System of Units (SI, the modern name for the Metric System) comprising the familiar seven SI base units: second, metre, kilogram, ampere, kelvin, candela and mole; the SI derived units made from combinations of these base units, such as metre per second; and the SI prefixes that we use to describe measurements when they get really big or really small, for example the nanometre. The SI is the only globally agreed system of units and plays an essential role in providing confidence in the accuracy and global comparability of the measurements needed for international trade, manufacturing, human health and safety, protection of the environment, global climate studies, scientific research, and indeed all of human life! The responsibility for maintaining, developing and improving the national measurement standards for these units, ensuring their comparability internationally, and disseminating the values of these to end users via reference measurements and calibrations falls on each country’s National Metrology Institute (NMI). The UK’s NMI is the National Physical Laboratory (NPL) – a public sector research establishment owned by DSIT. NPL is the largest part of the UK’s National Measurement System (NMS), an infrastructure of laboratories that deliver world-class measurement science and technology. The NMS also addresses cross cutting national and global measurement challenges in thematic areas such as advanced manufacturing, digital, energy and environment, life sciences and health, security and resilience.
NPL was established on 1 January 1900 and this year celebrates 125 years of delivering impact from science to benefit people, prosperity and the planet. Over the years NPL has contributed hugely ‘to effect the union between science and commerce’ – part of its original mission as stated by the future King George V during NPL’s official opening in 1902 – making fundamental contributions to metallurgy, ship design, aircraft technology, computer science and the internet, radar, and countless other areas of fundamental measurement science. A number of events have been organised to celebrate this milestone and NPL’s achievements. These also look forward to future challenges in emerging areas such as digitalisation, artificial intelligence, quantum science, resilient timing and engineering biology. Accurate and comparable measurement will be crucial for these technologies to reach their full potential, ensuring the essential role of NPL, the NMS, and the global measurement system for many years to come.
16 May 2025