An unpublished lecture by Heinrich Hertz: 'On the energy balance of the earth.'

This paper presents a recently discovered and newly translated manuscript of a lecture by Heinrich Rudolf Hertz, long famous for his 1888 discovery of long-wavelength electromagnetic waves. Hertz delivered this address on 20 April 1885 as his inaugural lecture to the faculty at the Technische Hochschule in Karlsruhe (now the Universitat Karlsruhe), where he was to make his most important contributions to physics. Although written over 110 years ago, this historical document records both Hertz's insightful view of the Earth's energy situation at that time and his remarkably good order-of-magnitude estimates of the energy sources then known to be available to the Earth.