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?

Transcript

FARZANA MASOULEH

We are moving forward from a set of units that were laid back by old technology and physical objects to a system of units that are defined based on the physical properties of nature. And what does really these definitions give us? So the first thing that it gives to us is the accuracy. So our measurements would be accurate everywhere in the world as long as we are using these physical constants. And these physical constants really will stay constant as long as the laws of physics that we know currently stay the same. So, with accuracy comes availability and comes stability, because we will be able to use these accurate measurements everywhere at any time. If you want, we can use them in space, on the Mars or even on any other planet that you’d like. So you will have them available and accessible everywhere.

But the main point is that Measurement Standards Laboratory will still keep the units for you and you don’t have to be worried about it because everyday life is not going to be changing. Although for us metrologists, it’s a very important point in our career. But still, water will freeze under 0 and still 1 kilogram of cheese will be 1 kilogram of cheese. So unfortunately, if after 20th May you start to get speeding tickets, this doesn’t mean that it’s related to redefinition or it’s because the calibration is not done right. This means that next time you should slow down.

So with all that being said, sometimes we are asked, “Why do we need to know, for example, 1 ampere to the accuracy of 1 nanoampere or even more?” I want to ask another question. When we hear that people want to improve the polish on their lens in a telescope, we don’t question why because we know that they want to get an image with a better resolution – something like this.

To the same extent, redefining SI base units, based on physical constants, will lay a foundation for technological advancements in the future. Who knows what these new definitions will have for us in the future?

Acknowledgements

This video clip is from a recording of a presentation by the Measurement Standards Laboratory of New Zealand (MSL) in celebration of the redefinition of the International System of Units (SI), which happened on 20 May 2019. The presentation by Peter Saunders and Farzana Masouleh of MSL was filmed at Unleash Space, Faculty of Engineering, Auckland University.