ismaël boulliau (1605 - 1694)
Ismaël Boulliau (Boulliaud), also known as Ismael Bullialdus, was a French astronomer and mathematician who followed the teachings of Copernicus.
Boulliau worked as a librarian for many years and had the opportunity to study the scientific works of Copernicus, Galileo, and Kepler, and as a result became a strong supporter of the heliocentric system of the world. Boulliau was also intimately acquainted with Huygens, Gassendi, Pascal and other prominent scientists of the time, and he translated many works from Greek into Latin.
Boulliau's main astronomical work, published in 1645, was Astronomia philolaica (Astronomy of Philolaus, named after the ancient Greek Pythagorean philosopher Philolaus, who promoted the idea of the motion of the Earth). In it, he supported Kepler's first law that the planets move on ellipses, and provided new evidence for this. Isaac Newton, in Book III of The Mathematical Beginnings of Natural Philosophy, relies on measurements of the magnitudes of planetary orbits determined from observations by Kepler and Boulliau.
Boulliau was also interested in history, theology, classical studies, and philology. He was active in the Republic of Letters, an intellectual community whose members exchanged ideas.
