Egyptian stars under Paris skies

One evening in early July of 1822 a group gathered for dinner at the home of the leading figure in French science, the Marquis de Laplace, outside Paris. The guests included five of the most distinguished physicists and chemists of the day: Jean-Baptiste Biot, famed for his experimental work in optics and electricity; François Arago, rapidly becoming an influential administrator of science, the editor of an important journal, and himself a reasonably accomplished experimenter in optics; Joseph Fourier, who had developed the series representation now termed Fourier analysis and whose controversial theory of thermal diffusion had already been widely discussed; the influential chemist Claude Berthollet; and John Dalton, the English protagonist of the atom.

The previous several years had seen remarkable developments in French science, including fundamental discoveries in electricity, magnetism, heat, and optics. Most of the dinner guests had participated in these events, often on opposing sides. Biot and Arago were scarcely on speaking terms, Fourier’s mathematics and his heat theory were not well thought of by Biot and Laplace, and Berthollet had little sympathy for chemical atomism. Yet the evening’s conversation had nothing to do with physics, chemistry, or mathematics. Instead, the guests discussed the arrival in Paris of a zodiac from a ceiling in the Egyptian temple of Dendera, far up the Nile. Sawn and exploded out of its site by a French archaeological vandal named Claude Lelorrain, the Dendera zodiac roused Parisian salons and institutes to such an extent that for several months it displaced all other topics, attracted crowds of curious admirers, and was soon bought by King Louis XVIII for an immense sum.

This was not the first time that Dendera had ignited discussion. On his return from Napoleon’s colonial expedition to Egypt in 1799, the artist Vivant Denon had made available his sketch of what certainly looked like a zodiac.