Playground
Niven has described his fiction as "playground equipment", encouraging fans to speculate and extrapolate on the events described. Debates have been made, for example, on who built the Ringworld (Pak Protectors and the Outsiders being the traditional favorites, but see Ringworld's Children for a possibly definitive answer), and what happened to the Tnuctipun. However, Niven also states that this is not an invitation to violate his copyrights, so fans should try to avoid publishing works that are too obviously based in the Known Space universe without Niven's given permission.
Niven was also reported to have said that "Known Space should be seen as a possible future history told by people that may or may not have all their facts right."
The author also published an "outline" for a story which would "destroy" the Known Space Series (or more precisely, reveal much of the Known Space background to be an in-universe hoax), in an article entitled "Down in Flames". Although the article is written as though Niven intended to write the story, he later wrote that the article was only an elaborate joke, and he never intended to write such a novel. The article itself notes that the outline was made obsolete by the publication of Ringworld. "Down in Flames" was a result of a conversation between Norman Spinrad and Niven in 1968, but at the time of its first publication in 1977 some of the concepts were invalidated by Niven's writings between '68 and '77. (A further edited version of the outline was published in N-Space in 1990.)
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