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Overview of technology and applied sciences

Technological concepts and issues •

Diffusion of innovations • Doomsday device • Externality •

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Technologies and applied sciences • Aerospace • Agriculture, agricultural science, & agronomy • Architecture • Artificial intelligence • Automation • Automobile • Big Science • Biotechnology • Cartography • Chemical engineering • Communication • Computer science (Computing, Programming, Software engineering,Unsolved problems in computer science, Unsolved problems in software engineering) • Construction • Dentistry • Design • Education • Electronics • Energy development • Energy storage • Engineering • Ergonomics • Family and consumer science • Firefighting • Forensics • Forestry • Free software • Health sciences • Health • Industry • Information science • Information technology • Internet • Library and information science • Machines • Management • Manufacturing • Marketing • Mass communication • Mass production • Medicine (Unsolved problems in medicine, Unsolved problems in neuroscience) • Military science • Military technology and equipment • Mining • Nanotechnology • Nuclear technology • Nutrition • Processes • Robotics • Space exploration • Techniques • Technology forecasting • Telecommunications • Tools • Transport (By country) • Vehicles • Weapons |}

Acoustics, the study of sound waves, is used everywhere we wish to hear, for example in music, speech, and audible alarms.
Agrophysics is the study of the physics in agronomy.
Biophysics is the interface of biology and physics.
Chemical physics studies the structure and dynamics of ions, free radicals, polymers, clusters, and molecules, using both classical and quantum mechanical viewpoints.
Communications has used physics extensively, for example in the Bell Laboratories.
Econophysics is the interface of economics and physics.
Engineering physics graduates specialists in optics, nanotechnology, control theory, aerodynamics, or solid-state physics.
Fluid mechanics is the study of fluids (liquids and gases) at rest and in motion.
Geophysics is the physics of Earth.
Lasers and radar were developed in the laboratories, used by the military, and now have extensive peacetime uses. Quantum electronics includes the study of lasers.
Medical physics includes the standards for radiation exposure and infrastructure for radiology.
Optics has existed as a science for over 1000 years. Like acoustics, it has its own journals, practioners, and university departments, as well as industries which utilize those graduates.
Plasma physics is the physics of an ionized gas.
Physics of computation
Solid state physics, including the material properties of semiconductor devices and integrated circuits.

Engineering utilizes physics in service of technology rather than science.

Materials science is the systematic study of the properties of materials.
Nanotechnology studies the creation of machines less than a micrometer in size.
Optoelectronics creates devices which use light rather than current.
Photovoltaics, or solar cells, promise to generate current from light.
Physical chemistry
Quantum chemistry models matter using quantum mechanics.
Quantum information science applies qubit devices.
Vehicle dynamics is a form of kinematics.

The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density.

Newton's first, second, and third laws of motion.

Maxwell's equations of electromagnetism.

The conservation laws: mass, charge, etc.

Boltzmann's equation of statistical mechanics.

Physics is the science whose goal is to understand nature in terms of simple and universal truths. Physicists create theories to describe the underlying laws of nature in a predictive way, and state their theories in the language of mathematics to make them succinct and precise. Physics is based on scientific method; experimental observation is the test of any physical theory.

Physics research is divided into two main branches: experimental physics and theoretical physics. Experimental physics focuses mainly on empirical research, and on the development and testing of theories against practical experiment. Theoretical physics is more closely related to mathematics, and involves generating and working through the mathematical implications of systems of physical theories, even where experimental evidence of their validity may not be immediately available.

Introduction

Scope and goals of physics

The deepest visible-light image of the universe, the Hubble Ultra Deep Field

The sweep of physics is broad, from the tiniest components of matter and the forces that hold it together, to galaxies and even larger structures. Physicists also study matter in all four of its basic states^[1]; gases, solids, liquids and plasmas, and the phase transitions between these states.

Physics is primarily focused on the goal of formulating ever simpler, more general, and more accurate rules that govern the behavior of the natural world. One of the major goals of physics is the formulation of theories of universal applicability. Therefore, physics can be viewed as the study of those universal laws which define, at the most fundamental level possible, the behavior of the physical universe. Currently, physicists have narrowed down four forces (or interactions): gravity, electromagnetism, the weak force associated with radioactivity, and the strong force which holds atoms together. However, these forces are believed to be different aspects of a single force, and the construction of theories which achieve this feat is an area of intense study.

Physics uses the scientific method

Physics uses the scientific method. That is, that the sole test of the validity of a physical theory be comparison with observation. Experiments and observations are to be collected and matched with the predictions of theories, thus verifying or falsifying the theory.

Those theories which are very well supported by data and which are especially simple and general have been called scientific laws. Of course, all theories, including those called laws, can also be replaced by more accurate and more general statements, if a disagreement of theory with observed data were to be found.^[2]

Data collection and theory development

There are many approaches to studying physics, and many different kinds of activities in physics. There are two main types of activities in physics; the collection of data and the development of theories.

The data in some subfields of physics is amenable to experiment. For example, condensed matter physics and nuclear physics benefit from the ability to perform experiments. Sometimes experiments are done to explore nature, and in other cases experiments are performed to produce data to compare with the predictions of theories.

Some other fields in physics like astrophysics and geophysics are primarily observational sciences because most their data has to be collected passively instead of through experimentation. Nevertheless, observational programs in these fields uses many of the same tools and technology that are used in the experimental subfields of physics. The accumulated body of knowledge in some area of physics through experiment and observation is known as phenomenology.

Theoretical physics often uses quantitative approaches to develop the theories that attempt to explain the data. In this way, theoretical physics often relies heavily on tools from mathematics and computational technologies (particularly in the subfield known as computational physics). Theoretical physics often involves creating quantitative predictions of physical theories, and comparing these predictions quantitatively with data. Theoretical physics sometimes creates models of physical systems before data are available to test and validate these models.

These two main activities in physics, data collection and theory production and testing, draw on many different skills. This has lead to a lot of specialization in physics, and the introduction, development and use of tools from other fields. For example, theoretical physicists apply mathematics and numerical analysis and statistics and probability and computers and computer software in their work. Experimental physicists develop instruments and techniques for collecting data, drawing on engineering and computer technology and many other fields of technology. Often the tools from these other areas are not quite appropriate for the needs of physics, and need to be adapted or more advanced versions have to be produced.

The culture of physics research differs from the other sciences in the separation of theory from data collection through experiment and observation. Since the 20th century, most individual physicists have specialized in either theoretical physics or experimental physics. The great Italian physicist Enrico Fermi (1901—1954), who made fundamental contributions to both theory and experimentation in nuclear physics, was a notable exception. In contrast, almost all the successful theorists in biology and chemistry (e.g. American quantum chemist and biochemist Linus Pauling) have also been experimentalists, though this is changing as of late.

Although theory and experiment are usually performed by separate groups, they are strongly dependent on each other. Progress in physics frequently comes about when experimentalists make a discovery that existing theories cannot account for, necessitating the formulation of new theories. Likewise, ideas arising from theory often inspire new experiments. In the absence of experiment, theoretical research can go in the wrong direction; this is one of the criticisms that has been leveled against M-theory, a popular theory in high-energy physics for which no practical experimental test has ever been devised.

Physics is quantitative

Physics is more quantitative than most other sciences. That is, many of the observations experimental results in physics are numerical measurements. Most of the theories in physics use mathematics to express their principles. Most of the predictions from these theories are numerical. This is because of the areas which physics has addressed are more amenable to quantitative approaches than other areas. Physical definitions, models and theories can often be expressed using mathematical relations. Sciences also tend to become more quantitative with time as they become more highly developed, and physics is one of the older sciences.^{[citation needed]}

A key difference between physics and mathematics is that because physics is ultimately concerned with descriptions of the material world, it tests its theories by comparing the predictions of its theories with data from observations or experiments, whereas mathematics is concerned with abstract logical patterns not limited by those observed in the real world (because the real world is limited in the number of dimensions and in many other ways it does not have to correspond to richer mathematical structures). The distinction, however, is not always clear-cut. There is a large area of research intermediate between physics and mathematics, known as mathematical physics.

Relation to mathematics and the other sciences

Discoveries in physics find connections throughout many fields of science. Since physics treats the core workings of the universe, including the quantum mechanical details which underpin all atomic interactions, it is often thought of as the foundational science, upon which stands the "central science" of chemistry, and the earth sciences, biological sciences, and social sciences. Important conservation laws such as the conservation of energy, conservation of momentum, and conservation of charge, and other discoveries in basic physics have important ramifications in the other sciences.

Physics relies on mathematics to provide the logical framework in which physical laws can be precisely formulated and their predictions quantified. Physical definitions, models and theories can be succinctly expressed using mathematical relations. There is a large area of research intermediate between physics and mathematics, known as mathematical physics.

As analytic solutions are not always possible, numerical analysis and simulations must be utilized. Thus, scientific computation is an integral part of physics, and the field of computational physics is an active area of research.

Beyond the known universe, the field of theoretical physics also deals with hypothetical issues^[3], such as parallel universes, a multiverse, or whether the universe could have expanded as predominantly antimatter rather than matter.

Mathematics is often said to be the language of physics, and so physics shares a close connection with mathematics. Physics is also intimately related to many other sciences, as well as applied fields like engineering and medicine. The principles of physics find applications throughout the other natural sciences as they depend on the interactions of the fundamental constituents of the natural world. Some of the phenomena studied in physics, such as the phenomenon of conservation of energy, are common to all material systems. These are often referred to as laws of physics. Others, such as superconductivity, stem from these laws, but are not laws themselves because they only appear in some systems. Physics is often said to be the "fundamental science" (chemistry is sometimes included), because each of the other disciplines (biology, chemistry, geology, material science, engineering, medicine etc.) deals with particular types of material systems that obey the laws of physics. For example, chemistry is the science of collections of matter (such as gases and liquids formed of atoms and molecules) and the processes known as chemical reactions that result in the change of chemical substances. The structure, reactivity, and properties of a chemical compound are determined by the properties of the underlying molecules, which can be described by areas of physics such as quantum mechanics (called in this case quantum chemistry), thermodynamics, and electromagnetism.

Philosophical Implications

Physics in many ways steamed from Greek philosophy. These early philosophical investigations, known as natural philosophy usually did not involve much experimention or detailed observation (a priori resoning). It was not till much later that the use of experiments (a posteriori) became mainstream, and it was not until the 19th century that physics was realized as a positive science; and a distinct discipline separate from philosophy.

They study of the philosophical issues surrounding physics is called philosophy of physics. Philosophy of physics is a way of answering metaphysical issues using the results of physics. Some important issues that are discussed are various interpretations of quantum mechanics, relativity, and cosmology, and what they tell us about the nature of space and time, causality, and determinism.

History

Aristotle

Etymology

(from the Greek, φύσις (phúsis), "nature" and φυσικός (phusikós), "natural")

Ancient Times

Since antiquity, people have tried to understand the behavior of matter: why unsupported objects drop to the ground, why different materials have different properties, and so forth. Also a mystery was the character of the universe, such as the form of the Earth and the behavior of celestial objects such as the Sun and the Moon. Several theories were proposed, most of which were wrong. These theories were largely couched in philosophical terms, and never verified by systematic experimental testing as is popular today. The works of Ptolemy and Aristotle however, were also not always found to match everyday observations. There were exceptions and there are anachronisms: for example, Indian philosophers and astronomers gave many correct descriptions in atomism and astronomy, and the Greek thinker Archimedes derived many correct quantitative descriptions of mechanics and hydrostatics.

The willingness to question previously held truths and search for new answers eventually resulted in a period of major scientific advancements, now known as the Scientific Revolution of the late 17th century. The precursors to the scientific revolution can be traced back to the important developments made in India and Persia, including the elliptical model of the planets based on the heliocentric solar system of gravitation developed by Indian mathematician-astronomer Aryabhata; the basic ideas of atomic theory developed by Hindu and Jaina philosophers; the theory of light being equivalent to energy particles developed by the Indian Buddhist scholars Dignāga and Dharmakirti; the optical theory of light developed by Persian scientist Alhazen; the Astrolabe invented by the Persian Mohammad al-Fazari; and the significant flaws in the Ptolemaic system pointed out by Persian scientist Nasir al-Din al-Tusi. As the influence of the Islamic Caliphate expanded to Europe, the works of Aristotle preserved by the Arabs, and the works of the Indians and Persians, became known in Europe by the 12th and 13th centuries.

The Scientific Revolution

Galileo

The Scientific Revolution is held by most historians (e.g., Howard Margolis) to have begun in 1543, when the first printed copy of Nicolaus Copernicus's De Revolutionibus (most of which had been written years prior but whose publication had been delayed) was brought to the influential Polish astronomer from Nuremberg.

Sir Isaac Newton

Further significant advances were made over the following century by Galileo Galilei, Christiaan Huygens, Johannes Kepler, and Blaise Pascal. During the early 17th century, Galileo pioneered the use of experimentation to validate physical theories, which is the key idea in modern scientific method. Galileo formulated and successfully tested several results in dynamics, in particular the Law of Inertia. In 1687, Newton published the Principia, detailing two comprehensive and successful physical theories: Newton's laws of motion, from which arise classical mechanics; and Newton's Law of Gravitation, which describes the fundamental force of gravity. Both theories agreed well with experiment. The Principia also included several theories in fluid dynamics. Classical mechanics was re-formulated and extended by Leonhard Euler, French mathematician Joseph-Louis Comte de Lagrange, Irish mathematical physicist William Rowan Hamilton, and others, who produced new results in mathematical physics. The law of universal gravitation initiated the field of astrophysics, which describes astronomical phenomena using physical theories.

After Newton defined classical mechanics, the next great field of inquiry within physics was the nature of electricity. Observations in the 17th and 18th century by scientists such as Robert Boyle, Stephen Gray, and Benjamin Franklin created a foundation for later work. These observations also established our basic understanding of electrical charge and current.

James Clerk Maxwell

In 1821, the English physicist and chemist Michael Faraday integrated the study of magnetism with the study of electricity. This was done by demonstrating that a moving magnet induced an electric current in a conductor. Faraday also formulated a physical conception of electromagnetic fields. James Clerk Maxwell built upon this conception, in 1864, with an interlinked set of 20 equations that explained the interactions between electric and magnetic fields. These 20 equations were later reduced, using vector calculus, to a set of four equations by Oliver Heaviside.

Albert Einstein in 1947

In addition to other electromagnetic phenomena, Maxwell's equations also can be used to describe light. Confirmation of this observation was made with the 1888 discovery of radio by Heinrich Hertz and in 1895 when Wilhelm Roentgen detected X rays. The ability to describe light in electromagnetic terms helped serve as a springboard for Albert Einstein's publication of the theory of special relativity in 1905. This theory combined classical mechanics with Maxwell's equations. The theory of special relativity unifies space and time into a single entity, spacetime. Relativity prescribes a different transformation between reference frames than classical mechanics; this necessitated the development of relativistic mechanics as a replacement for classical mechanics. In the regime of low (relative) velocities, the two theories agree. Einstein built further on the special theory by including gravity into his calculations, and published his theory of general relativity in 1915.

One part of the theory of general relativity is Einstein's field equation. This describes how the stress-energy tensor creates curvature of spacetime and forms the basis of general relativity. Further work on Einstein's field equation produced results which predicted the Big Bang, black holes, and the expanding universe. Einstein believed in a static universe and tried (and failed) to fix his equation to allow for this. However, by 1929 Edwin Hubble's astronomical observations suggested that the universe is expanding.

From the late 17th century onwards, thermodynamics was developed by physicist and chemist Boyle, Young, and many others. In 1733, Bernoulli used statistical arguments with classical mechanics to derive thermodynamic results, initiating the field of statistical mechanics. In 1798, Thompson demonstrated the conversion of mechanical work into heat, and in 1847 Joule stated the law of conservation of energy, in the form of heat as well as mechanical energy. Ludwig Boltzmann, in the 19th century, is responsible for the modern form of statistical mechanics.

1900 to Present

In 1895, Röntgen discovered X-rays, which turned out to be high-frequency electromagnetic radiation. Radioactivity was discovered in 1896 by Henri Becquerel, and further studied by Marie Curie, Pierre Curie, and others. This initiated the field of nuclear physics.

In 1897, Joseph J. Thomson discovered the electron, the elementary particle which carries electrical current in circuits. In 1904, he proposed the first model of the atom, known as the plum pudding model. (The existence of the atom had been proposed in 1808 by John Dalton.)

These discoveries revealed that the assumption of many physicists that atoms were the basic unit of matter was flawed, and prompted further study into the structure of atoms.

File:Ernest Rutherford.jpg

Ernest Rutherford

In 1911, Ernest Rutherford deduced from scattering experiments the existence of a compact atomic nucleus, with positively charged constituents dubbed protons. Neutrons, the neutral nuclear constituents, were discovered in 1932 by Chadwick. The equivalence of mass and energy (Einstein, 1905) was spectacularly demonstrated during World War II, as research was conducted by each side into nuclear physics, for the purpose of creating a nuclear bomb. The German effort, led by Heisenberg, did not succeed, but the Allied Manhattan Project reached its goal. In America, a team led by Fermi achieved the first man-made nuclear chain reaction in 1942, and in 1945 the world's first nuclear explosive was detonated at Trinity site, near Alamogordo, New Mexico.

In 1900, Max Planck published his explanation of blackbody radiation. This equation assumed that radiators are quantized in nature, which proved to be the opening argument in the edifice that would become quantum mechanics. Beginning in 1900, Planck, Einstein, Niels Bohr, and others developed quantum theories to explain various anomalous experimental results by introducing discrete energy levels. In 1925, Heisenberg and 1926, Schrödinger and Paul Dirac formulated quantum mechanics, which explained the preceding heuristic quantum theories. In quantum mechanics, the outcomes of physical measurements are inherently probabilistic; the theory describes the calculation of these probabilities. It successfully describes the behavior of matter at small distance scales. During the 1920s Erwin Schrödinger, Werner Heisenberg, and Max Born were able to formulate a consistent picture of the chemical behavior of matter, a complete theory of the electronic structure of the atom, as a byproduct of the quantum theory.

File:Richard feynman.jpg

Richard Feynman

Quantum field theory was formulated in order to extend quantum mechanics to be consistent with special relativity. It was devised in the late 1940s with work by Richard Feynman, Julian Schwinger, Sin-Itiro Tomonaga, and Freeman Dyson. They formulated the theory of quantum electrodynamics, which describes the electromagnetic interaction, and successfully explained the Lamb shift. Quantum field theory provided the framework for modern particle physics, which studies fundamental forces and elementary particles.

Chen Ning Yang and Tsung-Dao Lee, in the 1950s, discovered an unexpected asymmetry in the decay of a subatomic particle. In 1954, Yang and Robert Mills then developed a class of gauge theories which provided the framework for understanding the nuclear forces. The theory for the strong nuclear force was first proposed by Murray Gell-Mann. The electroweak force, the unification of the weak nuclear force with electromagnetism, was proposed by Sheldon Lee Glashow, Abdus Salam and Steven Weinberg and confirmed in 1964 by James Watson Cronin and Val Fitch. This led to the so-called Standard Model of particle physics in the 1970s, which successfully describes all the elementary particles observed to date.

Quantum mechanics also provided the theoretical tools for condensed matter physics, whose largest branch is solid state physics. It studies the physical behavior of solids and liquids, including phenomena such as crystal structures, semiconductivity, and superconductivity. The pioneers of condensed matter physics include Bloch, who created a quantum mechanical description of the behavior of electrons in crystal structures in 1928. The transistor was developed by physicists John Bardeen, Walter Houser Brattain and William Bradford Shockley in 1947 at Bell Telephone Laboratories.

right|130px The two themes of the 20th century, general relativity and quantum mechanics, appear inconsistent with each other. General relativity describes the universe on the scale of planets and solar systems while quantum mechanics operates on sub-atomic scales. This challenge is being attacked by string theory, which treats spacetime as composed, not of points, but of one-dimensional objects, strings. Strings have properties like a common string (e.g., tension and vibration). The theories yield promising, but not yet testable results. The search for experimental verification of string theory is in progress.

The United Nations declared the year 2005, the centenary of Einstein's annus mirabilis, as the World Year of Physics.

Branches of physics

Classical, quantum and modern physics

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Since the early twentieth century, it has become clear that the laws of nature appear to follow the postulates of quantum mechanics, and the theories that follow these postulates are said to have been quantized. To this effect, all results that were not quantized are called "classical": this includes the special and general theories of relativity. Classical theories are, generally, much easier to work with and much research is still being conducted on them without the express aim of quantization. Simply because a result is "classical" does not mean that it was discovered before the advent of quantum mechanics.

However, because relativity and quantum mechanics provide the most complete known description of fundamental interactions, and because the changes brought by these two frameworks to the physicist's world view were revolutionary, the term "modern physics" is used to describe physics which relies on these two theories. Colloquially, modern physics can be described as the physics of extremes: from systems at the extremely small (atoms, nuclei, fundamental particles) to the extremely large (the Universe) and of the extremely fast (relativity).

Central theories

While physics deals with a wide variety of systems, there are certain theories that are used by all physicists. Each of these theories were experimentally tested numerous times and found correct as an approximation of Nature (within a certain domain of validity). For instance, the theory of classical mechanics accurately describes the motion of objects, provided they are much larger than atoms and moving at much less than the speed of light. These theories continue to be areas of active research; for instance, a remarkable aspect of classical mechanics known as chaos was discovered in the 20th century, three centuries after the original formulation of classical mechanics by Isaac Newton (1642—1727). These "central theories" are important tools for research into more specialized topics, and any physicist, regardless of his or her specialization, is expected to be literate in them.

Major fields of physics

Classification of physics fields by the types of effects that need to be accounted for

Contemporary research in physics is divided into several distinct fields that study different aspects of the material world. Condensed matter physics, by most estimates the largest single field of physics, is concerned with how the properties of bulk matter, such as the ordinary solids and liquids we encounter in everyday life, arise from the properties and mutual interactions of the constituent atoms. The field of atomic, molecular, and optical physics deals with the behavior of individual atoms and molecules, and in particular the ways in which they absorb and emit light. The field of particle physics, also known as "high-energy physics", is concerned with the properties of submicroscopic particles much smaller than atoms, including the elementary particles from which all other units of matter are constructed. Finally, the field of astrophysics applies the laws of physics to explain celestial phenomena, ranging from the Sun and the other objects in the solar system to the universe as a whole.

Since the 20th century, the individual fields of physics have become increasingly specialized, and nowadays it is not uncommon for physicists to work in a single field for their entire careers. "Universalists" like Albert Einstein (1879—1955) and Lev Landau (1908—1968), who were comfortable working in multiple fields of physics, are now very rare.

Current Research

Research in physics is progressing constantly on a large number of fronts, and is likely to do so for the foreseeable future.

In condensed matter physics, the biggest unsolved theoretical problem is the explanation for high-temperature superconductivity. Strong efforts, largely experimental, are being put into making workable spintronics and quantum computers.

In particle physics, the first pieces of experimental evidence for physics beyond the Standard Model have begun to appear. Foremost amongst these are indications that neutrinos have non-zero mass. These experimental results appear to have solved the long-standing solar neutrino problem in solar physics. The physics of massive neutrinos is currently an area of active theoretical and experimental research. In the next several years, particle accelerators will begin probing energy scales in the TeV range, in which experimentalists are hoping to find evidence for the Higgs boson and supersymmetric particles.

Theoretical attempts to unify quantum mechanics and general relativity into a single theory of quantum gravity, a program ongoing for over half a century, have not yet borne fruit. The current leading candidates are M-theory, superstring theory and loop quantum gravity.

Many astronomical and cosmological phenomena have yet to be satisfactorily explained, including the existence of ultra-high energy cosmic rays, the baryon asymmetry, the acceleration of the universe and the anomalous rotation rates of galaxies.

Although much progress has been made in high-energy, quantum, and astronomical physics, many everyday phenomena, involving complexity, chaos, or turbulence are still poorly understood. Complex problems that seem like they could be solved by a clever application of dynamics and mechanics, such as the formation of sandpiles, nodes in trickling water, the shape of water droplets, mechanisms of surface tension catastrophes, or self-sorting in shaken heterogeneous collections are unsolved. These complex phenomena have received growing attention since the 1970s for several reasons, not least of which has been the availability of modern mathematical methods and computers which enabled complex systems to be modeled in new ways. The interdisciplinary relevance of complex physics has also increased, as exemplified by the study of turbulence in aerodynamics or the observation of pattern formation in biological systems. In 1932, Horace Lamb correctly prophesized:

I am an old man now, and when I die and go to heaven there are two matters on which I hope for enlightenment. One is quantum electrodynamics, and the other is the turbulent motion of fluids. And about the former I am rather optimistic.

^{[citation needed]}

Applications and Influence

Physics is used heavily in engineering. For instance, electrical engineering is the study of the practical application of electromagnetism. Statics, a subfield of mechanics, is used in the building of bridges and other structures which do not move. Other examples include the use of acoustics to build better concert halls, and optics to create better optical devices. Among other things physics finds uses in making more realistic video games and movies, and in forensic investigations.

There are many fields of physics which have strong applied branches, as well as many related and overlapping fields from other disciplines that are closely related to applied physics. A small, non-exhaustive sampling of fields connected with applied physics is presented in the following table.

Fields of physics with strong applied branches
Acoustics, Agrophysics, Biophysics, Chemical Physics, Communication Physics, Econophysics, Engineering physics, Fluid dynamics, Geophysics, Laser Physics, Medical physics, Optics, Plasma physics, Physics of computation, Solid state physics
Fields closely related to applied physics
Engineering, Materials science, Nanotechnology, Optoelectronics, Photovoltaics, Physical chemistry, Quantum chemistry, Quantum electronics, Quantum information science, Vehicle dynamics

References

^ Counting the number of states of matter is difficult, since there are a number of more complicated assemblages of matter that can be thought of as states; see states of matter.
^ Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known to be limiting cases of other theories.
^ Concepts which are denoted hypothetical can change with time. For example, the atom of nineteenth century physics was denigrated by some, including Ernst Mach's critique of Ludwig Boltzmann's formulation of statistical mechanics. By the end of World War II, the atom was no longer deemed hypothetical.

Alpher, Herman, and Gamow. Nature 162,774 (1948). Wilson's 1978 Nobel lecture
C.S. Wu's contribution to the overthrow of the conservation of parity
Yang, Mills 1954 Physical Review 95, 631; Yang, Mills 1954 Physical Review 96, 191.

Aristotle's Physics, trans. by R. P. Hardie and R. K. Gaye
Physics and Math Textbooks Numerous online textbooks on Physics and Mathematics
Usenet Physics FAQ. A FAQ compiled by sci.physics and other physics newsgroups.
Physics.org - Web portal run by the Institute of Physics.
World of Physics. An online encyclopedic dictionary of physics.
Website of the Nobel Prize in Physics.
The Physics Network Official Physics Network
Physics Today - Your daily physics news and research source
The Skeptic's Guide to Physics
PlanetPhysics Online Physics
Physics 2005: Website of the World Year of Physics 2005
Physicsweb.org
[1] The Physics Community accepts contributions from those knowledgeable in physics
Contemporary Physics

Organizations

AIP.org Website of the American Institute of Physics
IOP.org Website of the Institute of Physics
APS.org Website of the American Physical Society
SPS National Website of the Society of Physics Students
Physics & Math Forums

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[1] Counting the number of states of matter is difficult, since there are a number of more complicated assemblages of matter that can be thought of as states; see states of matter.

[2] Some principles, such as Newton's laws of motion, are still generally called "laws" even though they are now known to be limiting cases of other theories.

[3] Concepts which are denoted hypothetical can change with time. For example, the atom of nineteenth century physics was denigrated by some, including Ernst Mach's critique of Ludwig Boltzmann's formulation of statistical mechanics. By the end of World War II, the atom was no longer deemed hypothetical.

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v t e Major branches of physics
Divisions	Pure Applied Engineering
Approaches	Experimental Theoretical Computational
Classical	Classical mechanics Newtonian Analytical Celestial Continuum Acoustics Classical electromagnetism Classical optics Ray Wave Thermodynamics Statistical Non-equilibrium
Modern	Relativistic mechanics Special General Nuclear physics Particle physics Quantum mechanics Atomic, molecular, and optical physics Atomic Molecular Modern optics Condensed matter physics Solid-state physics Crystallography
Interdisciplinary	Astrophysics Atmospheric physics Biophysics Chemical physics Geophysics Materials science Mathematical physics Medical physics Ocean physics Quantum information science
Related	History of physics Nobel Prize in Physics Philosophy of physics Physics education Timeline of physics discoveries

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Contents

Overview of technology and applied sciences

Introduction

Scope and goals of physics

Physics uses the scientific method

Data collection and theory development

Physics is quantitative

Relation to mathematics and the other sciences

Philosophical Implications

History

Etymology

Ancient Times

The Scientific Revolution

1900 to Present

Branches of physics

Classical, quantum and modern physics

Central theories

Major fields of physics

Current Research

Applications and Influence

See also

Mainstream physics

Related fields

Fringe theories

References

Further reading

Popular Reading

University Level Textbooks

Introductory

Undergraduate

Graduate

History

External links

General

Organizations