During the present economic turmoil it may be tempting to make an analogy between energy and money — not least as a reminder that neither can be generated arbitrarily. Few physicists nowadays would use such a comparison to explain the fundamental principle of energy conservation, but in the second half of the nineteenth century scientists would often do so, and try to explore its ramifications. Such anthropomorphic references, however, have long since given way to firm, quantitative descriptions. Daan Wegener now describes the 'de-anthropomorphizing' of energy and energy conservation by considering the cases of the Austrian physicist and philosopher Ernst Mach (pictured) and his German colleague, and opponent, Max Planck (Studies in History and Philosophy of Modern Physics doi: 10.1016/j.shpsb.2010.02.001; 2010).

Credit: © ÖSTERREICHISCHE NATIONALBIBLIOTHEK

The relationship between Mach and Planck is typically discussed in the context of their disagreement about the reality of atoms, which Mach was reluctant to accept. Planck heavily criticized Mach's view that atoms are merely theoretical constructs, and Planck would of course be proven right. However, that victory, Wegener argues, does not imply a defeat of Machian philosophy altogether.

In his analysis of their views on the law of energy conservation, Wegener has spotted a range of similarities between Planck and Mach, starting from both men's belief that the law is valid and fundamental, to their scepticism towards philosophical speculations (and both found analogies between energy and money not to be useful). But whereas Mach and Planck both aimed at a “de-mystification and purification of the basic concepts of science, such as energy”, they phrased the law of energy conservation in slightly different ways, Wegener finds.

These differences, subtle as they are, highlight the fundamentally different outlooks on science that Mach and Planck had. Planck's motivation was mainly to establish theoretical physics as a profession of its own, distinct from metaphysics (and mathematics). He avoided any reference to “human or technical perspectives”, and considered the laws of nature to be valid independent of human existence. In contrast, the view of Mach — the “philosopher, historian and sociologist of science” — must be seen in a much broader context, Wegener argues, in which science interacts with society and industry. For Mach, conservation of energy followed from a principle of causality (an argument that is free of anthropomorphic elements) and empirical meaning could come only through the actual practice of science and in the context of historical developments.