The new SI

Advancing the teaching of measurement through the Revised SI

On 20 May 2019 (World Metrology Day) the new definitions of the SI units came into force and for the first time, all seven of the SI units have their definitions linked to one or more of seven fundamental constants of nature. The consequences for both metrology and science are quite profound, and furthermore it opens unique opportunities for science education.

Useful resources are available on the BIPM website here


MeASURe in close collaboration with the National Metrology Institute of South Africa are developing materials to enhance the teaching of measurement and laboratory work at schools and university. The first of these materials are a set of posters which may be downloaded and distributed freely:

Trio of posters on the Revised SI. 

Basic single poster on the Revised SI.

[The seven measurettes were designed by Tanya Hutton.]

Video introducing the "Measurement Education" project


Physics do-at-home practicals

A collection of university-level practical tasks for doing at home, at first, second and third year level.


Teaching the ISO-GUM framework for measurement and uncertainty

UCT Physics is also the only department in South Africa and one of the few worldwide where the ISO-recommended framework for the expression of measurement and uncertainty is taught throughout the curriculum, according to the so-called “Guide to the Expression of Uncertainty in Measurement” or the “GUM”. The department also has a strong track record in researching the difficulties that students have when dealing with scientific measurement and uncertainty.

Manual: Introduction to Measurement in the Physics Laboratory: A Probabilistic Approach

The new SI

The Revised SI units

Metrology is presently facing a very significant change in the ways in which the seven base SI units are defined. The present system which includes a number of arcane artefacts, such as the International Prototype Kilogram, has been redefined in terms of a number of quantum standards based on the fundamental constants of nature, most notably the speed of light and Planck’s constant. The introduction of these new definitions in 2018 offers a unique opportunity for metrology make useful impact to physics education, both at high school and university. We have undertaken a project which explores the ways in which introductory physics students interpret the universality of the constants of nature, and how these views translate into their own philosophies of the nature of physics. The results will inform the development of materials which introduce the new quantum standards underpinning the new SI units to both school and university students.

The art and act of measurement defines the very heart of the enterprise of Science. We live in a real world of tangible experiences, of interactions, of experiment, of natural phenomena. Scientists are constantly making choices in order to filter nature to reveal its secrets, by idealising the infinitely complex phenomena of our universe. Scientific observation thus becomes an approximation of reality, a simplification of complexity, an ordering to scale. Measurement is what allows the complex to become simple. Observation leads to order, to pattern, to relationship, to law.

The nature and definition of measurement scale has itself become a serious pursuit of humankind and science. Metrology, as the science of measurement, includes all theoretical and practical aspects of measurement and its application. Scientific and fundamental metrology concerns the establishment of quantity systems, units of measurement, the development of new measurement methods, the realization of measurement standards, and the transfer of traceability from these standards to users in society.