Biography
Early years
The son of clerk assistant Jean-Baptiste Rousseau and Marie Renée Lefort, he was the oldest of three brothers. One of his brothers, René, died at the Battle of France and the other, Jean, volunteered as an airborne radio-operator in the Free French Forces before pursuing a career at Air France.
Rousseau was drawn to science as a child through reading a popular astronomy collection published by Théophile Moreux. A gifted student in mathematics who received departmental and national bursaries in 1918 and 1920, Rousseau built his first telescope at the age of 13 and published his first scientific paper at 17.
With the help of Jean Becquerel, he was appointed Assistant Boarding Master at the Montargis middle school in 1923. Despite his repeated attempts to be transferred to a city with a university in order to prepare his degree, Rousseau lived for several years between Fontainebleau, Blois and Vendôme.
After obtaining his first degree in General Mathematics in 1929, he was transferred to Paris at the Lycée Charlemagne and briefly to the Lycée Janson-de-Sailly before becoming assistant teacher at the Lycée Buffon. Rousseau then fulfilled his military obligation in 1931.
Certified in Advanced Astronomy in March 1932, he obtained two distinct degrees in Philosophy (Psychology, Morals and Sociology) and in Mathematics and Physics in 1935.
First publications
While working toward his university degrees, Rousseau covered scientific news in several newspapers. His most significant articles were published in La Nature, a popular science magazine founded in 1873 by Gaston Tissandier. His experience as a popular writer fed his future works. His scientific columns earned him a significant number of letters from his readers.
Astronomy
When asked to transfer to the Lycée Félix Faure of Beauvaisin 1935, Rousseau resigned from the Éducation Nationale without hesitation to join the Meudon Observatory as "Astronome Stagiaire au Service du Méridien" ("Trainee Astronomer at the Meridian Study"). At the time, French astronomy was under-developed compared to other western nations at the time (namely British, North American and Russian). The total staff of astronomers barely reached 150 in France, and the modernization project of the observatory, set in the Château de Meudon had just started; feeders and racks of the stables where the laboratories were installed had not yet been removed.
Audouin Dollfus, one of the most eminent astronomer in France, son of Charles Dollfus (creator of the Musée de l'Air and Honorary Astronomer at the Paris Observatory), remembers Pierre Rousseau as a young astronomer:
"Before the War, we were only a fistful. Pierre Rousseau was a modest person, almost too modest, deep, an excellent writer and an excellent popularizer. His books on astronomy are admirable! I read them avidly. To illustrate his Mars, Mysterious Earth, I think he obtained the images from the telescope of Antoniadi himself."
In 1939, Rousseau was enlisted and stationed in an artillery battery unit in Lorraine . He writes in Le monde des étoiles (The World of Stars - 1950); "Combien de fois l’auteur de ce livre ne l’a-t-il pas contemplé [Jupiter.]… pendant la dernière guerre, avec la modeste « binoculaire » de sa batterie ?" (How many times the author of this book contemplated, during the last war, [Jupiter] with his modest binoculars ?).
His first book on astronomy (L'Exploration du Ciel - Sky Exploration) was published the same year, at 8.0000 copies. It shows, early on, Rousseau's distinctive love for anecdotes and a particular care to underline the work of scientists and the importance of the history of science.
While focusing particularly on astronomy and related sciences, he was also interested in epistemology, astronautics, geology, nuclear physics, and electricity. His last book, L'avenir de la Terre (The Future of Earth) was published in 1977 by Nouvelles Éditions Latines.
Later life
Through the 1950s and 1960s, Rousseau continued his work as a science journalist and popular science writer. His works were translated in several languages and have inspired some of his readers to become astronomers. With his multiple experiences in various scientific domains and the history of science, Rousseau presented himself as a witness of the evolution of scientific progress in the eyes of the public opinion. After the publication of his last essay, The Future Earth, he suffered a stroke at the end of the 1970s. Rousseau then progressively lost his physical and intellectual capacities until his death.
