A Signed Photograph of Albert Einstein with Fellow Physicist Rudolf Ladenburg, His Friend from His Days as a Patent Clerk, at the Symposium in Honor of Professor Ladenburg’s Retirement

Rudolf Ladenburg earned his doctorate in 1906 at Heidelberg under the direction of Wilhelm Röntgen. After working at the physics institute at the University of Breslau, Ladenburg became the chief of the physics division at the Kaiser Wilhelm Institute. His research explored dispersion lines in atomic spectra, and his most original work was on the anomalous dispersion of gases. Ladenburg also investigated hydrogen in excited states. A German Jew who sensed the way the wind was blowing, circa 1932 he went to Princeton, where he later succeeded Karl Taylor Compton at the Palmer Laboratory. After he came to Princeton his interest turned to nuclear physics. Ladenburg helped many German scientists come to the US and find employment in the 1930s.

It is believed that Albert Einstein first met Ladenburg 1909 in Bern, when Einstein was still working at the Swiss Patent Office. They had at that time been corresponding for years. There Ladenburg urged him to leave the Patent Office for a career in physics and academia, which Einstein did that very year. Einstein followed Ladenburg to the United States, and to Princeton, in 1933. Einstein’s new workplace was the Institute for Advanced Study to which he stayed loyal until his death in 1955. The two men remained friends until Ladenburg’s death in 1952, almost half a century from their first contact.

An 8 by 10 inch photograph of Einstein sitting next to Ladenberg at the May 20, 1950, symposium in Princeton in honor of Ladenburg’s retirement, signed “A. Einstein, 1950”, which Einstein presented to Ladenburg. We obtained this photograph directly from the Ladenburg descendants, and it has never before been offered for sale.