**A noble lady's place is in the natural philosophies. **

The Enlightenment Era is thought of by some people as one of the most exciting times there was to be a scholar. It was a time when rigorous scientific inquiry was just starting to gain steam in Europe, and math and philosophy were flourishing.

You might be familiar with some famous names from then-- like Newton, Euler, and Voltaire, who are just a few of the well-known physicists, mathematicians, and writers of the era. But there’s another brilliant scholar whose life and work intersected with all of these famous men, but whose name you probably have never heard before: Émilie du Châtelet.

“In a time when women were not given the same freedoms and education, Émilie du Châtelet successfully fought her way into a circle of intellectuals that was closed to all but a small group of men-- even if she had to occasionally dress in men’s clothing to do so.”

Watch the video or continue reading below!

**Émilie's Unique Education**

Born into a noble French family in the early 1700s, Émilie grew up surrounded by intellectuals. Her dad, a secretary to the king, would hold weekly parties for authors and scientists in the bustling city of Paris. Émilie’s dad also encouraged her own curiosity. He hired private tutors for her in subjects that, at the time, were considered very strange for a girl to learn, including Latin, Greek, math, astronomy, and even fencing!

Émilie had a special talent for math that showed itself early on. Very soon she figured out a way to take advantage of her mathematical gifts. As a young teenager, when she found she had no money left to buy books, Émilie calculated a new strategy to win money by gambling, and earned enough at the card tables to buy as many books as she wanted.

**A Natural Philosopher**

Émilie du Châtelet grew up in a time when academics were more fluid, and scholars spent time thinking about many different subjects. Science as we know it was not divided so clearly into biology or chemistry or physics, but was instead called natural philosophy.

Natural philosophy was studied by people who were *also* authors and philosophers; many scholars of the time would run experiments in between writing novels and essays. Émilie likewise held this interdisciplinary way of thinking, and spent her life working on complex problems in mathematics, conducting physics research, and writing and translating books.

In her studies and work in mathematics, she exchanged letters with famous mathematicians from all around Europe, including some early developers of calculus. Once, Émilie attempted to meet with one of these mathematicians in a Parisian cafe, a popular spot for intellectual discussion at the time.

When she showed up to her meeting, however, she was turned away at the door because she was a woman. But Émilie was too determined and refused to be kept out: she dressed up in a man’s suit, and snuck in in disguise!

"It is important that we recognize du Châtelet for her own brilliance! She was a great scholar and a bold, passionate person."

Many of Émilie du Châtelet’s most academically productive years were spent living with one of her greatest romantic and intellectual partners, Voltaire. Du Châtelet and Voltaire spent several years living in the French countryside together, writing and running science experiments in their basement. This caused a bit of a scandal, since du Châtelet was married to another man at the time! Voltaire, a famous author and philosopher, thought of du Châtelet as his muse, and for a long time historians remembered her only as Voltaire’s mistress. Recently, we’ve come to realize just how much Émilie du Châtelet accomplished in her own right, and to finally appreciate her as her own scholar.

**A Kinetic Discovery**

In addition to her studies of mathematics, du Châtelet used her expertise in languages to translate some very important scientific works into French. Her most famous translation is Newton’s Principia, translated from Latin into French.

You may have heard of some of Newton’s ideas in your science classes-- he formalized concepts of forces and acceleration, of inertia and gravity. Du Châtelet’s translation of his work into French spread these ideas to the European continent and undoubtedly sparked many advancements in science. The work was more than just a direct translation of Newton’s text, though! Du Châtelet added some of her own ideas and derivations, too, including the very first derivation of the **Law of Conservation of Energy**.

Du Châtelet was the first to theorize that the total energy of an object is conserved... Isaac Newton at the time thought kinetic energy was exactly proportional to velocity, but we now know that Émilie du Châtelet was right: kinetic energy is equal to one half times the mass times the velocity squared!

Conservation laws are some of the most important laws we have in physics. They let us figure things about complicated systems (like the motion of colliding galaxies or colliding particles) by using a really elegant statement about what must be true at the beginning and end of each collision.

Du Châtelet was the first to theorize that the **total energy of an object is conserved**, and that the energy due to the motion of the object-- kinetic energy -- is just one form of energy which can be transformed into other forms of energy. She even did her own experiments to discover the relationship between kinetic energy and the speed of the object. She dropped heavy balls into clay, and looked at how deep the balls went into the soft material.

She realized that the depth the ball fell in the clay depended on the square of the velocity: for example, balls moving three times as fast had nine times the energy.

Isaac Newton at the time thought that kinetic energy was exactly proportional to velocity, but we now know that Émilie du Châtelet was right. **Kinetic energy is equal to ½ m v^2**!

**Found in Translation**

For many years, people thought of Émilie du Châtelet only in respect to the more famous men around her. She was remembered as the translator of Newton’s great work, or as Voltaire’s girlfriend and muse. But it is important that we recognize du Châtelet for her own brilliance! She was a great scholar and a bold, passionate person. In a time when women were not given the same freedoms and education, Émilie du Châtelet successfully fought her way into a circle of intellectuals that was closed to all but a small group of men-- even if she had to occasionally dress in men’s clothing to do so.

Photos courtesy of Wikimedia Commons

Written by Caroline Martin

Edited by Ella King and Taylor Contreras

Illustrations by Ann Wang

Portrait by: IG @s_c_r_u_b_y

**Primary source and additional reading**:

__Du Châtelet (1706-1749)__ by Project Vox

**Learn more about the science Émilie explored!**

**Remember (5-15 minutes)**: __Word search__

**Expand (30-60 minutes)**: Émilie was fascinated by kinetic energy, meaning the energy of an object due to its motion. Explore kinetic energy with this __skate park simulator__.

**Investigate (1-1.5 hours)**: __Recreate Émilie's experiment__ she used to determine kinetic energy is proportional to the velocity *squared*.

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