Physics

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Physics (from the Greek, φύσις (phúsis), "nature" and φυσική (phusiké), "knowledge of nature") is the science concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space and time. That is, physics deals with the elementary constituents of the Universe and their interactions, as well as the analysis of systems which are best understood in terms of these fundamental principles. Physics is a study of the inorganic, physical world, as opposed to the organic world of biology, physiology, etc. [1] Chemistry concerning the electro-chemical interactions of substances overlaps with physics.
Contents
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* 1 Introduction
* 2 Connected Studies
* 3 Branches of physics
o 3.1 Central theories
o 3.2 Major fields of physics
* 4 Classical, quantum and modern physics
* 5 Theoretical and experimental physics
o 5.1 Discredited theories
o 5.2 Phenomenology
* 6 Applied physics
* 7 History
* 8 Future directions
* 9 See also
* 10 Notes
* 11 Further reading
o 11.1 Popular reading
o 11.2 University-level textbooks
+ 11.2.1 Survey texts
+ 11.2.2 Undergraduate texts on specific topics
+ 11.2.3 Graduate texts
+ 11.2.4 Historical
* 12 External links
o 12.1 General
o 12.2 Organizations

[edit] Introduction

Physics attempts to describe the natural world by the application of the scientific method, including modelling by theoreticians. Formerly, physics included the study of natural philosophy, its counterpart which had been called "physics" (earlier physike) from classical times up to the separation of physics from philosophy as a positive science in the 19th century, as the study of the changing world by philosophy. Mixed questions, of which solutions can be attempted through the applications of both disciplines (e.g. the divisibility of the atom) can involve natural philosophy in physics (the science) and vice versa.

[edit] Connected Studies

Many other sciences and fields of thought are related to physics.

Discoveries in physics find connections throughout the other natural sciences as they regard the basic constituents of the Universe. 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. Other phenomena, 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", because each of the other sciences (biology, chemistry, geology, physiology, archaeology, anthropology, etc.) deals with particular types of material systems that obey the laws of physics. For example, chemistry is the science of matter (such as atoms and molecules) and the chemical substances that they form in the bulk. 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. (Refer to Branches of physics)

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

Physics is also closely related to engineering and technology. For instance, electrical engineering is the study of the practical application of electromagnetism. Statics, a subfield of mechanics, is responsible for the building of bridges. Further, physicists, or practitioners of physics, invent and design processes and devices, such as the transistor, whether in basic or applied research. Experimental physicists design and perform experiments with particle accelerators, nuclear reactors, telescopes, barometers, synchrotrons, cyclotrons, spectrometers, lasers, and other equipment.

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

[edit] Branches of physics

Physicists study a wide range of physical phenomena, from quarks to black holes, from individual atoms to the many-body systems of superconductors.

[edit] 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.

* Classical mechanics is a model of the physics of forces acting upon bodies. It is often referred to as "Newtonian mechanics" after Newton and his laws of motion. Classical mechanics is subdivided into statics (which models objects at rest), kinematics (which models objects in motion), and dynamics (which models objects subjected to forces). See also mechanics.

* Electromagnetism, or electromagnetic theory, is the physics of the electromagnetic field: a field, encompassing all of space, which exerts a force on those particles that possess the property of electric charge, and is in turn affected by the presence and motion of such particles. Electromagnetism encompasses various real-world electromagnetic phenomena.

* Thermodynamics is the branch of physics that deals with the action of heat and the conversions from one to another of various forms of energy. Thermodynamics is particularly concerned with how these affect temperature, pressure, volume, mechanical action, and work. Historically, it grew out of efforts to construct more efficient heat engines — devices for extracting useful work from expanding hot gases.

* Statistical mechanics, a related theory, is the branch of physics that analyzes macroscopic systems by applying statistical principles to their microscopic constituents and, thus, can be used to calculate the thermodynamic properties of bulk materials from the spectroscopic data of individual molecules.

* Quantum mechanics is the branch of mathematical physics treating atomic and subatomic systems and their interaction with radiation in terms of observable quantities. It is based on the observation that all forms of energy are released in discrete units or bundles called quanta. Quantum theory typically permits only probable or statistical calculation of the observed features of subatomic particles, understood in terms of wave functions.

* The theory of relativity, or relativity theory, is:

*
o A physical theory which is based on two postulates (1) that the speed of light in a vacuum is constant and independent of the source or observer and (2) that it is impossible to determine ones absolute velocity in any inertial systems and which leads to the deduction of the equivalence of mass and energy and of change in mass, dimension, and time with increased velocity — called also special relativity, special theory of relativity;
o An extension of the theory to include gravitation and related acceleration phenomena — called also general relativity, general theory of relativity.

Theory Major s