
Source: Aphorisms and Reflections (1901), p. 148
The Architecture of Theories (1891)
Source: Aphorisms and Reflections (1901), p. 148
Source: Leisure, the Basis of Culture (1948), Leisure, the Basis of Culture, p. 50
“Physics is like sex: sure, it may give some practical results, but that's not why we do it.”
Does not appear to be from any of his books or cited in a biography. A Google Books search shows that the oldest book citing "physics is like sex" is Scary Monsters and Bright Ideas (2000) by science broadcaster Robyn Williams. On p. 44, this book claims: "Einstein said, 'You do not really understand something unless you can explain it to your grandmother'. Richard Feynman added, 'Physics is like sex: sure, it may give some practical results, but that's not why we do it'." Given that Einstein didn't really say the former, it's likely that Feynman didn't really say the latter.
Disputed and/or attributed
Variant: Physics is like sex: sure, it may give some practical results, but that's not why we do it.