2 - Planck and black-body radiation

Summary

The key role of experimental technique

1895 was not an arbitrary choice as the cut-off year for the history recounted in Chap. 1. Over the following years a number of experimental discoveries were made which were to change dramatically the face of physics. The origins of these discoveries can be traced to the need for increased precision in experimental physics. The industrial revolution and the widespread availability of electricity and electrical communication required more exact understanding of the physical properties of materials and also the establishment of international standards. These necessitated a much more professional approach to the teaching of experimental physics and its associated theory. As part of that movement the Clarendon Laboratory was founded in Oxford in 1868 and the Cavendish Laboratory in Cambridge in 1874. Of particular significance for this chapter was the foundation of the Physikalisch-Technische Reichsanstaldt in Berlin in 1887 with the task of providing precise measurements of the physical properties of materials which would be of importance to industry. There was an expectation that these laboratories would develop new techniques for undertaking precision measurements.

New experimental techniques were developed thanks to the development of new technologies. To mention only a few of the more important of these, better vacuums were available to physicists through the invention of the Geissler pump, invented by Johann Heinrich Wilhelm Geissler, a brilliant inventor and glass-blower, in about 1855. The vacuum was produced by trapping air in a mercury column and forcing it down the column by the force of gravity.