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This is the work in progress for my revision of Earth. It involves considerable changes to other articles, and to the Talk:Earth page.

Contents 1 Stuff yet to be rearranged 1.1 Terrain: 1.2 Natural resources 2 Earth's crust 3 Earth's mantle 4 Earth's core 5 Moon 6 List of landlocked nations 7 Earth 7.1 7.2 Composition and geography 7.3 Ecology 7.4 History 7.5 Culture 7.6 Economy 7.7 Politics 8 Talk:Earth 9 Don’t forget

[edit] Stuff yet to be rearranged

• Note: boundary situations with neighboring states prevent many countries from extending their fishing or economic zones to a full 200 nm; 43 nations and other areas that are landlocked include

[edit] Terrain:

Elevation extremes: (measured relative to sea level)

• Lowest point on land: Dead Sea -408 m
• Lowest point overall: Marianas Trench in the Pacific Ocean -10,924 m
• Highest point: Mount Everest 8,850 m (1999 est.)

[edit] Natural resources

• The Earth's crust contains large deposits of fossil fuels: (coal, oil, natural gas, methane clathrate). These deposits are used by humans both for energy production and as feedstock for chemical production.
• Mineral ore bodies have been formed in the Earth's crust by the action of erosion and plate tectonics. These ore bodies form concentrated sources for many metals and other useful elements.
• The Earth's biosphere produces many useful biological products, 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.

[edit] Earth's crust

The crust is the outermost solid layer of Earth, varying from 5 to 35 km in depth. It is composed of silicon-based rocks.

New material constantly finds its way to the surface through volcanoes and cracks in the ocean floors (see seafloor spreading). Much of the Earth's surface is less than 100,000,000 years old.

The crust-mantle boundary occurs as two physically different events. Firstly, there is a discontinuity in the seismic velocity which is known as the Mohorovicic discontinuity or Moho. The cause of the Moho is thought to be a change in rock composition from rocks containing plagioclase feldspar (above) to rocks that contain none (below). The second event is a chemical discontinuity between ultramafic cumulates and tectonized hartzburgites which has been observed from parts of the oceanic crust that have been obducted.

[edit] Earth's mantle

The mantle is the layer of Earth that lies between 30~35 and 2,900 km below the surface. It is composed of substances rich in iron and magnesium: olivines, pyroxenes, and the silicate perovskite (a dense form of enstatite).

The melting points of such iron rich substances are higher than the melting point of pure iron, which comprises almost all Earth’s core. The core is composed almost entirely of pure iron, while iron rich substances are more common outside the core.

The mantle is largely composed of . The lower mantle is thought to be solid while the upper mantle is plastic (semi-molten).

Since the melting point of a substance depends on the pressure it is under, and pressure increases deeper into the mantle, t ****

So, surface iron-substances are solid, upper mantle iron-substances are semi-melted (as it is hot and they are under relatively little pressure), lower mantle iron-substances are solid (as they are under tremendous pressure), outer core pure iron is liquid as it has a very low melting point (despite enormous pressure), and the inner core is solid due to the overwhelming pressure found at the center of the planet.

The upper mantle is known as the asthenosphere.

[edit] Earth's core

The average density of Earth is 5,515 kg/m³. Since the average density of surface material is around 3000 kg/m³, that means there must be denser materials within the core. It is thought that the core is largely composed of nickel and iron, with other dense elements such as lead and uranium either being too rare to be significant or being felsic-seeking in nature (and thus concentrated in the crust rather than the core).

The Earth was entirely molten about 4.6 billion years ago. Gravity would have caused denser substances to sink towards the center in a process called chemical differentiation, while less dense substances would have migrated to the crust.

The inner core is generally believed to be solid, and composed entirely of iron and some nickel. Some believe it may be entirely composed of a single iron crystal. The inner core is surrounded by the outer core, which is believed to be liquid iron mixed with liquid nickel.

Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet, completing one additional rotation every 600 years. It is not known exactly why this occurs, but it is thought to be a result of the circulation of the liquid outer core and interaction with Earth's magnetic field.

[edit] Moon

[incorporate into existing article]

The moon may enable life by moderating the weather. Paleontological evidence shows that Earth's axial tilt is stabilised by tidal interactions with its moon. Without this stabilization, the rotational axis might be chaotically unstable, as it is with a sphere. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result as one pole was continually heated and the other cooled. Planetologists who have studied the effect claim that this might kill all large animal and higher plant life. This remains a controversial subject, however, and further studies of Mars - which shares Earth's rotation period and axial tilt, but not its large moon or liquid core - may provide additional information.

By coincidence, the Moon is just far enough away to have, when seen from the Earth, the same apparent angular size as the Sun. This allows a total eclipse to occur on Earth.

Also, the Moon is tidally locked: its rotation period is the same as the time it takes to revolve around the Earth, meaning it always presents the same face to the planet, seeming to disappear and reappear as the solar terminator line moves around the moon.

The origin of the Moon is presently unknown, but one popular theory has it that it was formed from the collision of a Mars-sized protoplanet into the early Earth. This theory explains (among other things) the Moon's relative lack of iron and volatile elements. See Giant impact theory.

[edit] List of landlocked nations

Afghanistan, Andorra, Armenia, Austria, Azerbaijan, Belarus, Bhutan, Bolivia, Botswana, Burkina Faso, Burundi, Central African Republic, Chad, Czech Republic, Ethiopia, Holy See (Vatican City), Hungary, Kazakhstan, Kyrgyzstan, Laos, Lesotho, Liechtenstein, Luxembourg, Malawi, Mali, Moldova, Mongolia, Nepal, Niger, Paraguay, Rwanda, San Marino, Slovakia, Swaziland, Switzerland, Tajikistan, The Republic of Macedonia, Turkmenistan, Uganda, Uzbekistan, West Bank, Zambia, Zimbabwe

[edit] Earth

Earth is the third planet from the Sun in the Sol system, and the only planet generally accepted by humans to be sustaining life.

[edit]
Orbital characteristics
Mean radius	149,597,870 km
Perihelion	0.983 AU
Aphelion	1.017 AU
Eccentricity	0.0167
Orbital period	365.24220 days
Avg. Orbital Speed	29.79 km/s
Inclination	0°
Satellites	1
Satellite of	Sun
Physical characteristics
Equatorial diameter	12,756.3 km
Surface area	5.10072×108 km2
Mass	5.974×1024 kg
Mean density	5.515 g/cm3
Surface gravity	9.78 m/s2
Escape velocity	11.2 km/s
Rotation period	23.9345 hours
Axial tilt	23.45°
Albedo	37-39%
Surface temperature	min mean max 182 K 282 K 333 K
Atmospheric characteristics
Pressure	101.325 kPa
nitrogen	78%
oxygen	21%
argon	1%
carbon dioxide water vapor	trace

[edit] Composition and geography

Like other terrestrial planets, Earth has a silicaceous solid crust (see Earth's crust) with a viscous mantle (see Earth's mantle), and an inner core. Earth's core has a solid inner section and a liquid outer section; convection of this conductive liquid causes a magnetic field.

Earth is the only known planet to hold substantial liquid water. Water covers 70.8 percent of the surface (see ocean, fresh water), leaving exposed several continents (see Africa, America, Antarctica, Australasia, and Eurasia) and many smaller islands. Earth’s nitrogen-based atmosphere helps retain the water (in conjunction with the greenhouse effect, ozone layer, and magnetosphere), as well as filtering and retaining energy from the Sun.

Earth’s natural satellites include the Moon and at least one co-orbital asteroid.

[edit] Ecology

Life on Earth is carbon-based, universally derived from DNA, and ubiquitous but progressively more complex towards the Equator. Some 1.4 million species are known, but biologists estimate many times that number remain unclassified.

Of the known species, over half are insects, on which other animals and most flowering plants depend for their survival. Plants and algae are symbiotic with animals generally through the oxygen cycle. The most abundant species is the Antarctic krill (Euphausia superba), with an estimated biomass of at least 500 million tonnes. The most influential self-aware species is the human (Homo sapiens sapiens), with a population of 6 billion; human activities have affected the ecosystem noticeably in the past few centuries (see for example land use, pollution, global warming).

See also carbon cycle, tree of life.

[edit] History

Radiometric dating suggests Earth formed about 4.55 billion years ago, in molten form — the oldest known rocks are only 3.9 billion years old. Chemical differentiation caused denser elements to sink, with lighter substances solidifying into the crust; oceans formed from the condensation of volcanic outgassing.

According to mainstream biology, the first known organisms complex enough to be called “life” date from 3.8 billion years ago (see origin of life), and consisted of single cells; multicellular organisms took another 2.9 billion years to develop. The “Cambrian Explosion”, 545 million years ago, saw the development of a wide variety of animals, with plants following some 140 million years later. The evolution of more complex and diverse lifeforms, already complicated by ice ages and by continental drift dividing land masses, has also been disturbed by repeated extinction event.

The earliest humans (Homo habilis) are believed to have developed in Africa about 2.5 million years ago, with today’s Homo sapiens appearing about 300,000 years ago. For most of their existence, humans practised a variety of agricultural and hunter-gatherer lifestyles in tribal groups. Then totalitarian agriculture — the practice of devoting land to growing surplus food — developed, amongst other places, in the Fertile Crescent about 9000 BCE. This lifestyle spread rapidly with the expanding population, dominating Eurasia within only 7000 years; with reliable intercontinental transport, it reached North America in the 16th and 17th centuries CE, Australasia in the 18th and 19th centuries, and Africa in the early 20th century.

Meanwhile, the treatment of food as property — along with the animals and land used to produce it — had encouraged the establishment of governments. Dozens of government-based civilizations rose and fell over the next few thousand years, from the Sumerians, Greeks, Romans, and the Chinese dynasties, to today’s Western civilization. Among other developments, this period saw the introduction of cities, slavery, writing, mass warfare, and salvationist religions. Following the Dark Ages and Black Death in Europe, the Renaissance in the mid-1000s CE began an age of exploration and accelerating scientific and technological development. This had considerable positive effects on human welfare, particularly in medicine, nutrition, and communications. It also had negative effects: most obviously, increasingly powerful weaponry allowed unprecedented death and destruction from wars in the 20th century and terrorism into the 21st.

For more, see geologic timescale, history.

[edit] Culture

Earth’s culture has been heavily influenced by the themes of spirituality (see for example religion, temple, Christmas), narrative (see for example ballad, soap opera), and human sexuality (see for example Venus of Willendorf, burlesque, pop music, pornography). The past few centuries have, perhaps, seen more abstraction and mathematical elegance (see for example Modernism, classical music, abstract art), and an increase in commercialization (see for example patronage, mass production, advertising).

The massive increase in speed and volume of transport and communications over the last one thousand years (see for example human migration, mass media) has led to considerable fusion and assimilation of cultures, and a substantial reduction in the number of human languages in active use. Both these trends are strongly resisted, however, by groups seeking to maintain their cultural identity (see cultural imperialism).

[edit] Economy

Almost all trading of goods and services is mediated with money, measured in many currencies such as the US dollar. Money is itself also traded on international finance markets; these foreign exchange transactions worldwide total more than 1 trillion US dollars per day. However, the productivity of a nation is more usefully measured by Gross Domestic Product, consisting of _________________. As a sum of national GDPs, Gross World Product for 1999 was estimated at 40.9 trillion US dollars. Major industries include _____________.

For more, see Economy of Earth.

[edit] Politics

The breakup of the Ottoman Empire in 1922, and colonial empires later in the 20th century, left Earth’s land mass almost universally partitioned politically into nation states. (International treaties largely maintain the neutrality of Antarctica, of Earth’s oceans, and of outer space.) 191 nation states are currently recognized by the United Nations; 75 percent of these nations have a human population of between ___ and ___. Sufficiently large nations are typically subdivided into states, provinces, and/or city areas with some control over their own infrastructure (see local government).

Currently, most nation states have a generally democratic political system, with one being governed by an absolute monarch (see also constitutional monarchy), and four as communist states. Since the collapse of the communist Soviet Union in 1991, the dominant nation state has been the United States of America. Other significant powers include China and Russia, and the European Union has been increasing in influence over the past few decades.

[edit] Talk:Earth

“Mostly harmless” considered harmful? There has been a long-running tussle about whether to include the line “Mostly harmless” (from The Hitchhiker's Guide to the Galaxy) in this Wikipedia article. I’m summarizing the argument here, as someone who doesn’t care one way or the other. Anonymous: “I really feel it is remiss not to include the Mostly Harmless thing somewhere in the page.” Bryan Derksen: “… Look at the big picture; it was just a funny science fiction novel that happened to get a cult following in some parts of the world among certain groups … Bear in mind that we're trying to create an actual encyclopedia here, something that students might use as a resource for serious assignments and such.” Anonymous: “This is already seen in everything2.com, hhg.com and a few other distributed encyclopedias like this one. What's the big deal? People expect it!” maveric149: “Because it is irrelevant to an article about the Earth and wikipedia is not everything2 or hhg.” Eloquence: “The idea that somehow Douglas Adams' (certainly entertaining) fiction should receive preferential treatment in an article about our home planet seems quite bizarre to me. You know how many jokes, stories and tales about Earth there are? … We do not accommodate undesirable behavior to get rid of it.” Oliver P.: “It's the only well-known joke, by any author, on the subject of the encyclopaedic treatment of the Earth … However, I withdraw my suggestion, as the paragraph did look out of place, and nobody seems to have understood its intent anyway.”

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If an entity from another system within the known universe (or any other universe for that matter) were to read (assuming that was possible) the Earth page, ya gotta wonder what said entity might think! --Grant

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Revision: With Grant’s comment in mind, I have boldly revised Earth, with a new structure. I have tried to limit the article to 1000 words, delegating more obscure information to specialized articles (that is, after all, a big advantage of hypertext). I hope, personally, that those revising it in future stick roughly within that word limit — though it is purely an invented limit, without such a limit, this article would surely grow without bound. I suggest that for everything you add, you remove just as many words, preferably from the same subsection. For every example you add, remove a less useful example. And resist the common temptation to insert relatively unimportant details just because you happen to know them.

As RK wrote in an earlier version of this Talk page, “This article is not about all facts and information about the human race! This article also is not the Main Page of an encyclopedia.” For that reason, this article does not mention mathematics, physics, philosophy, the formation of the galaxy, or anything else which isn’t about Earth in particular. What it does do:

• It tries to describe this planet in the same way Wikipedia would describe any other well-studied inhabited planet. (Any planet’s most influential self-aware species would feature heavily in such an article, just as humans feature heavily in Earth.)
• In the current absence of a large number of well-studied planets, it avoids subjective judgements (see NPOV) about how special Earth is. (E.g. don’t say “Precipitation patterns vary widely”, until you know that they vary widely on Earth compared to other planets which have precipitation.)

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Here are some notes and clarifications.

1. The removal of the header from the table of facts, and the movement of the table after the first paragraph, are both deliberate and done for accessibility reasons. I think it more important that the page be pleasant to listen to, than that the table appears in exactly the same place on each planet page.
2. The History section will likely seem outrageous to anyone who has studied some small aspects of history in great detail, and isn’t used to seeing a planet-wide summary — averaging one billion years per paragraph — where their specialty isn’t even mentioned. I encourage someone to do a fuller (~2000-word) summary of Earth's history, with many more links for periods, regions, and subjects, which can be linked from the “For more, see …” line (leaving History for metahistorical issues).
3. Something I wanted to do, but haven’t had time yet, is a basic statistical analysis of population for nation states, to come up with a meaningful summary such as “75 percent of nation states have a population between 5 and 58 million”. That would give a good impression of how big most nation states are, ignoring extremes such as the Holy See and China.

Facts from the previous version, removed from this version because they weren’t important enough for an article about Earth in general, have mostly been moved to other articles — some existing (Moon) and some new (Earth's crust, Earth's mantle, Earth's core). The following, however, have not yet been moved to any articles:

• 0-60 km -- Lithosphere
  • 0-30/35 km -- Crust
• 30/35-2900 km -- Mantle
  • 100-700 km -- Asthenosphere
• 2900-5100 km -- Outer Core
• 5100-~6375 km -- Inner Core

Area:

• total: 510.072 million km²
• land: 148.94 million km²
• water: 361.132 million km²
• note: 70.8% of the world's surface is covered by water, 29.2% is exposed land

Land boundaries: the land boundaries in the world total 251,480.24 km (not counting shared boundaries twice)

Coastline: 356,000 km

Maritime claims: see United Nations Convention on the Law of the Sea

• contiguous zone: 24 nm claimed by most, but can vary
• continental shelf: 200 m depth claimed by most or to depth of exploitation; others claim 200 nm or to the edge of the continental margin
• exclusive fishing zone: 200 nm claimed by most, but can vary
• exclusive economic zone: 200 nm claimed by most, but can vary
• territorial sea: 12 nm claimed by most, but can vary

• The interior of the Earth reaches temperatures of 5270 K. The planet's internal heat was originally released during its accretion (see gravitational binding energy), and since then additional heat has continued to be generated by the decay of radioactive elements such as uranium, thorium, and potassium. The heat flow from the interior to the surface is only 1/20,000 as great as the energy received from the Sun.

• The Earth also suffers from the Chandler wobble.

• Climate: Two large areas of polar climates separated by two rather narrow temperate zones from a wide equatorial band of tropical to subtropical climates. Precipitation patterns vary widely, ranging from several meters of water per year to less than a millimeter. [Aside from the precipitation NPOV problem described earlier, are the polar/temperate/equatorial zones really statistically distinct, rather than merely useful ecological concepts?

If you find an article for any of these to go in, please delete it from the list above.

-- Ford Prefect, 2003-06-xx

[edit] Don’t forget

• Remove Earth from Brilliant prose page after uploading new version, for fairness
• Update user page