Camille Flammarion and the Second Principle of Thermodynamics

In Camille Flammarion’s book La fin du monde, published in 1894, we find an impressive picture: Some poorly dressed people, including a mother with her child, are shivering with cold in an extremely hostile environment of ice and snow. In two wide-spread German history of science textbooks, this picture is given as an illustration of the pessimistic conclusions that some nineteenth century physicists (among them Hermann von Helmholtz) had drawn from the Second Principle of Thermodynamics. They believed that in a remote future, the entropy of the universe would grow to a maximum, and all available energy would be transformed into heat. This apocalyptic vision was often called "heat death", but as the average temperature would then be very low, the expression "cold death" was used as well. By analysing Flammarion's text, it is shown that he was not a supporter of this vision of the end of the world. According to Flammarion, mankind would die of cold as a consequence of the lack of water vapour in the atmosphere, and this would occur about twenty million years before the exhaustion of the sun as a source of energy. The use of this picture as an illustration of the heat death (or cold death) theory derived from thermodynamics is a misinterpretation that reminds of the erroneous assumptions that were expressed with regard to another picture by Flammarion. An illustration stemming from L’Atmosphère: Métérologie populaire (Paris 1888) was for many years (and sometimes is still) falsely considered as a medieval German woodcut.