Road Rules

Road Rules, MTV's second reality show, debuted on July 19, 1995. The series followed six strangers between the ages of 18 and 24 (five strangers in the first four seasons) after stripping them of their money and putting them on an RV traveling from location to location only guided by a set of clues and a mission to complete at each location. It was nominated for an Emmy Award in 2001.

The ground-breaking series was a pioneer in travel/adventure/reward reality television (together with Mark Burnett's Eco-Challenge productions). Road Rules was created by Jonathan Murray and Mary-Ellis Bunim of Bunim/Murray Productions. After Bunim died of cancer in early 2004, the show went on hiatus for three years. After season 14 ended, it has been confirmed that Road Rules is no longer in production, although MTV nor Bunim-Murray have commented on the status of the series.[citation needed]

The show was spawned from its sister show The Real World. The idea of Road Rules came to mind, when Real World castmates Jon, Tami and Dominic traveled in an RV across the United States to get to their The Real World: Los Angeles house in the first two episodes of the second season. Bunim-Murray began working on the show soon after the third San Francisco season, and finally debuted in 1995. The show garnered a spin-off series, Real World/Road Rules Challenge, which is still in production.

There was also a 1998 mini-series, Road Rules: All-Stars, in which five former stars from The Real World go on a short Road Rules course managed by infamous former Real World housemate Puck, who, until the very end of the series, was disguising his identity with the alias "Mr. Big". However, this is generally considered the first season of Real World/Road Rules Challenge.

Contents [hide]
1 Seasons
2 Show's evolution
2.1 Europe (Season 3)
2.2 Islands (Season 4)
2.3 Northern Trail (Season 5)
2.4 Down Under (Season 6)
2.5 Latin America(Season 7)
2.6 Semester at Sea (Season 8)
2.7 Maximum Velocity Tour (Season 9)
2.8 The Quest (Season 10)
3 Road Rules face-offs
4 External links


[edit] Seasons
Season Year Cast members Handsome Reward
1 USA - The First Adventure 1995 Allison Jones Kit Hoover Los Jackson Mark Long Shelly Spottedhorse N/A European Trip
2 USA - The Second Adventure 1996 Emily Bailey Tim Beggy Christian Breivik Devin Elston Effie Perez N/A Honda Civics
3 Europe 1997 Patrice Boudibela Antoine de Bouverie Elizabeth "Belou" Den Tex Chris Melling Michelle Parma N/A Home entertainment center and $1000 cash
4 Islands 1997 Jake Bronstein Kalle Dedolph Vincent Forcier Oscar Hernandez Erika Ruen N/A Enrollment and Tuition on Semester at Sea Program
5 Northern Trail 1998 Jon Holmes Roni Martin Tara McDaniel Dan Setzler Noah Rickun Anne Wharton Trip to Greece
6 Down Under 1998 Susie Meister Chadwick Pelletier Shayne McBride Christina Pazsitzky Kefla Hare Piggy Thomas Choice of Seadoo, Motorbike or Harley
7 Latin America 1999 Brian Lancaster Sarah Martinez Gladys Sanabria Josh Florence Holly Shand Abe Ingersoll Volkswagen Beetle
8 Semester at Sea 1999 Veronica Portillo Yes Duffy Pua Medieros Pawel Litwinski Ayanna Mackins Shawn Sealy iMac Desktop Computer Package
9 Maximum Velocity Tour 2000 Laterrian Wallace Kathryn Kolb Holly Brentson James Orlando Msaada Nia Theo Vonkurnatowski Cumulative Cash Prize on Cobalt Credit Card
10 The Quest 2001 Jisela Delgado Sophia Pasquis Adam Larson Blair Herter Steve Meinke Ellen Cho Suzuki Grand Vitaras
*Katie Doyle
11 Campus Crawl 2002 Kendal Sheppard Shane Landrum Rachel Robinson Darrell Taylor Sarah Greyson Eric Jones Trip around the World
*Raquel Duran
12 South Pacific 2003 Cara Zavaleta Dave Giuntoli Christena Pyle Abram Boise Mary Beth Decker Donell Langham Car
*Tina Barta *Chris Graebe *Jeremy Blossom
13 X-Treme 2004 Jodi Weatherton Danny Dias Kina Dean Derrick Kosinski Ibis Nieves Patrick Maloney Subaru WRXI
*Nick Haggart *Angela Trimbur *Jillian Zoboroski
14 Viewers' Revenge 2007 Abram Boise Kina Dean Shane Landrum Adam Larson Susie Meister Veronica Portillo Mazda3 and Cumulative Cash Prize
*Dan Walsh *David Leech *Angel Turlington *Tori Hall
*Derek McCray *Dan Walsh *Susie Meister
*LaMonte Ponder

[edit] Show's evolution
The series began with a simple format, closely mirroring its parent show The Real World. The concept was simple, abandon five strangers on the road, take away their money, have them drive around in an RV completing missions and doing odd jobs for money, and if they lasted to the end of the trip, they would win a "handsome reward". It was touted as The Real World on an RV, but as the show progressed, several changes were made to the show for various reasons, mostly having to do with causing excitement and raising sagging ratings.

[edit] Europe (Season 3)
In its third season, producers of the show took production to the next level by deciding to move the show from the United States to Europe. While the first two seasons were not themed according to the series' location, the third season introduced the subtitle into the concept which would usually strand the Roadies in different locations around the world.

[edit] Islands (Season 4)
For the first time, the RV was completely abandoned for a short time in favor of an alternate mode of transportation. The cast traveled in and around the Caribbean islands and for a short time traveled on a catamaran. This season also competed against the Boston season of the Real World in San Juan, Puerto Rico, planting the seeds for The Real World/Road Rules Challenge and future face-offs.

[edit] Northern Trail (Season 5)
Changing the dynamic of the cast in hopes of creating more drama by including more people in the RV, an additional cast member would be included in each season, changing the number of cast members from five to six. Jon is considered the "stand out" of the season. With his zany antics and half-baked notions of romantic hijinks, he became both one of the most loved and conversely despised characters in the show's history.

[edit] Down Under (Season 6)
[edit] Latin America(Season 7)
[edit] Semester at Sea (Season 8)
Enticed by the idea of sailing around the world, producers put the cast on the (for 2005) University of Pittsburgh's Semester at Sea educational program. For the first time in any season, in order for the cast to get their handsome reward, the cast needed to complete coursework aboard the ship. Prior to this, cast members only needed to get to the end of the trip, and would not be penalized for refusing to do a mission. The most unusual mission was "Anime Mission", visiting Japan and experiencing ADR recording by their voices with Japanese director, Yuji Moriya who was center in the anime industry in the USA at that time.

[edit] Maximum Velocity Tour (Season 9)
Due to an exaggerated trend of sagging ratings, some say due to the Semester at Sea season, the show underwent a major re-tooling. The Maximum Velocity Tour represents when the series transitioned from a documentary-style reality show to an entertainment reality show. The show was brought back to the US and given a "game show" format. At the helm of a trip was a fictional character named the "Road Master" completed. After the cast would complete a mission, they would have money added to the group pool and if they failed to complete a mission, they would lose the money.

[edit] The Quest (Season 10)
Producers continued to re-tool the show. This time, if the cast members lost two missions, they would have to vote out a cast member. Any additional mission lost after that, another cast member would be voted off. Also, instead of adding money to a group pool, the cast competed each mission for a "key" to the handsome reward. The "keys" were placed in the RV on a large board where each "key" represented a virtue the cast learned in that mission. For this season, the "key" would be represented as part of a crest. If the cast lost a mission, they would not receive the "key" until they voted off a cast member. Jisela Delgado was the first cast member to be voted off in the series. Katie Doyle was the first replacement in the series. The series remained largely unchanged after this season, although each subsequent series had its own variation on the rules of the game.

Sunny Pundai Oussari Thevudaiyanmavan

[edit] Road Rules face-offs
Setting up the idea for Real World/Road Rules Challenge, the face-offs have come to be an instrumental part of each season. The current cast competes either with a current "The Real World" cast who would be filming their series parallel to theirs or a former Road Rules cast, if Real World was ever out of its production season. The first official face-off, between the Islands and Boston casts gained such high ratings, that another spin-off series was begun, the ever-popular Challenges, and a pattern in every season where the cast would compete against another cast for a separate prize.

First Adventure - No face-off during this season. Although cast member Mark initially appeared on the Real World: San Francisco season as one of three possible replacements for ousted housemate, Puck. The housemates chose Jo over Mark.
Second Adventure vs. Real World Miami - The Road Rules cast posed as house cleaners and stole the Miami's cast eight-ball. They did so successfully. Timmy fooled Miami's Dan and Cynthia who were obviously suspicious of the unannounced cleaning crew.
Europe - No face-off.
Islands vs. Real World Boston - The casts competed in a series of competitions in San Juan, Puerto Rico. The Boston cast narrowly won the games. Syrus, while competing in the final mission, busted his shin on a bench for his team to take the prize. The Islands crew, who desperately needed money at that time asked the Boston cast to split their winnings. The Boston cast declined to do so. They also played paintball with a team of former Road Rulers from different seasons.
Northern Trail vs. Road Rules All-Stars - The casts competed in a series of Olympic-themed games including luge, ski jumping, and figure skating. The Olympic-theme was due in part to the fact that the casts were competing in the Olympic facilities at Lake Placid, New York. The All-Stars won the competition in the figure skating competition. The Northern Trail handed the keys off to their RV, which the All-Stars cast used for their season.
Down Under vs. Real World Seattle - The cast competed in the "Aqua Games" in Seattle's main harbor. They competed in various games, including holding onto the back of a raft attached to a seadoo, jumping into rings from a platform, and the finale: a bull-riding contest. Nathan won the competition for the Seattle cast, while Christina and Susie both took the competition as a joke.
Latin America vs. Road Rules Down Under - The cast competed in Veracruz, Mexico in a series of games. The Down Under cast took the prize, but the more serious implication of this face-off was when Abe of the Latin America cast hooked up with Susie in the RV. This started the tension between Abe and Gladys, which led to Gladys hitting Abe and being sent home.
Semester at Sea - Did not do a face-off. However, during the filming and airing of the series, rumors were rampant that the two casts met up in India, where The Real World Hawaii took their vacation and the Semester at Sea cast landed in port. This was never confirmed or denied. Various students on the Semester at Sea program participated in various missions during this season.
Maximum Velocity Tour vs. Real World New Orleans - In a throwback to the very first face-off, the Maximum Velocity Tour cast worked with a Make-A-Wish child to pull off a sting on the Real World: New Orleans cast. They included the Make-A-Wish child in the mission, as the cast posed as Make-A-Wish ambassadors to distract the cast members while James and Laterrian jumped a back wall to steal the New Orleans' cast robotic dog. Hearing that the cast was in town, Melissa of the New Orleans cast hid the eight-ball in anticipation of the cast stealing it. This cast also competed in Los Angeles, CA against the cast of the first season of Making the Band (O-Town) in which O-Town won. They also competed against a group of winners from an MTV.com contest in Provo, Utah, which Road Rules won.
The Quest vs. Real World Back to New York - The casts met up in Morocco. These two casts met up after spending a week in Palm Spring during casting. Members of each cast had already made friends and enemies, creating instant drama and the casts playing practical jokes on each other. In direct contrast to her competitive persona on the Challenges, Back to New York's Coral and fellow cast member Nicole refused to compete in a mud wrestling challenge. This left Back to New York's Lori and Rachel to compete alone against the Road Rules girls. In a grueling mud wrestling competition, Road Rules won because Coral and Nicole refused to compete.
Campus Crawl vs. Real World Las Vegas - The Campus Crawl cast first had to take a photograph with one of the Las Vegas cast members handcuffed to the bathtub. Because Raquel had met Steven of Las Vegas in the College Station casting call, Raquel was able to coax Steven to show her and Rachel the Las Vegas suite. Not knowing that the two were from Road Rules, they were able to handcuff and photograph Steven. The cast competed at Lake Red Rock near Las Vegas, Nevada which The Real World won.
South Pacific vs. Road Rules Campus Crawl - This cast competed in a marathon challenge, in which the cast was required to compete in different games but were not allowed to sleep during the 48-hour period. In the last competition, in which they had to remember various details in the past 48 hours, the Campus Crawl cast pulled off a win.
X-treme vs. Road Rules South Pacific - The two casts competed in a series of games which concludes with a boxing match. The X-treme cast beat the South Pacific cast.
Viewers' Revenge vs. Pit Crew. Roadies beat out the Pit Crew in a mission that had players carrying tires from sand dunes. They also beat the Pit Crew in a mission that involved weight lifting and weight puzzles, along with a football game. The final challenge was carrying boxes across semis and dropping them into the hole; Pit Crew finally won, making the score 3-1.

The Earth

Earth is the third planet from the Sun. It is the fifth largest of the eight planets in the solar system, and the largest of the terrestrial planets (non-gas planets) in the Solar System in terms of diameter, mass and density. It is also referred to as the World, the Blue Planet,[note 3] and Terra.[note 4]

Home to millions of species,[11] including humans, Earth is the only place in the universe where life is known to exist. The planet formed 4.54 billion years ago,[12] and life appeared on its surface within a billion years. Since then, Earth's biosphere has significantly altered the atmosphere and other abiotic conditions on the planet, enabling the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks harmful radiation, permitting life on land.[13] The physical properties of the Earth, as well as its geological history and orbit, allowed life to persist during this period. The world is expected to continue supporting life for another 1.5 billion years, after which the rising luminosity of the Sun will eliminate the biosphere.[14]

Earth's outer surface is divided into several rigid segments, or tectonic plates, that gradually migrate across the surface over periods of many millions of years. About 71% of the surface is covered with salt-water oceans, the remainder consisting of continents and islands; liquid water, necessary for all known life, is not known to exist on any other planet's surface.[note 5][note 6] Earth's interior remains active, with a thick layer of relatively solid mantle, a liquid outer core that generates a magnetic field, and a solid iron inner core.

Earth interacts with other objects in outer space, including the Sun and the Moon. At present, Earth orbits the Sun once for every roughly 366.26 times it rotates about its axis. This length of time is a sidereal year, which is equal to 365.26 solar days.[note 7] The Earth's axis of rotation is tilted 23.4° away from the perpendicular to its orbital plane,[15] producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days). Earth's only known natural satellite, the Moon, which began orbiting it about 4.53 billion years ago, provides ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Between approximately 4.1 and 3.8 billion years ago, asteroid impacts during the Late Heavy Bombardment caused significant changes to the surface environment.

Both the mineral resources of the planet, as well as the products of the biosphere, contribute resources that are used to support a global human population. The inhabitants are grouped into about 200 independent sovereign states, which interact through diplomacy, travel, trade and military action. Human cultures have developed many views of the planet, including personification as a deity, a belief in a flat Earth or in Earth being the center of the universe, and a modern perspective of the world as an integrated environment that requires stewardship.

Contents [hide]
1 Chronology
1.1 Evolution of life
1.2 Future
2 Composition and structure
2.1 Shape
2.2 Chemical composition
2.3 Internal structure
2.4 Heat
2.5 Tectonic plates
2.6 Surface
2.7 Hydrosphere
2.8 Atmosphere
2.8.1 Weather and climate
2.8.2 Upper atmosphere
2.9 Magnetic field
3 Orbit and rotation
3.1 Rotation
3.2 Orbit
3.3 Axial tilt and seasons
4 Moon
5 Habitability
5.1 Biosphere
5.2 Natural resources and land use
5.3 Natural and environmental hazards
5.4 Human geography
6 Cultural viewpoint
7 See also
8 Notes
9 References
10 Bibliography
11 External links


Chronology
Main article: History of the Earth
See also: Geological history of Earth
Scientists have been able to reconstruct detailed information about the planet's past. The earliest dated solar system material is dated to 4.5672 ± 0.0006 billion years ago,[16] and by 4.54 billion years ago (within an uncertainty of 1%)[12] the Earth and the other planets in the Solar System formed out of the solar nebula—a disk-shaped mass of dust and gas left over from the formation of the Sun. This assembly of the Earth through accretion was largely completed within 10–20 million years.[17] Initially molten, the outer layer of the planet Earth cooled to form a solid crust when water began accumulating in the atmosphere. The Moon formed shortly thereafter, 4.53 billion years ago,[18] most likely as the result of a Mars-sized object (sometimes called Theia) with about 10% of the Earth's mass[19] impacting the Earth in a glancing blow.[20] Some of this object's mass would have merged with the Earth and a portion would have been ejected into space, but enough material would have been sent into orbit to form the Moon.

Outgassing and volcanic activity produced the primordial atmosphere. Condensing water vapor, augmented by ice and liquid water delivered by asteroids and the larger proto-planets, comets, and trans-Neptunian objects produced the oceans.[21] The newly-formed Sun was only 70% of its present luminosity, yet evidence shows that the early oceans remained liquid—a contradiction dubbed the faint young Sun paradox. A combination of greenhouse gases and higher levels of solar activity served to raise the Earth's surface temperature, preventing the oceans from freezing over.[22]

Two major models have been proposed for the rate of continental growth:[23] steady growth to the present-day[24] and rapid growth early in Earth history.[25] Current research shows that the second option is most likely, with rapid initial growth of continental crust[26] followed by a long-term steady continental area.[27][28][29] On time scales lasting hundreds of millions of years, the surface continually reshaped itself as continents formed and broke up. The continents migrated across the surface, occasionally combining to form a supercontinent. Roughly 750 million years ago (Ma), one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 Ma, then finally Pangaea, which broke apart 180 Ma.[30]

Evolution of life
Main article: Evolutionary history of life
At present, Earth provides the only example of an environment that has given rise to the evolution of life.[31] Highly energetic chemistry is believed to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed.[32] The development of photosynthesis allowed the Sun's energy to be harvested directly by life forms; the resultant oxygen accumulated in the atmosphere and formed in a layer of ozone (a form of molecular oxygen [O3]) in the upper atmosphere. The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes.[33] True multicellular organisms formed as cells within colonies became increasingly specialized. Aided by the absorption of harmful ultraviolet radiation by the ozone layer, life colonized the surface of Earth.[34]

Since the 1960s, it has been hypothesized that severe glacial action between 750 and 580 Ma, during the Neoproterozoic, covered much of the planet in a sheet of ice. This hypothesis has been termed "Snowball Earth", and is of particular interest because it preceded the Cambrian explosion, when multicellular life forms began to proliferate.[35]

Following the Cambrian explosion, about 535 Ma, there have been five mass extinctions.[36] The last extinction event was 65 Ma, when a meteorite collision probably triggered the extinction of the (non-avian) dinosaurs and other large reptiles, but spared small animals such as mammals, which then resembled shrews. Over the past 65 million years, mammalian life has diversified, and several million years ago, an African ape-like animal such as orrorin tugenensis gained the ability to stand upright.[37] This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain. The development of agriculture, and then civilization, allowed humans to influence the Earth in a short time span as no other life form had,[38] affecting both the nature and quantity of other life forms.

The present pattern of ice ages began about 40 Ma and then intensified during the Pleistocene about 3 Ma. The polar regions have since undergone repeated cycles of glaciation and thaw, repeating every 40–100,000 years. The last ice age ended 10,000 years ago.[39]

Future
Main article: Future of the Earth
See also: Risks to civilization, humans and planet Earth

The future of the planet is closely tied to that of the Sun. As a result of the steady accumulation of helium at the Sun's core, the star's total luminosity will slowly increase. The luminosity of the Sun will grow by 10% over the next 1.1 Gyr (1.1 billion years) and by 40% over the next 3.5 Gyr.[40] Climate models indicate that the rise in radiation reaching the Earth is likely to have dire consequences, including the possible loss of the planet's oceans.[41]

The Earth's increasing surface temperature will accelerate the inorganic CO2 cycle, reducing its concentration to lethal levels for plants (10 ppm for C4 photosynthesis) in 900 million years. The lack of vegetation will result in the loss of oxygen in the atmosphere, so animal life will become extinct within several million more years.[42] After another billion years all surface water will have disappeared[14] and the mean global temperature will reach 70 °C[42](158 °F). The Earth is expected to be effectively habitable for about another 500 million years,[43] although this may be extended up to 2.3 billion years if the nitrogen is removed from the atmosphere.[44] Even if the Sun were eternal and stable, the continued internal cooling of the Earth would result in a loss of much of its CO2 due to reduced volcanism,[45] and 35% of the water in the oceans would descend to the mantle due to reduced steam venting from mid-ocean ridges.[46]

The Sun, as part of its evolution, will become a red giant in about 5 Gyr. Models predict that the Sun will expand out to about 250 times its present radius, roughly 1 AU (150,000,000 km).[40][47] Earth's fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, the Earth will move to an orbit 1.7 AU (250,000,000 km) from the Sun when the star reaches it maximum radius. Therefore, the planet is expected to escape envelopment by the expanded Sun's sparse outer atmosphere, though most, if not all, remaining life will be destroyed because of the Sun's increased luminosity.[40] However, a more recent simulation indicates that Earth's orbit will decay due to tidal effects and drag, causing it to enter the red giant Sun's atmosphere and be destroyed.[47]

Composition and structure
Main article: Earth science
Further information: Earth physical characteristics tables
Earth is a terrestrial planet, meaning that it is a rocky body, rather than a gas giant like Jupiter. It is the largest of the four solar terrestrial planets, both in terms of size and mass. Of these four planets, Earth also has the highest density, the highest surface gravity, the strongest magnetic field, and fastest rotation.[48] It also is the only terrestrial planet with active plate tectonics.[49]

Shape
Main article: Figure of the Earth

Size comparison of inner planets (left to right): Mercury, Venus, Earth and MarsThe shape of the Earth is very close to that of an oblate spheroid, a sphere squished along the orientation from pole to pole such that there is a bulge around the equator.[50] This bulge results from the rotation of the Earth, and causes the diameter at the equator to be 43 km larger than the pole to pole diameter.[51] The average diameter of the reference spheroid is about 12,742 km, which is approximately 40,000 km/π, as the meter was originally defined as 1/10,000,000 of the distance from the equator to the North Pole through Paris, France.[52]

Local topography deviates from this idealized spheroid, though on a global scale, these deviations are very small: Earth has a tolerance of about one part in about 584, or 0.17%, from the reference spheroid, which is less than the 0.22% tolerance allowed in billiard balls.[53] The largest local deviations in the rocky surface of the Earth are Mount Everest (8,848 m above local sea level) and the Mariana Trench (10,911 m below local sea level). Because of the equatorial bulge, the feature farthest from the center of the Earth is actually Mount Chimborazo in Ecuador.[54][55]

Chemical Composition of the Crust[56] Compound Formula Composition
Continental Oceanic
silica SiO2 60.2% 48.6%
alumina Al2O3 15.2% 16.5%
lime CaO 5.5% 12.3%
magnesia MgO 3.1% 6.8%
iron(II) oxide FeO 3.8% 6.2%
sodium oxide Na2O 3.0% 2.6%
potassium oxide K2O 2.8% 0.4%
iron(III) oxide Fe2O3 2.5% 2.3%
water H2O 1.4% 1.1%
carbon dioxide CO2 1.2% 1.4%
titanium dioxide TiO2 0.7% 1.4%
phosphorus pentoxide P2O5 0.2% 0.3%
Total 99.6% 99.9%
Chemical composition
See also: Abundance of elements on Earth
The mass of the Earth is approximately 5.98 × 1024 kg. It is composed mostly of iron (32.1%), 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 mass segregation, the core region is believed to be primarily composed of iron (88.8%), with smaller amounts of nickel (5.8%), sulfur (4.5%), and less than 1% trace elements.[57]

The geochemist F. W. Clarke calculated that a little more than 47% of the Earth's crust consists of oxygen. The more common rock constituents of the Earth's crust are nearly all oxides; chlorine, sulfur and fluorine are the only important exceptions to this and their total amount in any rock is usually much less than 1%. The principal oxides are silica, alumina, iron oxides, lime, magnesia, potash and soda. The silica functions principally as an acid, forming silicates, and all the commonest minerals of igneous rocks are of this nature. From a computation based on 1,672 analyses of all kinds of rocks, Clarke deduced that 99.22% were composed of 11 oxides (see the table at right.) All the other constituents occur only in very small quantities.[note 8]

Internal structure
Main article: Structure of the Earth
The interior of the Earth, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties. The outer layer of the Earth 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, and the thickness of the crust varies: averaging 6 km under the oceans and 30–50 km on the continents. The crust and the cold, rigid, top of the upper mantle are collectively known as the lithosphere, and it is of the lithosphere that the tectonic plates are comprised. 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 kilometers below the surface, spanning a transition zone that separates the upper and lower mantle. Beneath the mantle, an extremely low viscosity liquid outer core lies above a solid inner core.[58] The inner core may rotate at a slightly higher angular velocity than the remainder of the planet, advancing by 0.1–0.5° per year.[59]

Geologic layers of the Earth[60]
Earth cutaway from core to exosphere. Not to scale. Depth[61]
km Component Layer Density
g/cm3
0–60 Lithosphere[note 9] —
0–35 ... Crust[note 10] 2.2–2.9
35–60 ... Upper mantle 3.4–4.4
35–2890 Mantle 3.4–5.6
100–700 ... Asthenosphere —
2890–5100 Outer core 9.9–12.2
5100–6378 Inner core 12.8–13.1

Heat
Earth's internal heat comes from a combination of residual heat from planetary accretion (about 20%) and heat produced through radioactive decay (80%).[62] The major heat-producing isotopes in the Earth are potassium-40, uranium-238, uranium-235, and thorium-232.[63] At the center of the planet, the temperature may be up to 7,000 K and the pressure could reach 360 GPa.[64] Because much of the heat is provided by radioactive decay, scientists believe that early in Earth history, before isotopes with short half-lives had been depleted, Earth's heat production would have been much higher. This extra heat production, twice present-day at approximately 3 billion years ago,[62] would have increased temperature gradients within the Earth, increasing the rates of mantle convection and plate tectonics, and allowing the production of igneous rocks such as komatiites that are not formed today.[65]

Present-day major heat-producing isotopes[66] Isotope Heat release
W/kg isotope Half-life

years Mean mantle concentration
kg isotope/kg mantle Heat release
W/kg mantle
238U 9.46 × 10-5 4.47 × 109 30.8 × 10-9 2.91 × 10-12
235U 5.69 × 10-4 7.04 × 108 0.22 × 10-9 1.25 × 10-13
232Th 2.64 × 10-5 1.40 × 1010 124 × 10-9 3.27 × 10-12
40K 2.92 × 10-5 1.25 × 109 36.9 × 10-9 1.08 × 10-12

Total heat loss from the earth is 4.2 × 1013 Watts.[67] 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.[68] More of the heat in the 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, majority of which occurs in the oceans due to the crust there being much thinner than that of the continents.[67]

Tectonic plates
Earth's main plates[69]
Plate name Area
106 km²
African Plate[note 11] 78.0
Antarctic Plate 60.9
Australian Plate 47.2
Eurasian Plate 67.8
North American Plate 75.9
South American Plate 43.6
Pacific Plate 103.3
Main article: Plate tectonics
The mechanically rigid outer layer of the Earth, the lithosphere, is broken into pieces called tectonic plates. These plates are rigid segments that move in relation to one another at one of three types of plate boundaries: Convergent boundaries, at which two plates come together, Divergent boundaries, at which two plates are pulled apart, and Transform boundaries, in which two plates slide past one another laterally. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation can occur along these plate boundaries.[70] The tectonic plates ride on top of the asthenosphere, the solid but less-viscous part of the upper mantle that can flow and move along with the plates,[71] and their motion is strongly coupled with patterns convection inside the Earth's mantle.

As the tectonic plates migrate across the planet, the ocean floor 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 continually recycles the oceanic crust back into the mantle. Because of this recycling, most of the ocean floor is less than 100 million years in age. The oldest oceanic crust is located in the Western Pacific, and has an estimated age of about 200 million years.[72][73] By comparison, the oldest dated continental crust is 4030 million years old.[74]

Other notable plates include the Indian Plate, 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 actually fused with Indian Plate between 50 and 55 million years ago. The fastest-moving plates are the oceanic plates, with the Cocos Plate advancing at a rate of 75 mm/yr[75] and the Pacific Plate moving 52–69 mm/yr. At the other extreme, the slowest-moving plate is the Eurasian Plate, progressing at a typical rate of about 21 mm/yr.[76]

Surface
Main articles: Landform and Extreme points of Earth
The Earth's terrain varies greatly from place to place. About 70.8%[77] of the surface is covered by water, with much of the continental shelf below sea level. The submerged surface has mountainous features, including a globe-spanning mid-ocean ridge system, as well as undersea volcanoes,[51] oceanic trenches, submarine canyons, oceanic plateaus and abyssal plains. The remaining 29.2% not covered by water consists of mountains, deserts, plains, plateaus, and other geomorphologies.

The planetary surface undergoes reshaping over geological time periods due to the effects of tectonics and erosion. The surface features built up or deformed through plate tectonics are subject to steady weathering from precipitation, thermal cycles, and chemical effects. Glaciation, coastal erosion, the build-up of coral reefs, and large meteorite impacts[78] also act to reshape the landscape.


Present day Earth altimetry and bathymetry. Data from the National Geophysical Data Center's TerrainBase Digital Terrain Model.The continental crust consists of lower density material such as the igneous rocks granite and andesite. Less common is basalt, a denser volcanic rock that is the primary constituent of the ocean floors.[79] Sedimentary rock is formed from the accumulation of sediment that becomes compacted together. Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form only about 5% of the crust.[80] The third form of rock material found on Earth is metamorphic rock, which is created from the transformation of pre-existing rock types through high pressures, high temperatures, or both. The most abundant silicate minerals on the Earth's surface include quartz, the feldspars, amphibole, mica, pyroxene and olivine.[81] Common carbonate minerals include calcite (found in limestone), aragonite and dolomite.[82]

The pedosphere is the outermost layer of the Earth that is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. Currently the total arable land is 13.31% of the land surface, with only 4.71% supporting permanent crops.[7] Close to 40% of the Earth's land surface is presently used for cropland and pasture, or an estimated 1.3 × 107 km² of cropland and 3.4 × 107 km² of pastureland.[83]

The elevation of the land surface of the Earth varies from the low point of −418 m at the Dead Sea, to a 2005-estimated maximum altitude of 8,848 m at the top of Mount Everest. The mean height of land above sea level is 840 m.[84]

Hydrosphere
Main article: Hydrosphere

Elevation histogram of the surface of the Earth. Approximately 71% of the Earth's surface is covered with water.The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from others in the Solar System. The Earth's hydrosphere consists chiefly of the oceans, but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 m. The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean with a depth of −10,911.4 m.[note 12][85] The average depth of the oceans is 3,800 m, more than four times the average height of the continents.[84]

The mass of the oceans is approximately 1.35 × 1018 metric tons, or about 1/4400 of the total mass of the Earth, and occupies a volume of 1.386 × 109 km3. If all of the land on Earth were spread evenly, water would rise to an altitude of more than 2.7 km.[note 13] About 97.5% of the water is saline, while the remaining 2.5% is fresh water. The majority of the fresh water, about 68.7%, is currently in the form of ice.[86]

About 3.5% of the total mass of the oceans consists of salt. Most of this salt was released from volcanic activity or extracted from cool, igneous rocks.[87] The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms.[88] Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir.[89] Shifts in the oceanic temperature distribution can cause significant weather shifts, such as the El Niño-Southern Oscillation.[90]

Atmosphere
Main article: Earth's atmosphere
The atmospheric pressure on the surface of the Earth averages 101.325 kPa, with a scale height of about 8.5 km.[8] It is 78% nitrogen and 21% oxygen, with trace amounts of water vapor, carbon dioxide and other gaseous molecules. The height of the troposphere varies with latitude, ranging between 8 km at the poles to 17 km at the equator, with some variation due to weather and seasonal factors.[91]

Earth's biosphere has significantly altered its atmosphere. Oxygenic photosynthesis evolved 2.7 billion years ago, forming the primarily nitrogen-oxygen atmosphere that exists today. This change enabled the proliferation of aerobic organisms as well as the formation of the ozone layer which, together with Earth's magnetic field, blocks ultraviolet solar radiation, permitting life on land. Other atmospheric functions important to life on Earth include transporting water vapor, providing useful gases, causing small meteors to burn up before they strike the surface, and moderating temperature.[92] This last phenomenon is known as the greenhouse effect: trace molecules within the atmosphere serve to capture thermal energy emitted from the ground, thereby raising the average temperature. Carbon dioxide, water vapor, methane and ozone are the primary greenhouse gases in the Earth's atmosphere. Without this heat-retention effect, the average surface temperature would be −18 °C and life would likely not exist.[77]

Weather and climate
Main articles: Weather and Climate
The Earth's atmosphere has no definite boundary, slowly becoming thinner and fading into outer space. Three-quarters of the atmosphere's mass is contained within the first 11 km of the planet's surface. This lowest layer is called the troposphere. Energy from the Sun heats this layer, and the surface below, causing expansion of the air. This lower density air then rises, and is replaced by cooler, higher density air. The result is atmospheric circulation that drives the weather and climate through redistribution of heat energy.[93]

The primary atmospheric circulation bands consist of the trade winds in the equatorial region below 30° latitude and the westerlies in the mid-latitudes between 30° and 60°.[94] Ocean currents are also important factors in determining climate, particularly the thermohaline circulation that distributes heat energy from the equatorial oceans to the polar regions.[95]


Source regions of global air massesWater vapor generated through surface evaporation is transported by circulatory patterns in the atmosphere. When atmospheric conditions permit an uplift of warm, humid air, this water condenses and settles to the surface as precipitation.[93] Most of the water is then transported back to lower elevations by river systems, usually returning to the oceans or being deposited into lakes. This water cycle is a vital mechanism for supporting life on land, and is a primary factor in the erosion of surface features over geological periods. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter. Atmospheric circulation, topological features and temperature differences determine the average precipitation that falls in each region.[96]

The Earth can be sub-divided into specific latitudinal belts of approximately homogeneous climate. Ranging from the equator to the polar regions, these are the tropical (or equatorial), subtropical, temperate and polar climates.[97] Climate can also be classified based on the temperature and precipitation, with the climate regions characterized by fairly uniform air masses. The commonly used Köppen climate classification system (as modified by Wladimir Köppen's student Rudolph Geiger) has five broad groups (humid tropics, arid, humid middle latitudes, continental and cold polar), which are further divided into more specific subtypes.[94]

Upper atmosphere

This view from orbit shows the full Moon partially obscured by the Earth's atmosphere. NASA image.See also: Outer space
Above the troposphere, the atmosphere is usually divided into the stratosphere, mesosphere, and thermosphere.[92] Each of these layers has a different lapse rate, defining the rate of change in temperature with height. Beyond these, the exosphere thins out into the magnetosphere. This is where the Earth's magnetic fields interact with the solar wind.[98] An important part of the atmosphere for life on Earth is the ozone layer, a component of the stratosphere that partially shields the surface from ultraviolet light. The Kármán line, defined as 100 km above the Earth's surface, is a working definition for the boundary between atmosphere and space.[99]

Due to thermal energy, some of the molecules at the outer edge of the Earth's atmosphere have their velocity increased to the point where they can escape from the planet's gravity. This results in a slow but steady leakage of the atmosphere into space. Because unfixed hydrogen has a low molecular weight, it can achieve escape velocity more readily and it leaks into outer space at a greater rate than other gasses.[100] The leakage of hydrogen into space is a contributing factor in pushing the Earth from an initially reducing state to its current oxidizing one. Photosynthesis provided a source of free oxygen, but the loss of reducing agents such as hydrogen is believed to have been a necessary precondition for the widespread accumulation of oxygen in the atmosphere.[101] Hence the ability of hydrogen to escape from the Earth's atmosphere may have influenced the nature of life that developed on the planet.[102] In the current, oxygen-rich atmosphere most hydrogen is converted into water before it has an opportunity to escape. Instead, most of the hydrogen loss comes from the destruction of methane in the upper atmosphere.[103]

Magnetic field

The Earth's magnetic field, which approximates a dipole.Main article: Earth's magnetic field
The Earth's magnetic field is shaped roughly as a magnetic dipole, with the poles currently located proximate to the planet's geographic poles. According to dynamo theory, the field is generated within the molten outer core region where heat creates convection motions of conducting materials, generating electric currents. These in turn produce the Earth's magnetic field. The convection movements in the core are chaotic in nature, and periodically change alignment. This results in field reversals at irregular intervals averaging a few times every million years. The most recent reversal occurred approximately 700,000 years ago.[104][105]

The field forms the magnetosphere, which deflects particles in the solar wind. The sunward edge of the bow shock is located at about 13 times the radius of the Earth. The collision between the magnetic field and the solar wind forms the Van Allen radiation belts, a pair of concentric, torus-shaped regions of energetic charged particles. When the plasma enters the Earth's atmosphere at the magnetic poles, it forms the aurora.[106]


Orbit and rotation
Rotation
Main article: Earth's rotation

Earth's axial tilt (or obliquity) and its relation to the rotation axis and plane of orbit.Earth's rotation period relative to the Sun—its mean solar day—is 86,400 seconds of mean solar time. Each of these seconds is slightly longer than an SI second because Earth's solar day is now slightly longer than it was during the 19th century due to tidal acceleration.[107]

Earth's rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86164.098903691 seconds of mean solar time (UT1), or 23h 56m 4.098903691s. [108][note 14] Earth's rotation period relative to the precessing or moving mean vernal equinox, misnamed its sidereal day, is 86164.09053083288 seconds of mean solar time (UT1) (23h 56m 4.09053083288s).[108] Thus the sidereal day is shorter than the stellar day by about 8.4 ms.[109] The length of the mean solar day in SI seconds is available from the IERS for the periods 1623–2005[110] and 1962–2005.[111]

Apart from meteors within the atmosphere and low-orbiting satellites, the main apparent motion of celestial bodies in the Earth's sky is to the west at a rate of 15°/h = 15'/min. This is equivalent to an apparent diameter of the Sun or Moon every two minutes; the apparent sizes of the Sun and the Moon are approximately the same.[112][113]

Orbit
Main article: Earth's orbit
Earth orbits the Sun at an average distance of about 150 million kilometers every 365.2564 mean solar days, or one sidereal year. From Earth, this gives an apparent movement of the Sun eastward with respect to the stars at a rate of about 1°/day, or a Sun or Moon diameter every 12 hours. Because of this motion, on average it takes 24 hours—a solar day—for Earth to complete a full rotation about its axis so that the Sun returns to the meridian. The orbital speed of the Earth averages about 30 km/s (108,000 km/h), which is fast enough to cover the planet's diameter (about 12,600 km) in seven minutes, and the distance to the Moon (384,000 km) in four hours.[8]

The Moon revolves with the Earth around a common barycenter every 27.32 days relative to the background stars. When combined with the Earth–Moon system's common revolution 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 counter-clockwise. Viewed from a vantage point above the north poles of both the Sun and the Earth, the Earth appears to revolve in a counterclockwise direction about the Sun. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.5 degrees from the perpendicular to the Earth–Sun plane, and the Earth–Moon plane is tilted about 5 degrees against the Earth-Sun plane. Without this tilt, there would be an eclipse every two weeks, alternating between lunar eclipses and solar eclipses.[8][114]

The Hill sphere, or gravitational sphere of influence, of the Earth is about 1.5 Gm (or 1,500,000 kilometers) in radius.[115][note 15] This is maximum distance at which the Earth's gravitational influence is stronger than the more distant Sun and planets. Objects must orbit the Earth within this radius, or they can become unbound by the gravitational perturbation of the Sun.


Illustration of the Milky Way Galaxy, showing the location of the Sun.Earth, along with the Solar System, is situated in the Milky Way galaxy, orbiting about 28,000 light years from the center of the galaxy. It is currently about 20 light years above the galaxy's equatorial plane in the Orion spiral arm.[116]

Axial tilt and seasons
Main article: Axial tilt
Because of the axial tilt of the Earth, the amount of sunlight reaching any given point on the surface varies over the course of the year. This results in seasonal change in climate, with summer in the northern hemisphere occurring when the North Pole is pointing toward the Sun, and winter taking place when the pole is pointed away. During the summer, the day lasts longer and the Sun climbs higher in the sky. In winter, the climate becomes generally cooler and the days shorter. Above the Arctic Circle, an extreme case is reached where there is no daylight at all for part of the year—a polar night. In the southern hemisphere the situation is exactly reversed, with the South Pole oriented opposite the direction of the North Pole.


Earth and Moon from Mars, imaged by Mars Global Surveyor. From space, the Earth can be seen to go through phases similar to the phases of the Moon.By astronomical convention, the four seasons are determined by the solstices—the point in the orbit of maximum axial tilt toward or away from the Sun—and the equinoxes, when the direction of the tilt and the direction to the Sun are perpendicular. Winter solstice occurs on about December 21, summer solstice is near June 21, spring equinox is around March 20 and autumnal equinox is about September 23.[117]

The angle of the Earth's tilt is relatively stable over long periods of time. However, the tilt does undergo nutation; a slight, irregular motion with a main period of 18.6 years. The orientation (rather than the angle) of the Earth's axis also changes over time, precessing around in a complete circle over each 25,800 year cycle; this precession is the reason for the difference between a sidereal year and a tropical year. Both of these motions are caused by the varying attraction of the Sun and Moon on the Earth's equatorial bulge. From the perspective of the Earth, the poles also migrate a few meters across the surface. This polar motion has multiple, cyclical components, which collectively are termed quasiperiodic motion. In addition to an annual component to this motion, there is a 14-month cycle called the Chandler wobble. The rotational velocity of the Earth also varies in a phenomenon known as length of day variation.[118]

In modern times, Earth's perihelion occurs around January 3, and the aphelion around July 4. However, these dates change over time due to precession and other orbital factors, which follow cyclical patterns known as Milankovitch cycles. The changing Earth-Sun distance results in an increase of about 6.9%[119] in solar energy reaching the Earth at perihelion relative to aphelion. Since the southern hemisphere is tilted toward the Sun at about the same time that the Earth reaches the closest approach to the Sun, the southern hemisphere receives slightly more energy from the Sun than does the northern over the course of a year. However, this effect is much less significant than the total energy change due to the axial tilt, and most of the excess energy is absorbed by the higher proportion of water in the southern hemisphere.[120]

Moon
Characteristics Diameter 3,474.8 km
2,159.2 mi
Mass 7.349 × 1022 kg
8.1 × 1019 (short) tons
Semi-major axis 384,400 km
238,700 mi
Orbital period 27 d 7 h 43.7 m
Main article: Moon
The Moon is a relatively large, terrestrial, planet-like satellite, with a diameter about one-quarter of the Earth's. It is the largest moon in the Solar System relative to the size of its planet. (Charon is larger relative to the dwarf planet Pluto.) The natural satellites orbiting other planets are called "moons" after Earth's Moon.

The gravitational attraction between the Earth and Moon causes tides on Earth. The same effect on the Moon has led to its tidal locking: its rotation period is the same as the time it takes to orbit the Earth. As a result, it always presents the same face to the planet. As the Moon orbits Earth, different parts of its face are illuminated by the Sun, leading to the lunar phases; the dark part of the face is separated from the light part by the solar terminator.

Because of their tidal interaction, the Moon recedes from Earth at the rate of approximately 38 mm a year. Over millions of years, these tiny modifications—and the lengthening of Earth's day by about 23 µs a year—add up to significant changes.[121] During the Devonian period, for example, (approximately 410 million years ago) there were 400 days in a year, with each day lasting 21.8 hours.[122]

The Moon may have dramatically affected the development of life by moderating the planet's climate. Paleontological evidence and computer simulations show that Earth's axial tilt is stabilized by tidal interactions with the Moon.[123] Some theorists believe that without this stabilization against the torques applied by the Sun and planets to the Earth's equatorial bulge, the rotational axis might be chaotically unstable, exhibiting chaotic changes over millions of years, as appears to be the case for Mars.[124] If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result from the resulting extreme seasonal differences. One pole would be pointed directly toward the Sun during summer and directly away during winter. Planetary scientists who have studied the effect claim that this might kill all large animal and higher plant life.[125] However, this is a controversial subject, and further studies of Mars—which has a similar rotation period and axial tilt as Earth, but not its large Moon or liquid core—may settle the matter.

Viewed from Earth, the Moon is just far enough away to have very nearly the same apparent-sized disk as the Sun. The angular size (or solid angle) of these two bodies match because, although the Sun's diameter is about 400 times as large as the Moon's, it is also 400 times more distant.[113] This allows total and annular eclipses to occur on Earth.



A scale representation of the relative sizes of, and distance between, Earth and Moon.
The most widely accepted theory of the Moon's origin, the giant impact theory, states that it formed from the collision of a Mars-size protoplanet called Theia with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements, and the fact that its composition is nearly identical to that of the Earth's crust.[126]

Earth has at least two co-orbital asteroids, 3753 Cruithne and 2002 AA29.[127]

Habitability
See also: Planetary habitability

A range of theoretical habitable zones with stars of different mass (our Solar System at center). Not to scale.A planet that can sustain life is termed habitable, even if life did not originate there. The Earth provides the (currently understood) requisite conditions of liquid water, an environment where complex organic molecules can assemble, and sufficient energy to sustain metabolism.[128] The distance of the Earth from the Sun, as well as its orbital eccentricity, rate of rotation, axial tilt, geological history, sustaining atmosphere and protective magnetic field all contribute to the conditions necessary to originate and sustain life on this planet.[129]

Biosphere
Main article: Biosphere
The planet's life forms are sometimes said to form a "biosphere". This biosphere is generally believed to have begun evolving about 3.5 billion years ago. Earth is the only place in the universe where life is known to exist. Some scientists believe that Earth-like biospheres might be rare.[130]

The biosphere is divided into a number of biomes, inhabited by broadly similar plants and animals. On land primarily latitude and height above the sea level separates biomes. Terrestrial biomes lying within the Arctic, Antarctic Circle or in high altitudes are relatively barren of plant and animal life, while the greatest latitudinal diversity of species is found at the Equator.[131]

Natural resources and land use
Main article: Natural resource
The Earth provides resources that are exploitable by humans for useful purposes. Some of these are non-renewable resources, such as mineral fuels, that are difficult to replenish on a short time scale.

Large deposits of fossil fuels are obtained from the Earth's crust, consisting of coal, petroleum, natural gas and methane clathrate. These deposits are used by humans both for energy production and as feedstock for chemical production. Mineral ore bodies have also been formed in Earth's crust through a process of Ore genesis, resulting from actions of erosion and plate tectonics.[132] These bodies form concentrated sources for many metals and other useful elements.

The Earth's biosphere produces many useful biological products for humans, including (but far from limited to) food, wood, pharmaceuticals, oxygen, and the recycling of many organic wastes. The land-based ecosystem depends upon topsoil and fresh water, and the oceanic ecosystem depends upon dissolved nutrients washed down from the land.[133] Humans also live on the land by using building materials to construct shelters. In 1993, human use of land is approximately:

Land use Percentage
Arable land 13.13%[7]
Permanent crops 4.71%[7]
Permanent pastures 26%
Forests and woodland 32%
Urban areas 1.5%
Other 30%

The estimated amount of irrigated land in 1993 was 2,481,250 km².[7]

Natural and environmental hazards
Large areas are subject to extreme weather such as tropical cyclones, hurricanes, or typhoons that dominate life in those areas. Many places are subject to earthquakes, landslides, tsunamis, volcanic eruptions, tornadoes, sinkholes, blizzards, floods, droughts, and other calamities and disasters.

Many localized areas are subject to human-made pollution of the air and water, acid rain and toxic substances, loss of vegetation (overgrazing, deforestation, desertification), loss of wildlife, species extinction, soil degradation, soil depletion, erosion, and introduction of invasive species.

A scientific consensus exists linking human activities to global warming due to industrial carbon dioxide emissions. This is predicted to produce changes such as the melting of glaciers and ice sheets, more extreme temperature ranges, significant changes in weather conditions and a global rise in average sea levels.[134]

Human geography
Main article: Human geography
See also: World

Cartography, the study and practice of map making, and vicariously geography, have historically been the disciplines devoted to depicting the Earth. Surveying, the determination of locations and distances, and to a lesser extent navigation, the determination of position and direction, have developed alongside cartography and geography, providing and suitably quantifying the requisite information.

Earth has approximately 6,740,000,000 human inhabitants as of November 2008.[135] Projections indicate that the world's human population will reach seven billion in 2013 and 9.2 billion in 2050.[136] Most of the growth is expected to take place in developing nations. Human population density varies widely around the world, but a majority live in Asia. By 2020, 60% of the world's population is expected to be living in urban, rather than rural, areas.[137]

It is estimated that only one eighth of the surface of the Earth is suitable for humans to live on—three-quarters is covered by oceans, and half of the land area is either desert (14%),[138] high mountains (27%),[139] or other less suitable terrain. The northernmost permanent settlement in the world is Alert, on Ellesmere Island in Nunavut, Canada.[140] (82°28′N) The southernmost is the Amundsen-Scott South Pole Station, in Antarctica, almost exactly at the South Pole. (90°S)


The Earth at night, a composite of DMSP/OLS ground illumination data on a simulated night-time image of the world. This image is not photographic and many features are brighter than they would appear to a direct observer.Independent sovereign nations claim the planet's entire land surface, with the exception of some parts of Antarctica. As of 2007 there are 201 sovereign states, including the 192 United Nations member states. In addition, there are 59 dependent territories, and a number of autonomous areas, territories under dispute and other entities.[7] Historically, Earth has never had a sovereign government with authority over the entire globe, although a number of nation-states have striven for world domination and failed.[141]

The United Nations is a worldwide intergovernmental organization that was created with the goal of intervening in the disputes between nations, thereby avoiding armed conflict.[142] It is not, however, a world government. While the U.N. provides a mechanism for international law and, when the consensus of the membership permits, armed intervention,[143] it serves primarily as a forum for international diplomacy.

The first human to orbit the Earth was Yuri Gagarin on April 12, 1961.[144] In total, about 400 people visited outer space and reached Earth orbit as of 2004, and, of these, twelve have walked on the Moon.[145][146][147] Normally the only humans in space are those on the International Space Station. The station's crew, currently six people, is usually replaced every six months.[148] Humans traveled the farthest from the planet in 1970, when Apollo 13 crew was 400,171 km away from Earth.[149][150]


Cultural viewpoint
Main article: Earth in culture

The first photograph ever taken by astronauts of an "Earthrise", from Apollo 8The name "Earth" was derived from the Anglo-Saxon word erda, which means ground or soil. It became eorthe in Old English, then erthe in Middle English.[151] The standard astronomical symbol of the Earth consists of a cross circumscribed by a circle.[152]

Earth has often been personified as a deity, in particular a goddess. In many cultures the mother goddess, also called the Mother Earth, is also portrayed as a fertility deity. Creation myths in many religions recall a story involving the creation of the Earth by a supernatural deity or deities. A variety of religious groups, often associated with fundamentalist branches of Protestantism[153] or Islam,[154] assert that their interpretations of these creation myths in sacred texts are literal truth and should be considered alongside or replace conventional scientific accounts of the formation of the Earth and the origin and development of life.[155] Such assertions are opposed by the scientific community[156][157] and other religious groups.[158][159][160] A prominent example is the creation-evolution controversy.

In the past there were varying levels of belief in a flat Earth,[161] but this was displaced by the concept of a spherical Earth due to observation and circumnavigation.[162] The human perspective regarding the Earth has changed following the advent of spaceflight, and the biosphere is now widely viewed from a globally integrated perspective.[163][164] This is reflected in a growing environmental movement that is concerned about humankind's effects on the planet

What is peace?

Peace has always been among humanity's highest values--for some, supreme. Consider: "Peace at any price."1 "The most disadvantageous peace is better than the most just war."2 "Peace is more important than all justice."3 "I prefer the most unjust peace to the justest war that was ever waged."4 "There never was a good war or a bad peace."5
Yet, we agree little on what is peace. Perhaps the most popular (Western) view is as an absence of dissension, violence, or war, a meaning found in the New Testament and possibly an original meaning of the Greek word for peace, Irene. Pacifists have adopted this interpretation, for to them all violence is bad. This meaning is widely accepted among irenologists6 and students of international relations. It is the primary dictionary definition.

Peace, however, is also seen as concord, or harmony and tranquility. It is viewed as peace of mind or serenity, especially in the East. It is defined as a state of law or civil government, a state of justice or goodness, a balance or equilibrium of Powers.

Such meanings of peace function at different levels. Peace may be opposed to or an opposite of antagonistic conflict, violence, or war. It may refer to an internal state (of mind or of nations) or to external relations. Or it may be narrow in conception, referring to specific relations in a particular situation (like a peace treaty), or overarching, covering a whole society (as in a world peace). Peace may be a dichotomy (it exists or it does not) or continuous, passive or active, empirical or abstract, descriptive or normative, or positive or negative.

The problem is, of course, that peace derives its meaning and qualities within a theory or framework. Christian, Hindu, or Buddhist will see peace differently, as will pacifist or internationalist. Socialist, fascist, and libertarian have different perspectives, as do power or idealistic theorists of international relations. In this diversity of meanings, peace is no different from such concepts as justice, freedom, equality, power, conflict, class, and, indeed, any other concept.

All concepts are defined within a theory or cognitive framework--what I have called elsewhere a perspective.7 Through a perspective peace is endowed with meaning by being linked to other concepts within a particular perception of reality; and by its relationship to ideas or assumptions about violence, history, divine grace, justice. Peace is thereby locked into a descriptive or explanatory view of our reality and each other.

My perspective, which sees peace as a phase in a conflict helix, an equilibrium within a social field, has been presented in the previous four volumes.7a In this Chapter I will review this perspective, make clear the imbedded meaning of peace, describe its related qualities and dimensions, and prepare for considering alternative conceptualizations in the next Chapter. This and Chapter 3 are thus the prologue to my subsequent theory of a just peace.



2.2 PEACE AS A SOCIAL CONTRACT
My perspective and associated meaning of peace are best summarized through a number of social principles. These have been documented and the evidence given for them elsewhere,8 as will be noted for each.




2.2.1 The Conflict Principle
Conflict is a balancing of powers among interests, capabilities, and wills.9 It is a mutual adjusting of what people want, can get, and are willing to pursue. Conflict behavior, whether hostile actions, violence, or war, is then a means and manifestation of this process.




2.2.2 The Cooperation Principle
Cooperation depends on expectations aligned with power. Through conflict in a specific situation, a balance of powers and associated agreement are achieved. This balance is a definite equilibrium among the parties' interests, capabilities, and wills; the agreement is a simultaneous solution to the different equations of power, and thereby the achievement of a certain harmony--structure--of expectations. At the core of this structure is a status quo, or particular expectations over rights and obligations. Conflict thus interfaces and interlocks a specific balance of powers and an associated structure of expectations.

Cooperation--contractual or familistic interactions10--depends on a harmony of expectations, a mutual ability of the parties to predict the outcome of their behavior. Such is, for example, the major value of a written contract or treaty. And this structure of expectations depends on a particular balance of powers.11 Thus, cooperation depends on expectations aligned with power.




2.2.3 The Gap Principle
A gap between expectations and power causes conflict. A structure of expectations, once established, has considerable social inertia, while the supporting balance of powers can change rapidly. Interests can shift, new capabilities can develop, wills can strengthen or weaken. As the underlying balance of powers changes, a gap between power and the structure of expectations can form, causing the associated agreement to lose support. The larger this gap, the greater the tension toward revising expectations in line with the change in power, and thus the more likely some random event will trigger conflict over the associated interests. Such conflict then serves to create a new congruence between expectations and power.

Conflict and cooperation therefore are interdependent. They are alternative phases in a continuous social process12 underlying human interaction: now conflict, then cooperation, and then again conflict.13 Cooperation involves a harmony of expectations congruent with a balance of powers achieved by conflict.



2.2.4 The Helix Principle
Conflict becomes less intense, cooperation14 more lasting. If interaction occurs in a closed system or is free from sudden, sharp changes in the conditions of a relationship (as, for example, if one party to a business contract goes bankrupt, or a signatory to a regional military alliance with the United States has a military coup), then through conflict and cooperation people gradually learn more about each other, their mutual adjustments come easier, their expectations more harmonious and lasting. Conflict and cooperation thus form a helix, moving upward on a curve of learning and adjustments, with the turn through cooperation being more familistic and durable; that through conflict shorter and less intense.15



2.2.5 The Second and Fourth Master Principles
Through conflict is negotiated a social contract.16 As mentioned, conflict is a balancing of powers--a conscious or subconscious negotiation of opposing interests, capabilities, and wills. This process determines some implicit or explicit, subconscious or conscious social contract. It is social in involving a relationship or interaction between two or more wills. It is a contract in that there is an agreement--a harmonization of expectations.
It is this social contract that is peace within social field theory. Peace, then is determined by a process of adjustment between what people, groups, or states want, can, and will do. Peace is based on a consequent balance of powers and involves a corresponding structure of expectations and patterns of cooperation. Moreover, peace may become unstable when an increasing gap develops between expectations and power, as here defined,17 and may collapse into conflict, violence, or war.





2.3 THE NATURE OF A SOCIAL CONTRACT
Social contracts, the structural basis of peace as here defined, take many forms that interconnect and overlap in diverse, complex ways to order social communities and organizations. I can hardly engage here this variety, which would itself require a volume.18 Rather, I shall simply outline the diversity of social contracts, especially so that the nested, overlapping, and multilayered nature of social contracts, and thus peace, is clear.
Throughout the following discussion three points should be kept in mind. First, as mentioned, a social contract is the outcome of parties balancing their mutual interests, capabilities, and wills, and is based on a particular balance thus achieved--a balance of powers.

Second, the powers constituting the balance are not necessarily coercive or authoritative; threat or legitimacy are not the only bases for social contracts. Altruistic, intellectual, or exchange powers (based on love, persuasion, or promises, respectively) may dominate. Thus, a social contract may be a marriage agreement, an understanding developed among scientists over a disputed theory, or a sale in a market.19

Third, a social contract--this peace--is only a phase in a conflict helix and is thus a temporary equilibrium in the long-term movement of interpersonal, social, or international relations.




2.3.1 Expectations
As used here, an expectation is a prediction about the outcome of one's behavior.20 A social contract harmonizes certain expectations between the parties; that is, it enables each to reliably predict the other's responses. Such expectations are varied; our vocabulary for discriminating among them is well developed. Remembering my fundamental concern with social peace and conflict (and thus I am uninterested in, for example, a legal classification of contracts), these can be divided into status quo and non-status quo expectations. Within these two divisions I can define five types, as shown in Table 2.1.






A. Status quo. The concept of status quo is basic to these volumes. In previous volumes21 I argued that a breakdown of status quo expectations is a necessary cause of violence and war, and I tried to verify this against empirical results.22 The reason for this necessity is that status quo expectations define the basic rights and obligations of the parties involved, and therefore affect vital values. These rights and obligations form the two types of status quo expectations. As Table 2.1 shows, they involve claims, privileges, responsibilities, duties, and so on. Note especially that expectations about property--who owns what--are part of the status quo.

Obviously, the division between status quo and non-status quo expectations is not clear-cut. The criterion of discrimination is salience to fundamental values, and thus intensity of feeling and commitment. For example, agreements over property (such as territory) will usually involve strong emotion and commitment, while agreed upon rules or practices, advantages or benefits are less vital and violations more tolerable. However, we are dealing here with a great complexity of social contracts and the subjectivity of underlying interests, meanings, and values. In some situations a rule, payment, or service may be a life-or-death matter or a question of fundamental principle to the parties involved and thus, for this case, a matter of the status quo. Therefore, the classification of expectations under status quo or non-status quo divisions in Table 2.1 simply attempts to make intelligible the diversity of expectations, rather than to construct conceptually tight demarcations covering all possibilities.

B. Non-Status Quo. One type of non-status quo expectations is distributional, establishing which party can anticipate what from whom, such as benefits, advantages, and services. The two remaining types guide or prescribe behavior between the parties. The social contract often includes rules, customs, or practices that provide standards or define customary or repeated actions. Such may be commands, authoritative standards, or principles of right actions. They may be binding, acting to control or regulate behavior. Such prescriptive expectations in social contracts are mores (long-term, morally binding customs), norms, the law-norms of groups,23 or the customary or positive law of societies or states. Even the "rules of morality constitute a tacit social contract" (Hazlitt, 1964: xii).

C. Overall. Regardless of whether the focus is the rights or obligations, the distributions, or the guides or prescriptions between parties structured by their social contract, these expectations share one characteristic: they circumscribe a region of predictability, or social certainty, between the parties. With a social contract, each party can reliably foresee and plan on the outcome of its behavior regarding the other, as over, for example, claims, privileges, duties, or services. What responses to anticipate, the prospect of reciprocity, the likelihood of particular sanctions, are clear. Social contracts are thus our social organs of peace, extending into the future mutual paths of social certainty and thus confidence.




2.3.2 Theoretical Dimensions

A. Actuality. In Table 2.2 I list 11 theoretical dimensions along which social contracts vary, and have organized them into four general types.24 To begin with, social contracts may be informal, as are unwritten understandings between friends or allies; or they may be formal, as with treaties. They may be implicit, tacit agreements that the parties choose not to mention, as a wife's acceptance of her husband's affairs; or they may be explicit, such as a verbal contract. They may be subconscious, as when co-workers unconsciously avoid sensitive topics over which they might fight. Or, of course, the social contract may be conscious.

These three dimensions--in formal versus formal, implicit versus explicit, and subconscious versus conscious--concern the actuality of social contracts, whether they are a latent agreement underlying social behavior or a manifest compact of some kind.25 A fourth, quite important dimension defines how a social contract is manifested.

A direct social contract is a specific agreement between particular parties. It gives or implies names, dates, places, and definite expectations. Contracts are usually thought of as this kind, such as a construction contract between two firms or a trade treaty among three states. However, direct contracts may overlap or be interconnected through the different parties, and thus form a system of contracts. And these systems themselves may overlap and be interdependent. Out of these diverse, interconnected, and related direct contracts and systems of contracts will develop more general expectations, such as abstract rules, norms, or privileges at the level of the social system itself. No one will have agreed to these expectations per se, nor are they connected to any particular interest, but they nonetheless comprise a social contract (albeit an indirect one) covering the social system. The prices of goods in a free market comprise such an indirect social contract evolving from the diverse direct contracts between buyers and sellers.26 In Section 2.3.3 I will present some of the major forms direct contracts may take; in subsequent sections I will describe several orders of direct and indirect contracts.

B. Generality. A second type of theoretical dimension delineates a social contract's generality. One such dimension concerns whether a contract is unique or common. A unique social contract is a one-time-only agreement within a unique situation and concerning nonrepetitive events or interaction between the parties. Such is the implicit agreement wrought in an alley by a thug, whose knife coerces you to hand over your money; another example is a two-hour ceasefire agreement to enable combatants to clear the battlefield of wounded, or a neutral state granting American relief planes a once-only flyover to rush food and medicine to earthquake victims in a neighboring state. By contrast, a common social contract involves repeated events or patterns of interaction. Treaties, legal contracts, constitutions, and charters are usually of this type. Clearly, the unique-common dimension is a continuum, since between the unique two-minute holdup and the common, overriding political constitution of a state are a variety of social contracts combining in different ways unique and common expectations.

Turning to the second generality dimension shown in Table 2.2, social contracts may be bilateral, involving only two parties, multilateral in covering more than two parties, or collective. The latter covers a society, community, or a group. Constitutions or charters are of this type, as are an organization's bylaws. While this may seem clear enough, there is an intellectual trap to avoid here--that of always viewing collective social contracts as necessarily constructed, designed, or the explicit and conscious outcome of a rational process of negotiation.27 Collective contracts also may emerge from the interwoven, multilayered, bilateral and multilateral social contracts crisscrossing a society. The integrated system of abstract rules, norms, mores, and customs spanning a society form an indirect, collective social contract. It is implicit and informal; its expectations are partly conscious, partly unconscious. The system of informal rules of the road is such a collective agreement governing, along with coextensive formal traffic laws, a community of drivers.

While no group of people may have formally or consciously agreed to a collective social contract--while such may emerge from various, lower-level social contracts, many of which are conscious agreements--it is still based on a particular balance of powers, now involving all members of the collective. Consider, for example, the historically rapid dissolution and restructuring of collective expectations involving rules, customs, and laws that have occurred as a result of conquest (such as Latvia, Lithuania, and Estonia conquered and absorbed by the Soviet Union in 1939), of military defeat and occupation (as of Hitler's national socialist, totalitarian Germany), or revolution (witness the French and Russian Revolutions, or the 1974-1978 Cambodian social revolution of the Khmer Rouge). Of course, not all norms, customs, or customary laws are changed, no more than a new bilateral or multilateral contract will discard all previous expectations. New social contracts build on the old. However, a new social contract, collective or otherwise, will be meaningfully different; associated interaction between the parties will change significantly.

Finally, the third dimension defining a contract's generality may be narrow, middle range, or overarching. A narrow contract concerns only a few interests, events, or behaviors, such as a contract to paint a car, a trade treaty increasing the quota on imported sugar, or the price of a Sony television set.28 An overarching contract develops from, refers to, or spans a whole system of relationships, such as those of a family, the larger society, or an organization. A marriage contract stipulating duties and rights of spouses, an organization's constitution, or the system of norms covering a society are some examples. Between the narrow and overarching are a variety of middlerange social contracts covering or involving a large amount of behavior, but not the whole society. One's work contract, an alliance between states, and a peace treaty are examples in this middle range.

C. Polarity. The third type of dimension shown in Table 2.2 concerns a social contract's polarity. In the dimension of coerciveness, the parties to social contract may voluntarily accept it, or one or more parties may be coerced into it, either by other parties to the contract or by a third party, such as in a shotgun wedding or governmentally imposed, union-management contract. Between freely determined and coerced contracts are those which one or more parties agree to out of necessity. That is, circumstances, the environment, or events leave virtually no realistic or practical choice. In a one-company mining town where a person has his roots, he may have little, socially meaningful choice but to contract for work with the company. To defeat Hitler in the Second World War, Churchill felt he had little choice but to form an alliance with Stalin.

A second polarity-type dimension concerns whether a social contract is solidary, neutral, or antagonistic.29 Solidary expectations derive from helpful, altruistic, or compassionate behavior. Such expectations are common among close friends or relations, lovers, or close-knit communal or religious groups. Antagonistic expectations, however, derive from mutually competitive, divergent, or opposing behavior. They involve a perception of incompatible purposes, temporarily bound in a social contract, and a belief that satisfying one's interests entails frustrating those of the other parties. A labor-management contract achieved after a long, violent strike is such an antagonistic contract; or a truce between traditional enemies, such as Pakistan and India, North and South Korea, or Israel and Syria. Between solidary and antagonistic contracts lie neutral contracts,30 those which are strictly a matter of business, a question of the parties coolly and objectively satisfying rather specific interests. Examples are agreements for a bank loan, renting an apartment, importing cotton, or increasing the postage on international mail.

D. Evaluative. Finally, there is the evaluative dimension. One of these concerns whether a social contract is good or bad. Fundamental philosophical controversy centers on the idea of good. For the moment, I mean "good" simply in the sense that one might say a treaty is a good one because it has characteristics that one desires or believes rationally commendable or divinely inspired.31

A contract may be positive or negative in the same sense as "good" or "bad." There is a potential confusion in the use of these terms, however, since here a social contract equals peace. "Positive peace" has come to mean, especially among Scandinavian irenologists32 an existing or ideal social state, such as the achievement of individual potential, as reflected in social equality, for example. "Negative peace" is then simply the absence of violence. This, however, is a confusion of categories, and leads to such strange but consistent (by definition) expressions as "a positive, negative peace."33 Simply, I will mean positive as good and negative as bad in qualifying social contracts or peace.

A second evaluative dimension defines one kind of good social contract: whether it is just or unjust. It is this dimension of social contracts that is the major focus of this book. Understanding that a social contract defines a particular peace, my question is: What is a just peace? My answer, developed in Part II is that justice is the freedom of people to form their own communities or to leave undesirable ones . For large-scale societies, just peace is promoted through a minimum government.



--------------------------------------------------------------------------------

2.3.3 Forms




Table 2.3 presents major forms of direct social contracts. There is no need to describe each in detail here. Suffice to say that each is a structure of expectations based on a definite balance of interests, capabilities, and wills. Each is a social island of peace.



2.3.4 Social Orders
A social order is a particular arrangement of direct and indirect social contracts forming a meaningful, causal-functional34 whole. Two types of social orders are of concern here. One is that of groups; the other of societies.
A. Groups. A group is structured by a direct, overarching social contract that defines members' rights, obligations, and authoritative roles. Behavior is guided and prescribed by sanction-based law-norms. All this may be codified in organizing documents, such as a charter, constitution, or bylaws; or these may be informal, implicit, or even subconscious understandings and norms evolving from the spontaneous interaction and conflicts of group members, as in a family or clan.35

In any case, this social contract may be solidary, neutral, or antagonistic (as in family, work group, and prison, respectively); it may tightly organize members or leave them unorganized; and it may recruit members voluntarily, through coercion, or out of necessity. Group goals may be diffused or superordinate; the basis of authoritative roles may be legitimacy or threats. These diverse characteristics shape the five groups shown in Table 2.4.36





For my purposes here, the most important distinction is between spontaneous groups and voluntary associations on the one hand, and voluntary, quasi-coercive, and coercive organizations on the other. An organization is structured by an explicit, formal social contract aimed at achieving some superordinate goal (profit for a business, military victory for an army, segregating criminals for a prison, education for a university). Expectations are wrapped around this goal: it determines roles, rights, and obligations, as well as law-norms prescribing behavior. An organization is then an antifield.37 Spontaneous interaction is circumscribed, consigned to regions of social space (the interstices of the organizational chart) irrelevant to an organization's goals. By contrast, voluntary groups and associations are less organized, not as strongly directed toward some superordinate goal. Goals may even be absent, diffuse, or unarticulated. Coercion or authority play minor roles. Within these groups and associations field forces and processes have considerable freedom and scope, as in a family, friendship group, or neighborhood association.

These different groups define different structures of peace, different patterns of our interests and capabilities, of our powers.

B. Societies. The second kind of social order shown in Table 2.4 is the society. The three pure types listed have been discussed at length in Vol. 2: The Conflict Helix38 and their empirical validity was assessed there.39 Here, I need only note the more important relevancies.

A society is defined by a division of labor40 and, accordingly, certain shared meanings, values, and norms; social interaction; and a communication system. It is shaped by an indirect, overarching, collective structure of expectations--a mainly informal and implicit social contract. The form of social power primarily underlying this contract determines the type of society. An exchange society is dominated by exchange power; an authoritative society by authoritative power; a coercive society by coercion. By virtue of the dominating form of power and associated social dynamics, each society manifests a particular dimension of conflict, with exchange societies least violent; coercive, the most.41 Each type of society is thus a different kind of peaceful order.

International relations among societies are of special importance here. Nation-states form an exchange society42 with a libertarian government, pluralistic conflict,43 and associated pluralistic structure of peace. In later discussing international peace I will make use of this social fact.

C. Summary. I have shown the diversity of social contracts, and thus peace, through detailing their various expectations, dimensions, forms, and orders. I need only underline now the nested, overlapping, and hierarchical complex of such contracts filling out the structure of a group or society. Consider, for example, a voluntary organization such as a university. It has an overarching contract defining its purposes, organizational structure, positions, and attendant rights and obligations, and associated rules and law-norms. Under the cover of these expectations are defined related social contracts and systems of contracts governing separate administrative functions (such as admission and financial aid), colleges, divisions, and departments. Within the constraints of the university's overarching expectations, each contract or system has a certain life, depending on the administrators, deans, and faculty involved. Each teaching department within a college of division achieves its own informal or formal social contracts establishing rights, obligations, and privileges attendant upon faculty and student rank and defining the role of students and rules for judging issues before the department. As should be clear, each department, college, and administrative division will be an arena of conflict establishing or revising such expectations, although the overarching social contract that constitutes the university remains stable--a region of social peace at its level.

The university itself is within an overarching social contract that is the larger society. Families, Businesses, universities, governments, churches, are all are collective social contracts within society, which also includes the numberless bilateral and multilateral social contracts among groups, subgroups, and individuals and the collective contracts ordering subsocieties. Each social contract is a specific peace within a particular conflict helix; each may have within it lower-level conflict (for example, a state within a region of international peace may suffer internal guerrilla war and terrorism); each peace may exist within an ongoing, antagonistic conflict (as internally peaceful states engage in war).

Peace is therefore complex, multilayered. To say the least, discussing peace requires being specific about the social contract involved. To present a theory about a just peace demands clarity about the associated expectations, dimensions, and social orders.



2.4 CONCEPTUAL LEVELS AND DIMENSIONS OF PEACE
The dimensions, forms, and orders of social contracts described above are also, by definition, those of peace. What must be added here and in the next Section are additional distinctions not usually applied to social contracts but which help locate peace as a social contract among our diverse conceptualizations of peace. This and Section 2.5 also represent part of my effort at vocabulary building--developing in a systematic manner, and locating in one place, those terms applicable to peace that will be used in subsequent chapters.




Table 2.5 presents the conceptual level and dimensions of peace to be discussed here.





2.4.1 Conceptual Levels
A. Levels. Undoubtedly, peace is often conceptually opposed to war. Obviously, then, one conceptual level for analyzing a just peace involves those social contracts determined by international, civil, or revolutionary war.
Peace, however, especially among pacifists, is also opposed to violence. This includes war, of course, but additionally covers violent acts not ordinarily thought of or legally defined as war. Indeed, in the contemporary world legal war (that is, war as a legal state of relations invoking special international laws) is rare, while warlike violence is as intense and prevalent as wars were during past centuries. Nonetheless, this is more than a matter of defining war empirically. Many do feel that peace, conceptually, applies only to those human relations which exclude personal, organized, or collective violence.

Those opposing the idea of peace to violence or war usually see peace as an absence of such behavior. But a different view, especially in the East, sees peace as harmony, tranquility, concord. Peace is then conceptually opposed to nonviolent, antagonistic conflict, such as that manifesting threats and accusations, hostile quarrels, angry boycotts, and riotous demonstrations.

Another concept goes even further, seeing peace as absolute harmony, serenity, or quietude; that is, as opposed to any kind of conflict, antagonistic or otherwise. Conflict is a general concept meaning, in essence, a balancing of power,44 which may involve not only hostile or antagonistic balancing but also that of intellectual conflict (as in friendly disagreement over facts), bargaining conflict (as in haggling over a sale price), or a lover's conflict (as when each tries to give the other the choice of a movie to see). Each of these conflicts ends in a social contract, and therefore in a kind of peace. I mention this conceptual level for completeness, however. My conceptual focus here, as for all irenologists, will be on peace at the level of antagonistic conflict, whether violent or not.

B. A Threshold. Especially significant for a theory of just peace is the distinction between nonviolent, antagonistic conflict on one side and violence on the other. There is an empirical threshold here. As I will argue later in Section 7.4.2 and Section 8.2, the conditions for a just peace at the level of violence will increase the amount of nonviolent conflict. A just peace free from long-term violence is, at the level of societies at least, only possible at the price of peace from nonviolent conflict.





2.4.2 Social Levels
A. Levels. Clearly, peace as a social contract occurs at different levels of social relationships. Table 2.5 lists four of concern here. One is international, the level of most historical concern about peace. A second level concerns the central government or ruling power (such as a dominant religious leader or political party) of a state. Peace here is the outcome of, or can disintegrate into, revolution or civil war; guerrilla war and terrorism; political turmoil involving riots, demonstrations, general strikes, and assassinations.
A third level involves group relations within states, such as among religious and ethnic groups, nationalities, classes, castes, unions, and families. A state, at the level of its central government, may be peaceful, manifesting a stable social contract, while some of its regions may experience continuing group violence. The final level involves the interpersonal relationships among individuals.

B. Crosscutting Levels. Social levels of peace are crosscutting: each of the conceptual levels may refer to any one of the social ones. Even war is applicable to individual relations, as when conflict goes beyond a violent incident to involve a campaign of violence to defeat or destroy another person.

It should, be clear, then, that there may be peace from war, but not from antagonistic, nonviolent conflict. Moreover, there may be peace from international war, while internal war rends a state. Conversely, a state may be at peace while engaged in international war. Peace among states may be widespread, central state governments may be stable and secure, while some groups in one province, region, or other political subdivision are locked in total war. From the perspective of a particular citizen, his state and social groups all may be at peace, while personal peace eludes him--he simply may not get along with his neighbors or co-workers.

Peace is thus multilayered and complex. This must be kept in mind in defining a just peace.





2.4.3 Conceptual Dimensions
A. The Metalevel. Section 2.3.2 presented major theoretical dimensions of social contracts, and thus of peace. The dimensions considered here and shown in Table 2.5 refer only to peace as a concept and not the concept of peace. This is like the difference between ethical and metaethical concepts, or political and metapolitical ones. In each case, the former refers to the content; the latter to the concept about the contents.45 For example, a peace can be overarching (Table 2.2); a concept of peace can be abstract.
B. Empirical Concept. The first such dimension defines whether the concept is empirical, abstract, or theoretical--a construct.46 An empirical concept47 of peace refers to readily observable phenomena. It is measurable (operational). Peace as absence-of-killing violence is such a concept; as is peace as an absence of legally declared war or a peace treaty (or any written social contract, for that matter).

C. Abstract Concept. While also referring to empirical phenomena, an abstract concept of peace is not directly observable. Rather, it usually denotes a bundle of empirical attributes or qualities, or is reflected in patterns of behavior. Examples are concepts such as status, power, or ideology, which are detached from particular instances or events or specific empirical characteristics. Abstract concepts provide general, theoretical understanding of social reality, while empirical concepts are usually common-sense descriptions of immediate perception.48 For general use peace as a social contract would be an abstract concept, although some social contracts may be quite concrete and hence empirical. The abstraction involved is clearest when we consider implicit, or even subconscious, agreements involving tacit expectations. The abstract, nonformal rules of the road are part of such an abstract social contract. And consider the overarching social contract whose expectations define rules and norms spanning society but which no one signed or directly agreed upon, which few are aware of, but which most obey. Most families are integrated by such expectations that wife and husband, parents and children have of each other but which an observer would have difficulty defining empirically (although certainly indicators could be developed, as for status or power).

Peace as a social contract is an abstraction within the idea of a conflict helix, which is part of social field theory. This theory provides an explanation of conflict, violence, war, and peace. So much, I trust, was made clear in Vol. 2: The Conflict Helix and Vol. 4: War, Power, Peace.

There are other abstract definitions of peace: For example, peace as law or justice; or peace as concord, harmony, or tranquility. Often the theoretical context for an abstract definition of peace is not explicit, but nonetheless is clear from the context within which the concept is developed or used.

D. Construct. Finally, peace as a construct49 means that "peace" serves a stepping-stone role in theory. It is a theoretical concept; analytic, not synthetic. The content given to a construct is not defined independent of a theory but wholly within the operations and deductions of a theory. By contrast, while measurements or indicators of an abstract concept certainly would be directed by a theory, the actual data (or content) are collected (or observed) independently.

This is a difficult but important idea, and I would like to take a moment to make it clear. Consider a simple explanatory theory that y = h + tx, where y is the level of armaments of state i, x is the level of armaments of an opposing state j, and t and h are theoretical coefficients conceptualized as "x's perception of threat from y," and "the hostility that j feels toward i," respectively.50 This simple explanatory theory says that one state's armaments are a function of those of the opposing state's, depending on its perception of the threat from the other and its hostility toward it. Now y and x are abstract concepts, since "armaments" is a concept covering a tremendous empirical diversity of weapons and indicators. Nonetheless, by adding auxiliary statements to the theory one might measure armaments through such indicators as defense expenditures or number of armed military personnel. Data on these indicators could then be collected from sources readily available and independent of the theory.

However, within this theory, threat and hostility are constructs. No measurement of them or indicators need by given; no data collected specifically on them. Rather, the coefficients are totally defined by fitting y = h + tx to the data on x and y. Such a fit could be made by bivariate regression analysis where h is the intercept and t the regression coefficient; y the dependent and x the independent variables. This gives numerical values to h and t without any specific data collected on them. As constructs, they would have been given empirical content totally dependent on the theory y = h + tx and data on x and y.

Keeping this simple arms theory in mind, I must now discriminate between the loose and tight versions of social field theory. In the loose version (specifically, that presented in most of these volumes, especially concerning the conflict helix), the mathematical structure of field theory is usually background;51 content, conceptual understanding, and explanation are usually foreground. A structure of expectations--social contract--is treated as an abstraction. It is given ostensive content, such as in discussing a union-management contract, an implicit agreement ending a family quarrel, an international settlement of a dispute, or the law-norms integrating a group.

In the tight theory,52 mathematical structure, substantive interpretation of primitive terms or constructs,53 operationalization, and empirical tests are of concern. The tight theory is meant to be as explicit, formal, and general as possible. Expectations are constructs weighting behavioral dispositions in a social field and technically function as canonical coefficients in application.54 And to enhance the theory's generality, I have considered a structure of expectations as implicitly an indirect, overarching social contract of a social field (such as a spontaneous or self-organizing55 society). This structure is a cooperative component--another construct56--underlying the variation in manifest interaction. It is reflected in common patterns of social interaction, and thus is empirically measured indirectly only by a mathematically defined axis lying through an empirical pattern of social interaction spanning society.57

For the tight theory, then, applicable to an indirect, overarching social contract for social fields, peace is a construct. Its whole meaning is given by the theory; it serves to aid empirical explanation and theoretical understanding; its empirical content is traced by the cooperative patterns of social interaction.

In this Vol. 5: The Just Peace I will not deal with the tight theory, whose role is precise and testable scientific explanation, not intuitive understanding. The loose theory will provide sufficient framework for our purposes here. And, as in previous volumes, I will treat peace as an abstraction, even when referring to indirect, overarching social contracts.

Incidentally, peace as a construct is not unique to field theory, although as far as I know no other such tight theory so treats it. Peace as divine grace in Christian theology or as shalom in Judaism, of which one meaning is a covenant with Jehovah, are constructs. Their empirical meaning is not given directly or abstractly; rather, they are primitive terms whose content comes from the empirical nature of other, linked theological concepts. Moreover, the concept of "positive peace" developed by Johan Galtung is a construct within a neo-Marxist theory of exploitation; "positive peace" has no direct empirical or indirect abstract empirical content, but is defined as the ability of individuals to realize their potential, which in turn is equated in theory with equality, itself an abstraction measured by various indicators of equality.58

E. Descriptive-Normative. The empirical-abstract-construct dimension of peace concepts is the first conceptual dimension. The second defines whether the concept of peace is descriptive or normative. A descriptive concept is one simply denoting some aspect of reality, such as trade, state, or president.

A normative concept is evaluative, denoting or implying goodness, desirability, what ought to be, or the negation of these denotations. Compassion, equality, and exploitation are such normative concepts. Clearly, the same concept may be used descriptively or normatively depending on context and intent. However, some concepts have a built-in evaluation that even a careful descriptive analysis may not avoid, such as with the concepts murder, torture, exploitation, charity, and love. As with love, peace undefined is an implicit good, a hope, desire, a human ideal. "Give peace in our time, 0 Lord."59 In its common usage, peace is normative.

However, regardless of the affective connotation of peace, the concept can be used descriptively. For example, if peace is conceived as an absence of war or a peace treaty, it is possible to write about the peace in Europe since 1945, the peace of the Versailles Treaty, or the average periods of peace in history, without necessarily connoting that these are good historical periods (although for pacifists, peace as an absence of war is, ipso facto, good in all contexts).

My use of peace as a social contract is meant descriptively. Not all social contracts are good. Some are quite bad,60 as was the horrible peace (as absence of international war) of the Khmer Rouge over Cambodia in 1974-1978 (before the Vietnamese invasion). Since peace is meant here to be (normatively) as neutral a concept as possible, it is sensible to ask when peace is good, or (as a subcategory of the good) when it is just--or when bad or unjust. For the very reason I have treated peace descriptively in previous volumes, even though it is my fundamental normative goal, I now must conclude by pointing out in this Vol. 5: The Just Peace when peace, so described, is just or unjust and, given my analyses and results, what will foster a just peace.





2.5 QUALITIES OF PEACE




2.5.1 An Existent




Table 2.6 presents four qualities of peace entailed by my conceptualization. Clearly, from Section 2.2, peace is a sociopsychological existent. It has dispositional and manifest61 being. In this it is on a par with conflict.62 Conflict is manifested in particular patterns of behavior; so is peace.63 Conflict and peace may be absent, as when two individuals or groups lack contact or awareness of each other. And conflict and peace are coupled existents, closely related within a social process I call the conflict helix.
Other conceptualizations also treat peace as an existing something, such as peace as harmony, integration, or virtue. However, the currently conventional definition of peace as the absence of violence or war treats peace as a void, a nonexistent. This creates several analytical problems, which will be mentioned below.64





2.5.2 Dichotomous
Peace as an existent is dichotomous: it is or it is not. It would be meaningless to talk about more or less of a peace, as it would be meaningless to talk about more or less of a contract, a nation-state, a president, or an elephant.65 Of course, a state may be large or small, rich or poor. Likewise, peace varies along several dimensions; it may take on different forms or social orders.66
It is necessary here, then, to remember the distinction between a peace existing or not and the attributes, form, or order of the peace that exists. Thus, I might say that peace in the world is increasing and mean that more states are subscribing to a particular overarching, international peace. Or by saying that peace is more intense I might imply that a specific peace is involving more and more cooperative interaction.





2.5.3 Internal and External
In my view, peace is internal and external. It is a social contract among people or groups involving these psychological and social realities. The former comprises the parties' expectations and the congruence of these expectations with their mutual interests, capabilities, and wills. These are all psychological variables. The social reality, manifesting the harmonization of certain expectations among the parties, may be evidenced in specific documents (such as a written contract), physical structures (such as certain government buildings), and patterns of cooperative interaction. To say, then, that peace is an existent means that the particular expectations, meanings, and values within the minds of the parties and their social manifestations are all causally-functionally67 integrated into a social contract. Thus, like an iceberg, peace seen on the surface of social relations is only a small part of the overall structure.68




2.5.4 Active
Finally, peace as a social contract is active, not passive. It is created through negotiation, adjustment, resolution, decisions. It comprises predictions (expectations) about the future. It is manifested through cooperative interaction. Its existence depends on congruence with the balance of powers. It is a phase in the dynamics of the conflict helix.
By contrast, peace as the absence of violence or war is passive. True, it may be generated by negotiation and resolution. But the resulting peace is inactive, inert. It is a social void-something to build a wall around to protect and maintain. Any condition or structure or lack thereof constitutes such a peace as long as there is no social violence-even a desert without human life.69





2.6 ADVANTAGES OF
THIS CONCEPTUALIZATION
Peace conceptualized as a social contract has a number of advantages. First, peace is then defined as part of a dynamic social process with a well-defined nature; it is given meaning and substance in definite relationship to conflict and cooperation.
Second, peace stands in clear theoretical and substantive relationship to such important concepts as perception, situation, expectations, interests, capabilities, will, power, status, class, and behavior.70 This gives the nature of peace considerable substantive and theoretical clarity. That is, peace is locked into an overarching social theory.

Third, as a social contract peace is operational, and empirical patterns of peace, so defined, have been well delineated.71

Fourth, because of the theoretical and substantive meaning of peace, peacemaking and peacekeeping policies are given concrete direction and crucial variables are spotlighted. For example, keeping the peace then depends, most generally, on maintaining congruence between the balance of powers and the structure of expectations (social contract). This might be done by altering expectations unilaterally to adjust to changing capabilities, or strengthening will to lessen a developing gap with expectations.72

Fifth, peace as conceptualized embodies a number of psychological principles, such as subjectivity, intentionality, free will, and individualism.73 This, plus the social principles mentioned in the previous Section, enable a clear and straightforward application of the social contract theory of justice. As will be shown in the next part, a just peace is a hypothetical social contract of a particular kind, one to which individuals would fairly and impartially agree.

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This Chapter has described peace as a social contract. And it has made the necessary definitions and distinctions in order to compare this idea of peace to alternative conceptualizations.