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Known Space is the fictional setting of about a dozen science fiction novels and several collections of short stories written by Larry Niven. It has also become a shared universe in the spin-off Man-Kzin Wars anthologies. ISFDB catalogs all works set in the fictional universe that includes Known Space under the series name Tales of Known Space, which was the title of a 1975 collection of Niven's short stories. The first-published work in the series, which was Niven's first published piece was "The Coldest Place", in the December 1964 issue of If magazine, edited by Frederik Pohl. This was the first-published work in the 1975 collection.
The stories span approximately one thousand years of future history, from the first human explorations of the Solar System to the colonization of dozens of nearby systems. Late in the series, Known Space is an irregularly shaped "bubble" about 60 light-years across.
Within the Tales of Known Space, the epithet "Known Space" refers to a relatively small region in the Milky Way galaxy, one centered on Earth. In the future that the series depicts, spanning roughly the third millennium, humans have explored this region and colonized many of its worlds. Contact has been made with other species, such as the two-headed Pierson's Puppeteers and the aggressive felinoid Kzinti. Stories in the Known Space series include events and places outside of the region called "Known Space" such as the Ringworld, the Pierson's Puppeteers' Fleet of Worlds and the Pak homeworld.
The Tales were originally conceived as two separate series, the Belter stories set roughly from 2000 to 2350 CE and the Neutron Star / Ringworld stories set in 2651 CE and later. The earlier, Belter period features solar-system colonization and slower-than-light travel with fusion-powered and Bussard ramjet ships. The later, Neutron Star, period features faster-than-light ships using "hyperdrive". Niven implicitly joined the two settings as a single fictional universe in the short story "A Relic of the Empire" (If, December 1966), by using background elements of the Slaver civilization from the Belter series as a plot element in the faster-than-light setting. In the late 1980s—having written almost no Tales of Known Space in more than a decade—Niven opened the 300-year gap in the Known Space timeline as a shared universe, and the stories of the Man-Kzin Wars volumes fill in that history, bridging the two settings.

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