Wealth inequality, a topic of much current concern, is an inevitable consequence of the laws of physics. That’s the conclusion of a study by Adrian Bejan of Duke University in the US and Marcelo Errera of the Federal University of Paraná in Curitiba, Brazil, who have related the distribution of wealth to what they call “the movement of all streams” of a live society. This corresponds to the actual physical movement of masses over distances and can be defined in various ways, such as the amount of fuel consumed annually, all of which lead to the same scaling behaviour. This naturally produces a hierarchical distribution of wealth that becomes more accentuated as the economy develops, and predicts the Lorenz-type distribution of wealth that has been adopted empirically for the last century.