Gustav Robert Kirchhoff
Gustav Robert Kirchhoff (b. Konigsberg, Germany, 12th March 1824, d. Berlin, Germany, 17th October 1887) was a physicist. His father was a law councillor. Kirchhoff easily derived Kirchhoff's voltage law for electrical network analysis between 1845-1846, while he was still a student at Konigsberg. In 1849, following the experiments of Kohlrausch, he introduced Kirchhoff's current law for electrical network analysis. He graduated in 1847 and married Clara Richelot, the daughter of one of his teachers, the same year. Three years later, he was appointed professor at Breslau. In 1854, he moved to Heidelberg, where Robert Bunsen was a professor of chemistry. In 1869, Clara died, leaving him two sons and two daughters. In 1872, he married Luise Brommel.
In 1859, he published an explanation of the dark lines in the sun's spectrum, discovered by Josef von Fraunhofer. In the course of investigating the optical spectra of chemical elements, Kirchhoff made his major contribution to science which was his experimental discovery and theoretical analysis of a fundamental law of electromagnetic radiation which states that for all material bodies, the ratio of absorptive and emissive power of radiation is a universal function of wavelength and temperature. In 1860, Bunsen and Kirchhoff discovered that each chemical substance emits light that has its own unique pattern of spectral lines. A Few months later, they discovered a new metal, cesium and the next year, they found rubidium. They also constructed an improved form of the spectroscope. Kirchhoff once told his bank manager of the discovery of terrestrial metals of the sun. The bank manager said, "Of what use is gold on the sun if I cannot get it down to earth?" later, after Queen Victoria of England had presented Kirchhoff with a medal and a prize in gold sovereigns for work on the sun's spectrum, he took them to the bank manager and said, "Here is some gold from the sun!"
Kirchhoff was crippled by an accident in mid-Iife which compelled him to use crutches and wheelchair. But, he remained in good spirit. On two occasions he turned down calls to other universities. Only when his failing health hindered his experimental work did he accept a chair of theoretical physics offered to him in Berlin. He worked there with great devotion, until illness forced him to give up his teaching activity in 1886. He bore with patience the long illness of his last years. He died peacefully, presumably of a cerebral congestion.
