# Marie-Antoinette Tonnelat

Marie-Antoinette Tonnelat (née Baudot) (March 5, 1912 – December 3, 1980) was a French theoretical physicist. Her physics research focused on relativistic quantum mechanics under the influence of gravity. Along with the help of Albert Einstein and Erwin Schrödinger, she attempted to propose one of the first unified field theories. She is also known for her work on the history of special and general relativity.

## Life
### Early years and education

Marie-Antoinette Baudot was born on March 5, 1912, in Charolles, a commune in the Southern Burgundy region of France. She began her education at Lycée de Chalon-sur-Saône and finished her higher education at Lycée Louis-le-Grand. Initially, she pursued engineering, but she eventually obtained two degrees in the sciences and in philosophy at the University of Sorbonne in Paris.
In 1935, Tonnelat pursued a doctorate in theoretical physics under Louis de Broglie at the Institut Henri Poincaré. In 1941, she finished her doctoral thesis titled On the Theory of the Photon in a Riemannian space. The same year she got married with Jacques Tonnelat, and in 1945 went on to become a researcher at the French National Center for Scientific Research (CNRS).

### Research with de Broglie

Her research focused on the field of relativistic spin-particles under the influence of a gravitational field. With de Broglie's neutrino theory of light, Tonnelat arrived at particles with maximal spin 2 from massive spin 1 particles, or photons. Spin 2 corresponded to the graviton. With her knowledge of the Klein-Gordon equation, Maxwell's equations, and the linearized version of the equation for Einstein spaces, she examined the theory for a particle with spin 2 and called it "a unitary formalism". She published a paper in the early 1940s in which she established the standard commutation relations for the quantized spin-2 field. De Broglie supported her research in unified field theory, but he himself stayed away from it and chose not to be directly involved with her studies.
Although her papers were eventually published at the French Academy of Sciences, her work was subject to delays due to an interruption caused by German occupation of France in the early 1940s.

### Professional career

Tonnelat spent much of her career as an educator. After the war, Tonnelat spent some time at the Dublin Institute for Advanced Studies with scientist Erwin Schrödinger in order to focus on furthering the research she had done under de Broglie earlier in her life. Once again, she began to examine the concept of unitary formalism that comes from emerging spin-2 particles. Her time with Schrödinger inspired her interest in the relativity theory and sparked her correspondence with Albert Einstein as well. Her goal was to create one unified theory using the concepts and ideas discovered by Einstein and Schrödinger.
In 1953, just prior to Einstein's death, Marie-Antoinette Tonnelat was invited to Princeton University to speak about the topic at the International Congress for the History of Science in Jerusalem. She gave many lectures throughout her career about her work related to the theory of relativity.
In 1956, she became a chair professor of physical theories at the Faculty of Science at the University of Paris. In parallel, she taught at the Institute of History of Science and Technology (directed by Gaston Bachelard) for twenty years.
In 1965, she published a second book on unified field theories that focused on the development of research in the field. There was only one chapter in the work that referred to her own research relating to Einstein and Schrödinger, but the book contained a few references to the doctoral theses that she had advised. Tonnelat's work was mainly concerned with establishing a connection between classic and quantum field theory. She debuts an alternative theory of gravitation (linear gravity), which she had studied in 1960.
In the 1960s, Tonnelat participated as nominator for the Nobel Prize in Physics, she proposed Louis Néel in 1960 and Alfred Kastler in 1965.
In 1980, Marie-Antoinette Tonnelat's deteriorating health made it difficult for her to continue giving her lectures. She died shortly after her last lecture.
She left an unpublished work about the history of theories of light and color.

## Honors and awards

Tonnelat became a Peccot Lecturer and Laureate of the Collège de France in 1943. Her talk titled "Unitary theories of light and gravitation" (French: Les théories unitaires de la lumière et de la gravitation). From the French Academy of Sciences she received the Pierson–Perrin Prize (1946) and the Henri Poincaré Award (1971).
For her book History of the Principle of Relativity (French: Histoire du principe de la Relativité) Tonnelat received the Prix d'Académie [fr] of the Académie Française in 1972 awarded for outstanding publications.
Tonnelat was elected member of the International Academy of the History of Science in 1973.