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Encyclopedia > Theoretical physics

Theoretical physics employs mathematical models and abstractions of physics in an attempt to explain experimental data taken of the natural world. Its central core is mathematical physics 1, though other conceptual techniques are also used. The goal is to rationalize, explain and predict physical phenomena. The advancement of science depends in general on the interplay between experimental studies and theory. In some cases, theoretical physics adheres to standards of mathematical rigor 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 a luminiferous ether. On the other hand, Einstein was awarded the Nobel Prize for explaining the photoelectric effect, previously an experimental result lacking a theoretical formulation. A mathematical model is an abstract model that uses mathematical language to describe the behaviour of a system. ... abstraction in general. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... Mathematical physics is the scientific discipline concerned with the application of mathematics to problems in physics and the development of mathematical methods suitable for such applications and for the formulation of physical theories. ... For other uses, see Phenomena (disambiguation). ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... In the scientific method, an experiment (Latin: ex- periri, of (or from) trying) is a set of observations performed in the context of solving a particular problem or question, to retain or falsify a hypothesis or research concerning phenomena. ... The word theory has a number of distinct meanings in different fields of knowledge, depending on their methodologies and the context of discussion. ... Look up Rigour in Wiktionary, the free dictionary. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ... â€œEinsteinâ€ redirects here. ... In physics, the Lorentz transformation converts between two different observers measurements of space and time, where one observer is in constant motion with respect to the other. ... For thermodynamic relations, see Maxwell relations. ... The Michelson-Morley experiment, one of the most important and famous experiments in the history of physics, was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University, and is considered by some to be the first strong evidence against the theory of... This article is about Earth as a planet. ... The luminiferous aether: it was hypothesised that the Earth moves through a medium of aether that carries light In the late 19th century luminiferous aether (light-bearing aether) was the term used to describe a medium for the propagation of light. ... The Nobel Prize (Swedish: ) was established in Alfred Nobels will in 1895, and it was first awarded in Physics, Chemistry, Physiology or Medicine, Literature, and Peace in 1901. ... A diagram illustrating the emission of electrons from a metal plate, requiring energy gained from an incoming photon to be more than the work function of the material. ...

## Contents

A physical theory is a model of physical events and cannot be proven from basic axioms. A physical theory is different from a mathematical theorem; physical theories model reality and are a statement of what has been observed, and provide predictions of new observations. For the algebra software named Axiom, see Axiom computer algebra system. ... For other meanings of mathematics or uses of math and maths, see Mathematics (disambiguation) and Math (disambiguation). ... Look up theorem in Wiktionary, the free dictionary. ...

 “ $mathrm{Ric} = k,g$ An Einstein manifold, used in general relativity to describe the curvature of spacetime An Einstein manifold is a Riemannian manifold (M,g) whose Ricci tensor is proportional to the metric tensor: Taking a trace shows that k is equal to s/n, where n is the dimension of M and s is the scalar curvature. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... For other uses of this term, see Spacetime (disambiguation). ... ”

Therefore, more is involved than the application, or even invention, of mathematics — to wit: concept formation. Archimedes realized that one could determine the volume of an irregularly-shaped object by immersing it in a liquid, and 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, and how to calculate the length of a rectangle's diagonal. Other examples include entropy as a measure of the uncertainty regarding the positions and motions of unseen particles and the quantum mechanical idea that (action and) energy are not continuously variable. Sometimes it is the vision of mathematicians which provides the clue; e.g., the notion, due to Riemann and others, that space itself might be curved. For other uses, see Archimedes (disambiguation). ... For other uses, see Volume (disambiguation). ... For other uses, see Liquid (disambiguation). ... Pythagoras of Samos (Greek: ; between 580 and 572 BCâ€“between 500 and 490 BC) was an Ionian (Greek) philosopher and founder of the religious movement called Pythagoreanism. ... Oscillation is the variation, typically in time, of some measure about a central value (often a point of equilibrium) or between two or more different states. ... For other uses, see Music (disambiguation). ... A calculation is a deliberate process for transforming one or more inputs into one or more results. ... 2-dimensional renderings (ie. ... In geometry, a rectangle is defined as a quadrilateral where all four of its angles are right angles. ... For other uses, see: information entropy (in information theory) and entropy (disambiguation). ... This article or section is in need of attention from an expert on the subject. ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... In physics, the action is an integral quantity that is used to determine the evolution of a physical system between two defined states using the calculus of variations. ... In computer science and mathematics, a variable (pronounced ) (sometimes called an object or identifier in computer science) is a symbolic representation used to denote a quantity or expression. ... Leonhard Euler, considered one of the greatest mathematicians of all time A mathematician is a person whose primary area of study and research is the field of mathematics. ... Bernhard Riemann. ... This article is about the idea of space. ...

Theoretical advances often consist in setting aside old, incorrect paradigms often replacing them with new ones. For other uses, see Paradigm (disambiguation). ...

Physical theories can be grouped into three categories: mainstream theories, proposed theories and fringe theories. Theoretical physics employs mathematical models and abstractions of physics, as opposed to experimental processes, in an attempt to understand nature. ... Theoretical physics employs mathematical models and abstractions of physics, as opposed to experimental processes, in an attempt to understand nature. ... Theoretical physics employs mathematical models and abstractions of physics, as opposed to experimental processes, in an attempt to understand nature. ...

## History

For more details on this topic, see History of physics.

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 was incorporated into the calculus and mechanics of Isaac Newton, another theoretician/experimentalist of the highest order. Joseph-Louis Lagrange, Leonhard Euler and William Rowan Hamilton would extend the theory of classical mechanics considerably. Each of these individuals picked up the interactive intertwining of mathematics and physics begun two millennia earlier by Pythagoras. Galileo redirects here. ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ... A blanket term for all sorts of scientists engaged more in experimental activity than on the theoretical side of the various sciences. ... Analytic geometry, also called coordinate geometry and earlier referred to as Cartesian geometry or analytical geometry, is the study of geometry using the principles of algebra. ... Descartes redirects here. ... For other uses, see Calculus (disambiguation). ... Classical mechanics (commonly confused with Newtonian mechanics, which is a subfield thereof) is used for describing the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. ... Sir Isaac Newton FRS (4 January 1643 â€“ 31 March 1727) [ OS: 25 December 1642 â€“ 20 March 1727] was an English physicist, mathematician, astronomer, natural philosopher, and alchemist. ... Joseph Louis Lagrange (January 25, 1736 &#8211; April 10, 1813) was an Italian mathematician and astronomer who later lived in France and Prussia. ... Leonhard Paul Euler (pronounced Oiler; IPA ) (April 15, 1707 â€“ September 18 [O.S. September 7] 1783) was a pioneering Swiss mathematician and physicist, who spent most of his life in Russia and Germany. ... For other persons named William Hamilton, see William Hamilton (disambiguation). ... For other meanings of mathematics or uses of math and maths, see Mathematics (disambiguation) and Math (disambiguation). ... A magnet levitating above a high-temperature superconductor demonstrates the Meissner effect. ...

Among the great conceptual achievements of the 19th and 20th centuries were the consolidation of the idea of energy by the inclusion of heat, then electricity and magnetism and light, and finally mass. The laws of thermodynamics, and especially the introduction of the singular concept of entropy, filled in a great missing link in the attempt to explain why things happen. Alternative meaning: Nineteenth Century (periodical) (18th century &#8212; 19th century &#8212; 20th century &#8212; more centuries) As a means of recording the passage of time, the 19th century was that century which lasted from 1801-1900 in the sense of the Gregorian calendar. ... (19th century - 20th century - 21st century - more centuries) Decades: 1900s 1910s 1920s 1930s 1940s 1950s 1960s 1970s 1980s 1990s As a means of recording the passage of time, the 20th century was that century which lasted from 1901&#8211;2000 in the sense of the Gregorian calendar (1900&#8211;1999... For other uses, see Heat (disambiguation) In physics, heat, symbolized by Q, is energy transferred from one body or system to another due to a difference in temperature. ... Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, composed of the electric field and the magnetic field. ... For other uses, see Light (disambiguation). ... For other uses, see Mass (disambiguation). ... The laws of thermodynamics, in principle, describe the specifics for the transport of heat and work in thermodynamic processes. ... For other uses, see: information entropy (in information theory) and entropy (disambiguation). ...

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 was given a kinematic explanation by general relativity. Quantum mechanics led to an understanding of blackbody radiation and of anomalies in the specific heats of solids — and finally to an understanding of the internal structures of atoms and molecules. Modern physics may refer to: Quantum mechanics Theory of relativity 20th-century physics in general See also History of physics This is a disambiguation page: a list of articles associated with the same title. ... Two-dimensional analogy of space-time curvature described in General Relativity. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Gravity is a force of attraction that acts between bodies that have mass. ... In physics, kinematics is the branch of mechanics concerned with the motions of objects without being concerned with the forces that cause the motion. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... Electromagnetic waves can be imagined as a self-propagating transverse oscillating wave of electric and magnetic fields. ... Look up anomaly in Wiktionary, the free dictionary. ... Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the temperature of a unit quantity of a substance by a certain temperature interval. ... For other uses, see Solid (disambiguation). ... Properties For other meanings of Atom, see Atom (disambiguation). ... 3D (left and center) and 2D (right) representations of the terpenoid molecule atisane. ...

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 a new branch of mathematics: infinite, orthogonal series. Leibniz redirects here. ... Jean Baptiste Joseph Fourier (March 21, 1768 - May 16, 1830) was a French mathematician and physicist who is best known for initiating the investigation of Fourier series and their application to problems of heat flow. ... The Fourier series is a mathematical tool used for analyzing periodic functions by decomposing such a function into a weighted sum of much simpler sinusoidal component functions sometimes referred to as normal Fourier modes, or simply modes for short. ...

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. For other uses, see Universe (disambiguation). ... This article is about the physics subject. ... For the novel, see The Elementary Particles. ...

### Prominent theoretical physicists

Famous theoretical physicists include

## Mainstream theories

Mainstream theories (sometimes referred to as central theories) are 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.

### Examples

In physics, black hole thermodynamics is the area of study that seeks to reconcile the laws of thermodynamics with the existence of black hole event horizons. ... Classical mechanics (commonly confused with Newtonian mechanics, which is a subfield thereof) is used for describing the motion of macroscopic objects, from projectiles to parts of machinery, as well as astronomical objects, such as spacecraft, planets, stars, and galaxies. ... Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ... In physics, dynamics is the branch of classical mechanics that is concerned with the effects of forces on the motion of objects. ... For other uses, see Dark matter (disambiguation). ... Electromagnetism is the physics of the electromagnetic field: a field which exerts a force on particles that possess the property of electric charge, and is in turn affected by the presence and motion of those particles. ... There are two types of field theory in physics: Classical field theory, the theory and dynamics of classical fields. ... Fluid dynamics is the sub-discipline of fluid mechanics dealing with fluids (liquids and gases) in motion. ... For a less technical and generally accessible introduction to the topic, see Introduction to general relativity. ... Molecular modelling is a collection of techniques to model or mimic the behaviour of molecules. ... Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the Relativistic Heavy Ion Collider. ... This article is about the physics subject. ... For a less technical and generally accessible introduction to the topic, see Introduction to quantum mechanics. ... Quantum field theory (QFT) is the quantum theory of fields. ... Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. ... The scientific school of Quantum electrochemistry began to form in 1960s under ruling of Revaz Dogonadze. ... Quantum chromodynamics (abbreviated as QCD) is the theory of the strong interaction (color force), a fundamental force describing the interactions of the quarks and gluons found in hadrons (such as the proton, neutron or pion). ... Solid-state physics, the largest branch of condensed matter physics, is the study of rigid matter, or solids. ... Condensed matter physics is the field of physics that deals with the macroscopic physical properties of matter. ... A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... For a less technical and generally accessible introduction to the topic, see Introduction to special relativity. ... The Standard Model of Fundamental Particles and Interactions For the Standard Model in Cryptography, see Standard Model (cryptography). ... Statistical mechanics is the application of probability theory, which includes mathematical tools for dealing with large populations, to the field of mechanics, which is concerned with the motion of particles or objects when subjected to a force. ... Look up conservation of energy in Wiktionary, the free dictionary. ... Thermodynamics (from the Greek Î¸ÎµÏÎ¼Î·, therme, meaning heat and Î´Ï…Î½Î±Î¼Î¹Ï‚, dynamis, meaning power) is a branch of physics that studies the effects of changes in temperature, pressure, and volume on physical systems at the macroscopic scale by analyzing the collective motion of their particles using statistics. ...

## Proposed theories

The proposed theories of physics are usually relatively new theories which deal with 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.

### Examples

The causal sets programme is an approach to quantum gravity. ... In physical cosmology, dark energy is a hypothetical form of energy that permeates all of space and tends to increase the rate of expansion of the universe. ... In physical cosmology, the cosmological constant (usually denoted by the Greek capital letter lambda: Î›) was proposed by Albert Einstein as a modification of his original theory of general relativity to achieve a stationary universe. ... 2D analogy to a wormhole. ... A termite cathedral mound produced by a termite colony: a classic example of emergence in nature. ... For the album, see Grand Unification (album). ... Loop quantum gravity (LQG), also known as loop gravity and quantum geometry, is a proposed quantum theory of spacetime which attempts to reconcile the seemingly incompatible theories of quantum mechanics and general relativity. ... M-theory is a solution proposed for the unknown theory of everything which would combine all five superstring theories and 11-dimensional supergravity together. ... Interaction in the subatomic world: world lines of pointlike particles in the Standard Model or a world sheet swept up by closed strings in string theory This box:      String theory is a model of fundamental physics, whose building blocks are one-dimensional extended objects called strings, rather than the zero... This article or section is in need of attention from an expert on the subject. ... This page discusses Theories of Everything in physics. ...

## Fringe theories

Fringe theories include any new area of scientific endeavor in 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 a form of protoscience and others are a form of pseudoscience. The falsification of the original theory sometimes leads to reformulation of the theory. This article or section does not cite its references or sources. ... A typical 18th century phrenology chart. ...

### Examples

* These theories are both proposed and fringe theories. This article or section contains information that has not been verified and thus might not be reliable. ... For the album, see Grand Unification (album). ... The luminiferous aether: it was hypothesised that the Earth moves through a medium of aether that carries light In the late 19th century luminiferous aether (light-bearing aether) was the term used to describe a medium for the propagation of light. ... In cosmology, the steady state theory (also known as the Infinite Universe Theory or continuous creation) is a model developed in 1948 by Fred Hoyle, Thomas Gold, Hermann Bondi and others as an alternative to the Big Bang theory (known, usually, as the standard cosmological model). ... This page discusses Theories of Everything in physics. ... A metatheory is a theory which concerns itself with another theory, or theories. ... Results from FactBites:

 Theoretical physics - Wikipedia, the free encyclopedia (1184 words) Theoretical physics employs mathematical models and abstractions, as opposed to experimental physics, in an attempt to understand Nature. 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. Modern theoretical physics attempts to unify theories and explain phenomena in further attempts to understand the Universe, from the cosmologic to the elementary particle scale.
More results at FactBites »

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