◀ ▲ ▶History / 18th-century / Person: De Lalande, Joseph-Jérôme Lefrançais

Person: De Lalande, Joseph-Jérôme Lefrançais

Jérôme Lalande was a French astronomer who made important measurements of the Solar System.

Mathematical Profile (Excerpt):

• In fact, for the first twenty years of his life Lalande was known as Jérôme Le Français, but after this he called himself Jérôme Le Français de la Lande.
• Aristocratic names were certainly to be avoided at the time of the French Revolution, so at this time he made the "le" and "la" part of the following names and wrote Jérôme Lefrançais de Lalande.
• For simplicity we shall use the name Lalande throughout this article.
• It is somewhat ironical that Lalande, who would later become renowned as an atheist, should have come so close to becoming a Jesuit.
• It was his parents wish that he study law that stopped Lalande joining the Jesuits, but more surprisingly it was also this wish which turned him into an astronomer.
• Lalande was fascinated by astronomy and, although he continued to study law, he also attended Delisle's astronomy lectures at the Collège Royale as well as Pierre Lemonnier's lectures on mathematical physics.
• Despite his interest in astronomy, Lalande completed his law studies and in 1751, still only aged nineteen, he qualified and prepared to return to his home town of Bourg-en-Bresse to practise law.
• Several sites had been chosen from which to make simultaneous observations and Nicolas Lacaille was sent by the Académie des Sciences to make observations from the Cape of Good Hope while Lemonnier, who was responsible for the observations to be made in Berlin, asked Lalande to go in his place.
• The visit proved highly successful for Lalande who, despite his youth, was admitted to the Prussian Academy and was able to discuss science with Voltaire, Maupertuis and Euler.
• Lalande's observations were published in Acta eruditorum, and in publications of the Berlin Academy and the Paris Academy.
• After his return to France, Lalande was elected to the Académie des Sciences in Paris on 4 February 1753.
• This was a great achievement for so young a man and for the vain Lalande it was extremely pleasing.
• To do this it was, of course, necessary to know the precise amount by which the Earth differed from a perfect sphere and Lalande disagreed with Lemonnier on the issue.
• The Paris Academy set up a commission to settle the argument and it decided in favour of Lalande.
• This certainly did not please Lemonnier and relations between him and Lalande soured.
• One of the next tasks that Lalande undertook was to assist Clairaut in calculating a more accurate orbit for Halley's comet.
• The calculations were very demanding and were undertaken by Lalande together with Mme Lepaute.
• Many accounts of this work ignored the enormous contributions made by Mme Lepaute, who worked night and day on the mathematical calculations, but Lalande was always keen to acknowledge the large scientific contribution being made by women and we mention below other projects on which he collaborated with women mathematicians.
• Lalande went on to publish a corrected edition of the tables of Halley's Comet based on these computations.
• In 1759 Lalande was asked if he would take over the editorship of the astronomical almanac Connaissance des temps Ⓣ(Knowledge of time).
• During his editorship, Lalande added accurate tables of lunar distances from stars which were valuable in navigation.
• In the year he took over as editor, Lalande was offered another prestigious position namely to follow his teacher Delisle as professor of astronomy at the Collège Royale.
• These events were of sufficient importance to have international cooperation organised to have the observations made from different sites, and Lalande played a role in coordinating this project.
• As well as his accurate observations, Lalande was also famous for his books.
• Before the publication of the third edition, in 1791, Lalande achieved the great honour of being elected Head of the Collège de France.
• By this time Lalande was sixty years old, he had survived the Terror during the French Revolution unscathed, something which he put down to his atheist views.
• What was being celebrated was a religion to substitute for Christianity and Lalande played a leading role.
• We are nearing the end of our description of Lalande's career, but let us pause to look at some aspects of his character.
• Lalande character seemed to contain many contradictions.
• Napoleon had been happy to agree that Lalande add his name to the Dictionary of Atheists in 1799.
• Lalande took the opportunity to reissue his Dictionary of Atheists with Napoleon's name included which caused the new Emperor to demand that the Institut de France censure Lalande.
• Delambre, who was at this time the Permanent Secretary to the Institut, tried hard to make Lalande bend to the Emperor's demands without being seen to undermine the highly prized intellectual freedom that members of the Institut enjoyed.
• Lalande refused to stop putting forward his atheist views.
• She was the chief investigator on Lalande's large-scale study of lunar astronomy, which was undertaken at the Paris Observatory, and she became the first woman in Paris to teach astronomy.
• The importance in which Lalande held women's contributions to astronomy, particularly as mathematicians and calculators, is seen in his Astronomie des dames first published in 1785, with new editions in 1795 and 1806.
• When the French Revolution led to the closure of the Académie des Sciences, Lalande attempted to set up a new organisation which he called Réunion des Sciences to carry on its functions.
• One important task Lalande undertook near the end of his career was to complete the remaining two volumes of Montucla's four volume Histoire des mathématiques Ⓣ(History of Mathematics).
• They were published in 1802 when Lalande was 70 years old.
• We should also mention that he instituted the Lalande Prize, also in the year 1802.
• Napoleon's insistence that Lalande stop his public support of atheism became unnecessary since Lalande fell ill.
• It is hard to assess Lalande's contributions for his personality certainly affected the way he was viewed in his own lifetime.

Born 11 July 1732, Bourg-en-Bresse, Ain, France. Died 4 April 1807, Paris, France.

View full biography at MacTutor

Tags relevant for this person:

Astronomy, Geography, Geometry, Physics

Thank you to the contributors under CC BY-SA 4.0!

Github:

non-Github:

@J-J-O'Connor

@E-F-Robertson

References

Adapted from other CC BY-SA 4.0 Sources:

1. O’Connor, John J; Robertson, Edmund F: MacTutor History of Mathematics Archive