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106-476: On Earth in 2850 AD, a bored Louis Wu is celebrating his 200th birthday. Despite his age, Louis is in perfect physical condition due to the longevity drug boosterspice . Nessus , a Pierson's puppeteer , offers him a mysterious job. Intrigued, Louis accepts. Nessus also recruits the Kzin Speaker-to-Animals and Teela Brown , a young human woman who becomes Louis's lover, for the rest of

212-540: A circumstellar disk , and then the planets grow out of that disk with the Sun. A nebula contains gas, ice grains, and dust (including primordial nuclides ). According to nebular theory , planetesimals formed by accretion , with the primordial Earth being estimated as likely taking anywhere from 70 to 100 million years to form. Estimates of the age of the Moon range from 4.5 Ga to significantly younger. A leading hypothesis

318-710: A chicken farm in New Jersey while his father was part of the exiled Lithuanian Diplomatic Service , since the United States continued to recognize the pre- World War II Lithuanian diplomats. Budrys was educated at the University of Miami and later at Columbia University in New York City. Incorporating his family's experience, Budrys's fiction depicts isolated and damaged people and themes of identity, survival and legacy. He taught himself English at

424-473: A co-producer. Tor/Seven Seas (same joint venture of Macmillan 's Tor Books and Seven Seas Entertainment who also published the English-language translation of Afro Samurai ) published a two-part original English-language manga adaptation of Ringworld , with the script written by Robert Mandell and the artwork by Sean Lam . Ringworld: The Graphic Novel, Part One , covering the events of

530-492: A common barycenter every 27.32 days relative to the background stars. When combined with the Earth–Moon system's common orbit around the Sun, the period of the synodic month , from new moon to new moon, is 29.53 days. Viewed from the celestial north pole , the motion of Earth, the Moon, and their axial rotations are all counterclockwise . Viewed from a vantage point above the Sun and Earth's north poles, Earth orbits in

636-548: A counterclockwise direction about the Sun. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.44 degrees from the perpendicular to the Earth–Sun plane (the ecliptic ), and the Earth-Moon plane is tilted up to ±5.1 degrees against the Earth–Sun plane. Without this tilt, there would be an eclipse every two weeks, alternating between lunar eclipses and solar eclipses . The Hill sphere , or

742-524: A first paperback edition of Ringworld , it's the one with the mistakes in it. It's worth money." After the publication of Ringworld , many fans identified numerous engineering problems in the Ringworld as described in the novel. One major one was that the Ringworld, being a rigid structure, was not actually in orbit around the star it encircled and would eventually drift, ultimately colliding with its sun and disintegrating. This led MIT students attending

848-420: A full rotation about its axis so that the Sun returns to the meridian . The orbital speed of Earth averages about 29.78 km/s (107,200 km/h; 66,600 mph), which is fast enough to travel a distance equal to Earth's diameter, about 12,742 km (7,918 mi), in seven minutes, and the distance from Earth to the Moon, 384,400 km (238,900 mi), in about 3.5 hours. The Moon and Earth orbit

954-421: A globe-spanning mid-ocean ridge system. At Earth's polar regions , the ocean surface is covered by seasonally variable amounts of sea ice that often connects with polar land, permafrost and ice sheets , forming polar ice caps . Earth's land covers 29.2%, or 149 million km (58 million sq mi) of Earth's surface. The land surface includes many islands around the globe, but most of

1060-468: A habitable inner surface (equivalent in area to approximately three million Earths), a breathable atmosphere, and a temperature optimal for humans. Night is provided by an inner ring of shadow squares which are connected to each other by thin, ultra-strong wire. When the crew completes their mission, as payment they will be given the starship they used to travel to the puppeteer world; it is about 1000 times faster than any human or Kzinti ship. When they reach

1166-480: A hidden, abandoned ringworld and determine what happened to its inhabitants. There have been many aborted attempts to adapt the novel to the screen. In 2001, Larry Niven reported that a movie deal had been signed and was in the early planning stages. In 2004, the Sci-Fi Channel reported that it was developing a Ringworld miniseries. The series never came to fruition. In 2013, it was again announced by

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1272-425: A liquid outer core that generates a magnetosphere capable of deflecting most of the destructive solar winds and cosmic radiation . Earth has a dynamic atmosphere , which sustains Earth's surface conditions and protects it from most meteoroids and UV-light at entry . It has a composition of primarily nitrogen and oxygen . Water vapor is widely present in the atmosphere, forming clouds that cover most of

1378-437: A pretty smooth pace." While praising the novel generally, he faulted Niven for relying on inconsistencies regarding evolution in his extrapolations to support his fictional premises. Sam Jordison described Ringworld as "arguably one of the most influential science fiction novels of the past 50 years." In addition to the two aliens, Niven includes a number of concepts from his other Known Space stories: The opening chapter of

1484-420: A ship that had brought back goods from worlds abandoned by the Ringworld builders. Nessus, using a tasp (a remote pleasure-giving device), conditions Prill into helping and joining them. When her ship returned to the Ringworld the last time, they discovered that civilization had collapsed. Louis surmises that a mold inadvertently brought back by a ship like Prill's mutated and broke down the superconductors vital to

1590-514: Is rounded into an ellipsoid with a circumference of about 40,000 km. It is the densest planet in the Solar System . Of the four rocky planets , it is the largest and most massive. Earth is about eight light-minutes away from the Sun and orbits it , taking a year (about 365.25 days) to complete one revolution. Earth rotates around its own axis in slightly less than a day (in about 23 hours and 56 minutes). Earth's axis of rotation

1696-403: Is Triton. "Ringworld" has become a generic term for such a structure, which is an example of what science fiction fans call a " Big Dumb Object ", or more formally a megastructure . Other science fiction authors have devised their own variants of Niven's Ringworld, notably Iain M. Banks ' Culture Orbitals , best described as miniature Ringworlds, and the titular ring-shaped Halo structures of

1802-456: Is a chemically distinct silicate solid crust, which is underlain by a highly viscous solid mantle. The crust is separated from the mantle by the Mohorovičić discontinuity . The thickness of the crust varies from about 6 kilometres (3.7 mi) under the oceans to 30–50 km (19–31 mi) for the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as

1908-535: Is approximately 9.8 m/s (32 ft/s ). Local differences in topography, geology, and deeper tectonic structure cause local and broad regional differences in Earth's gravitational field, known as gravity anomalies . The main part of Earth's magnetic field is generated in the core, the site of a dynamo process that converts the kinetic energy of thermally and compositionally driven convection into electrical and magnetic field energy. The field extends outwards from

2014-529: Is contained in 3.45 billion-year-old Australian rocks showing fossils of microorganisms . During the Neoproterozoic , 1000 to 539 Ma , much of Earth might have been covered in ice. This hypothesis has been termed " Snowball Earth ", and it is of particular interest because it preceded the Cambrian explosion , when multicellular life forms significantly increased in complexity. Following

2120-457: Is farthest out from its center of mass at its equatorial bulge, the summit of the volcano Chimborazo in Ecuador (6,384.4 km or 3,967.1 mi) is its farthest point out. Parallel to the rigid land topography the ocean exhibits a more dynamic topography . To measure the local variation of Earth's topography, geodesy employs an idealized Earth producing a geoid shape. Such a shape

2226-516: Is gained if the ocean is idealized, covering Earth completely and without any perturbations such as tides and winds. The result is a smooth but irregular geoid surface, providing a mean sea level (MSL) as a reference level for topographic measurements. Earth's surface is the boundary between the atmosphere, and the solid Earth and oceans. Defined in this way, it has an area of about 510 million km (197 million sq mi). Earth can be divided into two hemispheres : by latitude into

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2332-482: Is land, most of which is located in the form of continental landmasses within Earth's land hemisphere . Most of Earth's land is at least somewhat humid and covered by vegetation , while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater , lakes, rivers and atmospheric water combined. Earth's crust consists of slowly moving tectonic plates , which interact to produce mountain ranges, volcanoes , and earthquakes. Earth has

2438-426: Is liquid under normal atmospheric pressure. Differences in the amount of captured energy between geographic regions (as with the equatorial region receiving more sunlight than the polar regions) drive atmospheric and ocean currents , producing a global climate system with different climate regions , and a range of weather phenomena such as precipitation , allowing components such as nitrogen to cycle . Earth

2544-513: Is now slightly longer than it was during the 19th century due to tidal deceleration , each day varies between 0 and 2 ms longer than the mean solar day. Earth's rotation period relative to the fixed stars , called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86,164.0989 seconds of mean solar time ( UT1 ), or 23 56 4.0989 . Earth's rotation period relative to

2650-622: Is rare, though the alternative spelling Gaia has become common due to the Gaia hypothesis , in which case its pronunciation is / ˈ ɡ aɪ . ə / rather than the more classical English / ˈ ɡ eɪ . ə / . There are a number of adjectives for the planet Earth. The word "earthly" is derived from "Earth". From the Latin Terra comes terran / ˈ t ɛr ə n / , terrestrial / t ə ˈ r ɛ s t r i ə l / , and (via French) terrene / t ə ˈ r iː n / , and from

2756-487: Is that it was formed by accretion from material loosed from Earth after a Mars -sized object with about 10% of Earth's mass, named Theia , collided with Earth. It hit Earth with a glancing blow and some of its mass merged with Earth. Between approximately 4.1 and 3.8 Ga , numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of

2862-453: Is the basis for the astronomical unit (AU) and is equal to roughly 8.3 light minutes or 380 times Earth's distance to the Moon . Earth orbits the Sun every 365.2564 mean solar days , or one sidereal year . With an apparent movement of the Sun in Earth's sky at a rate of about 1°/day eastward, which is one apparent Sun or Moon diameter every 12 hours. Due to this motion, on average it takes 24 hours—a solar day—for Earth to complete

2968-457: Is tied to that of the Sun. Over the next 1.1 billion years , solar luminosity will increase by 10%, and over the next 3.5 billion years by 40%. Earth's increasing surface temperature will accelerate the inorganic carbon cycle , possibly reducing CO 2 concentration to levels lethally low for current plants ( 10  ppm for C4 photosynthesis ) in approximately 100–900 million years . A lack of vegetation would result in

3074-455: Is tilted with respect to the perpendicular to its orbital plane around the Sun, producing seasons . Earth is orbited by one permanent natural satellite , the Moon , which orbits Earth at 384,400 km (1.28 light seconds) and is roughly a quarter as wide as Earth. The Moon's gravity helps stabilize Earth's axis, causes tides and gradually slows Earth's rotation . Tidal locking has made

3180-583: The Milky Way and orbits about 28,000  light-years from its center. It is about 20 light-years above the galactic plane in the Orion Arm . The axial tilt of Earth is approximately 23.439281° with the axis of its orbit plane, always pointing towards the Celestial Poles . Due to Earth's axial tilt, the amount of sunlight reaching any given point on the surface varies over the course of

3286-759: The Pacific , North American , Eurasian , African , Antarctic , Indo-Australian , and South American . Other notable plates include the Arabian Plate , the Caribbean Plate , the Nazca Plate off the west coast of South America and the Scotia Plate in the southern Atlantic Ocean. The Australian Plate fused with the Indian Plate between 50 and 55 Ma . The fastest-moving plates are

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3392-419: The asthenosphere , the solid but less-viscous part of the upper mantle that can flow and move along with the plates. As the tectonic plates migrate, oceanic crust is subducted under the leading edges of the plates at convergent boundaries. At the same time, the upwelling of mantle material at divergent boundaries creates mid-ocean ridges. The combination of these processes recycles the oceanic crust back into

3498-415: The celestial equator , this is equivalent to an apparent diameter of the Sun or the Moon every two minutes; from Earth's surface, the apparent sizes of the Sun and the Moon are approximately the same. Earth orbits the Sun, making Earth the third-closest planet to the Sun and part of the inner Solar System . Earth's average orbital distance is about 150 million km (93 million mi), which

3604-408: The ocean floor form the top of Earth's crust , which together with parts of the upper mantle form Earth's lithosphere . Earth's crust may be divided into oceanic and continental crust. Beneath the ocean-floor sediments, the oceanic crust is predominantly basaltic , while the continental crust may include lower density materials such as granite , sediments and metamorphic rocks. Nearly 75% of

3710-430: The precessing or moving mean March equinox (when the Sun is at 90° on the equator), is 86,164.0905 seconds of mean solar time (UT1) (23 56 4.0905 ) . Thus the sidereal day is shorter than the stellar day by about 8.4 ms. Apart from meteors within the atmosphere and low-orbiting satellites, the main apparent motion of celestial bodies in Earth's sky is to the west at a rate of 15°/h = 15'/min. For bodies near

3816-413: The sphere of gravitational influence , of Earth is about 1.5 million km (930,000 mi) in radius. This is the maximum distance at which Earth's gravitational influence is stronger than that of the more distant Sun and planets. Objects must orbit Earth within this radius, or they can become unbound by the gravitational perturbation of the Sun. Earth, along with the Solar System, is situated in

3922-464: The "last ice age", covered large parts of the continents, to the middle latitudes, in ice and ended about 11,700 years ago. Chemical reactions led to the first self-replicating molecules about four billion years ago. A half billion years later, the last common ancestor of all current life arose. The evolution of photosynthesis allowed the Sun's energy to be harvested directly by life forms. The resultant molecular oxygen ( O 2 ) accumulated in

4028-533: The 1950s was published under the pen name "John A. Sentry", a reconfigured Anglification of his Lithuanian name. Among his other pseudonyms in the SF magazines of the 1950s and elsewhere, several revived as bylines for vignettes in his magazine Tomorrow Speculative Fiction , is "William Scarff". Budrys also wrote several stories under the names "Ivan Janvier" or "Paul Janvier", and used "Alger Rome" in his collaborations with Jerome Bixby . Budrys's 1960 novella Rogue Moon

4134-413: The 1971 Worldcon to chant, "The Ringworld is unstable!" Niven wrote the 1980 sequel The Ringworld Engineers in part to address these engineering issues. The second chapter refers to standard Earth gravity as 9.98 m/s (or even gives the unit as m/s [ sic ]), while standard Earth gravity is 9.81 m/s . The fifth chapter refers to Nereid as Neptune's largest moon; the planet's largest moon

4240-571: The 1990s he was the publisher and editor of the science fiction magazine Tomorrow Speculative Fiction . Budrys was born in Königsberg , Germany (present-day Kaliningrad , Russia ). His father Jonas Budrys was the consul general of Lithuania . In 1936, when Budrys was five years old, Jonas was appointed as the consul general in New York City. After the Soviet Union's occupation of Lithuania in 1940, Budrys helped his family run

4346-484: The Cambrian explosion, 535 Ma , there have been at least five major mass extinctions and many minor ones. Apart from the proposed current Holocene extinction event, the most recent was 66 Ma , when an asteroid impact triggered the extinction of non-avian dinosaurs and other large reptiles, but largely spared small animals such as insects, mammals , lizards and birds. Mammalian life has diversified over

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4452-654: The Earth. Terra is also the name of the planet in some Romance languages , languages that evolved from Latin , like Italian and Portuguese , while in other Romance languages the word gave rise to names with slightly altered spellings, like the Spanish Tierra and the French Terre . The Latinate form Gæa or Gaea ( English: / ˈ dʒ iː . ə / ) of the Greek poetic name Gaia ( Γαῖα ; Ancient Greek : [ɡâi̯.a] or [ɡâj.ja] )

4558-593: The Latin Tellus comes tellurian / t ɛ ˈ l ʊər i ə n / and telluric . The oldest material found in the Solar System is dated to 4.5682 +0.0002 −0.0004 Ga (billion years) ago. By 4.54 ± 0.04 Ga the primordial Earth had formed. The bodies in the Solar System formed and evolved with the Sun. In theory, a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into

4664-758: The Moon always face Earth with the same side. Earth, like most other bodies in the Solar System, formed 4.5 billion years ago from gas and dust in the early Solar System . During the first billion years of Earth's history , the ocean formed and then life developed within it. Life spread globally and has been altering Earth's atmosphere and surface, leading to the Great Oxidation Event two billion years ago. Humans emerged 300,000 years ago in Africa and have spread across every continent on Earth. Humans depend on Earth's biosphere and natural resources for their survival, but have increasingly impacted

4770-426: The Moon and, by inference, to that of Earth. Earth's atmosphere and oceans were formed by volcanic activity and outgassing . Water vapor from these sources condensed into the oceans, augmented by water and ice from asteroids, protoplanets , and comets . Sufficient water to fill the oceans may have been on Earth since it formed. In this model, atmospheric greenhouse gases kept the oceans from freezing when

4876-570: The RPG, along with notes composed by RPG author John Hewitt with Niven, was later used to form the "Bible" given to authors writing in the Man-Kzin Wars series. Niven himself recommended that Hewitt write one of the stories for the original two MKW books, although this never came to pass. Tsunami Games released two adventure games based on Ringworld . Ringworld: Revenge of the Patriarch

4982-418: The Ringworld and use the undamaged hyperdrive to return home. Using their flycycles, they set out for the rim of the ring, searching for technology to help them get home. They encounter primitive human natives who live in the ruins of a once-advanced city. The natives think that Louis is one of the engineers who created the ring, whom they revere as gods. The crew is attacked when Louis accidentally commits what

5088-499: The Ringworld civilization, causing its fall. Teela rejoins them, accompanied by her new lover, a traveling warrior named Seeker who protected her. Based on an insight gained from studying a Ringworld map, Louis comes up with a plan to get home. Teela chooses to remain on the Ringworld with Seeker. Louis, formerly skeptical about breeding for luck, now wonders if the entire mission was caused by Teela's luck, to unite her with her true love and help her mature. The party collects one end of

5194-458: The Solar System's planetary-sized objects, Earth is the object with the highest density . Earth's mass is approximately 5.97 × 10   kg ( 5.970  Yg ). It is composed mostly of iron (32.1% by mass ), oxygen (30.1%), silicon (15.1%), magnesium (13.9%), sulfur (2.9%), nickel (1.8%), calcium (1.5%), and aluminium (1.4%), with the remaining 1.2% consisting of trace amounts of other elements. Due to gravitational separation ,

5300-403: The Sun when the star reaches its maximum radius, otherwise, with tidal effects, it may enter the Sun's atmosphere and be vaporized. Earth has a rounded shape , through hydrostatic equilibrium , with an average diameter of 12,742 kilometres (7,918 mi), making it the fifth largest planetary sized and largest terrestrial object of the Solar System . Due to Earth's rotation it has

5406-569: The age of six by reading Robinson Crusoe . From Flash Gordon comic strips, Budrys read H. G. Wells 's The Time Machine ; Astounding Science Fiction caused him at the age of 11 to want to become a science fiction writer. His first published science fiction story was "The High Purpose", which appeared in Astounding in 1952. In 1952, Budrys worked as editor and manager for such science fiction publishers as Gnome Press and Galaxy Science Fiction . Some of Budrys's science fiction in

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5512-425: The atmosphere and due to interaction with ultraviolet solar radiation, formed a protective ozone layer ( O 3 ) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes . True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by

5618-450: The center, the temperature may be up to 6,000 °C (10,830 °F), and the pressure could reach 360  GPa (52 million  psi ). Because much of the heat is provided by radioactive decay, scientists postulate that early in Earth's history, before isotopes with short half-lives were depleted, Earth's heat production was much higher. At approximately 3  Gyr , twice the present-day heat would have been produced, increasing

5724-411: The channel, now rebranded as Syfy , that a miniseries of the novel was in development. This proposed 4-hour miniseries was being written by Michael R. Perry and would have been a co-production between MGM Television and Universal Cable Productions . In 2017, Amazon announced that Ringworld was one of three science fiction series it was developing for its streaming service. MGM were again listed as

5830-454: The continental crust , particularly during the early stages of Earth's history. New continental crust forms as a result of plate tectonics , a process ultimately driven by the continuous loss of heat from Earth's interior. Over the period of hundreds of millions of years, tectonic forces have caused areas of continental crust to group together to form supercontinents that have subsequently broken apart. At approximately 750 Ma , one of

5936-616: The continental surfaces are covered by sedimentary rocks, although they form about 5% of the mass of the crust. Earth's surface topography comprises both the topography of the ocean surface , and the shape of Earth's land surface. The submarine terrain of the ocean floor has an average bathymetric depth of 4 km, and is as varied as the terrain above sea level. Earth's surface is continually being shaped by internal plate tectonic processes including earthquakes and volcanism ; by weathering and erosion driven by ice, water, wind and temperature; and by biological processes including

6042-419: The core are chaotic; the magnetic poles drift and periodically change alignment. This causes secular variation of the main field and field reversals at irregular intervals averaging a few times every million years. The most recent reversal occurred approximately 700,000 years ago. The extent of Earth's magnetic field in space defines the magnetosphere . Ions and electrons of the solar wind are deflected by

6148-527: The core is primarily composed of the denser elements: iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements. The most common rock constituents of the crust are oxides . Over 99% of the crust is composed of various oxides of eleven elements, principally oxides containing silicon (the silicate minerals ), aluminium, iron, calcium, magnesium, potassium, or sodium. The major heat-producing isotopes within Earth are potassium-40 , uranium-238 , and thorium-232 . At

6254-463: The core, through the mantle, and up to Earth's surface, where it is, approximately, a dipole . The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10 T , with a magnetic dipole moment of 7.79 × 10 Am at epoch 2000, decreasing nearly 6% per century (although it still remains stronger than its long time average). The convection movements in

6360-539: The days shorter. Above the Arctic Circle and below the Antarctic Circle there is no daylight at all for part of the year, causing a polar night , and this night extends for several months at the poles themselves. These same latitudes also experience a midnight sun , where the sun remains visible all day. By astronomical convention, the four seasons can be determined by the solstices—the points in

6466-611: The earliest known supercontinents, Rodinia , began to break apart. The continents later recombined to form Pannotia at 600–540 Ma , then finally Pangaea , which also began to break apart at 180 Ma . The most recent pattern of ice ages began about 40 Ma , and then intensified during the Pleistocene about 3 Ma . High- and middle-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating about every 21,000, 41,000 and 100,000 years. The Last Glacial Period , colloquially called

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6572-544: The equally large area of land under permafrost ) or deserts (33%). The pedosphere is the outermost layer of Earth's land surface and is composed of soil and subject to soil formation processes. Soil is crucial for land to be arable. Earth's total arable land is 10.7% of the land surface, with 1.3% being permanent cropland. Earth has an estimated 16.7 million km (6.4 million sq mi) of cropland and 33.5 million km (12.9 million sq mi) of pastureland. The land surface and

6678-403: The former forces Nessus to flee from the group and then follow from a safe distance. While flying through a giant storm, Teela becomes separated from the others. When Louis and Speaker search for her, their flycycles are caught by an automated trap designed to catch speeders. They are brought to a floating police station. There, they meet Halrloprillalar Hotrufan ("Prill"), a former crew member of

6784-638: The growth and decomposition of biomass into soil . Earth's mechanically rigid outer layer of Earth's crust and upper mantle , the lithosphere , is divided into tectonic plates . These plates are rigid segments that move relative to each other at one of three boundaries types: at convergent boundaries , two plates come together; at divergent boundaries , two plates are pulled apart; and at transform boundaries , two plates slide past one another laterally. Along these plate boundaries, earthquakes, volcanic activity , mountain-building , and oceanic trench formation can occur. The tectonic plates ride on top of

6890-404: The heat in Earth is lost through plate tectonics, by mantle upwelling associated with mid-ocean ridges . The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans. The gravity of Earth is the acceleration that is imparted to objects due to the distribution of mass within Earth. Near Earth's surface, gravitational acceleration

6996-406: The land surface is taken by the four continental landmasses , which are (in descending order): Africa-Eurasia , America (landmass) , Antarctica , and Australia (landmass) . These landmasses are further broken down and grouped into the continents . The terrain of the land surface varies greatly and consists of mountains, deserts , plains , plateaus , and other landforms . The elevation of

7102-513: The land surface varies from a low point of −418 m (−1,371 ft) at the Dead Sea , to a maximum altitude of 8,848 m (29,029 ft) at the top of Mount Everest . The mean height of land above sea level is about 797 m (2,615 ft). Land can be covered by surface water , snow, ice, artificial structures or vegetation. Most of Earth's land hosts vegetation, but considerable amounts of land are ice sheets (10%, not including

7208-399: The lithosphere, which is divided into independently moving tectonic plates. Beneath the lithosphere is the asthenosphere , a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 410 and 660 km (250 and 410 mi) below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath

7314-410: The loss of oxygen in the atmosphere, making current animal life impossible. Due to the increased luminosity, Earth's mean temperature may reach 100 °C (212 °F) in 1.5 billion years, and all ocean water will evaporate and be lost to space, which may trigger a runaway greenhouse effect , within an estimated 1.6 to 3 billion years. Even if the Sun were stable, a fraction of the water in

7420-456: The lowercase when it is preceded by "the", such as "the atmosphere of the earth". It almost always appears in lowercase in colloquial expressions such as "what on earth are you doing?" The name Terra / ˈ t ɛr ə / occasionally is used in scientific writing and especially in science fiction to distinguish humanity's inhabited planet from others, while in poetry Tellus / ˈ t ɛ l ə s / has been used to denote personification of

7526-497: The magnetosphere. During magnetic storms and substorms , charged particles can be deflected from the outer magnetosphere and especially the magnetotail, directed along field lines into Earth's ionosphere , where atmospheric atoms can be excited and ionized, causing an aurora . Earth's rotation period relative to the Sun—its mean solar day—is 86,400 seconds of mean solar time ( 86,400.0025 SI seconds ). Because Earth's solar day

7632-409: The magnetosphere; solar wind pressure compresses the day-side of the magnetosphere, to about 10 Earth radii, and extends the night-side magnetosphere into a long tail. Because the velocity of the solar wind is greater than the speed at which waves propagate through the solar wind, a supersonic bow shock precedes the day-side magnetosphere within the solar wind. Charged particles are contained within

7738-483: The magnetosphere; the plasmasphere is defined by low-energy particles that essentially follow magnetic field lines as Earth rotates. The ring current is defined by medium-energy particles that drift relative to the geomagnetic field, but with paths that are still dominated by the magnetic field, and the Van Allen radiation belts are formed by high-energy particles whose motion is essentially random, but contained in

7844-417: The mantle, an extremely low viscosity liquid outer core lies above a solid inner core . Earth's inner core may be rotating at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1–0.5° per year, although both somewhat higher and much lower rates have also been proposed. The radius of the inner core is about one-fifth of that of Earth. The density increases with depth. Among

7950-612: The mantle. Due to this recycling, most of the ocean floor is less than 100 Ma old. The oldest oceanic crust is located in the Western Pacific and is estimated to be 200 Ma old. By comparison, the oldest dated continental crust is 4,030 Ma , although zircons have been found preserved as clasts within Eoarchean sedimentary rocks that give ages up to 4,400 Ma , indicating that at least some continental crust existed at that time. The seven major plates are

8056-548: The modern oceans will descend to the mantle , due to reduced steam venting from mid-ocean ridges. The Sun will evolve to become a red giant in about 5 billion years . Models predict that the Sun will expand to roughly 1  AU (150 million km; 93 million mi), about 250 times its present radius. Earth's fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, Earth will move to an orbit 1.7 AU (250 million km; 160 million mi) from

8162-399: The mother of Thor . Historically, "Earth" has been written in lowercase. Beginning with the use of Early Middle English , its definite sense as "the globe" was expressed as "the earth". By the era of Early Modern English , capitalization of nouns began to prevail , and the earth was also written the Earth , particularly when referenced along with other heavenly bodies. More recently,

8268-424: The name is sometimes simply given as Earth , by analogy with the names of the other planets , though "earth" and forms with "the earth" remain common. House styles now vary: Oxford spelling recognizes the lowercase form as the more common, with the capitalized form an acceptable variant. Another convention capitalizes "Earth" when appearing as a name, such as a description of the "Earth's atmosphere", but employs

8374-702: The natives consider a blasphemy, but extricate themselves. During their journey, Nessus reveals several puppeteer secrets. They initiated research into rendering the Kzinti extinct, considering them dangerous and useless, but found that the numerous Man-Kzin wars—which the Kzinti always lost—had greatly reduced their aggression: a very high percentage of Kzinti males were killed in each conflict, leaving more prudent and cautious survivors to breed. The puppeteers had also used Birthright Lotteries to try to breed humans for luck: all of Teela's ancestors for six generations are lottery winners. Speaker's outrage at learning

8480-425: The newly forming Sun had only 70% of its current luminosity . By 3.5 Ga , Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind . As the molten outer layer of Earth cooled it formed the first solid crust , which is thought to have been mafic in composition. The first continental crust , which was more felsic in composition, formed by

8586-552: The novel up to the sunflower attack on Speaker, was released on July 8, 2014. Part Two was released on November 10, 2015. Earth Earth is the third planet from the Sun and the only astronomical object known to harbor life . This is enabled by Earth being an ocean world , the only one in the Solar System sustaining liquid surface water . Almost all of Earth's water is contained in its global ocean, covering 70.8% of Earth's crust . The remaining 29.2% of Earth's crust

8692-593: The ocean may have covered Earth completely. The world ocean is commonly divided into the Pacific Ocean, Atlantic Ocean, Indian Ocean, Antarctic or Southern Ocean , and Arctic Ocean, from largest to smallest. The ocean covers Earth's oceanic crust , with the shelf seas covering the shelves of the continental crust to a lesser extent. The oceanic crust forms large oceanic basins with features like abyssal plains , seamounts , submarine volcanoes , oceanic trenches , submarine canyons , oceanic plateaus , and

8798-670: The oceanic plates, with the Cocos Plate advancing at a rate of 75 mm/a (3.0 in/year) and the Pacific Plate moving 52–69 mm/a (2.0–2.7 in/year). At the other extreme, the slowest-moving plate is the South American Plate, progressing at a typical rate of 10.6 mm/a (0.42 in/year). Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical ( rheological ) properties. The outer layer

8904-599: The orbit of maximum axial tilt toward or away from the Sun—and the equinoxes , when Earth's rotational axis is aligned with its orbital axis. In the Northern Hemisphere, winter solstice currently occurs around 21 December; summer solstice is near 21 June, spring equinox is around 20 March and autumnal equinox is about 22 or 23 September. In the Southern Hemisphere, the situation is reversed, with

9010-490: The original paperback edition of Ringworld featured Louis Wu teleporting eastward around the Earth in order to extend his birthday. Moving in this direction would, in fact, make local time later rather than earlier, so that Wu would soon arrive in the early morning of the next calendar day. Niven was "endlessly teased" about this error, which he corrected in subsequent printings to show Wu teleporting westward. In his dedication to The Ringworld Engineers , Niven wrote, "If you own

9116-649: The ozone layer, life colonized Earth's surface. Among the earliest fossil evidence for life is microbial mat fossils found in 3.48 billion-year-old sandstone in Western Australia , biogenic graphite found in 3.7 billion-year-old metasedimentary rocks in Western Greenland , and remains of biotic material found in 4.1 billion-year-old rocks in Western Australia. The earliest direct evidence of life on Earth

9222-474: The partial melting of this mafic crust. The presence of grains of the mineral zircon of Hadean age in Eoarchean sedimentary rocks suggests that at least some felsic crust existed as early as 4.4 Ga , only 140  Ma after Earth's formation. There are two main models of how this initial small volume of continental crust evolved to reach its current abundance: (1) a relatively steady growth up to

9328-501: The past 66 Mys , and several million years ago, an African ape species gained the ability to stand upright. This facilitated tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which led to the evolution of humans . The development of agriculture , and then civilization , led to humans having an influence on Earth and the nature and quantity of other life forms that continues to this day. Earth's expected long-term future

9434-478: The planet's environment . Humanity's current impact on Earth's climate and biosphere is unsustainable , threatening the livelihood of humans and many other forms of life, and causing widespread extinctions . The Modern English word Earth developed, via Middle English , from an Old English noun most often spelled eorðe . It has cognates in every Germanic language , and their ancestral root has been reconstructed as * erþō . In its earliest attestation,

9540-400: The planet. The water vapor acts as a greenhouse gas and, together with other greenhouse gases in the atmosphere, particularly carbon dioxide (CO 2 ), creates the conditions for both liquid surface water and water vapor to persist via the capturing of energy from the Sun's light . This process maintains the current average surface temperature of 14.76 °C (58.57 °F), at which water

9646-421: The polar Northern and Southern hemispheres; or by longitude into the continental Eastern and Western hemispheres. Most of Earth's surface is ocean water: 70.8% or 361 million km (139 million sq mi). This vast pool of salty water is often called the world ocean , and makes Earth with its dynamic hydrosphere a water world or ocean world . Indeed, in Earth's early history

9752-495: The present day, which is supported by the radiometric dating of continental crust globally and (2) an initial rapid growth in the volume of continental crust during the Archean , forming the bulk of the continental crust that now exists, which is supported by isotopic evidence from hafnium in zircons and neodymium in sedimentary rocks. The two models and the data that support them can be reconciled by large-scale recycling of

9858-493: The rates of mantle convection and plate tectonics, and allowing the production of uncommon igneous rocks such as komatiites that are rarely formed today. The mean heat loss from Earth is 87 mW m , for a global heat loss of 4.42 × 10  W . A portion of the core's thermal energy is transported toward the crust by mantle plumes , a form of convection consisting of upwellings of higher-temperature rock. These plumes can produce hotspots and flood basalts . More of

9964-564: The ring's floor up and finally breaking through. The top of the mountain, above the atmosphere, is therefore just a hole. Louis uses the police station to drag the Lying Bastard up and into the hole. Once the ship falls through and clears the ring, they can use its hyperdrive to get home. The book concludes with Louis and Speaker discussing returning to the Ringworld. Algis Budrys found Ringworld to be "excellent and entertaining ... woven together very skillfully and proceed[ing] at

10070-406: The shadow-square wire that snapped after the collision with their ship and fell near their path, and drag it behind them. Louis threads it through the Lying Bastard to tether it to the floating police station. "Fist-of-God", the enormous mountain near their crash site, was not on the Ringworld map, leading Louis to guess that it is the result of a meteoroid striking the underside of the ring, pushing

10176-522: The shape of an ellipsoid , bulging at its Equator ; its diameter is 43 kilometres (27 mi) longer there than at its poles . Earth's shape also has local topographic variations; the largest local variations, like the Mariana Trench (10,925 metres or 35,843 feet below local sea level), shortens Earth's average radius by 0.17% and Mount Everest (8,848 metres or 29,029 feet above local sea level) lengthens it by 0.14%. Since Earth's surface

10282-510: The ship's crew. On the puppeteer home world (which is fleeing deadly radiation which will arrive in 20,000 years), they are told that their goal is to determine if the Ringworld, a gigantic artificial ring near the puppeteers' path, poses any threat to their migration. The Ringworld is about one million miles (1.6 million km) wide and approximately the diameter of Earth's orbit, encircling a sunlike star. It rotates to provide artificial gravity 99% as strong as Earth's from centrifugal force . It has

10388-464: The star, instead orbiting stars or planets. The open source video game Endless Sky features an alien species that creates ringworlds. In 2017 Paradox Interactive added a DLC called "Utopia" to their game Stellaris , allowing the player to restore or build ringworlds. In 2021 Mobius Digital added a DLC called "Echoes of the Eye" to their game Outer Wilds , which allows the player to explore

10494-427: The summer and winter solstices exchanged and the spring and autumnal equinox dates swapped. Algis Budrys Algirdas Jonas " Algis " Budrys (January 9, 1931 – June 9, 2008) was a Lithuanian-American science fiction author, editor and critic. He was also known under the pen names Frank Mason , Alger Rome in collaboration with Jerome Bixby , John A. Sentry , William Scarff and Paul Janvier . In

10600-408: The vicinity of the Ringworld, they are unable to contact anyone. Their ship, the Lying Bastard , is disabled by an automated meteoroid -defense system. The vessel collides with a strand of shadow-square wire and crash-lands near a huge mountain, which is called "Fist-of-God" by the first natives they speak with. The fusion drive is destroyed, so they set out to find a way to get the Lying Bastard off

10706-593: The video game series Halo . Such a mini-Ringworld appears in Star Wars: The Book of Boba Fett , season 1, episode 5.. In the Paramount+ series Star Trek: Lower Decks season 4, episode 3, "In the Cradle of Vexilon", A Ringworld-like world is prominently featured. In 1984, a role-playing game based on this setting was produced by Chaosium named The Ringworld Roleplaying Game . Information from

10812-461: The word eorðe was used to translate the many senses of Latin terra and Greek γῆ gē : the ground, its soil , dry land, the human world, the surface of the world (including the sea), and the globe itself. As with Roman Terra /Tellūs and Greek Gaia , Earth may have been a personified goddess in Germanic paganism : late Norse mythology included Jörð ("Earth"), a giantess often given as

10918-620: The year. This causes the seasonal change in climate, with summer in the Northern Hemisphere occurring when the Tropic of Cancer is facing the Sun, and in the Southern Hemisphere when the Tropic of Capricorn faces the Sun. In each instance, winter occurs simultaneously in the opposite hemisphere. During the summer, the day lasts longer, and the Sun climbs higher in the sky. In winter, the climate becomes cooler and

11024-591: Was nominated for a Hugo Award and was later anthologized in The Science Fiction Hall of Fame, Volume Two (1973). His Cold War science fiction novel Who? was adapted for the screen in 1973. In addition to numerous Hugo Award and Nebula Award nominations, Budrys won the Science Fiction Research Association 's 2007 Pilgrim Award for lifetime contributions to speculative fiction scholarship. In 2009, he

11130-463: Was released in 1992 and Return to Ringworld in 1994. A third game, Ringworld: Within ARM's Reach , was also planned, but never completed. The video game franchise Halo , created by Bungie , took inspiration from the book in the creation and development of its story around the eponymous rings, called Halos. These are physically similar to the Ringworld, however they are much smaller and do not encircle

11236-567: Was the recipient of one of the first three Solstice Awards presented by the SFWA in recognition of his contributions to the field of science fiction. Having published about 100 stories and a half-dozen novels, with a wife and children to support. After 1960 Budrys wrote less fiction and worked in publishing, editing and advertising. He became better known as among science fiction's best critics than as writer, reviewing for Galaxy Science Fiction and The Magazine of Fantasy & Science Fiction ,

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