The SI – past and present
The International System of Units – the SI – was created to meet the needs of growing globalisation. The SI has expanded and evolved over the years to reflect advancements in technology. This interactive traces its history – and perhaps its future.
To use this interactive, move your mouse or finger over any of the labelled boxes and click to obtain more information.
This resource was created with the assistance of the Measurement Standards Laboratory of New Zealand.
Note: The background image is the Pavillon de Breteuil. The building had been used since 1875 by the International Bureau of Weights and Measures. Public domain.
Transcript
Regional measurement systems
Dr Peter Saunders gives us an insight to the wide variety of measurement systems that existed in Europe a few centuries ago.
Discussion point: Why were measurement standards useful for trade within a town but difficult for trade between towns?
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The birth of the SI
Dr Peter Saunders explains how the first three SI units – the metre, litre and kilogram – were created.
Discussion point: In 1791, the first of the modern metric measurements were introduced, along with the quote “For all time, for all people”. Do you think this quote has stood the test of time? Why?
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A global measurement system
Dr Peter Saunders explains how the Industrial Revolution and advances in science furthered the need for an accurate universal system of measurement.
Discussion point: Even though the Industrial Revolution began in Great Britain, why do you think they wanted to stick to their own units of measurement rather than sign up to the Metre Convention?
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International prototypes
Dr Peter Saunders notes that, from 1879–2019, the kilogram and the metre were defined by physical objects known as international prototypes.
Discussion point: Over time, the IPK has changed and is a tiny bit different from the replicas that were distributed in 1875 – but only by 50 micrograms. Does this matter?
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The future of the SI
Farzana Masouleh explains how the new SI definitions give us universal accuracy, availability and stability.
Discussion point: What does Farzana mean when she says we can use SI units on other planets?
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Acknowledgement
This resource has been updated with the assistance of the Measurement Standards Laboratory of New Zealand.
