EINSTEIN, ALBERT.

1 page (9 7/8 x 8 in.) signed "A. Einstein" in English, on personal stationary blind-stamped with Einstein's home address on Mercer Street Princeton, NJ; creases where previously folded, some toning to edges.

Bloomsbury, 2015, lot 143

EINSTEIN SUCCINCTLY DESCRIBES DETAILS OF THE THEORY OF RELATIVITY. Penned just three years before his death in 1955, Einstein writes in response to a curious young woman, who likely read comments that she found contradictory to Einstein's theory, as Einstein notes that  "In Mr. Jacks' book... the concept mass is used in a rather misleading way." The letter reads in full:

"Dear Miss Crouse:

Your questions are not at all silly. An object of not vanishing mass can approach but never reach the light velocity; the reason is that its kinetic energy must always be finite. In the remark of Mr. Jacks' book — as in many other publications — the concept mass is used in a rather misleading way. Mass should be used as a constant of the body in question and not as something depending from speed. The faulty application of the word stems from an illogical transference of Newton's law of motion to special relativity."