Eugen Goldstein
Eugen Goldstein was a German physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...

. He was an early investigator of discharge tubes, the discoverer of anode rays, and is sometimes credited with the discovery of the proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....



Goldstein was born in 1850 at Gleiwitz Upper Silesia, now known as Gliwice, Poland. He studied at Breslau and later, under Helmholtz, in Berlin. Goldstein worked at the Berlin Observatory from 1878 to 1890, but spent most of his career at the Potsdam Observatory, where he became head of the astrophysical section in 1927. He died in 1930 and was buried in the Weißensee Cemetery
Weißensee Cemetery
The Weißensee Cemetery is a Jewish cemetery located in the neighborhood of Weißensee in Berlin, Germany. It is the second largest Jewish cemetery in Europe. The cemetery covers approximately and contains approximately 115,000 graves. It was dedicated in 1880....

 in Berlin.


In the mid-nineteenth century, Julius Plücker
Julius Plücker
Julius Plücker was a German mathematician and physicist. He made fundamental contributions to the field of analytical geometry and was a pioneer in the investigations of cathode rays that led eventually to the discovery of the electron. He also vastly extended the study of Lamé curves.- Early...

 investigated the light emitted in discharge tubes (Crookes tube
Crookes tube
A Crookes tube is an early experimental electrical discharge tube, invented by English physicist William Crookes and others around 1869-1875, in which cathode rays, that is electrons, were discovered....

s) and the influence of magnetic fields on the glow. Later, in 1869, Johann Wilhelm Hittorf
Johann Wilhelm Hittorf
Johann Wilhelm Hittorf was a German physicist who was born in Bonn and died in Münster, Germany.Hittorf was the first to compute the electricity-carrying capacity of charged atoms and molecules , an important factor in understanding electrochemical reactions...

 studied discharge tubes with energy rays extending from a negative electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...

, the cathode. These rays produced a fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation of a different wavelength. It is a form of luminescence. In most cases, emitted light has a longer wavelength, and therefore lower energy, than the absorbed radiation...

 when they hit a tube's glass walls, and when interrupted by a solid object they cast a shadow.

In the 1870s Goldstein undertook his own investigations of discharge tubes, and named the light emissions studied by others kathodenstrahlen, or cathode ray
Cathode ray
Cathode rays are streams of electrons observed in vacuum tubes. If an evacuated glass tube is equipped with two electrodes and a voltage is applied, the glass opposite of the negative electrode is observed to glow, due to electrons emitted from and travelling perpendicular to the cathode Cathode...

s. He discovered several important properties of cathode rays, which contributed to their later identification as the first subatomic particle, the electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

. He found that cathode rays were emitted perpendicularly from a metal surface, and carried energy. He attempted to measure their velocity by the Doppler shift of spectral lines in the glow emitted by Crookes tubes.

In 1886, he discovered that tubes with a perforated cathode also emit a glow at the cathode end. Goldstein concluded that in addition to the already-known cathode rays, later recognized as electrons moving from the negatively-charged cathode toward the positively-charged anode
An anode is an electrode through which electric current flows into a polarized electrical device. Mnemonic: ACID ....

, there is another ray that travels in the opposite direction. Because these latter rays passed through the holes, or channels, in the cathode, Goldstein called them kanalstrahlen, or canal rays. They are composed of positive ions whose identity depends on the residual gas inside the tube. It was another of Helmholtz's students, Wilhelm Wien
Wilhelm Wien
Wilhelm Carl Werner Otto Fritz Franz Wien was a German physicist who, in 1893, used theories about heat and electromagnetism to deduce Wien's displacement law, which calculates the emission of a blackbody at any temperature from the emission at any one reference temperature.He also formulated an...

, who later conducted extensive studies of canal rays, and in time this work would become part of the basis for mass spectrometry
Mass spectrometry
Mass spectrometry is an analytical technique that measures the mass-to-charge ratio of charged particles.It is used for determining masses of particles, for determining the elemental composition of a sample or molecule, and for elucidating the chemical structures of molecules, such as peptides and...


The anode ray with the smallest e/m ratio comes from hydrogen gas (H2), and is made of H+ ions. In other words this ray is made of protons. Goldstein's work with anode rays of H+ was apparently the first observation of the proton, although strictly speaking it might be argued that it was Wien who measured the e/m ratio of the proton and should be credited with its discovery.

Goldstein also used discharge tubes to investigate comets. An object, such as a small ball of glass or iron, placed in the path of cathode rays produces secondary emissions to the sides, flaring outwards in a manner reminiscent of a comet's tail. See the work of Hedenus for pictures and additional information.

Further reading

  • Hedenus, M., Der Komet in der Entladungsröhre, 2007, GNT-Verlag
  • Brief obituary of Eugen Goldstein, Nature, 1931, volume 127, page 171
  • Goldstein, E., "Über eine noch nicht untersuchte Strahlungsform an der Kathodeinducirter Entladungen" in Berlin Akd. Monatsber. II, 1886, page 691
  • Goldstein, E., "Vorläufige Mittheilungen über electrishe Entladungen Verdünnten Gasen" in Berlin Akd. Monatsber., 1876, page 279|url=|format=PDF|accessdate=2007-09-11
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