An observatory is a location used for observing terrestrial or celestial events. Astronomy, climatology/meteorology, geophysical and volcanology are examples of disciplines for which observatories have been constructed. Observatories were as simple as containing an astronomical sextant or Stonehenge. Astronomical observatories are divided into four categories: space-based, ground-based, underground-based. Ground-based observatories, located on the surface of Earth, are used to make observations in the radio and visible light portions of the electromagnetic spectrum. Most optical telescopes are housed within a dome or similar structure, to protect the delicate instruments from the elements. Telescope domes have a slit or other opening in the roof that can be opened during observing, closed when the telescope is not in use. In most cases, the entire upper portion of the telescope dome can be rotated to allow the instrument to observe different sections of the night sky. Radio telescopes do not have domes.
For optical telescopes, most ground-based observatories are located far from major centers of population, to avoid the effects of light pollution. The ideal locations for modern observatories are sites that have dark skies, a large percentage of clear nights per year, dry air, are at high elevations. At high elevations, the Earth's atmosphere is thinner, thereby minimizing the effects of atmospheric turbulence and resulting in better astronomical "seeing". Sites that meet the above criteria for modern observatories include the southwestern United States, Canary Islands, the Andes, high mountains in Mexico such as Sierra Negra. A newly emerging site which should be added to this list is Mount Gargash. With an elevation of 3600 m above sea level, it is the home to the Iranian National Observatory and its 3.4m INO340 telescope. Major optical observatories include Mauna Kea Observatory and Kitt Peak National Observatory in the US, Roque de los Muchachos Observatory and Calar Alto Observatory in Spain, Paranal Observatory in Chile.
Specific research study performed in 2009 shows that the best possible location for ground-based observatory on Earth is Ridge A — a place in the central part of Eastern Antarctica. This location provides the least atmospheric disturbances and best visibility. Beginning in 1930s, radio telescopes have been built for use in the field of radio astronomy to observe the Universe in the radio portion of the electromagnetic spectrum; such an instrument, or collection of instruments, with supporting facilities such as control centres, visitor housing, data reduction centers, and/or maintenance facilities are called radio observatories. Radio observatories are located far from major population centers to avoid electromagnetic interference from radio, TV, other EMI emitting devices, but unlike optical observatories, radio observatories can be placed in valleys for further EMI shielding; some of the world's major radio observatories include the Socorro, in New Mexico, United States, Jodrell Bank in the UK, Arecibo in Puerto Rico, Parkes in New South Wales and Chajnantor in Chile.
Since the mid-20th century, a number of astronomical observatories have been constructed at high altitudes, above 4,000–5,000 m. The largest and most notable of these is the Mauna Kea Observatory, located near the summit of a 4,205 m volcano in Hawaiʻi; the Chacaltaya Astrophysical Observatory in Bolivia, at 5,230 m, was the world's highest permanent astronomical observatory from the time of its construction during the 1940s until 2009. It has now been surpassed by the new University of Tokyo Atacama Observatory, an optical-infrared telescope on a remote 5,640 m mountaintop in the Atacama Desert of Chile; the oldest proto-observatories, in the sense of a private observation post, Wurdi Youang, Australia Zorats Karer, Armenia Loughcrew, Ireland Newgrange, Ireland Stonehenge, Great Britain Quito Astronomical Observatory, located 12 minutes south of the Equator in Quito, Ecuador. Chankillo, Peru El Caracol, Mexico Abu Simbel, Egypt Kokino, Republic of Macedonia Observatory at Rhodes, Greece Goseck circle, Germany Ujjain, India Arkaim, Russia Cheomseongdae, South Korea Angkor Wat, CambodiaThe oldest true observatories, in the sense of a specialized research institute, include: 825 AD: Al-Shammisiyyah observatory, Iraq 869: Mahodayapuram Observatory, India 1259: Maragheh observatory, Iran 1276: Gaocheng Astronomical Observatory, China 1420: Ulugh Beg Observatory, Uzbekistan 1442: Beijing Ancient Observatory, China 1577: Constantinople Observatory of Taqi ad-Din, Turkey 1580: Uraniborg, Denmark 1581: Stjerneborg, Denmark 1642: Panzano Observatory, Italy 1642: Round Tower, Denmark 1633: Leiden Observatory, Netherlands 1667: Paris Observatory, France 1675: Royal Greenwich Observatory, England 1695: Sukharev Tower, Russia 1711: Berlin Observatory, Germany 1724: Jantar Mantar, India 1753: Stockholm Observatory, Sweden 1753: Vilnius University Observatory, Lithuania 1753: Navy Royal Institute and Observatory, Spain 1759: Trieste Observatory, Italy 1757: Macfarlane Observatory, Scotland 1759: Turin Observatory, Italy 1764: Brera Astronomical Observatory, Italy 1765: Mohr Observatory, Indonesia 1774: Vatican Observatory, Vatican 1785: Dunsink Observatory, Ireland 1786: Madras Observatory, India 1789: Armagh Observatory, Northern Ireland 1790: Real Observatorio de Madrid, Spain, 1803: National Astronomical Observatory, Bogotá, Colombia.
1811: Tartu Old Observatory, Estonia 1812: Astronomical Observatory of Capodimonte, Italy 1830/1842: Depot of Charts & Instruments
Administrative divisions of Ukraine
Ukraine is divided into several levels of territorial entities. On the first level there are 27 regions: 24 oblasts, one autonomous republic, two "cities with special status". Following the 2014 Crimean crisis and Sevastopol became de facto administrated by the Russian Federation, which claims them as the Republic of Crimea and the federal city of Sevastopol; the international community recognises them as being Ukrainian territory. The administrative division in Ukraine was directly inherited from the local republican administration of the Soviet Union, the Ukrainian Soviet Socialist Republic, has not changed since the middle of the 20th century, it is somewhat complex as beside having several levels of a territorial subdivision, it has a classification for various populated places cities. According to the Article 133 of Constitution of Ukraine, "the system of the administrative and territorial structure of Ukraine is composed of the Autonomous Republic of Crimea, districts, districts in city and villages."
Note, that although certain types of subdivision are not mentioned in Constitution of Ukraine, they are mentioned for regional composition. For disambiguation regular raions are sometimes denoted as rural to distinguish them from raions in city. Ukraine's administrative divisions are divided as follows: By geographical characteristics the units are divided on regions and places of settlement. By their status they can be administrative-territorial units, self-governed territorial units; the autonomous republic has a unique status of territorial autonomy, while districts in cities combine both characteristics of administrative territorial as well as self-governed territorial units. By position in the system of administrative division of Ukraine, the units divided into territorial units of prime level, of middle level, of higher level. Administrative division has changed because some territories are not under the control of the government. For example, Sievierodonetsk has become the new central regional center.
Regions, districts are governed by a state administration, a chief of, appointed by the president after a nomination by the cabinet of ministers. Crimea has its own cabinet of ministers, however the state administration is represented by the office of the Presidential Representative of Ukraine. A basic and the lowest level of administrative division is a settlement, governed by a local council. Cities as a settlement always carry a special status within a region and have their own form of self-administration and some may consist of their own city's districts. City municipalities are governed by a city council; some smaller cities and rural localities may be under control of city municipalities based on larger cities. Towns as well as villages are not controlled by state administration and are self-governed by either a town council or a village council within the limits of the Constitution and the laws of Ukraine. Village councils may carry a combined jurisdiction which may include several hamlets.
Unlike villages, each town council always has a separate jurisdiction which may be part of bigger city's council. Hamlet is governed by a village council of nearby village. Ukraine is divided into 3 main administrative divisions: oblast and council. Note, settlements such as cities do not necessary constitute the basic level of the Ukrainian administrative territorial system. For that purpose cities are categorized into own three categories that correspond to each level of subdivisions. Cities with special status and regional significance beside being divided into special districts in city may include smaller cities, and/or villages. Please, note that the settlement's population size is not the only factor for its status; the final decision on status change is carried out by the Ukrainian parliament. The following table is based on the 2001 Ukrainian Census; the following numbers are based on the 2001 Ukrainian Census. Top level:Autonomous Republic of Crimea Oblasts of Ukraine Cities with special status: Kiev and Sevastopol Middle level: Raions Cities of oblast significance City districts Primary level: Cities of raion significance Urban-type settlements Villages Rural-type settlements Total cities: 454, an increase of 20 compared with the 1989 census.
Before the introduction of oblasts in 1932, Ukraine comprised 40 okruhas, which had replaced the former Russian Imperial guberniya subdivisions. In 1932 the territory of the Ukrainian SSR was re-established based on oblasts. Excluded in the administrative changes was Western Ukraine, which at that time formed part of the Second Polish Republic and shared in the Polish form of administrative division based on voivodeships. In the post-World War II period, the Ukrainian Soviet Socialist Republic consisted of 25 oblasts and two cities with special status. After the fall of the Soviet Union in 1991, Crimea obtained the status of an autonomous republic wit
Republic of Crimea
The Republic of Crimea is a federal subject of Russia, located on the Crimean Peninsula. The capital city and largest city within the republic is Simferopol, the second largest city of Crimea, behind the federal city of Sevastopol. At the last census the republic had a population of 1,891,465. In March 2014, following the takeover of Crimea by pro-Russian separatists and the Russian Armed Forces, an unconstitutional referendum was held on the issue of reunification with Russia, which official results and opinion polls indicated was supported by a large majority of Crimeans; the official result was. Russia annexed the Republic of Crimea and Sevastopol as federal subjects of Russia. While Russia and 21 other UN member states either recognize Crimea as part of the Russian Federation or have expressed sympathy for the Russian authorities regarding the matter, Ukraine continues to claim Crimea as an integral part of its territory as the Autonomous Republic of Crimea, supported by most foreign governments, various United Nations General Assembly resolutions.
In 1792, under the Russian Empress Catherine the Great, Crimea was ceded to Russia by the Ottoman Empire under the Treaty of Jassy, which formally ended the Russo-Turkish war of 1787-1792. From 1802, it constituted a southern part of the Taurida Governorate of the Russian Empire until the collapse thereof in 1917. During the Russian Civil War Crimea changed hands multiple times, being inter alia the last territory held by the White Russian government in the European part of Russia in 1920, became an autonomous republic within Russian Soviet Federative Socialist Republic in 1921. During World War II, in 1944, the central Soviet authorities deported the Crimean Tatars for alleged collaboration with the Nazi occupation regime. In 1954, the Presidium of the USSR Supreme Soviet transferred the region from the Russian Soviet Federative Socialist Republic to the Ukrainian Soviet Socialist Republic, another constituent republic of the USSR a centralised state, wherein borders between constituent republics was a technical issue of administration, despite the fact that Ukraine was a separate member of the UN.
The Crimean Tatars were allowed to return to Crimea in the mid-1980s under perestroika. With the collapse of the Soviet Union, Crimea became part of the newly independent Ukraine, which led to tensions between Russia and Ukraine. With the Black Sea Fleet based on the peninsula, worries of armed skirmishes were raised. Crimean Tatars began resettling in Crimea. Ukraine restored Crimea's autonomous status in 1991. Crimea's autonomous status was re-affirmed in 1996 with the ratification of Ukraine's current constitution, which designated Crimea as the "Autonomous Republic of Crimea", but an "inseparable constituent part of Ukraine". On 11 March 2014, the Crimean parliament and the Sevastopol City Council jointly issued a letter of intent to unilaterally declare independence from Ukraine in the event of a'Yes' vote in the referendum to join the region to Russia, to be held on 16 March; the document mentioned Kosovo as a precedent in the lead part. The referendum on the status of Crimea allowed citizens to vote on whether Crimea should apply to join Russia as a federal subject of the Russian Federation, or restore the 1992 Crimean constitution and Crimea's status as a part of Ukraine.
The available choices did not include keeping the status quo of Crimea and Sevastopol as they were at the time the referendum was held. On 16 March 2014, according to statements of organizers of Crimean status referendum, a large majority voted in favour of independence of Crimea from Ukraine and joining Russia as a federal subject; the referendum was not recognized by most of the international community and the reported results were disputed by numerous independent observers. The BBC reported. Reports from the UN criticised the circumstances surrounding the referendum the presence of paramilitaries, self-defence groups and unidentifiable soldiers; the European Union, Canada and the United States condemned the vote as illegal. After the referendum, Crimean lawmakers formally voted both to secede from Ukraine and applied for their admission into Russia; the Sevastopol City Council, requested the port's separate admission as a federal city. On 18 March 2014, the self-proclaimed independent Republic of Crimea signed a treaty of accession to the Russian Federation.
The accession was granted but separately for each the former regions that composed it: one accession for the Autonomous Republic of Crimea as the Republic of Crimea— the same name as the short-lived self-proclaimed independent republic - and another accession for Sevastopol as a federal city. The accession was only recognised internationally by a few states with most regarding the action as illegal. Though Ukraine refused to accept the annexation, the Ukrainian military began to withdraw from Crimea on 19 March. A transition period, during which both parties to the accession treaty were to resolve the issues of integration of the new subjects "in the economic, financial and legal system of the Russian Federation", was set to last until 1 January 2015'The integration process started within days: on 24 March the Russian ruble went int
Autonomous Republic of Crimea
The Autonomous Republic of Crimea is, de jure, an autonomous republic of Ukraine encompassing most of Crimea, though, de facto, it was annexed by Russia and incorporated as a Russian federal subject - the Republic of Crimea - in 2014. Crimea was under Russian control from 1783 until 1954, when it was transferred, within the USSR, to the Ukrainian SSR. Following a referendum on 20 January 1991, the results of the pro-independence referendum were discarded and it became an autonomous republic within the Ukrainian SSR; when the Soviet Union collapsed in 1991 and Ukraine became an independent country, Crimea remained part of the newly independent Ukraine. In February 2014, following the 2014 Ukrainian revolution that ousted the Ukrainian President, Viktor Yanukovych, pro-Russian separatists and Russian Armed Forces took over the territory. A controversial Crimea-wide referendum, unconstitutional under the Ukrainian and Crimean constitutions, was held on the issue of reunification with Russia which official results indicated was supported by a large majority of Crimeans.
Russia formally annexed Crimea on 18 March 2014, although the annexation is not recognized internationally. Crimea first came under Russian control in 1783 when the Crimean Khanate was annexed by the Russian Empire and this was formally recognised in 1792 when the peninsula was ceded to Russia by the Ottoman Empire under the Treaty of Jassy. Thereafter, Russian rule in Crimea spanned a period of 171 years, punctuated by short periods during political upheavals and wars, which ended on 19 February 1954 when the Presidium of the Supreme Soviet issued a decree transferring the Crimean Oblast from the Russian Soviet Federative Socialist Republic to the Ukrainian Soviet Socialist Republic, within the Soviet Union on the basis of "the integral character of the economy, the territorial proximity and the close economic and cultural ties between the Crimea Province and the Ukrainian SSR.":Following a referendum on 20 January 1991 in which over 94% backed the proposal, the Crimean Oblast was upgraded to the status of an autonomous republic on 12 February 1991 by the Supreme Soviet of the Ukrainian SSR.
When the Soviet Union collapsed and Ukraine became an independent country, Crimea remained a republic within the newly independent Ukraine leading to tensions between Russia and Ukraine as the Black Sea Fleet was based on the peninsula. On 26 February 1992, the Crimean parliament renamed the ASSR the Republic of Crimea, it proclaimed self-government on 5 May 1992 with a referendum, for approval, planned for the August and passed the first Crimean constitution. The following day, the same parliament inserted a new sentence into this constitution that declared that Crimea was part of Ukraine and on 19 May, it annulled its proclamation of self-government after the Ukrainian government expanded on the republic's extensive autonomous status; the following year, on 14 October 1993, the Crimean parliament established the post of President of Crimea. On 17 March 1995, the parliament of Ukraine abolished the Crimean Constitution of 1992, all the laws and decrees contradicting those of Kiev, removed Yuriy Meshkov, the President of Crimea, along with the office itself.
After an interim constitution, the 1998 Constitution of the Autonomous Republic of Crimea was put into effect, changing the territory's name to the Autonomous Republic of Crimea. Following the ratification of the May 1997 Russian–Ukrainian Friendship Treaty, in which Russia recognized Ukraine's borders and sovereignty over Crimea, international tensions eased. However, in 2006, anti-NATO protests broke out on the peninsula. In September 2008, the Ukrainian Foreign Minister Volodymyr Ohryzko accused Russia of giving out Russian passports to the population in Crimea and described it as a "real problem" given Russia's declared policy of military intervention abroad to protect Russian citizens. On 24 August 2009, anti-Ukrainian demonstrations were held in Crimea by ethnic Russian residents. Sergei Tsekov said that he hoped that Russia would treat Crimea the same way as it had treated South Ossetia and Abkhazia; the 2010 Ukrainian–Russian Naval Base for Natural Gas treaty extended Russia's lease on naval facilities in Crimea until 2042, with optional five-year renewals.
Crimea voted for the pro-Russian Ukrainian President Viktor Yanukovych and his Party of Regions in presidential and parliamentary elections, his ousting on 22 February 2014 during the 2014 Ukrainian revolution was followed by a push by pro-Russian protesters for Crimea to secede from Ukraine and seek assistance from Russia. Four days thousands of pro-Russian and pro-Ukraine protesters clashed in front of the parliament building in Simferopol. On 28 February 2014, Russian forces occupied airports and other strategic locations in Crimea though the Russian foreign ministry stated that "movement of the Black Sea Fleet armored vehicles in Crimea happens in full accordance with basic Russian-Ukrainian agreements on the Black Sea Fleet". Gunmen, either armed militants or Russian special forces, occupied the Crimean parliament and, under armed guard with doors locked, members of parliament elected Sergey Aksyonov as the new Crimean Prime Minister. Aksyonov said that he asserted sole control over Crimea's security forces and appealed to Russia "for assistance in guaranteeing peace and calmness" on the peninsula
In the context of spaceflight, a satellite is an artificial object, intentionally placed into orbit. Such objects are sometimes called artificial satellites to distinguish them from natural satellites such as Earth's Moon. On 4 October 1957 the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since about 8,100 satellites from more than 40 countries have been launched. According to a 2018 estimate, some 4,900 remain in orbit, of those about 1,900. 500 operational satellites are in low-Earth orbit, 50 are in medium-Earth orbit, the rest are in geostationary orbit. A few large satellites have been assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites to the Moon, Venus, Jupiter, Saturn, a few asteroids, a comet and the Sun. Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of planetary surfaces, take pictures of planets they are launched into.
Common types include military and civilian Earth observation satellites, communications satellites, navigation satellites, weather satellites, space telescopes. Space stations and human spacecraft in orbit are satellites. Satellite orbits vary depending on the purpose of the satellite, are classified in a number of ways. Well-known classes include low Earth orbit, polar orbit, geostationary orbit. A launch vehicle is a rocket, it lifts off from a launch pad on land. Some are launched at sea aboard a plane. Satellites are semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, attitude control and orbit control. "Newton's cannonball", presented as a "thought experiment" in A Treatise of the System of the World, by Isaac Newton was the first published mathematical study of the possibility of an artificial satellite. The first fictional depiction of a satellite being launched into orbit was a short story by Edward Everett Hale, The Brick Moon.
The idea surfaced again in Jules Verne's The Begum's Fortune. In 1903, Konstantin Tsiolkovsky published Exploring Space Using Jet Propulsion Devices, the first academic treatise on the use of rocketry to launch spacecraft, he calculated the orbital speed required for a minimal orbit, that a multi-stage rocket fuelled by liquid propellants could achieve this. In 1928, Herman Potočnik published The Problem of Space Travel -- The Rocket Motor, he described the use of orbiting spacecraft for observation of the ground and described how the special conditions of space could be useful for scientific experiments. In a 1945 Wireless World article, the English science fiction writer Arthur C. Clarke described in detail the possible use of communications satellites for mass communications, he suggested. The US military studied the idea of what was referred to as the "earth satellite vehicle" when Secretary of Defense James Forrestal made a public announcement on 29 December 1948, that his office was coordinating that project between the various services.
The first artificial satellite was Sputnik 1, launched by the Soviet Union on 4 October 1957, initiating the Soviet Sputnik program, with Sergei Korolev as chief designer. This in turn triggered the Space Race between the United States. Sputnik 1 helped to identify the density of high atmospheric layers through measurement of its orbital change and provided data on radio-signal distribution in the ionosphere; the unanticipated announcement of Sputnik 1's success precipitated the Sputnik crisis in the United States and ignited the so-called Space Race within the Cold War. Sputnik 2 was launched on 3 November 1957 and carried the first living passenger into orbit, a dog named Laika. In May, 1946, Project RAND had released the Preliminary Design of an Experimental World-Circling Spaceship, which stated, "A satellite vehicle with appropriate instrumentation can be expected to be one of the most potent scientific tools of the Twentieth Century." The United States had been considering launching orbital satellites since 1945 under the Bureau of Aeronautics of the United States Navy.
The United States Air Force's Project RAND released the report, but considered the satellite to be a tool for science and propaganda, rather than a potential military weapon. In 1954, the Secretary of Defense stated, "I know of no American satellite program." In February 1954 Project RAND released "Scientific Uses for a Satellite Vehicle," written by R. R. Carhart; this expanded on potential scientific uses for satellite vehicles and was followed in June 1955 with "The Scientific Use of an Artificial Satellite," by H. K. Kallmann and W. W. Kellogg. In the context of activities planned for the International Geophysical Year, the White House announced on 29 July 1955 that the U. S. intended to launch satellites by the spring of 1958. This became known as Project Vanguard. On 31 July, the Soviets announced that they intended to launch a satellite by the fall of 1957. Following pressure by the American Rocket Society, the National Science Foundation, the International Geophysical Year, military interest picked up and in early 1955 the Army and Navy were worki
Astronomy is a natural science that studies celestial objects and phenomena. It applies mathematics and chemistry in an effort to explain the origin of those objects and phenomena and their evolution. Objects of interest include planets, stars, nebulae and comets. More all phenomena that originate outside Earth's atmosphere are within the purview of astronomy. A related but distinct subject is physical cosmology, the study of the Universe as a whole. Astronomy is one of the oldest of the natural sciences; the early civilizations in recorded history, such as the Babylonians, Indians, Nubians, Chinese and many ancient indigenous peoples of the Americas, performed methodical observations of the night sky. Astronomy has included disciplines as diverse as astrometry, celestial navigation, observational astronomy, the making of calendars, but professional astronomy is now considered to be synonymous with astrophysics. Professional astronomy is split into theoretical branches. Observational astronomy is focused on acquiring data from observations of astronomical objects, analyzed using basic principles of physics.
Theoretical astronomy is oriented toward the development of computer or analytical models to describe astronomical objects and phenomena. The two fields complement each other, with theoretical astronomy seeking to explain observational results and observations being used to confirm theoretical results. Astronomy is one of the few sciences in which amateurs still play an active role in the discovery and observation of transient events. Amateur astronomers have made and contributed to many important astronomical discoveries, such as finding new comets. Astronomy means "law of the stars". Astronomy should not be confused with astrology, the belief system which claims that human affairs are correlated with the positions of celestial objects. Although the two fields share a common origin, they are now distinct. Both of the terms "astronomy" and "astrophysics" may be used to refer to the same subject. Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties," while "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, dynamic processes of celestial objects and phenomena."
In some cases, as in the introduction of the introductory textbook The Physical Universe by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject. However, since most modern astronomical research deals with subjects related to physics, modern astronomy could be called astrophysics; some fields, such as astrometry, are purely astronomy rather than astrophysics. Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics" depending on whether the department is affiliated with a physics department, many professional astronomers have physics rather than astronomy degrees; some titles of the leading scientific journals in this field include The Astronomical Journal, The Astrophysical Journal, Astronomy and Astrophysics. In early historic times, astronomy only consisted of the observation and predictions of the motions of objects visible to the naked eye.
In some locations, early cultures assembled massive artifacts that had some astronomical purpose. In addition to their ceremonial uses, these observatories could be employed to determine the seasons, an important factor in knowing when to plant crops and in understanding the length of the year. Before tools such as the telescope were invented, early study of the stars was conducted using the naked eye; as civilizations developed, most notably in Mesopotamia, Persia, China and Central America, astronomical observatories were assembled and ideas on the nature of the Universe began to develop. Most early astronomy consisted of mapping the positions of the stars and planets, a science now referred to as astrometry. From these observations, early ideas about the motions of the planets were formed, the nature of the Sun and the Earth in the Universe were explored philosophically; the Earth was believed to be the center of the Universe with the Sun, the Moon and the stars rotating around it. This is known as the geocentric model of the Ptolemaic system, named after Ptolemy.
A important early development was the beginning of mathematical and scientific astronomy, which began among the Babylonians, who laid the foundations for the astronomical traditions that developed in many other civilizations. The Babylonians discovered. Following the Babylonians, significant advances in astronomy were made in ancient Greece and the Hellenistic world. Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. In the 3rd century BC, Aristarchus of Samos estimated the size and distance of the Moon and Sun, he proposed a model of the Solar System where the Earth and planets rotated around the Sun, now called the heliocentric model. In the 2nd century BC, Hipparchus discovered precession, calculated the size and distance of the Moon and inven
Russia the Russian Federation, is a transcontinental country in Eastern Europe and North Asia. At 17,125,200 square kilometres, Russia is by far or by a considerable margin the largest country in the world by area, covering more than one-eighth of the Earth's inhabited land area, the ninth most populous, with about 146.77 million people as of 2019, including Crimea. About 77 % of the population live in the European part of the country. Russia's capital, Moscow, is one of the largest cities in the world and the second largest city in Europe. Extending across the entirety of Northern Asia and much of Eastern Europe, Russia spans eleven time zones and incorporates a wide range of environments and landforms. From northwest to southeast, Russia shares land borders with Norway, Estonia, Latvia and Poland, Ukraine, Azerbaijan, China and North Korea, it shares maritime borders with Japan by the Sea of Okhotsk and the U. S. state of Alaska across the Bering Strait. However, Russia recognises two more countries that border it, Abkhazia and South Ossetia, both of which are internationally recognized as parts of Georgia.
The East Slavs emerged as a recognizable group in Europe between the 3rd and 8th centuries AD. Founded and ruled by a Varangian warrior elite and their descendants, the medieval state of Rus arose in the 9th century. In 988 it adopted Orthodox Christianity from the Byzantine Empire, beginning the synthesis of Byzantine and Slavic cultures that defined Russian culture for the next millennium. Rus' disintegrated into a number of smaller states; the Grand Duchy of Moscow reunified the surrounding Russian principalities and achieved independence from the Golden Horde. By the 18th century, the nation had expanded through conquest and exploration to become the Russian Empire, the third largest empire in history, stretching from Poland on the west to Alaska on the east. Following the Russian Revolution, the Russian Soviet Federative Socialist Republic became the largest and leading constituent of the Union of Soviet Socialist Republics, the world's first constitutionally socialist state; the Soviet Union played a decisive role in the Allied victory in World War II, emerged as a recognized superpower and rival to the United States during the Cold War.
The Soviet era saw some of the most significant technological achievements of the 20th century, including the world's first human-made satellite and the launching of the first humans in space. By the end of 1990, the Soviet Union had the world's second largest economy, largest standing military in the world and the largest stockpile of weapons of mass destruction. Following the dissolution of the Soviet Union in 1991, twelve independent republics emerged from the USSR: Russia, Belarus, Uzbekistan, Azerbaijan, Kyrgyzstan, Tajikistan and the Baltic states regained independence: Estonia, Lithuania, it is governed as a federal semi-presidential republic. Russia's economy ranks as the twelfth largest by nominal GDP and sixth largest by purchasing power parity in 2018. Russia's extensive mineral and energy resources are the largest such reserves in the world, making it one of the leading producers of oil and natural gas globally; the country is one of the five recognized nuclear weapons states and possesses the largest stockpile of weapons of mass destruction.
Russia is a great power as well as a regional power and has been characterised as a potential superpower. It is a permanent member of the United Nations Security Council and an active global partner of ASEAN, as well as a member of the Shanghai Cooperation Organisation, the G20, the Council of Europe, the Asia-Pacific Economic Cooperation, the Organization for Security and Co-operation in Europe, the World Trade Organization, as well as being the leading member of the Commonwealth of Independent States, the Collective Security Treaty Organization and one of the five members of the Eurasian Economic Union, along with Armenia, Belarus and Kyrgyzstan; the name Russia is derived from Rus', a medieval state populated by the East Slavs. However, this proper name became more prominent in the history, the country was called by its inhabitants "Русская Земля", which can be translated as "Russian Land" or "Land of Rus'". In order to distinguish this state from other states derived from it, it is denoted as Kievan Rus' by modern historiography.
The name Rus itself comes from the early medieval Rus' people, Swedish merchants and warriors who relocated from across the Baltic Sea and founded a state centered on Novgorod that became Kievan Rus. An old Latin version of the name Rus' was Ruthenia applied to the western and southern regions of Rus' that were adjacent to Catholic Europe; the current name of the country, Россия, comes from the Byzantine Greek designation of the Rus', Ρωσσία Rossía—spelled Ρωσία in Modern Greek. The standard way to refer to citizens of Russia is rossiyane in Russian. There are two Russian words which are commonly