Ismaël Bullialdus facts for kids
Quick facts for kids
Ismaël Bullialdus
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| Born | 28 September 1605 Loudun, France
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| Died | 25 November 1694 (aged 89) Abbey St. Victor, Paris, France
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| Nationality | French |
| Other names | Ismaël Boulliau, Ismaël Boulliaud, Ismaël Boullian |
| Occupation | Astronomer |
| Known for | Astronomia Philolaica and Republic of Letters correspondences |
Ismaël Boulliau (born September 28, 1605 – died November 25, 1694) was a French astronomer and mathematician from the 1600s. He was also very interested in history, religion, and ancient studies.
Boulliau was an important member of the Republic of Letters. This was a group of smart people who shared their ideas through letters. He was one of the first to support the ideas of famous scientists like Copernicus, Kepler, and Galileo. Many people called him "the most noted astronomer of his generation." One of his most famous books is Astronomia Philolaica, published in 1645.
Contents
Life and Career
Ismaël Boulliau was the second son born to his parents, Susanna Motet and Ismaël Bullialdus. His family followed the Calvinist religion. His father was a notary, which is someone who can legally witness documents. He was also an amateur astronomer who enjoyed watching the stars in Loudun, France. Boulliau's older brother, also named Ismaël, sadly died soon after he was born.
When he was 21, Boulliau changed his religion to Roman Catholicism. He became a priest at age 26. A year later, in 1632, he moved to Paris, the capital of France.
Boulliau was supported by the de Thou family. For 30 years, he worked in Paris as a librarian. He helped the brothers Jacques and Pierre Dupuy with the Bibliothèque du Roi. This was France's first royal library, which is now known as the Bibliothèque nationale de France.
After the Dupuy brothers passed away, Boulliau became a secretary. He worked for the French ambassador in Holland. But after an argument in 1666, he moved again. This time, he went to the Collège de Laon, where he worked as a librarian once more.
Boulliau published his first book, De Natura Lucis, in 1638. After that, he wrote many more works. These included books and published letters from his time in the Republic of Letters. He was one of the first people from another country to be chosen as a member of the Royal Society of London. This happened on April 4, 1667, just seven years after the Society was created. He spent the last five years of his life working as a priest, just as he had started his career.
He retired to the Abbey St. Victor in Paris. He passed away there when he was 89 years old.
Sharing Ideas: The Republic of Letters
Boulliau was a very active member of the Republic of Letters. This was a network of smart people who wrote letters to each other over long distances. It was like an international club for scholars and writers. Boulliau wrote a lot of letters. About 5,000 of his letters still exist today!
His letters show how far the Republic of Letters reached. He wrote to scholars not just in nearby countries like Holland and Italy. He also wrote to people in Scandinavia, Poland, and even the Near East. About 4,200 of his letters are kept in the Collection Boulliau at the Bibliothèque nationale de France. Another 800 letters to or from him are in 45 different archives in almost a dozen countries. Sadly, many of his original writings are lost. Soon after he died, his entire library, including books, notes, and letters, was scattered.
Some of the most famous letters in his collection were with important thinkers. These included Galileo, Marin Mersenne, Henry Oldenburg, Christiaan Huygens, and Fermat. Besides his own letters, Boulliau helped preserve other scientific papers. Among his documents were notes and studies of rare old writings. He also kept copies of his friends' writings, which helped save them. Perhaps most important were the ten volumes of original letters written to Nicolas-Claude Fabri de Peiresc.
Main Works
- De natura lucis (1638)
- Philolaus (1639)
- Expositio rerum mathematicarum ad legendum Platonem utilium, a translation of Theon of Smyrna (1644)
- Astronomia philolaica (1645) e-rara.ch
- De lineis spiralibus (1657)
- Opus novum ad arithmeticam infinitorum (1682)
- Ad astronomos monita duo (1667)
Ismaël Boulliau's most famous work is Astronomia Philolaica. This book was published in 1645. Some modern science historians believe it was the most important astronomy book between Kepler and Newton. The book helped spread the idea of Kepler's planetary ellipses, which means planets move in oval shapes, not perfect circles.
Kepler thought that a physical force caused planets to move. He used math and science to support his idea. But Boulliau offered a completely new idea called the "Conical Hypothesis."
Boulliau's Conical Hypothesis
Boulliau believed that planets always move in circles. He thought circles were the most perfect shape. However, he also believed that a planet doesn't stay in just one circle. Instead, it constantly moves from one circle to another. It passes through an endless number of circles during each trip around the sun.
He explained this by thinking about an ellipse (the oval shape of a planet's path). An ellipse can be made by cutting a cone at an angle. Inside a cone, there are many circles between the top and bottom of the ellipse. Boulliau thought that a planet moving in an ellipse was actually moving in tiny parts of these many circles.
He also believed that the planet's motion was perfectly smooth and even. He thought this was the most perfect kind of motion. This smooth motion wasn't along the elliptical path itself. Instead, it was along one of the circles that were parallel to the base of the cone. If you drew a line from the planet to one of these circles, and that line moved with the planet, it would cut off equal parts of that circle in equal amounts of time. This was a very imaginative idea to explain how planets move in perfect, even ways, even though their paths look like ellipses.
See also
- List of Roman Catholic scientist-clerics
- Republic of Letters
