Relativity During World War I Eddington was Secretary of the Royal Astronomical Society, which meant he was the first to receive a series of letters and papers from Willem de Sitter regarding Einstein’s theory of general relativity. Eddington was fortunate in being not only one of the few astronomers with the mathematical skills to understand general relativity, but (owing to his internationalist and pacifist views) one of the few at the time who was still interested in pursuing a theory developed by a German physicist. He quickly became the chief supporter and expositor of relativity in Britain.
He and Astronomer Royal Frank Watson Dyson organized two expeditions to observe a solar eclipse in 1919 to make the first empirical test of Einstein’s theory: the measurement of the deflection of light by the sun's gravitational field. In fact, it was Dyson’s argument for the indispensability of Eddington’s expertise in this test that allowed him to escape prison during the war. One of Eddington's photographs of the total solar eclipse of 29 May 1919, presented in his 1920 paper announcing its success, confirming Einstein's theory that light "bends" After the war, Eddington travelled to the island of Príncipe near Africa to watch the solar eclipse of 29 May 1919.
During the eclipse, he took pictures of the stars in the region around the Sun. According to the theory of general relativity, stars with light rays that passed near the Sun would appear to have been slightly shifted because their light had been curved by its gravitational field. This effect is noticeable only during eclipses, since otherwise the Sun's brightness obscures the affected stars. Eddington showed that Newtonian gravitation could be interpreted to predict half the shift predicted by Einstein.
Eddington's observations published the next year confirmed Einstein's theory, and were hailed at the time as a conclusive proof of general relativity over the Newtonian model. The news was reported in newspapers all over the world as a major story. Afterward, Eddington embarked on a campaign to popularize relativity and the expedition as landmarks both in scientific development and international scientific relations.
Unification or Death (Serbian: Уједињење или смрт, Ujedinjenje ili smrt), unofficially known as the Black Hand (Црна рука, Crna ruka), was a secret military society formed by members of the Serbian army in the Kingdom of Serbia, which was founded on 6 September 1901. It was intent on uniting all of the territories containing significant Serbpopulations annexed by Austria-Hungary. Through its purported connections to the June 1914 assassination in Sarajevo of Franz Ferdinand, Archduke of Austria, the Black Hand may have been one of the principal catalysts to the start of World War I, fueling theJuly Crisis of 1914 and giving Austria-Hungary a pretext to invade Serbia.
Gavrilo Princip was born in Obljaj, a poor part of Bosnia, which was then in the Austria-Hungary empire. His parents, Petar, a postman, and Marija (née Mićić) had nine children, six of whom died in infancy. His impoverished parents could not provide for him and sent him to live with an older brother in Zagreb, now the capital of Croatia.
On October 6th 1908, Bosnia-Herzegovina was declared a part of the Austro-Hungarian Empire by Emperor Franz Joseph. This created a stir among Slavic people of southern Europe and the Russian Tsar who opposed the annexation. On 28 June 1914, Gavrilo Princip participated in theassassination in Sarajevo of the Austrian Archduke. General Oskar Potiorek, Governor of the Austrian provinces of Bosnia and Herzegovina had invited Franz Ferdinand and Countess Sophie to
The Archduke knew that the visit would be dangerous, knowing his uncle, Emperor Franz Josef, had been the subject of an assassination attempt by the Black Hand in 1911.Just before 10 a.m. on Sunday, the royal couple arrived in Sarajevo by train. The six conspirators lined the route. The first conspirator on the route to see the royal car was Bosniak Muhamed Mehmedbašić. Standing by the Austro-Hungarian Bank, Mehmedbašić lost his nerve and allowed the car to pass without taking action. At 10:15 a.m., when the six car procession passed the central police station, nineteen-year-old student Nedeljko Čabrinović hurled a hand grenade at the Archduke's car. The driver accelerated when he saw the object flying towards him, but the bomb had a 10 second delay and exploded under the wheel of the fourth car.
.Franz Ferdinand later decided to go to the hospital and visit the victims of Čabrinović's failed bombing attempt. In order to avoid the city centre, General Oskar Potiorek decided that the royal car should travel straight along the Appel Quay to the Sarajevo Hospital. However, Potiorek forgot to inform the driver, Leopold Loyka, about this decision. On the way to the hospital, Loyka took a right turn into Franz Josef Street.Princip was standing near Moritz Schiller's cafe, having apparently given up, when he spotted Franz Ferdinand's car as it drove past, having taken the wrong turn. After realizing the mistake, the driver put his foot on the brake, and began to back up. In doing so the engine of the car stalled and the gears locked, giving Princip his opportunity. Princip stepped forward, drew his FN Model 1910pistol, pistol-whipped a nearby pedestrian, and at a distance of about 1.5 m (five feet), fired twice into the car. Franz Ferdinand was hit in the neck and Sophie (who instinctively covered Franz's body with her own after the first shot) in the abdomen, and they both died before 11 a.m.
Newton's law of universal gravitation states that every point mass in the universe attracts every other point mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. (Separately it was shown that large spherically symmetrical masses attract and are attracted as if all their mass were concentrated at their centers.) This is a general physical law derived from empirical observations by what Newton called induction. It is a part of classical mechanics and was formulated in Newton's work Philosophiae Naturalis Principia Mathematica ("the Principia"), first published on 5 July 1687. (When Newton's book was presented in 1686 to the Royal Society, Robert Hooke made a claim that Newton had obtained the inverse square law from him – see History section below.) In modern language, the law states the following
General relativity, or the general theory of relativity, is the geometric theory of gravitation published by Albert Einstein in 1916 and the current description of gravitation in modern physics. General relativity generalises special relativity and 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.
Albert Einstein developed the theories of special and general relativity. Picture from 1921.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 is present, and form the core of Einstein's general theory of relativity.
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 reproduce that "observation". By 1929, however, the work of Hubble and others had shown that our universe is expanding. This is readily 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 extremely hot and dense earlier state. Einstein later declared the cosmological constant the biggest blunder of his life.
The simplest explanation for dark energy is that it is simply the "cost of having space": that is, a volume of space has some intrinsic, fundamental energy. This is the cosmological constant, sometimes called Lambda (hence Lambda-CDM model) after the Greek letter Λ, the symbol used to mathematically represent this quantity. Since energy and mass are related by E = mc2, Einstein's theory ofgeneral relativity predicts that this energy will have a gravitational effect. It is sometimes called a vacuum energy because it is the energy density of empty vacuum. In fact, most theories of particle physics predict vacuum fluctuations that would give the vacuum this sort of energy. This is related to the Casimir Effect, in which there is a small suction into regions where virtual particles are geometrically inhibited from forming (e.g. between plates with tiny separation). The cosmological constant is estimated by cosmologists to be on the order of 10−29g/cm3, or about 10−120 in reduced Planck units. Particle physics predicts a natural value of 1 in reduced Planck units, leading to a large discrepancy.
Dark energy In physical cosmology and astronomy, dark energy is a hypothetical form of energy that permeates all of space and tends to accelerate the expansion of the universe. Dark energy is the most accepted hypothesis to explain observations since the 1990s that indicate that the universe is expanding at an accelerating rate. In the standard model of cosmology, dark energy currently accounts for 73% of the total mass-energy of the universe.
Shot dead After learning that the assassination had been unsuccessful Princip went to a nearby food shop (Schiller's delicatessen). When Princip emerged, he saw Franz Ferdinand's open car reversing after having taken the wrong turn as it drove past, near the Latin Bridge. After realizing the mistake, the driver put his foot on the brake, and began to back up. In doing so the engine of the car stalled and the gears locked, giving Princip his opportunity. Princip stepped forward and fired two shots from a distance of about one and a half metres using a Belgian-made 9×17mm (.380 ACP) Fabrique Nationale model 1910 semi-automatic pistol. Pistol serial numbers 19074, 19075, 19120 and 19126 were supplied to the assassins; Princip used #19074. According to Albertini, "the first bullet wounded the Archduke in the jugular vein, the second inflicted an abdominal wound on the Duchess." Princip was immediately arrested. At his sentencing, Princip stated that his intention had been to kill Governor Potiorek, rather than Sophie. Both victims remained seated upright, but dying while being driven to the Governor's residence for medical treatment. As reported by Count Harrach, Franz Ferdinand's last words were "Sophie, Sophie! Don't die! Live for our children!" followed by six or seven utterances of "It is nothing." in response to Harrach's inquiry as to Franz Ferdinand's injury. These utterances were followed by a long death rattle. Sophie was dead on arrival at the Governor's residence. Franz Ferdinand died 10 minutes later.
In the physics of general relativity, the equivalence principle is any of several related concepts dealing with the equivalence of gravitational and inertial mass, and to Albert Einstein's assertion that the gravitational "force" as experienced locally while standing on a massive body (such as the Earth) is actually the same as the pseudo-force experienced by an observer in a non-inertial (accelerated) frame of reference.
On Sunday, 28 June 1914, at approximately 10:45 am, Franz Ferdinand and his wife were killed in Sarajevo, the capital of the Austro-Hungarian province of Bosnia and Herzegovina, by Gavrilo Princip, 19 at the time, a member of Young Bosnia and one of a group of assassins organized by the Black Hand. The event led to a chain of events that eventually triggered World War I.