- Theoretical physics
**Theoretical physics**employsmathematical model s andabstraction s ofphysics in an attempt to explain experimental data taken of the natural world. Its central core ismathematical physics ^{1}, though other conceptual techniques are also used. The goal is to rationalize, explain and predict physical phenomena. The advancement ofscience depends in general on the interplay betweenexperiment al studies andtheory . In some cases, theoretical physics adheres to standards of mathematical rigor while giving little weight to experiments and observations. For example, while developingspecial relativity ,Albert Einstein was concerned with theLorentz transformation which leftMaxwell's equations invariant, but was apparently uninterested in theMichelson-Morley experiment on Earth's drift through a luminiferous ether. On the other hand, Einstein was awarded theNobel Prize for explaining thephotoelectric effect , previously an experimental result lacking a theoretical formulation.**Overview**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 a mathematicaltheorem in that while both are based on some form ofaxioms , judgment of mathematical applicability is not based on agreement with any experimental results.Rquote|right

$mathrm\{Ric\}\; =\; k,g$"An

Einstein manifold , used ingeneral relativity to describe the curvature ofspacetime "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 themusic al tone it produces, and how to calculate the length of arectangle 's diagonal. Other examples includeentropy 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 continuouslyvariable .Sometimes the vision provided by pure mathematical systems can provide clues to how a physical system might be modeled; e.g., the notion, due to Riemann and others, that

space itself might be curved.Theoretical advances may consist in setting aside old, incorrect

paradigm s (e.g., Burning consists of evolvingphlogiston , or Astronomical bodies revolve around theEarth ) or may be an alternative model that provides answers that are more accurate or that can be more widely applied.Physical theories become accepted if they are able to make correct predictions and (few) incorrect ones. The theory should have, at least as a secondary objective, 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 a wide range of phenomena. Testing the consequences of a theory is part of thescientific method .Physical theories can be grouped into three categories: "mainstream theories", "proposed theories" and "fringe theories".

**History**Theoretical physics began at least 2,300 years ago under the pre-Socratic Greek philosophers, and continued by

Plato ; andAristotle , whose views held sway for a millennium. Inmedieval times, during the rise of the universities, the only acknowledged intellectual disciplines weretheology ,mathematics ,medicine , andlaw . As the concepts of matter, energy, space, time and causality slowly began to acquire the form we know today, other sciences spun off from the rubric ofnatural philosophy . During theMiddle Ages andRenaissance , the concept ofexperiment al science, thecounterpoint to theory, began with scholars such asIbn al-Haytham andFrancis Bacon . The modern era of theory began perhaps with the Copernican paradigm shift inastronomy , soon followed byJohannes Kepler 's expressions for planetary orbits, which summarized the meticulous observations ofTycho Brahe .The great push toward the modern concept of explanation started with Galileo, one of the few

physicist s who was both a consummate theoretician and a greatexperimentalist . Theanalytic geometry and mechanics of Descartes was incorporated into thecalculus and mechanics ofIsaac Newton , another theoretician/experimentalist of the highest order.Joseph-Louis Lagrange ,Leonhard Euler andWilliam Rowan Hamilton would extend the theory of classical mechanics considerably. Each of these individuals picked up the interactive intertwining ofmathematics andphysics begun two millennia earlier by Pythagoras.Among the great conceptual achievements of the 19th and 20th centuries were the consolidation of the idea of

energy by the inclusion ofheat , thenelectricity and magnetism andlight , and finallymass . Thelaws of thermodynamics , and especially the introduction of the singular concept ofentropy began to provide a macroscopic explanation for the properties of matter.The pillars of

modern physics , and perhaps the most revolutionary theories in the history of physics, have been relativity theory andquantum mechanics . Newtonian mechanics was subsumed under special relativity and Newton'sgravity was given akinematic explanation bygeneral relativity . Quantum mechanics led to an understanding of blackbody radiation and of anomalies in the specific heats ofsolid s — and finally to an understanding of the internal structures ofatom s andmolecule s.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.

Modern theoretical physics attempts to unify theories and explain phenomena in further attempts to understand the

Universe , from the cosmological to theelementary particle scale. Where experimentation cannot be done, theoretical physics still tries to advance through the use of mathematical models. Some of their most prominent and well thought out advancements in this field include:**Prominent theoretical physicists**Famous "theoretical physicists" include

*Christiaan Huyghens (1629-1695)

*Isaac Newton (1643-1727)

*Leonhard Euler (1707-1783)

*Joseph Louis Lagrange (1736-1813)

*Pierre-Simon Laplace (1749-1827)

*Joseph Fourier (1768-1830)

*Nicolas Léonard Sadi Carnot (1796-1842)

*William Rowan Hamilton (1805-1865)

*Rudolf Clausius (1822-1888)

*James Clerk Maxwell (1831-1879)

*J. Willard Gibbs (1839-1903)

*Hendrik A. Lorentz (1853-1928)

*Nikola Tesla (1856-1943)

*Max Planck (1858-1947)

*Albert Einstein (1879-1955)

*Niels Bohr (1885-1962)

*Werner Heisenberg (1901-1976)

*Max Born (1882-1970)

*Erwin Schrödinger (1887-1961)

*Louis de Broglie (1892-1987)

*Satyendra Nath Bose (1894-1974)

*Wolfgang Pauli (1900-1958)

*Enrico Fermi (1901-1954)

*Paul Dirac (1902-1984)

*Eugene Wigner (1902-1995)

*Robert Oppenheimer (1904-1967)

*Sin-Itiro Tomonaga (1906-1979)

*Hideki Yukawa (1907-1981)

*Lev Landau (1908-1967)

*Julian Schwinger (1918-1994)

*Richard Feynman (1918-1988)

*Chen Ning Yang (1922- )

*Freeman Dyson (1923- )

*Abdus Salam (1926-1996)

*Murray Gell-Mann (1929- )

*John Polkinghorne (1930- )

*George Sudarshan (1931- )

*Sheldon Glashow (1932- )

*Steven Weinberg (1933- )

*Stephen Hawking (1942- )

*Gerardus 't Hooft (1946- )

*Jacob Bekenstein (1947-)

*Michio Kaku (1947-)

*Edward Witten (1951- )**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**

*Black hole thermodynamics

*Classical mechanics

*Condensed matter physics

* Dynamics

*Dark matter

*Electromagnetism

* Field theory

*Fluid dynamics

*General relativity

*Molecular modeling

*Particle physics

*Physical cosmology

*Quantum mechanics

*Quantum field theory

*Quantum information theory

*Quantum electrodynamics

*Quantum electrochemistry

*Quantum chromodynamics

*Solid state physics orCondensed Matter Physics and the electronic structure of materials

*Special relativity

*Standard Model

*Statistical mechanics

*Conservation of energy

*Thermodynamics **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**

*Causal Sets

*Dark energy or Einstein's Cosmological Constant

*Einstein-Rosen Bridge

*Emergence

*Grand unification theory

*Heim Quantum Theory

*Loop quantum gravity

*M-theory

*String theory

*Supersymmetry

*Theory of everything **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 ofpseudoscience . The falsification of the original theory sometimes leads to reformulation of the theory.**Examples***

Dynamic theory of gravity

*Grand unification theory

*Luminiferous aether

*Steady state theory

*Theory of everything

*Metatheory **ee also***

Experimental physics

*List of theoretical physicists

***Notes***fnb|1 Sometimes "mathematical physics" and "theoretical physics" are used synonymously to refer to the latter.

**External links*** [

*http://superstringtheory.com/history/history3.html Timeline of Theoretical Physics*]

* [*http://ctp.lns.mit.edu/index.html MIT Center for Theoretical Physics*]

* [*http://www.perimeterinstitute.ca Perimeter Institute for Theoretical Physics*]

* [*http://www.ejtp.com Electronic Journal of Theoretical Physics (EJTP)*]

* [*http://www.phys.uu.nl/~thooft/theorist.html How to Become a Theoretical Physicist by a Nobel Laureate*]

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