Joseph F. Mulligan

Who were Fabry and Pérot

In 1897 Charles Fabry and Alfred Perot published their most important article on what we now call the Fabry–Perot interferometer. Despite the great importance of this instrument for present-day research in physics and astrophysics, its inventors are almost completely unknown to most physicists. This article presents brief accounts of the life and work of Fabry and Perot, who at the beginning of the twentieth century were highly regarded by physicists throughout the world for their contributions to optics and spectroscopy. Later they also made many important contributions to astrophysics, including Fabry’s 1913 discovery (with Henri Buisson) of the ozone layer in the Earth’s atmosphere.

Some Recent Determinations of the Velocity of Light. II

A number of important measurements of the velocity of light have been made in recent years. Four of these determinations are here outlined, with emphasis on the experimental techniques used. These include the work of Essen, and of Hansen and Bol, with microwave cavity resonators, Bergstrands measurements with a modified Kerr-cell technique, and Aslaksons “Shoran” measurements. It is pointed out that these four determinations are consistent among themselves and yield a value very close to 299,790 km/sec for the velocity of light in vacuum. This is completely outside the probable error of the value 299,776±4 km/sec generally accepted by physicists in the years 1934–1949 on the basis of rotating mirror and Kerr-cell measurements. Some possible reasons for this discrepancy are discussed.

An unpublished lecture by Heinrich Hertz: “On the energy balance of the Earth’’

This paper presents a recently discovered and newly translated manuscript of a lecture by Heinrich Rudolf Hertz, long famous for his 1888 discovery of long-wavelength electromagnetic waves. Hertz delivered this address on 20 April 1885 as his inaugural lecture to the faculty at the Technische Hochschule in Karlsruhe (now the Universitat Karlsruhe), where he was to make his most important contributions to physics. Although written over 110 years ago, this historical document records both Hertz’s insightful view of the Earth’s energy situation at that time and his remarkably good order-of-magnitude estimates of the energy sources then known to be available to the Earth.

The Atomic Scientists: A Biographical History

This presentation brings to life the thoughts, battles, and breakthroughs of the figures that made science history, from Lucretius to Feyman. It contains over 100 biographies in all, covering the most notable thinkers, and many important but little-remembered contributors to the rise of atomic theory. The chronological format and broad historical sweep give this fascinating account special value as a reference source.

The influence of Hermann von Helmholtz on Heinrich Hertz’s contributions to physics

Heinrich Hertz, the discoverer of radio‐frequency electromagnetic radiation, also made important contributions to our knowledge of the photoelectric effect, cathode rays, electromagnetic theory, classical mechanics, and meteorology. In 1878 Hertz enrolled at the University of Berlin to study physics under Professor Hermann von Helmholtz. For the rest of his life he maintained a very close personal and scientific relationship with his mentor. The influence of Helmholtz on Hertz’s choice of research topics and on the kind of physicist Hertz became is documented from the writings of these two famous physicists.

Emil Wiechert (1861–1928): Esteemed seismologist, forgotten physicist

Emil Wiechert was well known during his lifetime as Professor of Geophysics at the Georg-August-Universitat in Gottingen and Director of the Geophysical Institute there. He made many significant contributions to geophysics and seismology, and is highly respected by present-day geophysicists for his research and organizational contributions to the development of geophysics and seismology as major scientific disciplines. On the other hand, his contributions to fundamental physics—cathode rays, the discovery of the electron, the Lienard–Wiechert potentials, his electron theory—are unknown to many physicists today. This article presents Wiechert’s life, achievements in physics, and relationship to well-known physicists like Arnold Sommerfeld, Hendrik Lorentz, and Woldemar Voigt, to enable contemporary physicists to know better Wiechert’s important contributions to pure physics, and to appreciate more fully his role in the history of physics.

The Aether and Heinrich Hertz's The Principles of Mechanics Presented in a New Form

Abstract. The luminiferous aether played an important role in the careers of one of the greatest of nineteenth-century physicists, Heinrich Hertz (1857–1894). This paper demonstrates from Hertzs own writings the maturing of his interest in the aether during the years 1885–1894 until he finally considered the nature of the aether the most important problem remaining to be solved by physicists. This conviction, joined to his desire to reduce all physics to mechanics, eventually led Hertz to devote the last three years of his life (1891–1894) to his The Principles of Mechanics Presented in a New Form, a work he intended as preparatory to an all-out attack on the nature and functions of an aether. The reason why, after Hertzs premature death in 1894, physicists gradually lost interest in both his Mechanics and in the aether are discussed.

Hermann von Helmholtz and his students

During the years 1871–1888, when Hermann von Helmholtz was professor of physics at the University of Berlin, physicists from all over the world flocked to Berlin to study and do research with him. Among these were the German physicists Max Planck, Heinrich Kayser, Eugen Goldstein, Wilhelm Wien, and Heinrich Hertz, and Americans Henry Rowland, A. A. Michelson, and Michael Pupin. Examples of Helmholtz’s scientific and personal interactions with these students and research associates show why he is justly considered the outstanding physics mentor of the 19th century. Both his ideas and his students played a major role in the development of physics in the late 19th and early 20th centuries.

The Reception of Heinrich Hertz’s Principles of Mechanics by His Contemporaries

For present-day physicists Heinrich Hertz’s Principles of Mechanics is a neglected, almost forgotten, book. For example, few recent textbooks on mechanics make even passing reference to Hertz’s fundamental law [Grundgesetz] of the straightest path, which is the foundation of his Principles of Mechanics.1 Since Hertz’s Electric Waves had received an enthusiastic reception from physicists when it first appeared in 1892, and is still important today, it is difficult at first to understand this lack of interest in his book on mechanics, which appeared just two years later. This paper suggests that a major factor in the neglect of Hertz’s Mechanics was the unenthusiastic and often quite negative response to his book by some of the most important physicists of his time.

Max Planck and the ‘‘black year’’ of German physics

1994 is the hundredth anniversary of what Max Planck described in 1935 as the ‘‘black year’’ of German physics. In the eight months between January 1st and September 8th 1894, Heinrich Hertz, August Kundt, and Hermann von Helmholtz died. This article reviews the lives of these three important physicists, their research contributions, and their unique positions in the German physics community. In conclusion, the relationships of these three physicists to Planck are discussed, and Planck’s evaluation of the impact of 1894 on physics in Germany is appraised from our perspective of one hundred years.