SEEBECK, THOMAS

(b. Tallinn, Estonia, 9 April 1770; d. Berlin, Germany, 10 December 1831)

electricity, magnetism, optics.

Thomas Seebeck, the discoverer of thermoelectricity and one of the most distinguished experimental physicists of the early nineteenth century, was born in Estonia, to a well-to-do merchant family. After graduating from a Gymnasium he studied medicine at Berlin and at the University of Göttingen, receiving an M.D. from the latter in 1802. As a student Seebeck developed a strong interest in the natural sciences and decided to devote himself to scientific research rather than to medical practice. He married in 1795 and shortly thereafter began the career of a rich scientific enthusiast.

As a natural philosopher Seebeck was attracted to Jena, where an important intellectual circle was developing in the early 1800’s around the philosophers Schelling and Hegel, the scientists Ritter and Oken, and the poet-philosopher Goethe. Here, partly inspired by Goethe’s anti-Newtonian theory of colors (the Farbenlehre), Seebeck undertook his first research in optics in 1806. Its goal was to investigate the heating and chemical effects of the different colors of the solar spectrum.

Several scientists before Seebeck—Marsiglio Landriani, A. M. de Rochon, William Herschel, and John Leslie—had examined the heating effects of rays of different colors, and Herschel had shown in 1800 that heating could be detected in the region beyond the red end of the visible spectrum. Seebeck confirmed Herschel’s finding and added to it the discovery of a slight rise in temperature beyond the violet region. He also found that the position of the point of greatest heat in the spectrum varied with the nature of the prism producing the colors. Seebeck also repeated and expanded upon Ritter’s experiments on the coloration effects of different rays on silver salts.

Malus’s discovery of polarization in 1808 led Seebeck to his next research in optics. In 1812 and 1813 he observed the “entoptic” patterns in pieces of glass under stress or subject to uneven heating and viewed through a polarizer. He also discovered optical rotatory polarization in certain oils, the power of tourmaline to produce a single polarized ray of light, and the system of colored rings produced in polarized light by Iceland spar cut orthogonal to its axis. All these discoveries, unfortunately, were partially anticipated by Brewster or Biot. Nonetheless, Seebeck shared the Paris Academy of Science’s annual prize in 1816 for his work on polarization in stressed glass, and was elected to the Berlin Academy in 1814.

In the 1820’s Seebeck, having moved to Berlin, became interested in the phenomena of magnetism. He repeated the discovery made independently by Arago and Davy, that an electric current can induce magnetism in iron and steel, and that a steel needle is strongly magnetized when drawn around a conductor. Next, he expanded upon Arago’s discovery that the oscillations of a magnetized iron needle about the magnetic meridian can be damped by placing a slab of almost any material in the immediate vicinity. He performed a large number of experiments on the magnetizability of different metals and first noticed the anomalous behavior of magnetized red-hot iron, an early indication of the phenomenon known as hysteresis.

By far Seebeck’s most significant discovery, however, was that of thermoelectricity—or thermomagnetism, as he called it—in 1822. While he was studying the influence of heat on galvanic arrangements, it occurred to him that heat might create magnetism in two different metals joined to form a closed circuit. He joined a semicircular piece of bismuth with a similar piece of copper and fastened the ends together to form a circle. When heat was applied to either of the bismuth-copper junctions, a magnetic needle placed nearby behaved as if the circle were a closed, current-carrying circuit. By repeating this experiment many times with different pairs of metals and other conductors, Seebeck was able to order the various conducting materials in a thermoelectric series with bismuth at the extreme negative end and tellurium at the extreme positive end. He did not, however, believe that an electric current was actually set up in the bimetallic rings and preferred to describe his effect as “thermomagnetism.”

BIBLIOGRAPHY

I. Original Works. Seebeck’s studies on the heating effects of the solar spectrum are presented in “Über die ungleiche Erregung der Wärme in prismatischen Sonnenbilde,” in Abhandlungen der Preussischen Akademie derWissenschaften (1818–1819), 305–350. His work on the chemical effects of different colored rays appears in Journal für Chemie und Physik, 2 (1811), 263–264. The two memoirs on polarized light are “Einige neue Versuche und Beobachtungen über Spiegelung und Brechung des Lichtes,” ibid., 7 (1812), 259–298, 382–384; and “Von den entoptischen Farbenfiguren und den Bedingungen ihrer Bildung in Gläsern,” ibid., 12 (1814), 1–16. His discovery of thermoelectricity is described in “Magnetische Polarisation der Metalle und Erze durch Temperatur-Differenz,” in Abhandlungen der Preussischen Akademie der Wissenschaften (1822–1823), 265–373. Other works are listed in the Royal Society Catalogue of Scientific Papers, V. 620–621; and at the end of Poggendorff’s “Gedachtnissrede auf T.J. Seebeck” (see below).

II. Secondary Literature. The only substantial biography of Seebeck is J.C. Poggendorff, “Gedachtnissrede auf Thomas Johann Seebeck. gehalten in den öffentlichen Sitzung vom 7 Juli 1839,” in Abhandlumgen der Preusstschen Akedemie der Wissenchaften (1841), xix-xxvii, Encyclopaedia Britannica, 7th ed. (1842), contains brief discussions of Seebeck’s principal discoveries in electromagnetism, VIII, 574, and XXI, 684: thermoelectricity, VIII, 574, and XXI, 695: the prismatic spectrum. XIII, 332: magnetism, XIII, 694, 709, 712; and optics, XIII, 370, 420,464.

Eugene Frankel