EINSTEIN, ALBERT. Autograph letter signed ("Papa") to Eduard Einstein ("Lieber Tetel"), n.p., n.d. [Peconic, Long Island, New York, late 1930s]. 2 pages, 8vo, 200 x 127 mm. (8 x 5 in.), slight darkening to extreme upper margin, minor chip to upper margin.
DEFINING THE OBJECTIVE AND SUBJECTIVE CONCEPTS OF TIME
Einstein has read Eduard's "exposition about time," and observes that "the concept of psychological time structures the world of our memories. The emotions, to be sure, play no special role in this world of psychological content (with respect to the temporal), nor in the construction of a subjective concept of the future. Psychological time is a kind of one-dimensional ordering of the contents of our consciousness as they are present in memory (or expectation)."
"The problem with which I have concerned myself is that of objective time; that is, the time of events, not of the contents of consciousness. It presupposes the subjective concept of time and is a problem not of psychology, but of physics. My understanding can be characterized thus: that the physical concept of time acquires a specific meaning only in association with other concepts (and laws) of physics. Its justification, like that of all matters pertaining to physics, requires proof with respect to the empirical."
Einstein is pleased that Eduard enjoyed his visit to Einstein's sister in Florence. In a postscript, he explains, "In the summer, I live here on the sea-coast, 170 kilometers east of New York [at Peconic, Long Island], in a little place which is from time to time quite deserted, until the summer visitors come."