1925 | Science
Science
Nobel physicist Robert A. Millikan at the Pasadena Institute of Technology coins the term cosmic rays for radiation discovered more than a decade ago by Austrian-born physicist Victor Francis Hess, now 42, who found from repeated balloon ascents that radiation increased rapidly with altitude and suggested that they came from extraterrestrial sources. Now 57, Millikan confirms Hess's theory and uses it to help found a new branch of physics that will lead to advances in astrophysics, cosmology, and the discovery of fundamental particles (see Dirac, 1928; positron, 1932).
Vienna-born University of Hamburg physics lecturer Wolfgang Pauli, 25, porposes what will be called the "Pauli exclusion principle:" no two fermions may possess the same energy (i.e. occupy the same quantum state) in a given atom. Pauli crystallizes existing knowledge of atomic structure; his work will lead to a recognition of the two-valued variable needed to characterize the state of an electron.
German physicists Hans Geiger and Walter (Wilhelm Georg) Bothe, 34, at the University of Berlin devise a new method for detecting subatomic particles (see Geiger, 1908). Using Geiger counters to gather data on the Compton effect (the dependence of the increase in the wavelength of a beam of X-rays upon the angle through which the beam is scattered as a result of collision with electrons (see 1922; 1923), they measure the energies and directions of single photons and electrons emerging from individual collisions and establish the particle nature of electromagnetic radiation, refuting a statistical interpretation of the Compton effect (see Chadwick, 1932).
French naturalist Théodor André Monod, 23, crosses the Sahara on camelback and discovers Asselar Man—a human skeleton dating to neolithic times.
The National Research Endowment is established "to increase and strengthen American contribution to the mathematical, physical, and biological sciences." Secretary of Commerce Herbert C. Hoover is named chairman.
Physicist Oliver Heaviside dies at Torquay, Devon, February 3 at age 74; mathematician-logician Gottlob Frege at Bad Kleinen July 26 at age 76.