The Meter Convention

Summary

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History Daily: "The Meter Convention"

Episode Air Date: May 20, 2026
Host: Lindsay Graham

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Episode Overview

This episode of History Daily delves into the remarkable story behind the creation of the metric system and the historic Treaty of the Meter, signed on May 20, 1875. Host Lindsay Graham recounts the tumultuous journey from revolutionary France to international standardization, spotlighting the scientists, political turmoil, and societal resistance that shaped the fate of the meter—a unifying force in science and commerce.

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Key Discussion Points & Insights

The Execution of Antoine Lavoisier and the Seeds of the Metric System

[00:39–03:14]

• The episode opens with a dramatic recounting of the execution of Antoine Lavoisier in 1794, a leading chemist and advocate for modern measurement.
• Lavoisier’s legacy includes his discovery of oxygen and his push for a universal measurement system to prevent confusion and fraud.
• His execution is painted as a dark omen for scientific progress:

  “Despite being one of France’s greatest scientists, Antoine has been locked away in prison for months. And now his past ties to the deposed king Louis XVI have sealed his fate.” (Host, 00:39)

Jean Baptiste Delambre’s Mission and Revolutionary France

[04:45–10:33]

• In 1792, Jean Baptiste Delambre and Pierre Méchain are commissioned to measure the Earth to define the meter as 1/10,000,000 of the distance from pole to equator.
• The revolutionary climate places scientists in danger as they’re seen as remnants of the aristocracy; Delambre faces accusations of espionage during his measurement expeditions.
• The initial mandate for the metric system in France faces confusion:

  “In village after village, Jean Baptiste explains how there are currently hundreds of measurements in France… it’s a recipe for confusion and fraud. But a single shared measuring system could transform people’s lives.” (Host, 07:22)

• Political purging interrupts scientific work. Delambre is forced off the project in 1794 but later reinstated as the government resumes support for a precise standard.

The Birth and Early Resistance to the Meter

[12:40–17:16]

• By 1799, the first platinum meter bar is unveiled in a ceremonial event, with international observers invited to spread the metric system.
• Initial public and political resistance is immense:

  “Most French citizens still resist. Not because they want to cling to royalist traditions, but because old habits are hard to break.” (Host, 13:47)

• Even Napoleon opposes the metric system, finding it impractical. The government attempts enforcement, but popular usage remains tied to old units.
• Napoleon eventually introduces a hybrid system in 1812, effectively shelving pure metric measures. The metric system becomes “an unloved and almost forgotten relic of the revolutionary era.” (Host, 16:19)

The Metric System’s Revival and Internationalization

[16:20–22:17]

• The revolution of 1830 breathes new life into the metric system. By 1837, France officially reinstates it, now as a symbol of progress and equality.
• Over the next decades, more countries adopt the system, but without unified standards, variations persist, causing international confusion.

The 1875 Meter Convention: Toward a Universal System

[19:24–22:17]

• On May 20, 1875, representatives from 17 countries convene in Paris to solve discrepancies in standards and sign the Treaty of the Meter.
• The International Bureau of Weights and Measures is established, tasked with maintaining and distributing the official measure of the meter and kilogram:

  “This convention will mark a profound shift toward a truly global system of measurement, one born from revolution, refined through science and now made possible by diplomacy.” (Host, 21:04)

• Despite global adoption trends, the United States resists the switch, persisting with traditional measurements into the 21st century.

  “Of the three, America alone will carry its resistance into the 21st century, remaining a stubborn exception to a global movement that was launched in Paris on May 20, 1875.” (Host, 21:53)

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Notable Quotes & Memorable Moments

• On Revolutionary Danger:

  “In revolutionary France, no amount of scientific achievement can protect you.” (Host, 09:37)

• On the Meter’s Definition:

  “They're measuring a slice of it, a meridian arc… by calculating its length, they can estimate the size of the Earth. And from that, they'll define a new unit of measure, the meter. 1/10,000,000 of the distance from the North Pole to the equator.” (Host, 05:09)

• On Resistance:

  “Even France’s rising young leader, Napoleon Bonaparte, refuses to adopt the metric system, claiming it’s too difficult to think in metric units.” (Host, 14:19)

• On International Cooperation:

  “The gathered delegates hope to solve that problem. Together, they propose the creation of an international body… the International Bureau of Weights and Measures.” (Host, 19:44)

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Timestamps for Key Segments

• [00:39–03:14]: Execution of Antoine Lavoisier and its impact on science
• [04:45–10:33]: The beginnings of the meridian survey and the perils of revolutionary France
• [12:40–17:16]: Introduction and rocky implementation of the meter, public resistance, and Napoleon’s hybrid measures
• [19:24–22:17]: The Meter Convention, establishment of international standards, and global legacy

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Conclusion & Legacy

This episode captures the dramatic, often perilous, journey toward a unified system of measurement—an achievement painstakingly realized through scientific inquiry, political upheaval, and, ultimately, international cooperation. The adoption and protection of the metric system emerge not just as a victory for science, but as a telling indicator of changing global attitudes toward shared standards, the persistence of tradition, and the hope for universality.

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For anyone interested in how a simple ambition for measurement clarity became a revolutionary—and then global—phenomenon, this episode provides a vivid, accessible, and engaging retelling.

Transcript

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It's May 8, 1794, in Paris, France, five years into the French Revolution. On the back of a battered cart, 50 year old scientist Antoine Lavoisier hunches down, trying to shield his face as he passes. The angry crowd lining the street shouts insults at him and hurls rotten vegetables, rocks and clumps of mud in its direction. Despite being one of France's greatest scientists, Antoine has been locked away in prison for months. And now his past ties to the deposed king Louis XVI have sealed his fate. Antoine has just been convicted as a traitor to the revolution. And now execution awaits. The cart bumps and rattles over the cobblestones, drawing closer and closer to the scaffold. Finally, it jerks to a halt in a wide public square. Seething with spect, Antoine stumbles as he's pulled from the cart. The guards grip his arms, guiding Antoine's trembling legs to the scaffold. There, the executioner and his guillotine await. Antoine is pushed to the ground and forced to kneel, and his head is placed beneath the blade. An eerie silence falls over the crowd, and for a brief moment, everything goes still. But then comes a creak of wood, a rustle of rope, and the blade falls, cutting short Antoine's life, work and legacy in one swift, unforgiving stroke. The execution of the influential Antoine Lavoisier will send shockwaves through Paris scientific community. Antoine had discovered and named the element oxygen, and he had tried to push science toward more precise methods through the use of a new system of measurements. His death will cast a dark shadow over the future of both chemistry and the metric system that he championed. But Antoine's work will not be in vain. It will take nearly a century, but his dream of a shared international system of measurement will finally be realized on May 20, 1875. There are still some places left on my European Christmas market tour. A winter wonderland whirlwind throughout France, Germany and Austria. We'll drink mulled wine, eat good food and visit some of the most consequential historical sites in Europe. I'm really looking forward to it and you can join me, but only if you act quickly. Over half of all available places are already taken. Tickets are on sale now, so reserve your spot. Go to historydaily.com and look for the Christmas market section. That's historydaily.com

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from Noiser and Airship, I'm Lindsey Graham and this is History. Daily. History is made every day on this podcast. Every day we tell the true stories of the people and events that shaped our world. Today is May 20th, 1875. The meter convention. It's June 1792. On the streets of Paris, two years before the execution of the scientist Antoine Lavoisier, 42 year old Jean Baptiste Delambre climbs into a carriage packed with instruments, its wheels groaning under the weight of the equipment. He tugs the door shut, the horses lurch forward, and Jean Baptiste feels a jolt of excitement. If all goes to plan, this is the start of a historic scientific expedition. Jean Baptiste is one of two astronomers who have been commissioned to measure the globe more precisely. They're measuring a slice of it, a meridian arc, the curved line that runs from Dunkirk in northern France through the capital, Paris, and all the way to Barcelona. By calculating its length, they can estimate the size of the Earth. And from that, they'll define a new unit of measure, the meter. 110 millionth of the distance from the North Pole pole to the equator. Jean Baptiste and his peers at Paris Academy of Sciences hoped that the meter would become a universal measure, the base for a new metric system that all of France and even the world can share. It's an ambitious goal, and it's also one that will plunge Jean Baptiste into danger. Because France is in turmoil, King Louis XVI has been imprisoned in his palace. Many of his aristocrats have been exiled or executed. And a republican movement is growing in strength. Amid the chaos, scientists like Jean Baptiste have become vulnerable. For years, they've relied on the patronage of the upper classes to support their work. But now their ties to the establishment risk turning them into potential targets. And as Jean Baptiste crisscrosses the French countryside taking measurements, he's met with suspicion. Everywhere he goes, his strange equipment sparks accusations of espionage, and Jean Baptiste is repeatedly forced to defend his mission. In village after village, Jean Baptiste explains how there are currently hundreds of measurements in France. Different trades and different regions use different standards. It's a recipe for confusion and fraud. But a single shared measuring system could transform people's lives, facilitating commerce and connection between all French people. This argument seems to sway his doubters, and for several months, Jean Baptiste continues his work, interrupted only by poor weather. But while he takes the careful measurements needed to create the meter on the streets of Paris, the Revolution is gaining momentum. In January 1793, the French king is executed and a republican government takes his place. Soon after, radical politicians call for the dissolution of all royal institutions, including the Academy of Sciences. It seems that the Academy's meridian survey seems doomed. But then it gets an unexpected reprieve. The new French government not only embraces the survey, it passes a new law mandating the use of the metric system. The people of France are given one year to prepare, with a provisional estimated meter to be used until Jean Baptiste and his team produce the definitive measurement. But Jean Baptiste has not dispelled all suspicions about his work. And in the first week of 1790, 4. He is removed from the Meridian Survey. In the eyes of the revolutionaries now in power, Jean Baptiste has failed to prove his loyalty to the new regime, and he must be purged. Jean Baptiste is ordered to hand over all his field notes, calculations and instruments. The news devastates him. But Jean Baptiste does as he's told, too scared to defy France's new leadership. Back in Paris, the new government rules with fear and bloodshed. And upon his return, Jean Baptiste learns that the acclaimed scientist and fellow proponent of the metric system, Antoine Lavoisier, has already been arrested. His imprisonment sends a clear message to Jean Baptiste and his in revolutionary France, no amount of scientific achievement can protect you. In this climate of fear, the Meridian Survey is no longer a priority. The leaders of the revolutionary government decide they can make do with a provisional but less accurate meter. What matters most is getting the entire country working from one system of measurement. But by the time the mandatory adoption date arrives, few French citizens know or care about the new metric system. Even public officials continue filing reports in the old units. The government tries to turn things around, condemning the previous system of measurement as obsolete and a relic of the old regime. It urges citizens to embrace the new metric system, but their appeals are largely ignored. So for a time, the metric system seems destined for obscurity. But then, in 1795, Jean Baptiste receives an unexpected opportunity to revive it. France's leaders have had a change of heart. They decide that if the meter is to have real authority, it must be based on fresh, precise data, not the outdated estimates behind the provisional meter. So they order Jean Baptiste to resume his work, this time with their full support. Jean Baptiste will spend three more years on the road taking precise measurements before his mission is complete. And upon his return to Paris, France will prepare to reintroduce the meter, and not just to its citizens, but to the entire world.

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It's June 22, 1799, in Paris, seven months after the meridian survey was completed. Inside a lecture hall in France's National Archives, a grand ceremony is underway. Physicist Pierre Simon Laplace stands before a room of French lawmakers and scientists from around the world. In front of Pierre Simon, resting on a velvet draped table, is a newly forged platinum bar, exactly 1 meter long. Pierre Simon gestures proudly to the bar as he speaks, hailing it as the crowning achievement of a decade of labor. He describes the long expeditions that were needed to create this new unit of measurement. Then, with a sweep of his hand, he pulls away a sheet to reveal a second set of bars. These are made of iron, but each is also precisely 1 meter long. Pierre Simon smiles and invites the foreign visitors to take a bar home. Carrying the metric system beyond France's borders and out into the world, the metric system promises to transform the economy and simplify daily life if it's adopted. So in the months after this ceremony, the French government pushes hard to ensure that the new meter is embraced. The legislature orders its citizens to start learning the metric system, and schools are forced to teach the new measurements. But most French citizens still resist. Not because they want to cling to royalist traditions, but because old habits are hard to break. Even France's rising young leader, Napoleon Bonaparte, refuses to adopt the metric system, claiming it's too difficult to think in metric units. Meanwhile, a new problem emerges. In 1804, Pierre Mechon dies. Pierre was part of the team tasked with surveying the meridian back in the 1790s. And while Jean Baptiste d' Alambre was responsible for measuring between Dunkirk and Rodez in the south of France, Pierre traced the rest of the ark to Barcelona. And after Pierre's death, Jean Baptiste goes through his former colleagues data and records from the expedition. That's when he discovers some discrepancies. These inconsistencies mean that their calculations were inaccurate. The meter that Pierre and Jean Baptiste spent nearly a decade defining is wrong. It isn't 1/10 millionth of the distance from the North Pole to the equator. It's off by about 0.02%. Disappointed, Jean Baptiste shares his findings with his colleagues. But in the end, they agree that it's better to leave the error buried. Another revision to the meter could destroy what little faith the public has in the metric system. So instead, they focus on boosting adoption. The government ramps up production of metric rulers to 300,000 a year. Police are ordered to punish those who refuse to use the metric measures. And new, more detailed conversion charts are printed and circulated to help those more accustomed to the old ways adapt. But all these efforts fail. Most people continue trading in the old units, and soon rumors spread that the government will abandon the metric system altogether. In 1812, that gossip becomes reality. With his attention focused on foreign conquest, Napoleon Bonaparte needs to minimize economic turmoil at home. So on February 12th of that year, he introduces a the ordinary measures. This new, new system officially keeps the meter as its foundation. But for everyday use, it allows people to draw from more familiar pre revolutionary units. Pierre Simon is one of the scientists who lobby against this decision. He pleads with Napoleon to preserve the metric system. He even tries to win him over by offering to rename the system as the Napoleonic Measures. But Napoleon refuses. And even after Napoleon's Reign collapses in 1815 and the French monarchy returns to power, the metric system stays buried for over a decade. The meter remains an unloved and almost forgotten relic of the revolutionary era. But in 1830, a new uprising rocks France. Angry over political repression and and economic hardship, the people rise up against their king once again. And after three days of fierce fighting in the streets of Paris, the king abdicates. This 1830 revolution will bring a wave of reform to France, and with it, a fresh look at the metric system. And for the new government, this system will be more than a tool of measurement. It will be a symbol of equality, science and progress values that this new generation of revolutionaries long story to restore. So in 1837, France will officially reintroduce the metric system. And this time, it will stick.

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It's May 20, 1875, in Paris, France, 38 years after France reintroduced the metric system. Inside a conference room, delegates from 17 countries across Europe and the Americas take their seats around a long table, eager to discuss a radical initiative. Since France made the metric system mandatory again in 1837, other nations have slowly begun to adopt it. But without a single authority to oversee standards, discrepancies remain. Different countries have slightly different standards for the meter and kilogram, and these minor variations have caused major confusion, especially as international trade and scientific research have expanded. So today, the gathered delegates hope to solve that problem. Together, they propose the creation of an international body, a permanent organization tasked with maintaining UN universal standards for measurement. They will call it the International Bureau of Weights and Measures. By the end of the day, the diplomats sign the Treaty of the Meter, agreeing to establish a set of exact shared measures. Under the treaty, the new bureau will build official standards of the meter and kilogram, store them under strict conditions, and distribute identical copies to participating countries. This convention will mark a profound shift toward a truly global system of measurement, one born from revolution, refined through science and now made possible by diplomacy. Over the next few decades, the metric system will continue to expand its reach, driven by the needs of science, industry and global trade. Countries not represented in the convention will begin the transition to the meter, but there will be one major exception. Out of all the nations that did sign the Treaty of the Meter, only the United States will fail to fully adopt the metric system. While the rest of the world continues to move toward at least partial metrification, the U.S. liberia and Myanmar will cling to their traditional measures. Of the three, America alone will carry its resistance into the 21st century, remaining a stubborn exception to a global movement that was launched in Paris on May 20, 1875. Next on History Daily May 21, 1871 an assault by French troops to retake Paris from revolutionaries leaves the city in ruins. From Nouser and Airship. This is History Daily Hosted, edited and executive produced by me, Lindsey Graham Audio editing by Mohammad Shahzid Sound design by Molly Bach Supervising Sound Designer Matthew Filler Music by Thrum this episode of is written and researched by Alexandra Curry Buckner Edited by Scott Reeves Managing Producer Emily Burke Executive producers are William Simpson for Airship and Pascal Hughes for Nouser.

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