Emilie du Chatelet

Émilie du
Châtelet
Jo Sibley
Gabrielle Émilie Le Tonnelier de
Breteuil, marquise du Châtelet
17 December 1706 – 10 September 1749
• Born Gabrielle Émilie Le Tonnelier de Breteuil, the daughter
of a lesser French nobleman in the court of Louis XIV.
• Married by arrangement, aged 18, to Marquis FlorentClaude du Chastellet-Lomont, thus becoming the Marquise
du Chastellet.
• Bore him three children, died following the birth of her fourth
child.
“love of learning is the
most necessary passion ...
in it lies our happiness.
It's a sure remedy for
what ails us, an unending
source of pleasure.”
Du Châtelet’s early education
Probably attended a Paris convent school, where she
learned Italian, Latin and English, as well as appropriate
etiquette for her état.
Her father provided tutors for her, significantly family friend
M. de Mezieres, who fostered her interest in mathematics.
Du Châtelet maintained her interest in mathematics,
philosophy and physics and sought an education in these
with renewed vigour following the birth of her first three
children.
Du Châtelet’s education
Du Châtelet studied under Pierre Louis de
Maupertuis, renowned mathematician and
astronomer of the time.
The subject of the infinitely
small led her to a dispute with
tutor Samuel Koenig. Later, this
exacerbated a dispute over her
book, Institutions de physique.
Alexis Clairaut became Du Châtelet’s
tutor from 1735. His work with
Maupertuis, argued against Newton’s
model of the shape of the Earth.
“If I were king, I would redress
an abuse which cuts back, as it
were, one half of human kind.
I would have
women
participate in all
human rights,
especially those
of the mind.
Du Châtelet’s passions
The marquise was determined not to
let society’s bias against her gender
get in the way of her studies.
As was the way of the time, having
provided heirs for her husband, she
took a series of lovers, most
importantly the scandalous
playwright, Voltaire.
Their passionate affair matured into a lifelong working
relationship, with Voltaire living for much of the time at the
Du Châtelet residence, Chateau de Cirey.
Du Châtelet’s passions
The marquise was formidable in
debate, and was an advocate for
education for women, especially
for French women to receive a
secondary education as she had;
unusual for the time.
She was an accomplished
gambler, devising a version of
‘derivatives’ to raise money to pay
for her gambling habits.
Du Châtelet’s work
Du Châtelet and Voltaire built a
huge library together at Cirey
and performed experiments
together investigating the
nature of fire.
This frontispiece from Voltaire’s
work on Newton’s philosophy
shows the Marquise as his
muse, reflecting the light of
Newton’s inspiration onto his
writing desk.
Du Châtelet’s work
In 1737, Du Châtelet published a
paper; ‘Dissertation sur la nature
et la propagation du feu’, based on
her research with Voltaire at Cirey.
The paper predicted the existence
of infrared radiation.
Du Châtelet’s work – kinetic energy
In the early 18th
century the idea
of energy, as a
transferable currency
between different
systems, was still in
its infancy, with
momentum instead
being the focus of
attention.
We now know that the total momentum of a system is
conserved; none is lost to friction. Momentum cannot transfer
between different forms; there is no potential momentum.
Du Châtelet’s work – kinetic energy
Mechanical energy, kinetic and potential, may be lost to
another form, but the total is conserved in time.
Mme. du Châtelet’s contribution was the hypothesis of the
conservation of total energy, as distinct from momentum.
The verification that Kinetic energy is  mass(velocity)2
came from Du Châtelet’s reworking of Leibniz’s ideas, using
an experiment by Gravesande.
Gravesande experiment
Du Châtelet’s work – kinetic energy
Re-creating the
experiment in the
classroom:
• Constant acceleration
due to gravity
• If dropped from rest
from a height H, the
speed on impact is
 𝐻
GCSE
Kinematics
opportunity!
Du Châtelet’s work – kinetic energy
Re-creating the experiment in
the classroom:
• Constant acceleration due
to gravity
• If dropped from rest from a
height H, the speed on
impact is  𝐻
• Consider depth of
impression or volume of
depression?
Volume of spherical cap
1
= 𝜋ℎ 3𝑎2 + ℎ2
6
1
=
𝜋ℎ 3𝑑 2 + 4ℎ2
24
Prove using
solids of
revolution?
Du Châtelet’s work – kinetic energy
Mechanical energy, kinetic and potential, may be lost to
another form, but the total is conserved in time.
Mme. du Châtelet’s contribution was the hypothesis of the
conservation of total energy, as distinct from momentum.
The verification that Kinetic energy is  mass(velocity)2
came from Du Châtelet’s reworking of Leibniz’s ideas, using
an experiment by Gravesande.
Gravesande experiment
Du Châtelet’s work – kinetic energy
Mme. du Châtelet’s contribution was the hypothesis of the
conservation of total energy, as distinct from momentum.
Without this additional consideration, problems such as the
collision and scattering of two particles cannot be fully
resolved.
Before
During
After
Du Châtelet’s work
Du Châtelet’s translation of Newton’s
Principia into French was the definitive
text into this century.
She did not simplify any of
his calculations and in fact
expanded on some of the
calculations, adding her
own proofs and diagrams
and a challenging
‘Algebraic Commentary’
which included her work on
kinetic energy.
The completion of her work
In 1748, Du Châtelet was living at Lunéville
with Voltaire and his retinue.
She worked long hours at her studies,
taking them immensely seriously and rarely
breaking away during the day.
She began an affair with a young poet,
Jean Francois Saint-Lambert, and soon fell
pregnant with his child.
Voltaire helped her to convince her husband that the child
was his. The child, a girl named Stanislas-Adélaide, was born
on 3rd September 1749.
The completion of her work
Voltaire wrote:
“The little girl arrives while her mother
was at her writing desk, scribbling some
Newtonian theories, and the newly born
baby was placed temporarily on a quarto
volume of geometry, while her mother
gathered together her papers and was put
to bed”
Du Châtelet’s final days
Gabrielle Émilie Le Tonnelier
de Breteuil, marquise du
Châtelet, died on 10th
September 1749, aged just
42.
Her husband, Saint-Lambert
and her long-time companion
Voltaire were all at her side.
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