An Excerpt from
by Erika Graham ’10
You call me to you, vast and powerful mind,
Minerva of France, immortal Emilie
I awake at your voice, I march to your insights,
In the footsteps of virtues and of the truth.
Emilie was a very unusual woman.
Her full name was Gabrielle-Emilie Le Tonnelier de Breteuil, Marquise du Châtelet, because when she was born in 1706, all French nobles had names longer than themselves! That’s why we’ll call her Emilie. But it wasn’t her name that made her unusual.
It was unusual for a woman born in 1706 to grow up to become a physicist.
But Emilie was unusual. Her father made sure that she got a good education before she got married, and she was able to learn advanced math from some of the best teachers around.
By 1734, she had a castle, Cirey, and she filled one huge room with instruments of all kinds, mathematical, physical, chemical, astronomical, mechanical, and so on. Scientific visitors thought they were dreaming to be in such a room. And Emilie welcomed many scientists to her home.
At Emilie’s castle in Cirey, her visitors worked with her on science, doing experiments and discussing all kinds of theories about the world.
After all, in France in 1734, science — especially physics — was one of the biggest issues of the day. Everyone loved to talk about it, but no one was quite sure how the universe worked:
Why do things fall?
How do things move?
And, while we’re at it,
What makes a thing a thing?
Or rather, everyone was sure how the universe worked. They just didn’t agree.
Mostly, people divided up into teams, with competing ideas about physics. In France, the star player was René Descartes (you say that day-CART). He lived from 1596 to 1650, and had a lot to say about the world.
What did he think? He thought about thinking. Humans are reasonable creatures, so everything could be explained if we just think about it enough. We call this rationalism.
To understand physics, Descartes asked people to think about an imaginary world along with him:
Allow your thought to wander beyond this world to view another, wholly new, world. Let us suppose so much matter all around us that, in whatever direction our imagination may extend, it no longer sees any place that is empty.
Then, thinking about this new world, you could figure out its physics. If all this matter, all the stuff in the new universe, was stirred up like a giant mixing bowl, what would happen? Everything would start moving around, some parts faster, others slower. After a while, things would settle down to look like — THIS.
Since the universe is filled up, nothing moves anywhere without pushing other things away, and those things have to push other bits from their places, and this pushing and shoving continues endlessly. And so, said Descartes, everything moves around in circles. There is no room to spare in the universe, so whenever one part of space wants to shift even a little bit, a whole chain of things has to get moving.
This was a fictional universe, but he said that things worked the same way in our world too. That’s why the solar system chases itself around in a circle. That’s how air fills back in behind an object moving through it.
And that’s the way he found ideas to explain the world; he took a thought that everyone could agree on, then explored what the results had to be. Human reason was pure, not bothered by all the sorts of inaccuracies caused by mistakes in our senses or our measurements. As he said, since we are taking the liberty of imagining this matter as we fancy, let us attribute to it, if we may, a nature in which there is absolutely nothing that everyone cannot know as perfectly as possible.
With the mind, everyone can understand physics. But not everyone agreed, including Isaac Newton.
He was the champion physicist of England, born in 1642 — so he was just 8 when Descartes died. But that didn’t stop him from arguing with Descartes once got old enough. He called Descartes’ physics absurd, fiction, and repugnant to reason. (Physicists could be quite badly behaved back then.) All the universe spinning in circles? Never!
He also didn’t like Descartes’ habit of imagining, either — that wasn’t how science should work! Rationalists were dreamers.
So what did he think? He thought about looking.
The world exists right here in front of our eyes, so why bother making up a fictional world, with the weird sort of physics Descartes threw in, when you could see and change and discover everything that was real? Certainly idle fancies ought not to be fabricated recklessly against the evidence of experiments. Newton liked watching the world. Newton liked experiments. And his experiments taught him that Descartes had it wrong.
He definitely disagreed with Descartes’ hypothesis of vortices, the system where everything in the universe formed into giant whirlpools of matter, including our solar system. Why did he disagree? Because he could see that the planets weren’t moving the way they should.
If the planets went around the sun in one large whirl, and also moved in the center of their own circle of motion because of the matter they pushed aside, they would have to move at a certain speed and go around the sun in a certain amount of time.
Unfortunately for Descartes, they didn’t.
Comets also helped convince Newton that Descartes was wrong. A swirl moving around the sun as evenly as Descartes thought was no place to go finding objects which cut out a strange path. But comets come and go quickly, at odd angles, and certainly aren’t moving in the same kind of orbits as the rest of the planets.
Descartes, for all his logic, had to be wrong.
But not everyone thought so. In fact, most people in France didn’t agree with Newton. They thought he didn’t understand.
Where was his logic?
Where were his causes?
Newton had taken away Descartes’ circles and hadn’t said why. He told people what he saw around him, and talked of forces and motion, but he gave no reason why his system had to be any better than Descartes’.
And, after all, Newton was only an Englishman.
What? Why does that matter?
You may well ask. After all, England and France aren’t all that far apart — doesn’t physics work the same way in both places? If you throw a stone in France, it will hit the ground as well as in England. Ask anyone.
Unfortunately, France and England hadn’t gotten along for a very long time; after the French thought they’d won the physics prize with Descartes, it was hard to let some newcomer take it away.
So, for a while, physics did work differently in France and England — and most of the rest of Europe, for that matter.
Newton died in 1727. Descartes was already long gone. But everywhere, people continued to argue over who was right. Now everyone called physics repugnant to reason and other nasty names — well, the physics they didn’t believe in, anyhow.
Things were getting out of control.