Branches of physics

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Further information: Classical physics, Modern physics, and Outline of physics § Branches of physics
Domains of major fields of physics

experimentally
test theories of the physical universe. These theories vary in their scope and can be organized into several distinct branches, which are outlined in this article.

Classical mechanics

Main articles: Classical mechanics and Mechanics

Classical mechanics is a model of the

fluids. It is often referred to as "Newtonian mechanics" after Isaac Newton and his laws of motion. It also includes the classical approach as given by Hamiltonian and Lagrange
methods. It deals with the motion of particles and the general system of particles.

There are many branches of classical mechanics, such as:

dynamics, kinematics, continuum mechanics (which includes fluid mechanics), statistical mechanics
, etc.

  • Mechanics: A branch of physics in which we study the object and properties of an object in form of a motion under the action of the force.

Thermodynamics and statistical mechanics

Main articles: Thermodynamics and Statistical mechanics

The first chapter of

existence of atoms, which Feynman considered to be the most compact statement of physics, from which science could easily result even if all other knowledge was lost.[1] By modeling matter as collections of hard spheres, it is possible to describe the kinetic theory of gases
, upon which classical thermodynamics is based.

Thermodynamics studies the effects of changes in

efficiency of early steam engines.[4]

The starting point for most thermodynamic considerations is the

surroundings. A system is composed of particles, whose average motions define its properties, which in turn are related to one another through equations of state. Properties can be combined to express internal energy and thermodynamic potentials, which are useful for determining conditions for equilibrium and spontaneous processes
.

Electromagnetism and photonics

Maxwell's equations of electromagnetism
Main article: Electromagnetism

The study of the behaviors of electrons, electric media, magnets, magnetic fields, and general interactions of light.

See also: Optics

Relativistic mechanics

Main articles: Special relativity and General relativity

The special theory of relativity enjoys a relationship with electromagnetism and mechanics; that is, the

principle of stationary action in mechanics can be used to derive Maxwell's equations,[7][8]
and vice versa.

The theory of special relativity was proposed in 1905 by

laws of physics are invariant in all inertial systems; and (2) that the speed of light in a vacuum is constant and independent of the source or observer. Reconciling the two postulates requires a unification of space and time into the frame-dependent concept of spacetime
.

General relativity is the

gravitation published by Albert Einstein in 1915/16.[9][10] It unifies special relativity, Newton's law of universal gravitation, and the insight that gravitation can be described by the curvature of space and time. In general relativity, the curvature of spacetime is produced by the energy
of matter and radiation.

Quantum mechanics, atomic physics, and molecular physics

Main article: Quantum mechanics
The first few hydrogen atom electron orbitals shown as cross-sections with color-coded probability density
Schrödinger equation of quantum mechanics

Quantum mechanics is the branch of physics treating atomic and subatomic systems and their interaction based on the observation that all forms of energy are released in discrete units or bundles called "quanta". Remarkably, quantum theory typically permits only probable or statistical calculation of the observed features of subatomic particles, understood in terms of wave functions. The Schrödinger equation plays the role in quantum mechanics that Newton's laws and conservation of energy serve in classical mechanics—i.e., it predicts the future behavior of a dynamic system—and is a wave equation that is used to solve for wavefunctions.

For example, the light, or electromagnetic radiation emitted or absorbed by an atom has only certain

frequencies (or wavelengths), as can be seen from the line spectrum associated with the chemical element represented by that atom. The quantum theory shows that those frequencies correspond to definite energies of the light quanta, or photons, and result from the fact that the electrons of the atom can have only certain allowed energy values, or levels; when an electron changes from one allowed level to another, a quantum of energy is emitted or absorbed whose frequency is directly proportional to the energy difference between the two levels. The photoelectric effect
further confirmed the quantization of light.

In 1924,

quantum statistics, quantum electrodynamics, concerned with interactions between charged particles and electromagnetic fields; and its generalization, quantum field theory
.

See also: String theory, Quantum gravity, and Loop quantum gravity

String Theory

A possible candidate for the theory of everything, this theory combines the theory of general relativity and quantum mechanics to make a single theory. This theory can predict about properties of both small and big objects. This theory is currently under the developmental stage.

Optics and acoustics

Main articles:
Optical physics and Optics

Optics is the study of light motions including reflection, refraction, diffraction, and interference.

Acoustics is the branch of physics involving the study of mechanical waves in different mediums.

See also:
Optical instruments

Condensed matter physics

Main article: Condensed matter physics

The study of the physical properties of matter in a condensed phase.

See also: Materials science and Solid-state physics

High-energy particle physics and nuclear physics

Main articles: Particle physics and Nuclear physics

atomic nuclei
.

See also: String theory

Cosmology

Main article: Cosmology

astrophysicists
. It also studies about fictional universes people made, how the universes came to be, and their eventual fate and destruction.

Interdisciplinary fields

To the interdisciplinary fields, which define partially sciences of their own, belong e.g. the

  • agrophysics is a branch of science bordering on agronomy and physics.
  • astrophysics, the physics in the universe, including the properties and interactions of celestial bodies in astronomy.
  • atmospheric physics is the application of physics to the study of the atmosphere.
  • space physics is the study of plasmas as they occur naturally in the Earth's upper atmosphere (aeronomy) and within the Solar System.
  • biophysics, studying the physical interactions of biological processes.
  • chemical physics, the science of physical relations in chemistry.
  • numerical methods
    to physical systems.
  • econophysics, dealing with physical processes and their relations in the science of economy.
  • environmental physics
    , the branch of physics concerned with the measurement and analysis of interactions between organisms and their environment.
  • engineering physics, the combined discipline of physics and engineering.
  • geophysics, the sciences of physical relations on our planet.
  • mathematical physics, mathematics pertaining to physical problems.
  • medical physics, the application of physics in medicine to prevention, diagnosis, and treatment.
  • physical chemistry, dealing with physical processes and their relations in the science of physical chemistry.
  • physical oceanography, is the study of physical conditions and physical processes within the ocean, especially the motions and physical properties of ocean waters.
  • psychophysics, the science of physical relations in psychology.
  • quantum computing, the study of quantum-mechanical computation systems.
  • sociophysics
    or social physics, is a field of science which uses mathematical tools inspired by physics to understand the behavior of human crowds

Summary

The table below lists the core theories along with many of the concepts they employ.

Theory Major subtopics Concepts
Classical mechanics
dynamics, chaos theory, acoustics, fluid dynamics, continuum mechanics
hydraulic
Electromagnetism
electrodynamics, electricity, magnetism, magnetostatics, Maxwell's equations, optics
magnetic permeability
Thermodynamics and statistical mechanics Heat engine, kinetic theory
thermodynamic system, viscosity, volume, work, granular material
Quantum mechanics
scattering theory, Schrödinger equation, quantum field theory, quantum statistical mechanics
Heisenberg uncertainty principle
Relativity Special relativity, general relativity, Einstein field equations
special principle of relativity, speed of light, stress–energy tensor, time dilation, twin paradox, world line

References

  1. atomic hypothesis
    , as his most compact statement of all scientific knowledge: "If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations ..., what statement would contain the most information in the fewest words? I believe it is ... that all things are made up of atoms – little particles that move around in perpetual motion, attracting each other when they are a little distance apart, but repelling upon being squeezed into one another. ..." vol. I p. I–2
  2. ISBN 978-0-19-856552-9
    .
  3. ISBN 978-0-7607-4616-5
    .
  4. ISBN 978-0-486-59065-3.[clarification needed
    ]
  5. ISBN 978-0-486-63277-3
    .
  6. ISBN 978-0-7484-0569-5
    .
  7. ISBN 0-08-016019-0
    )
  8. ISBN 0-7167-1823-5
  9. ^ Einstein, Albert (November 25, 1915). "Die Feldgleichungen der Gravitation". Sitzungsberichte der Preussischen Akademie der Wissenschaften zu Berlin: 844–847. Archived from the original on 2016-10-27. Retrieved 2006-09-12.
  10. doi:10.1002/andp.19163540702. Archived from the original
    (PDF) on 2006-08-29. Retrieved 2006-09-03.
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