Background
Ferdinand Kurlbaum was born on October 4, 1857, in Burg, Germany. He was the son of a judicial officer.
Humboldt University of Berlin, Berlin, Germany
As a result of scholastic difficulties, Kurlbaum did not enter the university until he was twenty-three. After only eight semesters, however, he began an important dissertation under the supervision of Heinrich Kayser in Helmholtz’s laboratory. This work, completed in 1887, contained a new determination of the wavelengths of thirteen Fraunhofer lines of the solar spectrum.
1907
Ferdinand Kurlbaum, 1907, photo by Rudolf Dührkoop.
Humboldt University of Berlin, Berlin, Germany
As a result of scholastic difficulties, Kurlbaum did not enter the university until he was twenty-three. After only eight semesters, however, he began an important dissertation under the supervision of Heinrich Kayser in Helmholtz’s laboratory. This work, completed in 1887, contained a new determination of the wavelengths of thirteen Fraunhofer lines of the solar spectrum.
German Physical Society, Berlin, Germany
Kurlbaum was president of the German Physical Society from 1910 to 1912.
Ferdinand Kurlbaum was born on October 4, 1857, in Burg, Germany. He was the son of a judicial officer.
As a result of scholastic difficulties, Kurlbaum did not enter the university until he was twenty-three. After only eight semesters, however, he began an important dissertation under the supervision of Heinrich Kayser in Helmholtz’s laboratory. This work, completed in 1887, contained a new determination of the wavelengths of thirteen Fraunhofer lines of the solar spectrum.
When Kayser was called to Hannover, Kurlbaum went with him as his assistant. In 1891 Kurlbaum moved to the Technical University of Berlin in Berlin. At first, he worked in the optical laboratory, which was directed by Otto Lummer. In 1893 Kurlbaum modified the bolometer in such a way that it was capable of making absolute measurements of radiation intensities.
In 1898 Lummer and Kurlbaum published, in the Verhandlungen der Physikalischen Gesellschaft zu Berlin, their famous work in which they described the radiation-containing hollow body in the form that is still customary: an electrically heated platinum cylinder, blackened on the inside with iron oxide and enclosed in an outer asbestos cylinder. In the same year, Kurlbaum provided an absolute measure of blackbody radiation which was tantamount to determining the Stefan-Boltzmann constants to an accuracy of 5 percent.
In 1894 Kurlbaum was named an assistant at the Technical University of Berlin; and in October 1899, at the proposal of the president, F. W. G. Kohlrausch, he received the title of “professor.” At the invitation of Heinrich Rubens, Kurlbaum participated in the latter’s measurements of the radiation intensity of the blackbody in the case of extremely long waves (residual radiation of fluorite and of rock salt). Lummer and Pringsheim had already questioned the validity of Wien’s law of radiation; but the decisive break came, as Max Planck later expressly stated, only with Rubens’ and Kurlbaum’s long-wave measurements. Kurlbaum communicated the results at the meeting of the German Physical Society held in Berlin on October 19, 1900. It followed from their findings that at high temperatures the radiation intensity of the blackbody is proportional to the absolute temperature, as Rayleigh had already written in June 1900 in Philosophical Magazine. This result, which stood in obvious contradiction to Wien’s law of radiation, was known to Planck on October 7, through a verbal communication from Rubens; the discovery of his own radiation law followed in the middle of October. Directly after Kurlbaum gave his report, Planck presented his new formula: quantum theory had begun. Arnold Sommerfeld observed in 1911: “It will always remain a famous page in the history of the first decades of the Technical University of Berlin that it erected one of the pillars of the quantum theory, the experimental bases of hollow-space radiation.” One may add that Kurlbaum immortalized his name on this “famous page.”
In 1901 Kurlbaum took charge of the high-voltage laboratory in the “second division” of the Technical University of Berlin, where the principal activity was the testing of apparatus. His own endeavors, however, continued to be devoted primarily to the measurement of radiation. With Ludwig Holborn, he constructed a filament pyrometer that was capable of measuring arbitrarily high temperatures in a brilliantly simple way and with great precision.
In the fall of 1904 Kurlbaum was appointed a full professor at the Technical College of Berlin-Charlottenburg, as a successor to C. A. Paalzow. He worked at first with Heinrich Rubens. After the latter’s departure, the main burden of teaching fell to Kurlbaum, and he carried out no further personal research at the Technical College.
Kurlbaum was president of the German Physical Society from 1910 to 1912.
Kurlbaum married Elisabeth von Siemens in 1895. They had two daughters and a son.