(b. Gleiwitz, Upper Silesia [now Gliwice, Poland], 5 September 1850; d. Berlin, Germany, 25 December 1930)
After attending Ratibor Gymnasium, Goldstein spent a year (1869–1870) at the University of Breslau. He then went on to the University of Berlin, where he worked with Helmholtz, taking his doctorate in 1881. He spent most of his exceptionally long professional career as a physicist at the Potsdam observantory. His first scientific paper was published in 1876, his last over fifty years later.
Almost all of Goldstein’s published work was on topics which sprang naturally from his lifelong interest in electrical discharges in moderate to high vacuums. He is now known primarily as the discoverer, in 1886, of “Kanalstrahlen,” as he called them—canal rays or positive rays, as they became known in English. He also made significant contributions to the study of cathode rays, which were discovered by Julius Plücker but named by Goldstein. Most of the rest of his work concerned various phenomena occurring in gaseous discharges.
In 1876 Goldstein showed that cathode rays could cast sharp shadows.1 He was able to demonstrate that they were emitted perpendicularly to the cathode surface, a discovery that made it possible to design concave cathodes to produce concentrated or focused rays, which were useful in a wide range of experiments. But this same discovery cast some doubt on the idea then prevailing among German physicists that the rays consisted of some form of electromagnetic radiation. Further, Goldstein and others showed in 1880 that the rays could be bent by magnetic fields;2 this discovery also gave aid and comfort to those physicists, predominantly British, who believed that the rays were streams of negative particles.
Sir William Crookes, for example, had suggested that the rays were charged “molecular torrents” rebounding from the cathode. To oppose this view, Goldstein conducted a series of experiments showing that cathode rays emitted light showing little if any Doppler shift and that they could traverse a distance some 150 times the mean free path for molecules at the pressures then being achieved in the discharge tube3.
Over a span of many years Goldstein published several papers on other aspects of cathode rays. He showed (1895–1898) that they could make certain salts change color, that they could be “reflected” diffusely from anodes (1882), and that there was some evidence for electrostatic deflection of parallel beams. However, his “reflection” experiment may have been misleading: the “reflected” rays may well have been soft X rays produced in the anode by the impinging cathode rays (but of course X rays had not yet been discovered). An exceptionally clever experimentalist, Goldstein studied the effects of a wide range of cathode and anode configurations.
In 1886 Goldstein published his discovery of “Kanalstrahlen,” rays which emerged from channels or holes in anodes in low-pressure discharge tubes4. His student Wilhelm Wien, who later became known primarily as a theoretical physicist, showed that the canal rays could be deflected by electric and magnetic fields, and that they had ratios of positive charge to mass approximately 10,000 times that of cathode rays5. When did not detect different ratios for different elements. The development of canal-ray apparatus into the important field of mass spectroscopy was, of course, carried out by others, notably J. J. Thomson and F. W. Aston.
Another of Goldstein’s students, Johannes Stark, was able to show that light from canal-ray particles showed a Doppler shift6. This was the first clear-cut demonstration of an optical Doppler shift in a terrestrial source.
Goldstein continued to publish papers on various canal-ray topics, notably studies of the wavelengths of light emitted by various metals and oxides when they were struck by the rays. He found, for example, that the alkali metals, when hit by the rays, emitted their characteristic bright spectral lines, while they did not do so when hit by cathode rays. He also found that a constriction in a discharge tube could function as a source of positive rays.
In the last two decades of his life Goldstein devoted much attention to anode discharges and to the striations of the positive column in low-pressure discharge tubes. Such tubes present a wealth of beautiful and fascinating phenomena, and Goldstein’s experimental virtuosity made it natural for him to pursue such topics. It is ironic that his work in these areas was of secondary importance and now is seldom mentioned in writings in the field, while his early work, and that of his students, was much more fundamental and lasting. But it is perhaps even more ironic that his last paper, published in 1928, reported detection of the synthesis of ammonia in discharge tubes containing various gases7. This virtually forgotten work foreshadowed an intriguing and interesting field of research that came to life over thirty years after Goldstein’s death.
1. Monatsberichte der Königlichen Akademie der Wissenschaften zu Berlin (1876), 284.
2.Wiedemann’s Annalen der Physik, 11 (1880), 850.
3.Philosophical Magazine, 10 (1880), 234, originally in Monatsberichte der Königlichen Akademie der Wissenschaften zu Berlin (Jan.1880).
4. “Über eine noch nicht untersuchte Strahlungsform an der Kathode inducirter Entladungeń,” in Sitzungsberichie der Königlichen Akademie der Wissenschaften zu Berlin,39 (1886), 691.
5. “Deflection of Canal Rays,” in Berlin Physikalische Gesellschaft Verhandlungen, 17 (1898), 10–12.
6. “Doppler Effect Exhibited by Canal Rays and the Spectrum of Positive Ions,” in Physikalische Zeitschrift,6 (1905), 892–897.
7. “Synthesis of Ammonia, Argon as Catalyst,” in Zeitschrift für Physik,47 (1928), 274.
I. Or1ginal Works. Most of Goldstein’s work was published in such journals as Wiedemann’s Annalen der Physik and Zeitschrift für Physik. Specific references can be found in Science Abstracts. A collection of papers was reprinted as no. 231 of Ostwald’s Klassiker der Exacten Wissenschaften (Leipzig, 1930).
II. Scondary Literature. As a tribute to Goldstein on his eightieth birthday, Rausch von Traubenberg wrote “Die Bedeutung der Kanalstrahlen für die Entwicklung der Physik,” in Naturwissenschaften, 18 (5 Sept. 1930), 773–776. See also E. Rüchardt,” Zur Entdeckung der Kanalstrahlen vor fünfzig Jahren,” and F. W. Aston, “Kanalstrahlen und Atomphysik,” both in Naturwissenschaften, 24 (24 July 1936), 465–469. Goldstein’s contributions to the understanding of cathode rays are briefly discussed in D. L. Anderson, The Discovery of the Electron (Princeton, 1964). A brief obituary note appeared in Nature, 127 (1931), 171.
David L. Anderson