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How Long is a Metre?
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Film summary
The evolution of standard measurements from body parts to precise, universal measures.Transcript
The metre is the base unit of length used in the majority of the world.
But it took a long time for people to agree on just how long it should be.
Standardising Units
Measurements of length were originally based on the human body, like the length of a foot, or the span of a hand.
This could lead to confusion, as these lengths varied from person to person.
Egypt, 3000 BC
In ancient Egypt, the base unit of length was a cubit – a measurement that varied depending on the length of a person's forearms, hands, and palms.
To avoid these variations in length, the Egyptians created a standard 'royal cubit'.
Copies of this cubit were produced in granite, and distributed to standardise measurement.
This system allowed construction to flourish in the region.
Similar systems developed around the world, but they tended to be specific to a region, making trading difficult.
France, 18th Century
By the 18th Century, in France alone, there were over 800 different names for measures.
The variances in these measures, meant there were around 250,000 different units of measurement.
A standard measurement needed to be found – the metre.
Standard International Units
It was decided that the metre should be a length that was the same the whole world over.
A metre would be one ten-millionth of the distance from the North Pole to the equator.
This was calculated using trigonometry, and an official metre bar was created in Paris in 1795.
Using the decimal system, other lengths could be calculated simply from the new metre.
The metre became the international standard for length, but was redefined more accurately in 1983.
We now define one metre as the distance which light travels in a vacuum in a little over three-hundred millionths of a second.
