Niels Henrik David Bohr was a Danish physicist who made foundational contributions to understanding atomic structure and quantum theory, for which he received the Nobel Prize in Physics in 1922. Bohr was a philosopher and a promoter of scientific research. Bohr developed the Bohr model of the atom, in which he proposed that energy levels of electrons are discrete and that the electrons revolve in stable orbits around the atomic nucleus but can jump from one energy level to another. Although the Bohr model has been supplanted by other models, its underlying principles remain valid, he conceived the principle of complementarity: that items could be separately analysed in terms of contradictory properties, like behaving as a wave or a stream of particles. The notion of complementarity dominated Bohr's thinking in both philosophy. Bohr founded the Institute of Theoretical Physics at the University of Copenhagen, now known as the Niels Bohr Institute, which opened in 1920. Bohr mentored and collaborated with physicists including Hans Kramers, Oskar Klein, George de Hevesy, Werner Heisenberg.
He predicted the existence of a new zirconium-like element, named hafnium, after the Latin name for Copenhagen, where it was discovered. The element bohrium was named after him. During the 1930s, Bohr helped refugees from Nazism. After Denmark was occupied by the Germans, he had a famous meeting with Heisenberg, who had become the head of the German nuclear weapon project. In September 1943, word reached Bohr that he was about to be arrested by the Germans, he fled to Sweden. From there, he was flown to Britain, where he joined the British Tube Alloys nuclear weapons project, was part of the British mission to the Manhattan Project. After the war, Bohr called for international cooperation on nuclear energy, he was involved with the establishment of CERN and the Research Establishment Risø of the Danish Atomic Energy Commission and became the first chairman of the Nordic Institute for Theoretical Physics in 1957. Bohr was born in Copenhagen, Denmark, on 7 October 1885, the second of three children of Christian Bohr, a professor of physiology at the University of Copenhagen, Ellen Adler Bohr, who came from a wealthy Danish Jewish family prominent in banking and parliamentary circles.
He had an elder sister, a younger brother Harald. Jenny became a teacher, while Harald became a mathematician and Olympic footballer who played for the Danish national team at the 1908 Summer Olympics in London. Bohr was a passionate footballer as well, the two brothers played several matches for the Copenhagen-based Akademisk Boldklub, with Bohr as goalkeeper. Bohr was educated at Gammelholm Latin School. In 1903, Bohr enrolled as an undergraduate at Copenhagen University, his major was physics, which he studied under Professor Christian Christiansen, the university's only professor of physics at that time. He studied astronomy and mathematics under Professor Thorvald Thiele, philosophy under Professor Harald Høffding, a friend of his father. In 1905, a gold medal competition was sponsored by the Royal Danish Academy of Sciences and Letters to investigate a method for measuring the surface tension of liquids, proposed by Lord Rayleigh in 1879; this involved measuring the frequency of oscillation of the radius of a water jet.
Bohr conducted a series of experiments using his father's laboratory in the university. To complete his experiments, he had to make his own glassware, creating test tubes with the required elliptical cross-sections, he went beyond the original task, incorporating improvements into both Rayleigh's theory and his method, by taking into account the viscosity of the water, by working with finite amplitudes instead of just infinitesimal ones. His essay, which he submitted at the last minute, won the prize, he submitted an improved version of the paper to the Royal Society in London for publication in the Philosophical Transactions of the Royal Society. Harald became the first of the two Bohr brothers to earn a master's degree, which he earned for mathematics in April 1909. Niels took another nine months to earn his. Students had to submit a thesis on a subject assigned by their supervisor. Bohr's supervisor was Christiansen, the topic he chose was the electron theory of metals. Bohr subsequently elaborated his master's thesis into his much-larger Doctor of Philosophy thesis.
He surveyed the literature on the subject, settling on a model postulated by Paul Drude and elaborated by Hendrik Lorentz, in which the electrons in a metal are considered to behave like a gas. Bohr extended Lorentz's model, but was still unable to account for phenomena like the Hall effect, concluded that electron theory could not explain the magnetic properties of metals; the thesis was accepted in April 1911, Bohr conducted his formal defence on 13 May. Harald had received his doctorate the previous year. Bohr's thesis was groundbreaking, but attracted little interest outside Scandinavia because it was written in Danish, a Copenhagen University requirement at the time. In 1921, the Dutch physicist Hendrika Johanna van Leeuwen would independently derive a theorem from Bohr's thesis, today known as the Bohr–van Leeuwen theorem. In 1910, Bohr met the sister of the mathematician Niels Erik Nørlund. Bohr resigned his membership in the Church of Denmark on 16 April 1912, he and Margrethe were married in a civil ceremony at the town hall in Slagelse on 1 August.
Years his brother Harald left the church before getting married. Bohr and Margrethe had six sons; the oldest, died in a boating acciden
In physics, a force is said to do work if, when acting, there is a displacement of the point of application in the direction of the force. For example, when a ball is held above the ground and dropped, the work done on the ball as it falls is equal to the weight of the ball multiplied by the distance to the ground; when the force is constant and the angle between the force and the displacement is θ the work done is given by W = Fs cos θ. Work transfers energy from one form to another. According to Jammer, the term work was introduced in 1826 by the French mathematician Gaspard-Gustave Coriolis as "weight lifted through a height", based on the use of early steam engines to lift buckets of water out of flooded ore mines. According to Rene Dugas, French engineer and historian, it is to Solomon of Caux "that we owe the term work in the sense that it is used in mechanics now"; the SI unit of work is the joule. The SI unit of work is the joule, defined as the work expended by a force of one newton through a displacement of one metre.
The dimensionally equivalent newton-metre is sometimes used as the measuring unit for work, but this can be confused with the unit newton-metre, the measurement unit of torque. Usage of N⋅m is discouraged by the SI authority, since it can lead to confusion as to whether the quantity expressed in newton metres is a torque measurement, or a measurement of work. Non-SI units of work include the newton-metre, the foot-pound, the foot-poundal, the kilowatt hour, the litre-atmosphere, the horsepower-hour. Due to work having the same physical dimension as heat measurement units reserved for heat or energy content, such as therm, BTU and Calorie, are utilized as a measuring unit; the work W done by a constant force of magnitude F on a point that moves a displacement s in a straight line in the direction of the force is the product W = F s. For example, if a force of 10 newtons acts along a point that travels 2 metres W = F s = = 20 J; this is the work done lifting a 1 kg object from ground level to over a person's head against the force of gravity.
The work is doubled either by lifting twice the weight the same distance or by lifting the same weight twice the distance. Work is related to energy; the work-energy principle states that an increase in the kinetic energy of a rigid body is caused by an equal amount of positive work done on the body by the resultant force acting on that body. Conversely, a decrease in kinetic energy is caused by an equal amount of negative work done by the resultant force. From Newton's second law, it can be shown that work on a free, rigid body, is equal to the change in kinetic energy K E of the linear velocity and angular velocity of that body, W = Δ K E; the work of forces generated by a potential function is known as potential energy and the forces are said to be conservative. Therefore, work on an object, displaced in a conservative force field, without change in velocity or rotation, is equal to minus the change of potential energy P E of the object, W = − Δ P E; these formulas show that work is the energy associated with the action of a force, so work subsequently possesses the physical dimensions, units, of energy.
The work/energy principles discussed here are identical to Electric work/energy principles. Constraint forces limit the movement of components in a system, such as constraining an object to a surface. Constraint forces restrict the velocity in the direction of the constraint to zero, which means the constraint forces do not perform work on the system. For a mechanical system, constraint forces eliminate movement in directions that characterize the constraint, thus constraint forces do not perform work on the system, because the component of velocity along the constraint force at each point of application is zero. For example, in a pulley system like the Atwood machine, the internal forces on the rope and at the supporting pulley do no work on the system; therefore work need only be computed for the gravity forces acting on the bodies. For example, the centripetal force exerted inwards by a string on a ball in uniform circular motion sideways constrains the ball to circular motion restricting its movement away from the center of the circle.
This force does zero work. Another example is a book on a table. If external forces are applied to the book so that it slides on the table the force exerted by the table constrains the book from moving downwards; the force exerted by the table supports the book and is perpendicular to its movement which means that this constraint force does not perform work. The magnetic force on a charged particle is F = qv × B, where q is the charge, v is the velocity of the particle, B is the mag
Max Karl Ernst Ludwig Planck, ForMemRS was a German theoretical physicist whose discovery of energy quanta won him the Nobel Prize in Physics in 1918. Planck made many contributions to theoretical physics, but his fame as a physicist rests on his role as the originator of quantum theory, which revolutionized human understanding of atomic and subatomic processes. In 1948, the German scientific institution the Kaiser Wilhelm Society was renamed the Max Planck Society; the MPS now includes 83 institutions representing a wide range of scientific directions. Planck came from a intellectual family, his paternal great-grandfather and grandfather were both theology professors in Göttingen. One of his uncles was a judge. Planck was born in Holstein, to Johann Julius Wilhelm Planck and his second wife, Emma Patzig, he was baptized with the name of Karl Ernst Ludwig Marx Planck. However, by the age of ten he used this for the rest of his life, he was the 6th child in the family, though two of his siblings were from his father's first marriage.
War was common during Planck's early years and among his earliest memories was the marching of Prussian and Austrian troops into Kiel during the Second Schleswig War in 1864. In 1867 the family moved to Munich, Planck enrolled in the Maximilians gymnasium school, where he came under the tutelage of Hermann Müller, a mathematician who took an interest in the youth, taught him astronomy and mechanics as well as mathematics, it was from Müller. Planck graduated early, at age 17; this is. Planck was gifted, he took singing lessons and played piano and cello, composed songs and operas. However, instead of music he chose to study physics; the Munich physics professor Philipp von Jolly advised Planck against going into physics, saying, "in this field everything is discovered, all that remains is to fill a few holes." Planck replied that he did not wish to discover new things, but only to understand the known fundamentals of the field, so began his studies in 1874 at the University of Munich. Under Jolly's supervision, Planck performed the only experiments of his scientific career, studying the diffusion of hydrogen through heated platinum, but transferred to theoretical physics.
In 1877 he went to the Friedrich Wilhelms University in Berlin for a year of study with physicists Hermann von Helmholtz and Gustav Kirchhoff and mathematician Karl Weierstrass. He wrote that Helmholtz was never quite prepared, spoke miscalculated endlessly, bored his listeners, while Kirchhoff spoke in prepared lectures which were dry and monotonous, he soon became close friends with Helmholtz. While there he undertook a program of self-study of Clausius's writings, which led him to choose thermodynamics as his field. In October 1878 Planck passed his qualifying exams and in February 1879 defended his dissertation, Über den zweiten Hauptsatz der mechanischen Wärmetheorie, he taught mathematics and physics at his former school in Munich. By the year 1880, Planck obtained two highest academic degrees offered in Europe; the first was a doctorate degree after he completed his paper detailing his research and theory of thermodynamics. He presented his thesis called Gleichgewichtszustände isotroper Körper in verschiedenen Temperaturen, which earned him a habilitation.
With the completion of his habilitation thesis, Planck became an unpaid Privatdozent in Munich, waiting until he was offered an academic position. Although he was ignored by the academic community, he furthered his work on the field of heat theory and discovered one after another the same thermodynamical formalism as Gibbs without realizing it. Clausius's ideas on entropy occupied a central role in his work. In April 1885 the University of Kiel appointed Planck as associate professor of theoretical physics. Further work on entropy and its treatment as applied in physical chemistry, followed, he published his Treatise on Thermodynamics in 1897. He proposed a thermodynamic basis for Svante Arrhenius's theory of electrolytic dissociation. In 1889 he was named the successor to Kirchhoff's position at the Friedrich-Wilhelms-Universität in Berlin – thanks to Helmholtz's intercession – and by 1892 became a full professor. In 1907 Planck turned it down to stay in Berlin. During 1909, as a University of Berlin professor, he was invited to become the Ernest Kempton Adams Lecturer in Theoretical Physics at Columbia University in New York City.
A series of his lectures were translated and co-published by Columbia University professor A. P. Wills, he retired from Berlin on 10 January 1926, was succeeded by Erwin Schrödinger. In March 1887 Planck married Marie Merck, sister of a school fellow, moved with her into a sublet apartment in Kiel, they had four children: Karl, the twins Emma and Grete, Erwin. After the apartment in Berlin, the Planck family lived in a villa in Berlin-Grunewald, Wangenheimstrasse 21. Several other professors from University of Berlin lived nearby, among them theologian Ad
Randomness is the lack of pattern or predictability in events. A random sequence of events, symbols or steps has no order and does not follow an intelligible pattern or combination. Individual random events are by definition unpredictable, but in many cases the frequency of different outcomes over a large number of events is predictable. For example, when throwing two dice, the outcome of any particular roll is unpredictable, but a sum of 7 will occur twice as as 4. In this view, randomness is a measure of uncertainty of an outcome, rather than haphazardness, applies to concepts of chance and information entropy; the fields of mathematics and statistics use formal definitions of randomness. In statistics, a random variable is an assignment of a numerical value to each possible outcome of an event space; this association facilitates the calculation of probabilities of the events. Random variables can appear in random sequences. A random process is a sequence of random variables whose outcomes do not follow a deterministic pattern, but follow an evolution described by probability distributions.
These and other constructs are useful in probability theory and the various applications of randomness. Randomness is most used in statistics to signify well-defined statistical properties. Monte Carlo methods, which rely on random input, are important techniques in science, as, for instance, in computational science. By analogy, quasi-Monte Carlo methods use quasirandom number generators. Random selection, when narrowly associated with a simple random sample, is a method of selecting items from a population where the probability of choosing a specific item is the proportion of those items in the population. For example, with a bowl containing just 10 red marbles and 90 blue marbles, a random selection mechanism would choose a red marble with probability 1/10. Note that a random selection mechanism that selected 10 marbles from this bowl would not result in 1 red and 9 blue. In situations where a population consists of items that are distinguishable, a random selection mechanism requires equal probabilities for any item to be chosen.
That is, if the selection process is such that each member of a population, of say research subjects, has the same probability of being chosen we can say the selection process is random. In ancient history, the concepts of chance and randomness were intertwined with that of fate. Many ancient peoples threw dice to determine fate, this evolved into games of chance. Most ancient cultures used various methods of divination to attempt to circumvent randomness and fate; the Chinese of 3000 years ago were the earliest people to formalize odds and chance. The Greek philosophers discussed randomness at length, but only in non-quantitative forms, it was only in the 16th century that Italian mathematicians began to formalize the odds associated with various games of chance. The invention of the calculus had a positive impact on the formal study of randomness. In the 1888 edition of his book The Logic of Chance John Venn wrote a chapter on The conception of randomness that included his view of the randomness of the digits of the number pi by using them to construct a random walk in two dimensions.
The early part of the 20th century saw a rapid growth in the formal analysis of randomness, as various approaches to the mathematical foundations of probability were introduced. In the mid- to late-20th century, ideas of algorithmic information theory introduced new dimensions to the field via the concept of algorithmic randomness. Although randomness had been viewed as an obstacle and a nuisance for many centuries, in the 20th century computer scientists began to realize that the deliberate introduction of randomness into computations can be an effective tool for designing better algorithms. In some cases such randomized algorithms outperform the best deterministic methods. Many scientific fields are concerned with randomness: In the 19th century, scientists used the idea of random motions of molecules in the development of statistical mechanics to explain phenomena in thermodynamics and the properties of gases. According to several standard interpretations of quantum mechanics, microscopic phenomena are objectively random.
That is, in an experiment that controls all causally relevant parameters, some aspects of the outcome still vary randomly. For example, if a single unstable atom is placed in a controlled environment, it cannot be predicted how long it will take for the atom to decay—only the probability of decay in a given time. Thus, quantum mechanics does not specify the outcome of individual experiments but only the probabilities. Hidden variable theories reject the view that nature contains irreducible randomness: such theories posit that in the processes that appear random, properties with a certain statistical distribution are at work behind the scenes, determining the outcome in each case; the modern evolutionary synthesis ascribes the observed diversity of life to random genetic mutations followed by natural selection. The latter retains some random mutations in the gene pool due to the systematically improved chance for survival and reproduction that those mutated genes confer on individuals who possess them.
Several authors claim that evolution and sometimes development require a specific form of randomness, namely the introduction of qualitatively new behaviors. Instead of the choice of one possibility among several pre-given ones, this randomness corresponds to the formation of new possibilities; the characteristics of an organism arise to some extent deterministically and to som
Paul Adrien Maurice Dirac was an English theoretical physicist, regarded as one of the most significant physicists of the 20th century. Dirac made fundamental contributions to the early development of both quantum mechanics and quantum electrodynamics. Among other discoveries, he formulated the Dirac equation which describes the behaviour of fermions and predicted the existence of antimatter. Dirac shared the 1933 Nobel Prize in Physics with Erwin Schrödinger "for the discovery of new productive forms of atomic theory", he made significant contributions to the reconciliation of general relativity with quantum mechanics. Dirac was regarded by his colleagues as unusual in character. In a 1926 letter to Paul Ehrenfest, Albert Einstein wrote of Dirac, "This balancing on the dizzying path between genius and madness is awful", he was the Lucasian Professor of Mathematics at the University of Cambridge, a member of the Center for Theoretical Studies, University of Miami, spent the last decade of his life at Florida State University.
Paul Adrien Maurice Dirac was born at his parents' home in Bristol, England, on 8 August 1902, grew up in the Bishopston area of the city. His father, Charles Adrien Ladislas Dirac, was an immigrant from Saint-Maurice, who worked in Bristol as a French teacher, his mother, Florence Hannah Dirac, née Holten, the daughter of a ship's captain, was born in Cornwall and worked as a librarian at the Bristol Central Library. Paul had a younger sister, Béatrice Isabelle Marguerite, known as Betty, an older brother, Reginald Charles Félix, known as Felix, who committed suicide in March 1925. Dirac recalled: "My parents were distressed. I didn't know they cared so much I never knew that parents were supposed to care for their children, but from on I knew."Charles and the children were Swiss nationals until they became naturalised on 22 October 1919. Dirac's father was authoritarian, although he disapproved of corporal punishment. Dirac had a strained relationship with his father, so much so that after his father's death, Dirac wrote, "I feel much freer now, I am my own man."
Charles forced his children to speak to him only in French. When Dirac found that he could not express what he wanted to say in French, he chose to remain silent. Dirac was educated first at Bishop Road Primary School and at the all-boys Merchant Venturers' Technical College, where his father was a French teacher; the school was an institution attached to the University of Bristol. It emphasised technical subjects like bricklaying and metal work, modern languages; this was unusual at a time when secondary education in Britain was still dedicated to the classics, something for which Dirac would express his gratitude. Dirac studied electrical engineering on a City of Bristol University Scholarship at the University of Bristol's engineering faculty, co-located with the Merchant Venturers' Technical College. Shortly before he completed his degree in 1921, he sat the entrance examination for St John's College, Cambridge, he passed and was awarded a £70 scholarship, but this fell short of the amount of money required to live and study at Cambridge.
Despite his having graduated with a first class honours Bachelor of Science degree in engineering, the economic climate of the post-war depression was such that he was unable to find work as an engineer. Instead, he took up an offer to study for a Bachelor of Arts degree in mathematics at the University of Bristol free of charge, he was permitted to skip the first year of the course owing to his engineering degree. In 1923, Dirac graduated, once again with first class honours, received a £140 scholarship from the Department of Scientific and Industrial Research. Along with his £70 scholarship from St John's College, this was enough to live at Cambridge. There, Dirac pursued his interests in the theory of general relativity, an interest he had gained earlier as a student in Bristol, in the nascent field of quantum physics, under the supervision of Ralph Fowler. From 1925 to 1928 he held an 1851 Research Fellowship from the Royal Commission for the Exhibition of 1851, he completed his PhD in June 1926 with the first thesis on quantum mechanics to be submitted anywhere.
He continued his research in Copenhagen and Göttingen. Dirac married Margit Wigner, in 1937, he adopted Margit's two children and Gabriel. Paul and Margit Dirac had two children together, Mary Elizabeth and Florence Monica. Margit, known as Manci, visited her brother in 1934 in Princeton, New Jersey, from her native Hungary and, while at dinner at the Annex Restaurant met the "lonely-looking man at the next table." This account from a Korean physicist, Y. S. Kim, who met and was influenced by Dirac says: "It is quite fortunate for the physics community that Manci took good care of our respected Paul A. M. Dirac. Dirac published eleven papers during the period 1939–46.... Dirac was able to maintain his normal research productivity only because Manci was in charge of everything else." Dirac was known among his colleagues for his taciturn nature. His colleagues in Cambridge jokingly defined a unit called a "dirac", one word per hour; when Niels Bohr complained that he did not know how to finish a sentence in a scientific article he was writing, Dirac replied, "I was taught at school never to start a sentence without knowing the end of it."
He criticised the physicist J. Robert Oppenheimer's interest in poetry: "The aim of science is to make difficult things understandable in a simpler way.
In physics, string theory is a theoretical framework in which the point-like particles of particle physics are replaced by one-dimensional objects called strings. It describes how these strings propagate through interact with each other. On distance scales larger than the string scale, a string looks just like an ordinary particle, with its mass and other properties determined by the vibrational state of the string. In string theory, one of the many vibrational states of the string corresponds to the graviton, a quantum mechanical particle that carries gravitational force, thus string theory is a theory of quantum gravity. String theory is a broad and varied subject that attempts to address a number of deep questions of fundamental physics. String theory has been applied to a variety of problems in black hole physics, early universe cosmology, nuclear physics, condensed matter physics, it has stimulated a number of major developments in pure mathematics; because string theory provides a unified description of gravity and particle physics, it is a candidate for a theory of everything, a self-contained mathematical model that describes all fundamental forces and forms of matter.
Despite much work on these problems, it is not known to what extent string theory describes the real world or how much freedom the theory allows in the choice of its details. String theory was first studied in the late 1960s as a theory of the strong nuclear force, before being abandoned in favor of quantum chromodynamics. Subsequently, it was realized that the properties that made string theory unsuitable as a theory of nuclear physics made it a promising candidate for a quantum theory of gravity; the earliest version of string theory, bosonic string theory, incorporated only the class of particles known as bosons. It developed into superstring theory, which posits a connection called supersymmetry between bosons and the class of particles called fermions. Five consistent versions of superstring theory were developed before it was conjectured in the mid-1990s that they were all different limiting cases of a single theory in eleven dimensions known as M-theory. In late 1997, theorists discovered an important relationship called the AdS/CFT correspondence, which relates string theory to another type of physical theory called a quantum field theory.
One of the challenges of string theory is that the full theory does not have a satisfactory definition in all circumstances. Another issue is that the theory is thought to describe an enormous landscape of possible universes, this has complicated efforts to develop theories of particle physics based on string theory; these issues have led some in the community to criticize these approaches to physics and question the value of continued research on string theory unification. In the twentieth century, two theoretical frameworks emerged for formulating the laws of physics; the first is Albert Einstein's general theory of relativity, a theory that explains the force of gravity and the structure of space and time. The other is quantum mechanics, a different formulation to describe physical phenomena using the known probability principles. By the late 1970s, these two frameworks had proven to be sufficient to explain most of the observed features of the universe, from elementary particles to atoms to the evolution of stars and the universe as a whole.
In spite of these successes, there are still many problems. One of the deepest problems in modern physics is the problem of quantum gravity; the general theory of relativity is formulated within the framework of classical physics, whereas the other fundamental forces are described within the framework of quantum mechanics. A quantum theory of gravity is needed in order to reconcile general relativity with the principles of quantum mechanics, but difficulties arise when one attempts to apply the usual prescriptions of quantum theory to the force of gravity. In addition to the problem of developing a consistent theory of quantum gravity, there are many other fundamental problems in the physics of atomic nuclei, black holes, the early universe. String theory is a theoretical framework that attempts to address many others; the starting point for string theory is the idea that the point-like particles of particle physics can be modeled as one-dimensional objects called strings. String theory describes how strings propagate through interact with each other.
In a given version of string theory, there is only one kind of string, which may look like a small loop or segment of ordinary string, it can vibrate in different ways. On distance scales larger than the string scale, a string will look just like an ordinary particle, with its mass and other properties determined by the vibrational state of the string. In this way, all of the different elementary particles may be viewed as vibrating strings. In string theory, one of the vibrational states of the string gives rise to the graviton, a quantum mechanical particle that carries gravitational force, thus string theory is a theory of quantum gravity. One of the main developments of the past several decades in string theory was the discovery of certain "dualities", mathematical transformations that identify one physical theory with another. Physicists studying string theory have discovered a number of these dualities between different versions of string theory, this has led to the conjecture that all consistent versions of string theory are subsumed in a single framework known as M-theory.
Studies of string theory have yielded a number of results on the nature of black holes and the gravitational interaction. There are certain paradoxes that arise when one attempts to understand the quantum aspects of black holes, work on string theory
Wolfgang Ernst Pauli was an Austrian-born Swiss and American theoretical physicist and one of the pioneers of quantum physics. In 1945, after having been nominated by Albert Einstein, Pauli received the Nobel Prize in Physics for his "decisive contribution through his discovery of a new law of Nature, the exclusion principle or Pauli principle"; the discovery involved spin theory, the basis of a theory of the structure of matter. Pauli was born in Vienna to his wife Bertha Camilla Schütz. Pauli's middle name was given in honor of physicist Ernst Mach. Pauli's paternal grandparents were from prominent Jewish families of Prague. Pauli's father converted from Judaism to Roman Catholicism shortly before his marriage in 1899. Pauli's mother, Bertha Schütz, was raised in her own mother's Roman Catholic religion. Pauli was raised as a Roman Catholic, although he and his parents left the Church, he is considered to have been a mystic. Pauli attended the Döblinger-Gymnasium in Vienna, graduating with distinction in 1918.
Only two months after graduation, he published his first paper, on Albert Einstein's theory of general relativity. He attended the Ludwig-Maximilians University in Munich, working under Arnold Sommerfeld, where he received his PhD in July 1921 for his thesis on the quantum theory of ionized diatomic hydrogen. Sommerfeld asked Pauli to review the theory of relativity for the Encyklopädie der mathematischen Wissenschaften. Two months after receiving his doctorate, Pauli completed the article, it was praised by Einstein. Pauli spent a year at the University of Göttingen as the assistant to Max Born, the following year at the Institute for Theoretical Physics in Copenhagen, which became the Niels Bohr Institute in 1965. From 1923 to 1928, he was a lecturer at the University of Hamburg. During this period, Pauli was instrumental in the development of the modern theory of quantum mechanics. In particular, he formulated the theory of nonrelativistic spin. In 1928, he was appointed Professor of Theoretical Physics at ETH Zurich in Switzerland where he made significant scientific progress.
He held visiting professorships at the University of Michigan in 1931, the Institute for Advanced Study in Princeton in 1935. He was awarded the Lorentz Medal in 1931. At the end of 1930, shortly after his postulation of the neutrino and following his divorce and the suicide of his mother, Pauli experienced a personal crisis, he consulted psychotherapist Carl Jung who, like Pauli, lived near Zurich. Jung began interpreting Pauli's archetypal dreams, Pauli became one of the depth psychologist's best students, he soon began to criticize the epistemology of Jung's theory scientifically, this contributed to a certain clarification of the latter's thoughts about the concept of synchronicity. A great many of these discussions are documented in the Pauli/Jung letters, today published as Atom and Archetype. Jung's elaborate analysis of more than 400 of Pauli's dreams is documented in Psychology and Alchemy; the German annexation of Austria in 1938 made him a German citizen, which became a problem for him in 1939 after the outbreak of World War II.
In 1940, he tried in vain to obtain Swiss citizenship, which would have allowed him to remain at the ETH. Pauli moved to the United States in 1940, where he was employed as a professor of theoretical physics at the Institute for Advanced Study. In 1946, after the war, he became a naturalized citizen of the United States and subsequently returned to Zurich, where he remained for the rest of his life. In 1949, he was granted Swiss citizenship. In 1958, Pauli was awarded the Max Planck medal. In that same year, he fell ill with pancreatic cancer; when his last assistant, Charles Enz, visited him at the Rotkreuz hospital in Zurich, Pauli asked him: "Did you see the room number?" It was number 137. Throughout his life, Pauli had been preoccupied with the question of why the fine structure constant, a dimensionless fundamental constant, has a value nearly equal to 1/137. Pauli died in that room on 15 December 1958. Pauli made many important contributions as a physicist in the field of quantum mechanics.
He published papers, preferring lengthy correspondences with colleagues such as Niels Bohr and Werner Heisenberg, with whom he had close friendships. Many of his ideas and results were never published and appeared only in his letters, which were copied and circulated by their recipients. Pauli proposed in 1924 a new quantum degree of freedom with two possible values, in order to resolve inconsistencies between observed molecular spectra and the developing theory of quantum mechanics, he formulated the Pauli exclusion principle his most important work, which stated that no two electrons could exist in the same quantum state, identified by four quantum numbers including his new two-valued degree of freedom. The idea of spin originated with Ralph Kronig. George Uhlenbeck and Samuel Goudsmit one year identified Pauli's new degree of freedom as electron spin, a discovery in which Pauli for a long time wrongly refused to believe. In 1926, shortly after Heisenberg published the matrix theory of modern quantum mechanics, Pauli used it to derive the observed spectrum of the hydrogen atom.
This result was important in secu