Steel is an alloy of iron and carbon, sometimes other elements. Because of its high tensile strength and low cost, it is a major component used in buildings, tools, automobiles, machines and weapons. Iron is the base metal of steel. Iron is able to take on two crystalline forms, body centered cubic and face centered cubic, depending on its temperature. In the body-centered cubic arrangement, there is an iron atom in the center and eight atoms at the vertices of each cubic unit cell, it is the interaction of the allotropes of iron with the alloying elements carbon, that gives steel and cast iron their range of unique properties. In pure iron, the crystal structure has little resistance to the iron atoms slipping past one another, so pure iron is quite ductile, or soft and formed. In steel, small amounts of carbon, other elements, inclusions within the iron act as hardening agents that prevent the movement of dislocations that are common in the crystal lattices of iron atoms; the carbon in typical steel alloys may contribute up to 2.14% of its weight.
Varying the amount of carbon and many other alloying elements, as well as controlling their chemical and physical makeup in the final steel, slows the movement of those dislocations that make pure iron ductile, thus controls and enhances its qualities. These qualities include such things as the hardness, quenching behavior, need for annealing, tempering behavior, yield strength, tensile strength of the resulting steel; the increase in steel's strength compared to pure iron is possible only by reducing iron's ductility. Steel was produced in bloomery furnaces for thousands of years, but its large-scale, industrial use began only after more efficient production methods were devised in the 17th century, with the production of blister steel and crucible steel. With the invention of the Bessemer process in the mid-19th century, a new era of mass-produced steel began; this was followed by the Siemens–Martin process and the Gilchrist–Thomas process that refined the quality of steel. With their introductions, mild steel replaced wrought iron.
Further refinements in the process, such as basic oxygen steelmaking replaced earlier methods by further lowering the cost of production and increasing the quality of the final product. Today, steel is one of the most common manmade materials in the world, with more than 1.6 billion tons produced annually. Modern steel is identified by various grades defined by assorted standards organizations; the noun steel originates from the Proto-Germanic adjective stahliją or stakhlijan, related to stahlaz or stahliją. The carbon content of steel is between 0.002% and 2.14% by weight for plain iron–carbon alloys. These values vary depending on alloying elements such as manganese, nickel, so on. Steel is an iron-carbon alloy that does not undergo eutectic reaction. In contrast, cast iron does undergo eutectic reaction. Too little carbon content leaves iron quite soft and weak. Carbon contents higher than those of steel make a brittle alloy called pig iron. While iron alloyed with carbon is called carbon steel, alloy steel is steel to which other alloying elements have been intentionally added to modify the characteristics of steel.
Common alloying elements include: manganese, chromium, boron, vanadium, tungsten and niobium. Additional elements, most considered undesirable, are important in steel: phosphorus, sulfur and traces of oxygen and copper. Plain carbon-iron alloys with a higher than 2.1% carbon content are known as cast iron. With modern steelmaking techniques such as powder metal forming, it is possible to make high-carbon steels, but such are not common. Cast iron is not malleable when hot, but it can be formed by casting as it has a lower melting point than steel and good castability properties. Certain compositions of cast iron, while retaining the economies of melting and casting, can be heat treated after casting to make malleable iron or ductile iron objects. Steel is distinguishable from wrought iron, which may contain a small amount of carbon but large amounts of slag. Iron is found in the Earth's crust in the form of an ore an iron oxide, such as magnetite or hematite. Iron is extracted from iron ore by removing the oxygen through its combination with a preferred chemical partner such as carbon, lost to the atmosphere as carbon dioxide.
This process, known as smelting, was first applied to metals with lower melting points, such as tin, which melts at about 250 °C, copper, which melts at about 1,100 °C, the combination, which has a melting point lower than 1,083 °C. In comparison, cast iron melts at about 1,375 °C. Small quantities of iron were smelted in ancient times, in the solid state, by heating the ore in a charcoal fire and welding the clumps together with a hammer and in the process squeezing out the impurities. With care, the carbon content could be controlled by moving it around in the fire. Unlike copper and tin, liquid or solid iron dissolves carbon quite readily. All of these temperatures could be reached with ancient methods used since the Bronze Age. Since the oxidation rate of iron increases beyond 800 °C, it is important that smelting take place in a low-oxygen environment. Smelting, using carbon to reduce iro
Tashkent is the capital and largest city of Uzbekistan, as well as the most populated city in ex-Soviet Central Asia with a population in 2018 of 2,485,900. It is located in the north-east of the country close to the Kazakhstan border. Tashkent was influenced by the Sogdian and Turkic cultures in its early history, before Islam in the 8th century AD. After its destruction by Genghis Khan in 1219, the city was profited from the Silk Road. From 18th to 19th century, the city became an independent city-state, before being re-conquered by the Khanate of Kokand. In 1865, it fell to the Russian Empire, became the capital of Russian Turkestan. In Soviet times, Tashkent witnessed major growth and demographic changes due to forced deportations from throughout the Soviet Union. Today, as the capital of an independent Uzbekistan, Tashkent retains a multi-ethnic population, with ethnic Uzbeks as the majority. In 2009, the city celebrated its 2,200 years of written history. See also: Timeline of Tashkent and History of TashkentDuring its long history, Tashkent has had various changes in names and political and religious affiliations.
Tashkent was settled by ancient people as an oasis on the Chirchik River, near the foothills of the West Tian Shan Mountains. In ancient times, this area contained Beitian the summer "capital" of the Kangju confederacy; some scholars believe that a "Stone Tower" mentioned by Ptolemy and by other early accounts of travel on the Silk Road referred to this settlement. This tower is said to have marked the midway point between China. Other scholars, disagree with this identification, though it remains one of four most probable sites for the Stone Tower. In pre-Islamic and early Islamic times, the town and the province were known as Chach; the Shahnameh of Ferdowsi refers to the city as Chach. The principality of Chach had a square citadel built around the 5th to 3rd centuries BC, some 8 kilometres south of the Syr Darya River. By the 7th century AD, Chach had more than 30 towns and a network of over 50 canals, forming a trade center between the Sogdians and Turkic nomads; the Buddhist monk Xuanzang, who travelled from China to India through Central Asia, mentioned the name of the city as Zhěshí.
After the 16th century, the name evolved from Chachkand/Chashkand to Tashkand. The modern spelling of "Tashkent" reflects Russian 20th-century Soviet influence; the city was destroyed by Genghis Khan in 1219 and lost much of its population as a result of the Mongols' destruction of the Khwarezmid Empire in 1220. Under the Timurid and subsequent Shaybanid dynasties, the city's population and culture revived as a prominent strategic center of scholarship and trade along the Silk Road. In 1809, Tashkent was annexed to the Khanate of Kokand. At the time, Tashkent had a population of around 100,000 and was considered the richest city in Central Asia, it prospered through trade with Russia but chafed under Kokand’s high taxes. The Tashkent clergy favored the clergy of Bukhara over that of Kokand. However, before the Emir of Bukhara could capitalize on this discontent, the Russian army arrived. In May 1865, Mikhail Grigorevich Chernyayev, acting against the direct orders of the tsar and outnumbered at least 15-1, staged a daring night attack against a city with a wall 25 kilometres long with 11 gates and 30,000 defenders.
While a small contingent staged a diversionary attack, the main force penetrated the walls, led by a Russian Orthodox priest armed only with a crucifix. Although the defense was stiff, the Russians captured the city after two days of heavy fighting and the loss of only 25 dead as opposed to several thousand of the defenders. Chernyayev dubbed the "Lion of Tashkent" by city elders, staged a "hearts-and-minds" campaign to win the population over, he abolished taxes for a year, rode unarmed through the streets and bazaars meeting common people, appointed himself "Military Governor of Tashkent", recommending to Tsar Alexander II that the city is made an independent khanate under Russian protection. The Tsar liberally rewarded Chernyayev and his men with medals and bonuses, but regarded the impulsive general as a "loose cannon", soon replaced him with General Konstantin Petrovich von Kaufman. Far from being granted independence, Tashkent became the capital of the new territory of Russian Turkistan, with Kaufman as first Governor-General.
A cantonment and Russian settlement were built across the Ankhor Canal from the old city, Russian settlers and merchants poured in. Tashkent was a center of espionage in the Great Game rivalry between Russia and the United Kingdom over Central Asia. T
The Latin or Roman alphabet is the writing system used by the ancient Romans to write the Latin language. Due to its use in writing Germanic and other languages first in Europe and in other parts of the world, due to its use in Romanizing writing of other languages, it has become widespread, it is used in China and has been adopted by Baltic and some Slavic states. The Latin alphabet evolved from the visually similar Cumaean Greek version of the Greek alphabet, itself descended from the Phoenician abjad, which in turn derived from Egyptian hieroglyphics; the Etruscans, who ruled early Rome, adopted the Cumaean Greek alphabet, modified over time to become the Etruscan alphabet, in turn adopted and further modified by the Romans to produce the Latin alphabet. During the Middle Ages, the Latin alphabet was used for writing Romance languages, which are direct descendants of Latin, as well as Celtic, Germanic and some Slavic languages. With the age of colonialism and Christian evangelism, the Latin script spread beyond Europe, coming into use for writing indigenous American, Austronesian and African languages.
More linguists have tended to prefer the Latin script or the International Phonetic Alphabet when transcribing or creating written standards for non-European languages, such as the African reference alphabet. The term Latin alphabet may refer to either the alphabet used to write Latin, or other alphabets based on the Latin script, the basic set of letters common to the various alphabets descended from the classical Latin alphabet, such as the English alphabet; these Latin-script alphabets may discard letters, like the Rotokas alphabet, or add new letters, like the Danish and Norwegian alphabets. Letter shapes have evolved over the centuries, including the development in Medieval Latin of lower-case, forms which did not exist in the Classical period alphabet. English is the only major modern European language requiring no diacritics for native words, it is believed that the Romans adopted the Cumae alphabet, a variant of the Greek alphabet, in the 7th century BC from Cumae, a Greek colony in Southern Italy.
The Ancient Greek alphabet was in turn based upon the Phoenician abjad. From the Cumae alphabet, the Etruscan alphabet was derived and the Romans adopted 21 of the original 27 Etruscan letters: Latin included 21 different characters; the letter ⟨C⟩ was the western form of the Greek gamma, but it was used for the sounds /ɡ/ and /k/ alike under the influence of Etruscan, which might have lacked any voiced plosives. During the 3rd century BC, the letter ⟨Z⟩ – unneeded to write Latin properly – was replaced with the new letter ⟨G⟩, a ⟨C⟩ modified with a small vertical stroke, which took its place in the alphabet. From on, ⟨G⟩ represented the voiced plosive /ɡ/, while ⟨C⟩ was reserved for the voiceless plosive /k/; the letter ⟨K⟩ was used only in a small number of words such as Kalendae interchangeably with ⟨C⟩. After the Roman conquest of Greece in the 1st century BC, Latin adopted the Greek letters ⟨Y⟩ and ⟨Z⟩ to write Greek loanwords, placing them at the end of the alphabet. An attempt by the emperor Claudius to introduce three additional letters.
Thus it was during the classical Latin period that the Latin alphabet contained 23 letters: The Latin names of some of these letters are disputed. In general the Romans did not use the traditional names as in Greek: the names of the plosives were formed by adding /eː/ to their sound and the names of the continuants consisted either of the bare sound, or the sound preceded by /e/; the letter ⟨Y⟩ when introduced was called "hy" /hyː/ as in Greek, the name upsilon not being in use yet, but this was changed to "i Graeca" as Latin speakers had difficulty distinguishing its foreign sound /y/ from /i/. ⟨ Z ⟩ was given zeta. This scheme has continued to be used by most modern European languages that have adopted the Latin alphabet. For the Latin sounds represented by the various letters see Latin pronunciation. Diacritics were not used, but they did occur sometimes, the most common being the apex used to mark long vowels, which had sometimes been written doubled. However, in place of taking an apex, the letter i was written taller: ⟨á é ꟾ ó v́⟩.
For example, what is today transcribed Lūciī a fīliī was written ⟨lv́ciꟾ·a·fꟾliꟾ⟩ in the inscription depicted. The primary mark of punctuation was the interpunct, used as a word divider, though it fell out of use after 200 AD. Old Roman cursive script called majuscule cursive and capitalis cursive, was the everyday form of handwriting used for writing letters, by merchants writing business accounts, by schoolchildren learning the Latin alphabet, emperors issuing commands. A more formal style of writing was based on Roman square capitals, but cursive was used for quicker, informal writing, it was most c
The Soviet ruble was the currency of the Union of Soviet Socialist Republics. One ruble was divided into 100 kopeks. Many of the ruble designs were created by Ivan Dubasov; the production of Soviet rubles was the responsibility of the Federal State Unitary Enterprise, or Goznak, in charge of the printing of and materials production for banknotes and the minting of coins in Moscow and Leningrad. In addition to regular currency, some other currency units were used, such as several forms of convertible ruble, transferable ruble, clearing ruble, Vneshtorgbank cheque, etc.. In 1991, after the breakup of the USSR, the Soviet ruble continued to be used in the post-Soviet states, forming a "ruble zone", until it was replaced with the Russian ruble by 1993; the word "ruble" is derived from rubit', i.e. to chop. A "ruble" was a piece of a certain weight chopped off a silver ingot, hence the name; the word kopek, copeck, or kopeyka is a diminutive form of the Russian kop'yo —a spear. The reason for this is that a horseman armed with a spear was stamped on one of the faces of the coin.
The word "kopeyka" is a direct translation of old Lithuanian money "kapa" that has the same meaning "to chop" in Lithuanian as does "ruble" in Russian. For many centuries, around 500,000 km2 of contemporary Russia were Lithuanian lands inhabited by Lithuanians, in this region Lithuanian "kapa" circulated. After the annexation of these lands by Muscovy, a modified version of this Lithuanian word came to be used by Russia as the hundredth fraction of the ruble; the Soviet currency had its own name in all Languages of the Soviet Union different from its Russian designation. All banknotes had the currency name and their nominal printed in the languages of every Soviet Republic; this naming is preserved in modern Russia. The current names of several currencies of Central Asia are the local names of the ruble. Finnish last appeared on 1947 banknotes since the Karelo-Finnish SSR was dissolved in 1956; the name of the currency in the languages of the 15 republics, in the order they appeared in the banknotes: Note that the scripts for Uzbek and Turkmen have switched from Cyrillic to Latin since the breakup of the Soviet Union.
Moldovan is once again referred to as Romanian. These 15 names derive from four roots: Slavic verb рубить, rubit', "chop" Turkic root som, "pure" Latin monēta, "coin" Old Ruthenian karbuvaty, "carve" The first ruble issued for the Socialist government was a preliminary issue still based on the previous issue of the ruble prior to the Russian Revolution of 1917, they are all in banknote form and started their issue in 1919. At this time other issues were made by other governing bodies. Denominations are as follows: 1, 2, 3, 5, 10, 15, 25, 50, 60, 100, 250, 500, 1,000, 5,000, 10,000, 25,000, 50,000, 100,000. Short term treasury certificate were issued to supplement banknote issue in 1 million, 5 million, 10 million rubles; these issue was printed in various fashions, as inflation crept up the security features were few and some were printed on one side, as was the case for the German inflationary notes. In 1918, state credit notes were introduced by the R. S. F. S. R. for 1, 3, 5, 10, 25, 50, 100, 250, 500, 1,000, 5,000 and 10,000 rubles.
These were followed in 1919 by currency notes for 1, 2, 3, 15, 20, 60, 100, 250, 500, 1000, 5000 and 10,000 rubles. In 1921, currency note denominations of 5, 50, 25,000, 50,000, 100,000, 1,000,000, 5,000,000 and 10,000,000 rubles were added. In 1922, the first of several redenominations took place, at a rate of 1 "new" ruble for 10,000 "old" rubles; the chervonets was introduced in 1922. This currency was short-lived. Only state currency notes were issued for this currency, in denominations of 1, 3, 5, 10, 25, 50, 100, 250, 500, 1,000, 5,000 and 10,000 rubles. A second redenomination took place in 1923, at a rate of 100 to 1. Again, only paper money was issued. During the lifetime of this currency, the first money of the Soviet Union was issued; this currency was short lived, not lasting too long after Vladimir Lenin's death, but lasting over two months longer than its predecessor. The first coinage after the Russian civil war was minted in 1921–1923 with silver coins in denominations of 10, 15, 20 and 50 kopecks and 1 ruble.
Gold chervonets were issued in 1923. These coins bore the emblem and legends of the RSFSR and depicted the famous slogan, "Workers of the world, Unite!". The 10, 15, 20 kopecks were minted with a purity of 50% silver while the ruble and half-ruble were minted with a purity of 90% silver; the chervonetz was 90% gold. These coins would continue to circulate after the RSFSR was consolidated into the USSR with other Soviet Republics until the discontinuation of silver coinage in 1931; as with the previous currency, only state currency notes were issued, in denominations of 50 kopeks, 1, 5, 10, 25, 50, 100, 250, 500, 1,000, 5,000 and 10,000 rubles. In early 1924, just before the next redenomination, the first paper money was issued in the name of the USSR, featuring the state emblem with 6 bands around the wheat, representing the languages of the 4 constituent republics of the Union: Russian SFS
The Registan was the heart of the ancient city of Samarkand of the Timurid dynasty, now in Uzbekistan. The name Rēgistan means "Sandy place" or "desert" in Persian; the Registan was a public square, where people gathered to hear royal proclamations, heralded by blasts on enormous copper pipes called dzharchis - and a place of public executions. It is framed by three madrasahs of distinctive Islamic architecture; the three madrasahs of the Registan are: the Ulugh Beg Madrasah, the Tilya-Kori Madrasah and the Sher-Dor Madrasah. Madrasah is an Arabic term meaning school; the Ulugh Beg Madrasah, built by Ulugh Beg during the Timurid Empire era of Timur—Tamerlane, has an imposing iwan with a lancet-arch pishtaq or portal facing the square. The corners are flanked by high minarets; the mosaic panel over the iwan's entrance arch is decorated by geometrical stylized ornaments. The square courtyard includes a mosque and lecture rooms, is fringed by the dormitory cells in which students lived. There are deep galleries along the axes.
The Ulugh Beg Madrasah was a two-storied building with four domed darskhonas at the corners. The Ulugh Beg Madrasah was one of the best clergy universities of the Muslim Orient in the 15th Century CE. Abdul-Rahman Jami, the great Persian poet, mystic and philosopher studied at the madrasah. Ulugh Beg himself gave lectures there. During Ulugh Beg's government the madrasah was a centre of learning In the 17th century the ruler of Samarkand, Yalangtush Bakhodur, ordered the construction of the Sher-Dor and Tillya-Kori madrasahs; the tiger mosaics with a rising sun on their back, on the face of each madrassa arch are interesting, in that they flout the ban in Islam of the depiction of living beings on religious buildings as they represent the more ancient Persian Mithraic religious motifs. There is a bit of Zoroastrianism influence in the architecture. Ten years the Tilya-Kori Madrasah was built, it was not only a residential college for students, but played the role of grand masjid. It has a two-storied main facade and a vast courtyard fringed by dormitory cells, with four galleries along the axes.
The mosque building is situated in the western section of the courtyard. The main hall of the mosque is abundantly gilded. To the east of the Tilya-Kori Madrasah, the mausoleum of Shaybanids is located; the real founder of Shaybanid power was Muhammad Shaybani - grandson of Abu'l Khair. In 1500, with the backing of the Chaghataite Khanate based in Tashkent, Muhammad Shaybani conquered Samarkand and Bukhara from their last Timurid rulers; the founder of the dynasty turned on his benefactors and in 1503 took Tashkent. He captured Khiva in 1506 and in 1507 he swooped down on Merv, eastern Persia, western Afghanistan; the Shaybanids stopped the advance of the Safavids. Muhammad Shaybani was a leader of nomadic Uzbeks. During the ensuing years they settled down in oases of Central Asia; the Uzbek invasion of the 15th Century CE was the last component of today's Uzbek nation ethnogeny. The ancient trading dome Chorsu is situated right behind the Sher-Dor. Bibi-Khanym Mosque Gur-e Amir Shah-i-Zinda Timurid dynasty Tourism in Uzbekistan Media related to Registan at Wikimedia Commons
Brass is an alloy of copper and zinc, in proportions which can be varied to achieve varying mechanical and electrical properties. It is a substitutional alloy: atoms of the two constituents may replace each other within the same crystal structure. Bronze is an alloy containing copper, but instead of zinc it has tin. Both bronze and brass may include small proportions of a range of other elements including arsenic, phosphorus, aluminium and silicon; the distinction is historical. Modern practice in museums and archaeology avoids both terms for historical objects in favour of the all-embracing "copper alloy". Brass is used for decoration for its bright gold-like appearance, it is used in zippers. Brass is used in situations in which it is important that sparks not be struck, such as in fittings and tools used near flammable or explosive materials. Brass has higher malleability than zinc; the low melting point of brass and its flow characteristics make it a easy material to cast. By varying the proportions of copper and zinc, the properties of the brass can be changed, allowing hard and soft brasses.
The density of brass is 8.4 to 8.73 grams per cubic centimetre. Today 90% of all brass alloys are recycled; because brass is not ferromagnetic, it can be separated from ferrous scrap by passing the scrap near a powerful magnet. Brass scrap is transported to the foundry where it is melted and recast into billets. Billets are extruded into the desired form and size; the general softness of brass means that it can be machined without the use of cutting fluid, though there are exceptions to this. Aluminium makes brass more corrosion-resistant. Aluminium causes a beneficial hard layer of aluminium oxide to be formed on the surface, thin and self-healing. Tin has a similar effect and finds its use in seawater applications. Combinations of iron, aluminium and manganese make brass wear and tear resistant. To enhance the machinability of brass, lead is added in concentrations of around 2%. Since lead has a lower melting point than the other constituents of the brass, it tends to migrate towards the grain boundaries in the form of globules as it cools from casting.
The pattern the globules form on the surface of the brass increases the available lead surface area which in turn affects the degree of leaching. In addition, cutting operations can smear the lead globules over the surface; these effects can lead to significant lead leaching from brasses of comparatively low lead content. In October 1999 the California State Attorney General sued 13 key manufacturers and distributors over lead content. In laboratory tests, state researchers found the average brass key, new or old, exceeded the California Proposition 65 limits by an average factor of 19, assuming handling twice a day. In April 2001 manufacturers agreed to reduce lead content to 1.5%, or face a requirement to warn consumers about lead content. Keys plated with other metals are not affected by the settlement, may continue to use brass alloys with higher percentage of lead content. In California, lead-free materials must be used for "each component that comes into contact with the wetted surface of pipes and pipe fittings, plumbing fittings and fixtures."
On January 1, 2010, the maximum amount of lead in "lead-free brass" in California was reduced from 4% to 0.25% lead. The so-called dezincification resistant brasses, sometimes referred to as CR brasses, are used where there is a large corrosion risk and where normal brasses do not meet the standards. Applications with high water temperatures, chlorides present, or deviating water qualities play a role. DZR-brass is excellent in water boiler systems; this brass alloy must be produced with great care, with special attention placed on a balanced composition and proper production temperatures and parameters to avoid long-term failures. The high malleability and workability good resistance to corrosion, traditionally attributed acoustic properties of brass, have made it the usual metal of choice for construction of musical instruments whose acoustic resonators consist of long narrow tubing folded or coiled for compactness. Collectively known as brass instruments, these include the trombone, trumpet, baritone horn, tenor horn, French horn, many other "horns", many in variously-sized families, such as the saxhorns.
Other wind instruments may be constructed of brass or other metals, indeed most modern student-model flutes and piccolos are made of some variety of brass a cupronickel alloy similar to nickel silver/German silver. Clarinets low clarinets such as the contrabass and subcontrabass, are sometimes made of metal because of limited supplies of the dense, fine-grained tropical hardwoods traditionally preferred for smaller woodwinds. For the same reason, some low clarinets and contrabassoons feature a hybrid construction, with long, straight sections of wood, curved joints, and/or bell of metal; the use of metal avoids the risks of exposing wooden instruments to changes in temperature or humid
Central Asia stretches from the Caspian Sea in the west to China in the east and from Afghanistan in the south to Russia in the north. The region consists of the former Soviet republics of Kazakhstan, Tajikistan and Uzbekistan, it is colloquially referred to as "the stans" as the countries considered to be within the region all have names ending with the Persian suffix "-stan", meaning "land of". Central Asia has a population of about 72 million, consisting of five republics: Kazakhstan, Tajikistan and Uzbekistan. Afghanistan, a part of South Asia, is sometimes included in Central Asia. Central Asia has been tied to its nomadic peoples and the Silk Road, it has acted as a crossroads for the movement of people and ideas between Europe, Western Asia, South Asia, East Asia. The Silk Road connected Muslim lands with the people of Europe and China; this crossroads position has intensified the conflict between tribalism and traditionalism and modernization. In pre-Islamic and early Islamic times, Central Asia was predominantly Iranian, populated by Eastern Iranian-speaking Bactrians, Sogdians and the semi-nomadic Scythians and Dahae.
After expansion by Turkic peoples, Central Asia became the homeland for the Kazakhs, Tatars, Turkmen and Uyghurs. From the mid-19th century until the end of the 20th century, most of Central Asia was part of the Russian Empire and the Soviet Union, both Slavic-majority countries, the five former Soviet "-stans" are still home to about 7 million ethnic Russians and 500,000 Ukrainians; the idea of Central Asia as a distinct region of the world was introduced in 1843 by the geographer Alexander von Humboldt. The borders of Central Asia are subject to multiple definitions. Built political geography and geoculture are two significant parameters used in the scholarly literature about the definitions of the Central Asia; the most limited definition was the official one of the Soviet Union, which defined Middle Asia as consisting of Uzbekistan, Turkmenistan and Kyrgyzstan, hence omitting Kazakhstan. This definition was often used outside the USSR during this period. However, the Russian culture has two distinct terms: Средняя Азия and Центральная Азия.
Soon after independence, the leaders of the four former Soviet Central Asian Republics met in Tashkent and declared that the definition of Central Asia should include Kazakhstan as well as the original four included by the Soviets. Since this has become the most common definition of Central Asia; the UNESCO History of the Civilizations of Central Asia, published in 1992, defines the region as "Afghanistan, northeastern Iran and central Pakistan, northern India, western China and the former Soviet Central Asian republics."An alternative method is to define the region based on ethnicity, in particular, areas populated by Eastern Turkic, Eastern Iranian, or Mongolian peoples. These areas include Xinjiang Uyghur Autonomous Region, the Turkic regions of southern Siberia, the five republics, Afghan Turkestan. Afghanistan as a whole, the northern and western areas of Pakistan and the Kashmir Valley of India may be included; the Tibetans and Ladakhi are included. Insofar, most of the mentioned peoples are considered the "indigenous" peoples of the vast region.
Central Asia is sometimes referred to as Turkestan. There are several places that claim to be the geographic center of Asia, for example Kyzyl, the capital of Tuva in the Russian Federation, a village 200 miles north of Ürümqi, the capital of the Xinjiang region of China. Central Asia is an large region of varied geography, including high passes and mountains, vast deserts, treeless, grassy steppes; the vast steppe areas of Central Asia are considered together with the steppes of Eastern Europe as a homogeneous geographical zone known as the Eurasian Steppe. Much of the land of Central Asia is too rugged for farming; the Gobi desert extends from the foot of the Pamirs, 77° E, to the Great Khingan Mountains, 116°–118° E. Central Asia has the following geographic extremes: The world's northernmost desert, at Buurug Deliin Els, Mongolia, 50°18' N; the Northern Hemisphere's southernmost permafrost, at Erdenetsogt sum, Mongolia, 46°17' N. The world's shortest distance between non-frozen desert and permafrost: 770 km.
The Eurasian pole of inaccessibility. A majority of the people earn a living by herding livestock. Industrial activity centers in the region's cities. Major rivers of the region include the Amu Darya, the Syr Darya, the Hari River and the Murghab River. Major bodies of water include the Aral Sea and Lake Balkhash, both of which are part of the huge west-central Asian endorheic basin that includes the Caspian Sea. Both of these bodies of water have shrunk in recent decades due to diversion of water from rivers that feed them for irrigation and industrial purposes. Water is an valuable resource in arid Central Asia and can lead to rather significant international disputes. Central Asia is bounded on the north by the forests of Siberia; the northern half of Cent