The Moon (Latin: Luna) is Earth's only natural satellite and the fifth largest satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,403 km, about thirty times the diameter of the Earth. The common centre of mass of the system (the barycentre) is located about 1,700 km—a quarter the Earth's radius—beneath the surface of the Earth. The Moon makes a complete orbit around the Earth every 27.3 days (the orbital period), and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days (the synodic period).
The Moon's diameter is 3,474 km,[6] a little more than a quarter of that of the Earth. Thus, the Moon's surface area is less than a tenth that of the Earth (about a quarter the Earth's land area, approximately as large as Russia, Canada, and the United States combined), and its volume is about 2 percent that of Earth. The pull of gravity at its surface is about 17 percent of that at the Earth's surface.
The Moon is the only celestial body to which humans have traveled and upon which humans have performed a manned landing. The first artificial object to pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966.[6] The United States (U.S.) Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although a few robotic landers and orbiters have been sent to the Moon since that time. Several countries have announced plans to return humans to the surface of the Moon in the 2020s.
Name and etymology
The proper English name for Earth's natural satellite is, simply, the Moon (capitalized).[7][8] Moon is a Germanic word, related to the Latin mensis (month). It is ultimately a derivative of the Proto-Indo-European root me-, also represented in measure[9] (time), with reminders of its importance in measuring time in words derived from it like Monday, month and menstrual. The related adjective is lunar, as well as an adjectival prefix seleno- and suffix -selene (from selēnē, the Ancient Greek word for the Moon). In English, the word moon exclusively meant "the Moon" until 1665, when it was extended to refer to the recently-discovered natural satellites of other planets.[9] Subsequently, these objects were given distinct names in order to avoid confusion.[8] The Moon is occasionally referred to by its Latin name Luna, primarily in science fiction.
Lunar surface
Main article: Geology of the Moon
Two sides of the Moon
The Moon is in synchronous rotation, which means it rotates about its axis in about the same time it takes to orbit the Earth. This results in it keeping nearly the same face turned towards the Earth at all times. The Moon used to rotate at a faster rate, but early in its history, its rotation slowed and became locked in this orientation as a result of frictional effects associated with tidal deformations caused by the Earth.[10]
Small variations (libration) in the angle from which the Moon is seen allow about 59% of its surface to be seen from the Earth (but only half at any instant).[6]
Near side of the Moon Far side of the Moon
The side of the Moon that faces Earth is called the near side, and the opposite side the far side. The far side is often inaccurately called the "dark side," but in fact, it is illuminated exactly as often as the near side: once per lunar day, during the new moon phase we observe on Earth when the near side is dark. The far side of the Moon was first photographed by the Soviet probe Luna 3 in 1959. One distinguishing feature of the far side is its almost complete lack of maria.
Lunar libration
Maria
Main article: Lunar mare
The dark and relatively featureless lunar plains which can clearly be seen with the naked eye are called maria (singular mare), Latin for seas, since they were believed by ancient astronomers to be filled with water. These are now known to be vast solidified pools of ancient basaltic lava. The majority of these lavas erupted or flowed into the depressions associated with impact basins that formed by the collisions of meteors and comets with the lunar surface. (Oceanus Procellarum is a major exception in that it does not correspond to a known impact basin). Maria are found almost exclusively on the near side of the Moon, with the far side having only a few scattered patches covering about 2% of its surface,[11] compared with about 31% on the near side.[6] The most likely explanation for this difference is related to a higher concentration of heat-producing elements on the near-side hemisphere, as has been demonstrated by geochemical maps obtained from the Lunar Prospector gamma-ray spectrometer.[12][13] Several provinces containing shield volcanoes and volcanic domes are found within the near side maria.[14]
Terrae
The lighter-colored regions of the Moon are called terrae, or more commonly just highlands, since they are higher than most maria. Several prominent mountain ranges on the near side are found along the periphery of the giant impact basins, many of which have been filled by mare basalt. These are believed to be the surviving remnants of the impact basin's outer rims.[15] In contrast to the Earth, no major lunar mountains are believed to have formed as a result of tectonic events.[16]
From images taken by the Clementine mission in 1994, it appears that four mountainous regions on the rim of the 73 km-wide Peary crater at the Moon's north pole remain illuminated for the entire lunar day. These peaks of eternal light are possible because of the Moon's extremely small axial tilt to the ecliptic plane. No similar regions of eternal light were found at the south pole, although the rim of Shackleton crater is illuminated for about 80% of the lunar day. Another consequence of the Moon's small axial tilt is regions that remain in permanent shadow at the bottoms of many polar craters.[17]
Impact craters
Lunar crater Daedalus on the Moon's far sideThe Moon's surface is marked by impact craters[18] which form when asteroids and comets collide with the lunar surface. There are about half a million craters with diameters greater than 1 km on the moon. Since impact craters accumulate at a nearly constant rate, the number of craters per unit area superposed on a geologic unit can be used to estimate the age of the surface (see crater counting). The lack of an atmosphere, weather and recent geological processes ensures that many of these craters have remained relatively well preserved in comparison to those on Earth.
The largest crater on the Moon, which also has the distinction of being one of the largest known craters in the Solar System,[19] is the South Pole-Aitken basin. It is on the far side, between the South Pole and equator, and is some 2,240 km in diameter and 13 km in depth.[20] Prominent impact basins on the near side include Imbrium, Serenitatis, Crisium, and Nectaris.
Regolith
Blanketed atop the Moon's crust is a highly comminuted (broken into ever smaller particles) and "impact gardened" surface layer called regolith. Since the regolith forms by impact processes, the regolith of older surfaces is generally thicker than for younger surfaces. In particular, it has been estimated that the regolith varies in thickness from about 3–5 m in the maria, and by about 10–20 m in the highlands.[21] Beneath the finely comminuted regolith layer is what is generally referred to as the megaregolith. This layer is much thicker (on the order of tens of kilometres) and comprises highly fractured bedrock.[22]
Presence of water
Main article: Lunar ice
The continuous bombardment of the Moon by comets and meteoroids has most likely added small amounts of water to the lunar surface. If so, sunlight would split much of this water into its constituent elements of hydrogen and oxygen, both of which would ordinarily escape into space over time, because of the Moon's weak gravity. However, because of the slightness of the axial tilt of the Moon's spin axis to the ecliptic plane—only 1.5°—some deep craters near the poles never receive direct light from the Sun and are thus in permanent shadow (see Shackleton crater). Water molecules that ended up in these craters could be stable for long periods of time.
Clementine has mapped craters at the lunar south pole[23] that are shadowed in this way, and computer simulations suggest that up to 14,000 km² might be in permanent shadow.[17] Results from the Clementine mission bistatic radar experiment are consistent with small, frozen pockets of water close to the surface, and data from the Lunar Prospector neutron spectrometer indicate that anomalously high concentrations of hydrogen are present in the upper metre of the regolith near the polar regions.[24] Estimates for the total quantity of water ice are close to one cubic kilometre.
Water ice can be mined and then split into its constituent hydrogen and oxygen atoms by means of nuclear generators or electric power stations equipped with solar panels. The presence of usable quantities of water on the Moon is an important factor in rendering lunar habitation cost-effective, since transporting water from Earth would be prohibitively expensive. However, recent observations made with the Arecibo planetary radar suggest that some of the near-polar Clementine radar data that were previously interpreted as being indicative of water ice might instead be a result of rocks ejected from young impact craters.[25] The question of how much water there is on the Moon has not been resolved.
In July 2008, small amounts of water were found in the interior of volcanic pearls from the Moon (brought to Earth by Apollo 15).[26]
Physical characteristics
Internal structure
Main article: Internal structure of the Moon
Schematic illustration of the internal structure of the MoonThe Moon is a differentiated body, being composed of a geochemically distinct crust, mantle, and core. This structure is believed to have resulted from the fractional crystallization of a magma ocean shortly after its formation, at about 4.4 billion years ago[27]. The energy required to melt the outer portion of the Moon is commonly attributed to a giant impact event that is postulated to have formed the Earth-Moon system, and the subsequent reaccretion of material in Earth orbit. Crystallization of this magma ocean would have given rise to a mafic mantle and a plagioclase-rich crust (see Origin and geologic evolution below).
Geochemical mapping from orbit implies that the crust of the Moon is largely anorthositic in composition,[28] consistent with the magma ocean hypothesis. In terms of elements, the crust is composed primarily of oxygen, silicon, magnesium, iron, calcium, and aluminium. Based on geophysical techniques, its thickness is estimated to be on average about 50 km.[1]
Partial melting within the mantle of the Moon gave rise to the eruption of mare basalts on the lunar surface. Analyses of these basalts indicate that the mantle is composed predominantly of the minerals olivine, orthopyroxene and clinopyroxene, and that the lunar mantle is more iron rich than that of the Earth. Some lunar basalts contain high abundances of titanium (present in the mineral ilmenite), suggesting that the mantle is highly heterogeneous in composition. Moonquakes have been found to occur deep within the mantle of the Moon about a thousand kilometres below the surface. These occur with monthly periodicities and are related to tidal stresses caused by the eccentric orbit of the Moon about the Earth.[1]
The Moon has a mean density of 3 346.4 kg/m³, making it the second densest moon in the Solar System after Io. Nevertheless, several lines of evidence imply that the core of the Moon is small, with a radius of about 350 km or less.[1] This corresponds to only about 20% the size of the Moon, in contrast to about 50% as is the case for most other terrestrial bodies. The composition of the lunar core is not well constrained, but most believe that it is composed of metallic iron alloyed with a small amount of sulfur and nickel. Analyses of the Moon's time-variable rotation indicate that the core is at least partly molten.[29]
Topography
Main article: Topography of the Moon
Topography of the Moon, referenced to the lunar geoidThe topography of the Moon has been measured by the methods of laser altimetry and stereo image analysis, most recently from data obtained during the Clementine mission. The most visible topographic feature is the giant far side South Pole-Aitken basin, which possesses the lowest elevations of the Moon. The highest elevations are found just to the north-east of this basin, and it has been suggested that this area might represent thick ejecta deposits that were emplaced during an oblique South Pole-Aitken basin impact event. Other large impact basins, such as Imbrium, Serenitatis, Crisium, Smythii, and Orientale, also possess regionally low elevations and elevated rims. Another distinguishing feature of the Moon's shape is that the elevations are on average about 1.9 km higher on the far side than the near side.[1]
Gravity field
Main article: Gravity of the Moon
The gravitational field of the Moon has been determined through tracking of radio signals emitted by orbiting spacecraft. The principle used depends on the Doppler effect, whereby the spacecraft acceleration in the line-of-sight direction can be determined by means of small shifts in frequency of the radio signal, and the distance from the spacecraft to a station on Earth. However, because of the Moon's synchronous rotation it is not possible to track spacecraft much over the limbs of the Moon, and the farside gravity field is thus only poorly characterised.[30]
Radial gravitational anomaly at the surface of the MoonThe major characteristic of the Moon's gravitational field is the presence of mascons, which are large positive gravitational anomalies associated with some of the giant impact basins.[31] These anomalies greatly influence the orbit of spacecraft about the Moon, and an accurate gravitational model is necessary in the planning of both manned and unmanned missions. The mascons are in part due to the presence of dense mare basaltic lava flows that fill some of the impact basins. However, lava flows by themselves can not explain the entirety of the gravitational signature, and uplift of the crust-mantle interface is required as well. Based on Lunar Prospector gravitational models, it has been suggested that some mascons exist that do not show evidence for mare basaltic volcanism.[32] The huge expanse of mare basaltic volcanism associated with Oceanus Procellarum does not possess a positive gravitational anomaly.
Magnetic field
Main article: Magnetic field of the Moon
Total magnetic field strength at the surface of the Moon as derived from the Lunar Prospector electron reflectometer experimentThe Moon has an external magnetic field of the order of one to a hundred nanotesla—less than one hundredth that of the Earth, which is 30–60 microtesla. Other major differences are that the Moon does not currently have a dipolar magnetic field (as would be generated by a geodynamo in its core), and the magnetizations that are present are almost entirely crustal in origin.[33] One hypothesis holds that the crustal magnetizations were acquired early in lunar history when a geodynamo was still operating. The small size of the lunar core, however, is a potential obstacle to this theory. Alternatively, it is possible that on an airless body such as the Moon, transient magnetic fields could be generated during large impact events. In support of this, it has been noted that the largest crustal magnetizations appear to be located near the antipodes of the giant impact basins. It has been proposed that such a phenomenon could result from the free expansion of an impact generated plasma cloud around the Moon in the presence of an ambient magnetic field.[34]
Atmosphere
Main article: Atmosphere of the Moon
The Moon has an atmosphere so thin as to be almost negligible, with a total atmospheric mass of less than 104 kg.[35] The effective surface pressure of this small mass is around 3 × 10-15 atm [36]. This pressure varies, of course, with the diurnal moon cycle. One source of its atmosphere is outgassing—the release of gases such as radon that originate by radioactive decay processes within the crust and mantle.[citation needed] Another important source is generated through the process of sputtering, which involves the bombardment of micrometeorites, solar wind ions, electrons, and sunlight.[28] Gases that are released by sputtering can either reimplant into the regolith as a result of the Moon's gravity, or can be lost to space either by solar radiation pressure or by being swept away by the solar wind magnetic field if they are ionised. The elements sodium (Na) and potassium (K) have been detected using earth-based spectroscopic methods, whereas the element radon–222 (222Rn) and polonium-210 (210Po) have been inferred from data obtained from the Lunar Prospector alpha particle spectrometer.[37] Argon–40 (40Ar), helium-4 (4He), oxygen (O2) and/or methane (CH4), nitrogen (N2) and/or carbon monoxide (CO), and carbon dioxide (CO2) were detected by in-situ detectors placed by the Apollo astronauts.[38]
Surface temperature
During the lunar day, the surface temperature averages 107°C, and during the lunar night, it averages -153°C.[39]
Origin and geologic evolution
Formation
Several mechanisms have been suggested for the Moon's formation. The formation of the Moon is believed to have occurred 4.527 ± 0.010 billion years ago, about 30–50 million years after the origin of the Solar System.[40]
Fission hypothesis
Early speculation proposed that the Moon broke off from the Earth's crust because of centrifugal forces, leaving a basin – presumed to be the Pacific Ocean – behind as a scar.[41] This idea, however, would require too great an initial spin of the Earth; and, even had this been possible, the process should have resulted in the Moon's orbit following Earth's equatorial plane. This is not the case.
Capture hypothesis
Other speculation has centered on the Moon being formed elsewhere and subsequently being captured by Earth's gravity.[42] However, the conditions believed necessary for such a mechanism to work, such as an extended atmosphere of the Earth in order to dissipate the energy of the passing Moon, are improbable.
Co-formation hypothesis
The co-formation hypothesis proposes that the Earth and the Moon formed together at the same time and place from the primordial accretion disk. The Moon would have formed from material surrounding the proto-Earth, similar to the formation of the planets around the Sun. Some suggest that this hypothesis fails to adequately explain the depletion of metallic iron in the Moon.
A major deficiency in all these hypotheses is that they cannot readily account for the high angular momentum of the Earth–Moon system.[43]
Giant Impact hypothesis
Main article: Giant impact hypothesis
The prevailing hypothesis today is that the Earth–Moon system formed as a result of a giant impact. A Mars-sized body (labelled "Theia") is believed to have hit the proto-Earth, blasting sufficient material into orbit around the proto-Earth to form the Moon through accretion.[6] As accretion is the process by which all planetary bodies are believed to have formed, giant impacts are thought to have affected most if not all planets. Computer simulations modelling a giant impact are consistent with measurements of the angular momentum of the Earth–Moon system, as well as the small size of the lunar core.[44] Unresolved questions regarding this theory concern the determination of the relative sizes of the proto-Earth and Theia and of how much material from these two bodies formed the Moon.
Lunar magma ocean
As a result of the large amount of energy liberated during both the giant impact event and the subsequent reaccretion of material in Earth orbit, it is commonly believed that a large portion of the Moon was once initially molten. The molten outer portion of the Moon at this time is referred to as a magma ocean, and estimates for its depth range from about 500 km to the entire radius of the Moon.[12]
As the magma ocean cooled, it fractionally crystallised and differentiated, giving rise to a geochemically distinct crust and mantle. The mantle is inferred to have formed largely by the precipitation and sinking of the minerals olivine, clinopyroxene, and orthopyroxene. After about three-quarters of magma ocean crystallisation was complete, the mineral anorthite is inferred to have precipitated and floated to the surface because of its low density, forming the crust.[12]
The final liquids to crystallise from the magma ocean would have been initially sandwiched between the crust and mantle, and would have contained a high abundance of incompatible and heat-producing elements. This geochemical component is referred to by the acronym KREEP, for potassium (K), rare earth elements (REE), and phosphorus (P), and appears to be concentrated within the Procellarum KREEP Terrane, which is a small geologic province that encompasses most of Oceanus Procellarum and Mare Imbrium on the near side of the Moon.[1]
Geologic evolution
See also: Geology of the Moon
A large portion of the Moon's post–magma-ocean geologic evolution was dominated by impact cratering. The lunar geologic timescale is largely divided in time on the basis of prominent basin-forming impact events, such as Nectaris, Imbrium, and Orientale. These impact structures are characterised by multiple rings of uplifted material, and are typically hundreds to thousands of kilometres in diameter. Each multi-ring basin is associated with a broad apron of ejecta deposits that forms a regional stratigraphic horizon. While only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages on the basis of stratigraphic grounds. The continuous effects of impact cratering are responsible for forming the regolith.
The other major geologic process that affected the Moon's surface was mare volcanism. The enhancement of heat-producing elements within the Procellarum KREEP Terrane is thought to have caused the underlying mantle to heat up, and eventually, to partially melt. A portion of these magmas rose to the surface and erupted, accounting for the high concentration of mare basalts on the near side of the Moon.[12] Most of the Moon's mare basalts erupted during the Imbrian period in this geologic province 3.0–3.5 billion years ago. Nevertheless, some dated samples are as old as 4.2 billion years,[45] and the youngest eruptions, based on the method of crater counting, are believed to have occurred only 1.2 billion years ago.[46]
There has been controversy over whether features on the Moon's surface undergo changes over time. Some observers have claimed that craters either appeared or disappeared, or that other forms of transient phenomena had occurred. Today, many of these claims are thought to be illusory, resulting from observation under different lighting conditions, poor astronomical seeing, or the inadequacy of earlier drawings. Nevertheless, it is known that the phenomenon of outgassing does occasionally occur, and these events could be responsible for a minor percentage of the reported lunar transient phenomena. Recently, it has been suggested that a roughly 3 km diameter region of the lunar surface was modified by a gas release event about a million years ago.[47][48]
Moon rocks
Main article: Moon rocks
Moon rocks fall into two main categories, based on whether they underlie the lunar highlands (terrae) or the maria. The lunar highlands rocks are composed of three suites: the ferroan anorthosite suite, the magnesian suite, and the alkali suite (some consider the alkali suite to be a subset of the mg-suite). The ferroan anorthosite suite rocks are composed almost exclusively of the mineral anorthite (a calic plagioclase feldspar), and are believed to represent plagioclase flotation cumulates of the lunar magma ocean. The ferroan anorthosites have been dated using radiometric methods to have formed about 4.4 billion years ago.[45][46]
The mg- and alkali-suite rocks are predominantly mafic plutonic rocks. Typical rocks are dunites, troctolites, gabbros, alkali anorthosites, and more rarely, granite. In contrast to the ferroan anorthosite suite, these rocks all have relatively high Mg/Fe ratios in their mafic minerals. In general, these rocks represent intrusions into the already-formed highlands crust (though a few rare samples appear to represent extrusive lavas), and they have been dated to have formed about 4.4–3.9 billion years ago. Many of these rocks have high abundances of, or are genetically related to, the geochemical component KREEP.
The lunar maria consist entirely of mare basalts. While similar to terrestrial basalts, they have much higher abundances of iron, are completely lacking in hydrous alteration products, and have a large range of titanium abundances.[49][50]
Astronauts have reported that the dust from the surface felt like snow and smelled like spent gunpowder.[51] The dust is mostly made of silicon dioxide glass (SiO2), most likely created from the meteors that have crashed into the Moon's surface. It also contains calcium and magnesium.
Orbit and relationship to Earth
Main articles: Orbit of the Moon and Lunar theory
Earth as viewed from the Moon during the Apollo 8 mission, Christmas Eve, 1968
Earth and the Moon, from 50,000,000 km, taken by Deep ImpactThe Moon makes a complete orbit around the Earth with respect to the fixed stars about once every 27.3 days (its sidereal period). However, since the Earth is moving in its orbit about the Sun at the same time, it takes slightly longer for the Moon to show its same phase to Earth, which is about 29.5 days (its synodic period).[6] Unlike most satellites of other planets, the Moon orbits near the ecliptic and not the Earth's equatorial plane. It is the largest moon in the solar system relative to the size of its planet. (Charon is larger relative to the dwarf planet Pluto.) The natural satellites orbiting other planets are called "moons", after Earth's Moon.
Most of the tidal effects seen on the Earth are caused by the Moon's gravitational pull, with the Sun making a somewhat smaller contribution. Tidal drag slows the Earth's rotation by about 0.002 seconds per day per century.[52] As a result of the conservation of angular momentum, the slowing of Earth's rotation is accompanied by an increase of the mean Earth-Moon distance of about 3.8 m per century, or 3.8 cm per year.[53] The Moon is exceptionally large relative to the Earth, being a quarter the diameter of the planet and 1/81 its mass. However, the Earth and Moon are still commonly considered a planet-satellite system, rather than a double-planet system, since the common centre of mass of the system (the barycentre) is located about 1,700 km beneath the surface of the Earth, or about a quarter of the Earth's radius. The surface of the Moon is less than one-tenth that of the Earth, and only about a quarter the size of the Earth's land area (or about as large as Russia, Canada, and the U.S. combined).
In 1997, the asteroid 3753 Cruithne was found to have an unusual Earth-associated horseshoe orbit. However, astronomers do not consider it to be a second moon of Earth, and its orbit is not stable in the long term.[54] Three other near-Earth asteroids, 54509 YORP, (85770) 1998 UP1 and 2002 AA29, which exist in orbits similar to Cruithne's, have since been discovered.[55]
The relative sizes and separation of the Earth–Moon system are shown to scale above. The beam of light is depicted travelling between the Earth and the Moon in the same time it actually takes light to scale the real distance between them: 1.255 seconds at its mean orbital distance. The light beam helps provide the sense of scale of the Earth-Moon system relative to the Sun, which is 8.28 light-minutes away (photosphere to Earth surface).
Ocean tides
Earth's ocean tides are initiated by the tidal force (a gradient in intensity) of Moon's gravity and are magnified by a host of effects in Earth's oceans. The gravitational tidal force arises because the side of Earth facing the Moon (nearest it) is attracted more strongly by the Moon's gravity than is the center of the Earth and—even less so—the Earth's far side. The gravitational tide stretches the Earth's oceans into an ellipse with the Earth in the center. The effect takes the form of two bulges—elevated sea level relative to the Earth; one nearest the Moon and one farthest from it. Since these two bulges rotate around the Earth once a day as it spins on its axis, ocean water is continuously rushing towards the ever-moving bulges. The effects of the two bulges and the massive ocean currents chasing them are magnified by an interplay of other effects; namely frictional coupling of water to Earth's rotation through the ocean floors, inertia of water's movement, ocean basins that get shallower near land, and oscillations between different ocean basins. The magnifying effect is a bit like water sloshing high up the sloped end of a bathtub after a relatively small disturbance of one's body in the deep part of the tub.
Gravitational coupling between the Moon and the ocean bulge nearest the Moon affects its orbit. The Earth rotates on its axis in the very same direction, and roughly 27 times faster, than the Moon orbits the Earth. Thus, frictional coupling between the sea floors and ocean waters, as well as water's inertia, drags the peak of the near-Moon tidal bulge slightly forward of the imaginary line connecting the centers of the Earth and Moon. From the Moon's perspective, the center of mass of the near-Moon tidal bulge is perpetually slightly ahead of the point about which it is orbiting. Precisely the opposite effect occurs with the bulge farthest from the Moon; it lags behind the imaginary line. However it is 12,756 km farther away and has slightly less gravitational coupling to the Moon. Consequently, the Moon is constantly being gravitationally attracted forward in its orbit about the Earth. This gravitational coupling drains kinetic energy and angular momentum from the Earth's rotation (see also, Day and Leap second). In turn, angular momentum is added to the Moon's orbit, which lifts the Moon into a higher orbit with a longer period. The effect on the Moon's orbital radius is a small one, just 0.10 ppb/year, but results in a measurable 3.82 cm annual increase in the Earth-Moon distance.[53] Cumulatively, this effect becomes ever more significant over time; since astronauts first landed on the Moon approximately 40 years ago, it is 1.52 metres farther away.
Eclipses
Main articles: Solar eclipse and Lunar eclipse
The 1999 solar eclipse
The March 3, 2007 lunar eclipseEclipses can occur only when the Sun, Earth, and Moon are all in a straight line. Solar eclipses occur near a new moon, when the Moon is between the Sun and Earth. In contrast, lunar eclipses occur near a full moon, when the Earth is between the Sun and Moon.
Because the Moon's orbit around the Earth is inclined by about 5° with respect to the orbit of the Earth around the Sun, eclipses do not occur at every full and new moon. For an eclipse to occur, the Moon must be near the intersection of the two orbital planes.[56]
The periodicity and recurrence of eclipses of the Sun by the Moon, and of the Moon by the Earth, is described by the saros cycle, which has a period of approximately 6 585.3 days (18 years 11 days 8 hours).[57]
The angular diameters of the Moon and the Sun as seen from Earth overlap in their variation, so that both total and annular solar eclipses are possible.[58] In a total eclipse, the Moon completely covers the disc of the Sun and the solar corona becomes visible to the naked eye. Since the distance between the Moon and the Earth is very slightly increasing over time, the angular diameter of the Moon is decreasing. This means that hundreds of millions of years ago the Moon could always completely cover the Sun on solar eclipses so that no annular eclipses were possible. Likewise, about 600 million years from now (assuming that the angular diameter of the Sun will not change), the Moon will no longer cover the Sun completely and only annular eclipses will occur.[56]
A phenomenon related to eclipse is occultation. The Moon is continuously blocking our view of the sky by a 1/2 degree-wide circular area. When a bright star or planet passes behind the Moon it is occulted or hidden from view. A solar eclipse is an occultation of the Sun. Because the Moon is close to Earth, occultations of individual stars are not visible everywhere, nor at the same time. Because of the precession of the lunar orbit, each year different stars are occulted.[59]
The most recent lunar eclipse was on February 20, 2008. It was a total eclipse. The entire event was visible from South America and most of North America (on Feb. 20), as well as Western Europe, Africa, and western Asia (on Feb. 21). The most recent solar eclipse took place on September 11, 2007, visible from southern South America and parts of Antarctica. The last total solar eclipse, on August 1, 2008, had a path of totality that began in northern Canada and passed through Russia and China.[60]
Observation
See also: Lunar phase, Earthshine, and Observing the Moon
During its brightest phase, at "full moon", the Moon has an apparent magnitude of about −12.6. By comparison, the Sun has an apparent magnitude of −26.8. When the Moon is in a quarter phase, its brightness is not half of a full moon, but only about a tenth. This is because the lunar surface is not a perfect Lambertian reflector. When the Moon is full the opposition effect makes it appear brighter, but away from full there are shadows projected onto the surface which diminish the amount of reflected light.
The Moon appears larger when close to the horizon. This is a purely psychological effect (see Moon illusion). It is actually about 1.5% smaller when the Moon is near the horizon than when it is high in the sky (because it is farther away by up to one Earth radius).
The moon appears as a relatively bright object in the sky, in spite of its low albedo. The Moon is about the poorest reflector in the solar system and reflects only about 7% of the light incident upon it (about the same proportion as is reflected by a lump of coal).[61] Color constancy in the visual system recalibrates the relations between the colours of an object and its surroundings, and since the surrounding sky is comparatively dark the sunlit Moon is perceived as a bright object.
A halo around the MoonThe highest altitude of the Moon on a day varies and has nearly the same limits as the Sun. It also depends on the Earth season and lunar phase, with the full moon being highest in winter. Moreover, the 18.6 year nodes cycle also has an influence, as when the ascending node of the lunar orbit is in the vernal equinox, the lunar declination can go as far as 28° each month (which happened most recently in 2006). This results that the Moon can go overhead on latitudes up to 28 degrees from the equator (e.g. Florida, Canary Islands or in the southern hemisphere Brisbane). Slightly more than 9 years later (next time in 2015) the declination reaches only 18° N or S each month. The orientation of the Moon's crescent also depends on the latitude of the observation site. Close to the equator, an observer can see a boat Moon.[62]
Like the Sun, the Moon can give rise to atmospheric effects, including a 22° halo ring, and the smaller coronal rings seen more often through thin clouds. For more information on how the Moon appears in Earth's sky, see lunar phase.
Exploration
Main articles: Exploration of the Moon, Apollo program, and Moon landing
See also: Robotic exploration of the Moon, Future lunar missions, and Colonization of the Moon
The first leap in lunar observation was prompted by the invention of the telescope. Galileo Galilei made good use of this new instrument and observed mountains and craters on the Moon's surface.
The Cold War-inspired space race between the Soviet Union and the U.S. led to an acceleration of interest in the Moon. Unmanned probes, both flyby and impact/lander missions, were sent almost as soon as launcher capabilities would allow. The Soviet Union's Luna program was the first to reach the Moon with unmanned spacecraft. The first man-made object to escape Earth's gravity and pass near the Moon was Luna 1, the first man-made object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9 and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966.[6] Moon samples have been brought back to Earth by three Luna missions (Luna 16, 20, and 24) and the Apollo missions 11 to 17 (except Apollo 13, which aborted its planned lunar landing).
The landing of the first humans on the Moon in 1969 is seen by many as the culmination of the space race.[63] Neil Armstrong became the first person to walk on the Moon as the commander of the American mission Apollo 11 by first setting foot on the Moon at 02:56 UTC on July 21, 1969. The American Moon landing and return was enabled by considerable technological advances, in domains such as ablation chemistry and atmospheric re-entry technology, in the early 1960s.
Scientific instrument packages were installed on the lunar surface during all of the Apollo missions. Long-lived ALSEP stations (Apollo lunar surface experiment package) were installed at the Apollo 12, 14, 15, 16, and 17 landing sites, whereas a temporary station referred to as EASEP (Early Apollo Scientific Experiments Package) was installed during the Apollo 11 mission. The ALSEP stations contained, among others, heat flow probes, seismometers, magnetometers, and corner-cube retroreflectors. Transmission of data to Earth was terminated on September 30, 1977 because of budgetary considerations.[64][65] Since the lunar laser ranging (LLR) corner-cube arrays are passive instruments, they are still being used. Ranging to the LLR stations is routinely performed from earth-based stations with an accuracy of a few centimetres, and data from this experiment are being used to place constraints on the size of the lunar core.[66]
&0000000000000036.00000036 years, &0000000000000138.000000138 days have now passed since Eugene Cernan and Harrison Schmitt, as part of the mission Apollo 17, left the surface of the Moon on December 14, 1972 (Cernan being the last to enter the LM) and no one has set foot on it since.
Astronaut Buzz Aldrin photographed by Neil Armstrong during the first moon landing on July 20, 1969.From the mid-1960s to the mid-1970s, there were 65 instances of artificial objects reaching the Moon (both manned and robotic, with ten in 1971 alone), with the last being Luna 24 in 1976. Only 18 of these were controlled moon landings, with nine completing a round trip from Earth and returning samples of moon rocks. The Soviet Union then turned its primary attention to Venus and space stations, and the U.S. to Mars and beyond. In 1990, Japan orbited the Moon with the Hiten spacecraft, becoming the third country to place a spacecraft into lunar orbit. The spacecraft released a smaller probe, Hagormo, in lunar orbit, but the transmitter failed, thereby preventing further scientific use of the mission.
In 1994, the U.S. finally returned to the Moon, robotically at least, sending the Joint Defense Department/NASA spacecraft Clementine. This mission obtained the first near-global topographic map of the Moon, and the first global multispectral images of the lunar surface. This was followed by the Lunar Prospector mission in 1998. The neutron spectrometer on Lunar Prospector indicated the presence of excess hydrogen at the lunar poles, which is likely to have been caused by the presence of water ice in the upper few metres of the regolith within permanently shadowed craters. The European spacecraft Smart 1 was launched September 27, 2003 and was in lunar orbit from November 15, 2004 to September 3, 2006.
On January 14, 2004, U.S. President George W. Bush called for a plan to resume manned missions to the Moon by 2020 (see Vision for Space Exploration).[67] NASA is now planning for the construction of a permanent outpost at one of the lunar poles.[68] The People's Republic of China has expressed ambitious plans for exploring the Moon and has started the Chang'e program for lunar exploration, successfully launching its first spacecraft, Chang'e-1, on October 24, 2007. Like NASA, China hopes to land people on the Moon by 2020.[69] The U.S. will launch the Lunar Reconnaissance Orbiter and the Lunar Crater Observation and Sensing Satellite in late April 2009 (the two missions are co-manifested). Russia also announced to resume its previously frozen project Luna-Glob, consisting of an unmanned lander and orbiter, which is slated to land in 2012.[70]
The Google Lunar X Prize, announced September 13, 2007, hopes to boost and encourage privately funded lunar exploration. The X Prize Foundation is offering anyone US$20 million who can land a robotic rover on the Moon and meet other specified criteria.
On September 14, 2007 the Japan Aerospace Exploration Agency launched SELENE, also known as Kaguya, a lunar orbiter which is fitted with a high-definition camera and two small satellites. The mission is expected to last one year.[71]
On October 22, 2008 India successfully launched the Chandrayaan I (a Sanskrit word literally meaning the 'Moon-craft') unmanned mission to the Moon and intends to launch several further unmanned missions. The country plans to launch Chandrayaan II in 2010 or 2011, which is slated to include a robotic lunar rover. India also has expressed its hope for a manned mission to the Moon by 2020.[72]
Human understanding
See also: The Moon in mythology, Moon in art and literature, Lunar effect, and Lunar deity
Map of the Moon by Johannes Hevelius (1647)The Moon has been the subject of many works of art and literature and the inspiration for countless others. It is a motif in the visual arts, the performing arts, poetry, prose and music. A 5000-year-old rock carving at Knowth, Ireland may represent the Moon, which would be the earliest depiction discovered.[73] In many prehistoric and ancient cultures, the Moon was thought to be a deity or other supernatural phenomenon, and astrological views of the Moon continue to be propagated today.
Among the first in the Western world to offer a scientific explanation for the Moon was the Greek philosopher Anaxagoras (d. 428 BC), who reasoned that the Sun and Moon were both giant spherical rocks, and that the latter reflected the light of the former. His atheistic view of the heavens was one cause for his imprisonment and eventual exile.[74]
In Aristotle's (384–322 BC) description of the universe, the Moon marked the boundary between the spheres of the mutable elements (earth, water, air and fire), and the imperishable stars of aether. This separation was held to be part of physics for many centuries after.[75]
Moon against the Belt of VenusDuring the Warring States of China, astronomer Shi Shen (fl. 4th century BC) gave instructions for predicting solar and lunar eclipses based on the relative positions of the moon and sun.[76] Although the Chinese of the Han Dynasty (202 BC–202 AD) believed the moon to be energy equated to qi, their 'radiating influence' theory recognized that the light of the moon was merely a reflection of the sun (mentioned by Anaxagoras above).[77] This was supported by mainstream thinkers such as Jing Fang (78–37 BC) and Zhang Heng (78–139 AD), but it was also opposed by the influential philosopher Wang Chong (27–97 AD).[77] Jing Fang noted the sphericity of the moon, while Zhang Heng accurately described a lunar eclipse and solar eclipse.[77][78] These assertions were supported by Shen Kuo (1031–1095) of the Song Dynasty (960–1279) who created an allegory equating the waxing and waning of the moon to a round ball of reflective silver that, when doused with white powder and viewed from the side, would appear to be a crescent.[79] He also noted that the reason for the sun and moon not eclipsing every time their paths met was because of a small obliquity in their orbital paths.[79]
By the Middle Ages, before the invention of the telescope, more and more people began to recognise the Moon as a sphere, though they believed that it was "perfectly smooth".[80] In 1609, Galileo Galilei drew one of the first telescopic drawings of the Moon in his book Sidereus Nuncius and noted that it was not smooth but had mountains and craters. Later in the 17th century, Giovanni Battista Riccioli and Francesco Maria Grimaldi drew a map of the Moon and gave many craters the names they still have today.
Still from silent film Le Voyage dans la Lune (1902) by Georges MélièsOn maps, the dark parts of the Moon's surface were called maria (singular mare) or seas, and the light parts were called terrae or continents. The possibility that the Moon contains vegetation and is inhabited by selenites was seriously considered by major astronomers even into the first decades of the 19th century. The contrast between the brighter highlands and darker maria create the patterns seen by different cultures as the Man in the Moon, the rabbit and the buffalo, among others.
In 1835, the Great Moon Hoax fooled some people into thinking that there were exotic animals living on the Moon.[81] Almost at the same time however (during 1834–1836), Wilhelm Beer and Johann Heinrich Mädler were publishing their four-volume Mappa Selenographica and the book Der Mond in 1837, which firmly established the conclusion that the Moon has no bodies of water nor any appreciable atmosphere.
The far side of the Moon remained completely unknown until the Luna 3 probe was launched in 1959, and it was extensively mapped by the Lunar Orbiter program in the 1960s.
Legal status
Main article: Space law
Although several pennants of the Soviet Union were scattered by Luna 2 in 1959 and by later landing missions, and U.S. flags have been symbolically planted on the Moon, no nation currently claims ownership of any part of the Moon's surface. Russia and the U.S. are party to the Outer Space Treaty, which places the Moon under the same jurisdiction as international waters (res communis). This treaty also restricts the use of the Moon to peaceful purposes, explicitly banning military installations and weapons of mass destruction (including nuclear weapons).[82]
A second treaty, the Moon Treaty, was proposed to restrict the exploitation of the Moon's resources by any single nation, but it has not been signed by any of the space-faring nations. Several individuals have made claims to the Moon in whole or in part, although none of these are generally considered credible
SPACE
Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction.[1] Physical space is often conceived in three linear dimensions, although modern physicists usually consider it, with time, to be part of the boundless four-dimensional continuum known as spacetime. In mathematics spaces with different numbers of dimensions and with different underlying structures can be examined. The concept of space is considered to be of fundamental importance to an understanding of the universe although disagreement continues between philosophers over whether it is itself an entity, a relationship between entities, or part of a conceptual framework.
Many of the philosophical questions arose in the 17th century, during the early development of classical mechanics. In Isaac Newton's view, space was absolute - in the sense that it existed permanently and independently of whether there were any matter in the space.[2] Other natural philosophers, notably Gottfried Leibniz, thought instead that space was a collection of relations between objects, given by their distance and direction from one another. In the 18th century, Immanuel Kant described space and time as elements of a systematic framework which humans use to structure their experience.
In the 19th and 20th centuries mathematicians began to examine non-Euclidean geometries, in which space can be said to be curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space.[3] Experimental tests of general relativity have confirmed that non-Euclidean space provides a better model for explaining the existing laws of mechanics and optics.
Philosophy of space
In the early 11th century Islamic philosopher and physicist, Ibn al-Haytham (also known as Alhacen or Alhazen), discussed space perception and its epistemological implications in his Book of Optics (1021). His experimental proof of the intromission model of vision led to changes in the way the visual perception of space was understood, contrary to the previous emission theory of vision supported by Euclid and Ptolemy. In "tying the visual perception of space to prior bodily experience, Alhacen unequivocally rejected the intuitiveness of spatial perception and, therefore, the autonomy of vision. Without tangible notions of distance and size for correlation, sight can tell us next to nothing about such things."[4]
Leibniz and Newton
Gottfried LeibnizIn the seventeenth century, the philosophy of space and time emerged as a central issue in epistemology and metaphysics. At its heart, Gottfried Leibniz, the German philosopher-mathematician, and Isaac Newton, the English physicist-mathematician, set out two opposing theories of what space is. Rather than being an entity which independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: "space is that which results from places taken together".[5] Unoccupied regions are those which could have objects in them and thus spatial relations with other places. For Leibniz, then, space was an idealised abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete.[6] Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people.[7] Leibniz argued that space could not exist independently of objects in the world because that would imply that there would be a difference between two universes exactly alike except for the location of the material world in each universe. But since there would be no observational way of telling these universes apart then, according to the identity of indiscernibles, there would be no real difference between them. According to the principle of sufficient reason, any theory of space which implied that there could be these two possible universes, must therefore be wrong.
Isaac NewtonNewton took space to be more than relations between material objects and based his position on observation and experimentation. For a relationist there can be no real difference between inertial motion, in which the object travels with constant velocity, and non-inertial motion, in which the velocity changes with time, since all spatial measurements are relative to other objects and their motions. But Newton argued that since non-inertial motion generates forces, it must be absolute.[9] He used the example of water in a spinning bucket to demonstrate his argument. Water in a bucket is hung from a rope and set to spin, starts with a flat surface. After a while, as the bucket continues to spin, the surface of the water becomes concave. If the bucket's spinning is stopped then the surface of the water remains concave as it continues to spin. The concave surface is therefore apparently not the result of relative motion between the bucket and the water[10]. Instead, Newton argued, it must be a result of non-inertial motion relative to space itself. For several centuries the bucket argument was decisive in showing that space must exist independently of matter.
Kant
Immanuel KantIn the eighteenth century the German philosopher Immanuel Kant developed a theory of knowledge in which knowledge about space can be both a priori and synthetic.[11] According to Kant, knowledge about space is synthetic, in that statements about space are not simply true by virtue of the meaning of the words in the statement. In his work, Kant rejected the view that space must be either a substance or relation. Instead he came to the conclusion that space and time are not discovered by humans to be objective features of the world, but are part of an unavoidable systematic framework for organizing our experiences.[12]
Non-Euclidean geometry
Spherical geometry is similar to elliptical geometry. On the surface of a sphere there are no parallel lines.Euclid's Elements contained five postulates which form the basis for Euclidean geometry. One of these, the parallel postulate has been the subject of debate among mathematicians for many centuries. It states that on any plane on which there is a straight line L1 and a point P not on L1, there is only one straight line L2 on the plane which passes through the point P and is parallel to the straight line L1. Until the 19th century, few doubted the truth of the postulate; instead debate centered over whether it was necessary as an axiom, or whether it was a theory which could be derived from the other axioms.[13] Around 1830 though, the Hungarian János Bolyai and the Russian Nikolai Ivanovich Lobachevsky separately published treatises on a type of geometry which does not include the parallel postulate, called hyperbolic geometry. In this geometry, there are an infinite number of parallel lines which pass through the point P. Consequently the sum of angles in a triangle is less than 180o and the ratio of a circle's circumference to its diameter is greater than pi. In the 1850s, Bernhard Riemann developed an equivalent theory of elliptical geometry, in which there are no parallel lines which pass through P. In this geometry, triangles have more than 180o and circles have a ratio of circumference to diameter which is less than pi.
Type of geometry Number of parallels Sum of angles in a triangle Ratio of circumference to diameter of circle Measure of curvature
Hyperbolic Infinite < 180o > π < 0
Euclidean 1 180o π 0
Elliptical 0 > 180o < π > 0
Gauss and Poincaré
Carl Friedrich GaussAlthough there was a prevailing Kantian consensus at the time, once non-Euclidean geometries had been formalised, some began to wonder whether or not physical space is curved. Carl Friedrich Gauss, the German mathematician, was the first to consider an empirical investigation of the geometrical structure of space. He thought of making a test of the sum of the angles of an enormous stellar triangle and there are reports he actually carried out a test, on a small scale, by triangulating mountain tops in Germany.
Henri PoincaréHenri Poincaré, a French mathematician and physicist of the late 19th century introduced an important insight which attempted to demonstrate the futility of any attempt to discover by experiment which geometry applies to space.[15] He considered the predicament which would face scientists if they were confined to the surface of an imaginary large sphere with particular properties, known as a sphere-world. In this world, the temperature is taken to vary in such a way that all objects expand and contract in similar proportions in different places on the sphere. With a suitable falloff in temperature, if the scientists try to use measuring rods to determine the sum of the angles in a triangle, they can be deceived into thinking that they inhabit a plane, rather than a spherical surface.[16] In fact, the scientists cannot in principle determine whether they inhabit a plane or sphere and, Poincaré argued, the same is true for the debate over whether real space is Euclidean or not. For him, it was a matter of convention which geometry was used to describe space.[17] Since Euclidean geometry is simpler than non-Euclidean geometry, he assumed the former would always be used to describe the 'true' geometry of the world.
Einstein
Albert EinsteinIn 1905, Albert Einstein published a paper on a special theory of relativity, in which he proposed that space and time be combined into a single construct known as spacetime. In this theory, the speed of light in a vacuum is the same for all observers - which has the result that two events that appear simultaneous to one particular observer will not be simultaneous to another observer if the observers are moving with respect to one another. Moreover, an observer will measure a moving clock to tick more slowly than one which is stationary with respect to them; and objects are measured to be shortened in the direction that they are moving with respect to the observer.
Over the following ten years Einstein worked on a general theory of relativity, which is a theory of how gravity interacts with spacetime. Instead of viewing gravity as a force field acting in spacetime, Einstein suggested that it modifies the geometric structure of spacetime itself.[19] According to the general theory, time goes more slowly at places with lower gravitational potentials and rays of light bend in the presence of a gravitational field. Scientists have studied the behaviour of binary pulsars, confirming the predictions of Einstein's theories and Non-Euclidean geometry is usually used to describe spacetime.
Mathematics
In modern mathematics, spaces are frequently described as different types of manifolds which are spaces that locally approximate to Euclidean space and where the properties are defined largely on local connectedness of points that lie on the manifold.
Physics
Classical mechanics
Classical mechanics
Newton's Second Law
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Space is one of the few fundamental quantities in physics, meaning that it cannot be defined via other quantities because nothing more fundamental is known at the present. On the other hand, it can be related to other fundamental quantities. Thus, similar to other fundamental quantities (like time and mass), space can be explored via measurement and experiment.
Astronomy
Main article: Astronomy
Astronomy is the science involved with the observation, explanation and measuring of objects in outer space.
Relativity
Main article: Theory of relativity
Before Einstein's work on relativistic physics, time and space were viewed as independent dimensions. Einstein's discoveries showed that due to relativity of motion our space and time can be mathematically combined into one object — spacetime. It turns out that distances in space or in time separately are not invariant with respect to Lorentz coordinate transformations, but distances in Minkowski space-time along space-time intervals are — which justifies the name.
In addition, time and space dimensions should not be viewed as exactly equivalent in Minkowski space-time. One can freely move in space but not in time. Thus, time and space coordinates are treated differently both in special relativity (where time is sometimes considered an imaginary coordinate) and in general relativity (where different signs are assigned to time and space components of spacetime metric).
Furthermore, from Einstein's general theory of relativity, it has been shown that space-time is geometrically distorted- curved -near to gravitationally significant masses.
Experiments are ongoing to attempt to directly measure gravitational waves. This is essentially solutions to the equations of general relativity which describe moving ripples of spacetime. Indirect evidence for this has been found in the motions of the Hulse-Taylor binary system.
Cosmology
Main article: Shape of the universe
Relativity theory lead to the cosmological question of what shape the universe is, and where space came from. It appears that space was created in the Big Bang and has been expanding ever since. The overall shape of space is not known, but space is known to be expanding very rapidly which is evident due to the Hubble expansion.
Spatial measurement
Main article: Measurement
The measurement of physical space has long been important. Although earlier societies had developed measuring systems, the International System of Units, (SI), is now the most common system of units used in the measuring of space, and is almost universally used within science.
Currently, the standard space interval, called a standard meter or simply meter, is defined as the distance traveled by light in a vacuum during a time interval of exactly 1/299,792,458 of a second. This definition coupled with present definition of the second is based on the special theory of relativity, that our space-time is a Minkowski space.[citation needed]
Geography
Geography is the branch of science concerned with identifying and describing the Earth, utilizing spatial awareness to try and understand why things exist in specific locations. Cartography is the mapping of spaces to allow better navigation, for visualization purposes and to act as a locational device. Geostatistics apply statistical concepts to collected spatial data in order to create an estimate for unobserved phenomena.
Geographical space is often considered as land, and can have a relation to ownership usage (in which space is seen as property or territory). While some cultures assert the rights of the individual in terms of ownership, other cultures will identify with a communal approach to land ownership, while still other cultures such as Australian Aboriginals, rather than asserting ownership rights to land, invert the relationship and consider that they are in fact owned by the land. Spatial planning is a method of regulating the use of space at land-level, with decisions made at regional, national and international levels. Space can also impact on human and cultural behavior, being an important factor in architecture, where it will impact on the design of buildings and structures, and on farming.
Ownership of space is not restricted to land. Ownership of airspace and of waters is decided internationally. Other forms of ownership have been recently asserted to other spaces — for example to the radio bands of the electromagnetic spectrum or to cyberspace.
Public space is a term used to define areas of land as collectively owned by the community, and managed in their name by delegated bodies; such spaces are open to all. While private property is the land culturally owned by an individual or company, for their own use and pleasure.
Abstract space is a term used in geography to refer to a hypothetical space characterized by complete homogeneity. When modeling activity or behavior, it is a conceptual tool used to limit extraneous variables such as terrain.
In psychology
The way in which space is perceived is an area which psychologists first began to study in the middle of the 19th century, and it is now thought by those concerned with such studies to be a distinct branch within psychology. Psychologists analyzing the perception of space are concerned with how recognition of an object's physical appearance or its interactions are perceived.
Other, more specialized topics studied include amodal perception and object permanence. The perception of surroundings is important due to its necessary relevance to survival, especially with regards to hunting and self preservation as well as simply one's idea of personal space.
Several space-related phobias have been identified, including agoraphobia (the fear of open spaces), astrophobia (the fear of celestial space) and claustrophobia (the fear of enclosed spaces).
Many of the philosophical questions arose in the 17th century, during the early development of classical mechanics. In Isaac Newton's view, space was absolute - in the sense that it existed permanently and independently of whether there were any matter in the space.[2] Other natural philosophers, notably Gottfried Leibniz, thought instead that space was a collection of relations between objects, given by their distance and direction from one another. In the 18th century, Immanuel Kant described space and time as elements of a systematic framework which humans use to structure their experience.
In the 19th and 20th centuries mathematicians began to examine non-Euclidean geometries, in which space can be said to be curved, rather than flat. According to Albert Einstein's theory of general relativity, space around gravitational fields deviates from Euclidean space.[3] Experimental tests of general relativity have confirmed that non-Euclidean space provides a better model for explaining the existing laws of mechanics and optics.
Philosophy of space
In the early 11th century Islamic philosopher and physicist, Ibn al-Haytham (also known as Alhacen or Alhazen), discussed space perception and its epistemological implications in his Book of Optics (1021). His experimental proof of the intromission model of vision led to changes in the way the visual perception of space was understood, contrary to the previous emission theory of vision supported by Euclid and Ptolemy. In "tying the visual perception of space to prior bodily experience, Alhacen unequivocally rejected the intuitiveness of spatial perception and, therefore, the autonomy of vision. Without tangible notions of distance and size for correlation, sight can tell us next to nothing about such things."[4]
Leibniz and Newton
Gottfried LeibnizIn the seventeenth century, the philosophy of space and time emerged as a central issue in epistemology and metaphysics. At its heart, Gottfried Leibniz, the German philosopher-mathematician, and Isaac Newton, the English physicist-mathematician, set out two opposing theories of what space is. Rather than being an entity which independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: "space is that which results from places taken together".[5] Unoccupied regions are those which could have objects in them and thus spatial relations with other places. For Leibniz, then, space was an idealised abstraction from the relations between individual entities or their possible locations and therefore could not be continuous but must be discrete.[6] Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people.[7] Leibniz argued that space could not exist independently of objects in the world because that would imply that there would be a difference between two universes exactly alike except for the location of the material world in each universe. But since there would be no observational way of telling these universes apart then, according to the identity of indiscernibles, there would be no real difference between them. According to the principle of sufficient reason, any theory of space which implied that there could be these two possible universes, must therefore be wrong.
Isaac NewtonNewton took space to be more than relations between material objects and based his position on observation and experimentation. For a relationist there can be no real difference between inertial motion, in which the object travels with constant velocity, and non-inertial motion, in which the velocity changes with time, since all spatial measurements are relative to other objects and their motions. But Newton argued that since non-inertial motion generates forces, it must be absolute.[9] He used the example of water in a spinning bucket to demonstrate his argument. Water in a bucket is hung from a rope and set to spin, starts with a flat surface. After a while, as the bucket continues to spin, the surface of the water becomes concave. If the bucket's spinning is stopped then the surface of the water remains concave as it continues to spin. The concave surface is therefore apparently not the result of relative motion between the bucket and the water[10]. Instead, Newton argued, it must be a result of non-inertial motion relative to space itself. For several centuries the bucket argument was decisive in showing that space must exist independently of matter.
Kant
Immanuel KantIn the eighteenth century the German philosopher Immanuel Kant developed a theory of knowledge in which knowledge about space can be both a priori and synthetic.[11] According to Kant, knowledge about space is synthetic, in that statements about space are not simply true by virtue of the meaning of the words in the statement. In his work, Kant rejected the view that space must be either a substance or relation. Instead he came to the conclusion that space and time are not discovered by humans to be objective features of the world, but are part of an unavoidable systematic framework for organizing our experiences.[12]
Non-Euclidean geometry
Spherical geometry is similar to elliptical geometry. On the surface of a sphere there are no parallel lines.Euclid's Elements contained five postulates which form the basis for Euclidean geometry. One of these, the parallel postulate has been the subject of debate among mathematicians for many centuries. It states that on any plane on which there is a straight line L1 and a point P not on L1, there is only one straight line L2 on the plane which passes through the point P and is parallel to the straight line L1. Until the 19th century, few doubted the truth of the postulate; instead debate centered over whether it was necessary as an axiom, or whether it was a theory which could be derived from the other axioms.[13] Around 1830 though, the Hungarian János Bolyai and the Russian Nikolai Ivanovich Lobachevsky separately published treatises on a type of geometry which does not include the parallel postulate, called hyperbolic geometry. In this geometry, there are an infinite number of parallel lines which pass through the point P. Consequently the sum of angles in a triangle is less than 180o and the ratio of a circle's circumference to its diameter is greater than pi. In the 1850s, Bernhard Riemann developed an equivalent theory of elliptical geometry, in which there are no parallel lines which pass through P. In this geometry, triangles have more than 180o and circles have a ratio of circumference to diameter which is less than pi.
Type of geometry Number of parallels Sum of angles in a triangle Ratio of circumference to diameter of circle Measure of curvature
Hyperbolic Infinite < 180o > π < 0
Euclidean 1 180o π 0
Elliptical 0 > 180o < π > 0
Gauss and Poincaré
Carl Friedrich GaussAlthough there was a prevailing Kantian consensus at the time, once non-Euclidean geometries had been formalised, some began to wonder whether or not physical space is curved. Carl Friedrich Gauss, the German mathematician, was the first to consider an empirical investigation of the geometrical structure of space. He thought of making a test of the sum of the angles of an enormous stellar triangle and there are reports he actually carried out a test, on a small scale, by triangulating mountain tops in Germany.
Henri PoincaréHenri Poincaré, a French mathematician and physicist of the late 19th century introduced an important insight which attempted to demonstrate the futility of any attempt to discover by experiment which geometry applies to space.[15] He considered the predicament which would face scientists if they were confined to the surface of an imaginary large sphere with particular properties, known as a sphere-world. In this world, the temperature is taken to vary in such a way that all objects expand and contract in similar proportions in different places on the sphere. With a suitable falloff in temperature, if the scientists try to use measuring rods to determine the sum of the angles in a triangle, they can be deceived into thinking that they inhabit a plane, rather than a spherical surface.[16] In fact, the scientists cannot in principle determine whether they inhabit a plane or sphere and, Poincaré argued, the same is true for the debate over whether real space is Euclidean or not. For him, it was a matter of convention which geometry was used to describe space.[17] Since Euclidean geometry is simpler than non-Euclidean geometry, he assumed the former would always be used to describe the 'true' geometry of the world.
Einstein
Albert EinsteinIn 1905, Albert Einstein published a paper on a special theory of relativity, in which he proposed that space and time be combined into a single construct known as spacetime. In this theory, the speed of light in a vacuum is the same for all observers - which has the result that two events that appear simultaneous to one particular observer will not be simultaneous to another observer if the observers are moving with respect to one another. Moreover, an observer will measure a moving clock to tick more slowly than one which is stationary with respect to them; and objects are measured to be shortened in the direction that they are moving with respect to the observer.
Over the following ten years Einstein worked on a general theory of relativity, which is a theory of how gravity interacts with spacetime. Instead of viewing gravity as a force field acting in spacetime, Einstein suggested that it modifies the geometric structure of spacetime itself.[19] According to the general theory, time goes more slowly at places with lower gravitational potentials and rays of light bend in the presence of a gravitational field. Scientists have studied the behaviour of binary pulsars, confirming the predictions of Einstein's theories and Non-Euclidean geometry is usually used to describe spacetime.
Mathematics
In modern mathematics, spaces are frequently described as different types of manifolds which are spaces that locally approximate to Euclidean space and where the properties are defined largely on local connectedness of points that lie on the manifold.
Physics
Classical mechanics
Classical mechanics
Newton's Second Law
History of ... [hide]Fundamental concepts
Space · Time · Mass · Force
Energy · Momentum
[show]Formulations
Newtonian mechanics
Lagrangian mechanics
Hamiltonian mechanics
[show]Branches
Statics
Dynamics
Kinematics
Applied mechanics
Celestial mechanics
Continuum mechanics
Statistical mechanics
[show]Scientists
Newton · Euler · d'Alembert · Clairaut
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Space is one of the few fundamental quantities in physics, meaning that it cannot be defined via other quantities because nothing more fundamental is known at the present. On the other hand, it can be related to other fundamental quantities. Thus, similar to other fundamental quantities (like time and mass), space can be explored via measurement and experiment.
Astronomy
Main article: Astronomy
Astronomy is the science involved with the observation, explanation and measuring of objects in outer space.
Relativity
Main article: Theory of relativity
Before Einstein's work on relativistic physics, time and space were viewed as independent dimensions. Einstein's discoveries showed that due to relativity of motion our space and time can be mathematically combined into one object — spacetime. It turns out that distances in space or in time separately are not invariant with respect to Lorentz coordinate transformations, but distances in Minkowski space-time along space-time intervals are — which justifies the name.
In addition, time and space dimensions should not be viewed as exactly equivalent in Minkowski space-time. One can freely move in space but not in time. Thus, time and space coordinates are treated differently both in special relativity (where time is sometimes considered an imaginary coordinate) and in general relativity (where different signs are assigned to time and space components of spacetime metric).
Furthermore, from Einstein's general theory of relativity, it has been shown that space-time is geometrically distorted- curved -near to gravitationally significant masses.
Experiments are ongoing to attempt to directly measure gravitational waves. This is essentially solutions to the equations of general relativity which describe moving ripples of spacetime. Indirect evidence for this has been found in the motions of the Hulse-Taylor binary system.
Cosmology
Main article: Shape of the universe
Relativity theory lead to the cosmological question of what shape the universe is, and where space came from. It appears that space was created in the Big Bang and has been expanding ever since. The overall shape of space is not known, but space is known to be expanding very rapidly which is evident due to the Hubble expansion.
Spatial measurement
Main article: Measurement
The measurement of physical space has long been important. Although earlier societies had developed measuring systems, the International System of Units, (SI), is now the most common system of units used in the measuring of space, and is almost universally used within science.
Currently, the standard space interval, called a standard meter or simply meter, is defined as the distance traveled by light in a vacuum during a time interval of exactly 1/299,792,458 of a second. This definition coupled with present definition of the second is based on the special theory of relativity, that our space-time is a Minkowski space.[citation needed]
Geography
Geography is the branch of science concerned with identifying and describing the Earth, utilizing spatial awareness to try and understand why things exist in specific locations. Cartography is the mapping of spaces to allow better navigation, for visualization purposes and to act as a locational device. Geostatistics apply statistical concepts to collected spatial data in order to create an estimate for unobserved phenomena.
Geographical space is often considered as land, and can have a relation to ownership usage (in which space is seen as property or territory). While some cultures assert the rights of the individual in terms of ownership, other cultures will identify with a communal approach to land ownership, while still other cultures such as Australian Aboriginals, rather than asserting ownership rights to land, invert the relationship and consider that they are in fact owned by the land. Spatial planning is a method of regulating the use of space at land-level, with decisions made at regional, national and international levels. Space can also impact on human and cultural behavior, being an important factor in architecture, where it will impact on the design of buildings and structures, and on farming.
Ownership of space is not restricted to land. Ownership of airspace and of waters is decided internationally. Other forms of ownership have been recently asserted to other spaces — for example to the radio bands of the electromagnetic spectrum or to cyberspace.
Public space is a term used to define areas of land as collectively owned by the community, and managed in their name by delegated bodies; such spaces are open to all. While private property is the land culturally owned by an individual or company, for their own use and pleasure.
Abstract space is a term used in geography to refer to a hypothetical space characterized by complete homogeneity. When modeling activity or behavior, it is a conceptual tool used to limit extraneous variables such as terrain.
In psychology
The way in which space is perceived is an area which psychologists first began to study in the middle of the 19th century, and it is now thought by those concerned with such studies to be a distinct branch within psychology. Psychologists analyzing the perception of space are concerned with how recognition of an object's physical appearance or its interactions are perceived.
Other, more specialized topics studied include amodal perception and object permanence. The perception of surroundings is important due to its necessary relevance to survival, especially with regards to hunting and self preservation as well as simply one's idea of personal space.
Several space-related phobias have been identified, including agoraphobia (the fear of open spaces), astrophobia (the fear of celestial space) and claustrophobia (the fear of enclosed spaces).
THE EIFFEL TOWER
The Eiffel Tower (French: Tour Eiffel, /tuʀ ɛfɛl/) is an iron tower built on the Champ de Mars beside the Seine River in Paris. The tower has become a global icon of France and is one of the most recognizable structures in the world.
Introduction
Named after its designer, engineer Gustave Eiffel, the Eiffel Tower is the tallest building in Paris.[1] More than 200,000,000 people have visited the tower since its construction in 1889,[2] including 6,719,200 in 2006,[3] making it the most visited paid monument in the world.[4][5] Including the 24 m (79 ft) antenna, the structure is 324 m (1,063 ft) high (since 2000), which is equivalent to about 81 levels in a conventional building.
Eiffel Tower October 2007 When the tower was completed in 1889 it was the world's tallest tower — a title it retained until 1930 when New York City's Chrysler Building (319 m — 1,047 ft tall) was completed.[6] The tower is now the fifth-tallest structure in France and the tallest structure in Paris, with the second-tallest being the Tour Montparnasse (210 m — 689 ft), although that will soon be surpassed by Tour AXA (225.11 m — 738.36 ft).
Eiffel Tower from the neighborhood.The metal structure of the Eiffel Tower weighs 7,300 tonnes while the entire structure including non-metal components is approximately 10,000 tonnes. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7 in) because of thermal expansion of the metal on the side facing the sun. The tower also sways 6–7 cm (2–3 in) in the wind.[3] As demonstration of the economy of design, if the 7300 tonnes of the metal structure were melted down it would fill the 125 meter square base to a depth of only 6 cm (2.36 in), assuming a density of the metal to be 7.8 tonnes per cubic meter. The tower has a mass less than the mass of the air contained in a cylinder of the same dimensions,[7] that is 324 meters high and 88.3 meters in radius. The weight of the tower is 10,100 tonnes compared to 10,265 tonnes of air.
The first and second levels are accessible by stairways and lifts. A ticket booth at the south tower base sells tickets to access the stairs which begin at that location. At the first platform the stairs continue up from the east tower and the third level summit is only accessible by lift. From the first or second platform the stairs are open for anyone to ascend or descend regardless of whether they have purchased a lift ticket or stair ticket. The actual count of stairs includes 9 steps to the ticket booth at the base, 328 steps to the first level, 340 steps to the second level and 18 steps to the lift platform on the second level. When exiting the lift at the third level there are 15 more steps to ascend to the upper observation platform. The step count is printed periodically on the side of the stairs to give an indication of progress of ascent. The majority of the ascent allows for an unhindered view of the area directly beneath and around the tower although some short stretches of the stairway are enclosed.
Maintenance of the tower includes applying 50 to 60 tonnes of paint every seven years to protect it from rust. In order to maintain a uniform appearance to an observer on the ground, three separate colors of paint are used on the tower, with the darkest on the bottom and the lightest at the top. On occasion the colour of the paint is changed; the tower is currently painted a shade of brownish-grey.[8] On the first floor there are interactive consoles hosting a poll for the colour to use for a future session of painting. The co-architects of the Eiffel Tower are Emile Nouguier, Maurice Koechlin and Stephen Sauvestre.[9]
History
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Eiffel Tower under construction in July 1888.The structure was built between 1887 and 1889 as the entrance arch for the Exposition Universelle, a World's Fair marking the centennial celebration of the French Revolution. Eiffel originally planned to build the tower in Barcelona, for the Universal Exposition of 1888, but those responsible at the Barcelona city hall thought it was a strange and expensive construction, which did not fit into the design of the city. After the refusal of the Consistory of Barcelona, Eiffel submitted his draft to those responsible for the Universal Exhibition in Paris, where he would build his tower a year later, in 1889. The tower was inaugurated on 31 March 1889, and opened on 6 May. Three hundred workers joined together 18,038 pieces of puddled iron (a very pure form of structural iron), using two and a half million rivets, in a structural design by Maurice Koechlin. The risk of accident was great, for unlike modern skyscrapers the tower is an open frame without any intermediate floors except the two platforms. However, because Eiffel took safety precautions, including the use of movable stagings, guard-rails and screens, only one man died.
Eiffel Tower Construction view: girders at the first storyThe tower was met with much criticism from the public when it was built, with many calling it an eyesore. Newspapers of the day were filled with angry letters from the arts community of Paris. One is quoted extensively in William Watson's US Government Printing Office publication of 1892 Paris Universal Exposition: Civil Engineering, Public Works, and Architecture. “And during twenty years we shall see, stretching over the entire city, still thrilling with the genius of so many centuries, we shall see stretching out like a black blot the odious shadow of the odious column built up of riveted iron plates.”[10] Signers of this letter included Jean-Louis-Ernest Meissonier, Charles Gounod, Charles Garnier, Jean-Léon Gérôme, William-Adolphe Bouguereau, and Alexandre Dumas.
Novelist Guy de Maupassant — who claimed to hate the tower — supposedly ate lunch in the Tower's restaurant every day. When asked why, he answered that it was the one place in Paris where one could not see the structure. Today, the Tower is widely considered to be a striking piece of structural art.
One of the great Hollywood movie clichés is that the view from a Parisian window always includes the tower. In reality, since zoning restrictions limit the height of most buildings in Paris to 7 stories, only a very few of the taller buildings have a clear view of the tower.
Eiffel had a permit for the tower to stand for 20 years, meaning it would have had to be dismantled in 1909, when its ownership would revert to the City of Paris. The City had planned to tear it down (part of the original contest rules for designing a tower was that it could be easily demolished) but as the tower proved valuable for communication purposes, it was allowed to remain after the expiration of the permit. The military used it to dispatch Parisian taxis to the front line during the First Battle of the Marne, and it therefore became a victory statue of that battle.
Shape of the tower
Looking up at the Eiffel Tower.At the time the tower was built many people were shocked by its daring shape. Eiffel was criticised for the design and accused of trying to create something artistic, or inartistic according to the viewer, without regard to engineering. Eiffel and his engineers, as renowned bridge builders however, understood the importance of wind forces and knew that if they were going to build the tallest structure in the world they had to be certain it would withstand the wind. In an interview reported in the newspaper Le Temps, Eiffel said:
“ Now to what phenomenon did I give primary concern in designing the Tower? It was wind resistance. Well then! I hold that the curvature of the monument's four outer edges, which is as mathematical calculation dictated it should be (...) will give a great impression of strength and beauty, for it will reveal to the eyes of the observer the boldness of the design as a whole. ”
—translated from the French newspaper Le Temps of 14 February 1887[11]
The shape of the tower was therefore determined by mathematical calculation involving wind resistance. Several theories of this mathematical calculation have been proposed over the years, the most recent is a nonlinear integral differential equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point. That shape is exponential. A careful plot of the tower curvature however, reveals two different exponentials, the lower section having a stronger resistance to wind forces.[12][13]
Installations
Communications
The Eiffel tower and the Seine at night
The Eiffel tower illuminated in blue to celebrate the French presidency of the EU (July 2008.)Since the beginning of the 20th century, the tower has been used for radio transmission. Until the 1950s, an occasionally modified set of antenna wires ran from the summit to anchors on the Avenue de Suffren and Champ de Mars. They were connected to long-wave transmitters in small bunkers; in 1909, a permanent underground radio centre was built near the south pillar and still exists today.[citation needed] On 20 November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory which used an antenna in Arlington, Virginia. The object of the transmissions was to measure the difference in longitude between Paris and Washington, D.C.[14]
Restaurants
The tower has two restaurants: Altitude 95, on the first floor (95 m, 311 ft, above sea level); and the Jules Verne, an expensive gastronomical restaurant on the second floor, with a private lift. This restaurant has one star in the Michelin Red Guide. In January 2007, a new multi-Michelin star chef Alain Ducasse was brought in to run Jules Verne.[15]
Passenger Lifts
Ground to Second level
[16] [17] The original lifts to the first and second floors were provided by two companies. Both companies had to overcome many technical obstacles as neither company (or indeed any company) had experience with installing lifts climbing to such heights with large loads. The slanting tracks with changing angles further complicated the problems. The East and West lifts were supplied by the French company Roux Combaluzier Lepape, using hydraulically powered chains and rollers. Contemporary engravings of the lift cars show that the passengers were seated at this time but it is not clear whether this was conceptual. It would be unnecessary to seat passengers for a journey time of around a couple of minutes. The North and South lifts were provided by the American Otis company using car designs similar to the original installation but using an improved hydraulic and cable scheme. The French lifts had a very poor performance and were replaced with the current installations in 1897 (West Pillar) and 1899 (East Pillar) by Fives-Lille using an improved hydraulic and rope scheme. Both of the original installations operated broadly on the principle of the Fives-Lille lifts.
The Fives-Lille lifts from ground level to the first and second levels are operated by cables and pulleys driven by massive water-powered pistons. The hydraulic scheme was somewhat unusual for the time in that it included three large counterweights of 200 tonnes each sitting on top of hydraulic rams which doubled up as accumulators for the water. As the lifts ascend the inclined arc of the pillars, the angle of ascent changes. The two lift cabs are kept more or less level and indeed are level at the landings. The cab floors do take on a slight angle at times between landings.
The principle behind the lifts is similar to the operation of a block and tackle but in reverse. Two large hydraulic rams (over 1 metre diameter) with a 16 metre travel are mounted horizontally in the base of the pillar which pushes a carriage (the French word for it translates as chariot and this term will be used henceforth to distinguish it from the lift carriage) with 16 large triple sheaves mounted on it. There are 14 similar sheaves mounted staticly. Six wire ropes are rove back and forth between the sheaves such that each rope passes between the 2 sets of sheaves 7 times. The ropes then leave the final sheaves on the chariot and passes up through a series of guiding sheaves to above the second floor and then via a pair of triple sheaves back down to the lift carriage again passing guiding sheaves.
This arrangement means that the lift carriage complete with its cars and passengers travels 8 times the distance that the rams move the chariot which is the 128 metres from the ground to the second floor. The force exerted by the rams also has to be 8 times the total weight of the lift carriage, cars and passengers plus extra to cater for various losses such as friction. The hydraulic fluid was water, normally stored in the 3 accumulators complete with counterbalance weights. To make the lift ascend, water was pumped using an electrically driven pump from the accumulators to the two rams. Since the counterbalance weights provided much of the pressure required, the pump only had to provide the extra effort. For the descent, it was only necessary to allow the water to flow back to the accumulators using a control valve. The lifts were operated by an operator perched precariously underneath the lift cars. His position (with a dummy operator) can still be seen on the lifts today.
The Fives-Lille lifts were completely upgraded in 1986 to meet modern safety requirements and to make the lifts easier to operate. A new computer controlled system was installed which completely automated the operation. One of the three counterbalances was taken out of use, and the cars were replaced with a more modern and lighter structure. Most importantly, the main driving force was removed from the original water pump such that the water hydraulic system provided only a counterbalancing function. The main driving force was transferred to a 320 kW electrically driven oil hydraulic pump which drives a pair of hydraulic motors on the chariot itself thus providing the motive power. The new lift cars complete with their carriage and a full 92 passenger load weigh 22 tonnes.
Due to elasticity in the ropes and the time taken to get the cars level with the landings, each lift in normal service takes an average of 8 minutes and 50 seconds to do the round trip spending an average of 1 minute and 15 seconds at each floor. The average journey time between floors is just 1 minute.
The original Otis lifts in the North and South pillars in their turn proved inferior to the new (in 1899) French lifts and were scrapped from the south pillar in 1900 and from the north pillar in 1913 after failed attempts to re-power them with an electric motor. The north and south pillars were to remain without lifts until 1965 when increasing visitor numbers persuaded the operators to install a relatively standard and modern rope hoisted system in the north pillar using a rope hauled counterbalance weight, but hoisted by a block and tackle system to reduce its travel to one third of the lift travel. The counterbalance is clearly visible within the structure of the North pillar. This latter lift was upgraded in 1995 with new cars and computer controls.
The South tower acquired a completely new fairly standard electrically driven lift in 1983 to serve the Jules Verne restaurant. This was also supplied by Otis.
A further 4 tonne service lift was added to the south pillar in 1989 by Otis to relieve the main lifts when moving relatively small loads or even just maintenance personnel.
The east and west hydraulic (water) lift works are on display and, at least in theory, are open to the public in a small museum located in base of the East and West tower, which is somewhat hidden from public view. Because the massive mechanism requires frequent lubrication and attention, public access is often restricted. However, when open, the wait times are much less than the other, more popular, attractions. The rope mechanism of the North tower is visible to visitors as they exit from the lift.
Second to Third level
The original Hydraulic pump for the Edoux lifts.The original lift from the second to the third floor were also of a water powered hydraulic design supplied by Léon Edoux. Instead of using a separate counterbalance, the two lift cars counterbalanced each other. A pair of 81 metre long hydraulic rams were mounted on the second level reaching nearly half way up to the third level. A lift car was mounted on top of the rams. Ropes ran from the top of this car up to a sheave on the third level and back down to a second car. The result of this arrangement was that each car only travelled half the distance between the second and third levels and passengers were required to change lifts halfway walking between the cars along a narrow gangway with a very impressive and relatively unobstructed downward view. The 10 tonne cars held 65 passengers each or up to 4 tonnes.
One interesting feature of the original installation was that the hoisting rope ran through guides to retain it on windy days to prevent it flapping and becoming damaged. The guides were mechanically moved out of the way of the ascending car by the movement of the car itself. In spite of some antifreeze being added to the water that operated this system, it nevertheless had to close to the public from November to March each year.
The original spiral stairs to the third floor which were only 80 centimetres wide. Note also the small service lift in the background.The original lifts complete with their hydraulic mechanism were completely scrapped in 1982 after 97 years of service. They were replaced with two pairs of relatively standard rope hoisted cars which were able to operate all the year round. The cars operate in pairs with one providing the counterbalance for the other. Neither car can move unless both sets of doors are closed and both operators have given a start command. The commands from the cars to the hoising mechanism are by radio obviating the necessity of a control cable. The replacement installation also has the advantage that the ascent can be made without changing cars and has reduced the ascent time from 8 minutes (including change) to 1 minute and 40 seconds. This instalation also has guides for the hoisting ropes but they are electrically operated. The guide once it has moved out of the way as the car ascends automatically reverses when the car has passed to prevent the mechanism becoming snagged on the car on the downward journey in the event it has failed to completely clear the car. Unfortunately these lifts do not have the capacity to move as many people as the 3 public lower lifts and long queues to ascend to the third level are common. Most of the intermediate level structure present on the tower today was installed when the lifts were replaced and allows maintenance workers to take the lift half way.
The replacement of these lifts allowed the restructuring of the criss-cross beams in upper part of the tower and further allowed the installation of two emergency staircases. These replaced the dangerous winding stairs that were installed when the tower was constructed.
Events
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Lightning strikes the Eiffel Tower on June 3, 1902, at 9:20 P.M
The Eiffel Tower served as an advertising space for Citroën from 1925 to 1934.
On 10 September 1889, Thomas Edison visited the tower. He signed the guestbook with the following message—
“ To M Eiffel the Engineer the brave builder of so gigantic and original specimen of modern Engineering from one who has the greatest respect and admiration for all Engineers including the Great Engineer the Bon Dieu, Thomas Edison. ”
Father Theodor Wulf in 1910 took observations of radiant energy radiating at the top and bottom of the tower, discovering at the top more than was expected, and thereby detecting what are today known as cosmic rays.[18]
On 4 February 1912, Austrian tailor Franz Reichelt died after jumping 60 metres from the first deck of Eiffel tower with his home-made parachute.
In 1925, the con artist Victor Lustig "sold" the tower for scrap metal on two separate, but related occasions.
In 1930, the tower lost the title of the world's tallest structure when the Chrysler Building was completed in New York City.
From 1925 to 1934, illuminated signs for Citroën adorned three of the tower's four sides, making it the tallest advertising space in the world at the time.
Upon the Nazi occupation of Paris in 1940, the lift cables were cut by the French so that Adolf Hitler would have to climb the steps to the summit. The parts to repair them were allegedly impossible to obtain because of the war. In 1940 German soldiers had to climb to the top to hoist the swastika, but the flag was so large it blew away just a few hours later, and it was replaced by a smaller one. When visiting Paris, Hitler chose to stay on the ground. It was said that Hitler conquered France, but did not conquer the Eiffel Tower. A Frenchman scaled the tower during the German occupation to hang the French flag. In August 1944, when the Allies were nearing Paris, Hitler ordered General Dietrich von Choltitz, the military governor of Paris, to demolish the tower along with the rest of the city. Von Choltitz disobeyed the order. The lifts of the Tower were working normally within hours of the Liberation of Paris.
On 3 January 1956, a fire damaged the top of the tower.
In 1957, the present radio antenna was added to the top.
In the 1980s, an old restaurant and its supporting iron scaffolding midway up the tower was dismantled; it was purchased and reconstructed on St. Charles Avenue in New Orleans, Louisiana, by entrepreneurs John Onorio and Daniel Bonnot, originally as the Tour Eiffel Restaurant, known more recently as the Red Room. The restaurant was re-assembled from 11,000 pieces that crossed the Atlantic in a 40-foot (12 m) cargo container.
On 31 March 1984, Robert Moriarty flew a Beechcraft Bonanza through the arches of the tower.[19]
In 1985's James Bond action/adventure film A View to a Kill, Sir Roger Moore as James Bond chases May Day played by actress Grace Jones up the Eiffel Tower. She parachutes from the structure to escape. The video of the film's theme tune, performed by the group Duran Duran, also included several scenes of the band staged on the tower intercut with clips from the film. A full 20 years earlier, the Bond film Thunderball (1965) featured an establishing shot of the tower as the villainous Largo, played by Adolfo Celi, parks outside the headquarters of SPECTRE in Paris.
In 1987, A.J. Hackett made one of his first bungy jumps from the top of the Eiffel Tower, using a special cord he had helped develop. Upon reaching the ground, Hackett was immediately arrested by the Paris police.[20]
On 14 July 1995, Bastille Day, French synthesiser musician Jean Michel Jarre performed Concert For Tolerance at the tower in aid of UNESCO. The free concert was attended by an estimated 1.5 million people, filling the Champ de Mars. The concert featured lighting and projection effects on the tower, and a huge firework display throughout. Exactly three years later, he returned to the same spot for a more dance music orientated show, Electronic Night.
On New Year's Eve 1999, the Eiffel Tower played host to Paris' Millennium Celebration. Fireworks exploded from the whole length of the tower in a spectacular display. An exhibition above a cafeteria on the first floor commemorates this event.
In 2000, flashing lights and four high-power searchlights were installed on the tower. Since then the light show has become a nightly event. The searchlights on top of the tower make it a beacon in Paris' night sky.
The tower received its 200,000,000th guest of all-time in 2002.[21][22]
At 19:20 on 22 July 2003, a fire occurred at the top of the tower in the broadcasting equipment room. The entire tower was evacuated; the fire was extinguished after 40 minutes, and there were no reports of injuries.
Since 2004, the Eiffel Tower has hosted an ice skating rink on the first floor during the winter period.
At the start of the French Presidency of the European Union in the second half of 2008, the twelve golden stars of the European Flag were mounted on the base, and whole tower bathed in blue light. In addition every hour, on the hour, 20,000 flash bulbs give the tower a sparkly appearance.[23]
Engraved names
Main article: The 72 names on the Eiffel Tower
Gustave Eiffel engraved on the tower seventy-two names of French scientists, engineers and other notable people. This engraving was painted over at the beginning of the twentieth century but restored in 1986–1987 by the Société Nouvelle d'exploitation de la Tour Eiffel, a company contracted to operate business related to the Tower.
Image copyright claims
Images of the tower have long been in the public domain; however, in 2003 SNTE (Société nouvelle d'exploitation de la tour Eiffel) installed a new lighting display on the tower. The effect was to put any night-time image of the tower and its lighting display under copyright. As a result, it was no longer legal to publish contemporary photographs of the tower at night without permission in some countries.[24][25]
The imposition of copyright has been controversial. The Director of Documentation for SNTE, Stéphane Dieu, commented in January 2005, "It is really just a way to manage commercial use of the image, so that it isn't used in ways we don't approve." However, it also potentially has the effect of prohibiting tourist photographs of the tower at night from being published[26] as well as hindering non profit and semi-commercial publication of images of the tower.
In a recent[citation needed] decision, the Court of Cassation ruled that copyright could not be claimed over images including a copyrighted building if the photograph encompassed a larger area. This seems to indicate that SNTE cannot claim copyright on photographs of Paris incorporating the lit tower.
In some jurisdictions, this claim of copyright is explicitly disallowed. For instance Irish copyright law, works "permanently situated in a public place or in premises open to the public" may be freely included in visual reproductions[27]; similar laws exist in Germany (see Panoramafreiheit).
Introduction
Named after its designer, engineer Gustave Eiffel, the Eiffel Tower is the tallest building in Paris.[1] More than 200,000,000 people have visited the tower since its construction in 1889,[2] including 6,719,200 in 2006,[3] making it the most visited paid monument in the world.[4][5] Including the 24 m (79 ft) antenna, the structure is 324 m (1,063 ft) high (since 2000), which is equivalent to about 81 levels in a conventional building.
Eiffel Tower October 2007 When the tower was completed in 1889 it was the world's tallest tower — a title it retained until 1930 when New York City's Chrysler Building (319 m — 1,047 ft tall) was completed.[6] The tower is now the fifth-tallest structure in France and the tallest structure in Paris, with the second-tallest being the Tour Montparnasse (210 m — 689 ft), although that will soon be surpassed by Tour AXA (225.11 m — 738.36 ft).
Eiffel Tower from the neighborhood.The metal structure of the Eiffel Tower weighs 7,300 tonnes while the entire structure including non-metal components is approximately 10,000 tonnes. Depending on the ambient temperature, the top of the tower may shift away from the sun by up to 18 cm (7 in) because of thermal expansion of the metal on the side facing the sun. The tower also sways 6–7 cm (2–3 in) in the wind.[3] As demonstration of the economy of design, if the 7300 tonnes of the metal structure were melted down it would fill the 125 meter square base to a depth of only 6 cm (2.36 in), assuming a density of the metal to be 7.8 tonnes per cubic meter. The tower has a mass less than the mass of the air contained in a cylinder of the same dimensions,[7] that is 324 meters high and 88.3 meters in radius. The weight of the tower is 10,100 tonnes compared to 10,265 tonnes of air.
The first and second levels are accessible by stairways and lifts. A ticket booth at the south tower base sells tickets to access the stairs which begin at that location. At the first platform the stairs continue up from the east tower and the third level summit is only accessible by lift. From the first or second platform the stairs are open for anyone to ascend or descend regardless of whether they have purchased a lift ticket or stair ticket. The actual count of stairs includes 9 steps to the ticket booth at the base, 328 steps to the first level, 340 steps to the second level and 18 steps to the lift platform on the second level. When exiting the lift at the third level there are 15 more steps to ascend to the upper observation platform. The step count is printed periodically on the side of the stairs to give an indication of progress of ascent. The majority of the ascent allows for an unhindered view of the area directly beneath and around the tower although some short stretches of the stairway are enclosed.
Maintenance of the tower includes applying 50 to 60 tonnes of paint every seven years to protect it from rust. In order to maintain a uniform appearance to an observer on the ground, three separate colors of paint are used on the tower, with the darkest on the bottom and the lightest at the top. On occasion the colour of the paint is changed; the tower is currently painted a shade of brownish-grey.[8] On the first floor there are interactive consoles hosting a poll for the colour to use for a future session of painting. The co-architects of the Eiffel Tower are Emile Nouguier, Maurice Koechlin and Stephen Sauvestre.[9]
History
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Eiffel Tower under construction in July 1888.The structure was built between 1887 and 1889 as the entrance arch for the Exposition Universelle, a World's Fair marking the centennial celebration of the French Revolution. Eiffel originally planned to build the tower in Barcelona, for the Universal Exposition of 1888, but those responsible at the Barcelona city hall thought it was a strange and expensive construction, which did not fit into the design of the city. After the refusal of the Consistory of Barcelona, Eiffel submitted his draft to those responsible for the Universal Exhibition in Paris, where he would build his tower a year later, in 1889. The tower was inaugurated on 31 March 1889, and opened on 6 May. Three hundred workers joined together 18,038 pieces of puddled iron (a very pure form of structural iron), using two and a half million rivets, in a structural design by Maurice Koechlin. The risk of accident was great, for unlike modern skyscrapers the tower is an open frame without any intermediate floors except the two platforms. However, because Eiffel took safety precautions, including the use of movable stagings, guard-rails and screens, only one man died.
Eiffel Tower Construction view: girders at the first storyThe tower was met with much criticism from the public when it was built, with many calling it an eyesore. Newspapers of the day were filled with angry letters from the arts community of Paris. One is quoted extensively in William Watson's US Government Printing Office publication of 1892 Paris Universal Exposition: Civil Engineering, Public Works, and Architecture. “And during twenty years we shall see, stretching over the entire city, still thrilling with the genius of so many centuries, we shall see stretching out like a black blot the odious shadow of the odious column built up of riveted iron plates.”[10] Signers of this letter included Jean-Louis-Ernest Meissonier, Charles Gounod, Charles Garnier, Jean-Léon Gérôme, William-Adolphe Bouguereau, and Alexandre Dumas.
Novelist Guy de Maupassant — who claimed to hate the tower — supposedly ate lunch in the Tower's restaurant every day. When asked why, he answered that it was the one place in Paris where one could not see the structure. Today, the Tower is widely considered to be a striking piece of structural art.
One of the great Hollywood movie clichés is that the view from a Parisian window always includes the tower. In reality, since zoning restrictions limit the height of most buildings in Paris to 7 stories, only a very few of the taller buildings have a clear view of the tower.
Eiffel had a permit for the tower to stand for 20 years, meaning it would have had to be dismantled in 1909, when its ownership would revert to the City of Paris. The City had planned to tear it down (part of the original contest rules for designing a tower was that it could be easily demolished) but as the tower proved valuable for communication purposes, it was allowed to remain after the expiration of the permit. The military used it to dispatch Parisian taxis to the front line during the First Battle of the Marne, and it therefore became a victory statue of that battle.
Shape of the tower
Looking up at the Eiffel Tower.At the time the tower was built many people were shocked by its daring shape. Eiffel was criticised for the design and accused of trying to create something artistic, or inartistic according to the viewer, without regard to engineering. Eiffel and his engineers, as renowned bridge builders however, understood the importance of wind forces and knew that if they were going to build the tallest structure in the world they had to be certain it would withstand the wind. In an interview reported in the newspaper Le Temps, Eiffel said:
“ Now to what phenomenon did I give primary concern in designing the Tower? It was wind resistance. Well then! I hold that the curvature of the monument's four outer edges, which is as mathematical calculation dictated it should be (...) will give a great impression of strength and beauty, for it will reveal to the eyes of the observer the boldness of the design as a whole. ”
—translated from the French newspaper Le Temps of 14 February 1887[11]
The shape of the tower was therefore determined by mathematical calculation involving wind resistance. Several theories of this mathematical calculation have been proposed over the years, the most recent is a nonlinear integral differential equation based on counterbalancing the wind pressure on any point on the tower with the tension between the construction elements at that point. That shape is exponential. A careful plot of the tower curvature however, reveals two different exponentials, the lower section having a stronger resistance to wind forces.[12][13]
Installations
Communications
The Eiffel tower and the Seine at night
The Eiffel tower illuminated in blue to celebrate the French presidency of the EU (July 2008.)Since the beginning of the 20th century, the tower has been used for radio transmission. Until the 1950s, an occasionally modified set of antenna wires ran from the summit to anchors on the Avenue de Suffren and Champ de Mars. They were connected to long-wave transmitters in small bunkers; in 1909, a permanent underground radio centre was built near the south pillar and still exists today.[citation needed] On 20 November 1913, the Paris Observatory, using the Eiffel Tower as an antenna, exchanged sustained wireless signals with the United States Naval Observatory which used an antenna in Arlington, Virginia. The object of the transmissions was to measure the difference in longitude between Paris and Washington, D.C.[14]
Restaurants
The tower has two restaurants: Altitude 95, on the first floor (95 m, 311 ft, above sea level); and the Jules Verne, an expensive gastronomical restaurant on the second floor, with a private lift. This restaurant has one star in the Michelin Red Guide. In January 2007, a new multi-Michelin star chef Alain Ducasse was brought in to run Jules Verne.[15]
Passenger Lifts
Ground to Second level
[16] [17] The original lifts to the first and second floors were provided by two companies. Both companies had to overcome many technical obstacles as neither company (or indeed any company) had experience with installing lifts climbing to such heights with large loads. The slanting tracks with changing angles further complicated the problems. The East and West lifts were supplied by the French company Roux Combaluzier Lepape, using hydraulically powered chains and rollers. Contemporary engravings of the lift cars show that the passengers were seated at this time but it is not clear whether this was conceptual. It would be unnecessary to seat passengers for a journey time of around a couple of minutes. The North and South lifts were provided by the American Otis company using car designs similar to the original installation but using an improved hydraulic and cable scheme. The French lifts had a very poor performance and were replaced with the current installations in 1897 (West Pillar) and 1899 (East Pillar) by Fives-Lille using an improved hydraulic and rope scheme. Both of the original installations operated broadly on the principle of the Fives-Lille lifts.
The Fives-Lille lifts from ground level to the first and second levels are operated by cables and pulleys driven by massive water-powered pistons. The hydraulic scheme was somewhat unusual for the time in that it included three large counterweights of 200 tonnes each sitting on top of hydraulic rams which doubled up as accumulators for the water. As the lifts ascend the inclined arc of the pillars, the angle of ascent changes. The two lift cabs are kept more or less level and indeed are level at the landings. The cab floors do take on a slight angle at times between landings.
The principle behind the lifts is similar to the operation of a block and tackle but in reverse. Two large hydraulic rams (over 1 metre diameter) with a 16 metre travel are mounted horizontally in the base of the pillar which pushes a carriage (the French word for it translates as chariot and this term will be used henceforth to distinguish it from the lift carriage) with 16 large triple sheaves mounted on it. There are 14 similar sheaves mounted staticly. Six wire ropes are rove back and forth between the sheaves such that each rope passes between the 2 sets of sheaves 7 times. The ropes then leave the final sheaves on the chariot and passes up through a series of guiding sheaves to above the second floor and then via a pair of triple sheaves back down to the lift carriage again passing guiding sheaves.
This arrangement means that the lift carriage complete with its cars and passengers travels 8 times the distance that the rams move the chariot which is the 128 metres from the ground to the second floor. The force exerted by the rams also has to be 8 times the total weight of the lift carriage, cars and passengers plus extra to cater for various losses such as friction. The hydraulic fluid was water, normally stored in the 3 accumulators complete with counterbalance weights. To make the lift ascend, water was pumped using an electrically driven pump from the accumulators to the two rams. Since the counterbalance weights provided much of the pressure required, the pump only had to provide the extra effort. For the descent, it was only necessary to allow the water to flow back to the accumulators using a control valve. The lifts were operated by an operator perched precariously underneath the lift cars. His position (with a dummy operator) can still be seen on the lifts today.
The Fives-Lille lifts were completely upgraded in 1986 to meet modern safety requirements and to make the lifts easier to operate. A new computer controlled system was installed which completely automated the operation. One of the three counterbalances was taken out of use, and the cars were replaced with a more modern and lighter structure. Most importantly, the main driving force was removed from the original water pump such that the water hydraulic system provided only a counterbalancing function. The main driving force was transferred to a 320 kW electrically driven oil hydraulic pump which drives a pair of hydraulic motors on the chariot itself thus providing the motive power. The new lift cars complete with their carriage and a full 92 passenger load weigh 22 tonnes.
Due to elasticity in the ropes and the time taken to get the cars level with the landings, each lift in normal service takes an average of 8 minutes and 50 seconds to do the round trip spending an average of 1 minute and 15 seconds at each floor. The average journey time between floors is just 1 minute.
The original Otis lifts in the North and South pillars in their turn proved inferior to the new (in 1899) French lifts and were scrapped from the south pillar in 1900 and from the north pillar in 1913 after failed attempts to re-power them with an electric motor. The north and south pillars were to remain without lifts until 1965 when increasing visitor numbers persuaded the operators to install a relatively standard and modern rope hoisted system in the north pillar using a rope hauled counterbalance weight, but hoisted by a block and tackle system to reduce its travel to one third of the lift travel. The counterbalance is clearly visible within the structure of the North pillar. This latter lift was upgraded in 1995 with new cars and computer controls.
The South tower acquired a completely new fairly standard electrically driven lift in 1983 to serve the Jules Verne restaurant. This was also supplied by Otis.
A further 4 tonne service lift was added to the south pillar in 1989 by Otis to relieve the main lifts when moving relatively small loads or even just maintenance personnel.
The east and west hydraulic (water) lift works are on display and, at least in theory, are open to the public in a small museum located in base of the East and West tower, which is somewhat hidden from public view. Because the massive mechanism requires frequent lubrication and attention, public access is often restricted. However, when open, the wait times are much less than the other, more popular, attractions. The rope mechanism of the North tower is visible to visitors as they exit from the lift.
Second to Third level
The original Hydraulic pump for the Edoux lifts.The original lift from the second to the third floor were also of a water powered hydraulic design supplied by Léon Edoux. Instead of using a separate counterbalance, the two lift cars counterbalanced each other. A pair of 81 metre long hydraulic rams were mounted on the second level reaching nearly half way up to the third level. A lift car was mounted on top of the rams. Ropes ran from the top of this car up to a sheave on the third level and back down to a second car. The result of this arrangement was that each car only travelled half the distance between the second and third levels and passengers were required to change lifts halfway walking between the cars along a narrow gangway with a very impressive and relatively unobstructed downward view. The 10 tonne cars held 65 passengers each or up to 4 tonnes.
One interesting feature of the original installation was that the hoisting rope ran through guides to retain it on windy days to prevent it flapping and becoming damaged. The guides were mechanically moved out of the way of the ascending car by the movement of the car itself. In spite of some antifreeze being added to the water that operated this system, it nevertheless had to close to the public from November to March each year.
The original spiral stairs to the third floor which were only 80 centimetres wide. Note also the small service lift in the background.The original lifts complete with their hydraulic mechanism were completely scrapped in 1982 after 97 years of service. They were replaced with two pairs of relatively standard rope hoisted cars which were able to operate all the year round. The cars operate in pairs with one providing the counterbalance for the other. Neither car can move unless both sets of doors are closed and both operators have given a start command. The commands from the cars to the hoising mechanism are by radio obviating the necessity of a control cable. The replacement installation also has the advantage that the ascent can be made without changing cars and has reduced the ascent time from 8 minutes (including change) to 1 minute and 40 seconds. This instalation also has guides for the hoisting ropes but they are electrically operated. The guide once it has moved out of the way as the car ascends automatically reverses when the car has passed to prevent the mechanism becoming snagged on the car on the downward journey in the event it has failed to completely clear the car. Unfortunately these lifts do not have the capacity to move as many people as the 3 public lower lifts and long queues to ascend to the third level are common. Most of the intermediate level structure present on the tower today was installed when the lifts were replaced and allows maintenance workers to take the lift half way.
The replacement of these lifts allowed the restructuring of the criss-cross beams in upper part of the tower and further allowed the installation of two emergency staircases. These replaced the dangerous winding stairs that were installed when the tower was constructed.
Events
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Lightning strikes the Eiffel Tower on June 3, 1902, at 9:20 P.M
The Eiffel Tower served as an advertising space for Citroën from 1925 to 1934.
On 10 September 1889, Thomas Edison visited the tower. He signed the guestbook with the following message—
“ To M Eiffel the Engineer the brave builder of so gigantic and original specimen of modern Engineering from one who has the greatest respect and admiration for all Engineers including the Great Engineer the Bon Dieu, Thomas Edison. ”
Father Theodor Wulf in 1910 took observations of radiant energy radiating at the top and bottom of the tower, discovering at the top more than was expected, and thereby detecting what are today known as cosmic rays.[18]
On 4 February 1912, Austrian tailor Franz Reichelt died after jumping 60 metres from the first deck of Eiffel tower with his home-made parachute.
In 1925, the con artist Victor Lustig "sold" the tower for scrap metal on two separate, but related occasions.
In 1930, the tower lost the title of the world's tallest structure when the Chrysler Building was completed in New York City.
From 1925 to 1934, illuminated signs for Citroën adorned three of the tower's four sides, making it the tallest advertising space in the world at the time.
Upon the Nazi occupation of Paris in 1940, the lift cables were cut by the French so that Adolf Hitler would have to climb the steps to the summit. The parts to repair them were allegedly impossible to obtain because of the war. In 1940 German soldiers had to climb to the top to hoist the swastika, but the flag was so large it blew away just a few hours later, and it was replaced by a smaller one. When visiting Paris, Hitler chose to stay on the ground. It was said that Hitler conquered France, but did not conquer the Eiffel Tower. A Frenchman scaled the tower during the German occupation to hang the French flag. In August 1944, when the Allies were nearing Paris, Hitler ordered General Dietrich von Choltitz, the military governor of Paris, to demolish the tower along with the rest of the city. Von Choltitz disobeyed the order. The lifts of the Tower were working normally within hours of the Liberation of Paris.
On 3 January 1956, a fire damaged the top of the tower.
In 1957, the present radio antenna was added to the top.
In the 1980s, an old restaurant and its supporting iron scaffolding midway up the tower was dismantled; it was purchased and reconstructed on St. Charles Avenue in New Orleans, Louisiana, by entrepreneurs John Onorio and Daniel Bonnot, originally as the Tour Eiffel Restaurant, known more recently as the Red Room. The restaurant was re-assembled from 11,000 pieces that crossed the Atlantic in a 40-foot (12 m) cargo container.
On 31 March 1984, Robert Moriarty flew a Beechcraft Bonanza through the arches of the tower.[19]
In 1985's James Bond action/adventure film A View to a Kill, Sir Roger Moore as James Bond chases May Day played by actress Grace Jones up the Eiffel Tower. She parachutes from the structure to escape. The video of the film's theme tune, performed by the group Duran Duran, also included several scenes of the band staged on the tower intercut with clips from the film. A full 20 years earlier, the Bond film Thunderball (1965) featured an establishing shot of the tower as the villainous Largo, played by Adolfo Celi, parks outside the headquarters of SPECTRE in Paris.
In 1987, A.J. Hackett made one of his first bungy jumps from the top of the Eiffel Tower, using a special cord he had helped develop. Upon reaching the ground, Hackett was immediately arrested by the Paris police.[20]
On 14 July 1995, Bastille Day, French synthesiser musician Jean Michel Jarre performed Concert For Tolerance at the tower in aid of UNESCO. The free concert was attended by an estimated 1.5 million people, filling the Champ de Mars. The concert featured lighting and projection effects on the tower, and a huge firework display throughout. Exactly three years later, he returned to the same spot for a more dance music orientated show, Electronic Night.
On New Year's Eve 1999, the Eiffel Tower played host to Paris' Millennium Celebration. Fireworks exploded from the whole length of the tower in a spectacular display. An exhibition above a cafeteria on the first floor commemorates this event.
In 2000, flashing lights and four high-power searchlights were installed on the tower. Since then the light show has become a nightly event. The searchlights on top of the tower make it a beacon in Paris' night sky.
The tower received its 200,000,000th guest of all-time in 2002.[21][22]
At 19:20 on 22 July 2003, a fire occurred at the top of the tower in the broadcasting equipment room. The entire tower was evacuated; the fire was extinguished after 40 minutes, and there were no reports of injuries.
Since 2004, the Eiffel Tower has hosted an ice skating rink on the first floor during the winter period.
At the start of the French Presidency of the European Union in the second half of 2008, the twelve golden stars of the European Flag were mounted on the base, and whole tower bathed in blue light. In addition every hour, on the hour, 20,000 flash bulbs give the tower a sparkly appearance.[23]
Engraved names
Main article: The 72 names on the Eiffel Tower
Gustave Eiffel engraved on the tower seventy-two names of French scientists, engineers and other notable people. This engraving was painted over at the beginning of the twentieth century but restored in 1986–1987 by the Société Nouvelle d'exploitation de la Tour Eiffel, a company contracted to operate business related to the Tower.
Image copyright claims
Images of the tower have long been in the public domain; however, in 2003 SNTE (Société nouvelle d'exploitation de la tour Eiffel) installed a new lighting display on the tower. The effect was to put any night-time image of the tower and its lighting display under copyright. As a result, it was no longer legal to publish contemporary photographs of the tower at night without permission in some countries.[24][25]
The imposition of copyright has been controversial. The Director of Documentation for SNTE, Stéphane Dieu, commented in January 2005, "It is really just a way to manage commercial use of the image, so that it isn't used in ways we don't approve." However, it also potentially has the effect of prohibiting tourist photographs of the tower at night from being published[26] as well as hindering non profit and semi-commercial publication of images of the tower.
In a recent[citation needed] decision, the Court of Cassation ruled that copyright could not be claimed over images including a copyrighted building if the photograph encompassed a larger area. This seems to indicate that SNTE cannot claim copyright on photographs of Paris incorporating the lit tower.
In some jurisdictions, this claim of copyright is explicitly disallowed. For instance Irish copyright law, works "permanently situated in a public place or in premises open to the public" may be freely included in visual reproductions[27]; similar laws exist in Germany (see Panoramafreiheit).
INDIA
India, officially the Republic of India (Hindi: भारत गणराज्य Bhārat Gaṇarājya; see also other Indian languages), is a country in South Asia. It is the seventh-largest country by geographical area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the south, the Arabian Sea on the west, and the Bay of Bengal on the east, India has a coastline of 7,517 kilometers (4,671 mi).[13] It is bordered by Pakistan to the west;[14] People's Republic of China (PRC), Nepal, and Bhutan to the north; and Bangladesh and Myanmar to the east. India is in the vicinity of Sri Lanka, the Maldives, and Indonesia in the Indian Ocean.
Home to the Indus Valley Civilization and a region of historic trade routes and vast empires, the Indian subcontinent was identified with its commercial and cultural wealth for much of its long history.[15] Four major world religions, Hinduism, Buddhism, Jainism and Sikhism originated there, while Zoroastrianism, Judaism, Christianity and Islam arrived in the first millennium CE and shaped the region's diverse culture. Gradually annexed by the British East India Company from the early eighteenth century and colonised by the United Kingdom from the mid-nineteenth century, India became an independent nation in 1947 after a struggle for independence that was marked by widespread nonviolent resistance.
India is a republic consisting of 28 states and seven union territories with a parliamentary system of democracy. It has the world's twelfth largest economy at market exchange rates and the fourth largest in purchasing power. Economic reforms since 1991 have transformed it into one of the fastest growing economies;[16] however, it still suffers from high levels of poverty,[17] illiteracy, and malnutrition. A pluralistic, multilingual, and multiethnic society, India is also home to a diversity of wildlife in a variety of protected habitats.
Etymology
Main article: Names of India
The name India (pronounced /ˈɪndiə/) is derived from Indus, which is derived from the Old Persian word Hindu, from Sanskrit Sindhu, the historic local appellation for the Indus River.[18] The ancient Greeks referred to the Indians as Indoi (Ινδοί), the people of the Indus.[19] The Constitution of India and common usage in various Indian languages also recognise Bharat (hi-Bharat.ogg pronunciation (help·info), /bʰɑːrət̪/) as an official name of equal status.[20] Hindustan (Hindustan.ogg /hin̪d̪ust̪ɑːn/ ), which is the Persian word for “Land of the Hindus” and historically referred to northern India, is also occasionally used as a synonym for all of India.[21]
History
Main articles: History of India and History of the Republic of India
Stone Age rock shelters with paintings at the Bhimbetka rock shelters in Madhya Pradesh are the earliest known traces of human life in India. The first known permanent settlements appeared over 9,000 years ago and gradually developed into the Indus Valley Civilisation,[22] dating back to 3300 BCE in western India. It was followed by the Vedic period, which laid the foundations of Hinduism and other cultural aspects of early Indian society, and ended in the 500s BCE. From around 550 BCE, many independent kingdoms and republics known as the Mahajanapadas were established across the country.[23]
Paintings at the Ajanta Caves in Aurangabad, Maharashtra, sixth century
In the third century BCE, most of South Asia was united into the Maurya Empire by Chandragupta Maurya and flourished under Ashoka the Great.[24] From the third century CE, the Gupta dynasty oversaw the period referred to as ancient "India's Golden Age."[25][26] Empires in Southern India included those of the Chalukyas, the Cholas and the Vijayanagara Empire. Science, engineering, art, literature, astronomy, and philosophy flourished under the patronage of these kings.
Following invasions from Central Asia between the 10th and 12th centuries, much of North India came under the rule of the Delhi Sultanate and later the Mughal Empire. Under the rule of Akbar the Great, India enjoyed much cultural and economic progress as well as religious harmony.[27][28] Mughal emperors gradually expanded their empires to cover large parts of the subcontinent. However, in North-Eastern India, the dominant power was the Ahom kingdom of Assam, among the few kingdoms to have resisted Mughal subjugation. The first major threat to Mughal imperial power came from a Hindu state known as the Maratha confederacy, that dominated much of India in the mid-18th century.[29]
From the 16th century, European powers such as Portugal, the Netherlands, France, and the United Kingdom established trading posts and later took advantage of internal conflicts to establish colonies in the country. By 1856, most of India was under the control of the British East India Company.[30] A year later, a nationwide insurrection of rebelling military units and kingdoms, known as India's First War of Independence or the Sepoy Mutiny, seriously challenged the Company's control but eventually failed. As a result of the instability, India was brought under the direct rule of the British Crown.
Mahatma Gandhi (right) with Jawaharlal Nehru, 1937. Nehru would go on to become India's first prime minister in 1947.
In the 20th century, a nationwide struggle for independence was launched by the Indian National Congress and other political organisations. Indian leader Mahatma Gandhi led millions of people in national campaigns of non-violent civil disobedience.[31] On 15 August 1947, India gained independence from British rule, but at the same time Muslim-majority areas were partitioned to form a separate state of Pakistan.[32] On 26 January 1950, India became a republic and a new constitution came into effect.[9]
Since independence, India has faced challenges from religious violence, casteism, naxalism, terrorism and regional separatist insurgencies, especially in Jammu and Kashmir and Northeast India. Since the 1990s terrorist attacks have affected many Indian cities. India has unresolved territorial disputes with P. R. China, which in 1962 escalated into the Sino-Indian War; and with Pakistan, which resulted in wars in 1947, 1965, 1971 and 1999. India is a founding member of the United Nations (as British India) and the Non-Aligned Movement. In 1974, India conducted an underground nuclear test[33] and five more tests in 1998, making India a nuclear state.[33] Beginning in 1991, significant economic reforms[34] have transformed India into one of the fastest-growing economies in the world, increasing its global clout.[16]
Government
Main article: Government of India
Flag of India National Symbols of India[35]
Flag Tricolour
Emblem Sarnath Lion Capital
Anthem Jana Gana Mana
Song Vande Mataram
Animal Royal Bengal Tiger
Bird Indian Peafowl
Flower Lotus
Tree Banyan
Fruit Mango
Sport Field hockey
Calendar Saka
The Constitution of India, the longest and the most exhaustive constitution of any independent nation in the world, came into force on 26 January, 1950.[36] The preamble of the constitution defines India as a sovereign, socialist, secular, democratic republic.[37] India has a bicameral parliament operating under a Westminster-style parliamentary system. Its form of government was traditionally described as being 'quasi-federal' with a strong centre and weaker states,[38] but it has grown increasingly federal since the late 1990s as a result of political, economic and social changes.[39]
The President of India is the head of state[40] elected indirectly by an electoral college[41] for a five-year term.[42][43] The Prime Minister is the head of government and exercises most executive powers.[40] Appointed by the President,[44] the Prime Minister is by convention supported by the party or political alliance holding the majority of seats in the lower house of Parliament.[40] The executive branch consists of the President, Vice-President, and the Council of Ministers (the Cabinet being its executive committee) headed by the Prime Minister. Any minister holding a portfolio must be a member of either house of parliament. In the Indian parliamentary system, the executive is subordinate to the legislature, with the Prime Minister and his Council being directly responsible to the lower house of the Parliament.[45]
The Legislature of India is the bicameral Parliament, which consists of the upper house called the Rajya Sabha (Council of States) and the lower house called the Lok Sabha (House of People).[46] The Rajya Sabha, a permanent body, has 245 members serving staggered six year terms.[47] Most are elected indirectly by the state and territorial legislatures in proportion to the state's population.[47] 543 of the Lok Sabha's 545 members are directly elected by popular vote to represent individual constituencies for five year terms.[47] The other two members are nominated by the President from the Anglo-Indian community if the President is of the opinion that the community is not adequately represented.[47]
India has a unitary three-tier judiciary, consisting of the Supreme Court, headed by the Chief Justice of India, twenty-one High Courts, and a large number of trial courts.[48] The Supreme Court has original jurisdiction over cases involving fundamental rights and over disputes between states and the Centre, and appellate jurisdiction over the High Courts.[49] It is judicially independent,[48] and has the power to declare the law and to strike down Union or State laws which contravene the Constitution.[50] The role as the ultimate interpreter of the Constitution is one of the most important functions of the Supreme Court.[51]
Political and administrative divisions
Main article: Administrative divisions of India
India consists of twenty-eight states and seven Union Territories.[52] All states, and the two union territories of Puducherry and the National Capital Territory of Delhi, have elected legislatures and governments patterened on the Westminister model. The other five union territories have centrally appointed administrators and hence are under direct rule of the President. In 1956, under the States Reorganisation Act, states were formed on a linguistic basis.[53] Since then, this structure has remained largely unchanged. Each state or union territory is further divided into 610 districts for basic governance and administration.[54] The districts in turn are further divided into tehsils and eventually into villages.
Administrative divisions of India, including 28 states and 7 union territories.
States:
1. Andhra Pradesh
2. Arunachal Pradesh
3. Assam
4. Bihar
5. Chhattisgarh
6. Goa
7. Gujarat
8. Haryana
9. Himachal Pradesh
10. Jammu and Kashmir
11. Jharkhand
12. Karnataka
13. Kerala
14. Madhya Pradesh
15. Maharashtra
16. Manipur
17. Meghalaya
18. Mizoram
19. Nagaland
20. Orissa
21. Punjab
22. Rajasthan
23. Sikkim
24. Tamil Nadu
25. Tripura
26. Uttar Pradesh
27. Uttarakhand
28. West Bengal
Union Territories:
1. Andaman and Nicobar Islands
2. Chandigarh
3. Dadra and Nagar Haveli
4. Daman and Diu
5. Lakshadweep
6. National Capital Territory of Delhi
7. Puducherry
Politics
Main article: Politics of India
The North Block, in New Delhi, houses key government offices.
India is the most populous democracy in the world.[55][56] For most of the years since independence, the federal government has been led by the Indian National Congress (INC).[52] Politics in the states have been dominated by several national parties including the INC, the Bharatiya Janata Party (BJP), the Communist Party of India (Marxist) (CPI(M)) and various regional parties. From 1950 to 1990, barring two brief periods, the INC enjoyed a parliamentary majority. The INC was out of power between 1977 and 1980, when the Janata Party won the election owing to public discontent with the state of emergency declared by the then Prime Minister Indira Gandhi. In 1989, a Janata Dal-led National Front coalition in alliance with the Left Front coalition won the elections but managed to stay in power for only two years.[57] As the 1991 elections gave no political party a majority, the INC formed a minority government under Prime Minister P.V. Narasimha Rao and was able to complete its five-year term.[58]
The years 1996–1998 were a period of turmoil in the federal government with several short-lived alliances holding sway. The BJP formed a government briefly in 1996, followed by the United Front coalition that excluded both the BJP and the INC. In 1998, the BJP formed the National Democratic Alliance (NDA) with several other parties and became the first non-Congress government to complete a full five-year term.[59] In the 2004 Indian elections, the INC won the largest number of Lok Sabha seats and formed a government with a coalition called the United Progressive Alliance (UPA), supported by various Left-leaning parties and members opposed to the BJP.[60]
Foreign relations and military
Main articles: Foreign relations of India and Indian Armed Forces
The Sukhoi-30 MKI is the Indian Air Force's prime air superiority fighter and the most advanced version of the Su-27 series.[61]
Since its independence in 1947, India has maintained cordial relationships with most nations. It took a leading role in the 1950s by advocating the independence of European colonies in Africa and Asia.[62] India was involved in two brief military interventions in neighboring countries – Indian Peace Keeping Force in Sri Lanka and Operation Cactus in Maldives. India is a member of the Commonwealth of Nations and a founding member of the Non-Aligned Movement.[63] After the Sino-Indian War and the Indo-Pakistani War of 1965, India's relationship with the Soviet Union warmed and continued to remain so until the end of the Cold War. India has fought two wars with Pakistan over the Kashmir dispute. A third war between India and Pakistan in 1971 resulted in the creation of Bangladesh (then East Pakistan).[64] Additional skirmishes have taken place between the two nations over the Siachen Glacier. In 1999, India and Pakistan fought an undeclared war over Kargil.
India and Russia share an extensive economic, defense and technological relationship.[65] Shown here is PM Manmohan Singh with President Dmitry Medvedev at the 34th G8 Summit.
In recent years, India has played an influential role in the SAARC, and the WTO.[66] India has provided as many as 55,000 Indian military and police personnel to serve in thirty-five UN peace keeping operations across four continents.[67] Despite criticism and military sanctions, India has consistently refused to sign the CTBT and the NPT, preferring instead to maintain sovereignty over its nuclear program. Recent overtures by the Indian government have strengthened relations with the United States, China and Pakistan. In the economic sphere, India has close relationships with other developing nations in South America, Asia and Africa.
India maintains the third-largest military force in the world, which consists of the Indian Army, Navy, Air Force[9] and auxiliary forces such as the Paramilitary Forces, the Coast Guard, and the Strategic Forces Command. The President of India is the supreme commander of the Indian Armed Forces. India maintains close defence cooperation with Russia, Israel and France, who are the chief suppliers of arms. The Defence Research and Development Organisation (DRDO) oversees indigenous development of sophisticated arms and military equipment, including ballistic missiles, fighter aircraft and main battle tanks, to reduce India's dependence on foreign imports. India became a nuclear power in 1974 after conducting an initial nuclear test, Operation Smiling Buddha and further underground testing in 1998. India maintains a "no first use" nuclear policy.[68] On 10 October, 2008 Indo-US civilian nuclear agreement was signed, prior to which India received IAEA and NSG waivers, ending restrictions on nuclear technology commerce with which India became de facto sixth nuclear power in world.[69]
Geography
Main article: Geography of India
See also: Geological history of India and Climate of India
Topographic map of India.
India, the major portion of the Indian subcontinent, sits atop the Indian tectonic plate, a minor plate within the Indo-Australian Plate.[70]
India's defining geological processes commenced seventy-five million years ago, when the Indian subcontinent, then part of the southern supercontinent Gondwana, began a northeastwards drift—lasting fifty million years—across the then unformed Indian Ocean.[70] The subcontinent's subsequent collision with the Eurasian Plate and subduction under it, gave rise to the Himalayas, the planet's highest mountains, which now abut India in the north and the north-east.[70] In the former seabed immediately south of the emerging Himalayas, plate movement created a vast trough, which, having gradually been filled with river-borne sediment,[71] now forms the Indo-Gangetic Plain.[72] To the west of this plain, and cut off from it by the Aravalli Range, lies the Thar Desert.[73] The original Indian plate now survives as peninsular India, the oldest and geologically most stable part of India, and extending as far north as the Satpura and Vindhya ranges in central India. These parallel ranges run from the Arabian Sea coast in Gujarat in the west to the coal-rich Chota Nagpur Plateau in Jharkhand in the east.[74] To their south, the remaining peninsular landmass, the Deccan Plateau, is flanked on the left and right by the coastal ranges, Western Ghats and Eastern Ghats respectively;[75] the plateau contains the oldest rock formations in India, some over one billion years old. Constituted in such fashion, India lies to the north of the equator between 6°44' and 35°30' north latitude[76] and 68°7' and 97°25' east longitude.[77]
India's coast is 7,517 kilometers (4,671 mi) long; of this distance, 5,423 kilometers (3,370 mi) belong to peninsular India, and 2,094 kilometers (1,301 mi) to the Andaman, Nicobar, and Lakshadweep Islands.[13] According to the Indian naval hydrographic charts, the mainland coast consists of the following: 43% sandy beaches, 11% rocky coast including cliffs, and 46% mudflats or marshy coast.[13]
Tso Kiagar Lake at Ladakh on the Himalayas
Major Himalayan-origin rivers that substantially flow through India include the Ganges and the Brahmaputra, both of which drain into the Bay of Bengal.[78] Important tributaries of the Ganges include the Yamuna and the Kosi, whose extremely low gradient causes disastrous floods every year. Major peninsular rivers whose steeper gradients prevent their waters from flooding include the Godavari, the Mahanadi, the Kaveri, and the Krishna, which also drain into the Bay of Bengal;[79] and the Narmada and the Tapti, which drain into the Arabian Sea.[80] Among notable coastal features of India are the marshy Rann of Kutch in western India, and the alluvial Sundarbans delta, which India shares with Bangladesh.[81] India has two archipelagos: the Lakshadweep, coral atolls off India's south-western coast; and the Andaman and Nicobar Islands, a volcanic chain in the Andaman Sea.[82]
India's climate is strongly influenced by the Himalayas and the Thar Desert, both of which drive the monsoons.[83] The Himalayas prevent cold Central Asian katabatic winds from blowing in, keeping the bulk of the Indian subcontinent warmer than most locations at similar latitudes.[84][85] The Thar Desert plays a crucial role in attracting the moisture-laden southwest summer monsoon winds that, between June and October, provide the majority of India's rainfall.[83] Four major climatic groupings predominate in India: tropical wet, tropical dry, subtropical humid, and montane.[86]
Flora and fauna
Main articles: Flora of India and Fauna of India
An artist's impression of the Himalayan mountain quail, one of three bird species of India that went extinct in the 20th century.
India, which lies within the Indomalaya ecozone, displays significant biodiversity. One of eighteen megadiverse countries, it is home to 7.6% of all mammalian, 12.6% of all avian, 6.2% of all reptilian, 4.4% of all amphibian, 11.7% of all fish, and 6.0% of all flowering plant species.[87] Many ecoregions, such as the shola forests, exhibit extremely high rates of endemism; overall, 33% of Indian plant species are endemic.[88][89] India's forest cover ranges from the tropical rainforest of the Andaman Islands, Western Ghats, and North-East India to the coniferous forest of the Himalaya. Between these extremes lie the sal-dominated moist deciduous forest of eastern India; the teak-dominated dry deciduous forest of central and southern India; and the babul-dominated thorn forest of the central Deccan and western Gangetic plain.[90] Important Indian trees include the medicinal neem, widely used in rural Indian herbal remedies. The pipal fig tree, shown on the seals of Mohenjo-daro, shaded Gautama Buddha as he sought enlightenment.
Many Indian species are descendants of taxa originating in Gondwana, to which India originally belonged. Peninsular India's subsequent movement towards, and collision with, the Laurasian landmass set off a mass exchange of species. However, volcanism and climatic changes 20 million years ago caused the extinction of many endemic Indian forms.[91] Soon thereafter, mammals entered India from Asia through two zoogeographical passes on either side of the emerging Himalaya.[90] Consequently, among Indian species, only 12.6% of mammals and 4.5% of birds are endemic, contrasting with 45.8% of reptiles and 55.8% of amphibians.[87] Notable endemics are the Nilgiri leaf monkey and the brown and carmine Beddome's toad of the Western Ghats. India contains 172, or 2.9%, of IUCN-designated threatened species.[92] These include the Asiatic Lion, the Bengal Tiger, and the Indian white-rumped vulture, which suffered a near-extinction from ingesting the carrion of diclofenac-treated cattle.
In recent decades, human encroachment has posed a threat to India's wildlife; in response, the system of national parks and protected areas, first established in 1935, was substantially expanded. In 1972, India enacted the Wildlife Protection Act[93] and Project Tiger to safeguard crucial habitat; in addition, the Forest Conservation Act[94] was enacted in 1980. Along with more than five hundred wildlife sanctuaries, India hosts thirteen biosphere reserves,[95] four of which are part of the World Network of Biosphere Reserves; twenty-five wetlands are registered under the Ramsar Convention.[96]
Economy
Main article: Economy of India
See also: Economic history of India
The Bombay Stock Exchange, in Mumbai, is Asia's oldest and India's largest stock exchange.
For an entire generation from the 1950s until the 1980s, India followed socialist-inspired policies. The economy was shackled by extensive regulation, protectionism, and public ownership, leading to pervasive corruption and slow growth.[97][98][99][100] Since 1991, the nation has moved towards a market-based system.[98][99] The policy change in 1991 came after an acute balance of payments crisis, and the emphasis since then has been to use foreign trade and foreign investment as integral parts of India's economy.[101]
With an average annual GDP growth rate of 5.8% for the past two decades, the economy is among the fastest growing in the world.[102] It has the world's second largest labour force, with 516.3 million people. In terms of output, the agricultural sector accounts for 28% of GDP; the service and industrial sectors make up 54% and 18% respectively. Major agricultural products include rice, wheat, oilseed, cotton, jute, tea, sugarcane, potatoes; cattle, water buffalo, sheep, goats, poultry; fish.[52] Major industries include textiles, chemicals, food processing, steel, transport equipment, cement, mining, petroleum, machinery, software.[52] India's trade has reached a relatively moderate share 24% of GDP in 2006, up from 6% in 1985.[98] India's share of world trade has reached 1%. Major exports include petroleum products, textile goods, gems and jewelry, software, engineering goods, chemicals, leather manufactures.[52] Major imports include crude oil, machinery, gems, fertilizer, chemicals.[52]
India's GDP is US$1.089 trillion, which makes it the twelfth-largest economy in the world[103] or fourth largest by purchasing power adjusted exchange rates. India's nominal per capita income US$977 is ranked 128th in the world. In the late 2000s, India's economic growth has averaged 7½% a year, which will double the average income in a decade.[98]
India remains one of the poorest countries in the world. The percentage of people living below the new international poverty line $1.25 a day (PPP, in nominal terms Rs 21.6 a day in urban areas and Rs 14.3 in rural areas in 2005) decreased from 60% in 1981 to 42% in 2005.[104] 85.7% of the population was living on less than $2.50 (PPP) a day in 2005, compared with 80.5% for Sub-Saharan Africa.[105] Even though India has avoided famines in recent decades, half of children are underweight, one of the highest rates in the world and nearly double the rate of Sub-Saharan Africa.[106]
Ongoing reforms are watched closely as India could become potentially important for the global economy. A Goldman Sachs report predicts that "from 2007 to 2020, India’s GDP per capita will quadruple," and that the Indian economy will surpass the United States by 2043, but India "will remain a low-income country for several decades, with per capita incomes well below its other BRIC peers. But if it can fulfill its growth potential, it can become a motor for the world economy, and a key contributor to generating spending growth.".[100] Although the Indian economy has grown steadily over the last two decades; its growth has been uneven when comparing different social groups, economic groups, geographic regions, and rural and urban areas.[107] World Bank suggests that the most important priorities are public sector reform, infrastructure, agricultural and rural development, removal of labor regulations, reforms in lagging states, and HIV/AIDS.[108]
Demographics
Main article: Demographics of India
See also: Religion in India, Languages of India, and Ethnic groups of South Asia
Population density map of India.
With an estimated population of 1.17 billion,[9] representing 17% of the world population,[109] India is the world's second most populous country. The last 50 years have seen a rapid increase in population due to medical advances and massive increase in agricultural productivity[110] made by the green revolution.[111] Almost 70% of Indians reside in rural areas, although in recent decades migration to larger cities has led to a dramatic increase in the country's urban population. India's largest cities are Mumbai (formerly Bombay), Delhi, Kolkata (formerly Calcutta), Chennai (formerly Madras), Bengaluru (formerly Bangalore), Hyderabad and Ahmedabad.[52]
India is the most culturally, linguistically and genetically diverse geographical entity after the African continent.[52] India is home to two major linguistic families: Indo-Aryan (spoken by about 74% of the population) and Dravidian (spoken by about 24%). Other languages spoken in India come from the Austro-Asiatic and Tibeto-Burman linguistic families. Hindi, with the largest number of speakers,[112] is the official language of the union.[113] English, which is extensively used in business and administration, has the status of a 'subsidiary official language;'[114] it is also important in education, especially as a medium of higher education. In addition, every state and union territory has its own official languages, and the constitution also recognises in particular 21 other languages that are either abundantly spoken or have classical status. While Sanskrit and Tamil have been studied as classical languages for many years,[115] the Government of India, using its own criteria, has also accorded classical language status to Kannada and Telugu.[116] The number of dialects in India is as high as 1,652.[117]
Over 800 million Indians (80.5%) are Hindu. Other religious groups include Muslims (13.4%), Christians (2.3%), Sikhs (1.9%), Buddhists (0.8%), Jains (0.4%), Jews, Zoroastrians, Bahá'ís and others.[118] Tribals constitute 8.1% of the population.[119] India has the third-highest Muslim population in the world and has the highest population of Muslims for a non-Muslim majority country.
India's literacy rate is 64.8% (53.7% for females and 75.3% for males).[9] The state of Kerala has the highest literacy rate (91%);[120] Bihar has the lowest (47%).[121] The national human sex ratio is 944 females per 1,000 males. India's median age is 24.9, and the population growth rate of 1.38% per annum; there are 22.01 births per 1,000 people per year.[9]
Cities by population Rank Core City State Population Rank Core City State Population
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Mumbai
Mumbai
Delhi
Delhi
1 Mumbai Maharashtra 13,922,125 11 Jaipur Rajasthan 2,997,114
2 Delhi Delhi 12,259,230 12 Lucknow Uttar Pradesh 2,621,063
3 Chennai Tamil Nadu 6,590,267 13 Nagpur Maharashtra 2,359,331
4 Kolkata West Bengal 5,080,519 14 Patna Bihar 1,814,012
5 Bengaluru Karnataka 5,310,318 15 Indore Madhya Pradesh 1,811,513
6 Hyderabad Andhra Pradesh 4,025,339 16 Bhopal Madhya Pradesh 1,742,375
7 Ahmedabad Gujarat 3,913,793 17 Thane Maharashtra 1,673,465
8 Pune Maharashtra 3,337,481 18 Ludhiana Punjab 1,662,325
9 Surat Gujarat 3,233,988 19 Agra Uttar Pradesh 1,638,209
10 Kanpur Uttar Pradesh 3,144,267 20 Pimpri Maharashtra 1,553,538
2009 estimation[122]
Culture
Main article: Culture of India
The Taj Mahal in Agra was built by Shah Jahan as memorial to wife Mumtaz Mahal. It is a UNESCO World Heritage Site considered to be of "outstanding universal value".[123]
India's culture is marked by a high degree of syncretism[124] and cultural pluralism.[125] It has managed to preserve established traditions while absorbing new customs, traditions, and ideas from invaders and immigrants and spreading its cultural influence to other parts of Asia. Traditional Indian society is defined by relatively strict social hierarchy. The Indian caste system describes the social stratification and social restrictions in the Indian subcontinent, in which social classes are defined by thousands of endogamous hereditary groups, often termed as jātis or castes.
Traditional Indian family values are highly respected, and multi-generational patriarchal joint families have been the norm, although nuclear family are becoming common in urban areas.[97] An overwhelming majority of Indians have their marriages arranged by their parents and other respected family-members, with the consent of the bride and groom.[126] The marriage is thought to be for life,[126] and the divorce rate is extremely low.[127] Child marriage is still a common practice, with half of women in India marry before the legal age of 18.[128][129]
Indian cuisine is characterized by a wide variety of regional styles and sophisticated use of herbs and spices. The staple foods in the region are rice (especially in the south and the east) and wheat (predominantly in the north).[130] Spices originally native to the Indian subcontinent that are now consumed world wide include black pepper; in contrast, hot chili peppers, popular across India, were introduced by the Portuguese.[131]
Traditional Indian dress varies across the regions in its colours and styles and depends on various factors, including climate. Popular styles of dress include draped garments such as sari for women and dhoti or lungi for men; in addition, stitched clothes such as salwar kameez for women and kurta-pyjama and European-style trousers and shirts for men, are also popular.
Many Indian festivals are religious in origin, although several are celebrated irrespective of caste and creed. Some popular festivals are Diwali, Ganesh Chaturthi, Ugadi, Thai Pongal, Holi, Onam, Vijayadasami, Durga Puja, Eid ul-Fitr, Bakr-Id, Christmas, Buddha Jayanti and Vaisakhi.[132] India has three national holidays. Other sets of holidays, varying between nine and twelve, are officially observed in individual states. Religious practices are an integral part of everyday life and are a very public affair.
Indian architecture is one area that represents the diversity of Indian culture. Much of it, including notable monuments such as the Taj Mahal and other examples of Mughal architecture and South Indian architecture, comprises a blend of ancient and varied local traditions from several parts of the country and abroad. Vernacular architecture also displays notable regional variation.
Indian music covers a wide range of traditions and regional styles. Classical music largely encompasses the two genres – North Indian Hindustani, South Indian Carnatic traditions and their various offshoots in the form of regional folk music. Regionalised forms of popular music include filmi and folk music; the syncretic tradition of the bauls is a well-known form of the latter.
A prayer flag above Tanze Monastery in the Kurgiakh Valley. The wind is believed to propagate the prayers printed on tissue.
Indian dance too has diverse folk and classical forms. Among the well-known folk dances are the bhangra of the Punjab, the bihu of Assam, the chhau of West Bengal, Jharkhand and sambalpuri of Orissa and the ghoomar of Rajasthan. Eight dance forms, many with narrative forms and mythological elements, have been accorded classical dance status by India's National Academy of Music, Dance, and Drama. These are: bharatanatyam of the state of Tamil Nadu, kathak of Uttar Pradesh, kathakali and mohiniyattam of Kerala, kuchipudi of Andhra Pradesh, manipuri of Manipur, odissi of Orissa and the sattriya of Assam.[133]
Theatre in India often incorporates music, dance, and improvised or written dialogue.[134] Often based on Hindu mythology, but also borrowing from medieval romances, and news of social and political events, Indian theatre includes the bhavai of state of Gujarat, the jatra of West Bengal, the nautanki and ramlila of North India, the tamasha of Maharashtra, the burrakatha of Andhra Pradesh, the terukkuttu of Tamil Nadu, and the yakshagana of Karnataka.[135]
The Indian film industry is the largest in the world.[136] Bollywood, based in Mumbai, makes commercial Hindi films and is the most prolific film industry in the world.[137] Established traditions also exist in Bengali, Kannada, Malayalam, Marathi, Tamil, and Telugu language cinemas.[138]
The earliest works of Indian literature were transmitted orally and only later written down.[139] These included works of Sanskrit literature – such as the early Vedas, the epics Mahābhārata and Ramayana, the drama Abhijñānaśākuntalam (The Recognition of Śakuntalā), and poetry such as the Mahākāvya[140] – and the Tamil language Sangam literature.[141] Among Indian writers of the modern era active in Indian languages or English, Rabindranath Tagore won the Nobel Prize in 1913.
Sports
Main article: Sports of India
A 2008 Indian Premier League Twenty20 cricket match being played between the Chennai Super Kings and Kolkata Knight Riders
India's official national sport is field hockey, administered by the Indian Hockey Federation. The Indian field hockey team won the 1975 Men's Hockey World Cup and 8 gold, 1 silver and 2 bronze medals at the Olympic games. However, cricket is the most popular sport; the India national cricket team won the 1983 Cricket World Cup and the 2007 ICC World Twenty20, and shared the 2002 ICC Champions Trophy with Sri Lanka. Cricket in India is administered by the Board of Control for Cricket in India, and domestic competitions include the Ranji Trophy, the Duleep Trophy, the Deodhar Trophy, the Irani Trophy and the Challenger Series. In addition Indian cricket league and Indian premier league organize Twenty20 competitions.
Tennis has become increasingly popular, owing to the victories of the India Davis Cup team. Association football is also a popular sport in northeast India, West Bengal, Goa and Kerala.[142] The Indian national football team has won the South Asian Football Federation Cup several times. Chess, commonly held to have originated in India, is also gaining popularity with the rise in the number of Indian Grandmasters.[143] Traditional sports include kabaddi, kho kho, and gilli-danda, which are played nationwide. India is also home to the ancient martial arts, Kalarippayattu and Varma Kalai.
The Rajiv Gandhi Khel Ratna and the Arjuna Award are India's highest awards for achievements in sports, while the Dronacharya Award is awarded for excellence in coaching. India hosted or co-hosted the 1951 and the 1982 Asian Games, the 1987 and 1996 Cricket World Cup. It is also scheduled to host the 2010 Commonwealth Games and the 2011 Cricket World Cup.
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