Success from Different Programs : The Development of Experimental Researches on Thermal Radiation in Germany at the End of the 19th Century

There were many historical studies on thermal radiation in Germany at the end of the 19th century, but they mainly treated the theoretical context of radiation research. In 1970, H. Kangro described the detailed development of black body experiments, and in 2001, D. Hoffmann looked at how the German physicist O. Lummer made the bolometer, a detector of radiation; however, there has been no comprehensive study of the development of radiation experiments and their instruments. This paper describes the progress of black body experiments, focusing on the development and improvement of key instruments, such as the galvanometer, the bolometer, the thermopile, and the cavity radiator, made by key German physicists, such as Lummer, W. Wien, H. Rubens, and F. Paschen. It concludes that the key physicists developed their special instruments in three main programs of experiments: standard-oriented, electromagnetic, and spectroscopic programs. The separate but interdependent development of these programs contributed to the approach of the non-classical theory of black-body radiation in 1900.