General relativity

General relativity known as the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1915 and the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time, or spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present; the relation is specified by the Einstein field equations, a system of partial differential equations. Some predictions of general relativity differ from those of classical physics concerning the passage of time, the geometry of space, the motion of bodies in free fall, the propagation of light. Examples of such differences include gravitational time dilation, gravitational lensing, the gravitational redshift of light, the gravitational time delay; the predictions of general relativity in relation to classical physics have been confirmed in all observations and experiments to date.

Although general relativity is not the only relativistic theory of gravity, it is the simplest theory, consistent with experimental data. However, unanswered questions remain, the most fundamental being how general relativity can be reconciled with the laws of quantum physics to produce a complete and self-consistent theory of quantum gravity. Einstein's theory has important astrophysical implications. For example, it implies the existence of black holes—regions of space in which space and time are distorted in such a way that nothing, not light, can escape—as an end-state for massive stars. There is ample evidence that the intense radiation emitted by certain kinds of astronomical objects is due to black holes. For example and active galactic nuclei result from the presence of stellar black holes and supermassive black holes, respectively; the bending of light by gravity can lead to the phenomenon of gravitational lensing, in which multiple images of the same distant astronomical object are visible in the sky.

General relativity predicts the existence of gravitational waves, which have since been observed directly by the physics collaboration LIGO. In addition, general relativity is the basis of current cosmological models of a expanding universe. Acknowledged as a theory of extraordinary beauty, general relativity has been described as the most beautiful of all existing physical theories. Soon after publishing the special theory of relativity in 1905, Einstein started thinking about how to incorporate gravity into his new relativistic framework. In 1907, beginning with a simple thought experiment involving an observer in free fall, he embarked on what would be an eight-year search for a relativistic theory of gravity. After numerous detours and false starts, his work culminated in the presentation to the Prussian Academy of Science in November 1915 of what are now known as the Einstein field equations; these equations specify how the geometry of space and time is influenced by whatever matter and radiation are present, form the core of Einstein's general theory of relativity.

The 19th century mathematician Bernhard Riemann's non-Euclidean geometry, called Riemannian Geometry, provided the key mathematical framework which Einstein fit his physical ideas of gravity on, enabled him to develop general relativity. The Einstein field equations are nonlinear and difficult to solve. Einstein used approximation methods in working out initial predictions of the theory, but as early as 1916, the astrophysicist Karl Schwarzschild found the first non-trivial exact solution to the Einstein field equations, the Schwarzschild metric. This solution laid the groundwork for the description of the final stages of gravitational collapse, the objects known today as black holes. In the same year, the first steps towards generalizing Schwarzschild's solution to electrically charged objects were taken, which resulted in the Reissner–Nordström solution, now associated with electrically charged black holes. In 1917, Einstein applied his theory to the universe as a whole, initiating the field of relativistic cosmology.

In line with contemporary thinking, he assumed a static universe, adding a new parameter to his original field equations—the cosmological constant—to match that observational presumption. By 1929, the work of Hubble and others had shown that our universe is expanding; this is described by the expanding cosmological solutions found by Friedmann in 1922, which do not require a cosmological constant. Lemaître used these solutions to formulate the earliest version of the Big Bang models, in which our universe has evolved from an hot and dense earlier state. Einstein declared the cosmological constant the biggest blunder of his life. During that period, general relativity remained something of a curiosity among physical theories, it was superior to Newtonian gravity, being consistent with special relativity and accounting for several effects unexplained by the Newtonian theory. Einstein himself had shown in 1915 how his theory explained the anomalous perihelion advance of the planet Mercury without any arbitrary parameters.

A 1919 expedition led by Eddington confirmed general relativity's prediction for the deflection of starlight by the Sun during the total solar eclipse of May 29, 1919, making Einstein famous. Yet the theory entered the mainstream of theoretical physics and astrophysics only with the developments between 1960 and 1975, now known as the golden age of general relativity. Physicists began to understand the concept of a black hole, to identify quasars as one

Nguyễn Phúc Lan

Nguyễn Phúc Lan was one of the Nguyễn lords who ruled south Vietnam from the city of Phú Xuân from 1635 to 1648. During his rule the Trịnh–Nguyễn War continued. Nguyễn Phúc Lan was the second son of Nguyễn Phúc Nguyên, his father died in the midst of the war by Trịnh Tráng to conquer the southern provinces. Unwilling to make peace, Nguyễn Phúc Lan continued his father's policies of maintaining a strong defensive position on the great walls while continuing friendly relations with the Portuguese and expanding south into Cambodian and Champa territory. Following after his grandfather, he took the title of Vuong. In 1640, famed Jesuit missionary Alexandre de Rhodes returned to Vietnam, this time to the Nguyễn court at Phú Xuân, he had been forced to leave the court at Hanoi ten years earlier but now he was back, reasoning that rules against him in Hanoi did not apply in Phú Xuân. He began work on converting people to the Roman Catholic building churches. However, after six years, Nguyễn Phúc Lan came to the same conclusion as Trịnh Tráng had: that de Rhodes and the Catholic Church represented a threat to his rule.

De Rhodes was condemned to death but the sentence was reduced to exile on pain of death should he return. De Rhodes never returned to Vietnam but Vietnamese Catholics remained and continued to practice their new religion. After a break of nine years, Trịnh Tráng launched a new major assault in 1642; this time they had their own European cannons, purchased from the Dutch. They had modern Dutch ships to lead their fleet. At first the assault went well and the first of the great walls was breached; the attack was renewed in 1643 but the second wall could not be taken. At sea, once again the Nguyễn fleet defeated the Royal fleet; the offensive halted and the Trịnh withdrew. On March 19, 1648, Nguyễn Phúc Lan died and was succeeded by his son, Nguyễn Phúc Tần, 28 years old. Lê dynasty List of Vietnamese dynasties Encyclopedia of Asian History, Volume 3 1988. Charles Scribner's Sons, New York Genealogy of the Royal Nguyen Family The Encyclopedia of Military History by R. Ernest Dupuy and Trevor N. Dupuy.

Harper & Row

Diego Carlos Santos Silva

Diego Carlos Santos Silva, or Diego Carlos, is a Brazilian professional defender who plays for Spanish club Sevilla FC. Diego began his senior career with Desportivo Brasil in the 2012–13 season. On 1 January 2013, Diego was sent out on loan to São Paulo. Diego spent the latter portion of the 2013–14 season out on loan at Paulista. Diego spent about a month out on loan at Madureira On 2 July 2014, Diego was sold to Estoril. In September 2014, Diego was loaned to FC Porto, he only played for the B team. In June 2016, it was announced; the transfer fee paid to Estoril was estimated at €2 million. On 14 January 2018, during a Ligue 1 match between Nantes and Paris Saint-Germain, referee Tony Chapron appeared to kick Diego following a collision, before sending him off for a second bookable offence. Chapron, suspended by the French Football Federation, admitted his mistake and asked for Diego Carlos' second yellow card to be rescinded; as a result, French football league withdrew the second yellow card.

On 31 May 2019, Spanish club Sevilla FC announced they had reached an agreement with Nantes for the transfer of Diego Carlos. As of match played 25 January 2020 Diego Carlos at ForaDeJogo Diego Carlos at Soccerway