Emilie du Chatelet died after child birth in 1749 at the age of 43. She knew the dangers of a late pregnancy. No anti-biotics to control infection; nothing to control uterine bleeding. Doctors did not bother to wash their hands or instruments. But she stoically accepted her probable fate. She’d always worked long hours and now the candles at her writing desk often burned till dawn as she raced to complete her translation and commentary on Newton’s science.
The famous writer and publicist Voltaire, her main and most constant lover, wrote of her achievements: “She was a great man whose only fault was in being a woman. A woman who translated and explained Newton ….. a very great man.”
Emilie’s book appeared in 1759 and for many years the only French translation of Newton’s Principia Mathematica. Voltaire wrote the Preface:- “Mme du Chatelet has rendered a double service to posterity with her translation of the Principia and enriching it with a commentary….. As regards the algebraic commentary, it is much more than a translation.…. It is more astonishing that a woman should have been capable of a task which required such depth and hard work….. “
The translating and explaining of Newton’s major work was a remarkable achievement in itself. Certainly few of the overwhelmingly male scientists at the time could grasp Newton’s ideas let alone do what she had done! But this was only one of several major achievements by this outstanding scientist, Emilie du Chatelet.
Emilie had already translated and explained the works of the German philosopher Leibniz, who had independently developed the mathematical calculus. Newton had a prior claim to the calculus and a bitter dispute between them grew over this matter.
When she was a girl she was described as gangly and ungainly. Her parents were French aristocratics and this elite class expected their daughters to be witty and beautiful. They considered that Emilie would not be marriageable and would lead the life of a spinster. Her father made the unusual and very rare decision to provide her with the best education possible, comparable to that of an aristocratic boy. The idea of educating women, even those of the ruling elite, was frowned upon – learning the art of courting was sufficient for young noblewomen!
Her early talent for mathematics had been encouraged by a family friend. As a teenager at the court of King at Versailles she was already reading the works of the natural philosophers. Her interests and intellect though soon left her isolated at the court. There being no others to debate or discuss scientific ideas and discoveries.
At nineteen Emilie chose one of the least objectionable courtiers, an older wealthy soldier, as a husband in a form of arranged marriage – the only way for her to gain status in society. They had nothing in common, her role was to provide his heirs, and in the custom of the time, her husband accepted her having affairs while he was away.
Meeting Voltaire she found they shared many interests, of promoting scientific ideas and of political reform. France had a king who demanded obedience, claiming that he was God’s regent on earth. Aristocrats got authority from the king, and it was impious to question this. But some began to think; what if the methods used in science by Newton could be applied to reveal the role of money, or other, hidden, forces in the political world as well to re-cast a more rational society?
It certainly wasn’t the case of a worldly, widely read man deciding when to let his young lover win the philosophical disputes between them. Du Chatelet was the real researcher of the physical world; the one who decided the important questions to be investigated.
At several times she came close to making breakthroughs. She performed a version of Lavoisier’s rust experiment, and if the scales she’d been able to get been machined more accurately, she might have been the one to come up with the law of the conservation of matter, even before Lavoisier was born!
Today we accept that scientific and religious ‘truths’ are separate, but in the seventeenth and eighteenth centuries this was far from the case. The differences between Newton’s and Liebniz’s scientific viewpoints also involved theological interpretations of our world.
Voltaire popularised the ‘ordained truths’ of Newton regarding energy: that when objects collide the energy involved is simply the product of their mass times their velocity. [Their m x v, written as mv1. If a 5 pound ball is going 10 miles per hour it must have 50 units of energy.] If two identical objects are on a collision course the two speeding objects are each endowed with a quantity of mv1. After they collide and had become stationary the mv1 of one cancelling out exactly the mv1 of the other.
Collisions like this happen all the time, but we don’t find that as time passes, that the world runs down through lack of energy. In Newton’s view the proof lay in this fact that our world continues to operate. Therefore God was reaching in, to nurture us; to supply all the motive forces that would otherwise be lost.
Liebniz disputed Newton’s view; “According to (Newton’s) doctrine, God Almighty wants to wind up his watch from time to time: otherwise it would cease to move. He had not, it seems, sufficient foresight to make it a perpetual motion.” Leibniz proposed his ‘vis viva’, [living force], as the principle that conserved the energy of the universe. Nothing is lost; the world runs itself; causality and energy do not leave our world – a supreme being is not needed to replace them. For Leibnitz God might have been needed at the very beginning, but now we are alone.
Leibnitz argued that when the two objects hit, all the energy they carried remains in existence. Their energy is not lost – merely transferred, or transformed. Leibniz claimed that the energy from the collision of objects was the mass of the body multiplied by the velocity squared! [The mass m x v x v, that is mv2. If a 5 pound ball is going at 10 mph, it has 5 times 10 times 10, that is 500 units of energy.]
Leibniz’s outlook flowed from his metaphysical philosophy, from his personal biases, and lacked objective proof. Newton had outlined a comprehensive world view. His proofs underpinned by complicated geometry and calculus that at the time was little understood. Voltaire felt it best just to nod in agreement, to accept it – for Newton had spoken! Emilie, however, worked through Leibniz’s contrary arguments for herself. She looked wider, for evidence that would help her make a choice.
She examined the recent experiments of Willem ’sGravesande, a Dutch researcher who’d been experimenting by driving brass spheres down into soft clay at measured speeds. If the simple Energy = mv1 was true, then a weight going twice as fast as an earlier one would sink in twice as deeply – one going three times as fast would sink three times as deep.
But that’s not what ‘sGravesande found. If the sphere fell twice as fast as before, it went four times as far into the clay. If it was flung down three times as fast, it sank nine times as far into the clay. This is what thinking of Energy as equal to mv2 would predict. 2 squared is 4. 3 squared is 9.
Du Chatelet analysis of these experiments deepened and improved Leibniz’s theory. Now, finally, there was a strong case for ‘mv2’ as a meaningful definition of energy. Most English-speaking scientists had taken Newton’s side, while German-speaking ones tended to support Leibniz. Du Chatelet’s voice was the major one in deciding the issue.
Through the lens of contemporary religious beliefs, Leibnitz’s ‘living force’, was seen, ironically, as a strangely passive view, suggesting that no fundamental improvements to our worldly condition could be made. Voltaire got great satisfaction by writing his play Candide to ridicule Liebnitz; “this the best of all possible worlds”. Candide is well written but Voltaire, unlike Emilie, misunderstood the basic argument!
In time energy expressed as being proportional to the mass of things multiplied by their velocity squared began to be accepted by physicists. Voltaire’s polemical skills, passing on the legacy of his lover, helped this process.
Why is squaring the velocity an accurate way to calculate energy in nature? The very geometry of our world often produces squared numbers. When you move twice as close toward a reading lamp, the light on the page you’re reading doesn’t simply get twice as strong – the light’s intensity increases four times! When you are further away, the light from the lamp is spread over a larger area. Go closer and that same amount of light is concentrated over a much smaller area.
If you accelerate your car on a road from 20 mph to 80 mph, your speed has gone up by four times. But it won’t take four times as long to stop if you apply the brakes and they lock. Your accumulated energy will have gone up by the square of four – that is sixteen times. That’s how much longer your car’s skid will be.
And if an object travels at the speed of light (called c, after the Greek celeritas)? It seemed to Einstein that the ultimate energy an object can contain was revealed when you look at its mass times c squared – its mc2. Einstein’s ground breaking conclusion that the seemingly separate domains of energy and mass were not only connected, but interchangeable, found its expression in his famous formula E =m c2.
In units of mph, c is 670 million, and so c2 is 448,000,000,000,000,000. A very little mass multiplied by this squaring of the speed of light meant an enormous potential energy could be released on the E side of Einstein’s equation. Du Chatelet’s insights had been a necessary step along that path, later trod by Einstein, that unveiled the secret of nuclear power.
In time her role came to be forgotten. Each new generation of scientists tends to neglect the past. But also because it was unsettling that a woman could have so greatly contributed to the shaping of the course of scientific thought.
And of Emilie’s views on women in society. From Emilie’s preface of her edited translation of Mandeville’s The Fable of the Bees, that she sub-titled “A Rendering and a Feminist Manifesto.
“I feel the full weight of the prejudice which so universally excludes us from the sciences; it is one of the contradictions in life that has always amazed me, ….. Why these creatures whose understanding appears in every way similar to that of men, seem to be stopped by some irresistible force, this side of a barrier. Let the people give a reason, but until they do, women will have reason to protest against their education ….. If I were king I would redress an abuse that cuts back, as it were, one half of human kind. I would have women participate in all human rights, especially those of the mind ….. The new education would greatly benefit the human race. Women would be worth more and men would gain something new to emulate …… I am convinced that either many women are unaware of their talents by reason of the fault in their education or they bury them on account of prejudice ….. My own experience confirms this. Chance made me aquainted with men of letters who extended the hand of friendship to me ….. I then began to believe that I was a being with a mind …..”