On the façade of the Ministry of Justice in Paris, just below a window on the ground floor, is a marble slab engraved with a horizontal line and the word ‘MÈTRE’.
It’s barely noticeable on the grand Place Vendme – in fact, out of all the tourists on the square, I was the only one who stopped and reflected on it.
But this plaque is one of the last ‘yardstick’ (Standard Meter Bar) that were put up 200 years ago in an attempt to introduce a new universal system of measurement throughout the city.
And it is one of many sites in Paris that point to the long and fascinating history of the metric system.
“Measurement is one of the most common and common things, but it’s actually the things we consider to be the most interesting and controversial in history,” said author Ken Elder, a professor of history at Northwestern University in the US. measure of everything, a book on the construction of the Metro.
It is now a thing in most places: the metric system, created in France, is the official measurement system in almost every country in the world, except the United States, Liberia, and Myanmar. And even there, the metric system is still used for purposes such as global trade.
But imagine a world where every time you travel, you need to use different conversions for measurement, as we do with currencies.
This was the case before the French Revolution in the late 18th century, when weights and measurements varied not only from nation to nation, but also within nations.
In France alone, it is estimated that thousands of different units of weight and measure were in use at the time.
The French Revolution changed this.
During the volatile years of 1789 to 1799, the revolutionaries sought not only to overthrow politics, taking power from the monarchy and the church, but also to radically change society by overturning old traditions and customs.
To this end, he introduced, among other things, the Republican calendar in 1793, which included 10-hour days, consisting of 100 minutes per hour and 100 seconds per minute.
In addition to eliminating the religious influence of the calendar, making it difficult for Catholics to keep track of Sundays and holy days, it helped introduce the decimal system to France.
But while the decimal hour did not advance, the new decimal system of measurement, which is the basis for the meter and kilogram, is still with us today.
The task of creating a new system of measurement was given to the most prominent scientific thinkers of the Enlightenment.
These scientists were eager to create a new uniform system based on logic rather than tradition or the will of the local authorities.
Therefore it was decided that the meter would be completely based on nature. It was thought to be one ten millionth of the distance from the North Pole to the Equator.
The line of longitude from the pole to the equator, which would be used to determine the length of the new standard, was the Paris Meridian.
This line was drawn by two astronomers who left Paris in 1792: Jean-Baptiste-Joseph Delambre, who traveled north to Dunkirk, and Pierre Méchin, who traveled south to Barcelona.
He used the latest technology of the time and the mathematical process of triangulation to measure the meridian arc between these two places at sea level.
Then, by spanning the distance between the North Pole and the equator to an ellipsoid, the two astronomers agreed to meet within a year in Paris to propose a new universal standard of measurement.
However, the process took seven years. Finally, in 1799, Delambre and Méchen presented their results, and based on them, a 1 meter long platinum bar was created to serve as the basis for the metric system.
As the Elder describes in his book, measuring this meridian arc proved to be an epic undertaking at a time of great political and social upheaval.
The two astronomers were often met with skepticism and hostility; They fell into the favor and disgrace of the state; And they were also injured at work, which involved climbing high places such as church domes.
The Pantheon, which was originally commissioned by Louis XIV to be a church, became the central geodesic station in Paris – from its dome, the Delambre, triangulating all the points around the city.
Today, it serves as a mausoleum for the heroes of the Republic such as Voltaire, René Descartes and Victor Hugo. But in Delambre’s day it served as a tomb of another kind – a storehouse for all the old weights and measures that were shipped from cities across France in anticipation of the new system.
But despite all the effort and technology invested in defining the new measure, no one wanted to use it.
People were reluctant to abandon the old methods of measuring, as they were intrinsically linked to local customs, customs and economies.
For example, an LL, the cloth measure, is usually equal to the width of the local looms, while arable land was often measured in days, referring to the amount of land a farmer would prepare during that time. Happened.
Paris officials were so outraged by the public’s refusal to leave the old measure behind that they even sent police inspectors to the markets to enforce the new system.
Finally, in 1812, Napoleon abandoned the metric system; Although it was still taught in school, they let people use whatever measurements they wanted until the metric system was restored in 1840.
According to Ken Elder, “It took almost 100 years for almost all French people to start using it.”
But it is not only because of the persistence of the state.
France was rapidly approaching the Industrial Revolution; Mapping for military purposes requires greater accuracy; And, in 1851, the first Great World’s Fairs were held, in which nations were to present and compare industrial and scientific knowledge.
Of course, this was difficult to do unless you had clear standard measurements like meters and kilograms.
For example, the Eiffel Tower was built for the 1889 World’s Fair in Paris and was the tallest man-made structure in the world at the time, at 324 metres.
All this led to the creation of one of the oldest international institutions in the world: the International Bureau of Weights and Measures (BIPM, for its acronym in French).
Located in the quiet suburb of Svres in Paris, BIPM is surrounded by parks and gardens. Your lack of pomp reminded me again Criteria at Place Vendome; It may be hidden, but it is fundamental to the world we live in today.
Originally established to preserve international standards, BIPM promotes the uniformity of seven international units of measurement: meter, kilogram, second, ampere (which measures the intensity of electric current), kelvin (unit of temperature), mol (amount of substance) and candela (luminous intensity).
This is where the Platinum Master standard meter bar is used to carefully calibrate the copies, which were then sent to various other national capitals.
In the 1980s, the BIPM defined the meter as the distance traveled by light in a vacuum over a specific time interval, making it more accurate than ever.
Since then, it has finally become a truly nature-based measurement, defined by the universal laws of physics.
The Svres building also houses the original kilogram, which sits under three domes in an underground vault that can only be accessed via three separate keys held by three different people.
Now, the kilo is calculated by the so-called kibble (or watt) balance, a device that allows mechanical and electromagnetic energy to be compared using two separate experiments.
This method of measuring the kilo does not change, nor can it be damaged or lost, as may be the case with a physical object.
Furthermore, a definition based on a constant – not an object – makes the exact measurement of the kilo, at least in theory, available to anyone anywhere on the planet, not just those who have it stored in France. Basic kg is accessible.
As with the 18th century meridian project, defining measurement remains one of our most important and difficult challenges.
What started with the metro became the basis of our modern economy and led to globalization. It paved the way for high-precision engineering and remains essential to science and research as well as to our understanding of the universe.
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