20 May 2018 - World Metrology Day - will mark the official start of the campaign towards the historic revision of the International System of Units (the SI), which is expected to be agreed at the 26th General Conference on Weights and Measures (CGPM) in November 2018. The theme "Constant evolution of the International System of Units" was chosen to reflect what will be one of the largest changes to the SI since its inception. The World Metrology Day Resource Website, which includes the Press Release, the Directors' Messages and the poster, is now live. The 2018 poster was designed by METAS (Switzerland) and the slogan 'Constant evolution' was proposed by INRIM (Italy).
In the revised SI, four of the SI base units - namely the kilogram, the ampere, the kelvin and the mole - will be redefined in terms of constants; the new definitions will be based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (kB), and the Avogadro constant (NA), respectively. Further, the definitions of all seven base units of the SI will be uniformly expressed using the explicit-constant formulation, and specific mises en pratique will be drawn up to explain the realization of the definitions of each of the base units in a practical way.
This historic change towards using the rules of nature in the definitions will eliminate the final link between the SI and definitions based on physical artefacts, the last one being the International Prototype of the Kilogram (IPK), which was sanctioned by the 1st CGPM in 1889. Great attention has been paid to ensure that the new definitions will be compatible with the old ones at the time the change is implemented, so that the changes will be unnoticeable to all but the most demanding users.
The International System of Units (SI) is the accepted set of units for all applications of measurement world-wide. Since it was first given the name SI nearly 60 years ago, improvements have been agreed to it whenever it has been possible to exploit advances in measurement technologies to address new requirements and to meet the needs of users. As science and technology continues to progress, the demands for measurements to underpin new products and services is growing exponentially. The revision will make it easier to exploit advances in measurement technologies, since the changes have the advantage of being based firmly on the laws of physics.
The steps taken by the BIPM and the wider metrology community to advance the SI in 2018 will ensure that the science of measurement and the SI remain at the forefront of scientific and technological innovation for the 21st century and beyond.
Last year's World Metrology Day was a huge success; we hope to build on that success in 2018. On the resource website, you may download the Press Release, the Directors' Messages and the poster. The poster may be downloaded in PDF format in English and French, and in PhotoShop format in English.
Please help us to spread the word about World Metrology Day and let the World Metrology Day Team know by email about the events you are organizing in your country so that we can include them on the website. If you need inspiration, you can see the sort of events organized by other NMIs in previous years on the website.