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EINSTEIN, Albert (1879-1955). Autograph letter signed ('Papa') to his sons Hans Albert and Eduard ('Liebe Buben'), n.p., 4 March 1922, small autograph diagram showing the paths of light rays in an experiment, 2 pages, 4° (some smudging on recto).
A fine letter on gyroscopes, refrigerators and quantum theory. Einstein describes his work on a gyroscopic compass, for which electrolyte fluid ('Elektrolyflüssigkeit') has proved insufficiently stable, so that they have had to fall back on using water; but 'the electrical set-up which I suggested has proved very satisfactory'. His work on a refrigerator is making progress too: they are attempting to obtain a commission from a local firm; the situation with the patent is however still murky. He ends by describing an experiment with cathode rays falling on a mica surface, and causing the surface to glow: the light is emitted in part directly, and in part after reflection from the inner surface. 'The question is whether the two beams interfere. The experiment is simple, as long as the surface doesn't become too hot'.
A startling example of the range of Einstein's interests at any moment. He was working on the gyroscope in collaboration with a navigational instruments firm, Anschutz, based in Kiel: the device was perfected by 1927, and proved markedly superior to older models, being employed in a number of navies, including the German, Italian, French and Japanese. The design for a noiseless refrigerator, on which he worked together with Leo Szilard, was a project that was still preoccupying him in 1928. The experiment with light rays would determine whether the light emission of elementary particles obeys the laws of classical wave theory or those of quantum theory.
A fine letter on gyroscopes, refrigerators and quantum theory. Einstein describes his work on a gyroscopic compass, for which electrolyte fluid ('Elektrolyflüssigkeit') has proved insufficiently stable, so that they have had to fall back on using water; but 'the electrical set-up which I suggested has proved very satisfactory'. His work on a refrigerator is making progress too: they are attempting to obtain a commission from a local firm; the situation with the patent is however still murky. He ends by describing an experiment with cathode rays falling on a mica surface, and causing the surface to glow: the light is emitted in part directly, and in part after reflection from the inner surface. 'The question is whether the two beams interfere. The experiment is simple, as long as the surface doesn't become too hot'.
A startling example of the range of Einstein's interests at any moment. He was working on the gyroscope in collaboration with a navigational instruments firm, Anschutz, based in Kiel: the device was perfected by 1927, and proved markedly superior to older models, being employed in a number of navies, including the German, Italian, French and Japanese. The design for a noiseless refrigerator, on which he worked together with Leo Szilard, was a project that was still preoccupying him in 1928. The experiment with light rays would determine whether the light emission of elementary particles obeys the laws of classical wave theory or those of quantum theory.
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