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Japan Standard Time

Japan Standard Time

Japan Standard Time (日本標準時 or 中央標準時) is the standard timezone in Japan that is 9 hours ahead of UTC; i.e. when it is midnight (00:00) in UTC, it is 9 am (09:00) in Japan Standard Time. Short: UTC+9. Before Meiji Era, each local region had been using a timezone in which noon was set to when the sun is exactly at south. As modern transportation like trains were adopted, this practice started to cause confusion. For example, there is a difference of about 5 degrees in terms of longitude between Tokyo and Osaka and because of this, a train that departed Tokyo would arrive at Osaka at 20 minutes ahead of the time in Tokyo. In 1886 (Meiji 19), a chokurei (Imperial Ordinance) was issued in response to this, which states: 明治十九年勅令第五十一号（本初子午線経度計算方及標準時ノ件）
（明治十九年七月十三日勅令第五十一号）
- 英国グリニツチ天文台子午儀ノ中心ヲ経過スル子午線ヲ以テ経度ノ本初子午線トス
- 経度ハ本初子午線ヨリ起算シ東西各百八十度ニ至リ東経ヲ正トシ西経ヲ負トス
- 明治二十一年一月一日ヨリ東経百三十五度ノ子午線ノ時ヲ以テ本邦一般ノ標準時ト定ム Imperial OrdinanceAccording to this, the standard time (標準時) was set 9 hours ahead of GMT (UTC was not established yet.) In the ordinance, the first clause mentions about GMT, the second defines east longitude and west longitude and the third says the standard timezone would be in effect from 1888. Coincidentally, a city of Akashi in Hyogo prefecture is located exactly on 135 degrees east longitude and the city subsequently has become known as Tokino machi (town of time). With annexation of Taiwan in 1895, Western Standard Time (西部標準時) was defined with 120° longitude, and the previous Standard Time was renamed to Central Standard Time (中央標準時). (See the picture on the right.) Western Standard Time was used in Taiwan and some part of Okinawa, until 1937. Japan Standard Time is the same as Korea Standard Time.

References

Category:Time zones ja:日本標準時

TimeZone

TimeZone is an Internet forum for discussion of watches and horology. It is the oldest and largest of its kind online.

External links

- [http://www.timezone.com TimeZone website] Category:Internet forums

UTC

:For alternate uses of UTC see UTC (disambiguation) Coordinated Universal Time or UTC, also sometimes referred to as "Zulu time" or Z, is an atomic realization of Universal Time (UT) or Greenwich Mean Time, the astronomical basis for civil time. Time zones around the world are expressed as positive and negative offsets from UT. UTC differs by an integral number of seconds from International Atomic Time (TAI), as measured by atomic clocks and a fractional number of seconds from UT. UTC is a hybrid time scale: the rate of UTC is based on atomic frequency standards but the epoch of UTC is synchronized to remain close to astronomical UT. The Earth's rotation is very slowly decelerating (due to braking action of the tides), hence the mean solar day has increased since TAI was introduced on 1 January 1958 (under another name). For this reason, UT is 'slower' than TAI. As of 1 January 1999, TAI was ahead of UTC by 32 seconds, consisting of a 10-second offset introduced on 1 January 1972 to account for all variations between 1958 and 1971, plus an additional 22 leap seconds introduced between 1972 and 1998. UTC is maintained within 0.9 s of UT1 (UT1 is one of three precise definitions of UT); leap seconds are added (or, theoretically, subtracted) at the end of any UTC month as necessary. The primary dates for leap second adjustments are at the end of the day on June 30 and December 31. The secondary dates, which to date have been unused, are March 31 and September 30. To date, all such adjustments – the first in 1972 – have been positive and applied on dates June 30 or December 31, where an additive leap second is designated as 23:59:60. The announcement of leap seconds is made by the International Earth Rotation and Reference Systems Service (IERS), based on precise astronomical forecasts of the Earth's rotation. Historically, one leap second has been required every one to two years. However a leap second has not been required since 1998, as the deceleration of the Earth's rotation slowed temporarily in the past seven years. The IERS announced in July 2005 that the next leap second will be on 31 December 2005. For most practical and legal-trade purposes, the fractional difference between UTC and UT (or GMT) is inconsequentially small, and for this reason UTC is colloquially called GMT sometimes, even if this is not technically correct.

Proposal to redefine UTC and abolish leap seconds

There is a proposal to redefine UTC and abolish leap seconds, such that sundials would slowly get further out-of-sync with civil time. See Leap second for more information.

General information

"UTC" is not a true acronym; it is a variant of Universal Time, UT, and has a modifier C (for "coordinated") appended to it just like other variants of UT. It [http://www.boulder.nist.gov/timefreq/general/misc.htm#Anchor-14550 may be regarded] as a compromise between the English acronym "CUT" and the French acronym "TUC" (temps universel coordonné). It is sometimes erroneously expanded into "Universal Time Code".

Converting Universal Time
to Standard (Winter) Local Times
Hawaii-Aleutian Standard Time	UTC -10
Alaska Standard Time	UTC -9
Pacific Standard Time	UTC -8
Mountain Standard Time	UTC -7
Central Standard Time	UTC -6
Eastern Standard Time	UTC -5
Atlantic Standard Time	UTC -4
Greenwich Mean Time/Western European Time	UTC
Central European Time	UTC +1
Eastern European Time	UTC +2
Moscow Time	UTC +3
Indian Standard Time	UTC +5:30
Singapore Standard Time, Hong Kong Time, Australian Western Standard Time, Chinese Standard Time	UTC +8
Japan Standard Time, Korea Standard Time	UTC +9
Australian Central Standard Time	UTC +9:30
Australian Eastern Standard Time	UTC +10
New Zealand Standard Time	UTC +12

For more, see time zone.

International standard UTC time can only be determined to the highest precision after the fact, as atomic time is determined by the reconciliation of the observed differences between an ensemble of atomic clocks maintained by a number of national time bureaus. This is done under the auspices of the Bureau International des Poids et Mesures (International Bureau of Weights and Measures). However, local clusters of atomic clocks are sufficient for accuracy to within a few tens of nanoseconds. UTC is the time system used for many Internet and World Wide Web standards. In particular, the Network Time Protocol, designed to synchronize the clocks of many computers over the Internet (usually to that of a known accurate atomic clock), uses UTC. As indicated in the standards, it is convenient to include the UTC date too. The UT time zone is sometimes denoted by the letter Z since the equivalent nautical time zone (GMT) has been denoted by Z since about 1950, and by a "zone description" of zero hours since 1920. See Time zone history. Since the NATO phonetic alphabet and radio-amateur word for Z is "Zulu", UT is sometimes known as Zulu time.

Amateur Radio

Those who transmit on the amateur radio bands often log the time of their radio contacts in UTC, as transmissions can go worldwide on some frequencies. In the past, the FCC required all amateur radio operators in the United States of America to log their radio conversations. While maintaining a record of radio transmissions is no longer required in the USA, many American amateur radio operators still choose to maintain a log expressing the time of their transmissions in UTC, due to the world wide reach of ham radio.

References

- ITU-R Recommendation TF.460-4: Standard-frequency and time-signal emissions. International Telecommunication Union. (Annex I of this document contains the official definition of UTC.)
- Dennis D. McCarthy: "Astronomical Time". Proc. IEEE, Vol. 79, No. 7, July 1991, pp. 915-920.
- Nelson, McCarthy, et al.: "[http://www.cl.cam.ac.uk/~mgk25/time/metrologia-leapsecond.pdf The leap second: its history and possible future]" (381 KB PDF file), Metrologia, Vol. 38, pp. 509–529, 2001.
- David W. Allan, Neil Ashby, Clifford C. Hodge: The Science of Timekeeping. Hewlett Packard Application Note 1289, 1997.

External links

- [http://www.bipm.org/en/scientific/tai/time_server.html Bureau International des Poids et Mesures UTC/TAI Time Server]
- [http://www.time.gov/ The official U.S. time]
- [http://www.worldtimeserver.com/ World Time Server - any location, any time]
- [http://www.thetimenow.com/ thetimeNOW - Current time in all time zones]
- [http://aa.usno.navy.mil/faq/docs/UT.html United States Naval Observatory - What is Universal Time?]
- [http://hpiers.obspm.fr/eoppc/bul/bulc/bulletinc.dat International Earth Rotation Service Leap Second Updates]
- [http://www.qsl.net/zl1bpu/micro/CLOCK/ Make your own UTC /Local time hardware clock]
- [http://www.w3.org/TR/NOTE-datetime W3C Specification about UTC Date and Time] and IETF Internet standard RFC 3339
- [http://www.grc.nasa.gov/WWW/MAEL/ag/zulu.htm Zulu Time]
- [http://www.hko.gov.hk/gts/time/worldtime2.htm Hong Kong Time by Hong Kong Observatory] Category:Time scales als:UTC ko:협정 세계시 zh-min-nan:UTC ja:協定世界時 nb:UTC simple:Coordinated Universal Time th:เวลาพิกัดสากล

UTC

Proposal to redefine UTC and abolish leap seconds

There is a proposal to redefine UTC and abolish leap seconds, such that sundials would slowly get further out-of-sync with civil time. See Leap second for more information.

General information

Converting Universal Time
to Standard (Winter) Local Times
Hawaii-Aleutian Standard Time	UTC -10
Alaska Standard Time	UTC -9
Pacific Standard Time	UTC -8
Mountain Standard Time	UTC -7
Central Standard Time	UTC -6
Eastern Standard Time	UTC -5
Atlantic Standard Time	UTC -4
Greenwich Mean Time/Western European Time	UTC
Central European Time	UTC +1
Eastern European Time	UTC +2
Moscow Time	UTC +3
Indian Standard Time	UTC +5:30
Singapore Standard Time, Hong Kong Time, Australian Western Standard Time, Chinese Standard Time	UTC +8
Japan Standard Time, Korea Standard Time	UTC +9
Australian Central Standard Time	UTC +9:30
Australian Eastern Standard Time	UTC +10
New Zealand Standard Time	UTC +12

For more, see time zone.

Amateur Radio

References

External links

UTC9

- Japan Standard Time
- Korea Standard Time Category:Time zones

Sun

:: For the astrological significance of the Sun, see Solar system in astrology. ::"Solar" redirects here; for the superhero by that name, see Solar (comics). The Sun (or Sol) is the star at the center of our Solar system. Earth orbits the Sun, as do many other bodies, including other planets, asteroids, meteoroids, comets and dust. Its heat and light support almost all life on Earth. The Sun is a ball of plasma with a mass of about 2 kg, which is somewhat higher than that of an average star. About 74% of its mass is hydrogen, with 25% helium and the rest made up of trace quantities of heavier elements. It is thought that the Sun is about 5 billion years old, and is about halfway through its main sequence evolution, during which nuclear fusion reactions in its core fuse hydrogen into helium. In about 5 billion years time the Sun will become a white dwarf. Although it is the nearest star to Earth and has been intensively studied by scientists, many questions about the Sun remain unanswered, such as why its outer atmosphere has a temperature of over 10⁶ K when its visible surface (the photosphere) has a temperature of just 6,000 K. Looking directly at the Sun can damage the retina and one's eyesight. See below for details.

General information

See below The Sun is classified as a main sequence star, which means it is in a state of "hydrostatic balance", neither contracting nor expanding, and is generating its energy through nuclear fusion of hydrogen nuclei into helium. The Sun has a spectral class of G2V, with the G2 meaning that its color is yellow and its spectrum contains spectral lines of ionized and neutral metals as well as very weak hydrogen lines [http://www.astro.uiuc.edu/~kaler/sow/spectra.html#classes], and the V signifying that it, like most stars, is a "dwarf" star on the main sequence[http://www.physics.uq.edu.au/people/ross/phys2080/spec/analyz.htm]. The Sun has a predicted main sequence lifetime of about 10 billion years. Its current age is thought to be about 4.5 billion years, a figure which is determined using computer models of stellar evolution, and nucleocosmochronology . The Sun orbits the center of the Milky Way galaxy at a distance of about 25,000 to 28,000 light-years from the galactic centre, completing one revolution in about 226 million years. The orbital speed is 217 km/s, equivalent to one light year every 1400 years, and one AU every 8 days. The astronomical symbol for the Sun is a circle with a point at its centre (Image:Sol.gif).

Structure

Image:Sol.gif The Sun is a near-perfect sphere, with an oblateness estimated at about 9 millionths, which means the polar diameter differs from the equatorial by about 10 km. This is because the centrifugal effect of the Sun's slow rotation is 18 million times weaker than its surface gravity (at the equator). Tidal effects from the planets do not significantly affect the shape of the Sun, although the Sun itself orbits the center of mass of the solar system, which is offset from the Sun's center mostly because of the large mass of Jupiter. The mass of the Sun is so comparatively great that the center of mass of the solar system is generally within the bounds of the Sun itself. The Sun does not have a definite boundary as rocky planets do, as the density of its gases drops off following an approximately exponential relationship with distance from the centre of the Sun. Nevertheless, the Sun has well defined interior structure, described below. The Sun's radius is measured from centre to the edges of the photosphere. The solar interior is not directly observable and the Sun itself is opaque to electromagnetic radiation. However, just as the study of the waves generated by earthquakes (seismology) can be used to study the interior structure of the Earth, helioseismology, the study of sound waves that travel through the Sun's interior, has also contributed greatly to our understanding of the Sun's structure . Computer modeling of the Sun is also used as a theoretical tool to investigate its deep layers.

Core

At the center of the Sun, where its density reaches up to 150,000 kg/m³ (150 times the density of water on Earth), thermonuclear reactions (nuclear fusion) convert hydrogen into helium, producing the energy that keeps the Sun in a state of equilibrium. About 8.9 protons (hydrogen nuclei) are converted to helium nuclei every second, releasing energy at the matter-energy conversion rate of 4.26 million tonnes per second or 383 yottawatts (9.15 tons of TNT per second). The core extends from the center of the Sun to about 0.2 solar radii, and is the only part of the Sun where an appreciable amount of heat is produced by fusion: the rest of the star is heated by energy that is transferred outward. All of the energy of the interior fusion must travel through the successive layers to the solar photosphere, before it escapes to space. The high-energy photons (gamma and X rays) released in fusion reactions take a long time to reach the Sun's surface, slowed down by the indirect path taken, as well as constant absorption and re-emission at lower energies in the solar mantle (see below). Estimates of the "photon travel time" range from as much as 50 million years (Richard S. Lewis, The Illustrated Encyclopedia of the Universe, Harmony Books, New York, 1983, p. 65) to as little as 17,000 years [http://www.badastronomy.com/bitesize/solar_system/sun.html]. Upon reaching the surface after a final trip through the convective outer layer, the photons escape as visible light. Neutrinos are also released in the fusion reactions in the core, but unlike photons they very rarely interact with matter, and so almost all are able to escape the Sun immediately.

Radiation zone

From about 0.2 to about 0.7 solar radii, the material is hot and dense enough that thermal radiation is sufficient to transfer the intense heat of the core outward. In this zone, there is no thermal convection: while the material grows cooler with altitude, this temperature gradient is slower than the adiabatic lapse rate and hence cannot drive convection. Heat is transferred by ions of hydrogen and helium emitting photons, which travel a brief distance before being re-absorbed by other ions. Because of this, it can take a photon nearly 1,000,000 years to reach the photosphere.

Convection zone

photosphere From about 0.7 solar radii to 1.0 solar radii, the material in the Sun is not dense enough or hot enough to transfer the heat energy of the interior outward via radiation. As a result, thermal convection occurs as thermal columns carry hot material to the surface (photosphere) of the Sun. Once the material cools off at the surface, it plunges back downward to the base of the convection zone, to receive more heat from the top of the radiative zone. Convective overshoot is thought to occur at the base of the convection zone, carrying turbulent downflows into the outer layers of the radiative zone. The thermal columns in the convection zone form an imprint on the surface of the Sun, in the form of the solar granulation and supergranulation. The turbulent convection of this outer part of the solar interior gives rise to a 'small-scale' dynamo that produces magnetic north and south poles all over the surface of the Sun.

Photosphere

The visible surface of the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. Above the photosphere, sunlight is free to propagate into space and its energy escapes the Sun entirely. Sunlight has approximately a black-body spectrum that indicates its temperature is about 6,000 K, interspersed with atomic absorption lines from the tenuous layers above the photosphere. The photosphere has a particle density of about 10²³/m³ (this is about 1% of the particle density of Earth's atmosphere at sea level). The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. They can be viewed with telescopes operating across the electromagnetic spectrum, from radio through visible light to gamma rays.

Temperature minimum

The coolest layer of the Sun is the temperature minimum region about 500 km above the photosphere. It is about 4,000 K. It is the only part of the Sun cool enough to support simple molecules such as carbon monoxide and water; all other parts of the Sun are hot enough to break chemical bonds.

Chromosphere

Above the visible surface of the Sun is a thin layer, about 2,000 km thick, that is dominated by a spectrum of emission and absorption lines. It is called the chromosphere from the Greek root chromos, meaning color, because the chromosphere is visible as a colored flash at the beginning and end of total eclipses of the Sun.

Corona

The corona is the extended outer atmosphere of the Sun, which is much larger in volume than the Sun itself. The corona merges smoothly with the solar wind that fills the solar system and heliosphere. The low corona, which is very near the surface of the Sun, has a particle density of 10¹¹/m³ (Earth's atmosphere near sea level has a particle density of about 2x10²⁵/m³). The temperature of the corona is several megakelvins.

Theoretical problems

Solar neutrino problem

megakelvin For some time it was thought that the number of neutrinos produced by the nuclear reactions in the Sun was only a third of the number predicted by theory, a result that was termed the solar neutrino problem. Several neutrino observatories were constructed, including the Sudbury Neutrino Observatory and Kamiokande to try to measure the solar neutrino flux. It has recently been found that neutrinos have rest mass, and can therefore transform into harder-to-detect varieties of neutrinos while en route from the Sun to Earth in a process known as neutrino oscillation . Thus, measurement and theory have been reconciled.

Coronal heating problem

The optical surface of the Sun (the photosphere) is known to have a temperature of about 6,000 K. Above it lies the solar corona with a temperature of one million kelvins. The high temperature of the corona suggests that it is heated by something other than the photosphere. It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere. Two main mechanisms have been proposed to explain coronal heating: Wave heating, in which sound, gravitational and magnetohydrodynamic waves are produced by turbulence in the convection zone. These waves travel upward and dissipate in the corona, depositing their energy in the ambient gas in the form of heat. The other proposed mechanism is flare heating, in which magnetic energy is continuously built up by photospheric motion and released through magnetic reconnection in the form of solar flares and waves. , , , . Currently, it is unclear whether waves are an efficient heating mechanism. All waves except Alfven waves have been found to dissipate or refract before reaching the corona (, ). In addition, Alfven waves do not easily dissipate in the corona . Current research focus has therefore shifted towards flare heating mechanisms. One possible candidate to explain coronal heating is continuous flaring at small scales , but this is still an open topic of investigation.

Faint young sun problem

Theoretical models of the sun's development suggest that 3.8 to 2.5 billion years ago, during the Archean period, the Sun was only about 75 percent as bright as it is today. Such a weak star would not have been able to sustain liquid water on the Earth's surface, and thus life should not have been able to develop. However, the geologic record shows that the Earth has remained at a fairly constant temperature throughout its history. In fact, the young Earth was actually warmer than it is today. Some scientists have suggested that the young Earth's atmosphere contained much larger quantities of greenhouse gases such as carbon dioxide and/or ammonia than are present today . Others suggest that cosmic rays might strongly influence the Earth's climate, and that their flux was much higher in the early history of the solar system .

Magnetic field

cosmic ray's rotating magnetic field on the plasma in the interplanetary medium (Solar Wind) [http://quake.stanford.edu/~wso/gifs/HCS.html]. (click to enlarge)]] All matter in the Sun is in the form of gas and plasma due to its high temperatures. This makes it possible for the Sun to rotate faster at its equator (about 25 days) than it does at higher latitudes (28 days near its poles). The differential rotation of the Sun's latitudes causes its magnetic field lines to become twisted together over time, causing magnetic field loops to erupt from the Sun's surface and trigger the formation of the Sun's dramatic sunspots and solar prominences. (See magnetic reconnection.) The solar activity cycle includes old magnetic fields being stripped off the Sun's surface starting from one pole and ending at the other. The magnetic field of the sun reverses once for each 11-year sunspot cycle. The influence of the Sun's rotating magnetic field on the plasma in the interplanetary medium creates the largest structure in the Solar System, the Heliospheric current sheet. The plasma in the interplanetary medium is also responsible for the strength of the Sun's magnetic field at the orbit of the Earth being over 100 times greater than originally anticipated. If space were a vacuum, then the Sun's 10^-4 tesla magnetic dipole field would reduce with the cube of the distance to about 10^-11 tesla. But satellite observations show that it is about 100 times greater at around 10^-9 tesla. Magnetohydrodynamic (MHD) theory predicts that the motion of a conducting fluid (e.g. the interplanetary medium) in a magnetic field, induces electric currents which in turn generates magnetic fields, and in this respect it behaves like an MHD dynamo.

Position of the Sun through the year

The path of the Sun across the sky varies throughout the year. The shape described by the Sun's position, considered at the same time each day for a complete year, is called the analemma, and resembles a figure 8, aligned along the North/South direction. The most obvious variation in the Sun's apparent position through the year is a North/South swing over 47 degrees of angle, due to the 23.5 degree tilt of the Earth, but there is an East/West component as well. The North/South swing in apparent angle is the main source of seasons on Earth.

Solar space missions

seasons using UV light from the He⁺ emission line at 30.4 nm. (Animation (980 kB MPEG))]] To obtain an uninterrupted view of the Sun, the European Space Agency and NASA cooperatively launched the Solar and Heliospheric Observatory (SOHO) on December 2, 1995. Originally a two-year mission, SOHO is now over ten years old (as of late 2005). It has proved so useful that a follow-on mission, the Solar Dynamics Observatory, is planned for launch in 2008. Elemental abundances in the photosphere are well known from spectroscopic studies, but the composition of the interior of the Sun is much less well known. A solar wind sample return mission, Genesis, was designed to allow astronomers to directly measure the composition of solar material. It returned to Earth in 2004 and is undergoing analysis, but it was damaged by crash-landing when its parachute failed to deploy on reentry to Earth's atmosphere.

History and future of the Sun

The Sun is thought to be a second-generation star, whose formation may have been triggered by shockwaves from a nearby supernova. This is suggested by a high abundance of heavy elements such as iron, gold and uranium in the solar system: the most plausible ways that these elements could be produced are by endothermic nuclear reactions during a supernova or by transmutation via neutron absorption inside a massive first generation star. Our Sun does not have enough mass to explode as a supernova, and its mass is below the Chandrasekhar limit. Instead, in 4-5 billion years it will enter its red giant phase, its outer layers expanding as the hydrogen fuel in the core is consumed and the core contracts and heats up. Helium fusion will begin when the core temperature reaches about 3 K. While it is likely that the expansion of the outer layers of the Sun will reach the current position of Earth's orbit, recent research suggests that mass lost from the Sun earlier in its red giant phase will cause the Earth's orbit to move further out, preventing it from being engulfed. Following the red giant phase, giant thermal pulsations will cause the Sun to throw off its outer layers forming a planetary nebula. The Sun will then evolve into a white dwarf, slowly cooling over eons. This stellar evolution scenario is typical of low to medium mass stars.

Human understanding of the Sun

:see also sun worship sun worship mythology]] Mankind's most fundamental understanding of the Sun is as the luminous disk in the heavens whose presence above the horizon creates day, and whose absence causes night. In many prehistoric and ancient cultures, the Sun was thought to be a deity or other supernatural phenomenon. One of the first people in the Western world to offer a scientific explanation for the sun was the Greek philosopher Anaxagoras, who reasoned that it was a giant flaming ball of metal even larger than the Peleponessus, and not the chariot of Helios. For teaching this heresy he was imprisoned by the authorities and sentenced to death (though later released through the intervention of Pericles). With respect to the fixed stars, the Sun appears from Earth to revolve once a year along the ecliptic through the zodiac. Thus, the Sun was considered by Greek astronomers to be one of the seven planets (Greek planetes "wanderer"), after which the seven days of the week are named in some languages.

The Sun as a power source

Sunlight — that is, light radiated from the surface of the Sun — is thought to be the main source of energy near the surface of Earth. The solar constant is the amount of power that the Sun deposits per unit area that is directly exposed to sunlight. It is about 1370 watts per square meter of area. Sunlight on the surface of Earth is attenuated by the Earth's atmosphere, so that less power arrives at the surface — closer to 1000 watts per directly exposed square meter in clear conditions. This energy can be harnessed through several natural and synthetic processes. Photosynthesis by plants captures the energy of sunlight and converts it to chemical form (oxygen and reduced carbon compounds), while direct heating or electrical conversion by solar cells are used by solar power equipment to generate electricity or do other useful work. The energy stored in petroleum is thought to have been converted from sunlight by photosynthesis in the distant past.

Sun and eye damage

Sunlight is very bright, and looking directly at the Sun is painful to the eyes. Looking directly at the Sun when it is high in the sky causes temporary bleaching of the photosensitive pigments in the retina, which makes phosphene visual artifacts and may cause temporary partial blindness. Direct viewing of the Sun with the naked eye delivers about 4 milliwatts of sunlight to the retina that is in the solar image, heating it up and potentially (though not normally) damaging it. Brief viewing of the full direct Sun with the naked eye is unpleasant but generally safe. Viewing the Sun through light-concentrating optics such as binoculars is hazardous without an attenuating (ND) filter to dim the sunlight. Suitable filters are available at welding supply shops and camera stores. Using a proper filter is very important as some improvised filters reduce visible light while passing either infrared or ultraviolet rays that can still damage the eye. Viewing the Sun through unfiltered 7x50 mm binoculars can deliver as much as 2.5 watts of sunlight into each eye, over 300 times more power than naked eye viewing. Even brief glances at the midday Sun through unfiltered binoculars can cause permanent blindness. During partial eclipses of the Sun, another hazardous condition exists because of the way the eye responds to bright light. The pupil is controlled by the total amount of light in the visual field, not by the brightest object in the field. During partial eclipses, most sunlight is blocked by the Moon passing directly in front of the Sun, but the uncovered parts of the photosphere have the same surface brightness as during a normal day. In the dim overall light, the pupil tends to dilate from about 2 mm to perhaps 6 mm diameter, increasing the eye's collecting area by a factor of nearly 10. Each retinal cell that is exposed to the partially-eclipsed solar image thus receives about ten times as much light as it would looking at the normal, non-eclipsed Sun. Viewing the partially eclipsed Sun with the naked eye can cause permanent localized damage to the retina, resulting in small, permanent blind spots for the viewer. This is an especially insidious hazard for inexperienced observers and for children, because there is no immediate perception of pain and it is tempting to stare at the spectacle of the eclipsing Sun, compounding any damage. During sunrise and sunset, sunlight is attenuated by a particularly long passage through Earth's atmosphere, and the direct Sun is sometimes faint enough to be viewed directly without discomfort or safely with binoculars. Hazy conditions, atmospheric dust, and high humidity contribute to this atmospheric attenuation.

External links

- [http://sohowww.nascom.nasa.gov/data/realtime-images.html Current SOHO snapshots]
- [http://soi.stanford.edu/data/farside/index.html Far-Side Helioseismic Holography] from [http://www.stanford.edu Stanford]
- [http://sunearth.gsfc.nasa.gov/eclipse/eclipse.html NASA Eclipse homepage]
- [http://sohowww.nascom.nasa.gov/ Nasa SOHO (Solar & Heliospheric Observatory) satellite] [http://sohowww.nascom.nasa.gov/explore/faq/sun.html FAQ]
- [http://soi.stanford.edu/results/sounds.html Solar Sounds] from [http://www.stanford.edu Stanford]
- [http://www.spaceweather.com Spaceweather.com]
- [http://scienceworld.wolfram.com/astronomy/Sun.html Eric Weisstein's World of Astronomy - Sun]
- [http://www.astro.uu.nl/~strous/AA/en/antwoorden/zonpositie.html The Position of the Sun]
- [http://www.lmsal.com/YPOP/FilmFestival/index.html A collection of solar movies]
- [http://www.solarphysics.kva.se/ The Institute for Solar Physics- Movies of Sunspots and spicules]
- [http://science.msfc.nasa.gov/ssl/pad/solar/default.htm NASA/Marshall Solar Physics website]
- [http://rredc.nrel.gov/solar/codesandalgorithms/spa Solar Position Algorithm] and [http://www.nrel.gov/docs/fy04osti/34302.pdf documentation] from the [http://www.nrel.gov National Renewable Energy Laboratory]
- [http://libnova.sourceforge.net/index.html libnova] - a celestial mechanics and astronomical calculation library

References

# Alfven, H., 1947, Monthly Notices of the Royal Astronomical Society., 107, 211 # # Biermann, L., 1946, Naturwissenschaffen, 33, 118 # Bonanno, A., Schlattl, H., Paternò, L. (2002), The age of the Sun and the relativistic corrections in the EOS, Astronomy and Astrophysics, v.390, p.1115-1118 # Carslaw, K.S., Harrison, R.G., Kirkby, J., 2002, Cosmic Rays, Clouds, and Climate, Science, 298, 1732-1737 # Kasting, J.F., Ackerman, T.P., 1986, Climatic Consequences of Very High Carbon Dioxide Levels in the Earth’s Early Atmosphere, Science, v. 234, p. 1383-1385 # Parker, E.N., 1958, Astrophysical Journal, 128, 644 # Parker, E.N., 1988, Astrophysical Journal, 330, 474 # Priest, E.R., 1982, Solar Magnetohydrodynamics (Dordrecht: Reidel), pp. 206-245 # Schlattl, H. (2001), Three-flavor oscillation solutions for the solar neutrino problem, Physical Review D, vol. 64, Issue 1 # Sturrock, P.A., & Uchida, Y., 1981, Astrophysical Journal., 246, 331 # Thompson, M.J. (2004), Solar interior: Helioseismology and the Sun's interior, Astronomy & Geophysics, v. 45, p. 4.21-4.25 Category:Yellow dwarfs Category:Space plasmas Category:Plasma physics als:Sonne zh-min-nan:Ji̍t-thâu ko:태양 ms:Matahari ja:太陽 simple:Sun th:ดวงอาทิตย์

Longitude

showing lines of longitude, which appear curved and vertical in this projection, but are actually halves of great circles]] Longitude, sometimes denoted by the Greek letter λ, describes the location of a place on Earth east or west of a north-south line called the Prime Meridian. Longitude is given as an angular measurement ranging from 0° at the Prime Meridian to +180° eastward and −180° westward. Unlike latitude, which has the equator as a natural starting position, there is no natural starting position for longitude. Therefore, a reference meridian had to be chosen. While British cartographers had long used the Greenwich meridian in London, other references were used elsewhere, including: Ferro, Rome, Copenhagen, Jerusalem, Saint Petersburg, Pisa, Paris, Philadelphia and Washington. In 1884, the International Meridian Conference adopted the Greenwich meridian as the universal prime meridian or zero point of longitude. Each degree of longitude is further sub-divided into 60 minutes, each of which divided into 60 seconds. A longitude is thus specified as 23° 27′ 30" E. For high accuracy, the seconds are specified with a decimal fraction. An alternative representation uses degrees and minutes, where parts of a minute are expressed as a decimal fraction, thus: 23° 27.500′ E. Degrees expressed as a decimal number is also used: 23.45833° E. Sometimes, the West/East suffix is replaced by a negative sign for West. Confusingly, the convention of negative for East is also sometimes seen. The preferred convention that East is positive is consistent with the right-handed x-axis in the Cartesian coordinate system. A specific longitude may then be combined with a specific latitude to give a precise position on the Earth's surface. As opposed to a degree of latitude, which always corresponds to about 111 km (69 mi), a degree of longitude corresponds to a distance from 0 to 111 km: it is 111 km times the cosine of the latitude, when the distance is laid out on a circle of constant latitude; if the shortest distance, on a great circle were used, the distance would be even a little less. Longitude at a point may be determined by calculating the time difference between that at its location and Coordinated Universal Time (UTC). Since there are 24 hours in a day and 360 degrees in a circle, the sun moves 15 degrees per hour (360°/24 hours = 15° per hour). So if the time zone a person is in is three hours ahead of UTC then that person is near 45° longitude (3 hours × 15° per hour = 45°). The word near was used because the point might not be at the center of the time zone; also the time zones are defined politically, so their centers and boundaries often do not lie on meridians at multiples of 15°. In order to perform this calculation, however, a person needs to have a chronometer (watch) set to UTC and needs to determine local time by solar observation or astronomical observation. The details are more complex than described here: see the articles on Universal Time and on the Equation of time for more details. A line of constant longitude is a meridian, and half of a great circle.

History of the measurement of longitude

The search for a solution

The measurement of longitude is important to both cartography and navigation. Historically, the most important practical application of these was to provide safe ocean navigation. Knowledge of both latitude and longitude was required. Whereas latitude was easy to determine by celestial navigation using the elevation of the pole star or of the sun at noon, for longitude early ocean navigators had to rely on dead reckoning. This was inaccurate on long voyages out of sight of land, and these voyages sometimes ended with shipwrecks. The discovery of how to measure longitude accurately was among the important discoveries of the 1600s and 1700s. The first effective solution for mapmaking was achieved by Giovanni Domenico Cassini starting in 1681, using Galileo's method based on the satellites of Jupiter. For application without a professional astronomer at hand, and in particular measurement at sea, the problem was more difficult; see Dava Sobel's book: Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time for a good historical overview. This genius was John Harrison.

The Longitude Act and Harrison's chronometer

The tragic wrecking of the British fleet led by Sir Cloudesley Shovell led to the British Longitude Act, which created the Longitude Prize for anyone who could devise a practical method of determining longitude at sea. This was eventually achieved by John Harrison with his chronometer; the timepiece in question was the one later known as H-4. Harrison's son led a voyage aboard a ship from Portsmouth, England to the Caribbean port city of Bridgetown, Barbados with the H-4 aboard. Harrison demonstrated a method of determining longitude by keeping the exact time of day for Britain, while using astronomical observations to find the exact local time on the ship as it sailed to the island of Barbados. In this way he was able to determine the position of the ship relative to Barbados whose longitude was known. The calculation of the ship's position was only 10 miles in error when it arrived.

Later developments

Exchanges of chronometers between observatories, to determine the precise differences in local time, used in conjunction with the observation of the transit of stars across the meridian became a standard way of determining longitude. Another method was the observation of occultations of stars at different observatories. From the mid 19th century, instead of exchanging chronometers, telegraph time signals were used; radio time signals followed in the early 20th century. Satellites were used for measurements from the 1970s and 1980s - see GPS. Longitude is the second part of the ICBM address, latitude being the first.

Ecliptic latitude and longitude

Ecliptic latitude and longitude are defined for the planets, stars, and other celestial bodies in a similar way to that in which the terrestrial counterparts are defined. The pole is the normal to the ecliptic nearest to the celestial north pole. Ecliptic latitude is measured from 0° to 90° north (+) or south (−) of the ecliptic. Ecliptic longitude is measured from 0° to 360° eastward (the direction that the Sun appears to move relative to the stars) along the ecliptic from the vernal equinox. The equinox at a specific date and time is a fixed equinox, such as that in the J2000 reference frame. However, the equinox moves because it is the intersection of two planes, both of which move. The ecliptic is relatively stationary, wobbling within a 4° diameter circle relative to the fixed stars over millions of years under the gravitational influence of the other planets. The greatest movement is a relatively rapid gyration of Earth's equatorial plane whose pole traces a 47° diameter circle caused by the Moon. This causes the equinox to precess westward along the ecliptic about 50" per year. This moving equinox is called the equinox of date. Ecliptic longitude relative to a moving equinox is used whenever the positions of the Sun, Moon, planets, or stars at dates other than that of a fixed equinox is important, as in calendars, astrology, or celestial mechanics. The 'error' of the Julian or Gregorian calendar is always relative to a moving equinox. The years, months, and days of the Chinese calendar all depend on the ecliptic longitudes of date of the Sun and Moon. The 30° zodiacal segments used in astrology are also relative to a moving equinox. Celestial mechanics (here restricted to the motion of solar system bodies) uses both a fixed and moving equinox. Sometimes in the study of Milankovitch cycles, the invariable plane of the solar system is substituted for the moving ecliptic. Longitude may be denominated from 0 to

\begin2\pi\end

radians in either case.

Longitude on bodies other than Earth

Planetary co-ordinate systems are defined relative to their mean axis of rotation and various definitions of longitude depending on the body. The longitude systems of most of those bodies with observable rigid surfaces have been defined by references to a surface feature such as a crater. The north pole is that pole of rotation that lies on the north side of the invariable plane of the solar system (the ecliptic). The location of the prime meridian as well as the position of body's north pole on the celestial sphere may vary with time due to precession of the axis of rotation of the planet (or satellite). If the position angle of the body's prime meridian increases with time, the body has a direct (or prograde) rotation; otherwise the rotation is said to be retrograde. In the absence of other information, the axis of rotation is assumed to be normal to the mean orbital plane; Mercury and most of the satellites are in this category. For many of the satellites, it is assumed that the rotation rate is equal to the mean orbital period. In the case of the giant planets, since their surface features are constantly changing and moving at various rates, the rotation of their magnetic fields is used as a reference instead. In the case of the Sun, even this criterion fails (because its magnetosphere is very complex and does not really rotate in a steady fashion), and an agreed-upon value for the rotation of its equator is used instead. For "planetographic longitude", west longitudes (i.e., longitudes measured positively to the west) are used when the rotation is prograde and east longitudes (i.e., longitudes measured positively to the east) when the rotation is retrograde. However, "planetocentric longitude" is measured positively to the east. Because of tradition, the Earth, Sun, and Moon do not conform with this definition: their rotations are prograde and longitudes run both east and west 180° instead of the usual 360°. The reference surfaces for some planets (such as Earth and Mars) are ellipsoids of revolution for which the equatorial radius is larger than the polar radius. Smaller bodies (Io, Mimas, etc.) tend to be better approximated by triaxial ellipsoids; however, triaxial ellipsoids would render many computations more complicated, especially those related to map projections. Many projections would lose their elegant and popular properties. For this reason spherical reference surfaces are frequently used in mapping programs. The modern standard for maps of Mars (since about 2002) is to use planetocentric coordinates. The meridian of Mars is located at Airy-0 crater. [http://www.esa.int/SPECIALS/Mars_Express/SEM0VQV4QWD_0.html]

External links

- [http://www.bcca.org/misc/qiblih/latlong.html Look-up Latitude and Longitude]
- [http://jan.ucc.nau.edu/~cvm/latlon_find_location.html Resources for determining your latitude and longitude]
- [http://www.pbs.org/wgbh/nova/longitude/ PBS Nova Online: Lost at Sea, the Search for Longitude]
- [http://www.hnsky.org/iau-iag.htm IAU/IAG Working Group On Cartographic Coordinates and Rotational Elements of the Planets and Satellites]
- Category:Navigation Category:Angle ja:経度 th:ลองจิจูด

Tokyo

Wikipedia:WikiProject Japanese prefectures

Tokyo (Japanese: 東京, , "eastern capital") is the home to the Japanese government and emperor, and so the Capital of Japan. It is also the nation's most populous urban area (12 million people, or about 10 percent of the country's population, live in Tokyo) and one of the 47 prefectures of Japan.

Structure of Tokyo

Under Japanese law, Tokyo is designated as a to (都, often translated "metropolis"), not a city (although it is often mistaken for one), and its administrative structure is similar to that of Japan's other prefectures. Within Tokyo lie dozens of cities, towns, and villages. It includes 23 special wards (特別区 -ku) which until 1943 comprised the city of Tokyo but are now separate, self-governing municipalities, each with a mayor and a council, and having the status of a city. In addition to these 23 municipalities, Tokyo also encompasses 26 more cities (市 -shi), 5 towns (町 -chō or machi), and 8 villages (村 -son or mura), each of which has a local government. The Tokyo Metropolitan Government is headed by a publicly-elected governor and metropolitan assembly. Its headquarters are located in the ward of Shinjuku. Tokyo includes lakes, rivers, dams, farms, remote islands, and national parks, in addition to its famous neon jungle, skyscrapers and crowded subways.

Location

Tokyo is located in the Kanto region on the island of Honshu. Its center is at 35°41' North, 139°46' East (35.68333, 139.7667) [http://earth-info.nga.mil/gns/html/cntry_files.html], but its borders extend to outlying islands in the Pacific Ocean, some as far as 1,000 km south of the mainland.

Influence

As the nation's center of politics, business, finance, education, mass media, and pop culture, Tokyo has Japan's highest concentration of corporate headquarters, financial institutions, universities and colleges, museums, theaters, and shopping and entertainment establishments. It boasts a highly-developed public transportation system with numerous train and subway lines. This extreme concentration is both boon and bane, prompting an ongoing debate over moving the nation's capital to another region. There is also great fear of a catastrophic earthquake striking Tokyo, which may in effect cripple the entire nation. Nevertheless, Tokyo continues to draw people from across Japan and other countries; a substantial portion of the population is not native to the region, and Tokyo is still a place to meet people from all over the country and the world.

History

outlying islands Tokyo's rise to prominence can be largely attributed to two men: Tokugawa Ieyasu and Emperor Meiji. In 1603, after unifying the warring states of Japan, Shogun Tokugawa Ieyasu made Edo (now Tokyo) his base of operations. As a result, the city developed rapidly and grew to become one of the largest cities in the world with a population topping 1 million by the 18th century. It became the de facto capital of Japan even while the emperor resided in Kyoto, the imperial capital. Since the city's early beginnings and even now, Edo/Tokyo has always had a large non-native population. Ieyasu himself was an outsider who brought many outsiders to help build the city and government. The sankin kotai system also required provincial warlords to periodically parade to Edo and keep a residence in the city along with key family members and samurai retainers. The term "Edokko" (child of Edo) was even coined (and still used today) to distinguish the natives from the non-natives. After 250 years, the shogunate was overthrown under the banner of restoring imperial rule. In 1869, the figurehead 17-year-old Emperor Meiji moved to Edo, which was renamed "Tokyo". Tokyo was already the nation's political, economic, and cultural center, and the emperor's residence made it a de facto imperial capital as well with the former Edo Castle becoming the Imperial Palace. Imperial Palace shows the old German name for Tokyo, Jedo.]] Tokyo went on to suffer two major catastrophes and has remarkably recovered from both of them. One was the Great Kanto Earthquake in 1923, and the other was World War II. The firebombings in 1945 were almost as devastating as the atomic bombs of Hiroshima and Nagasaki combined. Large areas of the city were flattened. Today, hardly a trace of the war is evident to visitors to the city, but many people still carry its emotional scars. After the war, Tokyo was rebuilt with excellent train and subway systems, which were showcased to the world during the city's 1964 Summer Olympics. The 1970s brought new high-rise developments, a new and controversial airport at Narita (1978), and a population increase to about 11 million (in the metropolitan area). In the 1980s, real estate prices skyrocketed during an economic bubble: many got rich quick, but the bubble burst in the early 1990s and many companies, banks, and individuals were caught with real estate shrinking in value. A major recession followed, making the 1990s Japan's "lost decade" which still continues today. Tokyo still sees new or renewed urban centers being developed on large lots of idle land. Recent projects include Ebisu Garden Place, Tennozu Isle, Shiodome, Roppongi Hills, Shinagawa (now also a shinkansen station), and Tokyo Station (Marunouchi side). Land reclamation projects in Tokyo have also been going on for centuries. The most prominent is the Odaiba area, now a major shopping and entertainment center.

Geography and administrative divisions

Odaiba (such as Odaiba) has been omitted for clarity. The islands cannot be shown at this scale. Click on the map to enlarge it.]] Tokyo is northwest of Tokyo Bay, and is about 90 km east-to-west and 25 km north-to-south. It borders Chiba Prefecture to the east, Yamanashi Prefecture to the west, Kanagawa Prefecture to the south, and Saitama Prefecture to the north. It also consists of islands in the Pacific Ocean directly south -- the Izu Islands are closest, while the Ogasawara Islands stretch over 1,000 km away from mainland Japan. Toyko has been hit by powerful earthquakes in 1703, 1782, 1812, 1855 and 1923. The 1923 earthquake with an estimated magnitude of 8.3 killed 142,000 people. Tokyo is also part of the Greater Tokyo Area, by far the world's most populous metropolitan region, which includes the surrounding prefectures of Kanagawa, Saitama, and Chiba. Tokyo consists of the following 23 special wards, 26 cities, 5 towns, and 8 villages:

The 23 special wards

Each of the 23 special wards (tokubetsu-ku) of Tokyo is a local municipality with its own elected mayor and assembly. It differs from an ordinary city in that certain governmental functions are handled by the Tokyo Metropolitan Government. As of September 1, 2003, the official total population of the 23 wards combined was about 8.34 million, with a population density of 13,416 persons per square kilometer.

Cities

municipality.]] West of the 23 wards, Tokyo consists of cities (shi), which enjoy a similar legal status to cities elsewhere in Japan. While serving a role as "bed towns" for those working in central Tokyo, some of these cities also have a local commercial and industrial base. Collectively, these cities are often known as "West Tokyo."

Districts, towns, and villages

The far west is occupied by the district (gun) of Nishitama. Much of this area is mountainous and unsuitable for urbanization. The highest mountain in Tokyo, Mount Kumotori, is 2,017 m high; other mountains in Tokyo include Mount Takasu (1737 m), Mount Odake (1266 m), and Mount Mitake (929 m). Lake Okutama, on the Tama River near Yamanashi Prefecture, is Tokyo's largest lake.
- Hinode
- Mizuho
- Okutama
- Hinohara Village

Islands

Hinohara Tokyo's outlying islands extend as far as 1,850 km from central Tokyo. Because of the islands' distance from the city, they are locally run by branches of the metropolitan government. Most of the islands are classified as villages. Izu Islands
- Oshima—Islands of Kozushima, Niijima, Oshima, and Toshima.
- Miyake—Islands of Mikurajima and Miyakejima (main town: Miyake).
- Hachijo—Islands of Aogashima and Hachijojima (main town: Hachijo). Ogasawara Islands
- Ogasawara—Ogasawara includes, from north to south, Chichi-jima, Nishinoshima, Haha-jima, Kita Iwo Jima, Iwo Jima, and Minami Iwo Jima. Also includes two tiny outlying islands: Minami Torishima, the easternmost point in Japan and at 1 850 km the most distant island from central Tokyo, and Okino Torishima, the southernmost point in Japan. The Iwo chain and the outlying islands are mostly uninhabited, but there are small local populations on the three islands closer to Honshu.

National Parks

There are two national parks in West Tokyo: Chichibu-Tama National Park, located in Nishitama and spilling over into Yamanashi and Saitama Prefectures, and Meiji no Mori Takao Quasi-National Park, located around Mount Takao to the south of Hachioji. South of Tokyo is the Ogasawara National Park.

Major Districts

Ogasawara National Park Ogasawara National Park in front of the Hachikō exit of Shibuya station.]] The center of Tokyo is Kokyo, or the Imperial Palace, the former site of Edo Castle. The term "central Tokyo" today may refer to either the area within the looping Yamanote train line or to Tokyo's 23 special wards (ku) covering about 621 square kilometers, the most densely-populated area of Tokyo. There are a number of major urban centers where business, shopping, and entertainment are concentrated. They are each centered at a major train station where multiple train lines operate.
- Shinjuku — Tokyo's capital where the Tokyo Metropolitan Government Building is located. It is best known for Tokyo's early skyscrapers since the early 1970s. Major department stores, camera and computer stores, and hotels can be found. On the east side of Shinjuku Station, Kabuki-cho is notorious for its many bars and nightclubs.
- Marunouchi and Otemachi — The main financial and business district of Tokyo has many headquarters of banks, trading companies, and other major businesses. The area is seeing a major redevelopment with new buildings for shopping and entertainment constructed in front of Tokyo Station's Marunouchi side.
- Ginza and Yurakucho — Major shopping and entertainment district with department stores, upscale shops selling brand-name goods, and movie theaters.
- Shinbashi—By being the gateway to Odaiba and having the new Shiodome Shiosite complex of high-rise buildings, this area has been effectively revitalized.
- Shinagawa — In addition to the major hotels on the west side of Shinagawa Station, the former sleepy east side of the station has been redeveloped as a major center for business.
- Shibuya — A longtime center of shopping, fashion, and entertainment, especially for the younger set.
- Ikebukuro — Anchored by the Sunshine City (which was once Tokyo's tallest building) hotel and shopping complex, this is another area where people gather due to the various train lines shooting out of Ikebukuro Station.
- Ueno — Ueno Station serves areas north of Tokyo from where many people commute. Besides department stores and shops in Ameyoko, Ueno boasts Ueno Park, Ueno Zoo, and major national museums. In spring, Ueno Park and adjacent Shinobazu Pond are prime places to view cherry blossoms.
- Odaiba — A large, reclaimed, waterfront area that has become one of Tokyo's most popular shopping and entertainment districts.
- Kinshicho — Major shopping and entertainment area in eastern Tokyo.
- Kichijoji — Major shopping and entertainment area in western Tokyo.
- Nagatacho - The political heart of Tokyo and the nation. It is the location of the Diet, government ministries, and party headquarters.
- Akasaka - Upscale commercial district next to Roppongi, Nagatacho, and Aoyama.
- Aoyama - An upscale neighborhood of Tokyo with parks, an enormous cemetery, expensive housing, trendy cafes, and international restaurants (includes the subway station Omotesando).

Economy

Omotesando] Tokyo has the largest metropolitan economy in the world: its nominal GDP of around $1.315 trillion is greater than the 8th largest national economy in the world. It is a major international finance center, headquarters to several of the world's largest investment banks and insurance companies, and serves as a hub for Japan's transportation, publishing, and broadcasting industries. During the centralized growth of Japan's economy following World War II, many large firms moved their headquarters from cities such as Osaka (the historical commercial capital) to Tokyo, in an attempt to take advantage of better access to the government. This trend has begun to slow due to ongoing population growth in Tokyo and the high cost of living there.

Demographics

As one of the major cities of the world, Tokyo has over 8 million people living within its 23 wards, and during the daytime, the population swells by over 2.5 million as workers and students commute from adjacent areas. This effect is even more pronounced in the three central wards of Chiyoda, Chuo, and Minato, whose collective population is less than 300,000 at night, but over 2 million during the day. Population By area (as of Oct. 1, 2003)
- All of Tokyo: 12.36 million
- 23 special wards: 8.34 million
- Tama area: 4 million
- Islands: 27,000 By age (As of Jan. 1, 2003):
- Juveniles (0-14): 1.433 million (12%)
- Working population (15-64): 8.507 million (71.4%)
- Aged population (65+): 2.057 million (16.6%) By time (As of 2000)
- Nighttime: 12.017 million
- Daytime: 14.667 million By nationality
- Foreign residents: 353,826 (as of Jan. 1, 2005)
- Top 5 Nationalities of Foreign Residents: Chinese (120,331), Korean (103,191), Philippine (31,505), American (18, 043), British (7,585)

Transportation

Tokyo is Japan's largest domestic and international hub for rail, ground, and air transportation. Public transportation within Tokyo is dominated by an extensive network of clean and efficient, if occasionally very crowded trains and subways run by a variety of operators, with buses, monorails and trams playing a secondary role.

Airports

- Tokyo International Airport in Ota Ward (Haneda) — Mainly for domestic flights.
- Narita International Airport in Narita, Chiba Prefecture — Major gateway for international travelers.
- Chofu Airport in Chofu City — Handles commuter flights to the Izu islands.
- Oshima Airport— Oshima Island
- Hachijojima Airport— Hachijo Island
- Miyakejima Airport— Miyake Island
- Tokyo Heliport— Koto Ward

Railways and subways

Tokyo Heliport Tokyo Heliport Rail is the primary mode of transportation in Tokyo, which has the most extensive underground network in the world and an equally extensive network of surface lines. Most lines in Tokyo are privately owned and operated, with the exception of Toei Subway (run directly by the metropolitan government). Railway and subway lines are highly integrated; commuter trains from the suburbs continue directly into the subway network on many lines, often emerging on the other side of the city to serve another company's surface line. It is estimated some 20 million people take the 70 plus train lines and go through 1000 stations in the metropolitan area daily. Some of the larger stations, like Shinjuku Station and Tokyo station, are miles long and are the busiest in the world. Tokyo station
- JR East—The largest passenger railway company in the world. In addition to the Shinkansen ("bullet train" lines), JR operates Tokyo's largest railway network, including the Yamanote Line loop, the Keihin-Tohoku Line between Saitama and Yokohama, the Chuo Line to West Tokyo, and the Sobu Line to Chiba. It is also the majority stockholder in the Tokyo Monorail, one of the world's most commercially successful monorail lines.
- Keihin Kyuko Electric Railway (Keikyū)—Operates out of Shinagawa Station to Kanagawa and Haneda Airport.
- Keisei Electric Railway—Operates out of Ueno Station to Chiba (including Narita International Airport).
- Keio Electric Railway—Operates out of Shinjuku Station to West Tokyo. Shinjuku Station
- Odakyu Electric Railway—Operates out of Shinjuku Station to Kanagawa, most notably Odawara and Hakone.
- Seibu Railway—Operates out of Shinjuku Station and Ikebukuro Station to West Tokyo.
- Tobu Railway—Operates out of Ikebukuro Station and Asakusa Station to Saitama, Gunma, and Tochigi.
- Tokyo Kyuko Electric Railway (Tokyu)—Operates out of Shibuya Station to West Tokyo and Kanagawa.
- Tokyo Metro (formerly Eidan)—Operates Japan's largest subway network.
- Tokyo Metropolitan Bureau of Transportation—Operates the Toei subway lines and the Arakawa streetcar line, Tokyo's sole streetcar line.
- Tsukuba Express, linking Akihabara Station with Tsukuba since its opening in August 2005.

Buses

Tsukuba The metropolitan government operates Toei buses mainly within the 23 special wards while private bus companies operate other bus routes. Bus transportation is convenient for places far from the train or subway stations. Most bus routes stop or terminate at a train or subway station, and they can be quite complicated with no signs in English. The Toei buses charge 200 yen per ride which the customer pays while boarding. Buses run by other companies may charge according to distance, and the customer pays when leaving the bus.

Others

- Taxis—Available along most major streets. Starting fare is about 650 yen.
- Streetcars—Once a common sight before subways and buses came to fore, streetcar lines have shrunk to only one route called the Toden Arakawa Line plying the route between Waseda and Minowabashi.
- Ferries/Boats—Long-distance ferries operated by Tokai Kisen go to outlying islands such as the Ogasawara Islands and Izu Islands. River boats on the Sumida River operate between Asakusa and Kasai Rinkai Park, mainly for tourists.
- Expressways—Many expressways converge at Tokyo including the Tomei Expressway, Chuo Expressway, Kan'etsu National Expressway, Ken-ō Expressway, Tokyo Gaikan Expressway, Daisan Keihin Highway, and Keiyo Highway. The Shuto Expressway network covers central Tokyo, linking the intercity expressways together.

Tourism

Chuo Expressway) and Tokyo Tower.]] Tokyo has many tourist attractions. It would take weeks to see all the major ones. Thanks to a very convenient train and subway system (with signs in English), it is easy to visit most of these attractions. Here are only some of them (random order).

Shrines, temples, and castles

Tokyo Tower] The Imperial Palace, Meiji Shrine, and Sensoji Temple are the three most popular ones in Tokyo.
- Kokyo, or the Imperial Palace — Home of the Emperor and Crown Prince and their families.
- Sensoji — Asakusa
- Meiji Shrine — Dedicated to Emperor Meiji
- State Guest-House
- Yasukuni Shrine
- Zojoji — Main headquarters of the Pure Land Buddhism (浄土宗）sect.
- Tsukiji Honganji Temple — Tokyo headquarters of the Jodo Shinshu Nishi Honganji Buddhist sect.
- Gokokuji Temple Gokokuji Temple in Asakusa]]

Festivals and events

Tokyo holds many festivals large and small throughout the year.

Spring (March-May)

Gokokuji Temple.]]
- Bunkyo Tsutsuji Matsuri (azalea festival) at Nezu Shrine in Bunkyo-ku.
- Fuji Matsuri (wisteria festival) at Kameido Tenjin Shrine in Koto-ku.
- Hinode Matsuri (sunrise festival) at Mitake Shrine in Ome.
- Kachiya Festival at Katori Shrine in Koto-ku.
- Kanda Myojin Omikoshi Togyo at Kanda Myojin Shrine in Chiyoda-ku.
- Kappa Matsuri at Ebara Shrine in Shinagawa-ku.
- Kifune Matsuri at Kifune Shrine in Ota-ku.
- Kurayami Matsuri (black night festival) at Okunitama Shrine in Fuchu.
- Meiji Shrine Spring Festival at Meiji Shrine in Shibuya-ku.
- Osunafumi Taisai (walking-on-sand ritual) at Tamagawa Daishi Temple in Setagaya-ku.
- Sanja Matsuri at Asakusa Shrine in Taito-ku.
- Shishi Matsuri (lion dance festival) at Nagasaki Shrine in Toshima-ku.
- Takigi Noh (open-air torchlight Noh performance) at Zojoji Temple in Minato-ku.
- Yayoi Matsuri ceremony by the Edo Shobo Kinen-kai (Edo Civilian Fire Fighters' Association) in the vicinity of Sensoji Temple in Taito-ku.

Summer (June-Aug.)

- Koenji Awa Odori
- Asakusa Samba Matsuri
- Sumida Fireworks in Asakusa and Sumida Ward
- Tokyo Bay Fireworks
- Jingu Fireworks
- Fukagawa Hachiman Matsuri

Fall (Sept.-Nov.)

- Tokyo Jidai Matsuri in Asakusa

Winter (Dec.-Feb.)

- Hatsumode New Year's Prayers at Meiji Shrine, Sensoji, and other major shrines and temples
- Dezome-shiki Fireman's Parade at Tokyo Big Sight
- Setsubun at Sensoji and other major temples

Others

- Grand Sumo Tournaments in Jan., May, and Sept. at the Ryogoku Kokugikan
- Tsukiji fish market

Parks and gardens

Tsukiji fish market.]]

Flowers

Tsukiji fish market
- Plum blossoms (Feb.-March)—Yoshino Baigo in Ome, Mukojima Hyakkaen Garden, Hanegi Park in Umegaoka
- Cherry blossoms (Late March-early April)—Ueno Park and Shinobazu Pond, Yoyogi Park, Shinjuku Gyoen, Inokashira Park in Kichijoji, Chidorigafuchi Imperial Palace moat near the Budokan, Aoyama Cemetery, Sumida Park and River near Asakusa, International Christian University
- Wisteria (Late April-early May)—Kameido Tenjin Shrine in Koto Ward
- Azaleas (Late April-early May)—Nezu Shrine, East Garden of the Imperial Palace, Shiofune Kannon Temple in Ome
- Roses (mid-late May)—Jindai Botanical Garden in Chofu
- Irises (early-mid June)—Meiji Shrine, Horikiri Iris Garden
- Hydrangeas (June-July)—Takahata Fudo Temple, Hino

Scenic views

Horikiri Iris Garden]
- Tokyo Tower
- Tokyo Metropolitan Government Building Observatory
- Rainbow Bridge walkway
- Sunshine City Observatory in Ikebukuro
- Fuji TV Headquarters Observatory in Odaiba

Shopping and entertainment

Tokyo has various shopping districts famous for specific products. Akihabara is well-known for electronics stores, Shinjuku for camera and book shops, Ginza for department stores and luxury goods, Shibuya and Harajuku for teenage fashion, and Jinbocho for used (and new) books. :See also: Tourism in Japan

Prefectural symbols

The Tokyo Metropolitan Government uses a gingko leaf design in iron fences along streets, Toei metropolitan buses, and other facilities they own or operate. Traditional symbols of Tokyo include Nijubashi (a bridge at the Imperial Palace), the National Diet Building, the Kaminarimon (Thunder Gate) housing the big red paper lantern at Sensoji in Asakusa, the State Guest-House in the Akasaka Imperial Palace, and the Meiji-era facade of Tokyo Station. More contempor