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  • One of the problems with the whole idea of a single Scientific Revolution is that some

  • disciplines decided not to join any revolution.

  • And others just took a long time to get there.

  • In the case of chemistrythe study of what stuff is—a real scientific revolution, like

  • in the Thomas Kuhn sense, didn't really get going until the 1770s.

  • Until then, mainstream chemistry in Europe was based on phlogiston theory, which may

  • be difficult to wrap your head around because it is the opposite of how we understand chemical

  • reactions today.

  • To shake loose that particular scientific status quo, it took the power of the Enlightenment,

  • and one of its most emblematic natural philosophers, Lavoisier.

  • [Intro Music Plays]

  • If the 1600s was the century of science in Europe, centered on London, then the 1700s

  • was the century of philosophy, centered on Paris.

  • This new philosophy largely consisted of a movement called the Enlightenmentdated

  • by some from 1715, when France's powerfulSun King,” Louis the Fourteenth, died,

  • to 1789, when the French Revolution started.

  • The Enlightenment was a shift in ideas about knowledge, away from traditional sources of

  • authority, like the Church, and toward the kind of scientific rationality described by

  • Bacon.

  • This aspect of the Enlightenment is summed up by the catchphrase sapere aude, ordare

  • to know.”

  • This suggested that knowing is something you should do—a moral good.

  • This was anAge of Reason.”

  • The Enlightenment was also about social values, such as individual liberty, the progress of

  • civilization, and religious tolerance, including the separation of church and state.

  • The Enlightenment at times even fed into anti-religious, specifically anti-Catholic, feelings, setting

  • the stage for a later perceived break between science and religion.

  • The termEnlightenmentwas coined by German writer Johann Wolfgang von Goethe,

  • and it was used by Voltaire, and later by Kant.

  • Thinkers like themcalled les philosophes, orthe philosophers”—met in scientific

  • societies, literary salons, and coffeehouses.

  • The philosophes saw it as their job to discover the laws of naturethe natural law that

  • helped guide human behavior.

  • They dreamed of a “republic of letters,” a world ruled by rational thought and guided

  • by reasoned debate.

  • So, yes, if you remember episode two: the philosophes were kinda like the Presocratics.

  • The ideas of the Enlightenment undermined the authority of kings and churches and helped

  • set the intellectual stage for the soon-to-come revolutions in the United States, France,

  • and Haiti.

  • But the Enlightenment was also about increasingly centralized state power and colonization of

  • non-Europeans, which we talked about two episodes ago.

  • Statistics, for example, was developed at this time to serve the interests of nation-states

  • and early corporations.

  • So we can also call this the Age of Empire

  • Perhaps no object better represents the Enlightenment than the ambitious book named the Encyclopédie.

  • Edited by Jean d'Alembert and Denis Diderot from 1751 to 1777, the twenty-two volume Encyclopédie

  • attempted to organize literally all of the knowledge available to humanity.

  • Basically...

  • Wikipedia!

  • The Encyclopédie physically demonstrated three big ideas: First, knowledge is cumulative.

  • Humans add new knowledge to our collective pool all the time.

  • Second, knowledge is recordable.

  • We can transmit knowledge through things like books.

  • And third, knowledge is political.

  • Diderot, like Bacon, believed that knowledge should be used to alleviate human misery.

  • Diderot hoped tochange the general way of thinkingby popularizing recent achievements

  • in science and technology and combating superstition.

  • He wanted to use knowledge to help people out.

  • He also thought that all traditional beliefs should be reexaminedwithout sparing anyone's

  • sensibilities.”

  • But strict censorship by the state made any explicitly anti-religious articles impossible,

  • so Diderot had to cleverly slip in critiques of the church.

  • For example, in the cross-reference for the entry on the Eucharist: “see cannibalism.”

  • Now, the Encyclopédie systemized knowledge in a neat way, but it was largely qualitative,

  • describing things according to valuesfor example, what a good ship looks like.

  • But Enlightenment thinkers increasingly dreamed of quantification, or describing things in

  • numberslike units of length, mass, heat, and so on.

  • But for quantification to work, you have to have an agreement about how to measure things.

  • In other words, you have to have standards.

  • The meter, for example, was defined by a commission of scientists in France in the 1790s as one

  • ten-millionth of the earth's meridian through Paris.

  • The commission included Pierre-Simon Laplace, who wrote the five-volume

  • Celestial Mechanics, starting in 1799.

  • This greatly expanded Newton's work on classical mechanics, opening up a range of topics to

  • the problem-solving power of calculus.

  • Celestial Mechanics became a sort of Principia - volume two.

  • And in order to actually measure the meter, the commission sent out two guys, Pierrechain

  • and Jean-Baptiste Delambre, to make measurements.

  • ...I'm not good at French.

  • This was a time of widespread war in Europe.

  • chain and Delambre struggled against skirmishes, yellow fever, and imprisonmentbut they

  • got the job done.

  • And along with standards, measurement required new instruments, like the barometer and electrometer,

  • as well as new ways of interpreting data, AKA statistics, which were also pioneered

  • by Laplace.

  • By the end of the eighteenth century, physics was already well on its way to rationalization,

  • quantification, and even standard measurement.

  • But what about chemistry?

  • In the late 1700s, natural philosophers believed that chemical reactions occurred thanks to

  • an ether—a colorless, odorless, “self-repulsive,” extremely fine, and therefore hard-to-measure

  • fluidcalled phlogiston.

  • According to phlogiston theory, this ether was released during combustion.

  • For example, a burning candle was thought to release phlogiston.

  • If you covered that candle with a jar, the flame would go out, because the air would

  • become saturated with phlogiston and couldn't absorb any more.

  • This is exactly the opposite of how we now understand it: that the flame goes out because

  • it's used up all of the oxygen, which is necessary for a chemical reaction.

  • Likewise, it was thought at the time that, when plants grew, they absorbed phlogiston

  • from the air.

  • When their wood was burned, it released phlogiston back into the air.

  • Or when we ate them, our bodies released phlogiston through respiration and body heat.

  • In this system, “phlogisticated airorfixed airwas what we would now call

  • carbon dioxide.

  • Joseph Black isolated fixed air in 1756.

  • Dephlogisticated air,” on the other hand, was oxygen.

  • This system worked pretty well to explain chemical reactions qualitativelywhy they

  • seemed to appear a certain waybut no one could quantify phlogiston.

  • And minor anomalies in phlogiston theory kept adding up.

  • For example, mercury gained weight during combustion, even though, by releasing phlogiston,

  • it should have lost weight.

  • The person who changed chemistry from a qualitative discipline to a quantitative one was Antoine-Laurent

  • de Lavoisier.

  • A good example of an Enlightenment natural philosopher, Lavoisier was born to a noble

  • family in Paris in 1743.

  • He studied law but was obsessed with geology and chemistry.

  • Lavoisier also worked on the metric system.

  • Lavoisier first presented research on chemistry, in a paper about gypsum, to the French

  • Academy of Sciences in 1764.

  • In 1768, the Academy made Lavoisier a provisional member.

  • Two decades later, he would become the founder of thenew chemistry,” revolutionizing

  • the entire discipline.

  • ThoughtBubble, show us what this means: Lavoisier knew phlogiston theory well.

  • But he began his chemical research with

  • the hypothesis that, during combustion, something is taken out of air rather than put into it.

  • That hypothesis turned out to be correct, and that something turned out to be oxygen.

  • Lavoisier's tested his hypothesis by accounting for inputs and outputs in chemical reactions—a

  • perfect example of the eighteenth-century quantification of science.

  • And Lavoisier also discovered that the mass of matter remains the same even when it changes

  • form or shape.

  • Which is very important!

  • Working carefully over years, he generated the first modern list of elements.

  • He named oxygen in 1778, hydrogen in 1783, and siliconmerely a prediction at that

  • pointin 1787.

  • In fact, Lavoisier and his allies developed a whole new nomenclature for chemistry, in

  • 1787.

  • Inflammable airbecame hydrogen.

  • Sugar of Saturnbecame lead acetate.

  • Vitriol of Venus”—which had also been called blue vitriol, bluestone, and Roman

  • vitriolbecame copper sulfate.

  • Yeah, the new naming system was less fun than the old one.

  • But it was more rational: the terms better described the underlying

  • stuff they pointed to.

  • Copper sulfatemeant a compound of sulfur and copper.

  • Lavoisier published the textbook Elementary Treatise of Chemistry in 1789, which taught

  • only the new chemistry.

  • In the introduction to his book, Lavoisier also separated heat and chemical composition.

  • So water is water whether it's heated up to steam or cooled down to ice.

  • He understood that heating something up doesn't always change what it is, fundamentally.

  • To explain these state changes, Lavoisier made up a new ether, which he called the

  • caloric.

  • Caloric could penetrate a block of ice, melting it into water by pushing the ice particles apart.

  • Thanks Thought Bubble.

  • Spoiler: caloric is not thought to be a real thing today.

  • (Many people wish calories weren't real, but, here we are.)

  • Led by the prominent English chemist Joseph Priestley, these old-timers kept modifying

  • phlogiston theory so that it could rationally account for chemical reactions without falling

  • apart, due to the whole phlogiston-in versus oxygen-out thing.

  • Well into the 1780s, many chemists still believed in phlogistonwhich no one had

  • actually seen or measuredsimply because it was familiar.

  • What changed their minds?

  • Well, Lavoisier and his allies published results that favored their system.

  • But more importantly, the students who learned from them could only speak the language

  • of the new chemistry.

  • The phlogiston believers were increasingly isolated.

  • Thus in a couple of decades, phlogiston moved from the center of chemistry into exile.

  • With the new chemistry, Lavoisier brought the discipline into the system of rational,

  • experimental science dreamed up by methodologists such as Bacon and fleshed out by Newton.

  • Outside of chemistry, Lavoisier was a noble with a powerful state job: he worked at the

  • hated tax collection agency of the French kingdom, known for being both secretive and

  • violent.

  • He profited from his job there, helping fund his chemical research.

  • But the French Revolution broke out in 1789, and being an aristocratic tax collector was

  • not a good look.

  • Lavoisier was tried for defrauding the people of France.

  • And the judge denied the appeal to save his life, despite his immense contributions to

  • knowledge, declaring that: “The Republic needs neither scientists nor chemists; the

  • course of justice can not be delayed.”

  • Lavoisier died by guillotine in 1794.

  • His friend, mathematician Joseph-Louis Lagrange, said of Lavoisier's death: “It took them

  • only an instant to cut off his head, but France may not produce another such head in a century.”

  • Now, how was Lavoisier so successful at setting up the new chemistry as a paradigm?

  • Well, he had a lot of support!

  • Marie-Anne Pierrette Paulze, AKAMadame Lavoisier,” was born into a noble family

  • in south-central France in 1858.

  • And she contributed significantly to Antoine's work.

  • She translated his texts into English, and after Antoine's death, she published his

  • complete papers, securing his legacy in the field.

  • Madame Lavoisier eventually remarried another scientist, Count Rumford, a physicist who had a role in shaping

  • thermodynamics.

  • But she insisted on keeping Lavoisier's name to show her allegiance to the man she

  • loved.

  • Also, Madame Rumford is way less cool.

  • After the Lavoisiers, a new generation of thinkers continued to develop their ideas,

  • in France and beyond.

  • Notably, John Dalton observed that the ratio of elements in reactions were often made up

  • of small numbers, meaning that chemical elements are in fact discrete particles, not fluids.

  • He called these particles chemical atomstrue indivisible units.

  • And Joseph Fourier published the Analytical Theory of Heat in 1822, using calculus to

  • describe how heat flows.

  • Fourier also discovered the greenhouse effect, or the capture of the sun's radiation in

  • the earth's atmosphere.

  • Next timewe'll classify plants' sexy parts, disintegrate a willow tree, and debate

  • whether whole species cango extinct.

  • Join us for biology before Darwin!

  • Crash Course History of science is filmed in the Dr. Cheryl C. Kinney studio

  • In Missoula, MT. And it's made possible with the help of all these nice people.

  • And our animation team is Thought Cafe.

  • Crash Course is a Complexly production.

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One of the problems with the whole idea of a single Scientific Revolution is that some

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