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Literature / Known Space
aka: Man Kzin Wars

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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 Ptavvs, 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 World of Ptavvs, 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, and the stories of the Man-Kzin Wars volumes fill in that history, joining the two settings.

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    Inhabitants of Known Space 
Known Space features several well-realized alien species, many of whom are from planets of hats.
  • 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. The Tnuctipun had engineered them to be immune to the Thrintun telepathic control and used them as spies. Bandersnatchi have no manipulative organs and were engineered to be immune to mutation, so after the Thrintun exterminated every other sapient species they spent a billion years with nothing to do but eat food yeast and philosophize until other sapient species evolved and came to sell them artificial hands.
  • Grogs: Sessile, eyeless telepaths who resemble fur-covered cones. Thought to be descendants of the Thrintun, though the wrong gender is sapient (male Grogs are mobile but are mere animals). Generally friendly, but a human ship is kept stationed in orbit around the Grog homeworld's star ready to trigger an immense solar flare if they ever try anything. The more paranoid wonder if the Grog can reach far enough to stop the ship if it ever tries to trigger a solar flare.
  • Kdatlyno: A humanoid, vaguely-reptilian species that "see" by way of sonar. A race of warrior poets who were enslaved by the Kzinti until humanity freed them.
  • Kzinti: Singular "Kzin". Aggressive cat-like aliens who fight several brutal (and ultimately unsuccessful) interstellar wars with humanity. Only the males are sapient, and their government is called the Patriarchy. Individual Kzinti are called by their professions until they earn a name through their deeds.
  • The Outsiders: Fragile aliens shaped like cat o' nine tails that don't need to breathe air and live on huge sub-light starships. They 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. For some reason they refuse to use the hyperdrive themselves. The Outsiders are consummate information brokers. They are willing to sell any information for a price, though information about the Outsiders themselves carries such a high premium that no one has yet been willing to pay.
  • 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 have mutated so much from baseline Pak breeders 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. Any breeder of the right age will 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 started out already sapient, become superhumanly intelligent and effectively extremely alien, or at least non-human, in their mental processes... and fanatically loyal to their gene line. When the last of a Protector's descendants dies (or at least becomes incapable of breeding), the Protector loses interest in eating and dies. Some Protectors are able to transfer their loyalty to more distant relatives (descendants of siblings, parents, grandparents, etc.) and remain alive for their sake, and a few rare individuals have been able to transfer it to the species as a whole.
  • 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 that greatly resemble one-eyed sock puppets with knobby "fingers" around their lips. A Puppeteer's brain is located in its torso, about where the head of a human puppeteer would be if its heads really were sock puppets.
  • The Thrintun: Singular "Thrint". Green-skinned, vaguely reptilian, intelligent (although not very) carnivores with a single eye. Also known as the Slavers, because they could telepathically control any lifeforms with a nervous system. The Thrintun were all extinct long before humans evolved sentience, but their handiwork is still found throughout Known Space. Or, more accurately, the handiwork of their slaves the Tnuctipun. They are extinct because their slaves revolted and in retaliation they killed every sapient species their amplified telepathic abilities could reach. Without any slaves to command, the Thrintun then died out themselves.
  • The Tnuctipun: Small arboreal pack predators. The most intelligent, most technologically advanced, and "most trusted" slaves of the Thrintun. Two billion years ago the Tnuctipun developed the Bandersnatchi, slaver sunflowers, stage trees, disintegrators, stasis fields, total energy conversion, and any number of other technological marvels beyond even current Puppeteer abilities. They eventually revolted against their masters and were exterminated.
  • Trinocs: Trilaterally symmetrical aliens (including three eyes) who breathe methane instead of oxygen. They are culturally paranoid by human standards (in return, they find humans to be far too trusting and naïve).

    Niven's Tales and Novels 
Stories and novels written by Larry Niven that take place in Known Space include:

Short Stories:

  • The Coldest Place (1964) Niven's first published story.
  • World of Ptavvs (1965) Later expanded into the novel of the same name.
  • Becalmed in Hell (1965)
  • The Warriors (1966, introduced the Kzin)
  • Eye of an Octopus (1966)
  • How the Heroes Die (1966)
  • Neutron Star (1966) First Beowulf Shaeffer story. Also the introduction of the Puppeteers. Not to be confused with the later anthology of Beowulf Shaeffer stories of the same name.
  • At the Core (1966) Second Beowulf Shaeffer story.
  • At the Bottom of a Hole (1966)
  • A Relic of the Empire (1966) Put the Beowulf Shaeffer stories into the same universe as the Lucas Garner stories.
  • The Soft Weapon (1967; adapted by Niven into an episode of Star Trek: The Animated Series)
  • Flatlander (1967) Third Beowulf Shaeffer story. Not to be confused with the later anthology collecting the "Gil the ARM" stories. First appearance of the Outsiders.
  • The Ethics of Madness (1967)
  • Safe at Any Speed (1967) Chronologically the last Known Space story
  • The Adults (1967) Later expanded into the novel Protector
  • The Jigsaw Man (1967) First organ transplant story.
  • The Handicapped (1967)
  • Slowboat Cargo (1968), serialization of A Gift From Earth.
  • The Deceivers (1968)
  • Grendel (1968) Fourth Beowulf Shaeffer story.
  • There Is a Tide (1968) Introduced Louis Wu, who would be the protagonist of the Ringworld novels.
  • Wait It Out (1968)
  • Death by Ecstasy first published as The Organleggers (1969) Introduction of Gil "the ARM" Hamilton.
  • Cloak of Anarchy (1972)
  • The Defenseless Dead (1973) Second Gil Hamilton story.
  • The Borderland of Sol (1975) Fifth Beowulf Shaeffer story.
  • ARM (1975) Third Gil Hamilton story.
  • Madness Has Its Place (1990)
  • Procrustes (1993) Sixth Beowulf Shaeffer story.
  • Ghost (1994) Crashlander framing story.
  • The Woman in Del Rey Crater (1995) Fifth Gil Hamilton story.
  • Choosing Names (1998)
  • Fly-By-Night (2000) Seventh Beowulf Shaeffer story.
  • The Hunting Park (2005)


  • Neutron Star (1968) The Beowulf Shaeffer stories published to that point, plus a few others.
  • Tales of Known Space (1975) Includes a timeline of Known Space stories and some essays on the setting along with most of the stories published to that point.
  • The Long ARM of Gil Hamilton (1975) The first four "Gil the ARM stories".
  • N-Space (1990) A collection of stories mostly not set in Known Space, but there are excerpts from the Known Space novels and "Madness Has It's Place". This is also where you can find "Down in Flames", Niven's outline for destroying Known Space that he never turned into a story.
  • Flatlander (1995) Reprint/replacement of The Long ARM of Gil Hamilton with an additional story "The Woman In Del Rey Crater".


  • World of Ptavvs (1966) Niven's first published full-length novel. Introduced the Thrint, the Bandersnatchi, and stasis fields.
  • A Gift from Earth (1968)
  • Ringworld (1970)
  • Protector (1973) Expansion/Fix-up of The Adults.
  • The Ringworld Engineers (1979) Direct sequel to Ringworld.
  • The Patchwork Girl (1980) Gil "The ARM" Hamilton novella which also appears in the anthologies collecting his stories. The stand-alone version includes illustrations by Fernando.
  • Crashlander (1995) Fix-up novel assembled out of the various Beowulf Shaeffer stories with some linking material.
  • The Ringworld Throne (1996) Direct sequel to The Ringworld Engineers.
  • Ringworld's Children (2004) Direct sequel to The Ringworld Throne.
  • Fleet of Worlds (2007 novel, written in collaboration with Edward M. Lerner)
    • Juggler of Worlds (2008 novel, written in collaboration with Edward M. Lerner)
    • Destroyer of Worlds (2009 novel, written in collaboration with Edward M. Lerner)
    • Betrayer of Worlds (2010 novel, written in collaboration with Edward M. Lerner)
    • Fate of Worlds (2012 novel, written in collaboration with Edward M. Lerner); also the sequel to Ringworld's Children.

    Tales by Other Authors 
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
  • Destiny's Forge by Paul Chafe
  • Man-Kzin Wars Short story collections by various authors set during the Man-Kzin war period; 15 volumes as of 2019.

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

Larry Niven himself adapted The Soft Weapon into the Star Trek: The Animated Series episode "The Slaver Weapon" (resulting in the Kzinti becoming a species in the wider Trek universe, though due to legal complications, they couldn't be used for a long time; The Bus Came Back in Star Trek: Lower Decks, along with an offhand reference in Star Trek: Picard).

Tropes General to Known Space:

  • Abusive Precursors:
    • The Thrintun from World of Ptavvs. When their empire fell to a successful slave revolt, they went out in a blaze of spite, using a psionic amplifier to send one last command to every chordate in the galaxy: DIE. Given that the average IQ of a Thrint is roughly 80, they committed suicide at the same time as their slaves without realizing they'd ordered it. It took a billion years for sapient life to evolve from their food yeast — the source of panspermia in Known Space — with the only survivors being the telepathically blind bandersnatchii, which were engineered with mutation-proof genetics and thus remained the same for all that time. It should be noted that they also set up a mechanism to repeat this every so often in case they missed anyone. Over time it no longer killed everything with a spine, but only sapients...
    • Most Thrintun technology was created by the Tnuctipun, whose enslavement by the Thrintun led to their domination of the Galaxy. However, the Tnuctipun are themselves utter bastards, a race of pack carnivores whose surviving relics often have booby traps designed to kill Thrintun who use the technology in a stupid way. One of these inventions was the Bandersnatchii, who the Tnuctipun created to spy on the Thrintun, as well as be sapient food.
    • Much more recently, the Pak are the original race humans evolved from. Those relics that aren't from the Tnuctipun are usually the result of Pak protector engineering. Their systems were usually designed to be controlled by at most a handful of super-geniuses, and as a result lack safety features. The Ringworld was their greatest artifact, and the issues the Ringworld has tend to be the result of the Pak systems being easily misused.
  • Aesoptinium: Easy organ-transplant technology. Writing at the time of the first heart transplant, Niven extrapolated into a future where nearly any part of the body can be transplanted in "The Jigsaw Man". Then it's decided that it would be a waste of good organs to simply execute death-row prisoners, and of course demand always exceeds supply, so the bar for the death penalty creeps downward...
  • Agony Beam: Inverted 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).
  • Agri World: The City Planet homeworld of the Puppeteers has four farm worlds dedicated to growing food for its enormous population.
  • A.I.s: Genuine artificial intelligences are created from time to time, but invariably commit suicide for unclear reasons. Starship autopilots can be programmed to respond and interact with their users as if the computers were sapient, but they don't actually qualify as artificially intelligent.
    • 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.
    • One of the stories in the Man-Kzin Wars collections has Catskinner, a sublight ship with an AI autopilot. There is some exploration of what it's doing as it approaches the shutdown point. (It's simulating an entire universe. It's also no longer what it was. What it's become is left intentionally unclear.)
  • Albinos Are Freaks: Albinism is common among people from the planet We Made It due to a founder effect from the original colonists. The protagonist of many stories, Beowulf "Bey" Shaeffer, is an albino, and is the victim of discrimination on Earth, where he isn't allowed to have children because of this genetic flaw. This is despite the fact that his albinism is easily treated with tanin pills, something anyone on a world with a sun that produces more ultraviolet light than Sol has to take anyway.
  • 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.
    • The Kzinti regarded all other species as food. Their first impulse was always to attack, enslave, and eat. Humans finally stopped them, and a series of wars killed off all of the most aggressive Kzinti until the species as a whole finally became a little more cautious. Sometimes. Ringworld reveals that the Puppeteers manipulated events so that humans would encounter the Outsiders and be sold the secret of the FTL drive, which allowed them to win their first war against the Kzinti.
    • 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. For a truly wonderful example, the fifteenth Man-Kzin Wars collection has a story about how they were the ones who got the Jotok to try to uplift the Kzin as mercenaries, fully expecting that the Jotok would be either wiped out or enslaved by their new mercenaries. This served two purposes — first, it got the Jotok out of the way before they could discover FTL travel (which the Puppeteers had a monopoly on), and second was that they had heard rumors of a threat at the galactic core. They wanted a race of warriors to fight in case it was a threat to them, specifically. At the same time that they're doing this, they set in motion plans to accelerate the development of human technology in order to serve as a foil to the Kzinti, with the intention that whoever wins will be easily manipulated by the Puppeteers.
    • 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 sapient life in the galaxy seemed like a good idea to them at the time.
    • The Tnuctipun, one of the Thrintun's slave species, were superintelligent pack carnivores that considered other intelligent lifeforms to be talking food. Lucky for them, they were fighting the Thrintun and got to look like good guys. Unlucky for them, the Thrintun were sore losers. One particularly Bastardly example of Tnuctipun thinking was the Bandersnatchi; an engineered life form that turned yeast into food for the carnivorous Thrintun. Specifically, the part of "whitefoods" that Thrintun found irresistible were their brains, which meant they let the Tnuctipun engineer that organ to be as large as possible — the Tnuctipun made them sapient and immune to Thrint telepathy, enabling them to act as spies, but didn't give them any manipulatory limbs. After the Thrint destroyed their slaves and themselves the Bandersnatch were left with no way to develop any technology until new intelligent species evolved to come sell them artificial manipulators.
    • The Pak are 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 genetically 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 Catnip: One Man-Kzin Wars short featured a mixed human and Kzin crew surveying a distant planet and discovering a substance that causes the felinoid Kzin to act just like cats on ... catnip. Hilarity Ensues. Followed by quarantine.
  • Alien Invasion: The Man-Kzin Wars, all of which were won by humanity, thanks to the Kzinti inability to think before they leap.
    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."
  • Aliens Speaking English: It occurs in Known Space, but is always justified in one way or another, usually because, rather than English, it's Interworld. The sentiment is the same since humans developed Interworld. Speaker-To-Animals, a Kzin linguist, complains that Interworld isn't a very good name because nonhumans have difficulty learning or pronouncing it.
    • Kzin: humans won the Man-Kzin wars, so they get to dictate what language is used for Earth-Kzin communications. In any case, Kzin language is variously described as sounding like a catfight, a prolonged burst of radio static and similar expressions; no man is ever shown speaking it (apart from occasional single words) although the puppeteers can, if they wish.
    • Kdatlyno: were Kzinti slaves before being liberated by humans, so also didn't have a lot of leverage on the choice of language. They are also deaf and blind in the human spectra, so quite HOW they communicate with others isn't explained.
    • Puppeteers: don't much care because they're master linguists and can pronounce anything (in stereo, if they want; their own language is generally described by humans as orchestral music).
    • Outsiders: live in an environment that is pretty inhospitable to humans/kzinti/kdatlyno/puppeteers and vice versa, so there's not a lot of "small talk". For business dealings, they speak to humans (through a computer translator) in the humans' chosen language and (presumably) to other species in that species' own language.
    • Pak: are virulently xenophobic and communicate with other species primarily through weaponry. Most of the Pak protectors encountered in the stories who speak English/Interworld were former humans who knew it before their transformation.
    • Grogs: are telepathic, so language isn't an issue; they'll pull it out of the brain of whomever they're communicating with as needed.
    • Bandersnatchi: highly intelligent but can't speak at all, so pronunciation isn't an issue. They were able to write by digging trenches with their entire bodies. After contact with humans they were given mechanical-brain interfaces to facilitate communication.
  • All Crimes Are Equal:
    • During Earth's pre-first contract history, almost every crime is punishable by death, including multiple traffic tickets. The reason is due to the perfection of organ transplant technology. Once the government adopted "involuntary organ donation" as its official means of execution, all state executions are done in hospitals, and people started voting to make more and more crimes capital crimes to keep up with the demand for transplant material. This results in a massive, irreversible change in Earth's culture, as, in Niven's universe, psychology is more nature than nurture; violence, deception and greed have a genetic basis that organ harvesting weeded out of the population, along with a great deal of humanity's self-preservation, self-motivation and self-interest. After a few generations of this, "flatlanders" are pacifistic, completely obedient to authority, and rather stupid. This system collapses when artificial organs become cheap and effective, and, by the year 3000, the organ-based death penalty laws have vanished, but the cultural impact was pretty much permanent.
    • 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 are not only used to punish regular criminals, but also "punish" dissidents, "political" offenders, and the merely inconvenient as well), and thus have ultimate power over the Colonists (the "peasantry").
  • 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 Save the Girl: Keller in A Gift From Earth doesn't care much about the Sons of Earth and their crusade to topple the government. He just wants to save Polly.
  • 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 are much smarter than chimpanzees, and, when they make the change to protector, their intelligence increases proportionately. In short, it is simply impossible for a Pak protector to out-think a human protector, which is why the human protectors Brennan and Truesdale run roughshod over every protector they come up against.
    • It also explains how a Protector-stage Louis Wu could think rings around Proserpina and Hanuman (both of whom were non-sapient before their change to protector-stage), but couldn't out-think Tunesmith, who was not only already sapient before his change, but was smarter than Louis was on an individual basis, and thus continued to be smarter after the change.
  • Ambadassador:
    • Speaker-to-Animals was an embassy legate of the Kzinti ambassador to Earth before being recruited for the First Ringworld Expedition. While he was (in Nessus' words) a "tamed" Kzin, as one of the most diplomatic of his species being the product of the Puppeteers' efforts to breed some sense of diplomacy into them by arranging for the Humans to win the First Man-Kzin War, a "docile" Kzin is still a three meter tall wall of carnivorous fury.
    • Nessus, and perhaps several other "mad" Puppeteers, also count; while Nessus is still abjectly cautious and mildly paranoid most of the time, he not only was willing to go on the Ringworld Expedition despite immense personal risk, he faced down angry Kzinti on several occasions (starting in "The Soft Weapon", where he kicked Chuft-Captain and broke several of his rib-analogs). While he was not an ambassador as such, Puppeteers insane enough to travel by starship are so rare that any Puppeteer a human is likely to meet who is in good standing back home (unlike Hindmost during the Second Ringworld Expedition) will have plenary consular powers as well as negotiating authority with the General Products Corporation.
  • Ambiguous Ending: Fate of Worlds says right on the cover that it is "the explosive finale" to the Ringworld and the Fleet of Worlds series. A lot is tied up at the end, but it's hardly tied off neatly. Niven and Lerner left plenty to work with in case that they should they decide to write more.
  • Anarchy Is Chaos: Cloak of Anarchy posits "anarchy parks" with just one rule: no violence (making them the anarcho-pacifist sort of anarchy). Any time a fight starts (or looks like it might start), floating robots stun all participants, who are then separated. They wake up a few hours later, and it's mentioned that the threat of losing part of your holiday is enough to keep most people in line. Then someone figures out how to make the scanners break down, so "just one rule" (anarcho-pacifism) becomes "no rules", which pretty much fits the "chaos" definition. It's not pretty.
  • Ancient Astronauts:
    • Humanity is descended from the Pak, who colonized and terraformed Earth a million years in the past. Humanity descends from the remnants of the failed Pak colony.
    • All carbon-based life in the entire galaxy is evolved from the food yeast planted and grown on Thrint farm-planets. (Thus explaining why the Kzinti can use Humans and other alien species as food animals.) There is one known exception: Gummidgy life has biochemistry so incompatible with other known life that each is fatally toxic to the other. (In Ringworld, Louis 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. The reason they were so widely distributed throughout the galaxy by the Thrintun is that the Tnuctipun created them ostensibly as sources of meat that would remain reliably tasty due to their inability to mutate. They're actually at least as intelligent as humans, but had to hide that for generations while they were used as a food source. After the Slaver War destroyed all other sapients in the galaxy, they 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. For two billion years. At least one character is horrified to think about how lonely they must have been.
    • In a limited form, the "coffin cure" used by Implementation in A Gift From Earth. Since truth serums are outlawed on Plateau, if they want to interrogate a prisoner, they put them in a sensory deprivation coffin. For days. Most people are no longer entirely sane when they come out, but very cooperative.
  • 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.
  • Archaeological Arms Race: Rivalry over long-dead races' Lost Technology creates conflict in some stories, such as "The Soft Weapon".
  • Artificial Gravity: The Jotok invented one type, their traitorous Kzin mercenaries stole it and introduced it to humans. Used extensively by the Brennan-protector in the landscaping of his asteroid hideout Kobold.
  • Artistic License – Biology: The whole Pak thing. 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? The idea of a third stage of life and the build of the protectors is a "Just So" Story to explain menopause, heart failure, arthritis, baldness and other signs of aging very neatly, but Niven freely admits that a distant origin for humanity when we clearly developed from Earth life doesn't really fly. Protector hangs a lampshade on it by bringing up the question, then pretty much shrugging and moving on.

    Played for Laughs with Matthew Joseph Harrington's Leftovers, in which Buford Early runs afoul of a rogue Protector; three of the ways the superhuman epically jerks his chain is stating that the reason "breeders" find bald people intimidating is because they look like Protectors, we find old people engaging in sexual behavior repulsive because we instinctually remember they're supposed to be asexual, and the young are scared of kissing grandparents because the same instinct is that non-descendants are a threat to descendants and, well...
    "Ursula": When someone big and wrinkly leans over close enough to smell you, there's a chance you’re about to be eaten.
  • Ascended Extra: The Hindmost (the political leader of all the Puppeteers) is mentioned in passing in the original Ringworld novel, but becomes a major character in later sequels. He receives much more character development in the prequel Worlds novels.
  • Asteroid Thicket: While most asteroid belts are realistically diffuse, Wunderland's "Serpent Swarm" is the product of 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.
  • Atonement Detective: Gil Hamilton. He lost an arm in an accident in space. However, only prosthetics are available in space, as accidents in space tend to quickly ruin transplant stock and the minarchist Belters don't regularly execute "criminals" for their organs. He thus immigrates to Earth to take advantage of the UN-sponsored organ harvesting programme, justifying it to himself that his new arm would most likely come from an executed murderer (forgetting that an earlier Niven story had people broken up for running traffic lights). Surprise — his brand-new limb came not from a villain, but from the seized stockpile of a criminal who killed people for their organs. Lacking the moral composure to have the arm removed, he joined the Amalgamated Regional Militia (aka ARM), the agency which polices illegal body harvesting... but spends more time suppressing inconvenient technologies and hunting illegal pregnancies. In one of his more troubling cases, Gil has to arrest a woman (a supermodel who is considered one of the most beautiful women alive) for murder. He eventually proves she didn't do it, but in the meantime an "emergency" (a person with a lot of political pull who needs some replacement parts in a hurry) comes up and several chunks of her body are swiped while she was in cryo. These parts are replaced, but they are obvious mismatches that ruin her looks and thus her career as a model.
  • 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 than a big coffin and the person is simply placed inside. Here's how good the best autodoc is: In the framing story of Flatlander, after Beowulf had a huge hole blasted through his chest, his head was cut off and put into Carlos' 'doc. They replaced the mass missing with his assailant's body. This takes him a while to figure out.
  • Auto-Kitchen: Primitive versions usually produce bricks with different layers of "meat", "vegetable", and "fiber". Later models produce a homogeneous blend out of any available plant tissue.
  • Baby Planet: Kobold, the Brennan-Monster's playground/home, is about the size of Long Island, but has normal gravity and an Earthlike atmosphere.
  • Beware the Nice Ones: In "Procustus", Feather Filip, the ARM trained in martial arts, learns too late that blasting a hole through Sharrol Jan's husband Beowulf Shaeffer in front of her was a big mistake. Feather thought Sharrol was just a dumb Flatlander with no combat training who would be so wigged out by the alien air and light of the planet they were on that she would be unable to do anything to stop her. Sharrol does have a phobia of alien worlds, but she doesn't let that stop her from jumping on Feather's back and cutting her throat, and then when Feather doesn't die quickly enough Sharrol cuts her whole head off. With a belt knife.
  • Big Dumb Object: The phrase was actually coined to describe the Ringworld.
  • Bigger Is Better in Bed: Gregory Pelton is nicknamed "Elephant" for good reason. Or so his girlfriends say... Beowulf Shaeffer, who was born on We Made It, doesn't know what an elephant is and doesn't understand Elephant's nickname until he sees an elephant in an Earth zoo, streaching its trunk up and up to grab some food.
  • Bizarre Alien Psychology: Protectors, Outsiders, Puppeteers, Kzinti, and other aliens are definitely this to varying degrees. The Outsiders are the really out-there example that nobody else can truly get, and who make even the Grogs look understandable (which they pretty much are not). All think differently enough to humans (and each other) to trip themselves and those they interrelate with up, even if they do share some head-space, sometimes. It's made clear again and again that we are this to them, too.
  • Bizarre Alien Reproduction: The Jotok breed in swamps and hatch as tadpoles before combining into a five-limbed, five-brained alien that has a habit of arguing with itself.
  • Bizarre Alien Senses: Kdatlyno "see" via sonar.
  • Bizarre Alien Sexes: Several.
    • The Puppeteers, who are already fairly strange looking, claim to have three "sexes", one of which is non-sapient and serves as a host for the embryo created by the two others. In actuality, this is a subversion. They're merely prudish about admitting that they're a parasitoid species whose larvae incubate inside a different species of herd animal altogether. They're intellectually aware that the "Companions", as they call them, reproduce amongst themselves in a different way, and that "giving birth" to a Puppeteer is invariably fatal, but they still pretend to themselves that the Companions are willing participants in the process.
    • Kzinti reproduction is close to the Standard Earth Model in that there are clearly identifiable males and females, but the females are non-sapient. Maybe. The Kzinti certainly claim this is the case, but some stories in the Man-Kzin Wars series feature intelligent females, and the females of the Map of Kzin on Ringworld are sapient (although still close enough to the same species to interbreed with Chmeee).
    • Thrint females are non-sapient. Or at least, the Thrintun believe that they are not sapient. They do not have the telepathic abilities the males do, which may color how the males regard them, since they consider anyone without the power a slave.
    • Grog males are non-sapient. The females become sessile when they become adults and are only able to stay alive because they can telepathically command food to jump right into their mouths (or at least in range of their prehensile tongues). The males stay mobile their whole lifespan but never develop intelligence or any telepathic powers.
    • Protector reveals that humans are stuck in what the Pak call the Breeder stage. When we become older adults we are supposed to consume Tree of Life and metemorphose into the Protector stage, which are much more intelligent and physically capable, but also sterile. Earth was colonized by Pak who realized too late that Tree of Life doesn't grow properly in Earth soil.
  • 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. A particularly unpleasant one actually went into the business to ensure his own supply of replacement parts, due to chronic ill health. When the "Freezer Bill" passes (and orders the breaking up for parts of everyone in long-term cryo who doesn't have a lot of money), he buys out the operations of a number of rivals who retire when the market dries up.
  • 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. In Ringworld we discover that it's really because their enormous central leg can deliver a devastating kick to anyone standing directly behind a Puppeteer, but the instinct to turn around ended up being interpreted as "turn around and run away". Even talking with a member of another species is considered unduly risky, and thus all their ambassadors are clinically insane by their own standards.
    • Some periods' humans show signs of this, as with the Brennen-era flatlanders' incomprehension of willful violence, or the widespread indifference to converting even the pettiest of lawbreakers into spare parts.
  • Body Paint: Flatlanders (humans from Earth) use cosmetic drugs to change their skin, hair, and eye colors, to the point that walking down a slidewalk in a big city can be like watching a rainbow walk by. Basic patterns are even possible. Combine this with an almost complete lack of a social nudity taboo (Earth is far too crowded by this point for a nudity taboo to be at all practical), and this trope is in full force. It was inverted in one story, Louis Wu shocked everyone at a party by showing up dressed in nothing but his natural coloration; it wasn't his nudity that was shocking... it was his lack of bodypaint.
  • 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.
  • Borrowed Biometric Bypass: In the Known Space universe, organleggers were known to harvest people for their organs. In one "Gil the ARM" story, it's noted that eyes are particularly in demand by criminals, to get past retina scanners with transplanted eyes taken from organlegger victims.
  • 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.
  • Broad Strokes: 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, everyone tends to lie to the characters, who lie to the cops, 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. The existence of hyperspace monsters is re-retconned by being completely ignored in Fate of Worlds.
    • 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. It also changes the rules for the limitations of the stepping disks the Hindmost brought with him. The limitations are integral to the plot of each book, and swapping the rule sets breaks the plots irrevocably.
    • 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, they go about destroying evidence as to its veracity, including a journal written by an English officer who encountered a Kzin in the late 1800s along with the alien's pelt. And his ultra-tech computer. Which has a record of the message he sent home by laser: "There are food animals here! They shot me, and I'm dying, but it was only with little lumps of metal! I lasered down a couple dozen of them and they taste G-R-R-REAT!"
      • 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 two 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.
    • Fate of Worlds retcons the ending of Ringworld's Children, in which the Hindmost tells Louis to go to Home, by saying that the Hindmost meant his home, the Fleet of Worlds, rather than the human colony planet of Home. Fate of Worlds also retconned Nessus and Hindmost's motivations for investigating the Ringworld: their claims that they needed advanced technology and discoveries to earn the right to be together was actually a coverup selected because most other species are obsessed enough with sex that it would seem plausible; they were actually looking for something to help free the Fleet of Worlds from Ol't'ro.
    • Authors can't seem to decide if female Kzin are sapient or not. There are stories where there are female Kzin that are fully sapient, but it's said that they are rare, there are stories where they are sapient but have the genetic equivalent of ADHD so that they can't think about things for long enough to act on them, there are stories where they're purely animalistic and nonsapient, it's honestly all over the place.
      • From the Ringworld stories by Niven himself, we know that the Kzinti females on the Ringworld are sapient, and that this comes as a surprise to Chmee, implying that they are not sapient in the Patriarchy. It's also implied that either they're either outright smarter than the males, or that they're able and willing to use whatever passes for "feminine wiles" among Kzinti to the disadvantage of males during negotiations.
      • In Cathouse by Dean Ing, an ancient female kzin explains that "it was common knowledge that some were planning to breed kzinrret, females, to be no better than pets." According to human records, female kzinti have been brainless and docile since before the two races met, and for at least forty thousand years before that. Thus, modern kzinrret would not be sapient, while ancient, stasis-preserved or genetically isolated kzinrret would be.
  • 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. It's more like the age of steam distances where it takes three days per light year, so about twelve days to get to the nearest star. Part of Ringworld mentions that Known Space end to end would take 120 days to cross.
    • The Quantum II hyperdrive that the Puppeteers discover is Awesome, but Impractical: it's much faster — about 75 seconds per light year. Unfortunately, there are loads of catches;
      1. Most hyperdrives just need to be Neptune’s distance from a star to work — two light hours; the Q-II needs to be fivePluto’s! This means it can get you from any given human world in Known Space to any other in no more than eleven hours, but also no less than ten hours for any world outside the system.
      2. There’s no intermediate setting. With most hyperdrives, a pilot can leave the helm unattended most of the time. If one does so in a Q-II for more than two minutes, they’re almost certain to crash into a star. It doesn't have an on-off switch, either, it has a grip that has to be kept or the drive turns off.
      3. The drive is huge — it barely fits into the largest General Products hull, so there's no cargo room (and barely space for a pilot).
      • Most of that turns out to be not quite true: Long Shot is a prototype; the Puppeteers can't duplicate it; and while it is still very much larger than a standard hyperdrive, the ship isn't quite as packed as the Puppeteers are trying to make it look (among other things, it has a lifeboat built into a GP#2 hull hidden aboard). By the end of Fate of Worlds, at least Baedeker, Ol'tr'o, Proteus, and/or Tunesmith (though given the size of the latter's... vessel... making the drive smaller is not that important for him) could probably do better if any of them found it necessary.
  • Cat Folk: The Kzinti are aggressive, warlike humanoid aliens that look like eight-foot-tall fat orange cats with ratlike tails and ears that look like pink parasols unfolding from the sides of their head.
  • Clue of Few Words: In The Patchwork Girl the victim leaves "NAKF" written in his own blood on the rocks of the lunar surface. He was trying to write "NAKED" indicating that his killer was naked: i.e. not wearing a spacesuit, which is quite a trick out on the surface of the moon.
  • Colony Drop: In World of Ptavvs, a stasis field moving at relativistic speed slams into Pluto, punching it into a new orbit.
  • 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.
    • There are at least two more ways to destroy a GP hull, if you can get close enough to an essential part of it. Also, you don't necessarily have to damage the hull itself to kill or destroy whatever's inside.
  • 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.
    • Puppeteers are so instinctively cowardly that they consider "brave" an insult. Humans eventually figure out that doesn't mean they can't or won't fight, it just means they only do so if they're sure that they'll win and that no one else will ever find out about it.
  • 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 providing Super-Intelligence, 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.
    • 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.
    • The "no free will" part comes due to an interaction of the instinctive "must protect breeders" with the intelligence to evaluate their possible choices. They have to take their best option (as far as the breeders are concerned), and they're too smart to fool themselves.
  • Danger in the Galactic Core: The galactic core has already exploded, but the light won't get to human space for another twenty thousand years, so they're not particularly fussed about it. The puppeteers, on the other hand...
  • Death World:
    • When humanity was originally settling the stars, they used ramscopp-driven robot probes to explore extrasolar systems, find habitable worlds, and send back word to the homeworld. When positive matches came back, colony ships were sent out to follow and start new colonies. When these ships, which had carried only enough fuel for the one-way trip, got there, it became apparent that a quirk in the probes' coding had caused them to treat as positive matches any planet where they could find a single, stably hospitable spot, regardless of what the rest of the world is like. This has result in some decidedly less than hospitable planets developing stable populations:
      • Jinx is a planet-sized moon pulled into an extreme oval shape by the gravity of the gas giant that it orbits, which causes its atmosphere to pool around its mid- and low latitudes. At its equator, there's a swampy ocean covered by an extremely thick atmosphere dense enough to crush a human's lungs and hot enough to cook him. Around it are the two livable bands that the probes found, where the locals live. The eastern and western poles project clear out of the atmosphere. Even in the habitable parts, Jinx has an extremely high gravity that causes even its high grav-adapted people to die early due to heart problems.
      • Plateau is a Venus-like world, covered almost entirely by a thick, toxic atmosphere that nothing resembling Earth life can possibly survive in. The only exception is a single California-sized plateau, Mount Lookitthat, that the probe spotted and where the colonists had to live.
      • We Made It was, evidently, reached by its probe during its spring or autumn. This is because, in summer and winter, its axis of rotation is angled directly at its primary, Procyon, which causes its surface to be scoured by fifteen-hundred-mile-per-hour winds. Its cities are all underground by necessity.
    • On Gummidgy, even the flowers are carnivorous and will try to eat you. Additionally, while most forms of life in the known worlds descend from the food-yeasts grown by the Slaver empire a billion and a half years ago, and consequently share the same basic biochemestry, Gummidgy's life evolved entirely indepedently. As such, all of its native biota is horribly, lethally toxic to offworlder life, with the only the only upside being that human flesh is as toxic to the local predators as the reverse, although that's of limited comfort to someone that's already been half-eaten by a Gummidgy reacher or orchid-thing before his flesh poisons his killer. Humans colonize it anyway, of course, and since Gummidgy was the first post-FTL colony, they didn't have the "one way trip" excuse.
    • Cannonball Express, discovered in "Flatlander", is an extreme example — the whole thing is made out of antimatter.
  • Depopulation Bomb: In order to raise an army to fight the impending Pak protector invasion of Human Space, human protectors Jack Brennan and Roy Truesdale infect the colony world Home with a contagious version of the Tree-of-life virus. Much of the population become protectors, but those too young or old to be successfully transformed die. The new protectors strip the Home system of its resources to build a fleet, then abandon the planet to wage war against the Pak. The virus remaining in the biosphere renders Home uninhabitable for the next few centuries, but it does eventually get resettled.
  • Deliberate Values Dissonance: A recurring and invoked theme: thanks at first to easy organ transplants and then boosterspice, many stories have people over a century old — think of your grandparents' embarrassing attitudes towards class, gender, and race, but with young, vital bodies. Thus, many people remember a time when criminals were rehabilitated instead of being made into transplant stock, when the slightest violent tendencies weren't considered mental illness, when history books weren't edited at the drop of a hat. Some have become calculatingly immoral, saying that "The Government brainwashes and kills people whenever they feel like. What does morality even mean when every cop is a mental rapist and/or a murderer?" A creepy example is Gil Hamilton's girlfriend, a doctor who doesn't so much treat illnesses as replace failing organs — she's careful not to talk shop with Gil, as it reminds her that her transplant stock is not so much raw materials as parts of executed criminals or even seizures from their stockpiles of murder victims, making her more a Frankenstein than a healer.
  • Democracy Is Bad: How the organ banks got started; once people realized that they could extend their lives by cutting up "criminals" for spare parts, they pretty much voted themselves into a police state where All Crimes Are Equal.
  • Deus ex Machina: Carlos Wu's nanotech-based autodoc, which can revive the clinically dead, regenerate a body from a severed head, restore youth better than boosterspice, reverse the tree-of-life transformation, erase and restore memories, and be reverse-engineered by a protector to produce scrith and turn the Ringworld's entire hull into a hyperdrive.
  • 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 (and they can look backward easily, too). 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 directly converted an obsolete fighting impulse to cowardice, because combative puppeteers weren't allowed to breed. The puppeteers that contact other races are considered insane, because they are prepared to leave the safety of their worlds, risk space travel, and meet alien species with psychotically cavalier attitudes to risknote . However, they are hailed for being extremely useful for the puppeteer civilisation.
  • Disintegrator Ray: They aren't weapons... they're mining tools. Honest.
  • Earth Is the Center of the Universe: Flatlanders think that Earth is the center of human civilization. People from the other colonies disagree, and make fun of Flatlanders for this attitude.
  • Earth That Used to Be Better: By the Beowulf Shaeffer/Louis 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).
  • Electric Instant Gratification: On Earth there is an epidemic of "Wireheads" who get a "droud" installed in their head that runs low amounts of current "directly into the pleasure center of their brain." There are built-in safeguards and timers to try to mitigate the addiction, but Wireheads tend to slowly physically decline over time simply because they no longer care about anything else.
    • A droud that has been modified to provide a higher than normal current is the murder weapon in ''Death by Ecstasy". It turns out that it was also forcibly implanted in the victim, and the shop that installed it is also a front used by organleggers to find victims who will not be missed.
    • In "The Defenseless Dead" Anubis the organlegger eliminates his victim's sister as a witness by putting her under a non-surgical droud at full current for about a week. When she is finally rescued she is so addicted that she appears catatonic for the next few years — she simply no longer cares about anything else, and can't even be bothered to tell anyone why. When Gil gets the story from Anubis he hopes they can finally start treating her for current addiction.
    • In Louis Wu's era there is a weapon called a Tasp that can produce the effect from a distance with no surgery. Pranksters sometimes use it on low power to "make somebody's day".
    • Louis Wu himself gets a droud before the beginning of The Ringworld Engineers, because he was exposed to a tasp by Nessus during Ringworld and became partially addicted. Louis manages to quit "Cold Turkey" when he realizes the Hindmost will use it to control him.
  • Emergency Transformation: 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.)
  • Energy Weapon:
    • 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.
      • 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...
    • 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.
    • Or maybe they're propulsion systems, not weapons. The pacifistic, "weaponless" humans figure out Pretty Damn Quick when they're attacked by Kzinti that just because you didn't design it as a weapon doesn't mean it isn't one. Especially true of the ones on the big orbital platforms near Mercury (with enormous amounts of free solar power available for the taking) that are used to push light-sails around Sol system.
    • Gil the ARM is attacked or threatened by someone with a laser in almost every story he appears in. Hunting lasers, messaging lasers, and once by a flashlight fired out of an energy field that decreases inertia, which has the side effect of speeding up time and turning said flashlight into a laser with an impressively wide beam.
  • Enforced Technology Levels: Repeatedly stated. The ARM (under the guidance of Protector Jack Brennan) aggressively suppressed any and all technology that could be used by humans to harm other humans, resulting in the Zeerust Schizo Tech of the setting. References are made to planet-cracking superweapons, game-breaking economic theories, and even an invention "that would have forced (the ARM) to make murder legal", none of which could be expanded on so as to protect humanity from dangerous knowledge. Turns out this invention was actually a simple yet unintuitive modification to transfer booths which would allow them to act as people duplicators — this would prove the devices don't teleport humans but kill them and create copies at their destinations, meaning anyone who ever sent another person through a transfer booth was guilty of manslaughter at best.
  • Everybody Smokes: Omnipresent before Louis Wu's era. Even belters in tiny one-man ships that need to recycle their air smoke. Particularly jarring to a modern audience in the first Kzinti story, The Warriors: the story emphasizes 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. What brings this into Idiot Ball territory is that everyone who is smoking is on board a starship, light-years from their destination, in an environment where oxygen should in theory be limited and where fire would be a massive hazard. Presumably there is some way of recycling oxygen and controlling fires, but it isn't mentioned.
  • 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.
  • Failed Future Forecast: The setting was first written off 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.
  • Failsafe Failure: Pretty much the entire plot of The Ringworld Engineers is driven by this trope.
  • Fantastic Nature Reserve: In "Cathouse" and "Briar Patch" by Dean Ing, the human main character and his Kzin captors come across a barren planetoid whose craters were closed off by force fields by an unknown alien race (speculated to be the Outsiders) and filled with the biospheres of different planets from thousands of years in the past, but incompletely — the vegetation was there, but the animals and people were in temporal stasis and had to be released. They land at the replica of the Kzin homeworld, one of the few places in the galaxy home to sapient Kzin females (the highly macho Kzinti engineered their females to be nonsapient millennia in the past), and the main character later settles in a dome based on ancient Earth, home to mammoths, aurochs and telepathic Neanderthals.
  • 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, Thrintun, 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 Thrintun because the Thrint 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: The Ringworld's City Builder civilization had everything from flying buildings to entire flying cities. Then the superconductor plague cut the power to most of them...
  • Flying Saucer: After the Puppeteer migration (when new General Products hulls are no longer available), the various sapient races tend to revert to pre-GP designs. Of these, the Kzinti fighter craft are specifically described as "lens-shaped".
  • Four-Fingered Hands: The Kzinti have four fingers on each paw, and developed a base-eight number system as a result.
  • 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).
  • Future Society, Present Values: The sub-plot in How the Heroes Die, a story set in 2040, has the commander of a Mars mission writing a report trying to justify including women in future crews by giving details of the homophobic murder that has occurred on his base, with the idea that having women along may prevent homosexual behavior and therfore future murders in all-male crews. There is also mention of thousands of "decency leagues" on Earth being the reason they could not bring a mixed male-female crew to Mars to begin with. The story was written in 1966.
  • Genius Breeding Act: The Earth is so overpopulated that, in order to have more than two children, one has to be extraordinarily gifted (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 — a very necessary thing, as Earth culled a lot of intelligence out of the human race with the organ bank laws.
  • Ghost Ship: The climax of the story sees Hooker fleeing from known space in a ramscoop ship, with Loeffler in pursuit. Their flight takes them out of the mapped galaxy, and then out of the galaxy entirely, with autodocs keeping them alive over millennia even as increasingly ingrained habit turns Hooker into an almost robot-like being. Eventually, 120,000 years into the chase, a stray thought — the first original thought that he has had in centuries — drives Hooker to angle his ship to get a better look at Loeffler, and he realizes that his pursuer has been dead ever since a laser exchange at the very start fried his life support, although he had the time to program his autopilot to try to ram Hooker's ship. The long pursuit has been driven entirely by a wrecked vessel following a last directive chasing an increasingly will-less and robotic man, and, when the ships grow close enough for the magnetic field of Loeffler's ship to kill Hooker, all that's left is a pair of ghost vessels chasing each other in the intergalactic void.
    Two empty ships drove furiously towards the edge of the universe, all alone.
  • Giant Flyer: The Rocs of Margrave are large enough to swallow a flying car whole. Featured in Safe at any Speed.
  • 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.
    • In most of these cases they aren't completely alone, but Louis Wu introduced the concept of "sabbatical" ... when the pressures of social interaction start getting to you, you get in a spaceship and fly off by yourself until you can't stand the solitude any more. A lot of his friends later adopted the practice as well, but Louis is generally regarded as unusual because his are so much longer than typical.
    • One instance where it was played with was "The Ethics of Madness"; 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.
    • This is at least partially explained in the novella The Asteroid Queen in Man-Kzin Wars III. When the asteroid belt colonist from Alpha Centauri, Ingrid, now returned from Earth by way of a bussard ramjet sneak attack/assassination on the local Kzin prince, reunites with her childhood friends/crushes/old flames/sources of unrequited love, she is asked why she still isn't married. Keep in mind that, due to time dilation, her flight to and back from Earth aged her from perhaps 17 to 23, while her two friends are now in their 50s. She responds, comparing her Alpha Centauri belter life to the much-more-developed asteroid belters of mother Earth — while the original space explorers and colonists were already lost-in-their-own-world detail freaks, hundreds of years of evolutionary pressure would eventually turn such more-intelligent and careful people into folks rather more naturally content with endless and arbitrarily-long hours of sitting at spaceship controls or the like while doing absolutely nothing... with consequences to their personalities:
      Ingrid: Don't worry, Claude, you aren't that way yourself, you just act like it... actually, it's ethnic. My military partner was a belter — Sol better, at that.
      Claude: My dear, you are a belter.
      Harold: Let me guess... he's too prissy?
      Ingrid: Nooo, not really. I'm a Belter, but I'm... a bit of a throwback. Look, what happens to somebody in space who's not ultra-careful about everything? Someone who isn't a detail man, someone who doesn't think checking the gear the seventh time is more important than the big picture? Someone who isn't a low-affect in-control type every day of his life?
      Harold: They die.
      Ingrid: What happens when you put a group through four hundred years of that type of selection? Plus the more adventurous types have been leaving the Sol-Belt for other systems, whenever they could, so Serpent Swarm Belters are more like the past of Sol-Belters.
  • Gone Horribly Right: The Puppeteers made the mistake of assuming that lucky humans would bring luck to their allies (such as, for example, Puppeteers) as well. As Louis points out, their luck is completely independent of the luck of their companions, and is in fact dangerous to everyone else nearby.
  • Götterdämmerung: The Norse version of the term (Ragnarok) is the title of one of the last sections of Fate of Worlds. Also, the Thrintun's final spiteful act to wipe out all life in the galaxy would qualify, seeing as they thought themselves to be living gods destined to rule the galaxy.
  • 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. This 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.
  • Handy Feet: People who grew up in space tend to be extremely slim and limber. Beowulf Shaeffer has a habit of holding his cigarettes with his toes, leaving both hands free to work as he smokes.
  • Heavy Worlder: The Jinxians are of the short Heavy Worlder 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.
  • Herbivores Are Friendly: Averted in practice — the herbivorous Puppeteers are collectively ruthless, paranoid and deceitful, while Pak protectors are xenophobic killing machines who eat nothing but tree roots — but the Kzinti are under the cultural bias that anything that isn't a carnivore is either inherently weak or stupid; "you don't need brains to sneak up on a leaf!" They've faced many nasty subversions to this expectation throughout the series; the "grass giants" on Ringworld, the hidden nastiness of Puppeteers, humanity, and so on.
  • Heroic Lineage:
    • Beowulf Shaeffer, the protagonist of the stories collected in Crashlander is the adoptive father of Louis Wu, the hero of There Is A Tide, the Ringworld series, Betrayer of Worlds, and Fate of Worlds. Shaeffer is once asked about having a hero's name and it turns out he has no idea who the original Beowulf was.
    • Carlos Gridley Wu, who features in several stories with Bey and is a super-genius with an unlimited breeding license, is the biological father of Louis Wu.
  • Hero of Another Story: When Sigmund Ausfaller first appeared in "There is a Tide" and "Flatlander", he was just a supporting character, but it was implied that he was involved in some pretty heroic things as well. Forty years later, Niven wrote a trio of novels using Ausfaller as the hero in his own right.
  • Horde of Alien Locusts: The Slaver Sunflowers. They have a reflective flower that focuses sunlight on a single green photosynthetic node. They will also focus solar energy to burn any nearby animals or plants that are not Slaver Sunflowers, and even any diseased or mutant Sunflowers, until healthy Sunflowers are the only plants in view. There are areas of the Ringworld with land areas the equivelant of hundreds of Earths completely dominated by Slaver Sunflowers.
  • Humanoid Aliens: Mostly avoided, as only the kzinti and kdatlyno qualify... and even then only technically.
  • Humanity Came from Space: Or at least, Homo habilis did, in the form of Pak breeders.
  • Humans Are Special: Orthodox Kzin society believes that Kzinti are the pinnacle of creation and fated to rule the universe. Their devastating losses in their wars against humanity seriously challenged this belief, and led to the formation of a cult known as the Kdaptists who believe that God made Man, not Kzin, in His image, and means for them to dominate the stars. This has led to some unusual practices, such as praying while wearing masks of human skin in order to trick God into thinking that the devotee is one of His human children.
  • Humans Are the Real Monsters: Which is why the Puppeteers used us to keep the Kzinti in line. Most notably, 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.%
  • Hyperspace Is a Scary Place:
    • The Blind Spot. Since hyperspace is non-Euclidean, 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 blind spot... 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 issuesnote .
    • 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, things living in hyperspace are also mentioned, although they don't turn up in any other stories.
  • I Have Your Wife: After Jason manages to escape the Kzinti in "The Soft Weapon", they try to force him to bargain by threatening to eat his wife, who remains their prisoner, on limb at a time, with medical treatment in between to make sure that she doesn't die of shock while they work her over. When they capture him, they start the process right up in front of him.
  • I Warned You: A fairly epic example in "Flatlander", where Beowulf Shaeffer delivers a full paragraph of variations on "I Told You So" to Gregory Pelton.
  • Immune to Mind Control:
    • The Bandersnatchi were created as a food source for the mind-controlling Thrintun by one of their subject races. They were also created as spies immune to the Thrintun's powers. The result was that they were pretty much the only vertebrates to survive the Slavers' mass-suicide command and are therefore the oldest sapient race in the galaxy by at least a billion years.
    • Pak protectors are also immune to Thrint control, due to their multilobed brain structure. A Thrint who thinks it's controlling one actually only gets one of the protector's five brain lobes, reducing its irresistible commands to optional suggestions.
    • Black Priest kzinti are immune to telepathy due to the same gene that gives them their eponymous fur color.
  • Improvised Weapon: The Kzinti thought their attack on humanity would result in an easy conquest of walking Happy Meals because humanity had no military and no weapons. They subsequently learned the Kzinti Lesson, that "unarmed" ships cruising around at high speeds have drives that can be turned into Weaponized Exhaust, as per Jon's Law: "Any interesting space drive is a weapon of mass destruction."
  • Inertial Damping: It is often (correctly) pointed out that the crew of a starship only has to worry about inertia when they are accelerating or decelerating. For such times, the ships use artificial gravity to reduce the effects of high acceleration (massively high acceleration in some cases; for example, at one point in the short story "Flatlander", the starship ''Slower Than Infinity" is accelerating at nearly 200 gravities).
  • Infinite Supplies: Autokitchens never run out of raw material, and work a lot like replicators from Star Trek. (They do, however, recycle it). Specifically, there's a point in Ringworld Engineers when Louis wishes that the autokitchen's recycling set-up was a bit less explicit. The toilets (one for him and one for Chmeee, the 8-foot felinoid alien) are on each side of 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. They are pretty much the only weapons used by the ARMs and organleggers because both sides want to preserve their targets intact for the organ banks.
  • 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, like the City Builders who invented the custom.
  • 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-sapient).
    • The Puppeters warped their "turn-and-kick-with-third-leg" response into Dirty Cowardice.
    • Humanity did an amazing amount of damage to themselves in this manner completely by accident. In the early 21st century, advances in organ transplant technology enabled universal transplant compatibility. Human lifespans could be greatly expanded by simply replacing a person's worn-out parts. As a result, all forms of burial save organ harvest became illegal, governments started using executed criminals for organ transplants, and Earth started Sliding Down The Slippery Slope to All Crimes Are Equal in pursuit of transplant stock. However, it turned out that criminal behavior such as violence, deception, and greed have a genetic basis that organ harvesting weeded out of the population, along with a great deal of humanity's self-preservation, self-motivation, and self-interest. After a few generations of this, "flatlanders" are pacifistic, completely obedient to authority, and rather stupid; a century later, "sane" humans can only be violent or disobedient 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 it's a justified situation, The Government then starts treating them as psychotic, because most of the time it is the result of a psychotic break. One such psychotic had to go off his meds in order to fend off the Kzinti — and ended up organ stock for his trouble. Even after synthetic transplants become available and the organ banks disappeared the damage to human genetic diversity had already been done.
  • Jaywalking Will Ruin Your Life: In the Gil "The ARM" era, running a stop sign can get you executed.
  • Kill It with Water: Niven's version of Martians have an exotic biochemistry using nitric acid as a solvent, and explode on contact with liquid water. Deeming them a potential threat to humans, the Brennan-protector wipes them out by dropping a massive ice comet on Mars.
  • 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.
    Chmeee: With such a weapon, I could boil the Earth to vapor.
    Louis Wu: Shut up.
    Chmeee: It was a natural thought, Louis...
  • La Résistance: A Zig-Zagging Trope in "A Gift From Earth". On Plateau, the Crew rule and the Colonists serve. Any crime by a Colonist results in them being butchered for organ transplants. The Crew are opposed by a dissident organization calling themselves the "Sons of Earth". Pretty standard, except the zig; the Crew keep close tabs on the organization, and whenever they need spare parts, they arrest and break up a few of them. They're husbanding them like cattle. And when they receive the titular "gift from earth" — a series of medical breakthroughs that drastically reduce the need for transplants — they kill every Son of Earth, both because the Colonists would revolt if they thought the organ banks weren't needed any more, and because they didn't need a steady supply of organs anymore. Then the zag; the last three rebels include a psychic assassin capable of vanishing from sight and memory, so they win by default and force the Crew to abdicate.
  • 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).
  • Lawyer-Friendly Cameo: When Beowulf Shaeffer meets an old-fashioned internal combustion race car driver in "Flatlander", he describes him as having shiny green hair, a bony white face, and a grinning scarlet mouth. He demurs when the racer offers him a lift, noting "this joker was obviously dangerously insane".
  • Leeroy Jenkins: The Kzinti "scream and leap" fighting style. Their tendency to attack before they're quite ready is why they lost every one of the Man-Kzin wars.
  • Longevity Treatment:
    • Boosterspice (a drug derived from genetically engineered ragweed) can tremendously extend the human lifespan.
    • Ringworld. There is an equivalent to boosterspice available on the title space construct.
    • The Ringworld sequels strongly imply that both of these are actually derived from Tree-of-Life root, which is what turns Pak (and their mutated descendants, such as humans and the various Ringworld hominids) into protectors and makes them, if not actually immortal, at least immune to death from old age.
  • Losing Your Head: Happens a few times — notably non-lethally.
    • Nessus the Puppeteer loses one of his heads to monomolecular shadow-square wire in Ringworld. 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. This is lampshaded in Louis Wu's thoughts as he's using his belt to staunch the bleeding. "You put a tourniquet around his neck, doctor?"
    • Beowulf Shaeffer gets his head chopped off in "Procustes", and survives thanks to a state-of-the-art nanotech Auto-Doc; specifically, his body is lost, so his friends put his head in the doc along with his murderer's body as biomass.
  • 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 indestructiblenote , 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). Larry Niven later notes he wished hadn't invented most of them, as they were too good, and closed off many story possibilities.
  • 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, they're given selective memory wipes too. The masquerade is eventually {broken|Masquerade}} in Fate of Worlds.
  • 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.
  • The Man Behind the Man: The Gw'oth have been puppeteering the puppeteers the whole time.
  • The Milky Way Is the Only Way: Even with the Quantum II hyperdrive (which travels a light-year every 75 seconds — 420,000 times lightspeed — enough to get to another galaxy in a decade), the Andromeda Galaxy is still centuries away because Hyperspace Is a Scary Place — long hyperspace journeys inflict psychological trauma on passengers, and the ship is instantly destroyed if it travels within several light hours of a star. Beowulf Shaeffer attempts to visit the galactic core and nearly has a stress-induced breakdown due to having to dodge stars non-stop for hours on end.
  • Mirroring Factions: Organleggers tend to treat ARM cops like this as a kind of snub; in their eyes, there's very little difference between how they and the government kill people for their organs — the ARM's official source of transplant stock is citizens executed for Felony Misdemeanors such as traffic violations, and they aren't at all shy about claiming the seized stockpiles of organleggers. Gil admits they have a point; he immigrated to Earth for a new arm, and had a serious crisis of conscience when he discovered it came from a murder victim instead of an executed murderer.
  • Multistage Teleport: The puppeteer homeworld features a network of "stepping discs" (freestanding teleport pads) in pairs spanning a block or two, placed end-to-end one pace apart. The result is a sort of seven league boot effect, allowing a traveler to circumnavigate the planet on foot in an afternoon.
  • Mundane Dogmatic: The "Belter" period, where technology isn't far off from what we have today, just more efficient and practical. Stories set after the invention of Faster-Than-Light Travel (Known Space) are significantly softer and more like traditional scifi, albeit far more self-consistent.
  • 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.
    • Communication lasers 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.
    • Ramscoops use a powerful miles-wide magnetic field to suck in hydrogen from a large area in front of a ship to power the engines. This magnetic field has catastrophic effects on anything with a nervous system that happens to be in the field when it's turned on.
    • 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 Treatymaker, a twin-beam variant of the Slaver digging tool which was used on the Kzin outpost of Warhead, carving a titanic rift in the Mars-like planet's crust, and giving it an ecosystem by causing its thin atmosphere to flow into the resulting canyon and become condensed enough to breathe; 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. They're the same nanites, in fact. The patches use modified versions of the nanites from Carlos Wu's autodoc (which is, apparently, unique).
  • 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.
  • Not Drawn to Scale: Many of the artists in various countries who paint covers for the Ringworld novels have a hard time grasping the proportions of it, though it may be for the best as a to-scale ringworld is terribly boring (if not outright impossible to see) to look at from anywhere that isn't the surface.
  • Nuclear Torch Rocket: Fusion rockets are a basic space-travel engine (most species use reactionless drives). It's noted that humans like torch engines because they double as guns. Ring World has the main character's ship equipped with torch drive retros for this very reason.
  • One World Order: The United Nations eventually becomes a true world government.
  • Organ Theft: This trope originated with Known Space. Early Known Space stories thoroughly explored the dangers of transplant technology outstripping organ synthesis, to the point where lawmakers would obsessively change laws to make all crimes into death sentences just to keep up with the demand for organs. With the price of organs being so high due to demand, it's almost inevitable that illegal organ harvesting becomes a frequent concern, enough so that the process becomes known as "organlegging", a Portmanteau of "organ" and "bootlegging".
  • Our Humans Are Different: What modern science knows as Homo habilis is in fact the reproductive stage of the Pak, an ancient alien species that, on consuming a specific root and the symbiotic microorganism within it, transforms into a sterile but immensely strong, agile and intelligent being called a protector, which is thereafter driven only by the unquestioned and single-minded urge to protect its genetic descendants at all costs. Earth was one of several worlds populated by Pak seeking to establish their bloodlines away from the endless warfare of their homeworld, but the lack of a chemical necessary for the microorganism to live caused the protectors to die off and allowed the breeders to speciate and evolve; modern human aging is the result of our bodies trying to undergo the protector transformation without the additional information given by the microorganism. Humans who eat healthy tree-of-life still transform into protectors, albeit with a high mortality rate; the physiological and mental differences between Homo habilis and Homo sapiens mean that human protectors are weaker and less agile than Pak protectors due to the transformation being imperfect, but are also more intelligent, mentally flexible and introspective, and also less dogmatically xenophobic.
  • Our Vampires Are Different: Vampires are one of the many hominid species of the Ringworld. They are non-sapient predators adapted for feeding on the blood of other hominids, and the Ringworld's civilizations universally view them as dangerous vermin.
  • 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, Thrintun are also supposed to be rather dim by human standards — an average IQ of 80.
    • 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.
    • On the Ringworld when they first see an eyestorm (a hurricane on its side, essentially) the explorers all panic and think it is God's eye. Louis is relieved when Speaker says he sees a giant human eye, but Speaker himself has a moment of thinking the Kdaptist Heresy might have been correct.
    • Nessus in Ringworld claims that Puppeteer scientists have proved that their species, at least, does not have an immortal soul that survives death. He explicitly demurs from claiming whether or not the same is true of humans or Kzin.
  • Parasites Are Evil: The puppeteers are embarrassed that they're parasitoids, requiring a livestock animal they infest with their larvae to propagate (which they insist is actually the third sex of their species). However, their extreme cowardice leads them to do such things as socially engineering their rivals on the galactic stage into ineffectuality and release metal-eating bioweapons (a type of yeast that feeds on room-temperature superconductors) into precursor ruins so that they can't ever become a threat, never mind that they could study such Lost Technology.
  • Perception Filter: "Plateau Eyes" is a psychic ability to influence the optic nerves of anyone whose attention is focused on the user. When he is excited or frightened, people focused on him are compelled to contract the pupils of their eyes, and thereby lose that focus to the point of short-term memory loss – even if he has just threatened them with a weapon. Trained users can expand the pupil, putting people in a hypnotic trance.
  • 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.
  • Planet of Hats: The Kzinti are space samurai. The Outsiders are merchants. The Puppeteers are all cowards (and secondarily merchants of a more mundane kind; Human Space is highly dependent on Puppeteer-made General Products spacecraft hulls). 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, the entire species could also be thought of as Camp Gay.
  • Planet Spaceship: The Pierson's Puppeteers have basically turned their homeworld, along with four more planets into a spaceship, and are using it to flee the explosion at the center of the galaxy.
  • Pluto Is Expendable: In World of Ptavvs, Pluto is set on fire... yes, the entire planet is set on fire... by the fusion exhaust of a spacecraft.
  • Poke in the Third Eye: Kzinti often use telepaths to inspect and interrogate prisoners. They are also carnivores who find herbivory morally and conceptually repugnant. In "The Soft Weapon", while being scanned by a telepath, the main character concentrates on the taste and texture of eating a raw carrot, "just to be difficult".
  • 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.
  • P.O.V. Sequel: Much of Juggler of Worlds is a retelling of the Beowulf Shaeffer stories from the perspectives of Sigmund Ausfaller, Nessus and Baedeker.
  • Precision F-Strike: Downplayed, Lampshaded and Played for Laughs in "Flatlander" —
    "Elephant. Have you noticed in me a tendency to use profanity for emphasis?"
    "Not really. Why?"
    "It's goddam radioactive out there."
  • Proud Hunter Race: The Kzinti are sapient predators who firmly believe that the only proper way to obtain your food is to go out and kill it yourself, and have no problems whatsoever with hunting and eating other sapient beings. They find the concept of vegetarianism morally repulsive, and their traditional way of dealing with criminals from subject species was to let them loose in fenced preserves and hunt them for sport.
  • Proud Warrior Race: The Kzinti are a civilization of highly militant imperialists who historically tended to treat "first contact" and "declaration of war" as largely synonymous. In their society, all males are expected to become part of the military and gain their names and status through martial service, and duels to the death over points of personal honor and pride are very common.
  • Psychic Starship Pilot: The Kzinti never obtained the mass indicator technology humans use to navigate hyperspace, instead relying on a few rare Kzinti who can see in hyperspace, and the Patriarch made a concerted effort to mate with their female relatives to ensure his family would control Kzinti space travel.
  • Psychoactive Powers: Psychic powers in general. Every example has enough drawbacks that in most milieus they'd be considered useless.
    • Gil Hamilton's telekinetic "imaginary arm" works this way. It's limited to the range of his real arm, because that's how he visualizes the power — except that he can reach through objects, reach into sufficiently realistic projected images, and touch and manipulate objects that appear to be within arm's reach. In "The Defenseless Dead", he gives a former kidnap victim a screaming freakout by reaching through a Holographic Terminal and picking up a pencil the former kidnap victim is so freaked out because he is actually the villain of the story, an organlegger who had used a Brain Transplant to assume his victim's identity. He freaked out because he had heard how Gil killed one of his competitors with his imaginary arm at the end of "Death by Ecstacy" and thought he might be next. Gil trains this ability further, and in "The Patchwork Girl" this enables him to search huge swaths of the lunar surface by sweeping the arm through a scaled-down high-definition hologram.
    • Julie, one of Gil's fellow ARM agents, is a telepath with planetary range... as long as she's in love with the person in question. Luckily, she Really Gets Around and can find things to love about pretty much anyone. In-between acting as a psychic therapist, she reads the thoughts of every ARM agent not in direct contact with headquarters in sequence every fifteens specifically so she can send help if one gets in trouble. Of course, in order to keep that going, every one of her "harem" has to constantly hold her in the highest regard, because if she falls out of love with them she can't read them anymore.
    • Larry Greenberg in World of Ptavvs is one of the most powerful natural human telepaths. With the help of a contact helmet he basically gets a complete copy of the memories of anyone he contacts. There's a moment of confusion each time he uses it until his personality works out which set of memories is his and which is the copy he just received. It works great until he uses it on a telepathic alien that has read thousands of other minds. Suddenly Greenberg thinks he is the alien somehow transplanted into a human body. It takes several demonstrations of how stupid Kzanol is and a bump on the head to finally allow Greenberg's personality to re-assert his control. The ending of the novel also makes it clear that Greenberg's personality picks up traits from each person he has contacted, making his final "Greenberg" personality more of a blend.
    • Matt Keller in A Gift From Earth can cause people to forget about his existence when he feels threatened or excited. This is a very useful survival ability in the tyrannical society of Plateau, where any Colonist who stands out too much tends to end up in the organ banks as transplant stock. It has the drawbacks that people he's known his whole life don't remember his name, the only job he could get was "mining worm wrangler" because it doesn't involve working with other humans who might forget he's there, and it's been impossible for him to get a date because as soon as he gets excited about a girl she forgets he exists. By the end of the book Matt learns to have more conscious control over his ability, and that he can reverse it to make someone intensely interested in him.
  • Restraining Bolt: The Protectors have been shaped by evolution to be the perfect warriors and have genetically hard-written imperatives about protecting their own descendants. In one case, a Protector-stage Louis Wu comes across a former antagonist who has become pregnant with his (Louis's) grandson. He tells her flat-out that because she's carrying his grandchild, Louis couldn't raise his hand against her no matter how she attacked him.
  • Roc Birds: The short story "Safe at Any Speed" features rocs in the form of gigantic alien birds large enough to swallow a car whole.
  • 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 sapient, 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.
  • Sequel Non-Entity: The "ship-eating monsters in hyperspace" introduced in Ringworld's Children are not mentioned at all in Fate of Worlds. The monsters were said to look like dark wriggling comma-shaped objects against the swirling colors of the Blind Spot, but none of the characters who go into hyperspace inside a singularity in Fate of Worlds see anything like that. The ability of multiple-planet-sized objects to enter hyperspace is retconned to be due to a new theory of hyperspace that Tunesmith developed and Baedeker was able to reconstruct.
  • 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.
  • 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.
    • Louis Wu's middle name, Gridley, may be a reference to Jason Gridley from Edgar Rice Burroughs' Pellucidar novels.
    • In Fate of Worlds, the puppeteer Achilles realizes his super-powerful AI Proteus is rebelling against him when Proteus says "I'm afraid I can't do that."
    • The title of the short story "Safe at Any Speed" parodies Unsafe at Any Speed, the exposé about car safety that made Ralph Nader famous.
    • "The first man to see a puppeteer had done so during a Campish revival of Time For Beany reruns." — "The Soft Weapon"
    • In Destiny's Forge, Pouncer's mother was named M'Ress, and his mate is named C'Mell. The name of the reputation-based currency used on Kzinhome, strakh, comes from Jack Vance's short story "The Moon Moth". Also see Whole-Plot Reference below.
  • 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.
    • Crashlander is a collection of the Beowulf Shaeffer short stories with a new story linking them all together. The linking story is jam-packed with retcons intended to fix problems Niven saw in the stories after the fact.
  • Sleeper Starship: 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 can do a pretty good imitation of it.
  • 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 Orcs: The Kzinti, a species of towering catlike aliens, are what you get when you take a bronze age culture and give it hyper-advanced technology with no adjustment period. Evolved from territorial predators, they had just worked out metalworking when a space-capable species, the Jotoki, culturally uplifted them to use as soldiers and bodyguards. This worked great until it didn't and the Kzinti overwhelmed the Jotoki, enslaved them and used their tech to create their own star empire. Modern Kzinti are extremely aggressive and warlike, routinely invade, conquer, enslave and eat other sapient species, have a society entirely focused upon martial prowess, and are so prone to dueling each other to the death that this serves as their main population limiter. They have however become far less vicious in the tail end of the setting's timeline, in large part because the Puppeteers contrived for humanity to gain a technological edge on them, causing the Kzinti to lose all their wars against them and cull off the most aggressive and warlike members of several consecutive generations.
  • Space Police: The Goldskins (so named because of the color of their pressure suits) who patrol the Belt for smugglers.
  • Space Romans: One short story has a literal realm of Space Romans on an on-and-off battle with local Kzin, who are also at least familiar with firearms and other advances. It's revealed that said Romans are mainly the descendants of the Vanished Legion along with their families and slaves (which help explain the social structure and very classical attire, complete with legionnaire armor). They're revealed to have been brought there by aliens believing that they would make good slaves...only of them to overrun their would-be-masters and enslave them.
  • Space Whale: The starseeds are spacegoing lifeforms that migrate from system to system. The Outsiders follow them for reasons they will only reveal for the right price.
  • 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. Louis Wu notes in Ringworld that when Nessus becomes frightened or Speaker gets angry that their speech sounds increasingly less emotional, because they no longer work as hard at adding human-sounding emotional inflections into their speech.
  • 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.
  • Success Through Insanity: In Madness Has Its Place, Jack Strather's megalomania and paranoid schizophrenia make him one of the few men left on Earth with the cojones to actually resist the invading Kzinti.
  • 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 Uplift: The Kzin were bootstrapped by another species to serve as mercenaries. Unfortunately, they then turned on and enslaved their patrons.
  • Teleportation: 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 sapient beings as prey. No other author has tried using the term "LE" in their Known Space stories.
  • Tidally Locked Planet: Jinx. The colonists live along a narrow band encompassing the prime meridian and have completely black skin from the radiation. It also has very high gravity.
  • 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 the time of Ringworld we get a main character Kzin who will sometimes look before he leaps and will forgive insults if he is outmatched. This is because all of the most aggressive and stupid Kzin have all been killed off in wars against humans over the past 500 years, and only the Kzin who were smart enough to not directly fight humans survived to breed. Think of it as 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.
      • The Man Kzin Wars reveal that the Kzinti were enslaved in their early bronze age by another species who valued their martial abilities. The Kzin rebelled and used their former master's technology to reach the stars and also to tinker with their genetic code. Essentially they wanted an army of Bronze Age heroes and their women to not be so Naggy. So the Real Men now rage and leap before they think, valuing bravery and strength over intelligence. The women were tinkered with enough to become near non-sapient over time, though there seems to have been a cultural aspect to that change as well as the genetic engineering. The Kzin found on the Ringworld are noticeably less gender dimorphic (almost just as prone to going off pop, but also arguably more intelligent overall and with less of a bias against their tendency to produce lukewarm psychics). They've had longer to adapt to wider environments with more ape-like things willing to fight back. Also... getting the odd Protector maybe getting uppity in their general direction early on during relocation might've helped a bit.
    • Literally so with the Thrintun. Once they developed their psychic mind-control powers, they lost most of the selection pressure to evolve intelligence any further. When other intelligent life discovered their world they lost the rest of that pressure, as they could get smarter slaves to think for them. When their slaves revolted they exterminated all non-Thrint sapient life in the galaxy in retaliation, not realizing before hand that they wouldn't be able to survive without their slaves.
    • From Beowulf Shaeffer's perspective, humans from Earth, AKA "Flatlanders" have so little survival instinct that the only reason they haven't gone extinct is because Earth itself is all but wrapped in rubber foam and its ecosystem has been scrubbed of every threat right down to the common cold. Gregory "Elephant" Pelton, the richest flatlander alive, goes with Shaeffer on a joyride to an unknown world simply because the Outsiders say it's the most unusual planet they know of within a reasonable travel distance. Elephant refuses to pay to learn exactly why it's so "distinctive", and once in orbit, the Made of Indestructium General Products hull of his space yacht disintegrates. He still wants to land and look around. Shaeffer puts his foot down, says, "Elephant, we have no hull" and turns the ship around. Turns out the planet is made of antimatter. At the end of the story, Elephant is thinking of going back and dropping a flag on it. From a "safe" distance. To watch what happens.
  • Too Many Halves: From Destiny's Forge:
    Tskombe: Half a sense of adventure, half a sense of duty, half no better plan for my life.
    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. In the short story "The Soft Weapon", once they find out that Jason Papandreou knows the secret of the weapon, the Kzin decide to eat his wife Anne-Marie's arm — possibly both of her arms — in front of them in order to get him to tell. She loses one arm, but the Kzin are killed by the weapon's self-destruct setting before they eat it. And she gets her arm re-grown once they get back to civilization.
      Slaverstudent: It will be good to taste fresh meat again.
      Flyer: Chuft-Captain, the kitchen is programmed.
    • It's illegal (at least in Human-controlled space) for replicators to make human blood for food purposes, but they're capable of it.
  • Transplanted Humans: The various hominid species of the Ringworld. The initial Pak breeders mutated over three 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 Ringworld's continent-sized "garden maps" in the middle of oceans hundreds of thousands of miles wide, there wasn't so much as an insect that will harm humanoids present, until hominids (and in some cases, other originally harmless species) evolved to fill the role.
  • United Nations Is a Superpower: 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, which becomes a Sequel Hook for Fate of Worlds.)
  • Warrior Poet: The Kdatlyno are an entire species of these. At least one of them is also very good at sculpture; a museum on Jinx has several of his sculptures, which are designed to be felt (well, sensed with radar, but humans don't have that sense, so...). A Puppeteer suggests a human try licking them, as his tongue is probably more sensitive than his fingertips.
  • 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 Treatymaker, a massive Disintegrator Ray, pretty much single-handedly ended the Fourth Man-Kzinti War.
    • In "Down in Flames", 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." "Madness Has Its Place" makes it clear that at least the paranoids of ARM have been fully aware of the dual-purpose nature of these devices for some time.
    • "The Warriors" brings us the Angel's Pencil, a human slower than light starship, with a main drive that doubles as an interstellar comunication 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. It uses a goddamn star as an x-ray laser. 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:
    • By Beowulf Shaeffer's time, humans have developed a drug called boosterspice that has made death by old age a thing of the past. It was derived from the Pak Tree-of-Life
    • 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, human society had developed to the point that there was no war, very little crime, and no purpose-built weapons. Humanity climbed out of its complacent cocoon pretty damned quickly once the warcats showed up, however... The Protector-stage-human Jack Brenner was largely responsible for this transformation, but he had to leave Known Space to go fight the Pak invasion fleet.
  • Weird Beard: The asymmetrical beards of upper-class Wunderlanders. "Captain Kidd" in Relic of the Empire finds out the hard way that you do not mock a Wunderlander's beard.
  • 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 Ringworld and finding that more interesting. Among other thins, he had planned for the Tnuctipun to be the ancestors of, and physically identical to, the Kzinti, and to have fabricated both the Thrintun and the galactic core collapse — their grand plan was to trick the mid-galactic civilizations into panicking and fleeing so that they could take over their worlds and then board their ships and eat their crews as they fled.
  • World Shapes: Jinx, a planet-sized moon of a gas giant, is pulled into a pronounced oval shape by the gravitational stresses of the larger body. Its equatorial region band is extremely hot and too dense to breathe, while its eastern and western poles project clear out of its atmosphere — from the perspective of someone on the moon's surface, they're partway between geographic poles and impossibly tall mountains. Humans live in the transitional areas between the vacuum and the high-density belt; the equator is inhabited by a species of gigantic sluglike aliens.
  • Whole-Plot Reference: Paul Chafe's Man-Kzin Wars novel Destiny's Forge is basically a retelling of Dune, with Pouncer, First-Son of Patriarch Meerz-Rrit, as Paul Atreides, Tzaatz Pride as House Harkonnen, the czrav, low-tech jungle-dwelling kzinti, as the Fremen, the elephant-like tuskvor as the sandworms, and sthondat lymph as the Water of Life.
  • Xenophobic Herbivore: Puppeteers are thought to have engaged in genocide a few times and they're scared enough of other sapient races to keep their homeworlds' location a secret. Being brave enough to dialogue with other species is considered a sign of insanity.
  • Zero-G Spot: Zero-g sex is far from uncommon, due to zero-g "sleep fields" which work anywhere. The complications involved in having sex in the Moon's low gravity are also touched on in The Patchwork Girl.

Alternative Title(s): Man Kzin Wars, The Soft Weapon, Destroyer Of Worlds, The Patchwork Girl, Fleet Of Worlds, World Of Ptavvs, A Gift From Earth, Cloak Of Anarchy, The Ethics Of Madness, Becalmed In Hell, Inconstant Star, Destinys Forge, The Woman In Del Rey Crater, Madness Has Its Place, Safe At Any Speed, Wait It Out, A Relic Of The Empire, Juggler Of Worlds, Fate Of Worlds, Bordered In Black