Science is like sex: sometimes something useful comes out, but that is not the reason we are doing it.

Richard Feynman (1918-1988) American physicist

(Attributed)

Many variations can be found for this quotation (none of them with citation); the word "Science" and "Physics" are often interchanged:

• "Science is like sex, it has its practical purposes, but that's not why we do it."
• "Science is like sex. Sometimes something useful comes out, but that is not why we are doing it."
• Physics is like sex. Sure, it may give some practical results, but that's not why we do it."

As noted here, Frank Oppenheimer (a colleague of Feynman's) was quoted saying, "There's a lot of practical fruits to understanding, but it's like sex. There are practical fruits to sex, but nobody would say that's why you do it, normally." Feynman and Oppenheimer may well have collaborated on the general phrasing, or taken it from one another.