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57-830: Ehrenfest is a surname. Notable people with the surname include: Paul Ehrenfest (1880-1933), Austrian physicist and mathematician Ehrenfest equations Ehrenfest model Ehrenfest paradox Ehrenfest theorem 32796 Ehrenfest Tatjana Ehrenfest-Afanassjewa (1876-1964), Ukrainian-Russian mathematician, wife of Paul Tanja van Aardenne-Ehrenfest (1905–1984), Austrian Dutch mathematician, daughter of Paul See also [ edit ] Ehrenfeld (disambiguation) Ehrenfels (disambiguation) Ehrenbaum Ehrenberg (disambiguation) Ehrenburg (disambiguation) Ehrenhaft Ehrenpreis Ehrenstein Ehrenthal [REDACTED] Surname list This page lists people with

114-543: A luminiferous aether . Conversely, Einstein was awarded the Nobel Prize for explaining the photoelectric effect , previously an experimental result lacking a theoretical formulation. A physical theory is a model of physical events. It is judged by the extent to which its predictions agree with empirical observations. The quality of a physical theory is also judged on its ability to make new predictions which can be verified by new observations. A physical theory differs from

171-504: A mathematical theorem in that while both are based on some form of axioms , judgment of mathematical applicability is not based on agreement with any experimental results. A physical theory similarly differs from a mathematical theory , in the sense that the word "theory" has a different meaning in mathematical terms. R i c = k g {\displaystyle \mathrm {Ric} =kg} The equations for an Einstein manifold , used in general relativity to describe

228-404: A certain economy and elegance (compare to mathematical beauty ), a notion sometimes called " Occam's razor " after the 13th-century English philosopher William of Occam (or Ockham), in which the simpler of two theories that describe the same matter just as adequately is preferred (but conceptual simplicity may mean mathematical complexity). They are also more likely to be accepted if they connect

285-500: A form of protoscience and others are a form of pseudoscience . The falsification of the original theory sometimes leads to reformulation of the theory. "Thought" experiments are situations created in one's mind, asking a question akin to "suppose you are in this situation, assuming such is true, what would follow?". They are usually created to investigate phenomena that are not readily experienced in every-day situations. Famous examples of such thought experiments are Schrödinger's cat ,

342-558: A mathematician; Galinka ('Galja') (1910–1979) became an author and illustrator of children's books; Paul, Jr. ('Pavlik') (1915–1939) became a physicist; and Vassily ('Wassik') (1918–1933). The Ehrenfests returned to Göttingen in September 1906. They did not see Boltzmann again: on 5 September Boltzmann took his own life in Duino near Trieste . Ehrenfest published an extensive obituary describing Boltzmann's accomplishments. Felix Klein , dean of

399-577: A member of the Royal Netherlands Academy of Arts and Sciences . Going by his correspondence with his friends, it seems that Ehrenfest suffered from severe depression at latest by May 1931. By August 1932, Einstein was so worried that he wrote to the Board of the University of Leiden, expressing concern and suggesting ways in which Ehrenfest's workload could be reduced. Having made arrangements for

456-493: A new branch of mathematics: infinite, orthogonal series . Modern theoretical physics attempts to unify theories and explain phenomena in further attempts to understand the Universe , from the cosmological to the elementary particle scale. Where experimentation cannot be done, theoretical physics still tries to advance through the use of mathematical models. Mainstream theories (sometimes referred to as central theories ) are

513-465: A physical system might be modeled; e.g., the notion, due to Riemann and others, that space itself might be curved. Theoretical problems that need computational investigation are often the concern of computational physics . Theoretical advances may consist in setting aside old, incorrect paradigms (e.g., aether theory of light propagation, caloric theory of heat, burning consisting of evolving phlogiston , or astronomical bodies revolving around

570-416: A professorship and therefore had no prospect of securing a permanent position. In 1912, Ehrenfest toured German -speaking universities in the hope of a position. He visited Berlin, where he saw Max Planck ; Leipzig , where he met his old friend German mathematician Gustav Herglotz ; Munich , where he met theoretical physicist Arnold Sommerfeld ; Zürich ; and Vienna. In Prague he met Albert Einstein for

627-672: A short visit to Leiden , Netherlands. He wrote his dissertation on Die Bewegung starrer Körper in Flüssigkeiten und die Mechanik von Hertz ( The Motion of Rigid Bodies in Fluids and the Mechanics of Hertz ) and obtained his Ph.D. on 23 June 1904 in Vienna, where he stayed from 1904 to 1905. On 21 December 1904, he married Afanasyeva, who collaborated with him in his work. They had two daughters and two sons: Tatyana ('Tanja') (1905–1984) also became

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684-469: A style all its own: a sharp logical analysis of the fundamental hypotheses, clear delineation of unsolved questions, and an explanation of general principles by cleverly chosen transparent examples. In 1907, the couple relocated to St. Petersburg. Ehrenfest found good friends there, in particular the physicist A.F. Joffe , but felt scientifically isolated. Moreover, because he was unwilling to declare belief in any religious denomination, he could not apply for

741-463: A wide range of phenomena. Testing the consequences of a theory is part of the scientific method . Physical theories can be grouped into three categories: mainstream theories , proposed theories and fringe theories . Theoretical physics began at least 2,300 years ago, under the Pre-socratic philosophy , and continued by Plato and Aristotle , whose views held sway for a millennium. During

798-514: Is best illustrated by what he wrote to Robert Oppenheimer in the summer of 1928, after Oppenheimer invited himself for an extended stay in Leiden: If you intend to mount heavy mathematical artillery again during your coming year in Europe, I would ask you not only not to come to Leiden, but if possible not even to Holland, and just because I am really so fond of you and want to keep it that way. But if, on

855-674: Is different from Wikidata All set index articles Paul Ehrenfest Paul Ehrenfest was born on 18 January 1880 in Vienna to Jewish parents, who were originally from Loštice in Moravia (now part of the Czech Republic ). His parents, Sigmund Ehrenfest and Johanna Jellinek, managed a grocery store. Although the family was not overly religious, Paul studied Hebrew and Jewish history . Later, he always emphasized his Jewish ancestry. Ehrenfest excelled in grade school but did not do well at

912-425: Is the crucial point) Das ist wo der Frosch ins Wasser springt (That is where the frog jumps into the water) Das ist der Patentanspruch (That is the patent claim, the essence) Da hat Herr ... schliesslich die Ratte aus der Suppe gezogen (There Mr. X finally pulled the rat out of the soup) [ when a scientist had solved a messy problem] Je besser man's versteht um so besser steht es dort (The better one understands,

969-415: Is the theory of adiabatic invariants . It is a concept derived from classical mechanics that can serve to refine certain methods of Niels Bohr's model of the atom (although initially Ehrenfest did not accept Bohr 's ideas), and also creates an association between atomic mechanics and statistical mechanics. He made major contributions to quantum physics , including the theory of phase transitions and

1026-840: The Akademisches Gymnasium , his best subject being mathematics . After transferring to the Franz Josef Gymnasium , his marks improved. In 1899, he passed the final exams . He majored in chemistry at the Vienna Institute of Technology , but took courses at the University of Vienna , in particular from Ludwig Boltzmann on his kinetic theory of thermodynamics . These lectures had a profound influence: they were instrumental in developing Ehrenfest's interest in theoretical physics , defined his main area of research for years to come, and provided an example of inspired teaching. At

1083-532: The EPR thought experiment , simple illustrations of time dilation , and so on. These usually lead to real experiments designed to verify that the conclusion (and therefore the assumptions) of the thought experiments are correct. The EPR thought experiment led to the Bell inequalities , which were then tested to various degrees of rigor , leading to the acceptance of the current formulation of quantum mechanics and probabilism as

1140-518: The Ehrenfest theorem , which states that expectation values of a quantum system conform to classical mechanics. His name is also given to the Ehrenfest paradox , an apparent paradox of relativity still discussed, to the Ehrenfest model , and to Ehrenfest time , the time characterizing the difference of quantum dynamics for observables from classical dynamics. Ehrenfest was also interested in developing mathematical theories for economics. This interest

1197-557: The Scientific Revolution gathered pace, the concepts of matter , energy, space, time and causality slowly began to acquire the form we know today, and other sciences spun off from the rubric of natural philosophy . Thus began the modern era of theory with the Copernican paradigm shift in astronomy, soon followed by Johannes Kepler 's expressions for planetary orbits, which summarized the meticulous observations of Tycho Brahe ;

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1254-603: The quantum mechanical idea that ( action and) energy are not continuously variable. Theoretical physics consists of several different approaches. In this regard, theoretical particle physics forms a good example. For instance: " phenomenologists " might employ ( semi- ) empirical formulas and heuristics to agree with experimental results, often without deep physical understanding . "Modelers" (also called "model-builders") often appear much like phenomenologists, but try to model speculative theories that have certain desirable features (rather than on experimental data), or apply

1311-446: The surname Ehrenfest . If an internal link intending to refer to a specific person led you to this page, you may wish to change that link by adding the person's given name (s) to the link. Retrieved from " https://en.wikipedia.org/w/index.php?title=Ehrenfest&oldid=952332519 " Categories : Surnames German-language surnames Hidden categories: Articles with short description Short description

1368-457: The two-fluid theory of electricity are two cases in this point. However, an exception to all the above is the wave–particle duality , a theory combining aspects of different, opposing models via the Bohr complementarity principle . Physical theories become accepted if they are able to make correct predictions and no (or few) incorrect ones. The theory should have, at least as a secondary objective,

1425-429: The 19th century. Another important event in the 19th century was the discovery of electromagnetic theory , unifying the previously separate phenomena of electricity, magnetism and light. The pillars of modern physics , and perhaps the most revolutionary theories in the history of physics, have been relativity theory and quantum mechanics . Newtonian mechanics was subsumed under special relativity and Newton's gravity

1482-469: The Dutchmen Snell and Huygens. In the 18th and 19th centuries Joseph-Louis Lagrange , Leonhard Euler and William Rowan Hamilton would extend the theory of classical mechanics considerably. They picked up the interactive intertwining of mathematics and physics begun two millennia earlier by Pythagoras. Among the great conceptual achievements of the 19th and 20th centuries were the consolidation of

1539-579: The Earth ) or may be an alternative model that provides answers that are more accurate or that can be more widely applied. In the latter case, a correspondence principle will be required to recover the previously known result . Sometimes though, advances may proceed along different paths. For example, an essentially correct theory may need some conceptual or factual revisions; atomic theory , first postulated millennia ago (by several thinkers in Greece and India ) and

1596-534: The Göttingen mathematicians and chief editor of the Enzyklopädie der mathematischen Wissenschaften ("Encyclopedia of Mathematical Sciences"), had counted on Boltzmann for a review about statistical mechanics. Now he asked Ehrenfest to take on this task. Together with his wife, Ehrenfest worked on it for several years; the article was not published until 1911. It is a review of the work of Boltzmann and his school, and has

1653-534: The annual Paul Ehrenfest Best Paper Award for Quantum Foundations . The Dutch Physics Council sponsors the annual Ehrenfest-Afanassjewa thesis award . Theoretical physics Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict natural phenomena . This is in contrast to experimental physics , which uses experimental tools to probe these phenomena. The advancement of science generally depends on

1710-419: The applications of relativity to problems in astronomy and cosmology respectively . All of these achievements depended on the theoretical physics as a moving force both to suggest experiments and to consolidate results — often by ingenious application of existing mathematics, or, as in the case of Descartes and Newton (with Leibniz ), by inventing new mathematics. Fourier's studies of heat conduction led to

1767-434: The better it is written there, [Ehrenfest's comment when Dirac was asked in writing for an explanation of his work, and Dirac characteristically simply reproduced exactly his previous explanation.] The monthly evening colloquium in physics at Leiden University Ehrenfest initiated in 1912 at his house continues with the name Colloquium Ehrenfestii . The Austrian Institute for Quantum Optics and Quantum Information sponsors

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1824-514: The body of knowledge of both factual and scientific views and possess a usual scientific quality of the tests of repeatability, consistency with existing well-established science and experimentation. There do exist mainstream theories that are generally accepted theories based solely upon their effects explaining a wide variety of data, although the detection, explanation, and possible composition are subjects of debate. The proposed theories of physics are usually relatively new theories which deal with

1881-467: The care of his other children, on 25 September 1933, in Amsterdam , Ehrenfest fatally shot his younger son Wassik, who had Down syndrome , then killed himself. Most of Ehrenfest's scientific papers deal primarily with fundamentals, and seek to clarify single sub-topics. His publications are renowned for their lucidity and directness, and for solving paradoxes by providing clearer descriptions. His method

1938-643: The concept of electron spin , Jan Tinbergen , Arend Rutgers , Hendrik Casimir , Gerhard Dieke , Dirk Struik , and Gerard Kuiper . His assistants included Yuri Krutkov , Viktor Trkal , Adriaan Fokker , Paul Epstein , and Gregory Breit . Other young foreign scientists who spent extended periods in his laboratory included Gunnar Nordström , Enrico Fermi , Igor Tamm , Oskar Klein , J. Robert Oppenheimer , Walter Elsasser , Ralph Kronig , Werner Heisenberg , Paul Dirac , and David Dennison . Ehrenfest had ambivalent opinions about science, technological progress, and cultural and social issues. In 1919, he became

1995-538: The confidence and sympathy you have shown me, I find myself so utterly incapable of finding words for it. On his invitation Einstein accepted in 1920 an appointment as extraordinary professor at the University of Leiden. This arrangement allowed Einstein to visit Leiden for a few weeks every year. At these occasions Einstein would stay at Ehrenfest's home. In 1923 Einstein stayed there for six weeks, after German ultra-nationalists in Berlin had made threats against his life. On

2052-483: The contrary, you want to spend at least your first few months patiently, comfortably, and joyfully in discussions that keep coming back to the same few points, chatting about a few basic questions with me and our young people—and without thinking much about publishing (!!!)—why then I welcome you with open arms!! Characteristically, he did not like the abstraction of the new quantum theory of Heisenberg and Dirac. Ehrenfest's most important contribution from 1912 to 1933

2109-400: The country and abroad, and invited them to visit Leiden and give presentations in his lecture series. Ehrenfest was an outstanding debater, quick to point out weaknesses and summarize the essentials. In his lectures, Ehrenfest emphasized simple models and examples to illustrate and clarify basic assumptions. His classes were small, and he made an effort to get to know students who made use of

2166-441: The curvature of spacetime A physical theory involves one or more relationships between various measurable quantities. Archimedes realized that a ship floats by displacing its mass of water, Pythagoras understood the relation between the length of a vibrating string and the musical tone it produces. Other examples include entropy as a measure of the uncertainty regarding the positions and motions of unseen particles and

2223-536: The first time, and they remained close friends thereafter. Einstein recommended that Ehrenfest succeed him in his position in Prague, but the plan failed since Ehrenfest declared himself an atheist. Sommerfeld offered him a position in Munich, but Ehrenfest received a better offer; at the same time there was an unexpected turn of events: H. A. Lorentz resigned his position at the University of Leiden , and on his advice, Ehrenfest

2280-416: The highest order, writing Principia Mathematica . In it contained a grand synthesis of the work of Copernicus, Galileo and Kepler; as well as Newton's theories of mechanics and gravitation, which held sway as worldviews until the early 20th century. Simultaneously, progress was also made in optics (in particular colour theory and the ancient science of geometrical optics ), courtesy of Newton, Descartes and

2337-455: The idea of energy (as well as its global conservation) by the inclusion of heat , electricity and magnetism , and then light . The laws of thermodynamics , and most importantly the introduction of the singular concept of entropy began to provide a macroscopic explanation for the properties of matter. Statistical mechanics (followed by statistical physics and Quantum statistical mechanics ) emerged as an offshoot of thermodynamics late in

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2394-565: The interplay between experimental studies and theory . In some cases, theoretical physics adheres to standards of mathematical rigour while giving little weight to experiments and observations. For example, while developing special relativity , Albert Einstein was concerned with the Lorentz transformation which left Maxwell's equations invariant, but was apparently uninterested in the Michelson–Morley experiment on Earth 's drift through

2451-667: The late 1920s. In the aftermath of World War 2, more progress brought much renewed interest in QFT, which had since the early efforts, stagnated. The same period also saw fresh attacks on the problems of superconductivity and phase transitions, as well as the first applications of QFT in the area of theoretical condensed matter. The 1960s and 70s saw the formulation of the Standard model of particle physics using QFT and progress in condensed matter physics (theoretical foundations of superconductivity and critical phenomena , among others ), in parallel to

2508-492: The occasion of the 50th anniversary of Lorentz' doctorate (December 1925) Ehrenfest invited both Bohr and Einstein over to Leiden, in an attempt to reconcile their scientific differences about the emerging quantum theory. These discussions were continued at the 1927 Solvay Conference , where Ehrenfest much to his dismay preferred Bohr's argument in this great debate. Ehrenfest used colourful German language in his physics lectures: Das ist der springende Punkt (translation: That

2565-419: The process of becoming established and some proposed theories. It can include speculative sciences. This includes physics fields and physical theories presented in accordance with known evidence, and a body of associated predictions have been made according to that theory. Some fringe theories go on to become a widely accepted part of physics. Other fringe theories end up being disproven. Some fringe theories are

2622-487: The reading room. Though few of them were accepted as majors in theoretical physics, he had long discussions with them almost daily. According to Einstein: He was not merely the best teacher in our profession whom I have ever known; he was also passionately preoccupied with the development and destiny of men, especially his students. To understand others, to gain their friendship and trust, to aid anyone embroiled in outer or inner struggles, to encourage youthful talent—all this

2679-590: The rise of medieval universities , the only acknowledged intellectual disciplines were the seven liberal arts of the Trivium like grammar , logic , and rhetoric and of the Quadrivium like arithmetic , geometry , music and astronomy . During the Middle Ages and Renaissance , the concept of experimental science, the counterpoint to theory, began with scholars such as Ibn al-Haytham and Francis Bacon . As

2736-484: The study of physics which include scientific approaches, means for determining the validity of models and new types of reasoning used to arrive at the theory. However, some proposed theories include theories that have been around for decades and have eluded methods of discovery and testing. Proposed theories can include fringe theories in the process of becoming established (and, sometimes, gaining wider acceptance). Proposed theories usually have not been tested. In addition to

2793-443: The techniques of mathematical modeling to physics problems. Some attempt to create approximate theories, called effective theories , because fully developed theories may be regarded as unsolvable or too complicated . Other theorists may try to unify , formalise, reinterpret or generalise extant theories, or create completely new ones altogether. Sometimes the vision provided by pure mathematical systems can provide clues to how

2850-472: The theories like those listed below, there are also different interpretations of quantum mechanics , which may or may not be considered different theories since it is debatable whether they yield different predictions for physical experiments, even in principle. For example, AdS/CFT correspondence , Chern–Simons theory , graviton , magnetic monopole , string theory , theory of everything . Fringe theories include any new area of scientific endeavor in

2907-695: The time, it was customary in the German-speaking world to study at more than one university, and in 1901, Ehrenfest transferred to University of Göttingen, which until 1933 was an important site for mathematics and theoretical physics. There he met his future wife, Tatyana Afanasyeva , a young mathematician born in Kiev (then the capital of the Kiev Governorate , Russian Empire ) and educated in St Petersburg . In 1903, he met Dutch physicist Hendrik Lorentz during

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2964-521: The works of these men (alongside Galileo's) can perhaps be considered to constitute the Scientific Revolution. The great push toward the modern concept of explanation started with Galileo , one of the few physicists who was both a consummate theoretician and a great experimentalist . The analytic geometry and mechanics of Descartes were incorporated into the calculus and mechanics of Isaac Newton , another theoretician/experimentalist of

3021-548: Was appointed as his successor. In October 1912, Ehrenfest arrived in Leiden, and on 4 December, he gave his inaugural lecture, Zur Krise der Lichtaether-Hypothese (About the crisis of the light-ether hypothesis). He remained in Leiden for the rest of his career. To stimulate interaction and exchange among physics students, Ehrenfest organized a discussion group and a study association called De Leidsche Flesch ("The Leyden jar "). He maintained close contact with prominent physicists in

3078-422: Was given a kinematic explanation by general relativity . Quantum mechanics led to an understanding of blackbody radiation (which indeed, was an original motivation for the theory) and of anomalies in the specific heats of solids — and finally to an understanding of the internal structures of atoms and molecules . Quantum mechanics soon gave way to the formulation of quantum field theory (QFT), begun in

3135-431: Was his real element, almost more than his immersion in scientific problems. If Ehrenfest felt there was little more he could teach a student, he would send them to other centers in Europe for more training. He would also encourage students to accept positions abroad. Among his students were Johannes Burgers , Hendrik Kramers , Dirk Coster , George Uhlenbeck and Samuel Goudsmit , who became famous for jointly proposing

3192-480: Was particularly close to both Einstein and Bohr. After Niels Bohr's first visit to Leiden in 1919, for Hans Kramers ' thesis defense, he wrote to Ehrenfest: I am sitting and thinking of all what you have told me about so very many different things, and whatever I think of I feel that I have learned so much from you which will be of great importance for me; but, at the same time, I wish so much to express my feeling of happiness over your friendship and of thankfulness for

3249-482: Was stimulated by his notion that there should be an analogy between thermodynamics and economic processes. While this did not result in publications, he did encourage his graduate student Jan Tinbergen to research this. Tinbergen's thesis was devoted to problems from both physics and economics, and he later became an economist and was awarded the first Nobel Memorial Prize in Economic Sciences in 1969. Ehrenfest

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