Person: Gassendi, Pierre
Pierre Gassendi was a French astronomer who was the first to observe a transit of Venus. He wrote on astronomy, his own astronomical observations and on falling bodies.
Mathematical Profile (Excerpt):
- Pierre Gassendi was actually given the name Pierre Gassend and only later used the now familiar Gassendi form.
- When Pierre was seven years old he was sent to school in Digne, a much larger town across the valley about 10 km from Champtercier.
- In 1607, Gassendi left school in Digne and returned to his native village of Champtercier where he spent the next two years.
- He clearly was an exceptional student for when Fesaye was absent he asked Gassendi to take the lecture in his place.
- From 1611, Gassendi studied theology under Professor Raphaelis and, as part of the course, he learnt Greek and Hebrew.
- Gassendi was Principal at the College of Digne from April 1612 to 1614.
- In April 1615 Gassendi left Provence for the first time, spending the period from April to November in Paris.
- Gassendi applied for both chairs and was offered both.
- Gassendi spent six years at Aix where he met Nicolas-Claude Fabri de Peiresc (1580-1637) who became his patron, supporting him financially for many years.
- Later Morin and Gassendi would become involved in a public dispute but at this stage they were good friends.
- Gassendi quickly learnt astronomy from Gaultier and so Peiresc also employed Gassendi as part of the team to assist in his project of computing the times of the four moons of Jupiter.
- We also have records of Gassendi and Gaultier observing a comet in 1618, an eclipse of the moon in 1620, and an eclipse of the sun in 1621.
- Gassendi's position at the University of Aix only lasted until 1623 when the Jesuit order took control of the university and he was forced to leave.
- This was not because the Jesuits had any particular objection to the material that Gassendi was teaching, rather it was just that they dismissed all those who were not Jesuits.
- However, there is over twenty years of Gassendi's career to look at before we reach that point.
- Gassendi first met Mersenne in October 1623 when he visited Paris.
- He took with him an introduction from Peiresc and soon Gassendi and Mersenne became good friends.
- Through Mersenne, Gassendi quickly became acquainted with many leading scholars.
- From that time on until Mersenne's death in 1648, whenever Gassendi was in Paris he would visit Mersenne and the two would celebrate mass together.
- After returning to Provence from Paris, Gassendi wrote to Galileo with strong support for his argument that the earth revolves round the sun.
- Gassendi had been intending to produce six further volumes of his Exercitationes but at this time he decided to give up the project.
- Pierre and Jacques Dupuy were librarians at the Bibliothèque du Roi, which dated back to the fourteenth century.
- In 1632 Gassendi published Mercury seen on the face of the sun, which described his observations of the transit of Mercury which he observed from Paris in November 1631 following the prediction of the event by Kepler in 1629.
- Gassendi had used a telescope to project the image of the sun onto paper, and so was able to observe the transit.
- Gassendi continued to publish works on philosophy and astronomy.
- Life became more difficult for Gassendi after his patron Peiresc died in 1637.
- Although Peiresc left books and mathematical instruments to Gassendi in his will, Peiresc's nephew refused to let Gassendi have them.
- Gassendi went on to write a biography of Peiresc, published in 1641; it is generally considered the first biography of a scholar.
- Gassendi later wrote biographies of Copernicus, Puerbach and Regiomontanus.
- Mersenne asked Gassendi to review Descartes' Meditations which he did producing Objections in 1641.
- Descartes did not take kindly to Gassendi's criticisms and replied with a stinging attack in Responses.
- Gassendi was not going to allow matters to rest there, and replied again, this time with Instantiae which began to circulate in Paris in 1642.
- This was not the only public debate that Gassendi was carrying out at this time.
- Gassendi was a firm believer in the system of Copernicus and Galileo, and the argument with Morin led to him thinking deeply about the scientific case for a sun centred system.
- In 1642 Gassendi published On the motion impressed by a moving mover.
- Several attacks on this work of Gassendi resulted in his publishing further work supporting the arguments of Galileo entitled On the proportion by which heavy bodies are accelerated.
- In 1645, on the recommendation of Cardinal Richelieu, Gassendi was offered the Chair of Mathematics at the Collège Royale in Paris.
- Gassendi's health was rather poor by this stage in his life, being troubled by a lung complaint.
- The results of Gassendi's observations and his lectures were written up and published as Institutio astronomica juxta hypotheseis tam veterum, quam Copernici et Tychonis in 1647.
- As he had feared, Gassendi began to find that his health was making it very difficult for him to continue teaching so, as the conditions of his appointment allowed, he left for Provence in 1648.
- Despite Gassendi's lung troubles, he was able to climb a mountain on 5 February 1650 with his assistant François Bernier and confirm the findings of the Puy de Dôme experiment.
- Gassendi remained in Provence until the spring of 1653 when he felt well enough to return to Paris with his assistant François Bernier.
- They met on Saturday mornings, and probably due to their influence, Gassendi produced an anonymous pamphlet attempting to reassure the people of Paris that the predicted eclipse on 12 August 1654 would not lead to a disaster.
Born 22 January 1592, Champtercier, Provence, France. Died 24 October 1655, Paris, France.
View full biography at MacTutor
Tags relevant for this person:
Astronomy, Physics
Thank you to the contributors under CC BY-SA 4.0! 
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- non-Github:
- @J-J-O'Connor
- @E-F-Robertson
References
Adapted from other CC BY-SA 4.0 Sources:
- O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive
