Physician and physicist — Julius Robert von Mayer (Heilbronn 1814 – 1878) was a German physician and physicist, among the first to formulate the principle of conservation of energy. During a voyage as a ship’s doctor in the tropics he noticed that the sailors’ venous blood was redder than usual, and from this deduced a link between body heat, work and diet, an insight that led him to the idea of the equivalence between heat and mechanical work. In 1842 he published an estimate of the so-called mechanical equivalent of heat, partly anticipating Joule’s work. His ideas, expressed in a not very technical form, were long ignored by the scientific community. Only late in life was he recognised as a pioneer of the first law of thermodynamics.

Theories and contributions

  • Conservation of energy — Energy is neither created nor destroyed but transformed; the basis of the first law of thermodynamics.
  • Mechanical equivalent of heat — Heat and work are forms of the same quantity: 1 cal4,18 J1\ \text{cal}\approx 4{,}18\ \text{J}.

Linked atoms

5 linked atoms.

04 Energia e lavoro

10 Trasformazioni irreversibili e bilancio energetico