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What does the French Revolution

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have to do with the time NASA accidentally[br]crashed a $200 million orbiter

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into the surface of Mars?

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Actually, everything.

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That crash happened due to an error

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in converting between [br]two measurement systems,

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U.S. customary units

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and their S.I, or metric, equivalence.

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So what's the connection to[br]the French Revolution?

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Let's explain.

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For the majority of recorded [br]human history,

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units like the weight of a grain[br]or the length of a hand weren't exact

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and varied from place to place.

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And different regions didn't just use[br]varying measurements.

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They had completely different [br]number systems as well.

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By the late Middle Ages,[br]the Hindu-Arabic decimal system

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mostly replaced Roman numerals [br]and fractions in Europe,

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but efforts by scholars like John Wilkins[br]to promote standard decimal-based measures

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were less successful.

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With a quarter million different units[br]in France alone,

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any widespread change would require[br]massive disruption.

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And in 1789, that disruption came.

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The leaders of the French Revolution[br]didn't just overthrow the monarchy.

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They sought to completely [br]transform society

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according to the rational principles[br]of the Enlightenment.

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When the new government took power,

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the Academy of Sciences convened[br]to reform the system of measurements.

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Old standards based on arbitrary authority[br]or local traditions

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were replaced with mathematical[br]and natural relationships.

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For example, the meter,[br]from the Greek word for measure,

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was defined as 1/10,000,000[br]between the Equator and North Pole.

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And the new metric system was,[br]in the words of the Marquis de Condorcet,

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"For all people, for all time."

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Standardizing measurements[br]had political advantages

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for the Revolutionaries as well.

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Nobles could no longer manipulate local[br]units to extract more rent from commoners,

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while the government could collect[br]taxes more efficiently.

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And switching to a new Republican Calendar[br]with ten-day weeks

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reduced church power [br]by eliminating Sundays.

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Adoption of this new system wasn't easy.

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In fact, it was a bit of a mess.

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At first, people used new units[br]alongside old ones,

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and the Republican Calendar [br]was eventually abandoned.

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When Napoléon Bonaparte took power,

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he allowed small businesses [br]to use traditional measurements

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redefined in metric terms.

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But the metric system remained standard[br]for formal use,

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and it spread across the continent,[br]along with France's borders.

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While Napoléon's empire [br]lasted eight years,

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its legacy endured far longer.

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Some European countries reverted[br]to old measurements upon independence.

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Others realized the value [br]of standardization

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in an age of international trade.

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After Portugal and the Netherlands[br]switched to metric voluntarily,

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other nations followed,

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with colonial empires spreading the system[br]around the world.

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As France's main rival,

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Britain had resisted revolutionary ideas[br]and retained its traditional units.

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But over the next two centuries,[br]the British Empire slowly transitioned,

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first approving the metric system[br]as an optional alternative

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before gradually making it offical.

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However, this switch came too late[br]for thirteen former colonies

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that had already gained independence.

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The United States of America stuck with[br]the English units of its colonial past

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and today remains one [br]of only three countries

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which haven't fully embraced [br]the metric system.

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Despite constant initiatives [br]for metrication,

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many Americans consider units like feet[br]and pounds more intuitive.

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And ironically, some regard the once[br]revolutionary metric system

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as a symbol of global conformity.

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Nevertheless, the metric system is almost[br]universally used in science and medicine,

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and it continues to evolve according[br]to its original principles.

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For a long time,

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standard units were actually defined by [br]carefully maintained physical prototypes.

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But thanks to improving technology[br]and precision,

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these objects with limited access[br]and unreliable longevity

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are now being replaced with standards[br]based on universal constants,

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like the speed of light.

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Consistent measurements are such[br]an integral part of our daily lives

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that it's hard to appreciate what a major[br]accomplishment for humanity they've been.

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And just as it arose [br]from a political revolution,

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the metric system remains crucial[br]for the scientific revolutions to come.