Beschreibung:

EINSTEIN, ALBERT. Autograph letter signed ("Papa") to Hans Albert Einstein, n.p., 17 May [1935]. 2 pages, 4to, 277 x 206 mm. (11 x 8½ in.), written on rectos only of two sheets, two tiny holes at fold intersections , otherwise fine. STATISTICAL PATH DISTRIBUTION A lengthy letter in which Einstein suggests an equation by which the probable paths of gravel in moving water might be calculated. He thanks his son for pictures of his grandsons: "I like the little pictures a lot, especially the one of the younger boy [Klaus, Hans Albert's son], who has such a clever and determined look. Your thoughts on the statistical distribution of paths could be of practical use, but are not completely clear to me. I would like to share my thoughts with you..." Einstein proceeds to set out, in careful detail, the terms and symbols for formulating an equation for the path taken by particles in a whirlpool. He provides an equation, in which "W" stands for the probablility and "z" for units of time, then further analyzes the nature of the results which will be obtained. Finally, he concludes, "From such observations of varying speeds of water and gravel, one can draw useful conclusions about the structures of whirlpools. I can understand why you chose this subject...I am very pleased about your enthusiasm for your work." Hans Albert's doctoral dissertation, which he successfully defended in March 1936, was entitled "Der Geschiebetrieb als Wahrscheinlichkeitsproblem" (The Application of Probability Theory to Sediment Transport).