Gravitational collapse is the contraction of an astronomical object due to the influence of its own gravity, which tends to draw matter inward toward the center of gravity. Gravitational collapse is a fundamental mechanism for structure formation in the universe. Over time an initial smooth distribution of matter will collapse to form pockets of higher density creating a hierarchy of condensed structures such as clusters of galaxies, stellar groups and planets. A star is born through the gradual gravitational collapse of a cloud of interstellar matter; the compression caused by the collapse raises the temperature until thermonuclear fusion occurs at the center of the star, at which point the collapse comes to a halt as the outward thermal pressure balances the gravitational forces. The star exists in a state of dynamic equilibrium. Once all its energy sources are exhausted, a star will again collapse until it reaches a new equilibrium state. An interstellar cloud of gas will remain in hydrostatic equilibrium as long as the kinetic energy of the gas pressure is in balance with the potential energy of the internal gravitational force.
Mathematically this is expressed using the virial theorem, which states that, to maintain equilibrium, the gravitational potential energy must equal twice the internal thermal energy. If a pocket of gas is massive enough that the gas pressure is insufficient to support it, the cloud will undergo gravitational collapse; the mass above which a cloud will undergo such collapse is called the Jeans mass. This mass depends on the temperature and density of the cloud, but is thousands to tens of thousands of solar masses. At what is called the death of the star, it will undergo a contraction that can be halted only if it reaches a new state of equilibrium. Depending on the mass during its lifetime, these stellar remnants can take one of three forms: White dwarfs, in which gravity is opposed by electron degeneracy pressure Neutron stars, in which gravity is opposed by neutron degeneracy pressure and short-range repulsive neutron–neutron interactions mediated by the strong force Black hole, in which there is no force strong enough to resist gravitational collapse The collapse of the stellar core to a white dwarf takes place over tens of thousands of years, while the star blows off its outer envelope to form a planetary nebula.
If it has a companion star, a white dwarf-sized object can accrete matter from the companion star. Before it reaches the Chandrasekhar limit, the increasing density and temperature within a carbon-oxygen white dwarf initiates a new round of nuclear fusion, not regulated because the star's weight is supported by degeneracy rather than thermal pressure, allowing temperature to rise exponentially; the resulting runaway carbon detonation blows the star apart in a Type Ia supernova. Neutron stars are formed by gravitational collapse of the cores of larger stars, are the remnant of other types of supernova, they are so compact that a Newtonian description is inadequate for an accurate treatment, which requires the use of Einstein's general relativity. According to Einstein's theory, for larger stars, above the Landau-Oppenheimer-Volkoff limit known as the Tolman–Oppenheimer–Volkoff limit no known form of cold matter can provide the force needed to oppose gravity in a new dynamical equilibrium. Hence, the collapse continues with nothing to stop it.
Once a body collapses to within its Schwarzschild radius it forms what is called a black hole, meaning a space-time region from which not light can escape. It follows from a theorem of Roger Penrose that the subsequent formation of some kind of singularity is inevitable. According to Penrose's cosmic censorship hypothesis, the singularity will be confined within the event horizon bounding the black hole, so the space-time region outside will still have a well behaved geometry, with strong but finite curvature, expected to evolve towards a rather simple form describable by the historic Schwarzschild metric in the spherical limit and by the more discovered Kerr metric if angular momentum is present. On the other hand, the nature of the kind of singularity to be expected inside a black hole remains rather controversial. According to some theories, at a stage, the collapsing object will reach the maximum possible energy density for a certain volume of space or the Planck density; this is. There are competing theories as to what occurs at this point, but it can no longer be considered gravitational collapse at that stage.
The radii of larger mass neutron stars are estimated to be about 12-km, or 2.0 times their equivalent Schwarzschild radius. It might be thought that a sufficiently massive neutron star could exist within its Schwarzschild radius and appear like a black hole without having all the mass compressed to a singularity at the center. Within the event horizon, matter would have to move outward faster than the speed of light in order to remain stable and avoid collapsing to the center. No physical force therefore can prevent a star smaller than 1.0 SR from collapsing to a singularity. A model for nonspherical collapse in general relativity with emission of matter and gravitational waves has been presented. Big Crunch Gravitational compression Stellar evolution Thermal runawa
Gravity, or gravitation, is a natural phenomenon by which all things with mass or energy—including planets, stars and light—are brought toward one another. On Earth, gravity gives weight to physical objects, the Moon's gravity causes the ocean tides; the gravitational attraction of the original gaseous matter present in the Universe caused it to begin coalescing, forming stars – and for the stars to group together 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 on farther objects. Gravity is most described by the general theory of relativity which describes gravity not as a force, but as a consequence of the curvature of spacetime caused by the uneven distribution of mass; the most extreme example of this curvature of spacetime is a black hole, from which nothing—not 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 which causes any two bodies to be attracted to each other, with the force proportional to the product of their masses and inversely proportional to the square of the distance between them.
Gravity is the weakest of the four fundamental forces of physics 1038 times weaker than the strong force, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak force. As a consequence, it has no significant influence at the level of subatomic particles. In contrast, it is the dominant force at the macroscopic scale, is the cause of the formation and trajectory of astronomical bodies. For example, gravity causes the Earth and the other planets to orbit the Sun, it causes the Moon to orbit the Earth, causes the formation of tides, the formation and evolution of the Solar System and galaxies; the earliest instance of gravity in the Universe in the form of quantum gravity, supergravity or a gravitational singularity, along with ordinary space and time, developed during the Planck epoch from a primeval state, such as a false vacuum, quantum vacuum or virtual particle, in a unknown manner. Attempts 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 with the other three forces of physics, are a current area of research.
Archimedes discovered the center of gravity of a triangle. He postulated that if the centers of gravity of two equal weights wasn't the same, it would be located in the middle of the line that joins them; the Roman architect and engineer Vitruvius in De Architectura postulated that gravity of an object didn't depend on weight but its "nature". Aryabhata first identified the force to explain why objects are not thrown out when the earth rotates. Brahmagupta described gravity as an attractive force and used the term "gruhtvaakarshan" for gravity. Modern work on gravitational theory began with the work of Galileo Galilei in the late 16th and early 17th centuries. In his famous experiment dropping balls from the Tower of Pisa, with careful measurements of balls rolling down inclines, Galileo showed that gravitational acceleration is the same for all objects; this was a major departure from Aristotle's belief that heavier objects have a higher gravitational acceleration. Galileo postulated air resistance as the reason that objects with less mass fall more in an atmosphere.
Galileo's work set the stage for the formulation of Newton's theory of gravity. In 1687, English mathematician Sir Isaac Newton published Principia, which hypothesizes the inverse-square law of universal gravitation. In his own words, "I deduced that the forces which keep the planets in their orbs must reciprocally as the squares of their distances from the centers about which they revolve: and thereby compared the force requisite to keep the Moon in her Orb with the force of gravity at the surface of the Earth; the equation is the following: F = G m 1 m 2 r 2 Where F is the force, m1 and m2 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 theory enjoyed its greatest success when it was used to predict the existence of Neptune based on motions of Uranus that could not be accounted for by the actions of the other planets. Calculations by both John Couch Adams and Urbain Le Verrier predicted the general position of the planet, Le Verrier's calculations are what led Johann Gottfried Galle to the discovery of Neptune.
A discrepancy in Mercury's orbit pointed out flaws in Newton's theory. By the end of the 19th century, it was known that its orbit showed slight perturbations that could not be accounted for under Newton's theory, but all searches for another perturbing body had been fruitless; the issue was resolved in 1915 by Albert Einstein's new theory of general relativity, which accounted for the small discrepancy in Mercury's orbit. This discrepancy was the advance in the perihelion of Mercury of 42.98 arcseconds per century. Although Newton's theory has been superseded by Einstein's general relativity, most modern non-relativistic gravitational calculations are still made using Newton
David Hilbert was a German mathematician and one of the most influential and universal mathematicians of the 19th and early 20th centuries. Hilbert discovered and developed a broad range of fundamental ideas in many areas, including invariant theory, calculus of variations, commutative algebra, algebraic number theory, the foundations of geometry, spectral theory of operators and its application to integral equations, mathematical physics, foundations of mathematics. Hilbert warmly defended Georg Cantor's set theory and transfinite numbers. A famous example of his leadership in mathematics is his 1900 presentation of a collection of problems that set the course for much of the mathematical research of the 20th century. Hilbert and his students contributed to establishing rigor and developed important tools used in modern mathematical physics. Hilbert is known as one of the founders of proof theory and mathematical logic, as well as for being among the first to distinguish between mathematics and metamathematics.
Hilbert, the first of two children of Otto and Maria Therese Hilbert, was born in the Province of Prussia, Kingdom of Prussia, either in Königsberg or in Wehlau near Königsberg where his father worked at the time of his birth. In late 1872, Hilbert entered the Friedrichskolleg Gymnasium. Upon graduation, in autumn 1880, Hilbert enrolled at the University of Königsberg, the "Albertina". In early 1882, Hermann Minkowski, returned to Königsberg and entered the university. Hilbert developed a lifelong friendship with the gifted Minkowski. In 1884, Adolf Hurwitz arrived from Göttingen as an Extraordinarius. An intense and fruitful scientific exchange among the three began, Minkowski and Hilbert would exercise a reciprocal influence over each other at various times in their scientific careers. Hilbert obtained his doctorate in 1885, with a dissertation, written under Ferdinand von Lindemann, titled Über invariante Eigenschaften spezieller binärer Formen, insbesondere der Kugelfunktionen. Hilbert remained at the University of Königsberg as a Privatdozent from 1886 to 1895.
In 1895, as a result of intervention on his behalf by Felix Klein, he obtained the position of Professor of Mathematics at the University of Göttingen. During the Klein and Hilbert years, Göttingen became the preeminent institution in the mathematical world, he remained there for the rest of his life. Among Hilbert's students were Hermann Weyl, chess champion Emanuel Lasker, Ernst Zermelo, Carl Gustav Hempel. John von Neumann was his assistant. At the University of Göttingen, Hilbert was surrounded by a social circle of some of the most important mathematicians of the 20th century, such as Emmy Noether and Alonzo Church. Among his 69 Ph. D. students in Göttingen were many who became famous mathematicians, including: Otto Blumenthal, Felix Bernstein, Hermann Weyl, Richard Courant, Erich Hecke, Hugo Steinhaus, Wilhelm Ackermann. Between 1902 and 1939 Hilbert was editor of the Mathematische Annalen, the leading mathematical journal of the time. "Good, he did not have enough imagination to become a mathematician".
Around 1925, Hilbert developed pernicious anemia, a then-untreatable vitamin deficiency whose primary symptom is exhaustion. Those forced out included Hermann Weyl, Emmy Noether and Edmund Landau. One who had to leave Germany, Paul Bernays, had collaborated with Hilbert in mathematical logic, co-authored with him the important book Grundlagen der Mathematik; this was a sequel to the Hilbert-Ackermann book Principles of Mathematical Logic from 1928. Hermann Weyl's successor was Helmut Hasse. About a year Hilbert attended a banquet and was seated next to the new Minister of Education, Bernhard Rust. Rust asked whether "the Mathematical Institute suffered so much because of the departure of the Jews". Hilbert replied, "Suffered? It doesn't exist any longer, does it!" By the time Hilbert died in 1943, the Nazis had nearly restaffed the university, as many of the former faculty had either been Jewish or married to Jews. Hilbert's funeral was attended by fewer than a dozen people, only two of whom were fellow academics, among them Arnold Sommerfeld, a theoretical physicist and a native of Königsberg.
News of his death only became known to the wider world six months. The epitaph on his tombstone in Göttingen consists of the famous lines he spoke at the conclusion of his retirement address to the Society of German Scientists and Physicians on 8 September 1930; the words were given in response to the Latin maxim: "Ignoramus et ignorabimus" or "We do not know, we shall not know": Wir müssen wissen. Wir werden wissen. In English: We mus
Albert Einstein was a German-born theoretical physicist who developed the theory of relativity, one of the two pillars of modern physics. His work is known for its influence on the philosophy of science, he is best known to the general public for his mass–energy equivalence formula E = mc2, dubbed "the world's most famous equation". He received the 1921 Nobel Prize in Physics "for his services to theoretical physics, for his discovery of the law of the photoelectric effect", a pivotal step in the development of quantum theory. Near the beginning of his career, Einstein thought that Newtonian mechanics was no longer enough to reconcile the laws of classical mechanics with the laws of the electromagnetic field; this led him to develop his special theory of relativity during his time at the Swiss Patent Office in Bern. However, he realized that the principle of relativity could be extended to gravitational fields, he published a paper on general relativity in 1916 with his theory of gravitation.
He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules. He investigated the thermal properties of light which laid the foundation of the photon theory of light. In 1917, he applied the general theory of relativity to model the structure of the universe. Except for one year in Prague, Einstein lived in Switzerland between 1895 and 1914, during which time he renounced his German citizenship in 1896 received his academic diploma from the Swiss federal polytechnic school in Zürich in 1900. After being stateless for more than five years, he acquired Swiss citizenship in 1901, which he kept for the rest of his life. In 1905, he was awarded a PhD by the University of Zurich; the same year, he published four groundbreaking papers during his renowned annus mirabilis which brought him to the notice of the academic world at the age of 26. Einstein taught theoretical physics at Zurich between 1912 and 1914 before he left for Berlin, where he was elected to the Prussian Academy of Sciences.
In 1933, while Einstein was visiting the United States, Adolf Hitler came to power. Because of his Jewish background, Einstein did not return to Germany, he settled in the United States and became an American citizen in 1940. On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential development of "extremely powerful bombs of a new type" and recommending that the US begin similar research; this led to the Manhattan Project. Einstein supported the Allies, but he denounced the idea of using nuclear fission as a weapon, he signed the Russell–Einstein Manifesto with British philosopher Bertrand Russell, which highlighted the danger of nuclear weapons. He was affiliated with the Institute for Advanced Study in Princeton, New Jersey, until his death in 1955. Einstein published more than 150 non-scientific works, his intellectual achievements and originality have made the word "Einstein" synonymous with "genius". Albert Einstein was born in Ulm, in the Kingdom of Württemberg in the German Empire, on 14 March 1879.
His parents were Hermann Einstein, a salesman and engineer, Pauline Koch. In 1880, the family moved to Munich, where Einstein's father and his uncle Jakob founded Elektrotechnische Fabrik J. Einstein & Cie, a company that manufactured electrical equipment based on direct current; the Einsteins were non-observant Ashkenazi Jews, Albert attended a Catholic elementary school in Munich, from the age of 5, for three years. At the age of 8, he was transferred to the Luitpold Gymnasium, where he received advanced primary and secondary school education until he left the German Empire seven years later. In 1894, Hermann and Jakob's company lost a bid to supply the city of Munich with electrical lighting because they lacked the capital to convert their equipment from the direct current standard to the more efficient alternating current standard; the loss forced the sale of the Munich factory. In search of business, the Einstein family moved to Italy, first to Milan and a few months to Pavia; when the family moved to Pavia, Einstein 15, stayed in Munich to finish his studies at the Luitpold Gymnasium.
His father intended for him to pursue electrical engineering, but Einstein clashed with authorities and resented the school's regimen and teaching method. He wrote that the spirit of learning and creative thought was lost in strict rote learning. At the end of December 1894, he travelled to Italy to join his family in Pavia, convincing the school to let him go by using a doctor's note. During his time in Italy he wrote a short essay with the title "On the Investigation of the State of the Ether in a Magnetic Field". Einstein always excelled at math and physics from a young age, reaching a mathematical level years ahead of his peers; the twelve year old Einstein taught himself algebra and Euclidean geometry over a single summer. Einstein independently discovered his own original proof of the Pythagorean theorem at age 12. A family tutor Max Talmud says that after he had given the 12 year old Einstein a geometry textbook, after a short time " had worked through the whole book, he thereupon devoted himself to higher mathematics...
Soon the flight of his mathematical genius was so high I could not follow." His passion for geometry and algebra led the twelve year old to become convinced that nature could be understood as a "mathematical structure". Einstein started teaching himself calculus at
Vacuum is space devoid of matter. The word stems from the Latin adjective vacuus for "vacant" or "void". An approximation to such vacuum is a region with a gaseous pressure much less than atmospheric pressure. Physicists discuss ideal test results that would occur in a perfect vacuum, which they sometimes call "vacuum" or free space, use the term partial vacuum to refer to an actual imperfect vacuum as one might have in a laboratory or in space. In engineering and applied physics on the other hand, vacuum refers to any space in which the pressure is lower than atmospheric pressure; the Latin term in vacuo is used to describe an object, surrounded by a vacuum. The quality of a partial vacuum refers to how it approaches a perfect vacuum. Other things equal, lower gas pressure means higher-quality vacuum. For example, a typical vacuum cleaner produces enough suction to reduce air pressure by around 20%. Much higher-quality vacuums are possible. Ultra-high vacuum chambers, common in chemistry and engineering, operate below one trillionth of atmospheric pressure, can reach around 100 particles/cm3.
Outer space is an higher-quality vacuum, with the equivalent of just a few hydrogen atoms per cubic meter on average in intergalactic space. According to modern understanding if all matter could be removed from a volume, it would still not be "empty" due to vacuum fluctuations, dark energy, transiting gamma rays, cosmic rays and other phenomena in quantum physics. In the study of electromagnetism in the 19th century, vacuum was thought to be filled with a medium called aether. In modern particle physics, the vacuum state is considered the ground state of a field. Vacuum has been a frequent topic of philosophical debate since ancient Greek times, but was not studied empirically until the 17th century. Evangelista Torricelli produced the first laboratory vacuum in 1643, other experimental techniques were developed as a result of his theories of atmospheric pressure. A torricellian vacuum is created by filling a tall glass container closed at one end with mercury, inverting it in a bowl to contain the mercury.
Vacuum became a valuable industrial tool in the 20th century with the introduction of incandescent light bulbs and vacuum tubes, a wide array of vacuum technology has since become available. The recent development of human spaceflight has raised interest in the impact of vacuum on human health, on life forms in general; the word vacuum comes from Latin, meaning'an empty space, void', noun use of neuter of vacuus, meaning "empty", related to vacare, meaning "be empty". Vacuum is one of the few words in the English language that contains two consecutive letters'u'. There has been much dispute over whether such a thing as a vacuum can exist. Ancient Greek philosophers debated the existence of a vacuum, or void, in the context of atomism, which posited void and atom as the fundamental explanatory elements of physics. Following Plato the abstract concept of a featureless void faced considerable skepticism: it could not be apprehended by the senses, it could not, provide additional explanatory power beyond the physical volume with which it was commensurate and, by definition, it was quite nothing at all, which cannot rightly be said to exist.
Aristotle believed that no void could occur because the denser surrounding material continuum would fill any incipient rarity that might give rise to a void. In his Physics, book IV, Aristotle offered numerous arguments against the void: for example, that motion through a medium which offered no impediment could continue ad infinitum, there being no reason that something would come to rest anywhere in particular. Although Lucretius argued for the existence of vacuum in the first century BC and Hero of Alexandria tried unsuccessfully to create an artificial vacuum in the first century AD, it was European scholars such as Roger Bacon, Blasius of Parma and Walter Burley in the 13th and 14th century who focused considerable attention on these issues. Following Stoic physics in this instance, scholars from the 14th century onward departed from the Aristotelian perspective in favor of a supernatural void beyond the confines of the cosmos itself, a conclusion acknowledged by the 17th century, which helped to segregate natural and theological concerns.
Two thousand years after Plato, René Descartes proposed a geometrically based alternative theory of atomism, without the problematic nothing–everything dichotomy of void and atom. Although Descartes agreed with the contemporary position, that a vacuum does not occur in nature, the success of his namesake coordinate system and more implicitly, the spatial–corporeal component of his metaphysics would come to define the philosophically modern notion of empty space as a quantified extension of volume. By the ancient definition however, directional information and magnitude were conceptually distinct. In the medieval Middle Eastern world, the physicist and Islamic scholar, Al-Farabi, conducted a small experiment concerning the existence of vacuum, in which he investigated handheld plungers in water, he concluded that air's volume can expand to fill available space, he suggested that the concept of perfect vacuum was incoherent. However, according to Nader El-Bizri, the physicist Ibn al-Haytham and the Mu'tazili theologians disagreed with Aristotle and Al-Farabi, they supported the existence of a void.
Using geometry, Ibn al-Haytham mathematically demonstrated that place is the imagined three-dimensional void between the inner surfaces of a containing body. According to Ahmad Dallal, Abū Rayhān al-Bīrūnī states that "there is no observable
Ismaël Boulliau, pronounced. He was an active member of the Republic of an intellectual community that exchanged ideas. An early defender of the ideas of Copernicus and Galileo, Ismael Bullialdus has been called "the most noted astronomer of his generation". One of his books is Astronomia Philolaica. Ismael Bullialdus was the second-born to his two Calvinist parents, Susanna Motet and Ismael Bullialdus, his father was a notary by profession and an amateur astronomer who made observations in Loudun, France. His older brother was named after their father Ismael, but died shortly after birth. At the age of 21, Bullialdus converted to Roman Catholicism and was ordained at age 26. One year in 1632, he moved to Paris. Enjoying the patronage of the de Thou family, Bullialdus worked for 30 years in Paris as a librarian associated with the brothers Jacques and Pierre Dupuy, who were working on the Bibliothèque du Roi, France's first royal library. After the death of his employers, the brothers Dupuy, Bullialdus became secretary to the French ambassador of Holland.
After a dispute with him in 1666, however, he once again moved, this time to the Collège de Laon, where he worked again as a librarian. Bullialdus published his first work "De Natura Lucis" in 1638, which he followed with many more published works, ranging from books to published correspondence during his time involved with the Republic of Letters, he was one of the earliest members to be elected as a foreign associate into the Royal Society of London on April 4, 1667, only seven years after the Society was founded. He spent the last five years of his life as a priest, the same occupation in which he started his career, he retired to the Abbey St. Victor in Paris, where he died at the age of 89. Bullialdus was an active member of the Republic of Letters, the long-distance intellectual correspondence network that had emerged as an international community of self-proclaimed scholars and literary figures. Bullialdus was a prolific correspondent, with around 5,000 letters, his letters demonstrate the geographic reach of the Republic of Letters.
Around 4,200 of them are in the Collection Boulliau of the Bibliothèque nationale de France with another 800 to or from him that are outside the collection in 45 different archives in nearly a dozen countries. Many of his manuscripts are lost; the most famous of the known letters included in the original Archive Boulliau include correspondence with notable luminaries, including Galileo, Marin Mersenne, Henry Oldenburg, Christiaan Huygens, Fermat. In addition to his own letters, Bullialdus contributed to "The Archives of the Scientific Revolution". Among Bullialdus' papers were examinations of rare manuscripts. Found among his letters were copies of his contemporaries' manuscripts which he had preserved. Arguably most notable were the ten volumes of original autographs addressed to Nicolas-Claude Fabri de Peiresc. De natura lucis Philolaus Expositio rerum mathematicarum ad legendum Platonem utilium, translation of Theon of Smyrna Astronomia philolaica e-rara.ch De lineis spiralibus Opus novum ad arithmeticam infinitorum Ad astronomos monita duo Ismael Bullialdus' most famous work is Astronomia Philolaica.
Published in 1645, the book is considered by some modern-day historians of science to be the most important book in astronomy between Kepler and Newton. The book widened the awareness of Kepler's planetary ellipses, whereas Kepler used a physical cause to explain planetary motion, called on math and science to support his theory, Bullialdus offered an new cosmology, the "Conical Hypothesis". Bullialdus' Philolaic Astronomy consists of 14 main assumptions: Planets have a simple motion in a simple line. Planetary revolutions are equal, uniform, they should be regular revolutions or composed of regular revolutions. They can only be circular. Or composed of circles. Motions should have a principle of equality. Since they admit of a certain inequality, the center of the zodiac must be the reference point of inequality; this point is in the sun. Half of the inequality is attributed to eccentricity, the other to another cause which makes the planet slower at aphelion, less slow at perihelion, without disturbing the equality of motion or transposing it to some other place, whether the circle or the surface.
When the planet, moving from aphelion, comes to quadrature on the same surface, with equal motion, it should differ from the apparent motion of the first inequality or nearly so. Since the equal motion in the first quadrant is greater than the apparent motion, that part of apparent motion must be greater, hence from the first quadrant to perihelion the arc described going to perihelion must be larger than the first. All revolution is composed of circular parts. Equal motion is uniform; this equal motion does not correspond to a single circle, but to several unequal circles to which the apparent motion als
J. Robert Oppenheimer
Julius Robert Oppenheimer was an American theoretical physicist and professor of physics at the University of California, Berkeley. Oppenheimer was the wartime head of the Los Alamos Laboratory and is among those who are credited with being the "father of the atomic bomb" for their role in the Manhattan Project, the World War II undertaking that developed the first nuclear weapons; the first atomic bomb was detonated on July 16, 1945, in the Trinity test in New Mexico. Oppenheimer remarked that it brought to mind words from the Bhagavad Gita: "Now I am become Death, the destroyer of worlds." In August 1945, the weapons were used in the atomic bombings of Hiroshima and Nagasaki, which resulted in Japan's unconditional surrender. After the war ended, Oppenheimer became chairman of the influential General Advisory Committee of the newly created United States Atomic Energy Commission, he used that position to lobby for international control of nuclear power to avert nuclear proliferation and a nuclear arms race with the Soviet Union.
After provoking the ire of many politicians with his outspoken opinions during the Second Red Scare, he suffered the revocation of his security clearance in a much-publicized hearing in 1954, was stripped of his direct political influence. Nine years President John F. Kennedy awarded him with the Enrico Fermi Award as a gesture of political rehabilitation. Oppenheimer's achievements in physics included the Born–Oppenheimer approximation for molecular wave functions, work on the theory of electrons and positrons, the Oppenheimer–Phillips process in nuclear fusion, the first prediction of quantum tunneling. With his students he made important contributions to the modern theory of neutron stars and black holes, as well as to quantum mechanics, quantum field theory, the interactions of cosmic rays; as a teacher and promoter of science, he is remembered as a founding father of the American school of theoretical physics that gained world prominence in the 1930s. After World War II, he became director of the Institute for Advanced Study in New Jersey.
Oppenheimer was born in New York City on April 22, 1904, to Julius Oppenheimer, a wealthy Jewish textile importer who had immigrated to the United States from Germany in 1888, Ella Friedman, a painter. Julius came to America with no money, no baccalaureate studies, no knowledge of the English language, he within a decade was an executive with the company. Ella was from Baltimore; the Oppenheimers were non-observant Ashkenazi Jews. In 1912 the family moved to an apartment on the 11th floor of 155 Riverside Drive, near West 88th Street, Manhattan, an area known for luxurious mansions and townhouses, their art collection included works by Pablo Picasso and Édouard Vuillard, at least three original paintings by Vincent van Gogh. Robert had a younger brother, who became a physicist. Oppenheimer was educated at Alcuin Preparatory School, in 1911, he entered the Ethical Culture Society School; this had been founded by Felix Adler to promote a form of ethical training based on the Ethical Culture movement, whose motto was "Deed before Creed".
His father had been a member of the Society for many years, serving on its board of trustees from 1907 to 1915. Oppenheimer was a versatile scholar, interested in English and French literature, in mineralogy, he completed the third and fourth grades in one year, skipped half the eighth grade. During his final year, he became interested in chemistry, he entered Harvard College one year after graduation, at age 18, because he suffered an attack of colitis while prospecting in Joachimstal during a family summer vacation in Europe. To help him recover from the illness, his father enlisted the help of his English teacher Herbert Smith who took him to New Mexico, where Oppenheimer fell in love with horseback riding and the southwestern United States. Oppenheimer majored in chemistry, but Harvard required science students to study history and philosophy or mathematics, he compensated for his late start by taking six courses each term and was admitted to the undergraduate honor society Phi Beta Kappa.
In his first year, he was admitted to graduate standing in physics on the basis of independent study, which meant he was not required to take the basic classes and could enroll instead in advanced ones. He was attracted to experimental physics by a course on thermodynamics, taught by Percy Bridgman, he graduated summa cum laude in three years. In 1924, Oppenheimer was informed that he had been accepted into Cambridge, he wrote to Ernest Rutherford requesting permission to work at the Cavendish Laboratory. Bridgman provided Oppenheimer with a recommendation, which conceded that Oppenheimer's clumsiness in the laboratory made it apparent his forte was not experimental but rather theoretical physics. Rutherford was unimpressed, he was accepted by J. J. Thomson on condition that he complete a basic laboratory course, he developed an antagonistic relationship with his tutor, Patrick Blackett, only a few years his senior. While on vacation, as recalled by his friend Francis Fergusson, Oppenheimer once confessed that he had left an apple doused with noxious chemicals on Blackett's desk.
While Fergusson's account is the only detailed version of this event, Oppenheimer's parents were alerted by the university authorities who considered placing him on probation, a fate prevented by his parents lobbying the authorities. Oppenheimer was a tall, thin chain smoker, who neglected to eat d