[Spoiler alert: Ringworld, Ringworld Engineers]
An artifact bigger than worlds; a hoop-shaped megastructure encircling a star 201 light-years from
Sol System. The Ringworld's structure, composed of
scrith, is a ribbon a million miles wide, with a diameter about equal to
Earth’s orbit; it rotates fast enough to provide Earth-like spin-induced gravity.
The Ringworld’s inside surface holds an Earth-like habitat inhabited by vastly more sentient beings than all the other worlds of
Known Space combined. The floor is sculpted, shaped to resemble a
normal world’s terrain, with mountains, valleys, seas, rivers, an Earth-like atmosphere, and a living biosphere. The underside of
the Ring floor shows the reverse of these shapes, and is protected from meteorite impacts by a layer of foamed
scrith. A day/night cycle is provided by a ring of
shadow squares in closer orbit around its sun. The Ringworld is
protected by the superthermal laser. The
protector Proserpina claimed the structure was built about a million years
ago by an alliance of
Pak protectors who disassembled a super-Jovian planet for raw materials; however,
this claim is unconfirmed. More recently, until 1733 A.D. much of the Ringworld was controlled by the
City Builders, who reportedly colonized several planets in nearby stellar
systems. The Ringworld was explored by the
First Ringworld Expedition and the
Second Ringworld Expedition.
The animated sequence begins by looking down on the full-scale Map of Earth in the Great Oval Ocean, then pulls back to show the entire Ringworld.
Video by Simon Terrey, courtesy of Three Dimensional Cube.
From interstellar space, the Ringworld appears as an inch-wide ribbon 50 feet long, shaped into a large hoop around a candle flame; the inside surface appears as
strips of baby blue separated by shorter strips of darkness. But the Ringworld was built on a scale to shrink planets to insignificance: The flame is a sun and the
ribbon is a million miles wide, with a diameter the size of Earth’s orbit around its sun. It has an Earth-like habitat on the
inside of the hoop; soil, water and air, with rim walls a thousand miles high along the edges of the
ribbon to hold in the atmosphere. It spins fast enough to provide artificial Earth-like gravity. A day/night cycle is provided by a set of huge black flat rectangles
(shadow squares) in a closer "orbit" around the star, blocking light across the ring at regular
intervals. Superlatives fail to properly describe the Ringworld. To call it "unimaginably enormous" is pitifully inadequate to describe an object with the surface area
of three million Earths. Merely to journey from one side of the ring to the other, from rim wall to rim wall, would be a distance equal to circling the Earth 40 times;
and to journey completely around the ring would be 600 times that distance. It is home to an estimated 30 trillion hominids
The Ringworld Engineers ch. 30, p. 309, including an estimated 1000 hominid species
The Ringworld Engineers ch. 26, p. 263
Note: Despite some numbers having what appear to be three or four
significant digits, it should be noted that the given numbers have a margin of error up to about 4%.
Mass: 2 x 1030 grams (approx. 318 Earth masses, or 1.05 Jupiter masses)
The Ringworld Engineers "Ringworld Parameters", p. 355
Radius: 95 million miles (153 million kilometers; 1.02 AU (Astronomical Units))
Circumference: 597 million miles (960.8 million kilometers)ibid
Width: 997,000 miles (1,605,000 kilometers; 125.8 Earth diameters)
Surface area: 6 x 1014 square miles (1.6 x 1015 square kilometers;
approximately 3 million times the surface area of the Earth) ibid
Rim walls: about 1000 miles (1600 kilometers) high, rising sunward ibid;
about 200 feet wide at the top A passage in The Ringworld Throne describes a
maglev transport system built on top of the rim wall, "around two hundred feet across" (The Ringworld Throne
ch. 15, hc pp. 358, 361, 394).
Rotation speed: 770 miles per second (1240 kilometers per second)
The Ringworld Engineers: "Ringworld Parameters", p. 355
Rotation period: 7.5 Ringworld days (of 30 hours, or 9.375 24-hour days)
Spin-induced gravity: 31.9 feet/second/second (9.72 meters/second/second)
= 0.992 gee (1 gee = Earth’s gravity) This figure was first given as 31 ft/sec2
(The Ringworld Engineers: "Ringworld Parameters", p. 355), and later as 31.7 ft/sec2
(The Ringworld Throne: "Ringworld Parameters", hc p. 420). But the gravity field of our Earth is
about 31.9 ft/sec2. Ye Editor has therefore chosen to presume the Earth of Known Space has the same gravity, and
treat both "31" and "31.7" as copying or editing errors.
Number: 20 Ringworld ch. 6, pp. 78-79
Dimensions: Rectangular, nearly 1 million x approx. 2.5 million miles (nearly 1.6 million x approx. 4 million kilometers)
Ringworld ch. 9, p. 127
Radius of Shadow Square System: approximately 28.6 million miles (46 million
kilometers)(approximately the orbit of Mercury in Sol System) "An inner ring of twenty rectangular shadow
squares, occupying what would have been the orbit of Mercury in Sol system..." (The Ringworld Engineers, ch. 4, p. 32).
But Mercury’s orbit is quite eccentric, varying from a minimum distance of 0.307 AU to a maximum distance of 0.467 AU. However:
"Near the zenith it [the Arch] was no more than a broken line of glowing blue-white. At the zenith itself the arch was cut by the otherwise
invisible ring of shadow squares" (Ringworld ch. 10, p. 149). This suggests the visual angle of the ring of shadow squares
isn’t that large, so Ye Editor has chosen to assume the minimum figure. We note the Ringworld Roleplaying Game specifies
the even smaller radius of approx. 27.3 million miles (0.294 AU), and that is what is shown on the "Ringworld Schematic" diagram above.
Stellar type: G3 verging on G2, barely smaller and cooler than Sol
The Ringworld Engineers: "Ringworld Parameters", p. 355
Stellar characteristics: Yellow-white color; surface temperature approx. 10,000 F; luminosity class V (main
sequence dwarf) This and subsequent data concerning the characteristics of Ringworld’s sun, given
in the Ringworld Roleplaying Game— Gamemaster Book (p. 4), are the characteristics given by astronomers
for a star of the given type.
Mass: approx. 0.97 Sol (approx. 1.93 x 1026grams)
Diameter: approx. 845,000 miles (1,360,000 kilometers)
Absolute luminosity (energy output): approx. 3.6 x 1033 ergs/second; approx.
3.6 x 1026 watts; approx. 4.8 x 1023 horsepower
Companion objects: The Ringworld, the shadow square system, and the Oort
cloud (distant cometary halo). No planets, moons, asteroids, or short-period comets"In the system of
the G2 sun there was nothing at all but the ring itself. No planets, no asteroids, no comets. [paragraph] ‘They cleaned it out,’ said
Louis. ‘They didn’t want anything to hit the ring’" (Ringworld ch. 6, p. 83). But later accounts state the Oort
cloud (cometary halo) was left, either because those comets presented no threat to the Ringworld (Ringworld’s
Children ch. 2, hc p. 44), or because there were too many to destroy and the Ringworld Engineers needed them
"To replace air lost over the rim walls" (The Ringworld Throne ch. 20, hc p. 259).
The Ringworld foundation, made of scrith, with an
average thickness apparently less than 100 feet The Ringworld Engineers
ch. 20, p. 195, is sculpted and shaped to resemble a normal planet’s terrain, with mountains, valleys, seas and
rivers. Above the foundation is an average of 40 feet of bedrock and/or soil
Ringworld ch. 17, p. 234 , plus water and atmosphere, resembling
the topography of a habitable planet. About half the area is covered with water Ringworld ch. 9, p. 131. It has an Earth-like atmosphere.
The habitat contains a complex, living ecology. However, there are no natural processes to build bedrock, nor mountains and hills,
so erosion eventually exposes the naked scrith foundation. Another way the Ringworld differs from a normal
planet, or ball world, is that all its seas have shallow, flat bottoms, and numerous bays
Ringworld ch. 8, p. 113. The Ringworld’s habitat requires constant
large-scale maintenance, as though it were a garden vastly bigger than worlds. The
First Ringworld Expedition and
Second Ringworld Expedition found extensive areas
had become deserts, due to a long-term breakdown in such maintenance The Ringworld Engineers
ch. 8, p. 74. The Ringworld Engineers
(those who built the Ringworld) intended a safe living environment, so imported no parasites, no disease germs, no large predators;
the Ringworld holds no analogs of mosquitoes or tigers. The vegetation is eerily but not precisely Earth-like, with green plants;
trees, grass, and bushes which are "gnarled in almost the right ways". Instrument readings indicate the biochemistry is Earth-like
even at the molecular level Ringworld ch 12, p. 160
The Sky and the Arch: When standing on the Ringworld, no horizon is seen. Details of the
landscape merge with the blue of the sky at the vanishing point, at infinity, the
mock-horizon. Overhead, the rest of the Ringworld appears
as a great Arch, stretching from one end of the world to the other, flaring
out rapidly near the bases, where it merges with the sky. It is seen divided into stripes of baby blue swirled with white
clouds, alternating with smaller strips of near-black. Near the zenith it is no more than a broken line of glowing blue-white,
cut by the otherwise invisible shadow squaresRingworld ch 11, p. 149. When standing on the Ringworld floor,
the Arch is an ever-present reminder that the Ringworld is an artifact bigger than worlds, a reminder of the power of the
Day and Night: During the day, the sun always appears directly overhead. Twilight comes not like
sundown on Earth, but as an eclipse of the sun. A day-and-night cycle on the Ringworld averages 30 hours long
The Ringworld Engineers: "Ringworld Parameters", p. 355 The
official accounts do not specify how many hours each of light, dark, and twilight there are, but it takes approximately
one hour and 40 minutes for a shadow square to cover the face of the sun Calculated from
the time it would take for the edge of a shadow square, moving at the "orbital" velocity of the shadow square system, to
transit a star with the diameter of Ringworld's sun. An unofficial account claims a day/night cycle consists of 21
hours of full daylight, 45 minutes of twilight, 7.5 hours of full night, and 45 more minutes of twilight
Ringworld Roleplaying Game— Gamemaster Book p. 4.
Presumably the 45 minute periods of twilight refer to when the Human (or hominid) eye notices the light
dimming; naturally, the light actually dims during the entire approximately one hour and 40 minutes it takes for a shadow
square to cover the sun, as seen from the Ringworld floor. But when full darkness comes, the terminator (the line dividing
light from shadow, day from night) races swiftly indeed across the landscape. The true glory of the Arch emerges only at
night, when the Arch glows far brighter than moonlight on Earth.
Dawn arrives as a sliver of noonday sun, spreading as fast as full darkness, with full daylight coming equally slowly.
Star-gazing: To someone raised on a normal planet, the night sky of the Ringworld appears strange
indeed. The dotted line of the Arch blazes brightly overhead, bisecting heaven in two, the light drowning out faint stars and
nebulae near it. There is no moon, no planets wandering across the sky. The stars themselves move at a snail’s pace; the
celestial sphere rotates only about six degrees of the circle in a night, or 1.67 degrees per hour
Ringworld Role-Playing Game: "Autopilot Print-out" (last page) .
The poles around which the stars rotate lie directly to port and
The underside of the Ringworld is like looking at the back of a mask of a planet’s topography, painted flat black. The
mountains and valleys, rivers and oceans molded into the habitable side of the Ringworld floor appear on the underside
in reverse; the hills and mountains as dimples and canyons, the valleys and canyons as ridges and mountain ranges. The
smallest details of the surface are smoothed out, covered by a thick blanket of foamed
scrithRingworld Engineers ch. 13, p. 121, which provides shielding
from meteorite impacts. Enormous black fins protrude from the bottom of the two
Great Oceans, providing cooling. Under certain areas of the
Maps are smaller cooling fins, providing areas of temperate and arctic
cold. Projecting from the surface of the Maps’ fins are myriads of relatively tiny flaps, providing seasonal temperature
variations Ringworld Engineers ch. 26, p. 266-7 .