Physics

Physics Branches
Here is a list of main branches of physics, along with a summary of what is studied in that particular branch. Every branch of physics is further divided into smaller sub-branches. As explained before, every one of these branches except mathematical physics, has an experimental and theoretical sub-division. The classification of these branches of physics is artificial and these branches overlap onto each other to create further specialized fields.

Classical Mechanics
This is the oldest branch of physics which analytically describes motion of all objects on the macroscopic scales. It describes everything from why large objects like balls bounce, why pendulum swings to why planets revolve around the Sun! It describes 'mechanics' of all kinds on the large scale and its classical, because it cannot explain motion at atomic level. Fluid mechanics is one specialized sub-branch of classical mechanics, which describes the physics of all types of fluids.

Mathematical Physics
This is the branch of physics, which gives theoretical physics its tools of analysis. Mathematics is the language of nature and therefore if one wants to understand nature, one must understand mathematics. Mathematics brings precision to physics. It is the branch which is an overlap of pure mathematics and physics. Mathematical physics techniques form the toolbox of a physicist. Just like a workman must use the right kind of tools to get his job done, so must a physicist use the right mathematical tools to solve a problem! The more and more deeply we explore nature, every new law discovered can only be expressed in a new form of mathematics.

Classical Electrodynamics
This field is the most broadly applied of all the branches of physics. Classical electrodynamics is based on Maxwell's laws of electromagnetism, which describes all kinds of electromagnetic phenomena from atomic to global scales. It is the theoretical basis of optics, telecommunication and many other sub-fields. Its domain extends over all of nature, as the 'Electromagnetic Force' is all pervading and we live in an electromagnetic world.

Quantum Mechanics
This branch describes a new kind of mechanics, which can explain phenomena at the sub-atomic level, which classical mechanics fails to describe. It provides the clearest picture of nature at the sub-atomic scales. Quantum physics, is based on the principle of uncertainty, and predicts all phenomena in terms of probabilities. It describes a weird sub-atomic world, which is totally different from the world at macroscopic scales. Studying quantum physics requires quite a bit of mathematical expertise and it is the theoretical basis of all branches of physics, that describe phenomena at atomic or sub-atomic scales. For more on this read, 'Basics of Quantum Mechanics for Dummies'.

Thermodynamics and Statistical Mechanics
Thermodynamics and statistical physics is one of the core branches of physics, which gives a theoretical mechanism to describe the motion of and phenomena in multi-particle systems. Even though a single particle motion can be analyzed by quantum mechanics, it cannot describe multi-particle systems analytically, as the variables of calculation there are too many. So, a statistical approach is needed that describes motion of matter in bulk. Thermodynamics is a predecessor of statistical mechanics. Statistical mechanics combined with quantum mechanics, forms quantum statistical mechanics.

Condensed Matter Physics
Condensed Matter Physics is a sub-branch of quantum physics and statistical mechanics, which describes all phenomena that occur in matter, which is in condensed form. This includes everything from liquids, solid and gases. The physics of semiconductor devices, which make today's age of information technology possible, is a result of research developments in condensed matter physics. It describes all phenomena in bulk matter like ferromagnetism, superfluidity and superconductivity.

Nuclear Physics
Nuclear physics describes all the phenomena that occur at the level of the atomic nucleus. It deals with and explains phenomena like radioactivity, nuclear fission and nuclear fusion. Developments in nuclear physics led to the production of nuclear weapons like the atom bomb, the Hydrogen bomb and made nuclear energy source available to mankind. For more on this, read 'List of Radioactive Elements'.

Quantum Field theory
This is the physics which describes the physics of particles, which are very small and very fast. It is also known as particle physics. It is based on the three theoretical foundations of quantum mechanics, special theory of relativity and the concept of fields. It is based on the unification of all these three foundations and it describes the physics of fundamental particles of matter. It is one of the most difficult branches of physics, which describe the ultimate building blocks of nature.

Non-Linear Dynamics
This is a sub-field of classical mechanics, which solves the problems on macroscopic scales, which cannot be solved by classical mechanics. It is an advanced branch of mathematics, which attempts to solve non-linear differential equations of motion, which are not amenable to a solution by conventional techniques. A greater part of it is also known as 'Chaos Theory', which delves in to the organized chaos that exists in the macroscopic world. It is the most happening branch of physics currently. For more on this read, 'An Introduction to Chaos Theory'.

Astronomy and Astrophysics
Astronomy is the observational study of the universe in all its manifestations and astrophysics (a confluence of all branches of physics), is the theoretical basis, which can explain all those phenomena. It is the most all encompassing of all the branches of physics, which has a singular goal of explaining every phenomenon that occurs in the universe.

General Theory of Relativity and Cosmology
The general theory of relativity is the correct theory, which describes gravitation at all scales. It interprets gravity not as a force, but as a consequence of the curvature of space-time. Space around massive objects actually gets warped and bent. Gravity is the result of this warping of space time. Special relativity unifies space and time in to 'Spacetime' and general relativity makes 'Spacetime' interact with matter. How much space warps, depends on the content of matter and energy in it. In simple words, general relativity is described by, 'Matter tells space how to bend, space tells matter how to move!' For more read 'Does the Fourth(4th) Dimension of Time Exist'.

Physics is the study of matter, energy and the interactions of the two.

Physics can be divided into two main branches: mechanics (the study of the behavior of forces and objects acting due to those forces); and, electricity and magnetism (which delves into the science of the atom).


The fundamental branches of physics:

classical mechanics
electromagnetism (including optics)
relativity
thermodynamics
quantum mechanics
astronomy
electromagnetism


Some of the more popular or modern branches of physics:

Astro and space physics (study of stars, planets, black holes, etc.)
geophysics (study of like earthquakes and plate tectonics)
nuclear physics
particle physics
medical physics
biophysics, and quantum physics, which is mostly theoretical

Classical Physics :

Mechanics
Acoustics
Thermics
Electromagnetics
Optics

Modern Physics:

Relativistic Mechanics
Quantum Mechanics
Quantum Acoustics
Quantum Thermodynamics
Quantum Electrodynamics
Quantum Optics

Applied Physics :

Cosmophysics
Astrophysics
Planetophysics
Geophysics
Molecular Physics
Atomic Physics
Nuclear Physics
Particle Physics
Solid-State Physics
Fluid Physics
Plasma Physics
Phononics
Thermal Physics
EM Instrumentation
Electronics
Photonics

Physicist

Famous Physicists

Classical Period

William Gilbert
1544-1603
English
hypothesized that the Earth is a giant magnet

Galileo Galilei
1564-1642
Italian
performed fundamental observations, experiments, and mathematical analyses in astronomy and physics; discovered mountains and craters on the moon, the phases of Venus, and the four largest satellites of Jupiter: Io, Europa, Callisto, and Ganymede

Willebrod Snell
1580-1626
Dutch
discovered law of refraction (Snell's law)

Blaise Pascal
1623-1662
French discovered that pressure applied to an enclosed fluid is transmitted undiminished to every part of the fluid and to the walls of its container (Pascal's principle)

Christiaan Huygens
1629-1695
Dutch
proposed a simple geometrical wave theory of light, now known as ``Huygen's principle''; pioneered use of the pendulum in clocks

Robert Hooke
1635-1703
English
discovered Hooke's law of elasticity

Sir Isaac Newton
1643-1727
English
developed theories of gravitation and mechanics, and invented differential calculus

Daniel Bernoulli
1700-1782
Swiss
developed the fundamental relationship of fluid flow now known as Bernoulli's principle

Benjamin Franklin
1706-1790
American
the first American physicist; characterized two kinds of electric charge, which he named ``positive'' and ``negative''

Leonard Euler
1707-1783
Swiss
made fundamental contributions to fluid dynamics, lunar orbit theory (tides), and mechanics; also contributed prolifically to all areas of classical mathematics

Henry Cavendish
1731-1810
British
discovered and studied hydrogen; first to measure Newton's gravitational constant; calculated mass and mean density of Earth

Charles Augustin de Coulomb
1736-1806
French
experiments on elasticity, electricity, and magnetism; established experimentally nature of the force between two charges

Joseph-Louis Lagrange
1736-1813
French
developed new methods of analytical mechanics

James Watt
1736-1819
Scottish
invented the modern condensing steam engine and a centrifugal governor

Count Alessandro Volta
1745-1827
Italian
pioneer in study of electricity; invented the first electric battery

Joseph Fourier
1768-1830
French
established the differential equation governing heat diffusion and solved it by devising an infinite series of sines and cosines capable of approximating a wide variety of functions

Thomas Young
1773-1829
British
studied light and color; known for his double-slit experiment that demonstrated the wave nature of light

Jean-Babtiste Biot
1774-1862
French
studied polarization of light; co-discovered that intensity of magnetic field set up by a current flowing through a wire varies inversely with the distance from the wire

André Marie Ampère
1775-1836
French
father of electrodynamics

Amadeo Avogadro
1776-1856
Italian
developed hypothesis that all gases at same volume, pressure, and temperature contain same number of atoms

Johann Carl Friedrich Gauss
1777-1855
German formulated separate electrostatic and electrodynamical laws, including ``Gauss' law''; contributed to development of number theory, differential geometry, potential theory, theory of terrestrial magnetism, and methods of calculating planetary orbits

Hans Christian Oersted
1777-1851
Danish
discovered that a current in a wire can produce magnetic effects

Sir David Brewster
1781-1868
English
deduced ``Brewster's law'' giving the angle of incidence that produces reflected light which is completely polarized; invented the kaleidoscope and the stereoscope, and improved the spectroscope

Augustin-Jean Fresnel
1788-1827
French
studied transverse nature of light waves

Georg Ohm
1789-1854
German
discovered that current flow is proportional to potential difference and inversely proportional to resistance (Ohm's law)

Michael Faraday
1791-1867
English
discovered electromagnetic induction and devised first electrical transformer

Felix Savart
1791-1841
French
co-discovered that intensity of magnetic field set up by a current flowing through a wire varies inversely with the distance from the wire

Sadi Carnot
1796-1832
French
founded the science of thermodynamics

Joseph Henry
1797-1878
American
performed extensive fundamental studies of electromagnetic phenomena; devised first practical electric motor

Christian Doppler
1803-1853
Austrian
experimented with sound waves; derived an expression for the apparent change in wavelength of a wave due to relative motion between the source and observer

Wilhelm E. Weber
1804-1891
German
developed sensitive magnetometers; worked in electrodynamics and the electrical structure of matter

Sir William Hamilton
1805-1865
Irish
developed the principle of least action and the Hamiltonian form of classical mechanics

James Prescott Joule
1818-1889
British
discovered mechanical equivalent of heat

Armand-Hippolyte-Louis Fizeau
1819-1896
French
made the first terrestrial measurement of the speed of light; invented one of the first interferometers; took the first pictures of the Sun on daguerreotypes; argued that the Doppler effect with respect to sound should also apply to any wave motion, particularly that of light

Jean-Bernard-Léon Foucault
1819-1868
French
accurately measured speed of light; invented the gyroscope; demonstrated the Earth's rotation

Sir George Gabriel Stokes
1819-1903
British
described the motion of viscous fluids by independently discovering the Navier-Stokes equations of fluid mechanics (or hydrodynamics); developed Stokes theorem by which certain surface integrals may be reduced to line integrals; discovered fluorescence

Hermann von Helmholtz
1821-1894
German
developed first law of thermodynamics, a statement of conservation of energy

Rudolf Clausius
1822-1888
German
developed second law of thermodynamics, a statement that the entropy of the Universe always increases

Lord Kelvin
(born William Thomson)
1824-1907
British
proposed absolute temperature scale, of essence to development of thermodynamics

Gustav Kirchhoff
1824-1887
German
developed three laws of spectral analysis and three rules of electric circuit analysis; also contributed to optics

Johann Balmer
1825-1898
Swiss
developed empirical formula to describe hydrogen spectrum

Sir Joseph Wilson Swan
1828-1914
British
developed a carbon-filament incandescent light; patented the carbon process for printing photographs in permanent pigment

James Clerk Maxwell
1831-1879
Scottish
propounded the theory of electromagnetism; developed the kinetic theory of gases

Josef Stefan
1835-1893
Austrian
studied blackbody radiation

Ernst Mach
1838-1916
Austrian
studied conditions that occur when an object moves through a fluid at high speed (the ``Mach number'' gives the ratio of the speed of the object to the speed of sound in the fluid); proposed ``Mach's principle,'' which states that the inertia of an object is due to the interaction between the object and the rest of the universe

Josiah Gibbs
1839-1903
American
developed chemical thermodynamics; introduced concepts of free energy and chemical potential

James Dewar
1842-1923
British
liquified nitrogen and invented the Dewar flask, which is critical for low-temperature work

Osborne Reynolds
1842-1912
British
contributed to the fields of hydraulics and hydrodynamics; developed mathematical framework for turbulence and introduced the ``Reynolds number,'' which provides a criterion for dynamic similarity and correct modeling in many fluid-flow experiments

Ludwig Boltzmann
1844-1906
Austrian
developed statistical mechanics and applied it to kinetic theory of gases

Roland Eötvös
1848-1919
Hungarian
demonstrated equivalence of gravitational and inertial mass

Oliver Heaviside
1850-1925
English
contributed to the development of electromagnetism; introduced operational calculus and invented the modern notation for vector calculus; predicted existence of the Heaviside layer (a layer of the Earth's ionosphere)

George Francis FitzGerald
1851-1901
Irish
hypothesized foreshortening of moving bodies (Lorentz-FitzGerald contraction) to explain the result of the Michelson-Morley experiment

John Henry Poynting
1852-1914
British
demonstrated that the energy flow of electromagnetic waves could be calculated by an equation (now called Poynting's vector)

Henri Poincaré 1854-1912
French
founded qualitative dynamics (the mathematical theory of dynamical systems); created topology; contributed to solution of the three-body problem; first described many properties of deterministic chaos; contributed to the development of special relativity

Janne Rydberg
1854-1919
Swedish
analyzed the spectra of many elements; discovered many line series were described by a formula that depended on a universal constant (the Rydberg constant)

Edwin H. Hall
1855-1938
American
discovered the ``Hall effect,'' which occurs when charge carriers moving through a material are deflected because of an applied magnetic field - the deflection results in a potential difference across the side of the material that is transverse to both the magnetic field and the current direction

Heinrich Hertz
1857-1894
German
worked on electromagnetic phenomena; discovered radio waves and the photoelectric effect

Nikola Tesla
1857-1943
Serbian-born American
created alternating current