On 20 May this year the definition of kilogram changed. The new definition fits in with the modern definitions for the units of time (second) and distance (metre).
Most of us grew up using the metric system which is an internationally recognised decimalised system of measurement used to measure everyday things such as the mass of a sack of rice, the height of a person, the speed of a car, and the volume of fuel in its tank.
It is interesting to go into the history of this system. The metric system was introduced by the French after the French Revolution at the end of the 18th century, at a time when there was a chaotic state of thousands of traditional units of measurement in use. Twelve scientists were appointed to organise a universal and accurate system of measurement. They chose ‘metre’ after the Greek word for measure ‘metron’; and for simplicity of multiplying and dividing they decided to base it on the number ‘ten.’ One metre was to be one-tenth millionth of one quarter of the circumference of the Earth, measured from the Pole to the Equator.
By 1795 all metric units were derived from the metre, including the gram for weight and the litre for capacity. At first people were reluctant to accept the new measures but in 1840 they were legally enforced and there were punishments for those who refused to use the metric system.
The history of the predecessor to the Kilometre—the Mile, can be traced back to the Romans who invented a way of measuring distance in footsteps. A Mile was a thousand footsteps. The Romans marked their miles with special stones called Milestones.
Measuring land was difficult in olden days. Sometimes fields were measured according to how much land could be ploughed by a pair of oxen in one day. In an unusual way of measuring land—if someone wanted to buy land, coins were put around the edges of the piece of land with all the coins touching each other. The cost of the land was said to be the number of coins that it took to surround it.
Today the global standards for measurement are set by the International Bureau of Weights and Measures which is located in Sevres near Paris. It is this international laboratory where international standards are kept; national standard copies inspected, and metrological research is conducted. The General Conference on Weights and Measures (CGPM), with diplomatic representatives of some 40 countries, meets every six years to consider reform. The conference selects 18 scientists who form the International Committee for Weights and Measures that governs the bureau.
As science advances so does precision, and today measurements are finely honed towards a hundred per cent accuracy. Thankfully, for most of us laymen this fine tuning does not mean too much change. News reports assured us that the ‘new improved’ kilogram would not impact weight watchers or grocery shoppers.