Born: 5 January 1723, France
Died: 6 December 1788
Country most active: France
Also known as: Nicole-Reine Etable de Labrière
This biography, written by J J O’Connor and E F Robertson, has been republished with permission from the School of Mathematics and Statistics at the University of St Andrews, Scotland.
Nicole-Reine Etable de Labrière was born in the Palais du Luxembourg in Paris where her father was in the service of the Queen of Spain, Elisabeth d’Orléans. One day the royal clockmaker Jean-Andre Lepaute (1709-1789) and his brother arrived at the Palais du Luxembourg to install a new type of clock. Nicole-Reine met Jean-Andre Lepaute on this occasion and their friendship blossomed. The two were married on 27 August 1749 and lived at the Palais du Luxembourg. Nicole-Reine helped her husband in his work, in particular keeping the Lepaute accounts. It is interesting to realise that the couple were living in the Palais du Luxembourg when Louis XV exhibited a selection of the royal collection of paintings in 1750. This exhibition moved to the Louvre to become the basis for the famous art gallery.
It was not long after Nicole-Reine married that Jérôme Lalande, who was at that time a law student, became fascinated by astronomy and was given a room above the porch of the Palais du Luxembourg to use as an observatory. Lalande quickly became a friend of Nicole-Reine and Jean-Andre Lepaute. He was sent to the Cape of Good Hope to make astronomical observations and, returning to Paris in 1753 after a very successful trip, he was elected to the Academy of Sciences. Jean-Andre Lepaute had designed a clock with a new type of escapement and Lalande was asked by the Academy to evaluate it for astronomical use. This prompted Jean-Andre Lepaute to become interested in building astronomical clocks and he published Traité d’Horlogerie contenant tout ce qui est nécessaire pour bien connoître et pour régler les pendules et les montres (Treatise on clock-making containing all that is necessary to be well acquainted and to set clocks and watches) in Paris in 1755. This work contains the first mathematical work by Nicole-Reine Lepaute who calculated the tables of oscillations of a pendulum which were contained in her husband’s work.
In June 1757 Lalande decided that he would like to attempt to calculate a precise date for the return of Halley’s comet. It was known to have been seen in 1305, 1380, 1456, 1531, 1607 and 1682 and Halley, taking into account perturbations to the orbit caused by the gravitational effects of Jupiter, had predicted that the comet would return reaching perihelion in December 1758. However the only way to get a more accurate prediction of its date of return was to calculate the perturbations to the orbit caused by the gravitational effects of both Jupiter and Saturn. Lalande approached Alexis Clairaut for help and Clairaut provided a basic programme of work requiring an extraordinary amount of computation. Lalande then asked Nicole-Reine Lepaute to assist him in the computations. Lalande wrote in Bibliographie Astronomique (1803):-
During six months we calculated from morning to night, sometimes even at meals. … The assistance of Mme Lepaute was such that, without her I should never have been able to undertake the enormous labour, in which it was necessary to calculate the distance of each of the two planets Jupiter and Saturn from the comet, separately for each successive degree for 150 years.
On 14 November 1758 Clairaut reported to the Academy of Sciences that they predicted the comet would reach perihelion by mid-April 1759. In fact the team had completed the calculations just in time for, on 25 December 1758, the comet was sighted. It actually reached perihelion on 13 April 1759, within the margin of error given for the prediction. Clairaut published Théorie des comètes (Theory of comets) (Paris, 1760) describing how the calculations had been carried out. He listed those who had assisted in the computations but did not put Nicole-Reine Lepaute’s name on the list. It has been claimed that this deliberate omission was to please his girlfriend Mademoiselle Goulier who was jealous of Lepaute. Whatever the reason, the omission caused a rift between Lalande and Clairaut, and the two men never again collaborated on an astronomical project. Lalande gave Nicole-Reine Lepaute the credit she deserved in his own publication; see the quote above.
In 1759 Lalande was asked if he would take over the editorship of the astronomical almanac Connaissance des temps. He was editor from 1760 until 1776, and Nicole-Reine Lepaute assisted him in computing the tables in this annual publication of the Academy of Sciences. Although her contributions are thought to have been substantial, we do not have any precise details of which part of the work she undertook. There are, however, many areas where we do know of her contributions. The Ephémérides des mouvements célestes (Almanac of celestial movements) gave tables of the sun, the moon and planets covering a period of ten years. Lepaute was the main person responsible for producing Volume VII, covering the period 1775-1784, and Volume VIII, covering the period 1783-1792. Alic writes:-
For this last volume she alone made all the computations for the positions of the sun, moon and planets.
Alic also claims that Lepaute published a memoir containing observations of the transit of Venus across disk of the sun in 1761. This may have been one of the memoirs which Lalande says that she wrote for the l’Académie de Béziers but these have not been found. Since she was elected a member of l’Académie de Béziers around this time it is likely that this information is correct. Other specific tasks carried out by Lepaute that are specified by Lalande include calculations for elements of the comet observed in 1762.
Another piece of work which is certainly due to Lepaute is the calculation concerning the annular eclipse of the sun on 1 April 1764. She produced a chart giving the path of the eclipse across Europe which was published in the Jesuit journal the Mémoires de Trévoux in June 1762. Alic writes:-
Her calculations required that she prepare a table of parallactic angles (the angle of displacement of an object caused by a change in the observer’s position), her extended version of which was published by the French government.
Thousands of copies of Lepaute’s chart were distributed in Paris.
Finally we mention that a crater on the moon has been named in honour of Lepaute.
The following is excerpted from Infinite Women creator Allison Tyra’s book Uncredited: Women’s Overlooked, Misattributed, and Stolen Work.
After building a clock with an astronomical function with her husband, Nicole-Reine Lepaute collaborated with him and astronomer Jérôme Lalande to produce a Traité d’horlogerie (Treatise of Clockmaking), published in 1775. Although it was her idea and she participated in its construction, as well as the writing of the treatise, it was published only under her husband’s name. Lalande acknowledged her contributions, noting “Madame Lepaute computed for this book a table of numbers of oscillations for pendulums of different lengths, or the lengths for each given number of vibrations, from that of 18 lignes, that does 18000 vibrations per hour, up to that of 3000 leagues.” She then worked with him and a male mathematician, to calculate when Halley’s Comet would return and the comet’s attraction to Jupiter and Saturn. Working for more than six months, the team predicted in November 1758 that it would arrive on April 13, 1759 with a margin of error of a month on either side. They were off by precisely one month when it returned on March 13, 1759, but it was the first time scientists had successfully predicted when the comet would cross the perihelion (the point of the comet’s orbit closest to the sun). Lalande did not acknowledge Lepaute’s contributions at all—allegedly removing all mentions of her from the book he published in 1760 to please another woman—though Lalande remained her staunch proponent, crediting her in an article calling her the “most distinguished female French astronomer ever.”