Jean-Baptiste Biot

1774 (Paris) – 1862 (Paris)

Arago and he worked together early in their careers, Arago coming to feel that Biot had sabotaged his results (he then revenged himself by working with Biot’s protégé Fresnel on the polarisation of light). Assisting Laplace in preparing his findings for publication, Biot observed that Laplace used the stock phrase “it is easy to see” when he’d forgotten his original reasoning. Biot and Gay-Lussac were the first to ascend in a balloon for scientific purposes. He did pioneering electro-magnetic work with Savart, and asked the young Pasteur to come and demonstrate his findings about the handedness of some molecules.

Jean le Rond d’Alembert

1717 (Paris) – 1783 (Paris)

Key player in the French Enlightenment. Diderot and d’Alembert were co-editors of the Encyclopédie, Rousseau as well as Buffon a noted contributor, and Voltaire one of the project’s greatest supporters. D’Alembert encouraged Monge to submit papers to the Académie des Sciences, helped the mathematicians Legendre, Condorcet and Lagrange up the professional ladder, but was put out to feel that Laplace’s subsequent work made his own obsolete. Hume, Smith and Gibbon were fellow attendees at d’Holbach’s salon. Rameau had been a friend, but disagreements over the Encyclopédie soured their relations. Casanova described him as the most modest man he’d ever known.

Jean Baptiste Perrin

1870 (Lille, France) – 1942 (New York)

Physicist who received the Nobel Prize for his work confirming the structure of matter. The Curies were next-door neighbours and professional colleagues (though Perrin, younger and better-connected, was awarded a position they coveted). Einstein wrote complementing him on the precision of his observations of Brownian motion (which assisted in Einstein’s own work). Lévi-Strauss knew him right at the end of his life, in New York, where they helped set up an institution for exiled French academics.

Jean Baptiste Perrin knew…

Augustin-Jean Fresnel

Augustin Fresnel

1788 (Broglie, France) – 1827 (Ville d'Avray)

Fresnel (the ‘s’ is silent) was Biot’s protégé. Arago collaborated with him on the polarisation of light, and used Fresnel’s work on wave theory to take revenge on Biot for sabotaging his own earlier work. Poisson’s work proved Fresnel right, but to Poisson’s own embarrassment, since he’d been sure Fresnel was wrong and was personally antipathetic to him. Fresnel collaborated with his close friend Ampère on research in electro-magnetism, and corresponded with Young, who was also interested in wave theory. Prosper Mérimée was his young cousin: it is unclear whether they crossed paths meaningfully.

James Clerk Maxwell

1831 (Edinburgh) – 1879 (Cambridge, England)

Tait was a schoolfriend, in fact a friend for life. At 23, Maxwell famously provided the mathematical theorisation of Faraday’s more empirically-based electromagnetic work (though it overshadows all else, this was far from his only significant achievement). Thomson and Stokes were friends and mathematical-physics colleagues. He corresponded with Wheatstone on telegraphy, sent Gibbs a plaster model after reading his paper on the 3D representation of thermodynamics, and was a friend of Babbage’s. Airy also corresponded; he described a paper of Maxwell’s as “one of the most remarkable applications of mathematics to physics” he’d ever seen.

Hyppolite Fizeau

1819 (Paris) – 1896 (Venteuil)

Foucault was a schoolfriend; they both abandoned medical studies for physics. Fizeau studied with Arago and Regnault. He and Foucault worked together on the velocity of light following ideas suggested by Arago, whose eyesight was failing, but parted ways shortly before the crucial experiments (Fizeau got there first). They also took the first clear photo of the moon’s surface.

Humphry Davy

Humphrey Davy

1778 (Penzance, England) – 1829 (Geneva)

Davy’s close friends Coleridge and Southey, also Roget, participated in his laughing-gas experiments. Banks, Cavendish and Thompson offered him help in his electro-chemical researches. He wrote up Wedgwood’s photographic experiments and climbed Helvellyn with Wordsworth, Southey and Scott. Faraday became his assistant after he temporarily blinded himself, Davy claiming him as his greatest scientific discovery; on a two-year European journey, they visited Ampère, Hachette, Cuvier, Berthollet, Volta and the de la Rives, among others. Coleridge said he went to Davy’s lectures to increase his stock of metaphors.

George Stokes

1819 (Skreen, Ireland) – 1903 (Cambridge, England)

Stokes corresponded with Wheatstone on the chemistry of colour. Maxwell, as well as Thomson, became a friend and colleague at Cambridge; they collaborated for over 50 years. Thomson personally benefited from Stokes’ sharing of his ideas about spectroscopy, and pointed out that several important discoveries of Stokes’ were uncreditied to him as he’d never formally published them. Adam, Owen, Crookes, Tait, Herschel and Airy were among his frequent scientific correspondents.

Charles Wheatstone

1802 (Barnwood, England) – 1875 (Paris)

Wheatstone enjoyed a lifelong friendship with Faraday, who because of his acute shyness usually got Wheatstone to deliver his lectures for him. Roget was like Faraday an old friend. Ørsted, twice Wheatstone’s age, discussed Chladni figures with him on a London visit. Henry met Wheatstone (and Faraday) on a visit to Britain in 1837. Wheatstone corresponded with Siemens on electromagnetic resistance, with Stokes on the chemistry of colour, and with Maxwell on issues relating to telegraphy.

Albert Einstein

1874 (Ulm, Germany) – 1955 (Princeton, N.J.)

Einstein wrote to Perrin enthusiastically about Brownian motion. Curie was a good long-term friend and correspondent, Valéry met him several times, Bose and Schrödinger were important collaborators, Zweig (whom he admired) hosted him in Austria and co-signed a petition for arms limitation. Chaplin took Einstein (a fan) to the première of ‘City Lights’, Bohr and he held a long-running debate (they differed about randomness), Mann was a New Jersey neighbour, and Born (a great friend) played Beethoven duets with him. His conversation with Tagore was advertised as “two planets having a chat.”

Albert Einstein knew…