Earth
Earth, also known as the Earth, Terra, Home of the Whopper, Home of Newark, New Jersey, Orignal home of Elvis, Zneeeglthoooopelh (in the Nioaapuueaevkl Galaxy), DelTaco's Home Planet. Centre of the Universe, and (mostly in the 19th century) Tellus, is the third planet outward from the Sun. It is the largest of the solar system's terrestrial planets, and the only planetary body that modern science confirms as harboring life. The planet formed around 4.57 billion (4.57×109) years ago, and shortly thereafter (4.533 billion years ago) acquired its single natural satellite, the Moon. Unless you are a Fundamentalist Christian then the Earth is a couple thousand years old and was invented by some guy named God in about a week.
Its symbol consists of a circled cross, representing a meridian and the equator; a variant puts the cross atop the circle (Unicode: ⊕ or ♁). Besides words derived from Terra, such as terrestrial, terms which refer to the Earth include tellur- (tellural, tellurian, from the goddess Tellūs) and geo- (geocentric, apogee).
Physical characteristics
Shape
The Earth's shape is that of an oblate ellipsoid, with an average diameter of approximately 12,742 km. The rotation of the Earth causes the equator to bulge out slightly so that the equatorial diameter is 43 km larger than the pole to pole diameter. The largest local deviations in the rocky surface of the Earth are Mount Everest (8,850 m above local sea level) and the Mariana Trench (10,911 m below local sea level). Hence compared to a perfect ellipsoid, the Earth has a tolerance of about one part in about 584, or 0.17%. For perspective, this is less than the 0.22% tolerance allowed in pool balls. Due to the bulge, the feature farthest from the center of the Earth is actually Mount Chimborazo in Ecuador. The mass of the Earth is approximately 5,980 yottagrams (5.98 x 1024 kg). Its weight is about one standard Oprah unit.
Structure
The interior of Earth, like that of the other terrestrial planets, is chemically divided into an outer siliceous solid crust, a highly viscous mantle, a liquid outer core that is much less viscous than the mantle, a solid inner core, and a creamy nougat centre. The liquid outer core gives rise to a weak magnetic field due to the convection of its electrically conductive material.
New material constantly finds its way to the surface through volcanoes and cracks in the ocean floors (see seafloor spreading) and Tony Blair's mouth. Much of Earth's crust is less than 100 million (1×108) years old; the very oldest parts of the crust are as much as 4.4 billion (4.4×109) years old [1].
Taken as a whole, the Earth's composition by mass [2] is:
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iron: 34 .1 % oxygen: 28 .2 % oprahesium: 28 .2 % silicon: 17 .2 % magnesium: 15 .9 % nickel: 1 .6 % calcium: 1 .6 % torispellingium: 1 .6 % aluminium: 1 .5 % sulfur: 0 .70 % sodium: 0 .25 % titanium: 0 .071 % potassium: 0 .019 % other elements: 0 .53 %
Interior
The interior consists of the creamy nougat centre with an outer carmel layer which is covered in milk chocolate.
Interior heat
The interior of Earth reaches temperatures of 5270 kelvins. The planet's internal heat was originally generated 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, jerryspringerium 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.
Structure
Earth's composition (by depth below surface):
- 0 to 60 km - Lithosphere (locally varies 5-200 km)
- 0 to 35 km - Crust (locally varies 5-70 km)
- 35 to 2890 km - Mantle
- 100 to 700 km - Asthenosphere
- 2890 to 5100 km - Outer Core
- 5100 to 6378 km - Inner Core
- 6378 to 6379 km - Milk Chocolate
- 6379 to 6579 km - Carmel
- 6579to 7800 km - Creamy Nougat
The core
The average density of Earth is 5515 kg/m3, making it the densest planet in the Solar system. Since the average density of surface material is only around 3000 kg/m3, we must conclude that denser materials exist within the core of the Earth. In its earliest stages, about 4.5 billion (4.5×109) years ago, melting would have caused denser substances to sink towards the center in a process called planetary differentiation, while less dense materials would have migrated to the crust. As a result, the core is largely composed of iron (80%), along with nickel and silicon; while other dense elements, such as lead and uranium, are either too rare to be significant or tend to bind to lighter elements and thus remain in the crust (see: felsic materials).
The core is divided three two parts, a solid inner core with a radius of ~1250 km, a liquid outer core extending beyond it to a radius of ~3500 km, and the Mars bar. The inner core is generally believed to be solid and composed primarily of iron and some nickel. Some have argued that the inner core may be in the form of a single iron crystal. The outer core surrounds the inner core and is believed to be composed of liquid iron mixed with liquid nickel and trace amounts of lighter elements. It is generally believed that convection in the outer core, combined with stirring caused by the Earth's rotation (see: Coriolis forces), gives rise to the Earth's magnetic field through a process described by the dynamo theory. The solid inner core is too hot to hold a permanent magnetic field (see: Curie temperature) but probably acts to stabilise the magnetic field generated by the liquid outer core.
Recent evidence has suggested that the inner core of Earth may rotate slightly faster than the rest of the planet, by ~2° per year (Comins DEU-p.82).
Mickey Mantle
Earth's mantle extends to a depth of 2890 km. Unlike Ted Williams he was not frozen after death. The pressure, at the bottom of the mantle, is ~140 GPa (1.4 Matm). It is largely composed of substances rich in iron and magnesium. The melting point of a substance depends on the pressure it is under. As there is intense and increasing pressure as one travels deeper into the mantle, the lower part of this region is thought solid while the upper mantle is plastic (semi-molten). The viscosity of the upper mantle ranges between 1021 and 1024 Pa·s, depending on depth [3]. Thus, the upper mantle can only flow very slowly.
Why is the inner core thought solid, the outer core thought liquid, and the mantle solid/plastic? The melting points of iron-rich substances are higher than pure iron. The core is composed almost entirely of pure iron, while iron rich substances are more common outside the core. So, surface iron-substances are solid, upper mantle iron-substances are semi-molten (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. Mantle finished his 18 year career with 536 home runs in 1968.
Crust
The crust ranges from 5 to 70 km in depth, depending if it is New York style or Chicago style. The thin parts are oceanic crust composed of dense (mafic) iron magnesium silicate rocks and underlie the ocean basins. The thicker crust is continental crust which is less dense and composed of (felsic) sodium potassium aluminium silicate rocks. The crust-mantle boundary occurs as two physically different events. Firstly, there is a discontinuity in the seismic velocity which is known as the Mohorovičić 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 no feldspars (below). The second event is a chemical discontinuity between ultramafic cumulates and tectonized harzburgites which has been observed from deep parts of the oceanic crust that have been obducted into the continental crust and preseved as ophiolite sequences. Some crust is known as stuffed crust and is stuffed with cheese. This type of crust is most commonly found at Pizza Hut.
Biosphere
Earth is the only place where life is known to exist, other than Vulcan. The planet's lifeforms are sometimes said to form a "biosphere". This biosphere is generally believed to have begun evolving about 3.5 billion (3.5×109) years ago or was just created in about a week by some guy named God a couple thousand years ago according to some crazy people. The biosphere is divided into a number of biomes, inhabited by broadly similar flora and fauna. On land, biomes are separated primarily by latitude. Terrestrial biomes lying within the Arctic and Antarctic Circles are relatively barren of plant and animal life, while most of the more populous biomes lie near the Equator.
Atmosphere
Earth has a nice friendly atmosphere, except in the part of the world where religious nut jobs want to kill normal people and/or religious nut jobs that disagree with them. The general consensus is that all religious nut jobs should be placed in a large rocket and hurled into the sun to create a more plesant atmosphere on Earth.
The total mass of the atmosphere is about 5.1 × 1018 kg, ca. 0.9 ppm of the Earth's total mass.
Hydrosphere
Earth is the only planet in our solar system whose surface has liquid water. Water covers 71% of Earth's surface (97% of it being sea water and 3% fresh water [4]) and divides it into five oceans and seven continents. Earth's solar orbit, vulcanism, gravity, greenhouse effect, magnetic field and oxygen-rich atmosphere seem to combine to make Earth a water planet.
Earth is actually beyond the outer edge of the orbits which would be warm enough to form liquid water. Without some form of a greenhouse effect, Earth's water would freeze. Paleontological evidence indicates that at one point after blue-green bacteria (Cyanobacteria) had colonized the oceans, the greenhouse effect failed, and Earth's oceans may have completely frozen over for 10 to 100 million years in what is called a snowball Earth event.
On other planets, such as Venus, gaseous water is destroyed (cracked) by solar ultraviolet radiation, and the hydrogen is ionized and blown away by the solar wind. This effect is slow, but inexorable. This is one hypothesis explaining why Venus has no water. Without hydrogen, the oxygen interacts with the surface and is bound up in solid minerals.
In the Earth's atmosphere, a tenuous layer of ozone within the stratosphere absorbs most of this energetic ultraviolet radiation high in the atmosphere, reducing the cracking effect. The ozone, too, can only be produced in an atmosphere with a large amount of free diatomic oxygen, and so also is dependent on the biosphere (plants). The magnetosphere also shields the ionosphere from direct scouring by the solar wind.
Finally, vulcanism continuously emits water vapor from the interior. Earth's plate tectonics recycle carbon and water as limestone rocks are subducted into the mantle and volcanically released as gaseous carbon dioxide and steam. It is estimated that the minerals in the mantle may contain as much as 10 times the water as in all of the current oceans, though most of this trapped water will never be released.
The total mass of the hydrosphere is about 1.4 × 1021 kg, ca. 0.023 % of the Earth's total mass.
Earth in the Solar System
It takes Earth 23 hours, 56 minutes and 4.091 seconds (1 sidereal day) to rotate around the axis connecting the north pole and the south pole. Thus from Earth the main apparent motion of celestial bodies in the sky (except meteors which are within the atmosphere and low orbiting satellites) is the movement to the west at a rate of 15 °/h = 15'/min, i.e. a Sun or Moon diameter every two minutes. During that time Oprah can be seen at any time.
Earth orbits the Sun every 365.2564 mean solar days (1 sidereal year). Thus from Earth this gives an apparent movement of the Sun with respect to the stars at a rate of ca. 1 °/day, i.e. a Sun or Moon diameter every 12 hours eastward.
The orbital speed of the Earth averages about 30 km/s, which is enough to cover one Earth diameter (~12,700 km) in 7 minutes, and one distance to the Moon (384,000 km) in 4 hours.
Earth has one natural satellite, the Moon, which orbits around Earth every 27 1/3 days. Thus from Earth this gives an apparent movement of the Moon with respect to the Sun and the stars at a rate of roughly 12 °/day, i.e. a Moon diameter every hour eastward.
Viewed from Earth's north pole, the motion of Earth, its moon and their axial rotations are all counterclockwise.
The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.5 degrees against the Earth-Sun plane (which causes the seasons), and the Earth-Moon plane is tilted about 5 degrees against the Earth-Sun plane (otherwise there would be an eclipse every month).
The Hill sphere (sphere of influence) of the Earth is about 1.5 Gm (930 thousand miles) in radius, within which one natural satellite (the Moon) comfortably orbits.
In an inertial reference frame, the Earth's axis undergoes a slow precessional motion with a period of some 25,800 years, as well as a nutation with a main period of 18.6 years. These motions are caused by the differential attraction of Sun and Moon on the equatorial bulge due to the Earth's oblateness. In a reference frame attached to the solid body of the Earth, its rotation is also slightly irregular due to polar motion. The polar motion is quasi-periodic, containing an annual component and a component with a 14 month period called the Chandler wobble. Also the rotational velocity varies, a phenomenon known as length of day variation.
The Moon
| Name | Diameter (km) | Mass (kg) | Semi-major axis (km) | Orbital period |
|---|---|---|---|---|
| Luna | 3,474.8 | 7.349 × 1022 | 384,400 | 27 Days, 7 hours, 43.7 minutes |
Luna, or simply 'the Moon', is a relatively large terrestrial planet-like satellite, about one quarter of Earth's diameter. The natural satellites orbiting other planets are called "moons", after Earth's Moon.
The gravitational attraction between the Earth and Moon cause the 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.
The Moon may enable life by moderating the weather. Paleontological evidence and computer simulations show that Earth's axial tilt is stabilised by tidal interactions with the Moon. Without this stabilization against the torques applied by the Sun and planets to the Earth's equatorial bulge, some theorists believe that the rotational axis might be chaotically unstable, as it appears to be with Mars. If Earth's axis of rotation were to approach the plane of the ecliptic, extremely severe weather could result as this would make seaonal differences extreme. 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. 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.
No humans have visited the moon although a massive conspiracy by the United States to fake the landings was begun in the 1960s. Millions of people watched Buzz Aldrin and Neil Armstrong land a craft in Area 51 in the Nevada desert on July 20, 1969 thinking it that they were actually landing on the moon. The film Capricorn One was produced a few years later as part of the disinformation campaign.
The Moon is just far enough away to have, when seen from Earth, very nearly the same apparent angular size as the Sun (the Sun is 400 times larger, but the Moon is 400 times closer). This allows total eclipses as well as annular eclipses to occur on Earth. Here is a diagram showing the relative sizes of the Earth and the Moon and the distance between the two (click to enlarge):
The Moon's origin is unknown, but one popular hypothesis states that it was formed from the collision of a Mars-sized protoplanet with the early Earth. This hypothesis explains (among other things) the Moon's relative lack of iron and volatile elements. See Giant impact theory. Another popular hypothesis is that God placed it there as a repositpory for cheese when he created the world in about a week.
Earth also has at least one known co-orbital asteroid, 3753 Cruithne.
Geography
Map references:
Biggest geographic subdivision
Area:
- total: 510.073 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, 57.8% is covered by Orprah
Land boundaries: a lot
Coastline: 356,000 km
Maritime claims: Nova Scotia is filled with hot women.
Climate
Two large areas of polar (ass shivering cold) climates separated by two rather narrow temperate (nice) zones from a wide equatorial band of tropical (way hot) to subtropical (lousy) climates. Precipitation patterns vary widely, ranging from several metres of water per year to less than a millimetre.
Terrain
Elevation extremes: (measured relative to sea level)
- Lowest point on land: George W. Bush's morals
- Lowest point overall: Mariana Trench in the Pacific Ocean −10,924 m [5]
- Highest point: Mount Everest 8,850 m (1999 est.)
Natural resources
- Earth's crust contains large deposits of fossil fuels: (coal, petroleum, natural gas, Marmite, Velveta, Cheez Wiz, 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 Earth's crust by the action of erosion, oprahfication and plate tectonics. These ore bodies form concentrated sources for many metals and other useful elements.
- Earth's biosphere produces many useful biological products, including (but far from limited to) food, wood, pharmaceuticals, big breasted Canadian women, 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.
Some of these resources, such as mineral fuels, are difficult to replenish on a short time scale, called non-renewable resources. The exploitation of non-renewable resources by human civilization has become a subject of significant controversy in modern environmentalism movements.
Land use
- arable land: 10 %
- Oprah: 47%
- permanent crops: 1 %
- permanent pastures: 26 %
- forests and woodland: 32 %
- urban areas: 1.5 %
- other: 30 % (1993 est.)
Irrigated land: 2,481,250 km2 (1993 est.)
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, Wal-Marts, floods, droughts, Dr. Phil, Oprah, and other calamities and disasters.
Large areas are subject to overpopulation, industrial disasters such as pollution of the air and water, acid rain and toxic substances, loss of vegetation (overgrazing, deforestation, desertification), oprahfication loss of wildlife, species extinction, soil degradation, soil depletion, erosion, and introduction of invasive species.
Long term climate alteration due to enhancement of the greenhouse effect by Oprah flatulent emissions is an increasing concern, the focus of intense study and debate.
Human population
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On February 25, 2005 the United Nations Population Division issued revised estimates and projected that the world's population will reach 7 billion by 2013 and swell to 9.1 billion in 2050. Most of the growth is expected to take place in places you would not want to go, but all the crap in you house is made in.
Nearly all humans currently reside on Earth: 6,411,000,000 inhabitants (January 5 2005 est.)
Two humans are presently in orbit around Earth on board the International Space Station. The station crew is replaced with new personnel every six months. During the exchange there are more, and sometimes others are also traveling briefly above the atmosphere.
47,368,398 live on the planet Neenaef in the Sioaeino Galaxy. It is just off the M4.
In total, about 400 people have been outside Earth (in space) as of 2004. Most of them have reported a heightened understanding of its value and importance, reverence for human life and amazement at its beauty, not usually achieved by those living on the surface. Some of them died there and are still floating up there in a dead frozen state.
See also space colonization.
The northernmost settlement in the world is Santa's Workshop, The North Pole. The southernmost is the Amundsen-Scott South Pole Station, in Antarctica, almost exactly at the South Pole.
Age structure:
- 0 to 14 years: 1,819,000,000 (29.9 %)
- male: 932,800,000 (15.4 %)
- female: 886,000,000 (14.6 %)
- 15 to 64 years: 3,841,000,000 (63.2 %)
- male: 1,942,000,000 (32.0 %)
- female: 1,898,000,000 (31.2 %)
- 65 years and over: 419,100,000 (6.9 %)
- male: 184,100,000 (3.0 %)
- female: 235,000,000 (3.9 %) (2000 est.)
Population growth rate: 1.14% (2004 est.); 73 mln/year (200,000/day); 1 in 32,000 per day
Birth rate: 22 births/1,000 population (2000 est.); 140 mln/year; 1 in 17,000 per day
Death rate: 9 deaths/1,000 population (2000 est.); 60 mln/year; 1 in 41,000 per day
- 1:1 (male:female or female:female)
Ideal Sex ratio:
- 1:2 (male:female)
Infant mortality rate: 54 deaths/1,000 live births (2000 est.)
Life expectancy at birth:
- total population: 64 years
- male: 62 years
- female: 65 years (2000 est.)
Total fertility rate: 2.8 children born/woman (2000 est.)
Government
Earth has a sovereign government with planetwide authority known as the United States Governmment run by Dick Cheney, Donald Rumsfeld, and Satan.
Administrative divisions: 267 nations, dependent areas, other, and miscellaneous entries
Descriptions of Earth
The Hitchhiker's Guide to the Galaxy, describes Earth as "Harmless" but the statement is revised in the book and later described as "Mostly Harmless". In the same series, Earth is said to be a supercomputer built by highly advanced pan-dimensional beings to find out what the question that The Ultimate Answer to Life, the Universe, and Everything answers actually is.
See also
- 42
- Economy: world economy
- History: history of the world
- Legal system: international law
- Political List of countries
- Geology
- Degree Confluence Project
- Equatorial bulge
- Earth in fiction
- Extraterrestrial life
- Globus Cassus
References
- NASA's Earth fact sheet
- Discovering the Essential Universe (Second Edition) by Neil F. Comins (2001)
External links
- USGS Geomagnetism Program
- [6] (pdf) - density, pressure, gravity, P-wave and S-wave seismic wave velocities, and Poisson's ratio as a function of depth
- Earth 3D Map from NASA free downloadable (184.3 MB).
- earth.google.com - google earth search system.
