“Carte blanche”. One of my favorite scientific articles was written by Edward Lorenz in 1963 and is entitled “Deterministic Nonperiodic Flow”. It is one of the founding texts of chaos theory. Its content will be passed on to the general public a little later through the beautiful image of the butterfly effect: a flapping of a butterfly’s wings in Brazil could create a hurricane in Texas. This publication is an extraordinary blend of physics, meteorology, mathematics and numerical simulations. I have read and reread it many, many times and thought I knew it until last week.

An article by Joshua Sokol in Quanta Magazine told me that I should have read the last paragraph in which the author thanks “Miss Ellen Fetter who took care of the many calculations and graphs”. How? It was not Edward Lorenz who did the calculations, but an assistant? It must be understood that simulating the movement of the atmosphere on a computer was an essential component of the article. In 1963, computers were primitive and “taking care of the calculations” would probably have deserved a little more than a discreet thank you.

**Handmade calculations**

This is not the first time that scientists have used “female calculators”, whose names appear at best in the acknowledgements. Ten years earlier, Enrico Fermi, John Pasta and Stanislaw Ulam published the first numerical simulation of a complex physical system. This article can be considered the birth of a new discipline in mathematical physics. It involved studying, on a computer, the vibrations of a chain made up of about sixty “non-linear” springs.

Here again, two discrete lines in the publication thank Miss Mary Tsingou for “the efficient programming of the problem and for having carried out the calculations on the Maniac de Los Alamos computer”, which represents a very important part of the work. It is only in 2008 that the physicist Thierry Dauxois will read these two lines and will propose to call Fermi-Pasta-Ulam-Tsingou this numerical simulation. I would have even proposed to respect the alphabetical order…

Going back in time again, we arrive at a period when calculations were done by hand, and the hand in question was often female. In the 1940s, a member of an institute of applied mathematics dared to talk about the kilogirl (kilofille): the amount of calculations a woman can produce in a thousand hours! Around 1880, the astronomer Edward Charles Pickering recruited a team of more than 80 female calculators at Harvard, Massachusetts, known as the “Pickering Harem” and paid less than a labourer.

Halley’s Comet is known to be visible in the sky about every 76 years. Its trajectory is disturbed by the attraction of Jupiter and Saturn. In the middle of the 18th century, some scientists still had doubts about Newton’s theory of gravitation. The calculation of the date of the comet’s return was a great moment in the history of science. In November 1758, the academician Alexis Clairaut announced a return “around April of next year”. It was a triumph when his prediction came true. The theory was indeed due to Clairaut, but the monstrous calculations were performed by Joseph Lalande and Nicole-Reine Lepaute who “calculated from morning till night, sometimes even at the table. Clairaut “forgot” to thank her collaborator. The City of Paris will do Nicole-Reine partial justice in 2007 by naming a street after her.

In 2017, Google engineer James Damore was fired after claiming that the lack of female computer scientists was of biological origin.