The incredible story of France’s creation of the metric decimal system

On the facade of the Ministry of Justice in Paris, just below a ground floor window, is a marble slab inscribed with a horizontal line and the word “METER”.

It’s barely noticeable on the majestic Place Vendôme – in fact, of all the tourists in the square, I was the only one to stop and meditate on it.

But this painting is one of the last “Ladder” (Standard Metric Rods) were placed in the city over 200 years ago with the aim of introducing a new global measurement system.

This is just one of the many Parisian sites that refer to the long and fascinating history of the metric system.

Ken Alder, professor of history at Northwestern University in the United States and author of measure everything, A book on the construction of the metro.

This is now a matter of course in most places: the metric system, which was created in France, is the official measurement system in almost every country in the world except the United States, Liberia and the United States. Myanmar. And even there the metric system is still used for purposes such as world trade.

But imagine a world where every time you travel you have to use different conversions for measurements, just like we do with currencies.

This was the case before the French Revolution at the end of the 18th century, when weights and measures differed not only from state to state, but also within states.

In France alone, it is estimated that at this time, thousands of different units of weights and measures were used.

The French Revolution changed that.

During the turbulent years from 1789 to 1799, revolutionaries sought not only to overthrow politics, to seize power from the monarchy and the Church, but also to fundamentally change society by overturning old traditions and customs. .

To this end, they introduced, among other things, the Republican calendar in 1793, which included 10 hours per day, averaging 100 minutes per hour and 100 seconds per minute.

In addition to removing the religious influence of the calendar, which made it difficult for Catholics to keep track of Sundays and Holy Days, it helped introduce the decimal system in France.

But while the decimal clock did not advance, the new decimal measurement system, which is the basis of the meter and the kilogram, is still with us today.

The task of creating a new system of measurement was entrusted to the most prominent scientific thinkers of the Enlightenment.

These scholars were eager to create a new unified system based on reason rather than tradition or the will of local authorities.

Therefore, it was decided that the meter should be based on pure nature. It was supposed to be a ten-millionth of the distance between the North Pole and the equator.

The longitude from the pole to the equator, which would be used to determine the length of the new standard, was the longitude of Paris.

This line was drawn by two astronomers who left Paris in 1792: Jean-Baptiste Joseph Delambre, who traveled north to Dunkirk, and Pierre Michen, who traveled south to Barcelona.

They used the latest technology at the time and the mathematical process of triangulation to measure the meridian arc between these two locations at sea level.

Then, after extrapolating the distance between the North Pole and the equator, extending the arc to the ellipse, astronomers agreed to meet within a year in Paris to propose a new global standard for measurement. .

The process ended up being seven years old. Finally, in 1799, Delambre and Méchain presented their results, and on this basis, a one-meter platinum band was created as the basis of the metric system.

As Alder details in his book, measuring this meridian during a time of great political and social upheaval has proven to be an epic task.

The two astronomers have often been greeted with suspicion and hostility. They have fallen into the blessings and the shame of the state. They have even been wounded in combat, including climbing high points such as church domes.

The Pantheon, commissioned by Louis XIV to be a church, became the central geodesic station of Paris – from its dome, Delambre triangulated all 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 another kind of sanctuary – a storehouse of all the old weights and measures that were being sent from cities across France in anticipation of the new order.

But despite all the effort and technology that went into defining the new procedure, no one wanted to use it.

People were reluctant to abandon the old methods of measurement, as they were closely related to rituals, customs and the local economy.

For example, a measurement of alder, of cloth, was usually equal to the width of a household loom, while topsoil was often measured in days, referring to how much land a farmer could prepare. during this period.

The Parisian authorities were so upset by the public’s refusal to abandon the old procedure that they sent police inspectors to the markets to make sure the new system was in place.

Finally, in 1812, Napoleon abandoned the metric system; Although it was still taught in school, people were allowed to use any measurement they wanted until the metric system was reinstated in 1840.

According to Ken Alder, “It took about 100 years for all French people to start using it.

But this is not only due to the perseverance of the state.

France was moving rapidly towards the industrial revolution. Mapping requires more precision for military purposes; And in 1851, the first major world exhibitions were held, during which countries were to present and compare industrial and scientific knowledge.

Of course, that was difficult unless you had clear standard measurements such as meters and kilograms.

For example, the Eiffel Tower was built for the Universal Exhibition of 1889 in Paris, and at a height of 324 meters, it was at the time the tallest man-made building in the world.

All this led to the creation of one of the oldest international institutions in the world: the International Bureau of Weights and Measures (BIPM).

The BIPM is located in the quiet suburb of Sèvres in Paris, surrounded by parks and gardens. Remind me again of your lack of bragging Ladder Place Vendôme ; It may be hidden, but it is fundamental to the world we live in today.

The BIPM was originally created to maintain international standards and promotes the standardization of seven international units of measurement: meter, kilogram, second, ampere (which measures the intensity of electric current), kelvin (the unit of temperature ), mole (amount of substance) and candela (light intensity).

This is where the Platinum Standard Tape Measure is used to carefully calibrate the copies, which are then sent to various other national capitals.

In the 1980s, the BIPM redefined scale as the distance traveled by light in a vacuum within a specified amount of time, making it more precise than ever.

Since then it has been determined by the universal laws of physics and eventually became a nature-based analogy.

The Sèvres building also houses the original kilometer, which is located under three vaults in an underground vault, and which can only be accessed by three different switches, held by three different people.

Now the kilogram is calculated by a so-called Kibble (or Watt) scale, an instrument that compares mechanical and electromagnetic energy using two separate experiments.

This method of measuring the kilogram does not change, it cannot be damaged or lost, as it can happen in the case of a physical body.

Moreover, a definition based on a constant – not an object – makes the exact measurement of the kilogram, at least in theory, accessible to anyone anywhere on the planet, and not just to those with access to the original kilogram stored in France.

As with the 18th century longitude project, determining measurements remains one of our most important challenges.

What started with the metro formed the basis of our modern economy and led to globalization. It paved the way for high-resolution engineering and remains essential to science and research, as well as our understanding of the universe.

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