Gustav Kirchhoff was the German physicist who invented the technique of spectroscopy and discovered laws governing the flow of electricity in circuits. Kirchhoff made his first important contribution to science when he was still a student at the University of Königsberg: he devised Kirchhoff's laws, which determine the current and potential difference at any point in an electrical circuit. He later moved to Berlin (1848) where he began collaborating with Robert Bunsen. Both then moved to Heidelberg where in the 1850s Bunsen developed his famous burner. Bunsen had noted that when held in a flame, metals and their salts produced a variety of colours. Kirchhoff suggested that by using a prism, the spectra of these coloured flames could be analysed and used to identify the substances. A spectroscope was developed and in 1860 they both began classifying the elements by spectral analysis. More importantly, Kirchhoff used this spectral analysis to identify the elements in the Sun's spectrum and to explain Fraunhofer's lines (now an important technique used to determine the composition of stars). In 1859 Kirchhoff formulated his laws of radiation, stating that the emission and absorption powers were the same for all bodies at a given temperature and wavelength of radiation. It was work that led to the concept of the ideal black body (1862) which was important in the development of quantum theory.
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