Prévost, Pierre (1751–1839)

Swiss physicist who first showed, in 1791, that all bodies radiate heat, no matter how hot or cold they are. In challenging the notion then prevalent that cold was produced by the entry of cold into an object rather than by an outflow of heat, Prévost made a basic advance in our knowledge of energy.

Prévost was born in Geneva and studied and travelled widely. For a year he was professor of literature at Geneva, then worked in Paris on the translation of a Greek drama. Returning to Geneva 1786, he became active in politics as well as carrying out research into magnetism and heat. He was professor of philosophy and general physics at Geneva 1793–1823. In his later years, Prévost chose to study the human ageing process. He used himself for his observations, noting down in detail every sign of advancement that his mind, body, and mirror showed.

Prévost found by experiment that dark, rough-textured objects give out and absorb more radiation than smooth, light-coloured bodies, given that both are at the same temperature. He conceived of heat as being a fluid composed of particles and this led to Prévost's theory of heat exchanges. If several objects at different temperatures are placed together, they exchange heat by radiation until all achieve the same temperature. They then remain at this temperature if they are receiving as much heat from their surroundings as they radiate away.