EVOLVEMENT OF THE METERIC

How Metric system evolved in France, now it sets a world standard: Iyer

Originally established to preserve international standards, the BIPM - The International Bureau of Weights and Measures (BIPM). Located in the quiet Paris suburb of Sèvres, is one of the world's oldest scientific institution. The BIPM promotes the uniformity of seven international units of measurement: the metre, the kilogram, the second, the ampere, the kelvin, the mole and the candela. 

it was proposed in 1792, by two French astronomers - François Arago & Jean-Baptiste-Joseph Delambre to measure the metre, which was to be based purely on nature. This is the line that the two astronomers set out from Paris - it was to be one 10-millionth of the distance from the North Pole to the equator.

The line of longitude running from the pole to the equator that would be used to determine the length of the new standard was the Paris meridian. This line dissects the centre of the Paris Observatory building as seen below:

The line of longitude used to determine the length of the metre runs through the centre of the Paris Observatory (Credit: Madhvi Ramani)

But  in 1812, Napoleon abandoned the metric system; although it was still taught in school, he largely let people use whichever measures they liked until it was reinstated in 1840. According to Dr Adler, "It took a span of roughly 100 years before almost all French people started using it."

In the 1960s, the BIPM redefined the metre in terms of light, making it more precise than ever. And now, defined by universal laws of physics, it was finally a measure truly based on nature.

Kilogram: The BIPM building in France is also home to the original kilogram, which sits under three bell jars in an underground vault and can only be accessed using three different keys, held by three different individuals. The small, cylindrical weight cast in platinum-iridium alloy is also, like the metre, due to be redefined in terms of nature – specifically the quantum-mechanical quantity known as the Planck constant – by the BIPM this November.

"Establishing a new basis for a new definition of the kilogram is a very big technological challenge. [It] was described at one point as the second most difficult experiment in the whole world, the first being discovering the Higgs Boson," said Dr Martin Milton, director of the BIPM, where in the lab the research is being conducted.

Global Impact:  What started with the metre formed the basis of our modern economy and led to globalisation. It enabled high-precision engineering and continues to be essential for science and research, progressing our understanding of the universe.