“How it happened that I in particular discovered the relativity theory, it seemed to lie in the following circumstance. The normal adult never bothers his head about space-time problems. Everything there is to be thought about it, in his opinion, has already been done in early childhood. I, on the contrary, developed so slowly that I only began to wonder about space and time when I was already grown up. In consequence I probed deeper into the problem than an ordinary child would have done.”
In Carl Seelig's Albert Einstein: A Documentary Biography (1956), Seelig reports that Einstein said this to James Franck, p. 71 http://books.google.com/books?id=VCbPAAAAMAAJ&q=%22how+it+happened%22#search_anchor.
I sometimes ask myself how did it come that I was the one to develop the theory of relativity. The reason, I think, is that a normal adult never stops to think about problems of space and time. But my intellectual development was retarded, as a result of which I began to wonder about space and time only when I had already grown up. Naturally, I could go deeper into the problem than a child with normal abilities.
Variant translation which appears in Einstein: The Life and Times by Ronald W. Clark (1971), p. 27 http://books.google.com/books?id=6IKVA0lY6MAC&lpg=PP1&pg=PA27#v=onepage&q&f=false
Attributed in posthumous publications
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Albert Einstein 702
German-born physicist and founder of the theory of relativi… 1879–1955Related quotes

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