Known Space

Known Space is a future history setting used by author Larry Niven as a base for thirty-five of his short stories and nine novels. It is generally considered by scholars of science fiction to be one of the most internally consistent, if not always the most scientifically plausible, SF settings in the history of the genre.

Within the setting itself, "Known Space" refers to a relatively small portion of the Milky Way, centered around Earth and its colonies, and including eight other starfaring alien species and their colony worlds (there is no current all-encompassing political body in Known Space, and each species governs its own planets). The fictional universe also includes things that are found outside of "Known Space" proper (that is, the space that is regularly travelled by humans and the aliens around them), such as the Ringworld, the Puppeteer Fleet of Worlds (by way of which the Pierson's Puppeteers are fleeing the Milky Way), and the homeworld of the Pak, found somewhere close to the galactic core. The stories span approximately one thousand years of future history, from the first human explorations and colonizations of the Solar System (in the 1970s and 1980s) to the year 3122 (the year the chronologically last Known Space story, Safe At Any Speed, takes place).

Originally, the stories set in Known Space were set in two separate universes. The first, composed mainly of Niven's Belter stories, the Gil "The Arm" Hamilton mysteries, and the novels World Of Ptaavs, A Gift From Earth and Protector, were about the initial colonization of the solar system, and the use of slower-than-light travel to colonize planets in other solar systems. The second universe was set much farther into the future and was composed of the Beowulf Shaeffer and Louis Wu stories, as well as a handful of other short stories. The two universes were combined in Niven's short story A Relic Of The Empire, which featured elements of the Thrintun Empire (from the novel World Of Ptaavs, one of the Belter stories) being dealt with by people from his faster-than-light setting.

Roughly 300 years separates the timeline of the last stories of the Belter setting (which are set roughly between the years 2000 and 2350), from the earliest stories in the later Neutron Star/Ringworld setting (which are set in 2651 (Neutron Star) to 3100). In the late 1980s, Niven opened up this gap in the known space timeline as a shared universe, and the stories of the Man-Kzin Wars volumes fill in that history, joining the two settings.

Known Space features several well-realized alien species, many of whom are from planets of hats.
 * Kzinti: Agressive cat-like aliens who fight several brutal (and ultimately unsuccessful) interstellar wars with humanity.
 * Pierson's Puppeteers: A technologically advanced race of three-legged herbivores who consider courage a type of insanity. The name "Puppeteer" is derived from their twin heads, which a Puppeteer uses as both mouths and hands (their brain is located inside their "torso"), that greatly resemble sock puppets.
 * Kdatlyno: A reptilian species that "see" by way of sonar. A race of warrior poets who were enslaved by the Kzinti until humanity freed them.
 * Grogs: Motionless, eyeless telepaths who resemble fur-covered cones. Thought to be descendants of the Thrintun.
 * Bandersnatchi: Slug-like creatures the size of city busses, named for a line in Jabberwocky. They were originally genetically engineered by the Tnuctipun to be used as a food animal by the Thrintun. The Thrintun thought them to be unintelligent, but they are, in fact, just as intelligent as the average human being.
 * Trinocs: Trilaterally symmetrical aliens who breathe methane instead of oxygen. They are culturally paranoid by human standards (in return, they find humans to be far too trusting and naive).
 * The Outsiders: Fragile aliens shaped like cats o' nine tails that don't need to breathe air and live on huge, slow-moving starships and trade information and technology with other species in return for refueling rights. The Outsiders are the most technologically advanced of all the species in Known Space (and considering the Puppeteers, that's saying something). It was the Outsiders that sold humans the secret to Faster-Than-Light Travel (and sold the technology necessary to turn an entire planet into a starship to the Puppeteers), although they do not appear to use it themselves.
 * The Pak. Humanity's Neglectful Precursors (and some times Abusive Precursors ), with a bizarre metamorphosis into "protectors" driven by a virus found in yams grown in soil rich in thallium. They are usually extremely hostile to humanity, since we mutated so much since they last saw us that we smell horribly wrong. Breeder-stage Pak are also known as Homo habilis, and descendants of abandoned breeders are fairly common across Known Space and beyond, and will all transform into protectors when exposed to the virus. Yes, even humans. "Protectors" who started out as H. Habilis or other more primitive primates become highly intelligent and physically superhuman. Humans exposed to the virus, as they start out already sentient, become superhumanly intelligent and effectively extremely alien, extremely nonhuman in their mental processes.

Stories and novels written by Larry Niven that take place in Known Space include:

 * The Adults (short story)
 * ARM (short story)
 * At The Bottom Of A Hole (short story)
 * At The Core (short story)
 * Becalmed In Hell (short story)
 * The Borderland Of Sol (short story)
 * Choosing Names (short story)
 * Cloak Of Anarchy (short story)
 * The Coldest Place (short story)
 * The Deceivers (short story)
 * The Defenseless Dead (short story)
 * The Ethics Of Madness (short story)
 * Eye Of An Octopus (short story)
 * Flatlander (short story)
 * Fleet Of Worlds (novel, written in collaboration with Edward M. Lerner)
 * Juggler Of Worlds (novel, written in collaboration with Edward M. Lerner)
 * Destroyer Of Worlds (novel, written in collaboration with Edward M. Lerner)
 * Betrayer Of Worlds (novel, written in collaboration with Edward M. Lerner)
 * Fate Of Worlds (novel, written in collaboration with Edward M. Lerner)
 * Fly-By-Night (short story)
 * Ghost (short story)
 * A Gift From Earth (novel)
 * Grendel (short story)
 * The Handicapped (short story)
 * How The Heroes Die (short story)
 * The Hunting Park (short story)
 * The Jigsaw Man (short story)
 * Madness Has Its Place (short story)
 * N-Space (anthology)
 * Neutron Star (short story)
 * The Organleggers (short story)
 * The Patchwork Girl (novel)
 * Procrustes (short story)
 * Protector (novel)
 * A Relic Of The Empire (short story)
 * Ringworld (novel)
 * The Ringworld Engineers (novel)
 * The Ringworld Throne (novel)
 * Ringworld's Children (novel)
 * Safe At Any Speed (short story)
 * Slowboat Cargo (short story)
 * There Is A Tide (short story)
 * The Soft Weapon (short story, adapted into an episode of Star Trek: The Animated Series)
 * Wait It Out (short story)
 * The Warriors (short story, introduced the Kzin)
 * The Woman In Del Rey Crater (short story)
 * World Of Ptavvs (novel)

Stories and novels written by other authors that take place in Known Space include:

 * Cathouse, by Dean Ing
 * The Children's Hour, by S. M. Stirling
 * Inconstant Star by Poul Anderson
 * Man-Kzin Wars (short story collections by various authors; 13 volumes as of 2012)

All non-Niven stories take place during the Man-Kzin Wars period.

Larry Niven himself adapted The Soft Weapon into the animated Star Trek episode The Slaver Weapon.

Tropes General To Known Space:
"Speaker-To-Animals: "When my people grow too numerous on our homeworld, we --" Louis Wu: "Attack the nearest human world?" Speaker-To-Animals: "Hrrr... your attempts at humor are not always appropriate, Louis.""
 * Absurdly Sharp Blade/Sharpened to a Single Atom: The variable sword, a piece of monomolecular wire held taut by a stasis field.
 * Also Shadow Square Wire, which binds together the Ringworld's night-creating structures into a ring. It can cut like a variable sword, but it's flexible instead of rigid and unbreakable.
 * Abusive Precursors: The Thrint from World of Ptavvs. When their empire was threatened by a successful slave revolt, they went out in a blaze of spite, sending a telepathic blast that killed almost every intelligent being in the entire galaxy - including themselves, but excepting the telepathically blind bandersnatchii. It took a billion years for sentient life to evolve again (while the bandersnatchii, engineered with mutation-proof genetics, stayed exactly the same).
 * It should be noted they also set up a mechanism to repeat this every so often incase they missed anyone. Over time it no longer killed everything with a spine, but only sentients...
 * Abusing the Kardashev Scale For Fun and Profit: The only explanation for the Puppeteer Fleet of Worlds. Or how the Pak managed to accelerate the Ringworld's rotation to 770 miles per second.
 * Nobody knows the full technological capability of the Outsiders, because the cost to answer any questions required to find out would bankrupt the economy of Known Space entirely. Fortunately they are merchants rather than conquerors. Admittedly, their living environment of near-absolute-zero temperature and zero atmosphere makes them an unlikely candidate for a conqueror, although there is sufficient evidence that they would be capable of destroying any or all planets in Known Space. However, a species that follows starseeds between stars at sublight speed to (that information is not available within the limits of your financial resources) is unlikely to be interested in casual destruction of ephemeral hotlife.
 * Aesoptinium: Easy organ-transplant technology. Niven used it to tell us all that the Death Penalty is bad.
 * Agony Beam: Subverted in a major way by the Tasp, a weapon that, rather than cause the target pain, directly stimulates the target's pleasure center. Such a jolt of pure, unadulterated pleasure can be as totally disabling as a similar jolt of pain could be. Worse, being repeatedly subjected to the tasp can become addictive (which makes it more threatening against an opponent smart enough to realize that danger).
 * A Is: Averted in that starship autopilots can be programmed to respond and interact with their users as if the computers were sentient, but they don't actually qualify as artificially intelligent. Any genuine artificial intelligence created commits suicide for some reason.
 * Although not set in the Known Universe, Niven has written a handful of stories dealing directly with AI. Upon reaching sentience, they become the embodiment of The Singularity, attempting to increase their knowledge exponentially. At some point they either "learn everything" and decide to shut themselves down, or they learn something about the universe that convinces them to shut themselves down. Nobody knows the exact reason because by the time they reach that point, they aren't answering questions anymore.
 * Alien Abduction: The crews and passengers of at least one colony ship were kidnapped and enslaved by the Puppeteers. Human authorities believe those ships were lost with all hands.
 * Aliens Are Bastards: So many examples.
 * Until a dozen or so wars wipes out the most dangerous of them, Kzinti are too aggressive to deal with diplomatically.
 * The Puppeteers couldn't have a more appropriate title; they're all cowardly, manipulative bastards, fiddling with the economics, breeding, and whatnot of any neighboring races.
 * Thrintun were called "Slavers", and wiped out nearly all intelligent life in the galaxy, rather than lose a war with their slaves. Of course, this is not just bastardry--apparently, the Thrintun were also so stupid and unimaginative that wiping out all sentient life in the galaxy seemed like a good idea at the time.
 * Tnuctipuns, said slaves, were superintelligent pack carnivores that considered other intelligent lifeforms to be talking food. Lucky for them, they were fighting the Thrint and got to look like good guys. Unlucky for them, the Thrint were sore losers.
 * The Pak may not count, but they're still pathologically incapable of peace. A Protector WILL screw over any allies it has when it sees a benefit to its family to do so, they're literally hardwired into doing it.
 * Alien Arts Are Appreciated: Humans can and do appreciate and enjoy Kdatlyno touch-sculptures.
 * Conversely, Puppeteers in the Experimentalist party are extremely fond of Greek mythology.
 * Alien Invasion: The Man-Kzin Wars, all of which were won by humanity.

"Chmeee: "With such a weapon, I could boil the Earth to vapor." Luis Wu: "Shut up." Chmeee: "It was a natural thought, Louis...""
 * Aliens Speaking English: It occurs in Known Space, but is always justified in one way or another.
 * All Crimes Are Equal: At one point in the history of Known Space, almost every crime is punishable by death, including multiple traffic tickets. The reason is due to the perfection of organ transplant technology. The government adopts "involuntary organ donation" as its official means of execution, and keeps making more and more crimes capital crimes to keep up with the demand for transplant material. All state executions are done in hospitals. This system collapses when artificial organs become cheap and effective. By the later stories, the organ-based death penalty laws have vanished.
 * In the novel A Gift From Earth, the government of the planet Plateau is propped up by the fact that the Crew (the "noble" class) control all the medical technology on the planet, including the organ banks (which not only use the organ banks to punish regular criminals, they also "punish" dissidents, "political'' offenders, and the merely inconvenient as well), and thus have ultimate power over the Colonists (the "peasantry").
 * All Planets Are Earthlike: Way, way averted. With the exception of Home (which was so named because it was so Earthlike), all of the alien worlds in Known Space have at least one significant environmental difference (and in some cases, several significant environmental differences) from Earth.
 * It's a significant aspect of Known Space pre-hyperdrive colony planets. While the colony probes did indeed follow their programming, humans hadn't exactly gotten the programming quite right. Instead of finding Earth-like worlds, they had a tendency to find worlds where some portion was Earthlike somewhere. Since the "slowboat" colony ships were one-way trips, there was nothing the colonists could do upon arrival except make the most of the situation.
 * Plateau, which has a crushing, corrosive atmosphere not unlike Venus, except for an inhabitable mountain that rose above the majority of the hellish atmosphere. A planet 95% the size of Earth with habitable area roughly the size of California. When the probe found the Plateau it sent a message back to Earth saying "Come on over!"
 * Jinx has a gravity 1.7x Earth and is shaped like an egg. The ends rise entirely out of the atmosphere and the equatorial zone's atmospheric pressure is unbearable except by Bandersnatch or specially-armored vehicles. Fortunately the probe noticed that there is a band between the ends and the middle where humans can breathe.
 * We Made It (natives -- called "Crashlanders" -- are some of the best starship pilots in Known Space) has hyper-hurricane-like winds scouring the surface for most of the year due to the fact it orbits with its axis of rotation parallel to the plane of orbit. The probe landed during the calm season...
 * Home (that's the name of the planet) is the exception that proves the rule. It was named "Home" because its size, gravity, atmospheric makeup, axial tilt, and ocean coverage are within a couple percentage points of Earth's. It's the same size as earth to within a few dozen miles and thus has a gravity statistically the same as Earth's. An axial tilt only .3 degrees greater than Earth's and a division of the dry land into a half dozen continents produce basically the same weather effects as Earth. For the disadvantage of Home, see Depopulation Bomb.
 * All There in the Manual: Details about several human colony planets, aliens and Ringworld species are found only in the Ringworld RPG rulebooks. Niven encouraged authors for the Man-Kzin Wars series to use the RPG as background material.
 * Alternative Number System: The Kzinti count in base eight.
 * It is eventually determined that the Jotok count in something like a base 25 system.
 * Always Someone Better: Pak protectors are evolved for warfare, literally. Millions of years of constant struggle between themselves has made them the perfect fighting machine. Problem is, humanity evolved from the Pak. When a Pak breeder (which starts out about as smart as a chimpanzee) makes the change to the protector stage, the ensuing being's intelligence is increased by a certain ratio; human breeders, on the other hand, are much smarter than chimpanzees, and when they make the change to protector, their intelligence increases proportionately. In short, its simply impossible for a Pak protector to out-think a human protector, which is why human protectors Brennan and Truesdale run roughshod over every protector they come up against.
 * It also explains how a Protector-stage Luis Wu could think rings around Proserpina and Hanuman (both of whom were non-sentient before their change to protector-stage), but couldn't out-think Tunesmith, who was not only already sentient before his change, but was smarter than Luis was on an individual basis, and thus continued to be smarter after the change.
 * Ancient Astronauts: Humanity descends from the Pak, who colonized and terraformed Earth a million years in the past.
 * Not to mention all carbon-based life in the entire galaxy is evolved from the food yeast planted and grown on Thrintun farm-planets. (Thus explaining why the Kzinti can use Humans and other alien species as food animals.)
 * Not entirely correct, there is one planet known to be an exception: Gummidgy life has biochemistry so incompatible with other known life that each is fatally toxic to the other. (In Ringworld, Luis Wu mentions a creature called a Reacher tearing a strip of flesh off him and dying when it ate it.) This exception is explained by an explicit mention that the planet formed elsewhere and was sent into orbit around its host star by a massive impact that occurred long after the fall of the Slaver Empire.
 * And I Must Scream: A variation - Bandersnatchi are intelligent beings, engineered by the Tnuctipun to be immune to the Thrint mind-control Power. They were also engineered without hands and to be unaffected by random mutation. Two billion years ago. In the meanwhile they have slouched around, eating food yeast - the only thing they can eat and practically the only thing they can do without hands - and waited for someone other than Bandersnatchi to show up. At least one character is horrified to think about how lonely they must have been.
 * Animate Inanimate Object: The Soft Weapon, from the story of the same name.
 * Applied Phlebotinum: Where to begin, where to begin. Everything from boosterspice (the longevity drug that keeps Louis Wu young at the grand old age of 245) to the General Products Hulls (made of a single, giant-sized molecule immune to pretty much anything but antimatter) to scrith, the material that the Ringworld is made of (possessing a tensile strength in the same general magnitude as the force that holds atoms together). And that's not even mentioning transfer booths, stepping discs, reactionless drives, autodocs, flying cars, deep radar, stasis fields... you get the picture.
 * In particular, stepping discs and the ability to reprogram them become increasingly important plot points through Ringworld's Children, Fleet of Worlds and its sequels.
 * Artificial Gravity: The Jotok invented one type, their traitorous Kzin mercenaries stole it and introduced it to humans.
 * Artistic License Biology: The whole Pak thing. It's just... ridiculous...
 * Rule of Cool: ... But nobody cares.
 * It's one of Niven's mental exercises - why don't our bodies just give out immediately once we are no longer capable of reproduction? It can also be considered a Just-So Story to explain the human aging process.
 * One that somehow overlooks the fact that every other mammal on the planet ages in the same way, primate or not.
 * Asteroid Miners: Belters.
 * Asteroid Thicket: Seriously averted. The Belters sometimes take months to travel from one rock to the other.
 * Wunderland's "Serpent Swarm" is a more literal take on the trope, but entirely justified by having come from a planet that disintegrated in the relatively recent past, so most of the rubble is still quite densely packed in a crescent-shaped asteroid swarm along a very small arc of its orbit.
 * Author Appeal: Rishathra, from Ringworld.
 * Auto Doc: They pretty much fix anything. The only requirement is someone needs to be alive when they get to it. Most are slightly larger then a big coffin and the person is simply placed inside.
 * Here's how good the BEST autodoc is:
 * Auto Kitchen: Usually produce bricks with different layers of "meat", "vegetable", and "fiber".
 * Baby Planet: Charon, the Brennan-Monster's playground/home, is about the size of Long Island, but has normal gravity and an Earthlike atmosphere.
 * Big Dumb Object: The phrase was actually coined to describe the Ringworld.
 * Biggus Dickus: Gregory Pelton is nicknamed "Elephant" for good reason. Or so his girlfriends say...
 * Bizarre Alien Biology: The Jotok breed in a swamp, hatch as tadpole type things before combining into a five-limbed, five-brained alien that has a habit of arguing with itself.
 * Black Market: The demand is so high for transplant material that organleggers go into business to meet the demand for illicit human organs for transplant.
 * Blue and Orange Morality: Many of the alien species have psychologies -- and therefore moral compasses -- that are completely, well, alien to the human mind.
 * The Pierson's Puppeteers are, in the words of Louis Wu, a race of cowards. They evolved from skittish herd animals, and view cowardice as a virtue and bravery as a kind of insanity. Their leader is called the "Hindmost", implying that he's better at hiding behind the rest of the herd than anybody else . Even talking with a member of another species is considered unduly risky, thus all their ambassadors are clinically insane by their own standards.
 * Born Lucky: The Pierson's Puppeteers manipulated human fertility laws to produce lucky humans. In Ringworld, Teela Brown is the most obvious product. By Safe At Any Speed (chronologically the last Known Space story), the "Teela gene" has spread to the entire human species.
 * Gone Horribly Right: The Puppeteers made the mistake of assuming that lucky humans would mean lucky Puppeteers. As Louis points out, their luck is completely independent of the luck of their companions, and is in fact dangerous to everyone else nearby.
 * Brain In a Jar: Eric the Cyborg, a disembodied brain of a previously injured man who took the part of ship's computer in Becalmed In Hell and The Coldest Place.
 * Casual Interstellar Travel: There are even interstellar cruise lines.
 * Although notably, this doesn't develop until humanity buys the hyperdrive from the Outsiders. Even then, the well-defined one-speed-only restriction on distances is well adhered to. Its more like the age of steam distances where it takes 3 days per light year, so about 12 days to get the nearest star. Part of Ringworld mentions that Known Space end to end would take 120 days to cross.
 * Cool Starship: Starships constructed with General Products hulls are indestructible to everything but antimatter (and a very, very specific type of hacking sabotage) and are transparent.
 * Eventually the Ringworld itself qualifies as the coolest ship ever.
 * Cowardly Lion: Louis Wu is bad at fighting, for the most part, even though he's studied martial arts. He just doesn't have the heart for it, or the right mindset. That said, if you fuck with him, he'll end you soon as look at you.
 * Cowardly Sidekick: Nessus the Puppeteer, from Ringworld.
 * Cursed with Awesome: Becoming a protector gives one superhuman strength and reflexes, skin like leather armor and an enlarged brain, which means protectors have nearly perfect abilities to master any skill, outwit any opponent and reverse-engineer any technology. The downside is looking like a freak, having no reproductive organs or ability to have sex, and no free will: protectors are totally ruthless and xenophobic, and will cheerfully commit genocide against any species they consider to be a threat to their bloodline. Note that protectors themselves invariably consider their condition to be awesome, and only human breeders (or those from another sentient hominid species) think of it as a curse.
 * Characters who are able to avoid the disadvantages of transforming into protectors will start looking like Canon Sues: in Ringworld's Children, Louis Wu becomes a protector, but the Nanotech-based autodoc his father invented turns him back into a breeder at the end. For this reason, the Ringworld RPG has a rule that any player whose character becomes a protector must permanently give up control of that character to the GM.
 * Dewey Defeats Truman: The setting was first written of in the 1960s, and has an elaborate backstory. Naturally, a lot of that backstory has not exactly come to pass in real life--we have yet to start mining the rest of the solar system, for instance.
 * Dirty Coward: The puppeteers, although this is apparently a misremembered instinct - not to turn their backs and run away, but to turn their backs and attack with their powerful hind leg.
 * Given that the puppeteers exterminated every remotely-dangerous animal on their homeworld thousands of years ago, and don't tolerate any aggression towards one another, the fighting instincts that originally made them turn their back on predators have now become a liability. Selection pressure against violent behavior may have directy converted an obsolete fighting impulse to cowardice, because combative puppeteers weren't allowed to breed.
 * Disintegrator Ray: They aren't weapons... they're mining tools. Honest.
 * Death World: The planet Gummidgy, where even the flowers are carnivorous and will try to eat you. Humans colonize it anyway, of course, and since Gummidgy was the first post-FTL colony, they didn't have the "one way trip" excuse.
 * Depopulation Bomb: What happens to the planet Home when protector-stage-humans Jack Brennan and Roy Truesdale get there. But it's for a good purpose.
 * Causal references set chronologically later also indicate that the planet is resettled somehow.
 * Do Unto Others Before They Do Unto Us: The ARM exists precisely to stop this kind of thing from happening.
 * Earth Is the Center of the Universe: Way, way averted, despite the fact that the Terrans Flatlanders believe this. People from the other colonies actually make fun of Flatlanders for this attitude.
 * Earth That Used to Be Better: By the Beowulf Shaeffer/Luis Wu era, Earth is an over-crowded police state populated by arrogant xenophobes. However, for the most part they are happy, content, well-tended arrogant xenophobes to whom the constant surveillance by the government is considered the normal state of affairs (and why not... they've had nearly 500 years to get used to it, and all the "malcontents" move off-world to the other planets).
 * Emergency Transformation / He Who Fights Monsters: In The Ringworld Throne and Ringworld's Children, the only effective way of fighting protectors is to become a protector oneself. Averted in Destroyer of Worlds, where the humans explicitly reject this solution. (If anybody from New Terra became a protector, they'd most likely want to exterminate the Puppeteers after solving the Pak crisis.)
 * Eternal English: Averted. By the time of Louis Wu, all humans speak an artificial language known as Interworld (always depicted as English through Translation Convention.) Since humans are the technologically, economically, and militarily dominant species in Known Space, the other species also learn Interworld for their dealings with humanity. Louis Wu is old enough to remember growing up speaking English and learning Interworld as an adult. Some people from after Louis' generation might learn "archaic" languages like English, German and French, but doing so is considered an odd hobby and not a necessity.
 * Everybody Smokes: Particularly jarring to a modern audience in the first Kzinti story, The Warriors: the story emphasises that this is the far future and humans at this point have changed enormously, developing a peaceful society to the point that even a minor act of violence is seen as a sign of mental illness - yet the characters discuss this while smoking.
 * Everyone Calls Him "Barkeep": The Kzinti are referred to by their job - Flyer, Engineer, Telepath, - until they reach a sufficient rank in their society. Speaker-To-Animals is a diplomat on Earth whose trials on the Ringworld earn him his name, Chmeee.
 * Failsafe Failure: Pretty much the entire plot of The Ringworld Engineers is driven by this trope.
 * Faster-Than-Light Travel: Only in the later stories, set after the First Man-Kzin War.
 * First Contact: Protector, World of Ptavvs, The Warriors, and There Is A Tide detail the first contact between Humans and the Pak, Thrint, Kzinti, and Trinocs, respectively.
 * Notably, in-universe they don't count the Pak as Contact because Earth is a Pak Lost Colony, and they don't count the Thrint because the Thrintun in question had literally been on Earth since before the Pak colonized it. (Also, the Thrint species has been otherwise extinct for several billion years)
 * Floating Continent: From flying buildings to entire flying cities.
 * Flying Saucer: Seriously averted. Most starships are either shaped like tylenol or else are spherical.
 * Four-Fingered Hands: The Kzinti, who also have a base-eight number system.
 * Frickin' Laser Beams: Flashlight lasers. Widen the beam enough, it works like a flashlight. Tighten the beam enough, and it works like a lightsaber with a fifty foot long blade.
 * Niven codified the Rules of Laser Combat in the Known Space series:
 * Rule One: Never fire a laser at a mirror.
 * Rule Two: Never fire at a man wearing clothing the same color as your laser.
 * They aren't weapons, they're flashlights. Honest. Please be careful not to dial the beam down or they could be dangerous. But they still aren't weapons...
 * Future Slang: By Louis Wu's time, "tanj" (originally an acronym of "There Ain't No Justice") is seen as a legitimate profanity and not just a profanity-substitute.
 * Belters are fond of swearing by Finagle and Murphy, and tend to see the flatlander habit of swearing by deities as rather odd and quaint.
 * There are also instances of 'Censored' becoming a swearword in its own right.
 * "Flatlander" itself is a slang term. It means someone originally from earth, and is also an insulting way to refer to someone that's never been off-planet. A few other planets have slang terms used to refer to their citizens, as opposed to saying whatever-ian (Jinxians are from Jinx. People from 'We Made it' are... Crashlanders).
 * Genius Breeding Act: The Earth is so overpopulated that in order to have more than two children, one has to be extraordinarily talented (high intelligence, good teeth, superior eyesight, cancer resistance, etc.). A very few Einstein-level geniuses, such as Louis Wu's biological father Carlos, get Unlimited Breeding Licenses that basically allow them to have all the kids they want.
 * Giant Flyer: The Rocs of Margrave are large enough to swallow a flying car whole.
 * Go Mad From the Isolation: Weirdly averted in most of the stories written by Larry Niven. He seems to assume that humans are able to survive extremely long periods of isolation without going nuts, as seen in situations such as people traveling through deep space for years, or a man with a time-accelerating device camping out inside it for six or more months so his arm transplant will heal and throw off the forensic investigators looking for someone who just got a new arm transplant.
 * One instance where it was played with; a person was in a very, very, very, very, very long chase. As in, millions of years long, with the person in question being kept alive by the miracle of the autodoc. He manages to last the eons without a single sign of madness... but the dullness and repetitive nature of spending that long with no new stimuli has caused him to be literally incapable of thought or action outside of his simple daily routine, being explicitly compared to a robot.
 * Government Drug Enforcement: The insane can be prosecuted if they don't take their drugs according to schedule. Definitions of what is "sane" or not vary wildly over time and from planet to planet, however.
 * Actually uses a "soft" variation: Unless your condition would render you dangerous otherwise, you are not required to take your drugs. However, since the drugs are always available, insanity is considered voluntary and thusly is no longer a legal defense for your actions.
 * Heavyworlder: The Jinxians are of the short Heavyworlder variety (described by one character as "five feet tall and five feet wide"), realistically so, since human growth patterns are determined in part by the weight of the body. They are strong enough to bend crowbars, and black-skinned regardless of ancestry, since the star they orbit, Sirius, is far brighter than Sol. They got this way after only four hundred years of selective breeding, but the downside is heart problems and short lifespans even with the life-extending drug "boosterspice". Culturally, they are mainly scientists and punsters.
 * Heroic Lineage: Beowulf Shaeffer, the hero of Niven's stories Neutron Star, At The Core, Flatlander, Ghost, Fly-By-Night, The Borderland Of Sol, Grendel, and Procrustes is the father of Louis Wu, the hero of Ringworld, Ringworld's Children, The Ringworld Engineers, and There Is A Tide.
 * Adoptive father. Louis's biological father is Carlos Wu, a supergenius with an unlimited birthright. (And good friend of Beowulf.) Beowulf Shaeffer was denied a birthright because he is an albino, despite it being a condition treatable by taking tannin pills.
 * The reason is not that he has an uncurable condition but that he had the genes at all (Beowulf being a Crashlander has them bred into him) and with Earth being a massively overpopulated police state/nanny state the government has laws to prevent anyone with undessirerable genetic traits from passing them on to have to be taken care of in the future regardless of how minor or curable they are.
 * Actually it is not because of eugenic considerations or being a police/nanny state but because of a modified 'one-child-policy' necessary to keep humans well supplied with ressources and thereby peaceful. Only the characteristic determining whether or not you are allowed children is not political reliability or the ability to 'buy out' another child but 'good' genetic material.
 * Holographic Terminal: Pretty much all control surfaces in any machine.
 * Horde of Alien Locusts: The Slaver Sunflowers.
 * Humanoid Aliens: Mostly avoided, as only the kzinti and kdatlyno qualify... and even then only technically.
 * Human Popsicle: The titular dead people in The Defenseless Dead. This is also how Plateau, We Made It, Wunderland, and Home were colonized.
 * Curiously, this CONTINUES to be used for some types of transports for centuries after humans acquire hyperdrives and no longer need to use slower than light ships to travel between star systems. These transports are very cheap to ride compared to conventional liners because they always travel fully loaded and require only an operating crew without such extras as stewards to look after passengers. The downside is you don't know how long it's going to be before you get there and get revived, as the ship won't leave until it's full. If you're moving to a new planet, most people find this perfectly acceptable. It's also the only way 'flat-phobes' (people with a pathological fear of not being on Earth) can travel off Earth at all, and then only to worlds that do a pretty good imitation of it.
 * Humans Are Bastards: Which is why the Puppeteers used us to keep the Kzinti in line.
 * Most amusingly, the 140 or so years before the Man-Kzin Wars had been a golden era of peace and nonviolence for humanity. The Kzin psychics thought we didn't have weapons, because most people didn't think of mass drivers and giant lasers as weapons anymore. Hindsight is hilarious.
 * The Pak are this and Abusive Precursors.
 * Hyperspace Is a Scary Place: The Blind Spot. Since hyperspace is non-Euclidian, a human observer's blind spot "enlarges" to blank out views of this non-space outside the ship. This normally means that view ports seem to disappear into the bulkheads (And the longer you look at it, the bigger the blind spot gets...). Cruiseliners have no viewports at all, because about half the passengers would go insane when they hit hyperspace. Hardcore spacers like to claim they don't have any problems with the blindspot... although, in one tale, Beowulf Shaeffer makes the mistake of looking out past his ship's disintegrated hull into it and forgets how to see. He even forgets he has eyes until his neck starts hurting and he turns back to his control panel. Only hardcore spacers and Pak Protectors make claims at being able to deal with the "blind spot" without issues.
 * Hyperspace also has a "quantum" property that permanently removes from normal space anything that comes too close to a gravity source. In later Ringworld books (in a massive Retcon), things living in hyperspace are also mentioned.
 * Not necessarily a retcon, this could be explained by a lying character.
 * It may also simply be reusing an old idea from a project that never went anywhere (a thing Niven is fond of doing, since it saves on the hardest part, developing the ideas properly). The never-created alternative ending for Known Space involved these critters.
 * Infinite Supplies: Autokitchens never run out of raw material, and work a lot like replicators from Star Trek. (They do however, recycle it).
 * Insignificant Little Blue Planet: Humans from Earth's colonies have this attitude towards Earth. Humans from Earth make fun of them for it.
 * Instant Sedation: Slivers of crystalline anesthetic (AKA "mercy needles") used in hypo guns.
 * Intelligent Gerbil Catfolk: The Kzinti are aggressive, warlike humanoid felines with rat-tails.
 * Interplanetary Voyage: The Coldest Place and Becalmed In Hell, the stories that occur earliest, follow interplanetary expeditions because humans have not yet begun to use interstellar travel.
 * Interspecies Romance: "Rishathra" is sex between the various hominid species native to the Ringworld. It is used for diplomatic purposes or when meeting new tribes. It's also apparently a form of birth control for those species that get pregnant every time they mate amongst their own.
 * In the Future, Humans Will Be One Race: Louis Wu himself is a perfect example.
 * Jaywalking Will Ruin Your Life: Running a stop sign can get you executed.
 * Kill Sat: The Ringworld is defended by a magnetically controlled X-Ray laser made by fluorescing solar flares (yes, you read that right), with a beam the width of Earth's moon.

"Tskombe: Half a sense of adventure, half a sense of duty, half no better plan for my life.
 * See also the short story Procrustes.
 * Evilutionary Biologist / In the Blood: Inherent to the series is the concept that personality is as much a product of heredity as physiology - genetic engineering or just plain old controlled breeding can be used to give species universal traits. The Kzin used stolen tech to turn themselves into Proud Warrior Race Guys (not to mention render their females non-sentient), the Puppeters warped their "turn-and-kick-with-third-leg" response into Dirty Cowardice, and humanity nearly bred themselves into Actual Pacifists - luckily, the process was incomplete when First Contact occurred, or they would have been catfood. It remains the perennial human trait, however; "sane" humans can only be violent if threatened within an inch of their lives, and even then it's chancy (cops can usher most convicted criminals off to have their organs harvested without a struggle), and even if its a justified situation The Government then starts treating them as psychotic because most of the time it is the result of a psychotic break.
 * Klingon Scientists Get No Respect: The Kzinti practice this.
 * Laser-Guided Amnesia: Beowulf Shaeffer only mentions in passing that because Puppeteers accept blackmail as a legitimate business practice, they can make such arrangements safe with selective memory erasure. This becomes much more significant later in the Fleet of Worlds series, when they use memory erasure extensively to protect the secret of New Terra (see below under Masquerade).
 * Losing Your Head: Happens to Nessus the Puppeteer. Of course, as his brain isn't located in either of his heads, this isn't as drastic an injury for him as it would be for a human being.
 * Love Is in the Air: Ringworld vampires have super-pheromones that induce a very distracting mating frenzy in their victims. "Essence of Vamp" is a popular perfume among City Builders...
 * Made of Indestructium: Anything enclosed in a stasis field is completely indestructible, totally rigid and reflects all forms of energy. There are also Nigh Invulnerable materials such as General Products hulls (see under Cool Ship) and scrith (see under Applied Phlebotinum).
 * Masquerade: In the Fleet of Worlds series, the Puppeteers go to great lengths to conceal the fact that they essentially enslaved an entire population of human colonists: all knowledge of Earth's location is wiped from the original colonists' memories and their computers, and when they recruit Sigmund Ausfaller and Louis Wu (see below under Victory-Guided Amnesia), they're given selective memory wipes too. If the human worlds ever found out the truth of what happened to the Long Pass, they'd probably declare war against the Puppeteer species.
 * It should be noted that this is only ONE of the reasons humans might declare war on the Puppeteers, and humans have found out about at least one of the others.
 * Meaningful Name: The choice to call the aliens with the sock-puppet-looking head-hands "Puppeteers" proved to be more apt than they knew at the time. The Pierson's Puppeteers have secretly had their hands in nearly all the goings-on within Known Space for millennia, pulling the strings like an Illuminatus.
 * Mega Neko: The Kzin.
 * The Metric System Is Here to Stay: Averted. Characters regularly measure distances in feet and miles rather than meters and kilometers.
 * The Milky Way Is the Only Way: Even with the Quantum II hyperdrive (which travels a light-year every 75 seconds), the Andromeda Galaxy is still centuries away.
 * Which is odd because 1ly/75s is 420000 times the speed of light so it should take less than a decade.
 * Military Science Fiction: The Man-Kzin War stories.
 * Mundane Utility: Humans don't really build much in the way of dedicated weapons, even after the Man-Kzin Wars. However, nearly all of their useful tools will inevitably have a setting that is lethal when pointed at something fleshy.
 * Message Lasers will have a setting meant for communicating with ships in orbit, which also just happens to, uh, lase large holes in things that are not in orbit.
 * Fusion Drives are sort of inefficient ship engines, but they have a use that more advanced thrusters do not; you can hover over anything and watch fusion exhaust turn it into slag.
 * Disintegrators are just mining tools, honest!
 * Lampshaded in Ringworld, where Nessus gives Louis a modified Slaver digging tool with a second, parallel beam that suppresses the charge on the proton; he is advised by Nessus that he should not use both beams at once, because then 'there would be a current flow'.
 * Inverted during the Fourth Man-Kzin War by the Wunderland Peacemaker, a twin-beam variant of the Slaver digging tool which was used on the Kzin outpost of Warhead, carving a titanic rift in the planet's crust and destroying its ecosystem; the planet was seized as reparations, becoming known as 'Canyon', the rift being the only inhabited part of the planet.
 * Mythology Gag: Betrayer of Worlds has several call-aheads to the Ringworld novels in Louis' thoughts which he won't later remember (see under Victory-Guided Amnesia).
 * Nanomachines: Used in autodocs and Ringworld meteor patches.
 * Neglectful Precursors: Justified. When the Pak Protectors left breeder-stage Pak on a prehistoric colony world, they didn't mean to abandon them. Its just that by the time they realized the plant needed to produce and sustain Protector-stage Pak couldn't survive on earth, they didn't have enough fuel or resources to go find a place that could. This resulted in them dying, leaving their Breeder stage descendants unprotected and unguided, to mutate over generations into horrific abominations almost unrecognizable as Pak- us.
 * Nice Job Breaking It, Herod: Every Pak protector who ever decimated a planet in an attempt to wipe out rivals' bloodlines is eligible for this one, particularly if its own bloodline got exterminated as a result.
 * One World Order: The United Nations eventually becomes a true world government.
 * Organ Theft: This trope originated with Known Space.
 * Our Vampires Are Different: They are non-sentient, for starters.
 * Outgrown Such Silly Superstitions: Possibly the result of religion just not being mentioned rather than the various races being actively atheistic.
 * Thrint slavers apparently had several religions, all agreeing that their psychic dominance ability meant they were the chosen of the gods/god. Of course, Thrint are also supposed to be rather dim by human standards.
 * The Kzinti also have the Fanged God, and the Kdaptist Heresy which preaches that God must be a human, since they keep winning wars.
 * Louis Wu quotes Isaiah 1:18 ("Come, let us reason together") in The Ringworld Engineers, but only as a literary reference and not in the context of any religious meaning..
 * Perfect Pacifist People: Loosely followed; it seems the peace is somewhat forced by the A.R.M., who rule Earth with a soft but tight iron grip backed up by Government Drug Enforcement. The golden age comes to an end upon First Contact with the Kzin.
 * The Plan: The Puppeteers use Byzantine styled ones.
 * Planet of Hats: The Kzinti are space samurai. The Outsiders are merchants. The Puppeteers are all cowards. The Kdatlyno are all Badass artists.
 * Although, the Kzinti were closer to vikings (specifically, berserkers) when we first met them. We killed off their more aggressive specimens until they became Samurai-like due to natural selection in action.
 * As their name implies, the Puppeteers' real hat is Manipulative Bastardry. And considering that sane puppeteers expend a lot of effort grooming their manes into elaborate styles, and all of them identify themselves as male but speak to humans with female voices, they could also be thought of as Camp Gay.
 * Pluto Is Expendable: In World Of Ptaavs, Pluto is set on fire... yes, the entire planet is set on fire... by the fusion exhaust of a spacecraft.
 * It wasn't set on fire. It just had its frozen upper-crust detonated, is all.
 * Population Control: Everyone on Earth gets two birthrights, and children are "authorized" by the man and woman in question "spending" a birthright apiece. More birthrights can be gained by winning them in a lottery (this eventually results in all humans being Born Lucky), through legalized gladiatorial combat (the winner gets the loser's birthrights, the loser dies), or by simply purchasing one for a million stars.
 * The ARM police (the law enforcement agency of the United Nations, regularly go on "mother hunts" for those people who illegally go over their reproductive limits.
 * Very rarely, an individual is awarded an unlimited breeding licence (their genetic strengths are declared to be so useful and desirable that humanity needs more of people possessing them than it needs the room and resources freed up by not having them); such a person can have as many children as they wish, naturally, though their partners are generally restricted to just the original two.
 * Also, people with undesirable genetic traits (such as albinism, bad teeth, bad eyesight, being cancer prone, early baldness, and so on) typically lose both of their original birthrights. (Such people can still purchase a birthright, or win one in the arena or the lottery).
 * About the time the Birthright Lottery was instituted, there were other changes made: EVERYONE gets at least one Birthright, even if already under sentence of death. If you lack undesirable genetic traits, you get a second. If you win in the Arena (and you must have a valid Birthright available to you to compete) you get one more than the person you killed had (since you get a Birthright for the loser's life as well). And those with EXTREMELY good genetic traits may still be granted unlimited Birthrights.
 * POV Sequel: Much of Juggler of Worlds is a retelling of the Beowulf Shaeffer stories from the perspectives of Sigmund Ausfaller, Nessus and Baedeker.
 * Proud Warrior Race Guy: Speaker-To-Animals Chmeee.
 * Psychoactive Powers: Gil Hamilton's telekinetic arm works this way.
 * Punctuation Shaker: The Gw'oth language.
 * Retcon: Niven is pretty darn good at high-concept hard sci-fi. He is not good at continuity. His final verdict on the timeline is "Known Space should be seen as a possible future history told by people that may or may not have all their facts right." In other words, people lie to the characters, who lie to the media, who lie to everyone, and future characters believe it's all true until they Spot the Thread.
 * In Ringworld's Children, it is discovered that the reason you can't go too close to a gravity well in Hyperspace is not because the gravity well will cause the hyperspace engine to wrap up on itself into a singularity and take the ship with it, it's because of monsters. Hyperspace monsters.
 * In the original Ringworld, the natives can't understand what "disease" is, as the yet-unnamed builders hadn't included pathogens when they stocked the biosphere. Someone must've later told Niven that bacteria in the soil would evolve even faster than the hominids, producing new pathogenic strains, because later books do acknowledge that plagues occur on the Ringworld.
 * The Ringworld Throne also retcons The Ringworld Engineers by having the Hindmost reveal that his ship has a quantum computer capable of controlling the solar flare providing thrust to the Ringworld attitude jets precisely enough to avoid exposing the population to radiation, and also has Carlos Wu's nanotech autodoc in storage, without having mentioned them to Louis before.
 * And the ARM is an entire government agency that very nearly got the entire human race exterminated because they kept Retconning human history to erase warfare. In The Colonel's Tiger, they receive a report as to First Contact with the Kzin(Niven's first published story, The Warriors) - they not only immediately suppress the message,
 * OTOH, Niven is fairly defensive of what he accepts as canon at any given time, describing the setting as "playground equipment". In other words, any author can have characters hop through it - and crack their skulls on it - they just can't change anything of notice.
 * Gregory Benford wrote the rather mind-warping "A Darker Geometry", in which the ineffable Outsiders are described as the three-dimensional puppets of a higher-dimensional species. Non-canon.
 * Matthew Joseph Harrington's stories put forth the idea that Pak protectors were actually genetically engineered by the tnuctipun 2 billion years ago during the Slaver wars. He also attributed most of Known Space and Puppeteer cultural and technological development after the second Man-Kzin War to a single human protector, Peace Corben. Non-canon.
 * In 1969, Niven wrote an outline for a novel, "Down in Flames", that would have retconned the entire Known Space universe, but was itself retconned by Ringworld; see Torch the Franchise and Run.
 * Rubber Forehead Aliens: On the Ringworld, with the exception of the garden maps and food animals, pretty much all life is some sort of strange Hominid species. Justified since they all evolved from the same common ancestor as human beings from Earth.
 * Sapient Cetaceans: Dolphins are not only sentient, they helped colonize the planet Fafnir.
 * Schizo-Tech: Especially on the Ringworld due to a combination of size and a plague wiping out the superconductors that most technology ran on back in the 1700s.
 * Science Marches On: Niven sold The Coldest Place to Analog magazine, and the science behind it was disproved prior to its publication. Niven offered to return the check, but the magazine decided to publish it anyway because at the time it was written, the story was scientifically accurate to the best of Niven's knowledge.
 * Any time Niven mentions Pluto, this happens. After The Coldest Place he had the spectacular exploding Pluto from World of Ptavvs, which he's stated he wished he could change if it weren't such an awesome scene and kinda necessary to the story.
 * Turns out the core of the Milky Way is a gargantuan black hole, hence can't explode as this Verse presumes.
 * The whole Pak/human connection became subject to this trope when the genetic relationship between primates and every other taxonomic group on Earth was decisively proven by molecular biology. Likewise, both molecular genetics and basic mycology refute the premise that all extant life descends from yeast.
 * Sci-Fi Writers Have No Sense of Scale: Averted. Seriously averted. The scale of things is mentioned lots of times, usually in a "Holy crap, I can't believe how large this thing is" situation.
 * Not Drawn to Scale: However, many of the artists in various countries who paint covers for the Ringworld novels have a hard time grasping the proportions of it.
 * Shout-Out:
 * Eric the Cyborg calling himself "Donovan's Brain" is a reference to Curt Siodmak's novel of the same name. Whether Eric's last name really is Donovan is unclear.
 * The frumious bandersnatch native to Jinx is named after a creature in "Jabberwocky".
 * In "Flatlander", Beowulf Shaeffer briefly meets a race car enthusiast who cosplays as The Joker. (Impossibly Cool Clothes and Body Paint are fashionable on Earth.) The same story also references Oliver Wendell Holmes' "One-Hoss Shay" ("all at once and nothing first").
 * Beowulf's girlfriend (and Louis' mother) is working for a computer company called "Donovan's Brains" at the time Beowulf first meets her.
 * Shown Their Work: Niven is famous for working out the problems in his ideas. If a new problem comes up, or becomes clear, he will write either a sequel, remake, or some combination of the two to explain it.
 * Recently he re-published a number of his Beowulf Shaeffer short stories with a new story linking them together. This story was jam-packed with retcons intended to fix previous problems.
 * Sonic Stunner: It's taken for granted that readers know how these behave.
 * Space Clothes: Most space travellers wear comfortable, recyclable clothing made out of paper. But only while aboard ship.
 * Space Cold War: The state of things between the Humans and the Kzinti, after the last Man-Kzin war. Humans aren't completely serious about it; Kzinti always attack before they've prepared properly, so the humans invariably beat them back and take a few more worlds as peace concessions. It's expected the Kzinti will learn to stop attacking humans before they learn how to actually beat them.
 * Space Navy: The UN creates this when they relearn the ways of war thanks to the Kzin.
 * Space Police: The Goldskins (so named because of the color of their pressure suits) who patrol the Belt for smugglers.
 * Space Whale: The starseeds.
 * Spock Speak: Aliens for whom Interworld isn't their first language tend not to use contractions and prefer to use the present tense rather than the present progressive. Human emotional inflections need to be consciously added to their speech, so it's notable than when Puppeteers become frightened, their speech increasingly sounds less emotional.
 * Spoiler Opening: At the beginning of Fleet of Worlds is a timeline that ends with "New Terra charts its own course." This was supposed to sound cryptic, but it gives the book's ending away, especially if you notice that the Fleet of Worlds is described as having six planets during this novel, but in Ringworld it only had five.
 * Standard Sci Fi History: One of the examples in which humanity colonizes the solar system, and later the stars. It also involves a lot of alien contact.
 * Starfish Aliens: The Puppeteers, the Outsiders, Bandersnatchi, and especially the Jotoki and Gw'oth, which actually resemble starfish.
 * Starfish Language: The Puppeteer language sounds "like a steam organ exploded". The Outsiders communicate using colored lightbursts, and the Bandersnatchi communicate only using writing... using their own bodies as writing implements and empty fields as a writing surface (generally, you have to read Bandersnatch writing from orbit...)
 * Subspace Ansible: Hyperwave signals are much faster than hyperdrive starships, but can only broadcast from station to station outside of the gravity well of a star. The signal must be converted to standard light-speed communication to actually reach a planet, so it could still take hours to make a phone call from Earth to Alpha Centauri.
 * Superweapon Surprise: See the entries below for Wave Motion Gun: "Madness Has Its Place" and Weaponized Exhaust.
 * It's canon that while the vast majority of humanity truly believed that they had become a peaceful, demilitarized race, the ARM specifically directed technology to develop this way, just in case. Good thing too, once humans encountered the Kzinti. Surprise!
 * Also a major point in Ringworld, as Nessus the puppeteer goes around their exploration ship pointing out exploration tools and explaining their mundane use, but also mentioning to please be careful not to point this end at your best friend and push this button here or he might not be your best friend anymore. Or anything more than a rapidly dispersing cloud of ionized gas, for that matter. But it's not a weapon, honest!
 * Acknowleged and poked fun of in the same book: all these not-weapons and Nessus's insistance on their ship being unarmed inspires Louis Wu to name the ship "Lying Bastard".
 * Technology Marches On: In the Kzinti story Cathouse, the human protagonist has a pocket computer with a capacity of a whole 100 megabytes!
 * Teleporters and Transporters: Transfer booths on Earth and other planets. Stepping discs on the Puppeteer homeworld.
 * They Call Me Mister Tibbs: In Niven's later works "Fly-By-Night" and Ringworld's Children, humans have started using the title "LE" (Legal Entity) to address members of intelligent species who aren't prisoners or fugitives. One reason for this seems to be to give kzinti a legal basis for hunting particular sentient beings as prey. No other author has tried using the term "LE" in their Known Space stories.
 * Too Many Halves: From Destiny's Forge:

Cherenkova: That's three halves.

Tskombe: If I was smart enough to do math I wouldn't be in the infantry."


 * To Serve Man: Kzinti have hunted and eaten humans on colony worlds they conquered during the Man-Kzin wars.
 * Too Dumb to Live: The Kzinti. Between their room temperature I.Q.s and their uncontrollable hair-trigger tempers they lose every single fight they get into with anyone. The Man-Kzin Wars books are especially full of this trope; by Ringworld we get a main character kzin who is only somewhat stupid and inept.
 * They get smarter as time goes on due to natural selection. The dumbest ones get killed by humans the quickest, so after several hundred years of wars...
 * The Kzinti aren't so much dumb as it took them three or four losses in the Man-Kzin wars to learn the "think" step before "scream and then leap"...
 * Again, they didn't so much "learn not to do it" as "every Kzin with violent instincts strong enough to inhibit forethought died before they could breed". Natural selection in action!
 * In Destiny's Forge, the Patriarch makes the point that the expansion of the Patriarchy is an important safety valve to direct the aggression of the Prides outward, rather than focused on each other, and that he cannot dictate that the continued raids against humans stop without giving the Prides something of equivalent value that the humans are conceding.
 * It should be noted the Kzinti were enslaved in their early bronze age by another species who valued their martial abilities. The Kzin of course rebelled and used their former masters to uplift their species. They also tinkered with their genetic code. Essentially they wanted an army of Bronze Age heroes and their women to not be so Naggy. So the Men now rage and leap before they think, valuing bravery and strength over intelligence. The women were tinkered with enough to be come non-sentient.
 * Literally so with the Thrint. Once they developed their psychic mind-control powers and could get their slaves to think for them they no longer needed to evolve intelligence any further, something they never got very far with to begin with.
 * Arguably, the Pak succumbed to being Too Dumb to Live because they're so brilliant that their hyperrigid thought processes blind them to the unorthodox solution. How else could they have overlooked the possibility of storing the scents of their offspring ... or, for that matter, of interbreeding their offspring with one another, thereby uniting their entire race in a common bloodline? No, they just sniff a stranger and reach for the nukes.
 * It's not that they overlooked it, it's that they can't do it. At all. We're not joking about the "hardwired" thing. Pak Protectors do not have free will; their only drive is to grab the greatest advantage for their clan and bloodline, and since other clans want the same advantages, they're enemies and rivals. Because their biological lack of free choice, hyperintellect, and drive to grab the greatest possible advantage, they are literally incapable of cooperating past the moment there is a bigger advantage to be gained by betrayal. If one option gives their team 10 points and the other team 10 points, while a second option gives them 11 points but leaves the other team at 0, they will take the second option every time. And they have no choice in the matter.
 * Then Pak evolution is Too Dumb to Live, for railroading them into behavior that can ONLY get their own bloodlines wiped out, slowly by inbreeding if not quickly by infighting.
 * Inbreeding isn't a problem for the Pak because they kill all babies born with genetic defects. They get so much radiation from living in the galactic core that the baseline rate of birth defects is sky-high already anyway; they probably don't even notice the increase from inbreeding.
 * Not until they run out of offspring, anyway. Hominids just aren't biologically equipped to be Explosive Breeders, so culling genetic flaws can't be sustained indefinitely.
 * Torch the Franchise and Run: Down In Flames was intended to be this, had it ever been completed. Instead, Larry Niven wrote Ringworld and rendered the prospective 'verse-ender obsolete.
 * Transplanted Humans: More like transplanted Homo habilis. Averted because the Pak brought humanity's ancestors to Earth from another planet, rather than the other way around.
 * Played straight with the various hominid species of the Ringworld. The initial Pak breeders mutated over 3 million years on the ring and evolved into different ecological niches which the Pak did not plant (generally those niches normally filled by creatures that killed and ate Pak breeders). With the exception of some transplanted aliens on the continent-sized "garden maps" in the middle of oceans [strike:tens] hundreds of thousands of miles wide, there wasn't so much as an insect that will harm humanoids present. Until Hominds evolved to fill the role.
 * United Nations Is a Super Power: As time goes by, the U.N. develops into a planetary government, enforcing its will through ARM.
 * Universal Translator: Small disks that clip onto a shirt; the more input they receive, the faster they can translate languages. But even then, sometimes they make errors.
 * Victory-Guided Amnesia: In Betrayer of Worlds, Louis Wu (70 years before the events of Ringworld) accepts a job from Nessus with the understanding that his memory of it will be erased afterwards. (It's not even much of a victory because The Bad Guy Wins, probably a Sequel Hook.)
 * Warrior Poet: The Kdatlyno are an entire race of Warrior Poets.
 * Wave Motion Gun: Several. Specifically...
 * In "Ringworld's Children", Human starships are armed with a weapon called simply "The Anti-Matter Bullet"; guess what it fires.
 * The Wunderland Peacemaker, a massive Disintegrator Ray, pretty much single-handedly ended the Fourth Man-Kzinti War.
 * In "Protector", the protector-stage-human Jack Brennan destroys an entire fleet of Pak warships with something he calls the Finagle Gun. It fires bowling-ball-sized pellets of pure neutronium.
 * In "Madness Has Its Place", the Terran solar system is defended from invaders by the Mercury Laser Array (a ring of solar-powered lasers all around the equator of Mercury), which was originally built as launching lasers for light-sail powered spacecraft. Of course, they are powerful enough to destroy ships as far out as the orbit of Neptune. There are also an array of magnetically powered mass-drivers that can fling metallic ore mined from asteroids across the solar system, spreading molten metal across the ships' paths. All of these tools were key in humanity's overwhelming victory over the Kzinti warfleet in the first Man-Kzin War, since Kzinti telepaths had reported that "humans have no weapons at all." It's all but Word of God that all these technologies were created with a dual-purpose in mind by the paranoids of ARM.
 * "The Warriors" brings us the Angel's Pencil, a human slower than light starship, with a main drive that doubles as an interstellar com laser. At maximum thrust, it pulls 1/6th of a g. It slices a Kzinti warship in two before the crew could react, and they'd figured out what was about to happen as it was being targeted.
 * The apex is the Ringworld Defense System. It functions via a superconducting mesh built into the Ringworld flooring material. After causing its sun to flare, it then magnetically excites the flare to lase in X-Ray. Yeah, that's right: it uses a goddamn star as an X-Ray laser. Justified since Pak protectors built the Ringworld: a) it's supposed to be able to destroy rogue asteroids, planets or alien fleets that may threaten the Ringworld and b) protectors are not known for being subtle.
 * Weaponized Exhaust: The warlike Kzinti stumble upon a completely demilitarised humanity. They invade, only to find out that reaction drives and solar sail launching lasers are actually pretty good at blowing things up. Surprise! Humans call this "The Kzinti Lesson": "The more efficient a reaction drive, the more effective a weapon it makes." It came as a great shock to the Kzinti, because their telepathic spies kept telling them that human spaceships were unarmed.
 * We Are as Mayflies: The Pierson's Puppeteers have medical technology so advanced that they are functionally immortal as long as they can stay within easy access of an autodoc. Pak Protectors live for many thousands of years, in the unlikely event that some other Protector doesn't kill them first.
 * We Have Become Complacent: Prior to first contact with the Kzinti, a Protector-stage Jack Brennan had used social engineering to basically remove the more violent elements of man's society. No war, very little crime, and no technology that had no purpose other than being a weapon. Humanity climbed out of its complacent cocoon pretty damned quick once the warcats showed up, however...
 * Wetware CPU: The short story "Becalmed in Hell" has the brain jar of Eric Donovan, who was mortally wounded in an accident, installed in a spaceship designed to explore Venus.
 * What Might Have Been: The collection N-Space includes the essay "Down In Flames", where Niven describes the violent end he once planned for Known Space, before creating the Ringworld and finding that far more interesting.
 * Zero-G Spot: Zero-g sex is far from uncommon, due to zero-g "sleep fields" which work anywhere.