text:
Gravity

In physics, gravity is a fundamental interaction which causes mutual attraction between all things that have mass. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a result, it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.

On Earth, gravity gives weight to physical objects, and the Moon's gravity is responsible for sublunar tides in the oceans. The corresponding antipodal tide is caused by the inertia of the Earth and Moon orbiting one another. Gravity also has many important biological functions, helping to guide the growth of plants through the process of gravitropism and influencing the circulation of fluids in multicellular organisms.

The gravitational attraction between the original gaseous matter in the universe caused it to coalesce and form stars which eventually condensed into galaxies, so gravity is responsible for many of the large-scale structures in the universe. Gravity has an infinite range, although its effects become weaker as objects get farther away.

Gravity is most accurately described by the general theory of relativity, proposed by Albert Einstein in 1915, which describes gravity not as a force, but as the curvature of spacetime, caused by the uneven distribution of mass, and causing masses to move along geodesic lines. The most extreme example of this curvature of spacetime is a black hole, from which nothing—not even light—can escape once past the black hole's event horizon. However, for most applications, gravity is well approximated by Newton's law of universal gravitation, which describes gravity as a force causing any two bodies to be attracted toward each other, with magnitude proportional to the product of their masses and inversely proportional to the square of the distance between them.

Current models of particle physics imply that the earliest instance of gravity in the universe, possibly in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch (up to 10−43 seconds after the birth of the universe), possibly from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a currently unknown manner. Scientists are currently working to develop a theory of gravity consistent with quantum mechanics, a quantum gravity theory, which would allow gravity to be united in a common mathematical framework (a theory of everything) with the other three fundamental interactions of physics.

Definitions
, also known as gravitational attraction, is the mutual attraction between all masses in the universe. Gravity is the gravitational attraction at the surface of a planet or other celestial body; gravity may also include, in addition to gravitation, the centrifugal force resulting from the planet's rotation.

Ancient world
The nature and mechanism of gravity were explored by a wide range of ancient scholars. In Greece, Aristotle believed that objects fell towards the Earth because the Earth was the center of the Universe and attracted all of the mass in the Universe towards it. He also thought that the speed of a falling object should increase with its weight, a conclusion that was later shown to be false. While Aristotle's view was widely accepted throughout Ancient Greece, there were other thinkers such as Plutarch who correctly predicted that the attraction of gravity was not unique to the Earth.

Although he did not understand gravity as a force, the ancient Greek philosopher Archimedes discovered the center of gravity of a triangle. He postulated that if two equal weights did not have the same center of gravity, the center of gravity of the two weights together would be in the middle of the line that joins their centers of gravity. Two centuries later, the Roman engineer and architect Vitruvius contended in his De architectura that gravity is not dependent on a substance's weight but rather on its "nature". In the 6th century CE, the Byzantine Alexandrian scholar John Philoponus proposed the theory of impetus, which modifies Aristotle's theory that "continuation of motion depends on continued action of a force" by incorporating a causative force that diminishes over time.

In the seventh century CE, the Indian mathematician and astronomer Brahmagupta proposed the idea that gravity is an attractive force that draws objects to the Earth and used the term gurutvākarṣaṇ to describe it.

In the ancient Middle East, gravity was a topic of fierce debate. The Persian intellectual Al-Biruni believed that the force of gravity was not unique to the Earth, and he correctly assumed that other heavenly bodies should exert a gravitational attraction as well. In contrast, Al-Khazini held the same position as Aristotle that all matter in the Universe is attracted to the center of the Earth.

Scientific revolution
In the mid-16th century, various European scientists experimentally disproved the Aristotelian notion that heavier objects fall at a faster rate. In particular, the Spanish Dominican priest Domingo de Soto wrote in 1551 that bodies in free fall uniformly accelerate. De Soto may have been influenced by earlier experiments conducted by other Dominican priests in Italy, including those by Benedetto Varchi, Francesco Beato, Luca Ghini, and Giovan Bellaso which contradicted Aristotle's teachings on the fall of bodies.

The mid-16th century Italian physicist Giambattista Benedetti published papers claiming that, due to specific gravity, objects made of the same material but with different masses would fall at the same speed. With the 1586 Delft tower experiment, the Flemish physicist Simon Stevin observed that two cannonballs of differing sizes and weights fell at the same rate when dropped from a tower. In the late 16th century, Galileo Galilei's careful measurements of balls rolling down inclines allowed him to firmly establish that gravitational acceleration is the same for all objects. Galileo postulated that air resistance is the reason that objects with a low density and high surface area fall more slowly in an atmosphere.

In 1604, Galileo correctly hypothesized that the distance of a falling object is proportional to the square of the time elapsed. This was later confirmed by Italian scientists Jesuits Grimaldi and Riccioli between 1640 and 1650. They also calculated the magnitude of the Earth's gravity by measuring the oscillations of a pendulum.

Newton's theory of gravitation
In 1657, Robert Hooke published his Micrographia, in which he hypothesised that the Moon must have its own gravity. In 1666, he added two further principles: that all bodies move in straight lines until deflected by some force and that the attractive force is stronger for closer bodies. In a communication to the Royal Society in 1666, Hooke wrote "I will explain a system of the world very different from any yet received. It is founded on the following positions. 1. That all the heavenly bodies have not only a gravitation of their parts to their own proper centre, but that they also mutually attract each other within their spheres of action. 2. That all bodies having a simple motion, will continue to move in a straight line, unless continually deflected from it by some extraneous force, causing them to describe a circle, an ellipse, or some other curve. 3. That this attraction is so much the greater as the bodies are nearer. As to the proportion in which those forces diminish by an increase of distance, I own I have not discovered it...." Hooke's 1674 Gresham lecture, An Attempt to prove the Annual Motion of the Earth, explained that gravitation applied to "all celestial bodies"

In 1684, Newton sent a manuscript to Edmond Halley titled De motu corporum in gyrum ('On the motion of bodies in an orbit'), which provided a physical justification for Kepler's laws of planetary motion. Halley was impressed by the manuscript and urged Newton to expand on it, and a few years later Newton published a groundbreaking book called Philosophiæ Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy). In this book, Newton described gravitation as a universal force, and claimed that "the forces which keep the planets in their orbs must [be] reciprocally as the squares of their distances from the centers about which they revolve." This statement was later condensed into the following inverse-square law:

$$F = G \frac{m_1 m_2}{r^2}, $$where $F$ is the force, $m_{1}$ and $m_{2}$ are the masses of the objects interacting, $r$ is the distance between the centers of the masses and $G$ is the gravitational constant

Newton's Principia was well received by the scientific community, and his law of gravitation quickly spread across the European world. More than a century later, in 1821, his theory of gravitation rose to even greater prominence when it was used to predict the existence of Neptune. In that year, the French astronomer Alexis Bouvard used this theory to create a table modeling the orbit of Uranus, which was shown to differ significantly from the planet's actual trajectory. In order to explain this discrepancy, many astronomers speculated that there might be a large object beyond the orbit of Uranus which was disrupting its orbit. In 1846, the astronomers John Couch Adams and Urbain Le Verrier independently used Newton's law to predict Neptune's location in the night sky, and the planet was discovered there within a day.

General relativity
Eventually, astronomers noticed an eccentricity in the orbit of the planet Mercury which could not be explained by Newton's theory: the perihelion of the orbit was increasing by about 42.98 arcseconds per century. The most obvious explanation for this discrepancy was an as-yet-undiscovered celestial body, such as a planet orbiting the Sun even closer than Mercury, but all efforts to find such a body turned out to be fruitless. In 1915, Albert Einstein developed a theory of general relativity which was able to accurately model Mercury's orbit.

In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of a force. Einstein began to toy with this idea in the form of the equivalence principle, a discovery which he later described as "the happiest thought of my life." In this theory, free fall is considered to be equivalent to inertial motion, meaning that free-falling inertial objects are accelerated relative to non-inertial observers on the ground. In contrast to Newtonian physics, Einstein believed that it was possible for this acceleration to occur without any force being applied to the object.

Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. These straight paths are called geodesics. As in Newton's first law of motion, Einstein believed that a force applied to an object would cause it to deviate from a geodesic. For instance, people standing on the surface of the Earth are prevented from following a geodesic path because the mechanical resistance of the Earth exerts an upward force on them. This explains why moving along the geodesics in spacetime is considered inertial.

Einstein's description of gravity was quickly accepted by the majority of physicists, as it was able to explain a wide variety of previously baffling experimental results. In the coming years, a wide range of experiments provided additional support for the idea of general relativity. Today, Einstein's theory of relativity is used for all gravitational calculations where absolute precision is desired, although Newton's inverse-square law continues to be a useful and fairly accurate approximation.

Modern research
In modern physics, general relativity remains the framework for the understanding of gravity. Physicists continue to work to find solutions to the Einstein field equations that form the basis of general relativity, while some scientists have speculated that general relativity may not be applicable at all in certain scenarios.

Einstein field equations
The Einstein field equations are a system of 10 partial differential equations which describe how matter affects the curvature of spacetime. The system is often expressed in the form $$G_{\mu \nu} + \Lambda g_{\mu \nu} = \kappa T_{\mu \nu},$$ where $Gμν$ is the Einstein tensor, $gμν$ is the metric tensor, $Tμν$ is the stress–energy tensor, $Λ$ is the cosmological constant, $$G$$ is the Newtonian constant of gravitation and $$c$$ is the speed of light. The constant $$\kappa = \frac{8\pi G}{c^4}$$ is referred to as the Einstein gravitational constant.

A major area of research is the discovery of exact solutions to the Einstein field equations. Solving these equations amounts to calculating a precise value for the metric tensor (which defines the curvature and geometry of spacetime) under certain physical conditions. There is no formal definition for what constitutes such solutions, but most scientists agree that they should be expressable using elementary functions or linear differential equations. Some of the most notable solutions of the equations include:
 * The Schwarzschild solution, which describes spacetime surrounding a spherically symmetric non-rotating uncharged massive object. For compact enough objects, this solution generated a black hole with a central singularity. At points far away from the central mass, the accelerations predicted by the Schwarzschild solution are practically identical to those predicted by Newton's theory of gravity.
 * The Reissner–Nordström solution, which analyzes a non-rotating spherically symmetric object with charge and was independently discovered by several different researchers between 1916 and 1921. In some cases, this solution can predict the existence of black holes with double event horizons.
 * The Kerr solution, which generalizes the Schwarzchild solution to rotating massive objects. Because of the difficulty of factoring in the effects of rotation into the Einstein field equations, this solution was not discovered until 1963.
 * The Kerr–Newman solution for charged, rotating massive objects. This solution was derived in 1964, using the same technique of complex coordinate transformation that was used for the Kerr solution.
 * The cosmological Friedmann–Lemaître–Robertson–Walker solution, discovered in 1922 by Alexander Friedmann and then confirmed in 1927 by Georges Lemaître. This solution was revolutionary for predicting the expansion of the Universe, which was confirmed seven years later after a series of measurements by Edwin Hubble. It even showed that general relativity was incompatible with a static universe, and Einstein later conceded that he had been wrong to design his field equations to account for a Universe that was not expanding.

Today, there remain many important situations in which the Einstein field equations have not been solved. Chief among these is the two-body problem, which concerns the geometry of spacetime around two mutually interacting massive objects, such as the Sun and the Earth, or the two stars in a binary star system. The situation gets even more complicated when considering the interactions of three or more massive bodies (the "n-body problem"), and some scientists suspect that the Einstein field equations will never be solved in this context. However, it is still possible to construct an approximate solution to the field equations in the n-body problem by using the technique of post-Newtonian expansion. In general, the extreme nonlinearity of the Einstein field equations makes it difficult to solve them in all but the most specific cases.

Gravity and quantum mechanics
Despite its success in predicting the effects of gravity at large scales, general relativity is ultimately incompatible with quantum mechanics. This is because general relativity describes gravity as a smooth, continuous distortion of spacetime, while quantum mechanics holds that all forces arise from the exchange of discrete particles known as quanta. This contradiction is especially vexing to physicists because the other three fundamental forces (strong force, weak force and electromagnetism) were reconciled with a quantum framework decades ago. As a result, modern researchers have begun to search for a theory that could unite both gravity and quantum mechanics under a more general framework.

One path is to describe gravity in the framework of quantum field theory, which has been successful to accurately describe the other fundamental interactions. The electromagnetic force arises from an exchange of virtual photons, where the QFT description of gravity is that there is an exchange of virtual gravitons. This description reproduces general relativity in the classical limit. However, this approach fails at short distances of the order of the Planck length, where a more complete theory of quantum gravity (or a new approach to quantum mechanics) is required.

Tests of general relativity
Testing the predictions of general relativity has historically been difficult, because they are almost identical to the predictions of Newtonian gravity for small energies and masses. Still, since its development, an ongoing series of experimental results have provided support for the theory:
 * In 1919, the British astrophysicist Arthur Eddington was able to confirm the predicted gravitational lensing of light during that year's solar eclipse. Eddington measured starlight deflections twice those predicted by Newtonian corpuscular theory, in accordance with the predictions of general relativity. Although Eddington's analysis was later disputed, this experiment made Einstein famous almost overnight and caused general relativity to become widely accepted in the scientific community.
 * In 1959, American physicists Robert Pound and Glen Rebka performed an experiment in which they used gamma rays to confirm the prediction of gravitational time dilation. By sending the rays down a 74-foot tower and measuring their frequency at the bottom, the scientists confirmed that light is redshifted as it moves towards a source of gravity. The observed redshift also supported the idea that time runs more slowly in the presence of a gravitational field.
 * The time delay of light passing close to a massive object was first identified by Irwin I. Shapiro in 1964 in interplanetary spacecraft signals.
 * In 1971, scientists discovered the first-ever black hole in the galaxy Cygnus. The black hole was detected because it was emitting bursts of x-rays as it consumed a smaller star, and it came to be known as Cygnus X-1. This discovery confirmed yet another prediction of general relativity, because Einstein's equations implied that light could not escape from a sufficiently large and compact object.
 * General relativity states that gravity acts on light and matter equally, meaning that a sufficiently massive object could warp light around it and create a gravitational lens. This phenomenon was first confirmed by observation in 1979 using the 2.1 meter telescope at Kitt Peak National Observatory in Arizona, which saw two mirror images of the same quasar whose light had been bent around the galaxy YGKOW G1.
 * Frame dragging, the idea that a rotating massive object should twist spacetime around it, was confirmed by Gravity Probe B results in 2011.
 * In 2015, the LIGO observatory detected faint gravitational waves, the existence of which had been predicted by general relativity. Scientists believe that the waves emanated from a black hole merger that occurred 1.5 billion light-years away.

Earth's gravity

Every planetary body (including the Earth) is surrounded by its own gravitational field, which can be conceptualized with Newtonian physics as exerting an attractive force on all objects. Assuming a spherically symmetrical planet, the strength of this field at any given point above the surface is proportional to the planetary body's mass and inversely proportional to the square of the distance from the center of the body. The strength of the gravitational field is numerically equal to the acceleration of objects under its influence. The rate of acceleration of falling objects near the Earth's surface varies very slightly depending on latitude, surface features such as mountains and ridges, and perhaps unusually high or low sub-surface densities. For purposes of weights and measures, a standard gravity value is defined by the International Bureau of Weights and Measures, under the International System of Units (SI).

The force of gravity on Earth is the resultant (vector sum) of two forces: (a) The gravitational attraction in accordance with Newton's universal law of gravitation, and (b) the centrifugal force, which results from the choice of an earthbound, rotating frame of reference. The force of gravity is weakest at the equator because of the centrifugal force caused by the Earth's rotation and because points on the equator are furthest from the center of the Earth. The force of gravity varies with latitude and increases from about 9.780 m/s2 at the Equator to about 9.832 m/s2 at the poles.

Origin
The earliest gravity (possibly in the form of quantum gravity, supergravity or a gravitational singularity), along with ordinary space and time, developed during the Planck epoch (up to 10−43 seconds after the birth of the Universe), possibly from a primeval state (such as a false vacuum, quantum vacuum or virtual particle), in a currently unknown manner.

Gravitational radiation

General relativity predicts that energy can be transported out of a system through gravitational radiation. The first indirect evidence for gravitational radiation was through measurements of the Hulse–Taylor binary in 1973. This system consists of a pulsar and neutron star in orbit around one another. Its orbital period has decreased since its initial discovery due to a loss of energy, which is consistent for the amount of energy loss due to gravitational radiation. This research was awarded the Nobel Prize in Physics in 1993.

The first direct evidence for gravitational radiation was measured on 14 September 2015 by the LIGO detectors. The gravitational waves emitted during the collision of two black holes 1.3 billion light years from Earth were measured. This observation confirms the theoretical predictions of Einstein and others that such waves exist. It also opens the way for practical observation and understanding of the nature of gravity and events in the Universe including the Big Bang. Neutron star and black hole formation also create detectable amounts of gravitational radiation. This research was awarded the Nobel Prize in Physics in 2017.

Speed of gravity
In December 2012, a research team in China announced that it had produced measurements of the phase lag of Earth tides during full and new moons which seem to prove that the speed of gravity is equal to the speed of light. This means that if the Sun suddenly disappeared, the Earth would keep orbiting the vacant point normally for 8 minutes, which is the time light takes to travel that distance. The team's findings were released in Science Bulletin in February 2013.

In October 2017, the LIGO and Virgo detectors received gravitational wave signals within 2 seconds of gamma ray satellites and optical telescopes seeing signals from the same direction. This confirmed that the speed of gravitational waves was the same as the speed of light.

Anomalies and discrepancies
There are some observations that are not adequately accounted for, which may point to the need for better theories of gravity or perhaps be explained in other ways.
 * Extra-fast stars: Stars in galaxies follow a distribution of velocities where stars on the outskirts are moving faster than they should according to the observed distributions of normal matter. Galaxies within galaxy clusters show a similar pattern. Dark matter, which would interact through gravitation but not electromagnetically, would account for the discrepancy. Various modifications to Newtonian dynamics have also been proposed.
 * Flyby anomaly: Various spacecraft have experienced greater acceleration than expected during gravity assist maneuvers.
 * Accelerated expansion: The expansion of the universe seems to be speeding up. Dark energy has been proposed to explain this.
 * Anomalous increase of the astronomical unit: Recent measurements indicate that planetary orbits are widening faster than if this were solely through the Sun losing mass by radiating energy.
 * Extra energetic photons: Photons travelling through galaxy clusters should gain energy and then lose it again on the way out. The accelerating expansion of the Universe should stop the photons returning all the energy, but even taking this into account photons from the cosmic microwave background radiation gain twice as much energy as expected. This may indicate that gravity falls off faster than inverse-squared at certain distance scales.
 * Extra massive hydrogen clouds: The spectral lines of the Lyman-alpha forest suggest that hydrogen clouds are more clumped together at certain scales than expected and, like dark flow, may indicate that gravity falls off slower than inverse-squared at certain distance scales.

Historical alternative theories

 * Aristotelian theory of gravity
 * Le Sage's theory of gravitation (1784) also called LeSage gravity but originally proposed by Fatio and further elaborated by Georges-Louis Le Sage, based on a fluid-based explanation where a light gas fills the entire Universe.
 * Ritz's theory of gravitation, Ann. Chem. Phys. 13, 145, (1908) pp. 267–271, Weber–Gauss electrodynamics applied to gravitation. Classical advancement of perihelia.
 * Nordström's theory of gravitation (1912, 1913), an early competitor of general relativity.
 * Kaluza–Klein theory (1921)
 * Whitehead's theory of gravitation (1922), another early competitor of general relativity.

Modern alternative theories

 * Brans–Dicke theory of gravity (1961)
 * Induced gravity (1967), a proposal by Andrei Sakharov according to which general relativity might arise from quantum field theories of matter
 * String theory (late 1960s)
 * ƒ(R) gravity (1970)
 * Horndeski theory (1974)
 * Supergravity (1976)
 * In the modified Newtonian dynamics (MOND) (1981), Mordehai Milgrom proposes a modification of Newton's second law of motion for small accelerations
 * The self-creation cosmology theory of gravity (1982) by G.A. Barber in which the Brans–Dicke theory is modified to allow mass creation
 * Loop quantum gravity (1988) by Carlo Rovelli, Lee Smolin, and Abhay Ashtekar
 * Nonsymmetric gravitational theory (NGT) (1994) by John Moffat
 * Tensor–vector–scalar gravity (TeVeS) (2004), a relativistic modification of MOND by Jacob Bekenstein
 * Chameleon theory (2004) by Justin Khoury and Amanda Weltman.
 * Pressuron theory (2013) by Olivier Minazzoli and Aurélien Hees.
 * Conformal gravity
 * Gravity as an entropic force, gravity arising as an emergent phenomenon from the thermodynamic concept of entropy.
 * In the superfluid vacuum theory the gravity and curved spacetime arise as a collective excitation mode of non-relativistic background superfluid.
 * Massive gravity, a theory where gravitons and gravitational waves have a non-zero mass

title: Gravity


text:
Poltava

 Poltava  (, ; Полтава, ) is a city located on the Vorskla River in Central Ukraine. It serves as the administrative center of Poltava Oblast as well as Poltava Raion within the oblast. It also hosts the administration of Poltava urban hromada, one of the hromadas of Ukraine. Poltava has a population of

History
It is still unknown when Poltava was founded, although the town was not attested before 1174. However, municipal authorities chose to celebrate the city's 1100th anniversary in 1999. The settlement is indeed an old one, as archeologists unearthed an ancient Paleolithic dwelling, as well as Scythian remains, within the city limits.

Middle Ages
The present name of the city is traditionally connected to the settlement Ltava, which is mentioned in the Hypatian Chronicle in 1174. According to the chronicle, on Saint Peter's Day (12 July) of 1182, Igor Sviatoslavich, chasing hordes of the Cuman khans Konchak and Kobiak, crossed the Vorskla River near Ltava and moved towards Pereiaslav), where Igor's army was victorious over the Cumans. During the Mongol invasion of Rus' in 1238–39, many cities of the middle Dnipro region were destroyed, possibly including Ltava.

In the mid-14th century the region was part of the Duchy of Kyiv, which was a vassal of the Algirdas' Grand Duchy of Lithuania. According to the Russian historian Aleksandr Shennikov, the region around modern Poltava was a Cuman Duchy belonging to Mansur, who was a son of Mamai. Shennikov also claims that the Mansur Duchy joined the Grand Duchy of Lithuania as an associated state rather than a vassal state, and that the city of Poltava already existed at that time. In 1399, Mansur's army assisted the Grand Ducal Lithuanian Army in the battle of the Vorskla River. According to legend, after the battle, the Cossack Mamay helped Vytautas to escape death.

The city is mentioned for the first time under the name of Poltava no later than 1430. Supposedly, in 1430 the Lithuanian duke Vytautas gave the city, along with Glinsk (today a village near the city of Romny) and Glinitsa, to Murza Olexa (Loxada Mansurxanovich), who moved to the Grand Duchy of Lithuania from the Golden Horde. In 1430 Murza Olexa was baptized as Alexander Glinsky, who was a progenitor of the Glinsky family. According to Shenninkov, Alexander Glinsky must have been baptized in 1390 by Cyprian, Metropolitan of Kyiv, who had just regained his title of Metropolitan of Kyiv and all Russia (rather than the Metropolitan of Russia Minor and Lithuania). On 6 March 1390 Cyprian permanently moved to Muscovy.

In 1482, Poltava was razed by the Crimean Khan Mengli I Giray.

Early modern period
In 1537 Ografena Vasylivna Glinska (Baibuza) passed Poltava to her son-in-law Mykhailo Ivanovych Hrybunov-Baibuza.

After the Union of Lublin in 1569, the territory around Poltava became part of the Crown of Poland. In 1630 Poltava was passed to a Polish magnate, Bartholomew Obalkowski. In 1641 it changed ownership again, to Alexander Koniecpolski. In 1646 Poltava became part of Wiśniowiecki Ordynatsia (a large Wiśniowiecki estate in Left-bank Ukraine centered in Lubny), governed by the Ruthenian-Polish magnate Jeremi Wiśniowiecki (1612–51).

In 1648, the city became the base of a distinguished regiment of Ukrainian Cossacks, and served as a Cossack stronghold during the Khmelnytsky Uprising. In 1650, to commemorate a victory of the Cossack Host over the Polish army at the Poltavka River, the Metropolitan of Kyiv, Sylvester Kossov, ordered the establishment of the Holy Cross Exaltation Monastery in Poltava. The project was financed by a number of prominent local residents, including Martyn Pushkar, Ivan Iskra, Ivan Kramar and many others.

During the 1654 Pereyaslav Council, the Poltava city delegates pledged their allegiance to the Czar of Muscovy, after which stolnik Andrei Spasitelev arrived in Poltava and recorded 1,335 residents who had pledged their allegiance. In 1658 Poltava became a center of anti-government revolt led by Martyn Pushkar, who contested the legitimacy of Ivan Vyhovsky's election to the post of Hetman of Zaporizhian Host. The uprising was extinguished with the help of Crimean Tatars.

On the issue boyar Vasily Borisovich Sheremetev wrote to Alexei Mikhailovich on 8 June 1658: "... the Cherkas [Cossack] city of Poltava is ravaged and burned to the ground and only if the Great Sovereign orders to rebuild on the Tatar Sokma (pathway) of Bakeyev Route and protect many his sovereign cities from Tatar visits. And if the Great Sovereign allows to place a voivode in the city and rebuilt the city until the fall that in Poltava Cherkasy [Cossacks] and residents built their houses and stock-piled their food". With the signing of the 1667 truce of Andrusovo, the city was finally subjected to the Tsardom of Muscovy, while remaining part of the Cossack Hetmanate.

The city suffered from the Great Turkish War when in 1695 Petro Ivanenko led an anti-Muscovite uprising with the help of Crimean Tatars, who ravaged the local monastery. The same year the Poltava Regiment actively participated in the Azov campaigns which resulted in the taking of the Turkish fortress of Kyzy-Kermen (today the city of Beryslav, Kherson Oblast). On 8 July (New Style) or 27 June (Old Style) 1709 the Battle of Poltava took place near the city during the Great Northern War. The battle ended in a decisive victory of Peter I of Russia over the Swedish forces and had great historical importance for the Russians. In 1710 there was a plague in the city and its surrounding area. In the mid-18th century the Kolomak Woods near Poltava became a base of haidamaks (Cossack paramilitary bands).

By 1770, Poltava had several brick factories, a regimental doctor, and a pharmacy; that same year the city conducted four fairs. In 1775 it became a city of Novorossiysk Governorate, guarded by the 8th Company of the Dnieper Pike Regiment headquartered in Kobeliaky. In 1775 Poltava's Holy Cross Exaltation Monastery became the seat of bishops of the newly created Eparchy (Diocese) of Slaviansk and Kherson. This large new diocese included the lands of the Novorossiya Governorate and the Azov Governorate north of the Black Sea.

Since much of that area had only recently been seized from the Ottoman Empire by Russia, and a large number of Orthodox Greek settlers had been invited to settle in the region, the imperial government selected a renowned Greek scholar, Eugenios Voulgaris, to preside over the new diocese. After his retirement in 1779, he was replaced by another Greek theologian, Nikephoros Theotokis. In 1779 the city established the Poltava county school, which became its first secular educational institution. In 1787 Catherine the Great stopped in Poltava on the way from Crimea, escorted by Grigori Potemkin, Alexander Suvorov and Mikhail Kutuzov. In Poltava, on 7 June 1787, before another Russo-Turkish War, Potemkin received his title "Prince of Taurida", while Suvorov received a snuffbox with monogram. In 1802 the city became the seat of the newly established Poltava Governorate. The city's population in 1802 consisted of some 8,000 residents. That same year Poltava opened a government-funded hospital of 20 beds.

19th century
On 2 February 1808, the Poltava Male Gymnasium was established. On 20 June 1808 some 54 families of craftsmen were invited to the city from German principalities and settled in the newly established German Sloboda neighborhood with about 50 clay-made houses. In 1810 there were 8,328 people living in Poltava; that same year, the city's first theater was built. In August 1812, on orders of Little Russia Governor General Lobanov-Rostovsky, the famed Ukrainian writer and statesman Ivan Kotlyarevsky formed the 5th Poltava Cavalry Cossack Regiment.

By 1860, Poltava had around 30,000 inhabitants, a district school, a gymnasium, an Institute for Noble Maidens, a spiritual academy, a cadet corps, a library and a number of schools. In 1870 a railway station was opened, leading to rapid economic growth in the region. However, by 1914 the Population of Poltava (around 60,000) was mostly working in small enterprises. In the late 19th and early 20th centuries Poltava became an important cultural centre, where many representatives of Ukrainian national revival were active.

20th century
During the events of 1917–1920, Poltava was under the rule of a number of governments, including the Central Rada, Hetmanate, Ukrainian People's Republic, White Movement and Bolsheviks. From 1918 to 1919 there was Occupation of Poltava by the Bolsheviks. After becoming a part of Ukrainian Soviet Socialist Republic, Poltava experienced accelerated industrial growth, and its population increased to 130,000 by 1939.

In World War II, the Nazi Wehrmacht occupied Poltava from 18 September 1941 until 23 September 1943, when it was retaken during the Chernigov-Poltava Strategic Offensive of the Battle of the Dnieper. During the Nazi occupation the Jewish population (9.9% of the total population in 1939) was imprisoned in a ghetto before being murdered during mass executions perpetrated by an Einsatzgruppe and buried in mass graves in the area.

By the summer of 1944, the United States Army Air Forces conducted a number of shuttle bombing raids against Nazi Germany under the name of Operation Frantic. Poltava Air Base, as well as Myrhorod Air Base, were used as eastern locations for landing B-17 Flying Fortress heavy bombers involved in those operations.

The post-war restoration of Poltava continued in the 1950s and 1960s. The city became an important centre of military education in the Soviet Union, where missile and communications officers were prepared, and was also home to a Soviet Air Force division of heavy bombers.

Until 18 July 2020, Poltava was designated as a city of oblast significance and did not belong to Poltava Raion even though it was the center of the raion. As part of the administrative reform of Ukraine, which reduced the number of raions of Poltava Oblast to four, the city was merged into Poltava Raion.

Language
Distribution of the population by native language according to the 2001 census:

According to a survey conducted by the International Republican Institute in April-May 2023, 75 % of the city's population spoke Ukrainian at home, and 12 % spoke Russian.

Climate
Poltava has a warm-summer humid continental climate (Köppen: Dfb), with four distinct seasons, it is one of the coldest cities in Ukraine. The annual precipitation is fairly evenly distributed, with the highest concentration in summer, and which falls as snow in winter.

Government and subdivisions
Poltava is the administrative center of the Poltava Oblast (province) as well as of the Poltava Raion housed within the city. However, Poltava is a city of oblast subordinance, thus being subject directly to the oblast authorities rather to the raion administration housed in the city itself.

Poltava's government consists of the 50-member Poltava City Council (Полтавська Міська рада) which is headed by the Secretary (currently Oleksandr Kozub). The city's current mayor is Oleksandr Mamay, who was sworn in on 4 November 2010 after being elected with more than 61 percent of the vote. In 2015 he was re-elected as a candidate of Conscience of Ukraine with 62.9% in a second round of Mayoral election.

The territory of Poltava is divided into 3 urban districts:
 * 1) Shevchenkivskyi District,  to the south-west with an area of 2077 hectares and a population of 147,600 in 2005. It is a largely residential area and includes the city centre.
 * 2) Kyivskyi District, is the largest by area, comprising 5437 hectares, or 52.8% of the city total situated in the north and north-west. Its census in 2005 was 111,900. This district has a large industrial zone.
 * 3) Podilskyi District, to the east and south-east, in the valley of the Vorskla river, with an area of 2988 hectares and a population of 53,700 in 2005.

The village of Rozsoshentsi, Shcherbani, Tereshky, Kopyly and Suprunivka are officially considered to be outside the city, but constitute part of the Poltava agglomeration.

Culture
The centre of the old city is a semicircular Neoclassical square with the Tuscan column of cast iron (1805–11), commemorating the centenary of the Battle of Poltava and featuring 18 Swedish cannons captured in that battle. As Peter the Great celebrated his victory in the Saviour church, this 17th-century wooden shrine was carefully preserved to this day. The five-domed city cathedral, dedicated to the Exaltation of the Cross, is a superb monument of Cossack Baroque, built between 1699 and 1709. As a whole, the cathedral presents a unity which even the Neoclassical belltower has failed to mar. Another frothy Baroque church, dedicated to the Dormition of the Theotokos, was destroyed in 1934 and rebuilt in the 1990s.

A minor planet 2983 Poltava discovered in 1981 by Soviet astronomer Nikolai Stepanovich Chernykh is named after the city.

Sports
The most popular sport is football (soccer). Two professional football teams are based in the city: Vorskla Poltava in the Ukrainian Premier League and FC Poltava in the Second League. There are 3 stadiums in Poltava: Butovsky Vorskla Stadium (main city stadium), Dynamo Stadium are situated in the city centre and Lokomotiv Stadium which is situated in Podil district.

Notable people

 * Marie Bashkirtseff (1858–1884) Parisian painter and diarist.
 * Yitzhak Ben-Zvi (1884–1963) historian, longest-serving President of Israel from 1952 to 1963.
 * Hanka Bielicka (1915–2006) a Polish singer and actress, known by the name Hanna
 * Oleksandr Bilash (1931–2003) composer of lyric songs, ballads, operas, operettas and oratorios
 * Sofya Bogomolets (1856–1892) a Russian revolutionary and political prisoner.
 * Boris Brasol (1885-1963), lawyer and literary critic and a White Russian immigrant to the United States.
 * Moura Budberg (1892–1974), a Russian adventuress and suspected double agent of OGPU & MI6.
 * Nat Carr (1886–1944) an American character actor of the silent and early talking picture eras.
 * Gregori Chmara (1878–1970) a stage and film actor whose career spanned six decades.
 * Marusia Churai (1625–1653) a semi-mythical Ukrainian Baroque composer, poet, and singer.
 * Andriy Danylko (born 1973) stage name Verka Serduchka; a Ukrainian comedian, actor, and singer.
 * Sam Dreben (1878–1925), a highly decorated soldier in the US Army and a mercenary
 * Vladimir Gajdarov (1893–1978) a Russian film actor and star of Russian and German silent cinema.
 * Yuliy Ganf (1898–1973) a graphic artist, caricaturist, illustrator and poster designer.
 * Nikolai Gogol (1809–1852), a novelist, short story writer and playwright.
 * Alexander Gurwitsch (1874–1954) biologist and medical scientist; originated Morphogenetic field theory
 * Oksana Ivanenko (1906-1997) – Ukrainian children's writer and translator
 * Vladimir Ivashko (1932-1994), politician, acting General Secretary of the Communist Party of the Soviet Union
 * Philip Jaffe (1895–1980) a left-wing American businessman, editor and author.
 * Ernst Jedliczka (1855–1904) a Russian-German pianist, piano pedagogue, and music critic.
 * Mykola Karpov (1929–2003), Ukrainian playwright.
 * Dmitri Kessel (1902–1995), photojournalist, Life magazine 1944–1972 and war correspondent
 * Vera Kholodnaya (1893–1919) an actress of the early Imperial Russian cinema.
 * Yuri Kondratyuk (1897–1942), astronautics and spaceflight pioneer; foresaw reaching the Moon
 * Ivan Kotliarevsky (1769–1838) a Ukrainian writer, poet and playwright and social activist
 * Anatoly Lunacharsky (1875–1933) Russian Marxist revolutionary; Bolshevik Soviet people's Commissar
 * Anton Makarenko (1888–1939), educator, social worker and writer and top educational theorist
 * Yuri Levitin (1912–1993) a Soviet Russian composer of classical music.
 * Mykola Lysenko (1842–1912) composer, pianist, conductor; founder first Ukrainian classical music school
 * Patriarch Mstyslav (1898–1993), Ukrainian Orthodox Church hierarch
 * Matvei Muranov (1873–1959) a Ukrainian Bolshevik revolutionary, Soviet politician and statesman.
 * Panas Myrny (1849-1920) a Ukrainian prose writer and playwright
 * Jensen Noen (born 1987) a Los Angeles-based filmmaker, cinematographer and writer.
 * Oleksiy Onyschenko (born 1933) a philosopher, academic and culture theorist
 * Mikhail Ostrogradsky (1801–1862), a Ukrainian mathematician, mechanic and physicist
 * Olena Pchilka (1849–1930), a Ukrainian publisher, writer, ethnographer and civil activist.
 * Ivan Paskevich (1782-1856), Ukrainian military leader in Imperial Russian service.
 * Symon Petliura (1879–1926) a Ukrainian politician, journalist and military leader of Ukraine's struggle for independence following the fall of the Russian Empire in 1917.
 * Zhanna Prokhorenko (1940–2011) a Soviet and Russian actress
 * Sasha Putrya (1977–1989) Ukrainian artist, died aged 11 from leukemia.
 * Svitlana Pyrkalo (born 1976) a London-based writer, journalist and former BBC radio producer
 * Boris Schwanwitsch (1889–1957) a Russian entomologist who specialised in Lepidoptera.
 * Moshe Zvi Segal (1904–1985), rabbi and activist in Israeli organizations, including Etzel and Lechi.
 * Bert Shefter (1902–1999) a film composer who worked primarily in America.
 * Avraham Shlonsky (1900–1973), Israeli poet and editor
 * Hryhorii Skovoroda (1722–1794) a Ukrainian poet, philosopher and composer
 * Ivan Steshenko (1873–1918), a Ukrainian civic and political activist, writer and Govt. minister.
 * Maria Tarnowska (1877–1949), femme fatale, famously convicted of murder in Venice in 1910.
 * Elias Tcherikower (1881–1943), a Jewish historian of Judaism and the Jewish people.
 * Alina Treiger (born 1979) the first female rabbi to be ordained in Germany since WWII.
 * Yelena Ubiyvovk (1918–1942) a partisan and leader of a Komsomol cell during WWII.
 * Paisius Velichkovsky (1722–1794), Eastern Orthodox monk and theologian, promoted staretsdom
 * Nikolai Yaroshenko (1846–1898) a Ukrainian painter of portraits, genre paintings and drawings.

Sport

 * Leonid Bartenyev (1933–2021) a 100 metre team silver medallist at the 1956 and 1960 Summer Olympics
 * Sergei Diyev (born 1958) a Russian football manager and former player with over 600 club caps
 * Serhiy Konovalov (born 1972) a football coach and former footballer with 270 club caps and 22 for Ukraine
 * Oleksandr Melaschenko (born 1978) a football striker with over 320 club caps and 16 for Ukraine
 * Ruslan Rotan (born 1981) a former professional footballer with 382 club caps and 100 for Ukraine; now manager of the Ukraine national under-21 football team
 * Ivan Shariy (born 1957) is a former Soviet and Ukrainian footballer with over 500 club caps

Transportation

Poltava's transportation infrastructure consists of two major train stations with railway links to Kyiv, Kharkiv, and Kremenchuk. Poltava's Kyiv line is electrified and is used by the Poltava Express. The electrification of the Poltava-Kharkiv line was completed in August 2008.

The Avtovokzal serves as the city's intercity bus station. Buses for local municipal routes depart from "AC-2" (autostation No. 2 – along Shevchenko street) and "AC-3" (Zinkivska street). Local municipal routes are parked along the Taras Shevchenko Street. Marshrutka minibuses serve areas where regular bus access is unavailable; however, they are privately owned and cost more per ride. In addition, a 10-route trolleybus network of 72.6 km runs throughout the city. On the routes of the city go more than 50 units of trolleybuses.

Poltava is also served by an International Airport, situated outside the city limits near the village of Ivashky. The international highway M03, linking Poltava with Kyiv and Kharkiv, passes through the southern outskirts of the city. There is also a regional highway P-17 crossing Poltava and linking it with Kremenchuk and Sumy.

Education
Poltava has always been one of the most important science and education centres in Ukraine. Major universities and institutions of higher education include the following:
 * Poltava National Pedagogical University named after V. G. Korolenko
 * National University "Yuri Kondratyuk Poltava Polytechnic"
 * Poltava Agrarian State Academy
 * Poltava State Medical University
 * Poltava University of Economics and Trade
 * Poltava Military Institute of Connections
 * Poltava Law Institute of Yaroslav Mudryi National Law University
 * Poltava branch of the State Academy of Statistics, region and audit to the State Statistics Committee of Ukraine

Astronomy
 * Poltava gravimetric observatory (PGO) is situated a bit north from city centre (27–29 Miasoyedov St.). Its main work directions are measurements of Earth rotation, latitude variations (applying zenith stars observations, lunar occultation observations and other)
 * Observational station of PGO in rural area, some 20 km east along the M03-E40 highway. Radiotelescope URAN-2 (Ukrainian: УРАН-2) is situated there too.

Twin towns – sister cities
Poltava is twinned with:
 * 🇧🇬 Veliko Tarnovo, Bulgaria (1963)
 * 🇩🇪 Filderstadt, Germany
 * 🇩🇪 Ostfildern, Germany
 * 🇺🇸 Irondequoit, United States
 * 🇸🇪 Kristianstad, Sweden

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Poltava


text:
User:Tei~enwiki

WARNING!!'

M Your computer has do a illegal access to our WikiPedia user page and a far far Star will die now ( Actually, this its only a joke, the Super Nova Explosion its not implemented yet... please, smile :D

-//-

Si hablas español, mejor buscame en la wikipedia española. Ando un poco por ahi.

--User:Tei

title: User:Tei~enwiki


text:
Talk:Gravitational constant

Time variation
The "controversial" suggestion about a 5.9 day variation in G is not worth including. There is better evidence against it than for it. Plus, it is theoretically unsupported.

I suggest removal.

The astronomical evidence against time variation of G is worth mentioning. Wcmead3 (talk) Wcmead3 (talk) 04:09, 25 April 2023 (UTC)

Discrepancy in G measurements
This is an intriguing puzzle that has persisted for several years. If there is significant research reported that helps resolve the matter, it should be described and referenced in this article. Wcmead3 (talk) Wcmead3 (talk) 04:15, 25 April 2023 (UTC)

Gravity as a force
Newtonian gravity is a force in the usual sense of forces but, with general relativity, gravity is not a force, right? It instead determines curvature. To what extent should we be careful using the word "force" in this article? — Q uantling (talk | contribs) 12:30, 16 July 2024 (UTC)

title: Talk:Gravitational constant


text:
Talk:Homology

What are homology rings? I would think that homology is only defined in abelian categories. How else can you divide by the previous map's image? AxelBoldt

This ought to be a disambiguation page, with links to "homology (mathematics)" and to the (more well-known?) "homology (biology)". That it is not, can only mean that nowhere near enough biologists are found among Wikipedians. Since there are probably 20 times as many biologists as mathematicians, it shouldn't be that hard to recruit them by publicizing Wikipedia among them. Mike Hardy
 * Most biologists don't realize that you can edit wikipedia because they're used to having journal subscriptions... —Preceding unsigned comment added by 84.9.15.119 (talk) 02:07, 1 April 2009 (UTC)

So, does homology in biology have anything to do with homology in math at all? I figure they may be vaguely related by some form of topological data analysis. I'm sorry if this is a dumb question, but I'm feeling really confused about it. Daviddwd (talk) 23:09, 18 August 2014 (UTC)

title: Talk:Homology