- Anti Joke

Earth From Wikipedia, the free encyclopedia This article is about the planet. For other uses, see Earth (disambiguation). Page semi-protected Earth Astronomical symbol of Earth "The Blue Marble" photograph of Earth, taken by the Apollo 17 lunar mission. The Arabian peninsula, Africa and Madagascar lie in the upper half of the disc, while Antarctica is at the bottom. "The Blue Marble" photograph of Earth, taken during the Apollo 17 lunar mission. Orbital characteristics Epoch J2000[n 1] Aphelion 151930000 km (1.01559 AU)?[n 2] Perihelion 147095000 km (0.9832687 AU)?[n 2] Semi-major axis 149598261 km (1.00000261 AU)?[1] Eccentricity 0.01671123[1] Orbital period 365.256363004 d?[2] (1.00001742096 yr) Average orbital speed 29.78 km/s[3] (107200 km/h) Mean anomaly 355.53 deg[4] Inclination 7.155 deg to Sun's equator; 1.57869 deg[5] to invariable plane; 0.00005 deg to J2000 ecliptic Longitude of ascending node ?11.26064 deg[3] to J2000 ecliptic Argument of perihelion 102.94719 deg[3] Satellites One natural satellite; 1070 operational artificial satellites; 21000 pieces of debris over 10 cm in size (as of 24 October 2013).[6] Physical characteristics Mean radius 6371.0 km[7] Equatorial radius 6378.1 km[8][9] Polar radius 6356.8 km[10] Flattening 0.0033528[11] 1/298.257222101 (ETRS89) Circumference 40075.017 km (equatorial)?[9] 40007.86 km (meridional)?[12][13] Surface area 510072000 km2[14][15][n 3] (148940000 km2 (29.2%) land 361132000 km2 (70.8%) water) Volume 1.08321×1012 km3[3] Mass 5.97219×1024 kg[16] (3.0×10-6 solar mass) Mean density 5.514 g/cm3[3] Surface gravity 9.807 m/s2[17] (1 g) Moment of inertia factor 0.3307[18] Escape velocity 11.186 km/s[3] Sidereal rotation period 0.99726968 d[19] (23h 56m 4.100s) Equatorial rotation velocity 1,674.4 km/h (465.1 m/s)[20] Axial tilt 23 deg 26 min 21.4119 s?[2] Albedo 0.367 geometric[3] 0.306 Bond[3] Surface temp. min mean max Kelvin 184 K[21] 288 K[22] 330 K[23] Celsius ?89.2 °C 15 °C 56.7 °C Atmosphere Surface pressure 101.325 kPa (at MSL) Composition by volume 78.08% nitrogen (N2)[3] (dry air) 20.95% oxygen (O2) 0.930% argon 0.039% carbon dioxide[24] ~ 1% water vapor (climate-variable) Earth, also called the world[n 4] and, less frequently, Gaia[n 5] (and Terra in some works of science fiction[27]) is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to accommodate life. The earliest life on Earth arose at least 3.5 billion years ago.[28][29][30] Earth's biodiversity has expanded continually except when interrupted by mass extinctions.[31] Although scholars estimate that over 99 percent of all species that ever lived on the planet are extinct,[32][33] Earth is currently home to 10–14 million species of life,[34][35] including over 7.2 billion humans[36] who depend upon its biosphere and minerals. Earth's human population is divided among about two hundred sovereign states which interact through diplomacy, conflict, travel, trade and communication media. According to evidence from radiometric dating and other sources, Earth was formed around four and a half billion years ago. Within its first billion years,[37] life appeared in its oceans and began to affect its atmosphere and surface, promoting the proliferation of aerobic as well as anaerobic organisms and causing the formation of the atmosphere's ozone layer. This layer and the geomagnetic field blocked the most life-threatening parts of the Sun's radiation, so life was able to flourish on land as well as in water.[38] Since then, the combination of Earth's distance from the Sun, its physical properties and its geological history have allowed life to thrive and evolve. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. Seventy-one percent of Earth's surface is covered with water,[39] with the remainder consisting of continents and islands that together have many lakes and other sources of water that contribute to the hydrosphere. Earth's poles are mostly covered with ice that includes the solid ice of the Antarctic ice sheet and the sea ice of the polar ice packs. Earth's interior remains active with a solid iron inner core, a liquid outer core that generates the magnetic field, and a thick layer of relatively solid mantle. Earth gravitationally interacts with other objects in space, especially the Sun and the Moon. During one orbit around the Sun, Earth rotates about its own axis 366.26 times, creating 365.26 solar days or one sidereal year.[n 6] Earth's axis of rotation is tilted 23.4° away from the perpendicular of its orbital plane, producing seasonal variations on the planet's surface with a period of one tropical year (365.24 solar days).[40] The Moon is Earth's only natural satellite. It began orbiting Earth about 4.53 billion years ago. The Moon's gravitational interaction with Earth stimulates ocean tides, stabilizes the axial tilt and gradually slows the planet's rotation. Contents [hide] 1 Name and etymology 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 2.10 Magnetosphere 3 Orbit and rotation 3.1 Rotation 3.2 Orbit 3.3 Axial tilt and seasons 4 Habitability 4.1 Biosphere 4.2 Evolution of life 4.3 Natural resources and land use 4.4 Natural and environmental hazards 4.5 Human geography 5 Cultural and historical viewpoint 6 Chronology 6.1 Formation 6.2 Geological history 6.3 Predicted future 7 Moon 8 Asteroids and artificial satellites 9 See also 10 Notes 11 References 12 Further reading 13 External links Name and etymology The modern English word Earth developed from a wide variety of Middle English forms,[42] which derived from an Old English noun most often spelled eorðe.[41] It has cognates in every Germanic language, and their proto-Germanic root has been reconstructed as *erþ?. In its earliest appearances, eorðe was already being used to translate the many senses of Latin terra and Greek ?? (g?): the ground,[44] its soil,[46] dry land,[49] the human world,[51] the surface of the world (including the sea),[54] and the globe itself.[56] As with Terra and Gaia, Earth was a personified goddess in Germanic paganism: the Angles were listed by Tacitus as among the devotees of Nerthus,[57] and later Norse mythology included Jörð, a giantess often given as the mother of Thor.[58] Originally, earth was written in lowercase and, from early Middle English, its definite sense as "the globe" was expressed as the earth. By early Modern English, many nouns were capitalized and the earth became (and often remained) the Earth, particularly when referenced along with other heavenly bodies. More recently, the name is sometimes simply given as Earth, by analogy with the names of the other planets.[41] House styles now vary: Oxford spelling recognizes the lowercase form as the most common, with the capitalized form an acceptable variant. Another convention capitalizes Earth when appearing as a name (e.g. "Earth's atmosphere") but writes it in lowercase when preceded by the (e.g. "the atmosphere of the earth"). It almost always appears in lowercase in colloquial expressions such as "what on earth are you doing?"[59] Composition and structure Shape Main article: Figure of the Earth World map color-coded by relative height Stratocumulus clouds over the Pacific, viewed from orbit The shape of Earth approximates an oblate spheroid, a sphere flattened along the axis from pole to pole such that there is a bulge around the equator.[60] This bulge results from the rotation of Earth, and causes the diameter at the equator to be 43 kilometres (27 mi) larger than the pole-to-pole diameter.[61] Thus the point on the surface farthest from Earth's center of mass is the Chimborazo volcano in Ecuador.[62] The average diameter of the reference spheroid is about 12,742 kilometres (7,918 mi), which is approximately 40,000 km/?, because the meter was originally defined as 1/10,000,000 of the distance from the equator to the North Pole through Paris, France.[63] Local topography deviates from this idealized spheroid, although on a global scale these deviations are small compared to Earth's radius: The maximum deviation of only 0.17% is at the Mariana Trench (10911 m below local sea level), whereas Mount Everest (8,848 m above local sea level) represents a deviation of 0.14%. If Earth were shrunk to the size of a cue ball, some areas of Earth such as mountain ranges and oceanic trenches would feel like small imperfections, whereas much of the planet, including the Great Plains and the Abyssal plains, would actually feel smoother than a cue ball.[64] Due to the equatorial bulge, the surface locations farthest from Earth's center are the summits of Mount Chimborazo in Ecuador and Huascarán in Peru.[65][66][67][68] Chemical composition of the crust[69] 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% Chimborazo, Ecuador. The point on Earth's surface farthest from its center.[65] Chemical composition See also: Abundance of elements on Earth Earth's mass is approximately 5.97×1024 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.[70] The geochemist F. W. Clarke calculated that a little more than 47% of Earth's crust consists of oxygen. The more common rock constituents of the crust are nearly all oxides; chlorine, sulfur and fluorine are the 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 most common 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), with the other constituents occurring in minute quantities.[71] Internal structure Main article: Structure of the Earth Earth's interior, like that of the other terrestrial planets, is divided into layers by their chemical or physical (rheological) properties, but unlike the other terrestrial planets, it has a distinct outer and inner core. The outer layer 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 Mohorovi?i? discontinuity, and the thickness of the crust varies: averaging 6 km (kilometers) 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 composed. Beneath the lithosphere is the asthenosphere, a relatively low-viscosity layer on which the lithosphere rides. Important changes in crystal structure within the mantle occur at 410 and 660 km 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.[72] 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.[73] The radius of the inner core is about one fifth of Earth's. Geologic layers of Earth[74] Earth-cutaway-schematic-english.svg Earth cutaway from core to exosphere. Not to scale. Depth[75] km Component Layer Density g/cm3 0–60 Lithosphere[n 7] — 0–35 Crust[n 8] 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%).[76] The major heat-producing isotopes within Earth are potassium-40, uranium-238, uranium-235, and thorium-232.[77] At the center, the temperature may be up to 6,000 °C (10,830 °F),[78] and the pressure could reach 360 GPa.[79] Because much of the heat is provided by radioactive decay, scientists postulate that early in Earth's 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 byr,[76] would have increased temperature gradients with radius, increasing the rates of mantle convection and plate tectonics, and allowing the production of uncommon igneous rocks such as komatiites that are rarely formed today.[80] Present-day major heat-producing isotopes[81] Isotope Heat release W / kg isotope Half-life years Mean mantle concentration kg isotope / kg mantle Heat release W / kg mantle 238U 94.6 × 10?6 4.47 × 109 30.8 × 10?9 2.91 × 10?12 235U 569 × 10?6 0.704 × 109 0.22 × 10?9 0.125 × 10?12 232Th 26.4 × 10?6 14.0 × 109 124 × 10?9 3.27 × 10?12 40K 29.2 × 10?6 1.25 × 109 36.9 × 10?9 1.08 × 10?12 The mean heat loss from Earth is 87 mW m?2, for a global heat loss of 4.42 × 1013 W.[82] 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.[83] More of the heat in Earth is lost through plate tectonics, by mantle upwelling associated with mid-ocean ridges. The final major mode of heat loss is through conduction through the lithosphere, the majority of which occurs under the oceans because the crust there is much thinner than that of the continents.[84] Tectonic plates Earth's major plates[85] Shows the extent and boundaries of tectonic plates, with superimposed outlines of the continents they support Plate name Area 106 km2 Pacific Plate 103.3 African Plate[n 9] 78.0 North American Plate 75.9 Eurasian Plate 67.8 Antarctic Plate 60.9 Indo-Australian Plate 47.2 South American Plate 43.6 Main article: Plate tectonics The mechanically rigid outer layer of 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.[86] 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,[87] and their motion is strongly coupled with convection patterns inside 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. Due to this recycling, most of the ocean floor is less than 100 myr old in age. The oldest oceanic crust is located in the Western Pacific, and has an estimated age of about 200 myr.[88][89] By comparison, the oldest dated continental crust is 4030 myr.[90] The seven major plates are the Pacific, North American, Eurasian, African, Antarctic, Indo-Australian, and South American. Other notable plates include the Arabian Plate, the Caribbean Plate, the Nazca Plate off the west coast of South America and the Scotia Plate in the southern Atlantic Ocean. The Australian Plate fused with the Indian Plate between 50 and 55 mya. The fastest-moving plates are the oceanic plates, with the Cocos Plate advancing at a rate of 75 mm/year[91] and the Pacific Plate moving 52–69 mm/year. At the other extreme, the slowest-moving plate is the Eurasian Plate, progressing at a typical rate of about 21 mm/year.[92] Surface Main articles: Lithosphere, Landform and Extreme points of Earth Circle frame.svg Features of Earth's solid surface shown as percentages of the planet's total surface area Oceanic ridges (22.1%) Ocean basin floors (29.8%) Continental mountains (10.3%) Continental lowlands (18.9%) Continental shelves and slopes (11.4%) Continental rise (3.8%) Volcanic island arcs, trenches, submarine volcanoes, and hills (3.7%) An aerial view of Barringer Meteor Crater in Arizona. Earth's terrain varies greatly from place to place. About 70.8%[14] of the surface is covered by water, with much of the continental shelf below sea level. This equates to 361.132 million km2 (139.43 million sq mi).[93] The submerged surface has mountainous features, including a globe-spanning mid-ocean ridge system, as well as undersea volcanoes,[61] oceanic trenches, submarine canyons, oceanic plateaus and abyssal plains. The remaining 29.2% (148.94 million km2, or 57.51 million sq mi) not covered by water consists of mountains, deserts, plains, plateaus, and other landforms. The planetary surface undergoes reshaping over geological time periods due to tectonics and erosion. The surface features built up or deformed through plate tectonics are subject to steady weathering and erosion from precipitation, thermal cycles, and chemical effects. Glaciation, coastal erosion, the build-up of coral reefs, and large meteorite impacts[94] 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.[95] Sedimentary rock is formed from the accumulation of sediment that becomes buried and compacted together. Nearly 75% of the continental surfaces are covered by sedimentary rocks, although they form about 5% of the crust.[96] 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 Earth's surface include quartz, feldspars, amphibole, mica, pyroxene and olivine.[97] Common carbonate minerals include calcite (found in limestone) and dolomite.[98] The pedosphere is the outermost layer of Earth's continental surface and is composed of soil and subject to soil formation processes. It exists at the interface of the lithosphere, atmosphere, hydrosphere and biosphere. The total arable land is 13.31% of the land surface, with 4.71% supporting permanent crops.[15] Close to 40% of Earth's land surface is used for cropland and pasture, or an estimated 1.3×107 km2 of cropland and 3.4×107 km2 of pastureland.[99] The elevation of the land surface 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.[100] Besides being divided logically into Northern and Southern hemispheres centered on the poles, Earth has been divided arbitrarily into Eastern and Western hemispheres. Earth's surface is traditionally divided into seven continents and various seas. As people settled and organized the planet, nearly all the land was divided into nations. Hydrosphere Main article: Hydrosphere Elevation histogram of Earth's surface The abundance of water on Earth's surface is a unique feature that distinguishes the "Blue Planet" from other planets in the Solar System. 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.[n 10][101] The mass of the oceans is approximately 1.35×1018 metric tons, or about 1/4400 of Earth's total mass. The oceans cover an area of 3.618×108 km2 with a mean depth of 3682 m, resulting in an estimated volume of 1.332×109 km3.[102] If all of Earth's crustal surface was at the same elevation as a smooth sphere, the depth of the resulting world ocean would be 2.7 to 2.8 km.[103][104] About 97.5% of the water is saline; the remaining 2.5% is fresh water. Most fresh water, about 68.7%, is present as ice in ice caps and glaciers.[105] The average salinity of Earth's oceans is about 35 grams of salt per kilogram of sea water (3.5% salt).[106] Most of this salt was released from volcanic activity or extracted from cool igneous rocks.[107] The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms.[108] Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir.[109] Shifts in the oceanic temperature distribution can cause significant weather shifts, such as the El Niño-Southern Oscillation.[110] Atmosphere Main article: Atmosphere of Earth A Typhoon as seen from low Earth orbit The atmospheric pressure on Earth's surface averages 101.325 kPa, with a scale height of about 8.5 km.[3] It has a composition of 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 resulting from weather and seasonal factors.[111] Earth's biosphere has significantly altered its atmosphere. Oxygenic photosynthesis evolved 2.7 bya, forming the primarily nitrogen–oxygen atmosphere of today.[112] This change enabled the proliferation of aerobic organisms as well as the formation of the ozone layer, which blocks ultraviolet solar radiation, permitting life on land. Other atmospheric functions important to life include transporting water vapor, providing useful gases, causing small meteors to burn up before they strike the surface, and moderating temperature.[113] 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. Water vapor, carbon dioxide, methane and ozone are the primary greenhouse gases in the atmosphere. Without this heat-retention effect, the average surface would be ?18 °C, in contrast to the current +15 °C, and life would likely not exist.[114] Weather and climate Main articles: Weather and Climate In this scene from Antarctica, Earth's south polar continent, ice ridges contrast with towering clouds Satellite cloud cover image of Earth using NASA's Moderate-Resolution Imaging Spectroradiometer 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 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 thermal energy.[115] 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°.[116] Ocean currents are also important factors in determining climate, particularly the thermohaline circulation that distributes thermal energy from the equatorial oceans to the polar regions.[117] The Earth in true color and false color as seen by the MESSENGER spacecraft. Water 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 falls to the surface as precipitation.[115] Most of the water is then transported to lower elevations by river systems and usually returned to the oceans or 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, topolographic features and temperature differences determine the average precipitation that falls in each region.[118] The amount of solar energy reaching Earth's surface decreases with increasing latitude. At higher latitudes the sunlight reaches the surface at lower angles and it must pass through thicker columns of the atmosphere. As a result, the mean annual air temperature at sea level decreases by about 0.4 °C per degree of latitude from the equator.[119] Earth's surface can be subdivided 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.[120] 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.[116] Upper atmosphere This view from orbit shows the full Moon partially obscured by Earth's atmosphere. NASA image Above the troposphere, the atmosphere is usually divided into the stratosphere, mesosphere, and thermosphere.[113] Each layer has a different lapse rate, defining the rate of change in temperature with height. Beyond these, the exosphere thins out into the magnetosphere, where the geomagnetic fields interact with the solar wind.[121] Within the stratosphere is the ozone layer, a component that partially shields the surface from ultraviolet light and thus is important for life on Earth. The Kármán line, defined as 100 km above Earth's surface, is a working definition for the boundary between the atmosphere and outer space.[122] Thermal energy causes some of the molecules at the outer edge of the atmosphere to increase their velocity to the point where they can escape from Earth's gravity. This causes a slow but steady leakage of the atmosphere into space. Because unfixed hydrogen has a low molecular mass, it can achieve escape velocity more readily and it leaks into outer space at a greater rate than other gases.[123] The leakage of hydrogen into space contributes to the shifting of Earth's atmosphere and surface 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.[124] Hence the ability of hydrogen to escape from the atmosphere may have influenced the nature of life that developed on Earth.[125] 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.[126] Magnetic field Diagram showing the magnetic field lines of Earth's magnetosphere. The lines are swept back in the anti-solar direction under the influence of the solar wind. Schematic of Earth's magnetosphere. The solar wind flows from left to right Main article: Earth's magnetic field The main part of the Earth's magnetic field is generated in the core, the site of a dynamo process that converts kinetic energy of fluid convective motion into electrical and magnetic field energy. The field extends outwards from the core, through the mantle, and up to Earth's surface, where it is, to rough approximation, a dipole. The poles of the dipole are located close to Earth's geographic poles. At the equator of the magnetic field, the magnetic-field strength at the surface is 3.05 × 10?5 T, with global magnetic dipole moment of 7.91 × 1015 T m3.[127] The convection movements in the core are chaotic; the magnetic poles drift and periodically change alignment. This causes field reversals at irregular intervals averaging a few times every million years. The most recent reversal occurred approximately 700,000 years ago.[128][129] Magnetosphere The extent of Earth's magnetic field in space defines the magnetosphere. Ions and electrons of the solar wind are deflected by the magnetosphere; solar wind pressure compresses the dayside of the magnetosphere, to about 10 Earth radii, and extends the nightside magnetosphere into a long tail. Since the velocity of the solar wind is greater than the speed at which wave propagate through the solar wind, a supersonic bowshock precedes the dayside magnetosphere within the solar wind. Charged particles are contained within the magnetosphere; the plasmasphere is defined by low-energy particles that essentially follow magnetic field lines as Earth rotates; the ring current is defined by medium-energy particles that drift relative to the geomagnetic field, but with paths that are still dominated by the magnetic field, and the Van Allen radiation belt are formed by high-energy particles whose motion is essentially random, but otherwise contained by the magnetosphere. During a magnetic storm, charged particles can be deflected from the outer magnetosphere, directed along field lines into Earth's ionosphere, where atmospheric atoms can be excited and ionized, causing the aurora.[130] 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 (86,400.0025 SI seconds).[131] Because Earth's solar day is now slightly longer than it was during the 19th century due to tidal deceleration, each day varies between 0 and 2 SI ms longer.[132][133] Earth's rotation period relative to the fixed stars, called its stellar day by the International Earth Rotation and Reference Systems Service (IERS), is 86,164.098903691 seconds of mean solar time (UT1), or 23h 56m 4.098903691s.[2][n 11] Earth's rotation period relative to the precessing or moving mean vernal equinox, misnamed its sidereal day, is 86,164.09053083288 seconds of mean solar time (UT1) (23h 56m 4.09053083288s) as of 1982.[2] Thus the sidereal day is shorter than the stellar day by about 8.4 ms.[134] The length of the mean solar day in SI seconds is available from the IERS for the periods 1623–2005[135] and 1962–2005.[136] Apart from meteors within the atmosphere and low-orbiting satellites, the main apparent motion of celestial bodies in Earth's sky is to the west at a rate of 15°/h = 15'/min. For bodies near the celestial equator, this is equivalent to an apparent diameter of the Sun or the Moon every two minutes; from Earth's surface, the apparent sizes of the Sun and the Moon are approximately the same.[137][138] 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. This gives an apparent movement of the Sun eastward with respect to the stars at a rate of about 1°/day, which is one apparent Sun or Moon diameter every 12 hours. Due to this motion, on average it takes 24 hours—a solar day—for Earth to complete a full rotation about its axis so that the Sun returns to the meridian. The orbital speed of Earth averages about 29.8 km/s (107,000 km/h), which is fast enough to travel a distance equal to Earth's diameter, about 12,742 km, in seven minutes, and the distance to the Moon, 384,000 km, in about 3.5 hours.[3] The Moon and Earth orbit a common barycenter every 27.32 days relative to the background stars. When combined with Earth–Moon system's common orbit around the Sun, the period of the synodic month, from new moon to new moon, is 29.53 days. Viewed from the celestial north pole, the motion of Earth, the Moon, and their axial rotations are all counterclockwise. Viewed from a vantage point above the north poles of both the Sun and Earth, Earth orbits in a counterclockwise direction about the Sun. The orbital and axial planes are not precisely aligned: Earth's axis is tilted some 23.4 degrees from the perpendicular to the Earth–Sun plane (the ecliptic), and the Earth–Moon plane is tilted up to ±5.1 degrees against the Earth–Sun plane. Without this tilt, there would be an eclipse every two weeks, alternating between lunar eclipses and solar eclipses.[3][139] The Hill sphere, or gravitational sphere of influence, of Earth is about 1.5 Gm or 1,500,000 km in radius.[140][n 12] This is the maximum distance at which the Earth's gravitational influence is stronger than the more distant Sun and planets. Objects must orbit Earth within this radius, or they can become unbound by the gravitational perturbation of the Sun. Earth, along with the Solar System, is situated in the Milky Way galaxy and orbits about 28,000 light years from the center of the galaxy. It is about 20 light years above the galactic plane in the Orion spiral arm.[141] Axial tilt and seasons Main article: Axial tilt Due to Earth's axial tilt, the amount of sunlight reaching any given point on the surface varies over the course of the year. This causes 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. In northern temperate latitudes, the sun rises north of true east during the summer solstice, and sets north of true west, reversing in the winter. The sun rises south of true east in the summer for the southern temperate zone, and sets south of true west. Above the Arctic Circle, an extreme case is reached where there is no daylight at all for part of the year, up to six months at the North Pole itself, a polar night. In the southern hemisphere the situation is exactly reversed, with the South Pole oriented opposite the direction of the North Pole. Six months later, this pole will experience a midnight sun, a day of 24 hours, again reversing with the South Pole. 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. In the northern hemisphere, 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. In the southern hemisphere, the situation is reversed, with the summer and winter solstices exchanged and the spring and autumnal equinox dates swapped.[142] NASA's Cassini spacecraft photographs Earth and the Moon (visible bottom-right) from Saturn (July 19, 2013). The angle of Earth's axial tilt is relatively stable over long periods of time. Its axials tilt does undergo nutation; a slight, irregular motion with a main period of 18.6 years.[143] The orientation (rather than the angle) of 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 the Moon on Earth's equatorial bulge. The poles also migrate a few meters across Earth's 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. Earth's rotational velocity also varies in a phenomenon known as length-of-day variation.[144] In modern times, Earth's perihelion occurs around January 3, and its aphelion around July 4. 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 causes an increase of about 6.9%[n 13] in solar energy reaching Earth at perihelion relative to aphelion. Because the southern hemisphere is tilted toward the Sun at about the same time that 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. 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.[145] Habitability See also: Planetary habitability This ancient impact crater, now filled with water, marks Earth's surface A planet that can sustain life is termed habitable, even if life did not originate there. Earth provides liquid water—an environment where complex organic molecules can assemble and interact, and sufficient energy to sustain metabolism.[146] The distance of 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 current climatic conditions at the surface.[147] Biosphere Main article: Biosphere Coral reef and beach A planet's life forms are sometimes said to form a "biosphere". Earth's biosphere is generally believed to have begun evolving about 3.5 bya.[112] The biosphere is divided into a number of biomes, inhabited by broadly similar plants and animals. On land, biomes are separated primarily by differences in latitude, height above sea level and humidity. Terrestrial biomes lying within the Arctic or Antarctic Circles, at high altitudes or in extremely arid areas are relatively barren of plant and animal life; species diversity reaches a peak in humid lowlands at equatorial latitudes.[148] Evolution of life Main article: Evolutionary history of life Speculative phylogenetic tree of life on Earth based on rRNA analysis Highly energetic chemical reactions are thought to have produced self–replicating molecules around four billion years ago. This was followed a half billion years later by the last common ancestor of all life.[149] The development of photosynthesis allowed the Sun's energy to be harvested directly by life forms; the resultant molecular oxygen (O2) accumulated in the atmosphere and due to interaction with high energy solar radiation, formed a layer of protective ozone (O3) in the upper atmosphere.[112] The incorporation of smaller cells within larger ones resulted in the development of complex cells called eukaryotes.[150] 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 Earth's surface.[151] The earliest fossil evidences for life are graphite found to be biogenic in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland[152] and microbial mat fossils found in 3.48 billion-year-old sandstone discovered in Western Australia.[153][154] Since the 1960s, it has been hypothesized that severe glacial action between 750 and 580 mya, 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.[155] Following the Cambrian explosion, about 535 mya, there have been five major mass extinctions.[156] The most recent such event was 66 mya, when an asteroid impact triggered the extinction of the (non-avian) dinosaurs and other large reptiles, but spared some small animals such as mammals, which then resembled shrews. Over the past 66 myr, mammalian life has diversified, and several million years ago an African ape-like animal such as Orrorin tugenensis gained the ability to stand upright.[157] This enabled tool use and encouraged communication that provided the nutrition and stimulation needed for a larger brain, which allowed the evolution of the human race. The development of agriculture, and then civilization, allowed humans to influence Earth in a short time span as no other life form had,[158] affecting both the nature and quantity of other life forms. Natural resources and land use Main articles: Natural resource and Land use Estimated human land use, 2000[159] Land use Mha Cropland 1,510–1,611 Pastures 2,500–3,410 Natural forests 3,143–3,871 Planted forests 126–215 Urban areas 66–351 Unused, productive land 356–445 Earth provides resources that are exploitable by humans for useful purposes. Some of these are non-renewable resources, such as fossil fuels, that are difficult to replenish on a short time scale. Large deposits of fossil fuels are obtained from Earth's crust, consisting of coal, petroleum and natural gas. These deposits are used by humans both for energy production and as feedstock for chemical production. Mineral ore bodies have also been formed within the crust through a process of ore genesis, resulting from actions of magmatism, erosion and plate tectonics.[160] These bodies form concentrated sources for many metals and other useful elements. Earth's biosphere produces many useful biological products for humans, including 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.[161] In 1980, 5,053 Mha (50.53 million km2) of Earth's land surface consisted of forest and woodlands, 6,788 Mha (67.88 million km2) was grasslands and pasture, and 1,501 Mha (15.01 million km2) was cultivated as croplands.[162] The estimated amount of irrigated land in 1993 was 2,481,250 square kilometres (958,020 sq mi).[15] Humans also live on the land by using building materials to construct shelters. Natural and environmental hazards Earth's volcanoes can inject gas and ash into the atmosphere. A volcano injecting hot ash into the atmosphere Large areas of Earth's surface are subject to extreme weather such as tropical cyclones, hurricanes, or typhoons that dominate life in those areas. From 1980 to 2000, these events caused an average of 11,800 deaths per year.[163] Many places are subject to earthquakes, landslides, tsunamis, volcanic eruptions, tornadoes, sinkholes, blizzards, floods, droughts, wildfires, 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. According to the United Nations, 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 and a global rise in average sea levels.[164] Human geography Main articles: Human geography and World The seven continents of Earth[165] North America South America Antarctica Europe Africa Asia Oceania v t e A composite picture consisting of DMSP/OLS ground-illumination data for 2000 placed on a simulated night-time image of Earth. Cartography, the study and practice of map-making, and geography, the study of the lands, features, inhabitants and phenomena on Earth, have historically been the disciplines devoted to depicting 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's human population reached approximately seven billion on October 31, 2011.[166] Projections indicate that the world's human population will reach 9.2 billion in 2050.[167] 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.[168] It is estimated that one-eighth of Earth's surface is suitable for humans to live on – three-quarters of Earth's surface is covered by oceans, leaving one quarter as land. Half of that land area is desert (14%),[169] high mountains (27%),[170] or other unsuitable terrain. The northernmost permanent settlement in the world is Alert, on Ellesmere Island in Nunavut, Canada.[171] (82°28?N) The southernmost is the Amundsen–Scott South Pole Station, in Antarctica, almost exactly at the South Pole. (90°S) Independent sovereign nations claim the planet's entire land surface, except for some parts of Antarctica, a few land parcels along the Danube river's western bank, and the odd unclaimed area of Bir Tawil between Egypt and Sudan. As of 2013, there are 205 de facto sovereign states, including the 193 United Nations member states. In addition, there are 59 dependent territories, and a number of autonomous areas, territories under dispute and other entities.[15] 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.[172] 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.[173] The U.N. serves primarily as a forum for international diplomacy and international law. When the consensus of the membership permits, it provides a mechanism for armed intervention.[174] The first human to orbit Earth was Yuri Gagarin on April 12, 1961.[175] In total, about 487 people have visited outer space and reached orbit as of 30 July 2010, and, of these, twelve have walked on the Moon.[176][177][178] Normally, the only humans in space are those on the International Space Station. The station's crew, made up of six people, is usually replaced every six months.[179] The farthest that humans have travelled from Earth is 400,171 km, achieved during the Apollo 13 mission in 1970.[180] Cultural and historical viewpoint Main article: Earth in culture The first "earthrise" ever seen directly by humans, photographed by astronauts on board Apollo 8. The standard astronomical symbol of Earth consists of a cross circumscribed by a circle, Earth symbol.svg.[181] Unlike other planets in the Solar System, humankind did not begin to view Earth as a moving object until the 16th century.[182] Earth has often been personified as a deity, in particular a goddess. In many cultures a mother goddess is also portrayed as a fertility deity. Creation myths in many religions recall a story involving the creation of Earth by a supernatural deity or deities. A variety of religious groups, often associated with fundamentalist branches of Protestantism[183] or Islam,[184] 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 Earth and the origin and development of life.[185] Such assertions are opposed by the scientific community[186][187] and by other religious groups.[188][189][190] A prominent example is the creation–evolution controversy. In the past, there were varying levels of belief in a flat Earth,[191] but this was displaced by spherical Earth, a concept that has been credited to Pythagoras (6th century BC).[192] Human cultures have developed many views of the planet, including its personification as a planetary deity, its shape as flat, its position as the center of the universe, and in the modern Gaia Principle, as a single, self-regulating organism in its own right. Chronology Formation Main article: History of the Earth Artist's impression of the birth of the Solar System The earliest material found in the Solar System is dated to 4.5672±0.0006 billion years ago (bya);[193] therefore, it is inferred that Earth must have been formed by accretion around this time. By 4.54±0.04 bya[37] the primordial Earth had formed. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets grow out of that in tandem with the star. A nebula contains gas, ice grains and dust (including primordial nuclides). In nebular theory planetesimals commence forming as particulate accrues by cohesive clumping and then by gravity. The assembly of the primordial Earth proceeded for 10–20 myr.[194] The Moon formed shortly thereafter, about 4.53 bya.[195] The formation of the Moon remains a topic of debate. The working hypothesis is that it formed by accretion from material loosed from Earth after a Mars-sized object, named Theia, impacted with Earth.[196] This model, however, is not self-consistent. In this scenario, the mass of Theia is 10% of that of Earth,[197] it impacted Earth with a glancing blow,[198] and some of its mass merges with Earth. Between approximately 3.8 and 4.1 bya, numerous asteroid impacts during the Late Heavy Bombardment caused significant changes to the greater surface environment of the Moon, and by inference, to Earth. Geological history Main article: Geological history of Earth Earth's atmosphere and oceans formed by volcanic activity and outgassing that included water vapor. The origin of the world's oceans was condensation augmented by water and ice delivered by asteroids, proto-planets, and comets.[199] In this model, atmospheric "greenhouse gases" kept the oceans from freezing when the newly forming Sun had only 70% of its current luminosity.[200] By 3.5 bya, the Earth's magnetic field was established, which helped prevent the atmosphere from being stripped away by the solar wind.[201] A crust formed when the molten outer layer of Earth cooled to form a solid as the accumulated water vapor began to act in the atmosphere. The two models[202] that explain land mass propose either a steady growth to the present-day forms[203] or, more likely, a rapid growth[204] early in Earth history[205] followed by a long-term steady continental area.[206][207][208] Continents formed by plate tectonics, a process ultimately driven by the continuous loss of heat from Earth's interior. On time scales lasting hundreds of millions of years, the supercontinents have formed and broken up three times. Roughly 750 mya (million years ago), one of the earliest known supercontinents, Rodinia, began to break apart. The continents later recombined to form Pannotia, 600–540 mya, then finally Pangaea, which also broke apart 180 mya.[209] The present pattern of ice ages began about 40 mya and then intensified during the Pleistocene about 3 mya. High-latitude regions have since undergone repeated cycles of glaciation and thaw, repeating every 40–100000 years. The last continental glaciation ended 10,000 years ago.[210] Predicted future Main article: Future of the Earth Estimates on how much longer the planet will be able to continue to support life range from 500 million years (myr), to as long as 2.3 billion years (byr).[211][212][213] 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 byr and by 40% over the next 3.5 byr.[214] Climate models indicate that the rise in radiation reaching Earth is likely to have dire consequences, including the loss of the planet's oceans.[215] Earth's increasing surface temperature will accelerate the inorganic CO2 cycle, reducing its concentration to levels lethally low for plants (10 ppm for C4 photosynthesis) in approximately 500-900 myr.[211] 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.[216] After another billion years all surface water will have disappeared[212] and the mean global temperature will reach 70 °C[216] (158 °F). Earth is expected to be effectively habitable for about another 500 myr from that point,[211] although this may be extended up to 2.3 byr if the nitrogen is removed from the atmosphere.[213] Even if the Sun were eternal and stable, 27% of the water in the modern oceans will descend to the mantle in one billion years, due to reduced steam venting from mid-ocean ridges.[217] 14 billion year timeline showing Sun's present age at 4.6 byr; from 6 byr Sun gradually warming, becoming a red dwarf at 10 byr, "soon" followed by its transformation into a white dwarf Life cycle of the Sun The Sun, as part of its evolution, will become a red giant in about 5 byr. Models predict that the Sun will expand to roughly 1 AU (150,000,000 km), which is about 250 times its present radius.[214][218] Earth's fate is less clear. As a red giant, the Sun will lose roughly 30% of its mass, so, without tidal effects, Earth will move to an orbit 1.7 AU (250,000,000 km) from the Sun, when the star reaches its maximum radius. The planet was, therefore, initially expected to escape envelopment by the expanded Sun's sparse outer atmosphere, though most, if not all, remaining life would have been destroyed by the Sun's increased luminosity (peaking at about 5,000 times its present level).[214] A 2008 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 vaporized.[218] After that, the Sun's core will collapse into a white dwarf, as its outer layers are ejected into space as a planetary nebula. The matter that once made up Earth will be released into interstellar space, where it may one day become incorporated into a new generation of planets and other celestial bodies. See also: Risks to civilization, humans, and planet Earth Moon Full moon as seen from Earth's Northern Hemisphere Characteristics Diameter 3,474.8 km Mass 7.349×1022 kg Semi-major axis 384,400 km Orbital period 27 d 7 h 43.7 m Details of the Earth–Moon system, showing the radius of each object and the Earth-Moon barycenter. The Moon's axis is located by Cassini's third law. Earth and the Moon were imaged by Mariner 10 from 2.6 million km while completing the first ever Earth–Moon encounter by a spacecraft capable of returning high-resolution digital color-image data. Main article: Moon The Moon is a relatively large, terrestrial, planet-like satellite, with a diameter about one-quarter of Earth's. It is the largest moon in the Solar System relative to the size of its planet, although Charon is larger relative to the dwarf planet Pluto. The natural satellites of other planets are also referred to as "moons", after Earth's. The gravitational attraction between Earth and the 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 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. Due to their tidal interaction, the Moon recedes from Earth at the rate of approximately 38 mm/yr. Over millions of years, these tiny modifications—and the lengthening of Earth's day by about 23 µs/yr—add up to significant changes.[219] During the Devonian period, for example, (approximately 410 mya) there were 400 days in a year, with each day lasting 21.8 hours.[220] 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.[221] Some theorists believe that without this stabilization against the torques applied by the Sun and planets to 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.[222] Viewed from Earth, the Moon is just far enough away to have almost 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.[138] This allows total and annular solar eclipses to occur on Earth. 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 Earth's crust.[223] Asteroids and artificial satellites The International Space Station is an artificial satellite in orbit around Earth. Earth has at least five co-orbital asteroids, including 3753 Cruithne and 2002 AA29.[224][225] A trojan asteroid companion, 2010 TK7, is librating around the leading Lagrange triangular point, L4, in the Earth's orbit around the Sun.[226][227] As of 2011, there were 931 operational, human-made satellites orbiting Earth.[228] There are also inoperative satellites and over 300,000 pieces of space debris. Earth's largest artificial satellite is the International Space Station. See also Celestial sphere Earth physical characteristics tables Earth science Notes Jump up ^ All astronomical quantities vary, both secularly and periodically. The quantities given are the values at the instant J2000.0 of the secular variation, ignoring all periodic variations. ^ Jump up to: a b aphelion = a × (1 + e); perihelion = a × (1 – e), where a is the semi-major axis and e is the eccentricity. The difference between Earth's perihelion and aphelion is 5 million kilometers. Jump up ^ Due to natural fluctuations, ambiguities surrounding ice shelves, and mapping conventions for vertical datums, exact values for land and ocean coverage are not meaningful. Based on data from the Vector Map and Global Landcover datasets, extreme values for coverage of lakes and streams are 0.6% and 1.0% of Earth's surface. The ice shields of Antarctica and Greenland are counted as land, even though much of the rock that supports them lies below sea level. Jump up ^ Particularly as the setting for human civilization and experience.[25] Jump up ^ From the name of the Greek earth goddess, but now particularly used for the global ecosystem.[26] Jump up ^ The number of solar days is one less than the number of sidereal days because the orbital motion of Earth around the Sun causes one additional revolution of the planet about its axis. Jump up ^ Locally varies between 5 and 200 km. Jump up ^ Locally varies between 5 and 70 km. Jump up ^ Including the Somali Plate, which is being formed out of the African Plate. See: Chorowicz, Jean (October 2005). "The East African rift system". Journal of African Earth Sciences 43 (1–3): 379–410. Bibcode:2005JAfES..43..379C. doi:10.1016/j.jafrearsci.2005.07.019. Jump up ^ This is the measurement taken by the vessel Kaik? in March 1995 and is believed to be the most accurate measurement to date. See the Challenger Deep article for more details. Jump up ^ The ultimate source of these figures, uses the term "seconds of UT1" instead of "seconds of mean solar time".—Aoki, S.; Kinoshita, H.; Guinot, B.; Kaplan, G. H.; McCarthy, D. D.; Seidelmann, P. K. (1982). "The new definition of universal time". Astronomy and Astrophysics 105 (2): 359–61. Bibcode:1982A&A...105..359A. Jump up ^ For Earth, the Hill radius is R_H = a\left ( \frac{m}{3M} \right )^{\frac{1}{3}}, where m is the mass of Earth, a is an astronomical unit, and M is the mass of the Sun. So the radius in A.U. is about \left ( \frac{1}{3 \cdot 332,946} \right )^{\frac{1}{3}} = 0.01. Jump up ^ Aphelion is 103.4% of the distance to perihelion. Due to the inverse square law, the radiation at perihelion is about 106.9% the energy at aphelion. References ^ Jump up to: a b Standish E.M. "Keplerian Elements for Approximate Positions of the Major Planets". Retrieved 15 February 2015. ^ Jump up to: a b c d Staff (2007-08-07). "Useful Constants". International Earth Rotation and Reference Systems Service. Retrieved 2008-09-23. ^ Jump up to: a b c d e f g h i j k l Williams, David R. (2004-09-01). "Earth Fact Sheet". NASA. Retrieved 2010-08-09. Jump up ^ "Earth Mean Anomaly". Wolfram Alpha. Retrieved 30 December 2014. Jump up ^ Allen, Clabon Walter; Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 294. ISBN 0-387-98746-0. Retrieved 2011-03-13. Jump up ^ Cain, Fraser (24 October 2013). "How Many Satellites Are in Space?". Universe Today. Retrieved 1 February 2014. Jump up ^ Various (2000). David R. Lide, ed. Handbook of Chemistry and Physics (81st ed.). CRC. ISBN 0-8493-0481-4. Jump up ^ "Selected Astronomical Constants, 2011". The Astronomical Almanac. Archived from the original on 2013-08-26. Retrieved 2011-02-25. ^ Jump up to: a b World Geodetic System (WGS-84). Available online from National Geospatial-Intelligence Agency. Jump up ^ Cazenave, Anny (1995). "Geoid, Topography and Distribution of Landforms". In Ahrens, Thomas J. Global earth physics a handbook of physical constants (PDF). Washington, DC: American Geophysical Union. ISBN 0-87590-851-9. Archived from the original on 2006-10-16. Retrieved 2008-08-03. Jump up ^ IERS Working Groups (2003). McCarthy, Dennis D.; Petit, Gérard, ed. General Definitions and Numerical Standards. IERS Technical Note No. 32 (U.S. Naval Observatory and Bureau International des Poids et Mesures). Archived from the original on 2010-02-01. Retrieved 2008-08-03. Jump up ^ Humerfelt, Sigurd (October 26, 2010). "How WGS 84 defines Earth". Retrieved 2011-04-29. Jump up ^ Earth's circumference is almost exactly 40,000 km because the metre was calibrated on this measurement—more specifically, 1/10-millionth of the distance between the poles and the equator. ^ Jump up to: a b Pidwirny, Michael (2006-02-02). "Surface area of our planet covered by oceans and continents.(Table 8o-1)". University of British Columbia, Okanagan. Retrieved 2007-11-26. ^ Jump up to: a b c d Staff (2008-07-24). "World". The World Factbook. Central Intelligence Agency. Retrieved 2008-08-05. Jump up ^ "Solar System Exploration: Earth: Facts & Figures". NASA. 13 December 2012. Retrieved 22 January 2012. Jump up ^ The international system of units (SI) (2008 ed.). United States Department of Commerce, NIST Special Publication 330. p. 52. Jump up ^ Williams, James G. (1994). "Contributions to the Earth's obliquity rate, precession, and nutation". The Astronomical Journal 108: 711. Bibcode:1994AJ....108..711W. doi:10.1086/117108. ISSN 0004-6256. Jump up ^ Allen, Clabon Walter; Cox, Arthur N. (2000). Allen's Astrophysical Quantities. Springer. p. 296. ISBN 0-387-98746-0. Retrieved 2010-08-17. Jump up ^ Arthur N. Cox, ed. (2000). Allen's Astrophysical Quantities (4th ed.). New York: AIP Press. p. 244. ISBN 0-387-98746-0. Retrieved 2010-08-17. Jump up ^ "World: Lowest Temperature". WMO Weather and Clim

So, there's a man crawling through the desert. He'd decided to try his SUV in a little bit of cross-country travel, had great fun zooming over the badlands and through the sand, got lost, hit a big rock, and then he couldn't get it started again. There were no cell phone towers anywhere near, so his cell phone was useless. He had no family, his parents had died a few years before in an auto accident, and his few friends had no idea he was out here. He stayed with the car for a day or so, but his one bottle of water ran out and he was getting thirsty. He thought maybe he knew the direction back, now that he'd paid attention to the sun and thought he'd figured out which way was north, so he decided to start walking. He figured he only had to go about 30 miles or so and he'd be back to the small town he'd gotten gas in last. He thinks about walking at night to avoid the heat and sun, but based upon how dark it actually was the night before, and given that he has no flashlight, he's afraid that he'll break a leg or step on a rattlesnake. So, he puts on some sun block, puts the rest in his pocket for reapplication later, brings an umbrella he'd had in the back of the SUV with him to give him a little shade, pours the windshield wiper fluid into his water bottle in case he gets that desperate, brings his pocket knife in case he finds a cactus that looks like it might have water in it, and heads out in the direction he thinks is right. He walks for the entire day. By the end of the day he's really thirsty. He's been sweating all day, and his lips are starting to crack. He's reapplied the sunblock twice, and tried to stay under the umbrella, but he still feels sunburned. The windshield wiper fluid sloshing in the bottle in his pocket is really getting tempting now. He knows that it's mainly water and some ethanol and coloring, but he also knows that they add some kind of poison to it to keep people from drinking it. He wonders what the poison is, and whether the poison would be worse than dying of thirst. He pushes on, trying to get to that small town before dark. By the end of the day he starts getting worried. He figures he's been walking at least 3 miles an hour, according to his watch for over 10 hours. That means that if his estimate was right that he should be close to the town. But he doesn't recognize any of this. He had to cross a dry creek bed a mile or two back, and he doesn't remember coming through it in the SUV. He figures that maybe he got his direction off just a little and that the dry creek bed was just off to one side of his path. He tells himself that he's close, and that after dark he'll start seeing the town lights over one of these hills, and that'll be all he needs. As it gets dim enough that he starts stumbling over small rocks and things, he finds a spot and sits down to wait for full dark and the town lights. Full dark comes before he knows it. He must have dozed off. He stands back up and turns all the way around. He sees nothing but stars. He wakes up the next morning feeling absolutely lousy. His eyes are gummy and his mouth and nose feel like they're full of sand. He so thirsty that he can't even swallow. He barely got any sleep because it was so cold. He'd forgotten how cold it got at night in the desert and hadn't noticed it the night before because he'd been in his car. He knows the Rule of Threes - three minutes without air, three days without water, three weeks without food - then you die. Some people can make it a little longer, in the best situations. But the desert heat and having to walk and sweat isn't the best situation to be without water. He figures, unless he finds water, this is his last day. He rinses his mouth out with a little of the windshield wiper fluid. He waits a while after spitting that little bit out, to see if his mouth goes numb, or he feels dizzy or something. Has his mouth gone numb? Is it just in his mind? He's not sure. He'll go a little farther, and if he still doesn't find water, he'll try drinking some of the fluid. Then he has to face his next, harder question - which way does he go from here? Does he keep walking the same way he was yesterday (assuming that he still knows which way that is), or does he try a new direction? He has no idea what to do. Looking at the hills and dunes around him, he thinks he knows the direction he was heading before. Just going by a feeling, he points himself somewhat to the left of that, and starts walking. As he walks, the day starts heating up. The desert, too cold just a couple of hours before, soon becomes an oven again. He sweats a little at first, and then stops. He starts getting worried at that - when you stop sweating he knows that means you're in trouble - usually right before heat stroke. He decides that it's time to try the windshield wiper fluid. He can't wait any longer - if he passes out, he's dead. He stops in the shade of a large rock, takes the bottle out, opens it, and takes a mouthful. He slowly swallows it, making it last as long as he can. It feels so good in his dry and cracked throat that he doesn't even care about the nasty taste. He takes another mouthful, and makes it last too. Slowly, he drinks half the bottle. He figures that since he's drinking it, he might as well drink enough to make some difference and keep himself from passing out. He's quit worrying about the denaturing of the wiper fluid. If it kills him, it kills him - if he didn't drink it, he'd die anyway. Besides, he's pretty sure that whatever substance they denature the fluid with is just designed to make you sick - their way of keeping winos from buying cheap wiper fluid for the ethanol content. He can handle throwing up, if it comes to that. He walks. He walks in the hot, dry, windless desert. Sand, rocks, hills, dunes, the occasional scrawny cactus or dried bush. No sign of water. Sometimes he'll see a little movement to one side or the other, but whatever moved is usually gone before he can focus his eyes on it. Probably birds, lizards, or mice. Maybe snakes, though they usually move more at night. He's careful to stay away from the movements. After a while, he begins to stagger. He's not sure if it's fatigue, heat stroke finally catching him, or maybe he was wrong and the denaturing of the wiper fluid was worse than he thought. He tries to steady himself, and keep going. After more walking, he comes to a large stretch of sand. This is good! He knows he passed over a stretch of sand in the SUV - he remembers doing donuts in it. Or at least he thinks he remembers it - he's getting woozy enough and tired enough that he's not sure what he remembers any more or if he's hallucinating. But he thinks he remembers it. So he heads off into it, trying to get to the other side, hoping that it gets him closer to the town. He was heading for a town, wasn't he? He thinks he was. He isn't sure any more. He's not even sure how long he's been walking any more. Is it still morning? Or has it moved into afternoon and the sun is going down again? It must be afternoon - it seems like it's been too long since he started out. He walks through the sand. After a while, he comes to a big dune in the sand. This is bad. He doesn't remember any dunes when driving over the sand in his SUV. Or at least he doesn't think he remembers any. This is bad. But, he has no other direction to go. Too late to turn back now. He figures that he'll get to the top of the dune and see if he can see anything from there that helps him find the town. He keeps going up the dune. Halfway up, he slips in the bad footing of the sand for the second or third time, and falls to his knees. He doesn't feel like getting back up - he'll just fall down again. So, he keeps going up the dune on his hand and knees. While crawling, if his throat weren't so dry, he'd laugh. He's finally gotten to the hackneyed image of a man lost in the desert - crawling through the sand on his hands and knees. If would be the perfect image, he imagines, if only his clothes were more ragged. The people crawling through the desert in the cartoons always had ragged clothes. But his have lasted without any rips so far. Somebody will probably find his dessicated corpse half buried in the sand years from now, and his clothes will still be in fine shape - shake the sand out, and a good wash, and they'd be wearable again. He wishes his throat were wet enough to laugh. He coughs a little instead, and it hurts. He finally makes it to the top of the sand dune. Now that he's at the top, he struggles a little, but manages to stand up and look around. All he sees is sand. Sand, and more sand. Behind him, about a mile away, he thinks he sees the rocky ground he left to head into this sand. Ahead of him, more dunes, more sand. This isn't where he drove his SUV. This is Hell. Or close enough. Again, he doesn't know what to do. He decides to drink the rest of the wiper fluid while figuring it out. He takes out the bottle, and is removing the cap, when he glances to the side and sees something. Something in the sand. At the bottom of the dune, off to the side, he sees something strange. It's a flat area, in the sand. He stops taking the cap of the bottle off, and tries to look closer. The area seems to be circular. And it's dark - darker than the sand. And, there seems to be something in the middle of it, but he can't tell what it is. He looks as hard as he can, and still can tell from here. He's going to have to go down there and look. He puts the bottle back in his pocket, and starts to stumble down the dune. After a few steps, he realizes that he's in trouble - he's not going to be able to keep his balance. After a couple of more sliding, tottering steps, he falls and starts to roll down the dune. The sand it so hot when his body hits it that for a minute he thinks he's caught fire on the way down - like a movie car wreck flashing into flames as it goes over the cliff, before it ever even hits the ground. He closes his eyes and mouth, covers his face with his hands, and waits to stop rolling. He stops, at the bottom of the dune. After a minute or two, he finds enough energy to try to sit up and get the sand out of his face and clothes. When he clears his eyes enough, he looks around to make sure that the dark spot in the sand it still there and he hadn't just imagined it. So, seeing the large, flat, dark spot on the sand is still there, he begins to crawl towards it. He'd get up and walk towards it, but he doesn't seem to have the energy to get up and walk right now. He must be in the final stages of dehydration he figures, as he crawls. If this place in the sand doesn't have water, he'll likely never make it anywhere else. This is his last chance. He gets closer and closer, but still can't see what's in the middle of the dark area. His eyes won't quite focus any more for some reason. And lifting his head up to look takes so much effort that he gives up trying. He just keeps crawling. Finally, he reaches the area he'd seen from the dune. It takes him a minute of crawling on it before he realizes that he's no longer on sand - he's now crawling on some kind of dark stone. Stone with some kind of marking on it - a pattern cut into the stone. He's too tired to stand up and try to see what the pattern is - so he just keeps crawling. He crawls towards the center, where his blurry eyes still see something in the middle of the dark stone area. His mind, detached in a strange way, notes that either his hands and knees are so burnt by the sand that they no longer feel pain, or that this dark stone, in the middle of a burning desert with a pounding, punishing sun overhead, doesn't seem to be hot. It almost feels cool. He considers lying down on the nice cool surface. Cool, dark stone. Not a good sign. He must be hallucinating this. He's probably in the middle of a patch of sand, already lying face down and dying, and just imagining this whole thing. A desert mirage. Soon the beautiful women carrying pitchers of water will come up and start giving him a drink. Then he'll know he's gone. He decides against laying down on the cool stone. If he's going to die here in the middle of this hallucination, he at least wants to see what's in the center before he goes. He keeps crawling. It's the third time that he hears the voice before he realizes what he's hearing. He would swear that someone just said, "Greetings, traveler. You do not look well. Do you hear me?" He stops crawling. He tries to look up from where he is on his hands and knees, but it's too much effort to lift his head. So he tries something different - he leans back and tries to sit up on the stone. After a few seconds, he catches his balance, avoids falling on his face, sits up, and tries to focus his eyes. Blurry. He rubs his eyes with the back of his hands and tries again. Better this time. Yep. He can see. He's sitting in the middle of a large, flat, dark expanse of stone. Directly next to him, about three feet away, is a white post or pole about two inches in diameter and sticking up about four or five feet out of the stone, at an angle. And wrapped around this white rod, tail with rattle on it hovering and seeming to be ready to start rattling, is what must be a fifteen foot long desert diamondback rattlesnake, looking directly at him. He stares at the snake in shock. He doesn't have the energy to get up and run away. He doesn't even have the energy to crawl away. This is it, his final resting place. No matter what happens, he's not going to be able to move from this spot. Well, at least dying of a bite from this monster should be quicker than dying of thirst. He'll face his end like a man. He struggles to sit up a little straighter. The snake keeps watching him. He lifts one hand and waves it in the snake's direction, feebly. The snake watches the hand for a moment, then goes back to watching the man, looking into his eyes. Hmmm. Maybe the snake had no interest in biting him? It hadn't rattled yet - that was a good sign. Maybe he wasn't going to die of snake bite after all. He then remembers that he'd looked up when he'd reached the center here because he thought he'd heard a voice. He was still very woozy - he was likely to pass out soon, the sun still beat down on him even though he was now on cool stone. He still didn't have anything to drink. But maybe he had actually heard a voice. This stone didn't look natural. Nor did that white post sticking up out of the stone. Someone had to have built this. Maybe they were still nearby. Maybe that was who talked to him. Maybe this snake was even their pet, and that's why it wasn't biting. He tries to clear his throat to say, "Hello," but his throat is too dry. All that comes out is a coughing or wheezing sound. There is no way he's going to be able to talk without something to drink. He feels his pocket, and the bottle with the wiper fluid is still there. He shakily pulls the bottle out, almost losing his balance and falling on his back in the process. This isn't good. He doesn't have much time left, by his reckoning, before he passes out. He gets the lid off of the bottle, manages to get the bottle to his lips, and pours some of the fluid into his mouth. He sloshes it around, and then swallows it. He coughs a little. His throat feels better. Maybe he can talk now. He tries again. Ignoring the snake, he turns to look around him, hoping to spot the owner of this place, and croaks out, "Hello? Is there anyone here?" He hears, from his side, "Greetings. What is it that you want?" He turns his head, back towards the snake. That's where the sound had seemed to come from. The only thing he can think of is that there must be a speaker, hidden under the snake, or maybe built into that post. He decides to try asking for help. "Please," he croaks again, suddenly feeling dizzy, "I'd love to not be thirsty any more. I've been a long time without water. Can you help me?" Looking in the direction of the snake, hoping to see where the voice was coming from this time, he is shocked to see the snake rear back, open its mouth, and speak. He hears it say, as the dizziness overtakes him and he falls forward, face first on the stone, "Very well. Coming up." A piercing pain shoots through his shoulder. Suddenly he is awake. He sits up and grabs his shoulder, wincing at the throbbing pain. He's momentarily disoriented as he looks around, and then he remembers - the crawl across the sand, the dark area of stone, the snake. He sees the snake, still wrapped around the tilted white post, still looking at him. He reaches up and feels his shoulder, where it hurts. It feels slightly wet. He pulls his fingers away and looks at them - blood. He feels his shoulder again - his shirt has what feels like two holes in it - two puncture holes - they match up with the two aching spots of pain on his shoulder. He had been bitten. By the snake. "It'll feel better in a minute." He looks up - it's the snake talking. He hadn't dreamed it. Suddenly he notices - he's not dizzy any more. And more importantly, he's not thirsty any more - at all! "Have I died? Is this the afterlife? Why are you biting me in the afterlife?" "Sorry about that, but I had to bite you," says the snake. "That's the way I work. It all comes through the bite. Think of it as natural medicine." "You bit me to help me? Why aren't I thirsty any more? Did you give me a drink before you bit me? How did I drink enough while unconscious to not be thirsty any more? I haven't had a drink for over two days. Well, except for the windshield wiper fluid... hold it, how in the world does a snake talk? Are you real? Are you some sort of Disney animation?" "No," says the snake, "I'm real. As real as you or anyone is, anyway. I didn't give you a drink. I bit you. That's how it works - it's what I do. I bite. I don't have hands to give you a drink, even if I had water just sitting around here." The man sat stunned for a minute. Here he was, sitting in the middle of the desert on some strange stone that should be hot but wasn't, talking to a snake that could talk back and had just bitten him. And he felt better. Not great - he was still starving and exhausted, but much better - he was no longer thirsty. He had started to sweat again, but only slightly. He felt hot, in this sun, but it was starting to get lower in the sky, and the cool stone beneath him was a relief he could notice now that he was no longer dying of thirst. "I might suggest that we take care of that methanol you now have in your system with the next request," continued the snake. "I can guess why you drank it, but I'm not sure how much you drank, or how much methanol was left in the wiper fluid. That stuff is nasty. It'll make you go blind in a day or two, if you drank enough of it." "Ummm, n-next request?" said the man. He put his hand back on his hurting shoulder and backed away from the snake a little. "That's the way it works. If you like, that is," explained the snake. "You get three requests. Call them wishes, if you wish." The snake grinned at his own joke, and the man drew back a little further from the show of fangs. "But there are rules," the snake continued. "The first request is free. The second requires an agreement of secrecy. The third requires the binding of responsibility." The snake looks at the man seriously. "By the way," the snake says suddenly, "my name is Nathan. Old Nathan, Samuel used to call me. He gave me the name. Before that, most of the Bound used to just call me 'Snake'. But that got old, and Samuel wouldn't stand for it. He said that anything that could talk needed a name. He was big into names. You can call me Nate, if you wish." Again, the snake grinned. "Sorry if I don't offer to shake, but I think you can understand - my shake sounds somewhat threatening." The snake give his rattle a little shake. "Umm, my name is Jack," said the man, trying to absorb all of this. "Jack Samson. "Can I ask you a question?" Jack says suddenly. "What happened to the poison...umm, in your bite. Why aren't I dying now? How did you do that? What do you mean by that's how you work?" "That's more than one question," grins Nate. "But I'll still try to answer all of them. First, yes, you can ask me a question." The snake's grin gets wider. "Second, the poison is in you. It changed you. You now no longer need to drink. That's what you asked for. Or, well, technically, you asked to not be thirsty any more - but 'any more' is such a vague term. I decided to make it permanent - now, as long as you live, you shouldn't need to drink much at all. Your body will conserve water very efficiently. You should be able to get enough just from the food you eat - much like a creature of the desert. You've been changed. "For the third question," Nate continues, "you are still dying. Besides the effects of that methanol in your system, you're a man - and men are mortal. In your current state, I give you no more than about another 50 years. Assuming you get out of this desert, alive, that is." Nate seemed vastly amused at his own humor, and continued his wide grin. "As for the fourth question," Nate said, looking more serious as far as Jack could tell, as Jack was just now working on his ability to read talking-snake emotions from snake facial features, "first you have to agree to make a second request and become bound by the secrecy, or I can't tell you." "Wait," joked Jack, "isn't this where you say you could tell me, but you'd have to kill me?" "I thought that was implied." Nate continued to look serious. "Ummm...yeah." Jack leaned back a little as he remembered again that he was talking to a fifteen foot poisonous reptile with a reputation for having a nasty temper. "So, what is this 'Bound by Secrecy' stuff, and can you really stop the effects of the methanol?" Jack thought for a second. "And, what do you mean methanol, anyway? I thought these days they use ethanol in wiper fluid, and just denature it?" "They may, I don't really know," said Nate. "I haven't gotten out in a while. Maybe they do. All I know is that I smell methanol on your breath and on that bottle in your pocket. And the blue color of the liquid when you pulled it out to drink some let me guess that it was wiper fluid. I assume that they still color wiper fluid blue?" "Yeah, they do," said Jack. "I figured," replied Nate. "As for being bound by secrecy - with the fulfillment of your next request, you will be bound to say nothing about me, this place, or any of the information I will tell you after that, when you decide to go back out to your kind. You won't be allowed to talk about me, write about me, use sign language, charades, or even act in a way that will lead someone to guess correctly about me. You'll be bound to secrecy. Of course, I'll also ask you to promise not to give me away, and as I'm guessing that you're a man of your word, you'll never test the binding anyway, so you won't notice." Nate said the last part with utter confidence. Jack, who had always prided himself on being a man of his word, felt a little nervous at this. "Ummm, hey, Nate, who are you? How did you know that? Are you, umm, omniscient, or something?" Well, Jack," said Nate sadly, "I can't tell you that, unless you make the second request." Nate looked away for a minute, then looked back. "Umm, well, ok," said Jack, "what is this about a second request? What can I ask for? Are you allowed to tell me that?" "Sure!" said Nate, brightening. "You're allowed to ask for changes. Changes to yourself. They're like wishes, but they can only affect you. Oh, and before you ask, I can't give you immortality. Or omniscience. Or omnipresence, for that matter. Though I might be able to make you gaseous and yet remain alive, and then you could spread through the atmosphere and sort of be omnipresent. But what good would that be - you still wouldn't be omniscient and thus still could only focus on one thing at a time. Not very useful, at least in my opinion." Nate stopped when he realized that Jack was staring at him. "Well, anyway," continued Nate, "I'd probably suggest giving you permanent good health. It would negate the methanol now in your system, you'd be immune to most poisons and diseases, and you'd tend to live a very long time, barring accident, of course. And you'll even have a tendency to recover from accidents well. It always seemed like a good choice for a request to me." "Cure the methanol poisoning, huh?" said Jack. "And keep me healthy for a long time? Hmmm. It doesn't sound bad at that. And it has to be a request about a change to me? I can't ask to be rich, right? Because that's not really a change to me?" "Right," nodded Nate. "Could I ask to be a genius and permanently healthy?" Jack asked, hopefully. "That takes two requests, Jack." "Yeah, I figured so," said Jack. "But I could ask to be a genius? I could become the smartest scientist in the world? Or the best athlete?" "Well, I could make you very smart," admitted Nate, "but that wouldn't necessarily make you the best scientist in the world. Or, I could make you very athletic, but it wouldn't necessarily make you the best athlete either. You've heard the saying that 99% of genius is hard work? Well, there's some truth to that. I can give you the talent, but I can't make you work hard. It all depends on what you decide to do with it." "Hmmm," said Jack. "Ok, I think I understand. And I get a third request, after this one?" "Maybe," said Nate, "it depends on what you decide then. There are more rules for the third request that I can only tell you about after the second request. You know how it goes." Nate looked like he'd shrug, if he had shoulders. "Ok, well, since I'd rather not be blind in a day or two, and permanent health doesn't sound bad, then consider that my second request. Officially. Do I need to sign in blood or something?" "No," said Nate. "Just hold out your hand. Or heel." Nate grinned. "Or whatever part you want me to bite. I have to bite you again. Like I said, that's how it works - the poison, you know," Nate said apologetically. Jack winced a little and felt his shoulder, where the last bite was. Hey, it didn't hurt any more. Just like Nate had said. That made Jack feel better about the biting business. But still, standing still while a fifteen foot snake sunk it's fangs into you. Jack stood up. Ignoring how good it felt to be able to stand again, and the hunger starting to gnaw at his stomach, Jack tried to decide where he wanted to get bitten. Despite knowing that it wouldn't hurt for long, Jack knew that this wasn't going to be easy. "Hey, Jack," Nate suddenly said, looking past Jack towards the dunes behind him, "is that someone else coming up over there?" Jack spun around and looked. Who else could be out here in the middle of nowhere? And did they bring food? Wait a minute, there was nobody over there. What was Nate... Jack let out a bellow as he felt two fangs sink into his rear end, through his jeans... Jack sat down carefully, favoring his more tender buttock. "I would have decided, eventually, Nate. I was just thinking about it. You didn't have to hoodwink me like that." "I've been doing this a long time, Jack," said Nate, confidently. "You humans have a hard time sitting still and letting a snake bite you - especially one my size. And besides, admit it - it's only been a couple of minutes and it already doesn't hurt any more, does it? That's because of the health benefit with this one. I told you that you'd heal quickly now." "Yeah, well, still," said Jack, "it's the principle of the thing. And nobody likes being bitten in the butt! Couldn't you have gotten my calf or something instead?" "More meat in the typical human butt," replied Nate. "And less chance you accidentally kick me or move at the last second." "Yeah, right. So, tell me all of these wonderful secrets that I now qualify to hear," answered Jack. "Ok," said Nate. "Do you want to ask questions first, or do you want me to just start talking?" "Just talk," said Jack. "I'll sit here and try to not think about food." "We could go try to rustle up some food for you first, if you like," answered Nate. "Hey! You didn't tell me you had food around here, Nate!" Jack jumped up. "What do we have? Am I in walking distance to town? Or can you magically whip up food along with your other powers?" Jack was almost shouting with excitement. His stomach had been growling for hours. "I was thinking more like I could flush something out of its hole and bite it for you, and you could skin it and eat it. Assuming you have a knife, that is," replied Nate, with the grin that Jack was starting to get used to. "Ugh," said Jack, sitting back down. "I think I'll pass. I can last a little longer before I get desperate enough to eat desert rat, or whatever else it is you find out here. And there's nothing to burn - I'd have to eat it raw. No thanks. Just talk." "Ok," replied Nate, still grinning. "But I'd better hurry, before you start looking at me as food. Nate reared back a little, looked around for a second, and then continued. "You, Jack, are sitting in the middle of the Garden of Eden." Jack looked around at the sand and dunes and then looked back at Nate sceptically. "Well, that's the best I can figure it, anyway, Jack," said Nate. "Stand up and look at the symbol on the rock here." Nate gestured around the dark stone they were both sitting on with his nose. Jack stood up and looked. Carved into the stone in a bas-relief was a representation of a large tree. The angled-pole that Nate was wrapped around was coming out of the trunk of the tree, right below where the main branches left the truck to reach out across the stone. It was very well done - it looked more like a tree had been reduced to almost two dimensions and embedded in the stone than it did like a carving. Jack walked around and looked at the details in the fading light of the setting sun. He wished he'd looked at it while the sun was higher in the sky. Wait! The sun was setting! That meant he was going to have to spend another night out here! Arrrgh! Jack looked out across the desert for a little bit, and then came back and stood next to Nate. "In all the excitement, I almost forgot, Nate," said Jack. "Which way is it back to town? And how far? I'm eventually going to have to head back - I'm not sure I'll be able to survive by eating raw desert critters for long. And even if I can, I'm not sure I'll want to." "It's about 30 miles that way." Nate pointed, with the rattle on his tail this time. As far as Jack could tell, it was a direction at right angles to the way he'd been going when he was crawling here. "But that's 30 miles by the way the crow flies. It's about 40 by the way a man walks. You should be able to do it in about half a day with your improved endurance, if you head out early tomorrow, Jack." Jack looked out the way the snake had pointed for a few seconds more, and then sat back down. It was getting dark. Not much he could do about heading out right now. And besides, Nate was just about to get to the interesting stuff. "Garden of Eden? As best as you can figure it?" "Well, yeah, as best as I and Samuel could figure it anyway," said Nate. "He figured that the story just got a little mixed up. You know, snake, in a 'tree', offering 'temptations', making bargains. That kind stuff. But he could never quite figure out how the Hebrews found out about this spot from across the ocean. He worried about that for a while." "Garden of Eden, hunh?" said Jack. "How long have you been here, Nate?" "No idea, really," replied Nate. "A long time. It never occurred to me to count years, until recently, and by then, of course, it was too late. But I do remember when this whole place was green, so I figure it's been thousands of years, at least." "So, are you the snake that tempted Eve?" said Jack. "Beats me," said Nate. "Maybe. I can't remember if the first one of your kind that I talked to was female or not, and I never got a name, but it could have been. And I suppose she could have considered my offer to grant requests a 'temptation', though I've rarely had refusals." "Well, umm, how did you get here then? And why is that white pole stuck out of the stone there?" asked Jack. "Dad left me here. Or, I assume it was my dad. It was another snake - much bigger than I was back then. I remember talking to him, but I don't remember if it was in a language, or just kind of understanding what he wanted. But one day, he brought me to this stone, told me about it, and asked me to do something for him. I talked it over with him for a while, then agreed. I've been here ever since. "What is this place?" said Jack. "And what did he ask you to do?" "Well, you see this pole here, sticking out of the stone?" Nate loosened his coils around the tilted white pole and showed Jack where it descended into the stone. The pole was tilted at about a 45 degree angle and seemed to enter the stone in an eighteen inch slot cut into the stone. Jack leaned over and looked. The slot was dark and the pole went down into it as far as Jack could see in the dim light. Jack reached out to touch the pole, but Nate was suddenly there in the way. "You can't touch that yet, Jack," said Nate. "Why not?" asked Jack. "I haven't explained it to you yet," replied Nate. "Well, it kinda looks like a lever or something," said Jack. "You'd push it that way, and it would move in the slot." "Yep, that's what it is," replied Nate. "What does it do?" asked Jack. "End the world?" "Oh, no," said Nate. "Nothing that drastic. It just ends humanity. I call it 'The Lever of Doom'." For the last few words Nate had used a deeper, ringing voice. He tried to look serious for a few seconds, and then gave up and grinned. Jack was initially startled by Nate's pronouncement, but when Nate grinned Jack laughed. "Ha! You almost had me fooled for a second there. What does it really do?" "Oh, it really ends humanity, like I said," smirked Nate. "I just thought the voice I used was funny, didn't you?" Nate continued to grin. "A lever to end humanity?" asked Jack. "What in the world is that for? Why would anyone need to end humanity?" "Well," replied Nate, "I get the idea that maybe humanity was an experiment. Or maybe the Big Guy just thought, that if humanity started going really bad, there should be a way to end it. I'm not really sure. All I know are the rules, and the guesses that Samuel and I had about why it's here. I didn't think to ask back when I started here." "Rules? What rules?" asked Jack. "The rules are that I can't tell anybody about it or let them touch it unless they agree to be bound to secrecy by a bite. And that only one human can be bound in that way at a time. That's it." explained Nate. Jack looked somewhat shocked. "You mean that I could pull the lever now? You'd let me end humanity?" "Yep," replied Nate, "if you want to." Nate looked at Jack carefully. "Do you want to, Jack?" "Umm, no." said Jack, stepping a little further back from the lever. "Why in the world would anyone want to end humanity? It'd take a psychotic to want that! Or worse, a suicidal psychotic, because it would kill him too, wouldn't it?" "Yep," replied Nate, "being as he'd be human too." "Has anyone ever seriously considered it?" asked Nate. "Any of those bound to secrecy, that is?" "Well, of course, I think they've all seriously considered it at one time or another. Being given that kind of responsibility makes you sit down and think, or so I'm told. Samuel considered it several times. He'd often get disgusted with humanity, come out here, and just hold the lever for a while. But he never pulled it. Or you wouldn't be here." Nate grinned some more. Jack sat down, well back from the lever. He looked thoughtful and puzzled at the same time. After a bit, he said, "So this makes me the Judge of humanity? I get to decide whether they keep going or just end? Me?" "That seems to be it," agreed Nate. "What kind of criteria do I use to decide?" said Jack. "How do I make this decision? Am I supposed to decide if they're good? Or too many of them are bad? Or that they're going the wrong way? Is there a set of rules for that?" "Nope," replied Nate. "You pretty much just have to decide on your own. It's up to you, however you want to decide it. I guess that you're just supposed to know." "But what if I get mad at someone? Or some girl dumps me and I feel horrible? Couldn't I make a mistake? How do I know that I won't screw up?" protested Jack. Nate gave his kind of snake-like shrug again. "You don't. You just have to try your best, Jack." Jack sat there for a while, staring off into the desert that was rapidly getting dark, chewing on a fingernail. Suddenly, Jack turned around and looked at the snake. "Nate, was Samuel the one bound to this before me?" "Yep," replied Nate. "He was a good guy. Talked to me a lot. Taught me to read and brought me books. I think I still have a good pile of them buried in the sand around here somewhere. I still miss him. He died a few months ago." "Sounds like a good guy," agreed Jack. "How did he handle this, when you first told him. What did he do?" "Well," said Nate, "he sat down for a while, thought about it for a bit, and then asked me some questions, much like you're doing." "What did he ask you, if you're allowed to tell me?" asked Jack. "He asked me about the third request," replied Nate. "Aha!" It was Jack's turn to grin. "And what did you tell him?" "I told him the rules for the third request. That to get the third request you have to agree to this whole thing. That if it ever comes to the point that you really think that humanity should be ended, that you'll come here and end it. You won't avoid it, and you won't wimp out." Nate looked serious again. "And you'll be bound to do it too, Jack." "Hmmm." Jack looked back out into the darkness for a while. Nate watched him, waiting. "Nate," continued Jack, quietly, eventually. "What did Samuel ask for with his third request?" Nate sounded like he was grinning again as he replied, also quietly, "Wisdom, Jack. He asked for wisdom. As much as I could give him." "Ok," said Jack, suddenly, standing up and facing away from Nate, "give it to me. Nate looked at Jack's backside. "Give you what, Jack?" "Give me that wisdom. The same stuff that Samuel asked for. If it helped him, maybe it'll help me too." Jack turned his head to look back over his shoulder at Nate. "It did help him, right?" "He said it did," replied Nate. "But he seemed a little quieter afterward. Like he had a lot to think about." "Well, yeah, I can see that," said Jack. "So, give it to me." Jack turned to face away from Nate again, bent over slightly and tensed up. Nate watched Jack tense up with a little exasperation. If he bit Jack now, Jack would likely jump out of his skin and maybe hurt them both. "You remember that you'll be bound to destroy humanity if it ever looks like it needs it, right Jack?" asked Nate, shifting position. "Yeah, yeah, I got that," replied Jack, eyes squeezed tightly shut and body tense, not noticing the change in direction of Nate's voice. "And," continued Nate, from his new position, "do you remember that you'll turn bright purple, and grow big horns and extra eyes?" "Yeah, yeah...Hey, wait a minute!" said Jack, opening his eyes, straightening up and turning around. "Purple?!" He didn't see Nate there. With the moonlight Jack could see that the lever extended up from its slot in the rock without the snake wrapped around it. Jack heard, from behind him, Nate's "Just Kidding!" right before he felt the now familiar piercing pain, this time in the other buttock. Jack sat on the edge of the dark stone in the rapidly cooling air, his feet extending out into the sand. He stared out into the darkness, listening to the wind stir the sand, occasionally rubbing his butt where he'd been recently bitten. Nate had left for a little while, had come back with a desert-rodent-shaped bulge somewhere in his middle, and was now wrapped back around the lever, his tongue flicking out into the desert night's air the only sign that he was still awake. Occasionally Jack, with his toes absentmindedly digging in the sand while he thought, would ask Nate a question without turning around. "Nate, do accidents count?" Nate lifted his head a little bit. "What do you mean, Jack?" Jack tilted his head back like he was looking at the stars. "You know, accidents. If I accidentally fall on the lever, without meaning to, does that still wipe out humanity?" "Yeah, I'm pretty sure it does, Jack. I'd suggest you be careful about that if you start feeling wobbly," said Nate with some amusement. A little later - "Does it have to be me that pulls the lever?" asked Jack. "That's the rule, Jack. Nobody else can pull it," answered Nate. "No," Jack shook his head, "I meant does it have to be my hand? Could I pull the lever with a rope tied around it? Or push it with a stick? Or throw a rock?" "Yes, those should work," replied Nate. "Though I'm not sure how complicated you could get. Samuel thought about trying to build some kind of remote control for it once, but gave it up. Everything he'd build would be gone by the next sunrise, if it was touching the stone, or over it. I told him that in the past others that had been bound had tried to bury the lever so they wouldn't be tempted to pull it, but every time the stones or sand or whatever had disappeared." "Wow," said Jack, "Cool." Jack leaned back until only his elbows kept him off of the stone and looked up into the sky. "Nate, how long did Samuel live? One of his wishes was for health too, right?" asked Jack. "Yes," replied Nate, "it was. He lived 167 years, Jack." "Wow, 167 years. That's almost 140 more years I'll live if I live as long. Do you know what he died of, Nate?" "He died of getting tired of living, Jack," Nate said, sounding somewhat sad. Jack turned his head to look at Nate in the starlight. Nate looked back. "Samuel knew he wasn't going to be able to stay in society. He figured that they'd eventually see him still alive and start questioning it, so he decided that he'd have to disappear after a while. He faked his death once, but changed his mind - he decided it was too early and he could stay for a little longer. He wasn't very fond of mankind, but he liked the attention. Most of the time, anyway. "His daughter and then his wife dying almost did him in though. He didn't stay in society much longer after that. He eventually came out here to spend time talking to me and thinking about pulling the lever. A few months ago he told me he'd had enough. It was his time." "And then he just died?" asked Jack. Nate shook his head a little. "He made his forth request, Jack. There's only one thing you can ask for the fourth request. The last bite. After a bit Nate continued, "He told me that he was tired, that it was his time. He reassured me that someone new would show up soon, like they always had. After another pause, Nate finished, "Samuel's body disappeared off the stone with the sunrise." Jack lay back down and looked at the sky, leaving Nate alone with his memories. It was a long time until Jack's breathing evened out into sleep. Jack woke with the sunrise the next morning. He was a little chilled with the morning desert air, but overall was feeling pretty good. Well, except that his stomach was grumbling and he wasn't willing to eat raw desert rat. So, after getting directions to town from Nate, making sure he knew how to get back, and reassuring Nate that he'd be back soon, Jack started the long walk back to town. With his new health and Nate's good directions, he made it back easily. Jack caught a bus back to the city, and showed up for work the next day, little worse for the wear and with a story about getting lost in the desert and walking back out. Within a couple of days Jack had talked a friend with a tow truck into going back out into the desert with him to fetch the SUV. They found it after a couple of hours of searching and towed it back without incident. Jack was careful not to even look in the direction of Nate's lever, though their path back didn't come within sight of it. Before the next weekend, Jack had gone to a couple of stores, including a book store, and had gotten his SUV back from the mechanic, with a warning to avoid any more joyriding in the desert. On Saturday, Jack headed back to see Nate. Jack parked a little way out of the small town near Nate, loaded up his new backpack with camping gear and the things he was bringing for Nate, and then started walking. He figured that walking would leave the least trail, and he knew that while not many people camped in the desert, it wasn't unheard of, and shouldn't really raise suspicions. Jack had brought more books for Nate - recent books, magazines, newspapers. Some things that would catch Nate up with what was happening in the world, others that were just good books to read. He spent the weekend with Nate, and then headed out again, telling Nate that he'd be back again soon, but that he had things to do first. Over four months later Jack was back to see Nate again. This time he brought a laptop with him - a specially modified laptop. It had a solar recharger, special filters and seals to keep out the sand, a satellite link-up, and a special keyboard and joystick that Jack hoped that a fifteen-foot rattlesnake would be able to use. And, it had been hacked to not give out its location to the satellite. After that Jack could e-mail Nate to keep in touch, but still visited him fairly regularly - at least once or twice a year. After the first year, Jack quit his job. For some reason, with the wisdom he 'd been given, and the knowledge that he could live for over 150 years, working in a nine to five job for someone else didn't seem that worthwhile any more. Jack went back to school. Eventually, Jack started writing. Perhaps because of the wisdom, or perhaps because of his new perspective, he wrote well. People liked what he wrote, and he became well known for it. After a time, Jack bought an RV and started traveling around the country for book signings and readings. But, he still remembered to drop by and visit Nate occasionally. On one of the visits Nate seemed quieter than usual. Not that Nate had been a fountain of joy lately. Jack's best guess was that Nate was still missing Samuel, and though Jack had tried, he still hadn't been able to replace Samuel in Nate's eyes. Nate had been getting quieter each visit. But on this visit Nate didn't even speak when Jack walked up to the lever. He nodded at Jack, and then went back to staring into the desert. Jack, respecting Nate's silence, sat down and waited. After a few minutes, Nate spoke. "Jack, I have someone to introduce you to." Jack looked surprised. "Someone to introduce me to?" Jack looked around, and then looked carefully back at Nate. "This something to do with the Big Guy? "No, no," replied Nate. "This is more personal. I want you to meet my son." Nate looked over at the nearest sand dune. "Sammy!" Jack watched as a four foot long desert rattlesnake crawled from behind the dune and up to the stone base of the lever. "Yo, Jack," said the new, much smaller snake. "Yo, Sammy" replied Jack. Jack looked at Nate. "Named after Samuel, I assume?" Nate nodded. "Jack, I've got a favor to ask you. Could you show Sammy around for me?" Nate unwrapped himself from the lever and slithered over to the edge of the stone and looked across the sands. "When Samuel first told me about the world, and brought me books and pictures, I wished that I could go see it. I wanted to see the great forests, the canyons, the cities, even the other deserts, to see if they felt and smelled the same. I want my son to have that chance - to see the world. Before he becomes bound here like I have been. "He's seen it in pictures, over the computer that you brought me. But I hear that it's not the same. That being there is different. I want him to have that. Think you can do that for me, Jack?" Jack nodded. This was obviously very important to Nate, so Jack didn't even joke about taking a talking rattlesnake out to see the world. "Yeah, I can do that for you, Nate. Is that all you need?" Jack could sense that was something more. Nate looked at Sammy. Sammy looked back at Nate for a second and then said, "Oh, yeah. Ummm, I've gotta go pack. Back in a little bit Jack. Nice to meet ya!" Sammy slithered back over the dune and out of sight. Nate watched Sammy disappear and then looked back at Jack. "Jack, this is my first son. My first offspring through all the years. You don't even want to know what it took for me to find a mate." Nate grinned to himself. "But anyway, I had a son for a reason. I'm tired. I'm ready for it to be over. I needed a replacement." Jack considered this for a minute. "So, you're ready to come see the world, and you wanted him to watch the lever while you were gone?" Nate shook his head. "no, Jack - you're a better guesser than that. You've already figured out - I'm bound here - there's only one way for me to leave here. And I'm ready. It's my time to die." Jack looked more closely at Nate. He could tell Nate had thought about this - probably for quite a while. Jack had trouble imagining what it would be like to be as old as Nate, but Jack could already tell that in another hundred or two hundred years, he might be getting tired of life himself. Jack could understand Samuel's decision, and now Nate's. So, all Jack said was, "What do you want me to do?" Nate nodded. "Thanks, Jack. I only want two things. One - show Sammy around the world - let him get his fill of it, until he's ready to come back here and take over. Two - give me the fourth request. "I can't just decide to die, not any more than you can. I won't even die of old age like you eventually will, even though it'll be a long time from now. I need to be killed. Once Sammy is back here, ready to take over, I'll be able to die. And I need you to kill me. "I've even thought about how. Poisons and other drugs won't work on me. And I've seen pictures of snakes that were shot - some of them live for days, so that's out too. So, I want you to bring back a sword. Nate turned away to look back to the dune that Sammy had gone behind. "I'd say an axe, but that's somewhat undignified - putting my head on the ground or a chopping block like that. No, I like a sword. A time-honored way of going out. A dignified way to die. And, most importantly, it should work, even on me. "You willing to do that for me, Jack?" Nate turned back to look at Jack. "Yeah, Nate," replied Jack solemnly, "I think I can handle that." Nate nodded. "Good!" He turned back toward the dune and shouted, "Sammy! Jack's about ready to leave!" Then quietly, "Thanks, Jack." Jack didn't have anything to say to that, so he waited for Sammy to make it back to the lever, nodded to him, nodded a final time to Nate, and then headed into the desert with Sammy following. Over the next several years Sammy and Jack kept in touch with Nate through e-mail as they went about their adventures. They made a goal of visiting every country in the world, and did a respectable job of it. Sammy had a natural gift for languages, as Jack expected he would, and even ended up acting as a translator for Jack in a few of the countries. Jack managed to keep the talking rattlesnake hidden, even so, and by the time they were nearing the end of their tour of countries, Sammy had only been spotted a few times. While there were several people that had seen enough to startle them greatly, nobody had enough evidence to prove anything, and while a few wild rumors and storied followed Jack and Sammy around, nothing ever hit the newspapers or the public in general. When they finished the tour of countries, Jack suggested that they try some undersea diving. They did. And spelunking. They did that too. Sammy finally drew the line at visiting Antarctica. He'd come to realize that Jack was stalling. After talking to his Dad about it over e-mail, he figured out that Jack probably didn't want to have to kill Nate. Nate told Sammy that humans could be squeamish about killing friends and acquaintances. So, Sammy eventually put his tail down (as he didn't have a foot) and told Jack that it was time - he was ready to go back and take up his duties from his dad. Jack, delayed it a little more by insisting that they go back to Japan and buy an appropriate sword. He even stretched it a little more by getting lessons in how to use the sword. But, eventually, he'd learned as much as he was likely to without dedicating his life to it, and was definitely competent enough to take the head off of a snake. It was time to head back and see Nate. When they got back to the US, Jack got the old RV out of storage where he and Sammy had left it after their tour of the fifty states, he loaded up Sammy and the sword, and they headed for the desert. When they got to the small town that Jack had been trying to find those years ago when he'd met Nate, Jack was in a funk. He didn't really feel like walking all of the way out there. Not only that, but he'd forgotten to figure the travel time correctly, and it was late afternoon. They'd either have to spend the night in town and walk out tomorrow, or walk in the dark. As Jack was afraid that if he waited one more night he might lose his resolve, he decided that he'd go ahead and drive the RV out there. It was only going to be this once, and Jack would go back and cover the tracks afterward. They ought to be able to make it out there by nightfall if they drove, and then they could get it over tonight. Jack told Sammy to e-mail Nate that they were coming as he drove out of sight of the town on the road. They then pulled off the road and headed out into the desert. Everything went well, until they got to the sand dunes. Jack had been nursing the RV along the whole time, over the rocks, through the creek beds, revving the engine the few times they almost got stuck. When they came to the dunes, Jack didn't really think about it, he just downshifted and headed up the first one. By the third dune, Jack started to regret that he'd decided to try driving on the sand. The RV was fishtailling and losing traction. Jack was having to work it up each dune slowly and was trying to keep from losing control each time they came over the top and slid down the other side. Sammy had come up to sit in the passenger seat, coiled up and laughing at Jack's driving. As they came over the top of the fourth dune, the biggest one yet, Jack saw that this was the final dune - the stone, the lever, and somewhere Nate, waited below. Jack put on the brakes, but he'd gone a little too far. The RV started slipping down the other side. Jack tried turning the wheel, but he didn't have enough traction. He pumped the brakes - no response. They started sliding down the hill, faster and faster. Jack felt a shock go through him as he suddenly realized that they were heading for the lever. He looked down - the RV was directly on course for it. If Jack didn't do something, the RV would hit it. He was about to end humanity. Jack steered more frantically, trying to get traction. It still wasn't working. The dune was too steep, and the sand too loose. In a split second, Jack realized that his only chance would be once he hit the stone around the lever - he should have traction on the stone for just a second before he hit the lever - he wouldn't have time to stop, but he should be able to steer away. Jack took a better grip on the steering wheel and tried to turn the RV a little bit - every little bit would help. He'd have to time his turn just right. The RV got to the bottom of the dune, sliding at an amazing speed in the sand. Just before they reached the stone Jack looked across it to check that they were still heading for the lever. They were. But Jack noticed something else that he hadn't seen from the top of the dune. Nate wasn't wrapped around the lever. He was off to the side of the lever, but still on the stone, waiting for them. The problem was, he was waiting on the same side of the lever that Jack had picked to steer towards to avoid the lever. The RV was already starting to drift that way a little in its mad rush across the sand and there was no way that Jack was going to be able to go around the lever to the other side. Jack had an instant of realization. He was either going to have to hit the lever, or run over Nate. He glanced over at Sammy and saw that Sammy realized the same thing. Jack took a firmer grip on the steering wheel as the RV ran up on the stone. Shouting to Sammy as he pulled the steering wheel, "BETTER NATE THAN LEVER," he ran over the snake.

. . I am a whale

OK, Billy went to his friend Fred in the tree. And then went inside to get a snack. Then Fred fell out of the Tree and.....landed on a comfy mattress.

What can fit between breasts? Is long? And gets hard when you jerk it? A seatbelt.

Why did Hitler Kill his self Answer- He got a gas bill By Lewis

How many hours of sleep did Jimmy get last night? Zero, because he has insomnia. Jimmy got fired from his job today because of his lack of energy and motivation due to his disorder. His wife divorced Jimmy because he can no longer support her and their two kids.

How do you make a sandwich out of clay? Shape it like a sandwich

If i was gay... I would have strong sexual feelings towards peolple of the same sex as me

Knock! Knock! Who's there? Russel. Russell who? Russell Johnson. Oh, come in.

A stripper walks into a bar. She works there.

BEST PLACE IN THE WORLD COPENHAGEN !!!!!!!!!!!!!!!!

Why did the plane crash? Because the pilot was a tomato.

What goes from pink to red in 5 seconds? A pink shirt when red pain is spilled on it.

Why am I telling you this joke? Because I entered the following, agreed to the Terms of Service, and clicked "submit".

A Jew walks into a bar. He immediately turns around and walks out because prices at this particular high end bar are much too high for his liking.

What did the shark say to the boat captain? So do you prefer cards or pool?

Why can't Anne Frank write a sequel? Because she's dead.

Human: Are you a frayed knot? Frayed knot: I'm afraid so.

A blonde fails an exam because she did not study

What do you call someone who's sad? A depressed person

women are like puzzles because prior to 1920 neither had the right to vote, puzzles still don't.

Why was six afraid of seven? Because six cheated on seven and slept with nine.

Knock, Knock. Who's there? Ron Sparks.

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