The definition of the kilogram was established 130 years ago. However, a new definition has now been approved, after a unanimous vote at the General Conference on Weights and Measures last year.
Why is the definition changing?
To put it simply, the new definition is more accurate as it relies on the laws of physics. Previously, the kilogram was defined by a physical metal object weighing one kilogram made in 1889. Several copies were made and placed in various locations around the world; however, these copies have been found to drift from the standard over some time. Given they were drifting, it was fair to assume that maybe the original kilogram may be drifting too.
The kilogram has now been redefined using the Planck constant, the speed of light and the resonant frequency of the caesium atom, meaning it will be consistently accurate and unable to drift.
Why is this important?
Metrology and calibration are used in many aspects of our lives, even if we don’t realise it. Therefore, it needs to be incredibly precise and constant. In the world of science, and in particular metrology, it will have substantial flow-on effects, but it isn’t something we will notice in our daily lives.
How does this affect me? In short, most likely it won’t in any measurable way, and most definitely not on your bathroom scales. If you use very precise scales, they will now be calibrated by us, with weights that have been calibrated against a new measure of the kilogram. Other than that, everything will work just as it did before, but you now have a new piece of trivia with which to impress your friends.
