When Louis Wu tired of human company, he took a vacation or "sabbatical" for several months or more, exploring alone in his starship yacht beyond the fringes of Known Space. On these vacations, including one in 2830, he read, listened to music, and looked for Slaver stasis boxes.
Reference: "There Is a Tide", Ringworld ch. 14
A ramscoop with a "dead pocket" or bubble in its otherwise deadly magnetic field. A starship was placed in the bubble, making a manned ramscoop ship possible. Early Human attempts to build a safe ramscoop, including the Long Pass and apparently including the Lazy Eight II, were deemed failures. A reliable technology was finally developed in 2320, when Moscow Motors, in a UN financed project, built their first safe ramscoop field generator. Using this device, Skyhook Enterprises in 2322 built the first in a long line of successful manned ramscoop starships. Hyperdrive made the ramscoop obsolete in 2411.
Reference: "The Ethics of Madness", "The Warriors"
In 2850, the southern end of a single sprawling city on the west coast of North America, on Earth, with San Francisco at the northern end.
Reference:Ringworld ch. 1
In 2850, the northern end of a single sprawling city on the west coast of North America, on Earth, with San Diego at the southern end.
The material of the Ringworld's foundation and rim walls, and apparently the shadow square wire. It is an artificial material, translucent gray and almost frictionless. Far stronger than any normal material, it has a tensile strength approximately equal to the strong nuclear force. It appears to be a superconductor of heat.
(b) A series of busts and statuettes by the Kdatlyno artist Lloobee, displayed in the Art Section of the Institute of Knowledge on Jinx in 2649. There were three groups in the series, all inspired by Lloobee's trip to Gummidgy in 2647, during which he was kidnapped. The first group portrayed passengers on the starship Argos; the second, his rescuers Beowulf Shaeffer and Emil Horne; the third revealed the identities of his kidnappers.
The events described in the account published as The Ringworld Engineers. [Spoiler alert: The Ringworld Engineers] In this account, Hindmost takes Louis Wu and Chmeee (nee Speaker-To-Animals) back to the Ringworld for further exploration of the mega-structure.
Reference:Ringworld Engineers (throughout)
A Ringworld native of undetermined species, whose facial features greatly resembled the wire sculpture of Zrillir, with a noble brow and no facial hair. He was tall, heavily muscled, with long, ash blond hair. He wore an animal skin around his waist. He was an able warrior, and carried a black metal sword. He found Teela Brown after her flycycle lost power in Hotrufan City, during the First Ringworld Expedition in 2851. They became lovers, and he accompanied her thereafter. Not overly bright, he had vowed to walk to the base of the Arch. According to Teela, he had once gotten a massive dose of something like boosterspice from an "evil magician", was hundreds of years old, and according to Teela knew "a few simple skills" including how to fly an aircar. See also maroon dart.
A robot serving the function of a butler, at Louis Wu's mansion, on Earth in 2850.
Reference:Ringworld ch. 3
shadow square wire
Almost invisibly thin wire which holds the shadow squares together. It can be reeled in to join the shadow squares, or unreeled to let them drift apart. Far stronger than any normal material, it is apparently made of scrith. Like a variable-sword, it is capable of cutting through nearly anything with very little resistance. The length of a wire was estimated at five million miles. [Spoiler alert: Ringworld] During the First Ringworld Expedition in 2851, the starship Lying Bastard (Liar) hit one of the wires when approaching the shadow squares. The wire was torn loose and drifted along with the Liar, to later hit the Ringworld floor. Speaker-To-Animals did a spacewalk to investigate the wire, finding it cut through his grippy with little resistance. After crashing on the Ringworld, the expedition encountered it falling slowly past the floating buildingHeaven, onto Zrillir City below. Even later it was seen as a tangled mass draped across the cityscape like a gray cloud. Trying to cut it with the Puppeteer disintegrator produced a string of colored lights within the wire. Speaker found one end of the wire, where a top-shaped object tapered down to the wire itself. The end was later anchored to the flying building Improbable, which towed it to the crashed Liar, where it was attached inside and used as a tow line to haul the spaceship to the peak of Fist-of-God Mountain.
A series of 20 enormous flat regularly spaced black rectangles, "orbiting" relatively close around the Ringworld's sun, block the sunlight at regular intervals, providing a day/night cycle for the Ringworld floor. Their size is approximately 1 million x 2.6 million miles (1.6 million x 4.18 million kilometers). The shadow square system actually spins at greater than orbital speed; the rectangles are held together with shadow square wires, and are gently curved to follow the "orbit". Their color is "blacker than black", the color used in blackbody experiments. Power is generated on the squares by thermoelectricty, and beamed to the Ringworld for distribution in a ubiquitous beamed power system.
Human male Crashlander, by 2641 former chief pilot for the bankrupt interstellar Nakamura Lines. Seven feet tall, weight about 160 pounds, with the albino white hair and blood-red eyes normal for Crashlanders. Beowulf (Bey) enjoyed high living and playing tourist, and was a fairly amoral spendthrift. He was said to be too lazy to stay out of trouble, but bright enough to think his way out once he was in it interstitial notes, Tales of Known Space, p. 154. He was hired by Puppeteers in 2641 to perform a flyby survey of the neutron star BVS-1; see "Neutron Star" (story summary). They hired him again in 2645 to pilot an exploratory mission to the galactic core; see "At the Core" (story summary). Later that year he joined Gregory Pelton in investigating the most unusual planet in Known Space; see "Flatlander" (story summary). On Earth during this time he met his true love, Sharrol Janss. They decided to marry and raise children. They arranged for Carlos Wu to father Sharrol's children, since Bey was not entitled to do so. So Bey played tourist again. On Gummidgy in 2647, he very reluctantly helped Emil Horne investigate the disappearance of Lloobee, a Kdatlyno artist, who later honored him in a famous heroic sculpture. See "Grendel" (story summary). By 2651, Sharrol had borne two children. As a prospective father, Bey became more responsible. While returning to Earth to join her, Bey volunteered to help Carlos and Sigmund Ausfaller investigate the disappearance of starships in Sol System; see the account published as "The Borderland of Sol".
Circulatory shock, a normal Human response to injury or trauma, is not experienced by Kzinti. In 2851 Speaker-To-Animals said it took centuries of study to understand why Humans died so easily under torture.
A spaceship crewed by just one person. Belters commonly use them, and in 2850 Louis Wu's starship was a singleship.
Reference:Ringworld chs. 1, 12
"Curved" space near a large mass, a gravity well, creates a singularity in hyperspace.
Hyperdrive and hyperwave communication cannot operate inside the gravitational singularity, or gravity well, which surrounds every star, and every planet of Mars size and up. For more information, see "Hyperspace Theory & Practice" in the Articles section.
Reference: "The Borderland of Sol", Ringworld ch. 5
A binary star system located 8.7 light-years from Sol System. Sirius A is a very bright, blue-white A1V star, of 2.1 solar masses. Sirius B is a hot white dwarf of about 0.55 solar mass, orbiting at a distance of 20 AU. According to an unofficial source, the gas giant Binary orbits Sirius A at 4.3 AU Ringworld Roleplaying Game— Explorer Book p. 39. Jinx, a Human colony world, is a moon of Binary.
Reference:World of Ptavvs p. 50
The original colony settlement and capital of Jinx, located on the Eastern Continent 3000 miles from the ocean. By 2106 it had a population of nearly 200.
Reference:World of Ptavvs p. 51
In 2645 Beowulf Shaeffer thought Flatlanders used these to dye skin and color hair, in a manner similar to but much more sophisticated than the tannin pills he took to darken his skin. But it may be that he mistook the application of body paints for the effect of pills. In either case, the skin color fashions of Flatlanders showed an amazing variety of colors and patterns, including plaids. See also "joker".
The starship which, in 2641, Beowulf Shaeffer (Bey) used to perform a flyby survey of the neutron star BVS-1. Constructed to Bey's specifications, it had a #2 General Products hull, an oversized fusion drive capable of 30 gees, and a powerful laser cannon. Bey naively believed such a heavily armed, invulnerable starship was unique in the era. (As a counterexample, see Hobo Kelly.) [Spoiler alert: "Neutron Star"] Bey actually planned to steal the ship and sell it on the black market, but was foiled when Sigmund Ausfaller told him a bomb was hidden aboard which would destroy the ship if Bey stole it.
Reference: "Neutron Star"
The first safe ramscoop starship was built by this company in 2322, under the leadership of Douglas Hooker and Greg Loeffler. Headquartered in Kansas City on Earth, it built many of the ships used during the First Man-Kzin War. Hyperdrive technology made the ramscoop obsolete, and Skyhook Enterprises went bankrupt before the Second Man-Kzin War "Canon for the Man-Kzin Wars", Scatterbrain pb p. 294.
Reference: "The Ethics of Madness"
Each flycycle used by the First Ringworld Expedition in 2850-51 had a remote control "slave circuit" which, when activated, caused that flycyle to exactly duplicate the movements of another.
This device emits a beam which suppresses the electron's charge. In the cone of the beam, the electron becomes a neutral particle, causing the proton's charge to tear matter apart into dust. It is most effective as a digging tool, or a weapon used against structures. The most common type of disintegrator is a hand-held, rifle-like projector, but larger and more powerful projectors are certainly possible (see Wunderland Treatymaker). In operation, used to dig a hole or a tunnel, the disintegrated material blows out and past the user in a minor hurricane of monatomic dust, dense enough to block vision. Although it can cause severe wounds when used on a living being, it takes too long to kill to be considered an effective weapon. The device was first encountered by Humans in 2106 as an artifact from the Slaver Empire.
Reference:World of Ptavvs, "Grendel", Ringworld ch. 15
The ancient empire of the Thrintun, also called "Slavers", who ruled most of the galaxy 1.5 billion years ago. With their powerful telepathic mind-control Power, they ruled a number of slave races. These included the brilliant and inventive Tnuctipun, whose eventual revolt brought an end to the Empire in the Tnuctipun-Slaver war. Relics of the Slaver Empire include Slaver stasis boxes and their contents. Biological survivors include air plants, Bandersnatchi, stage trees and sunflowers. Most or all of these were products of Tnuctipun science.
Reference:World of Ptavvs, "A Relic of the Empire", "The Handicapped", "The Soft Weapon"
Slaver stasis box
A usually box-shaped container protected by a stasis field, perfectly preserving its contents indefinitely. Slaver stasis boxes are rare relics of the Slaver Empire, which perished in the Tnuctipun-Slaver war 1.5 billion years ago. The boxes may contain anything from the era, and often contain weapons, such as the variable-sword. Records have also been found. One held a small, tarsier-like sentient being, still alive. In 2830, no box as large as 10 feet across had ever been found.
Reference: "A Relic of the Empire", "The Soft Weapon", "There Is a Tide"
Plants, each of which has a large flower with a mirrored surface, which can focus sunlight either on a photosynthetic node, or on anything within view which is moving. Apparently they can see movement about as far away as can the Human eye. One sunflower isn't dangerous, but a large patch can be deadly. Where Slaver sunflowers flourish, nothing else lives. If not stopped by any natural barrier, a patch will slowly spread to cover all available land. Sunflowers kill anything that moves, and burn out all other plants, even any of their own species which become diseased. Anything that is killed becomes fertilizer for the sunflowers. Probably a product of Tnuctipun biological engineering, they were planted on Slaver Empire estates as a defensive measure. A variety which appears on the Ringworld stands a foot high on a knobbly green stalk. Its single blossom is as big as a large man's face; the back is stringy, as if laced with tendons; the front is a smooth concave mirror. From its center protrudes a short green stalk ending in a dark green bulb. During the First Ringworld Expedition's first encounter with Slaver sunflowers in 2851, Speaker-To-Animals was severely burnt over much of his body, and temporarily blinded. There is also documentation of a "tiny cold-world sunflower" "The tnuctipun had left mutated remnants of their biological engineering: ...the tiny cold-world sunflower, with its rippling reflective blossoms" ("The Soft Weapon", Neutron Star p. 83)., but this apparently refers to a mutated form.
Reference: "The Handicapped", "The Soft Weapon", Ringworld chs. 14, 23
Originally known as a "Russian sleep machine", or "electrosleep" device. Two electrodes are taped to the subject's eyelids and one to the nape of the neck, enabling a gentle electric current to be run through the brain. An hour of sleep under such a device provides a full night's rest.
(also called sleeper field) An application of artificial gravity used by Humans in place of a bed, in common use by 2648. It causes the user to float in air, and is more comfortable than a bed because there is no pressure against any part of the body. It is not quite a null-gee field; a slight pull to the center keeps the user from drifting out. The field can typically be set for two separate "sleeping nodes", for two people, or to join them into one. Halrloprillalar Hotrufan became enthusiastic when introduced to sleeping plates, but did not use them for sleeping.
Reference: "Grendel", Ringworld chs. 4, 24
A sidewalk which moves like a conveyor belt. In all the cities of Earth in 2850, slidewalks moved at 10 miles per hour. In Beirut, they were turned off at night. See also pedwalk.
Slower-than-light starships transporting settlers from Earth to Human colony worlds in the age before hyperdrive, starting sometime in the 21st century. Originally they were powered by fusion drive. Unlike ramscoop starships, they had to carry their own fuel, so traveled at less than half lightspeed "Men must ride the slowboats, carrying their own fuel, moving at less than half the speed of light" (A Gift from Earth ch. 1, p. 12)., or a quarter lightspeed "For centuries men had followed [the ramrobots] at a quarter of the speed of light, carrying their own fuel" ("The Ethics of Madness", Neutron Star p. 179)., and spent most of the voyage coasting. Beginning circa 2355, they used safe ramscoop propulsion. The early ramrobots were mis-programmed; finding a habitable point, they signaled discovery of a habitable world. Slowboat voyages were one-way trips, so colonists following these erroneous signals were forced to settle on the marginally habitable worlds of Jinx, Plateau, We Made It, and probably Down. Hyperdrive made the slowboats obsolete in 2411.
Reference:A Gift from Earth, "The Ethics of Madness", "Flatlander"
Chart of inner Sol System, showing the Belt (main asteroid belt) and the Trojan asteroids
Picture credit: Wikipedia (public domain)
The stellar system containing Earth; Sol is Earth's sun. By 2651 twelve major planets were recognized, as well as the main asteroid Belt. In order outward from the sun, it is comprised of Mercury, Venus, Earth, Mars, the Belt, Jupiter, Saturn, Uranus, Neptune, Persephone, Caïna, Antenora, Ptolemea, and the cometary halo. It also contains Pluto, a loose moon of Neptune.
The force field protecting the operator of a Puppeteer-built flycycle. When the accelerating flycycle approached the sound barrier, there was an increasing rushing sound, which disappeared when the flycycle reached sonic speed and the field changed shape. An object or person falling within the field would be caught, suspended by the bottom part of the field. The sonic fold had a built-in standing-wave property, so that if its power failed, it died away only gradually.
Reference:Ringworld chs. 11-12, 22
[Spoiler alert: "The Ethics of Madness"] On Plateau in 2379, authorities were able to cause a radio to emit a "loud and terrible sound" which hypnotized Douglas Hooker following his use of a fusion drive to attack a house there. Note the term "sonic hypnosis" does not appear in any account, and is used here for convenience.
Reference: "The Ethics of Madness"
A non-lethal weapon which renders the victim numb and paralyzed, in use by 2341. It affects only the part(s) of the body it hits; if the victim's head is affected he is knocked out, for as much as 12 hours or more if used at full power. It uses sound waves, so is useless in a vacuum. Jinxians use them for dueling. "Captain Kidd" and his pirates used a stunner on Dr. Richard Schultz-Mann in 2644; Emil Horne used dueling stunners in 2647; the Kzinti of the Traitor's Claw used sonic stunners in 2657. The Jinxian duelling stunners carried by the First Ringworld Expedition in 2851 fired a 10-second charge, or an hour's charge if a safety button was pressed.
Reference: "A Relic of the Empire", "Grendel", "The Soft Weapon", Ringworld ch. 10
Circa 2366, the starship Angel's Pencil with its photon drive (light-pressure drive) accelerated at a mere 0.05 gee, although the Kzinti Empire warship Tracker was observed making 200 gees when matching courses, using a gravity planer. In 2648, the passenger starship Argos accelerated at five gees with its fusion drive"From breakout it had taken us ten hours to reach Gummidgy. That was at five-gee acceleration, fusion drive and gravity drag, with four gees compensated by the internal gee-field" ("Grendel", Neutron Star p. 249)., and interstellar pilot Beowulf Shaeffer claimed the fastest ships could do 20 gees "Now, the fastest ship I ever heard of could make twenty gees..." ("Grendel", Neutron Star p. 250).. But perhaps that referred only to civilian ships, for in 2650 he found the Hobo Kelly, a disguised warship, could do thirty gees "The Hobo Kelly is deceptive. It seems to be a cargo and passenger ship, but it is a warship, armed and capable of thirty gees acceleration" ("The Borderland of Sol", Tales of Known Space p. 159).. By 2830, fusion drive had largely been replaced by the reactionless thruster, although was still used as a weapon. Thrusters were safer and more efficient, perhaps leading to a somewhat faster average; in 2830, Louis Wu's personal starship could make slightly over 20 gees "Twenty gees was close to his ship's limit" ("There Is a Tide", Tales of Known Space p. 208).. Many types of space propulsion are documented (as listed below), including the superluminal (faster-than-light) hyperdrive.
Reference: "The Ethics of Madness", "The Warriors", "Neutron Star", "A Relic of the Empire", "At the Core", "Flatlander", "Grendel", "The Soft Weapon", "There Is a Tide", Ringworld
spacecraft deceleration rings
A linear accelerator used on the Ringworld to slow incoming ramships for landing at a Ringworld spaceport. The linear accelerator appeared as a row of upright rings 50 miles across, with one such installation adjacent to each of the six spaceports.
A male Kzin with black markings around his eyes and tattooed ears. He spoke excellent Interworld, despite having a mouth not shaped for Human speech. He had been raised a Kdaptist. He was an apprentice diplomat, part of the Kzinti Empire's embassy on Earth, and of a low-status family. He had been angered when Nessus asked him to introduce himself, and his self-description as a "speaker to animals" was a deliberate insult to Humans. Aboard the starship Lying Bastard (Liar), his cabin was decorated with holoscapes of orange-yellow jungle and ancient alien fortress, and cabin gravity set slightly higher than one gee. He was unaffected by hyperspace blind-spot, and when piloting the Liar left its hull transparent.
First Ringworld Expedition: Speaker was hired as an explorer for the First Ringworld Expedition in 2850. He was the expedition’s military leader, assuming command when the group was endangered or entering a potential combat situation. With typical Kzinti aggression, he used this position to assert leadership as frequently as possible, and repeatedly disputed Nessus' decisions. He was badly burned and temporarily blinded by Slaver Sunflowers, although recovered after treatment with medical foam. Speaker became enraged at Nessus over several revelations during the expedition, especially how Puppeteers had interfered in the First Man-Kzin War, using Humans to reverse the expansion of the Kzinti Empire and breed the Kzinti to be less aggressive. But by the end of the expedition he had come to realize that Kzinti expansion was ultimately self-defeating, and decided to keep his knowledge about Puppeteer manipulations to himself. For more information on the expedition, see Ringworld (story summary).
A species of plant genetically engineered to be a solid-fuel rocket. It is a survivor from the Slaver Empire, probably a product of Tnuctipun genetic engineering. Dr. Richard Schultz-Mann studied stage trees on Mira Ceti-T in 2644. [Spoiler alert: "A Relic of the Empire"] Stage trees have two life cycles. The smaller, called "stage bush", grows as a miniature tree, four to six feet tall, slender and straight. The top is brilliant yellow foliage spread like a dandelion head. If ignited, a ripe bush rises high into the air, where the head bursts like a fireworks display, scattering seeds. The other life cycle, a much larger form, grows only in an especially fertile patch of ground. It is a multi-stage rocket a half-mile high, with a granite-like covering and an egg-shaped knob at the top 15 feet across. The overall shape resembles an asparagus spear. The base of the plant, composed of a dense woolly, yellow moss-like vegetation, spreads in a circle 300 feet across. If launched naturally, the final stage usually reaches escape velocity for the local star system. When the seed pod reaches another star system it explodes, scattering seeds, one or more of which may reach a habitable world. The Thrintun grew them on plantations, and used the solid-fuel rocket cores to lift their ships where using fusion rockets would have been dangerous.
Reference: "A Relic of the Empire"
By 2641 the star had become the standard unit of currency in Human Space, replacing the earlier UNmark. A one-tenth (1/10) star stamp was sufficient to mail a wallet. A half-star was the price of a disposable book tape"Write a book and make a fortune! ...human space contained nearly fifty billion readers. Persuade one percent of them to shell out half a star each for a disposable tape..." ("A Relic of the Empire", Neutron Star p. 45) or a transfer booth fee. Half-star coins were in circulation in 2645, and ten-star coins in 2647.
Reference: "Neutron Star", "A Relic of the Empire", "At the Core", "Flatlander", "Grendel", "The Soft Weapon"
On the Ringworld, the direction of right when facing spinward. By analogy with directions on a normal planet, where the day/night terminator moves from east to west, starboard is north.
Reference:Ringworld ch. 10
Starseeds are enormous, non-sapient creatures which travel in interstellar space, swarm in the galactic core, propelled by light-sail. Their metabolism is powered by a nuclear solar-phoenix reaction; their food is the thin interstellar hydrogen gas. Their motive power is an enormous, highly reflective light sail, controlled like a skydiver's parachute. They travel at about 80% lightspeed, commonly migrating to the galactic core to mate, then about 50,000 lightyears to the galactic rim to lay eggs. The hatched starseed chick must find its own way home, riding the photon wind, to the warm, hydrogen-rich core. It is believed some of the eggs are launched outward, traveling to other galaxies. A starseed spends most of its time folded into a compact egg shape. When it needs to maneuver, it unfurls its light-sail, thousands of miles across. A cross-shaped thickening in the sail is the living body of the starseed. Four thread-like shrouds, controlled by muscles and used to orient and control the sail, extend to a tiny knob which is also living matter. A furled specimen observed in 2647 was over a mile thick, a mile and a half long. Outsider ships follow the migrations of starseeds. The reason is unknown, but it has been speculated that the Outsiders have some sort of symbiotic relationship with starseeds, or are biologically dependent on them.
Reference: "Flatlander", "Grendel", Juggler of Worlds, Ringworld ch. 13
A Puppeteer device which causes a star to emit electromagnetic signals which attract starseeds. In 2851, Nessus called it a "simple device" which had been invented millennia earlier. [Spoiler alert: Ringworld] Puppeteers intervened in the First Man-Kzin War by using a starseed lure to guide Outsiders, which follow starseeds, to make contact with We Made It, in 2409, ensuring Humans would gain hyperdrive technology.
A field inside which time stands almost perfectly still. This technology is from the ancient Slaver Empire, probably a product of Tnuctipun science. The surface of a stasis field is one hundred percent reflective, a perfect mirror. Nothing outside a stasis field can affect anything inside, and vice versa. The stasis field and its contents can be moved or accelerated as a whole; anything inside moves as if encased in glass. The stasis field provides perfect protection against almost every danger, including all known weapons, explosions, and collisions. The field itself is carried by a conductive surface, such as a metal mesh, a solid metal box, or a transparent conductive coating on the inside surface of a General Products hull. A stasis field is also described as a time-retarder field. It does not completely stop time, so can be set to shut off after a certain interval. Since one such field cannot exist inside another, a stasis field can be shut down prematurely by putting it inside a larger stasis field. Although Humans had a working example of the technology as early as 2106, a relic of the Slaver Empire, they apparently still could not produce reliable stasis fields as late as 2850, possibly due to technology suppression by the ARM. The Puppeteers could build reliable stasis fields by 2650, and likely much earlier.
A sophisticated transportation system on Hearth, using transfer booth technology. A cluster of four blue discs were mounted in the ground at every street intersection, forming a network of open transfer "booths". In practice, one could follow a line of stepping discs, jumping a block with every three steps. Other stepping "discs" were used for longer transit distances; a brown pentagram took the First Ringworld Expedition explorers to the starship Lying Bastard in 2850.
The drug used to temporarily increase the psionic ability, or latent ability, of a Kzin telepath to full potential. It makes 999 out of every 1000 Kzinti it is used on insane, and the thousandth becomes a shivering neurotic.
Reference: "The Soft Weapon"
stock market crash
The following stock market crashes are mentioned:
(a) A crash wiped out Richard Schultz-Mann's fortune. The date is unknown, but it was prior to 2624.
(b) [Spoiler alert: "At the Core"] The Puppeteer migration in 2645 started a huge crash throughout human space, starting with spacecraft manufacturing companies dependent on General Products hulls which were no longer being manufactured.
Reference: (a) "A Relic of the Empire", (b) "At the Core"
A catastrophe known as the Fall of Cities occurred on the Ringworld in 1733 A.D. In this disaster the City Builder cities fell, literally so for the floating cities. The cause was a plague which destroyed the room-temperature superconductors which the City Builders used in their sophisticated machines, including the magnetic repellers levitating the floating buildings. According to the crew of the Pioneer, a City Builder ramship, the cause was a mold newly evolved on one of the City Builder colony worlds, carried to the Ringworld by a trade ship; a mold which grew slowly, and thus the plague was spread widely before the danger was recognized. [Spoiler alert: The Ringworld Engineers] However, during the Second Ringworld Expedition it was revealed the plague was actually caused by a genetically engineered bacteria, deliberately introduced by the Puppeteers to wreck the advanced and powerful City Builder civilization.
Reference:Ringworld ch. 21
The Kzinti know two formulations for room-temperature superconductors. The Puppeteers know four.
(also called meteor defense laser and x-ray laser) [Spoiler alert: Ringworld] The Ringworld system's laser superweapon, which vaporized the delta wing of the Lying Bastard during the First Ringworld Expedition in 2851. The ship was attacked three times by the laser: First, when its course changed from intersecting the sun to intersecting the Ringworld; second, when it approached the shadow square wire; and third, as it approached crashing to the Ring floor. Louis Wu surmised the laser was emitted from the shadow squares, and that its primary purpose was to defend the Ringworld from meteor impacts. Ringworld's great rotational speed, 770 miles per second, makes it highly susceptible to damage from large meteors. In the account of the First Ringworld Expedition (published as Ringworld), the superthermal laser was called the meteor defense laser; or, following Speaker-To-Animals' term, the x-ray laser. [Spoiler alert: The Ringworld Engineers] The Second Ringworld Expedition discovered that the laser was actually emitted from the Ringworld's sun. To create the laser, the superconductor grid in the Ringworld foundation manipulates the sun's magnetic field, causing it to emit a solar flare which unnaturally extends straight out from the sun. The gas in the protrusion is then excited to create a gas laser of almost inconceivable power, estimated at more than 1027 ergs/second. (By comparison, the amount of sunlight falling on the entire Earth is only 1.77 x 1024 ergs/second.)
Reference:Ringworld chs. 9-10, 15, 21-22, The Ringworld Engineers, The Ringworld Throne, Ringworld's Children