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Physics is a science. Physics is concerned with the discovery and understanding of the fundamental laws which govern matter, energy, space and time. 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. Chemistry concerning the electro-chemical interactions of substances overlaps with physics.

Introduction to physics.

Physics experiment: Thousands of particles explode from the collision point of two relativistic (100 GeV per nucleon) gold ions in the STAR detector of the relativistic heavy ion collider; an experiment done in order to investigate the properties of a quark gluon plasma such as the one thought to exist in the ultrahot first few microseconds after the Big Bang.

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.

Connected studies of physics.

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.

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.

Central theories of physics.

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:.
  • 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;.
  • An extension of the theory to include gravitation and related acceleration phenomena - called also General relativity, general theory of relativity.
TheoryMajor subtopicsConcepts
classical mechanics Newton's laws of motion, Lagrangian mechanics, Hamiltonian mechanics, Kinematics, Statics, Dynamics, Chaos theory, Acoustics, Fluid dynamics, Continuum mechanics density, dimension, Gravity, space, time, motion, Length, Position, velocity, acceleration, mass, Momentum, Force, energy, angular momentum, Torque, Conservation law, Harmonic oscillator, Wave, Work, Power
electromagnetism electrostatics, electrodynamics, electricity, magnetism, Maxwell's equations, Optics Capacitance, electric charge, Current, Electrical conductivity, electric field, Electric permittivity, Electric potential, Electrical resistance, Electromagnetic field, Electromagnetic induction, electromagnetic radiation, Gaussian surface, magnetic field, Magnetic flux, magnetic monopole, Magnetic permeability
Thermodynamics and Statistical mechanics Heat engine, Kinetic theory Boltzmann's constant, Conjugate variables, Enthalpy, Entropy, Equation of state, Equipartition theorem, Free energy, Heat, Ideal gas law, Internal energy, Laws of thermodynamics, Irreversible process, Ising model, Mechanical action, Partition function, pressure, Reversible process, Spontaneous process, State function, Statistical ensemble, temperature, thermodynamic equilibrium, Thermodynamic potential, Thermodynamic processes, Thermodynamic state, Thermodynamic system, Viscosity, Volume, Work
quantum mechanics PAth integral formulation, Scattering theory, Schrödinger equation, Quantum field theory, Quantum statistical mechanics Adiabatic approximation, Blackbody radiation, Correspondence principle, Free particle, Hamiltonian, Hilbert space, Identical particles, Matrix Mechanics, Planck's constant, Observer effect, Operators, quanta, Quantization, Quantum entanglement, Quantum harmonic oscillator, Quantum number, Quantum tunneling, Schrödinger's cat, Dirac equation, Spin, Wavefunction, Wave mechanics, Wave-particle duality, Zero-point energy, Pauli Exclusion Principle, Heisenberg uncertainty principle
Theory of Relativity special relativity, Einstein field equations Covariance, Einstein manifold, Equivalence principle, Four-momentum, Four-vector, General principle of relativity, Geodesic motion, gravity, Gravitoelectromagnetism>, inertial frame of reference, Invariance, Length contraction, Lorentzian manifold, Lorentz transformation, Mass-energy equivalence, Metric, Minkowski diagram, Minkowski space, Principle of Relativity, Proper length, Proper time, Reference frame, Rest energy, rest mass, Relativity of simultaneity, Spacetime, Special principle of relativity, speed of light, stress-energy tensor, Time dilation, Twin paradox, World line

Major fields of physics.

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. A magnet levitating above a high-temperature superconductor (with boiling liquid nitrogen underneath), demonstrating the Meissner effect, is a phenomenon of importance to the field of condensed matter physics.
  • 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.

Many fields and subfields of physics are listed in the table below.

FieldSubfieldsMajor theoriesConcepts
Astrophysics cosmology, Gravitation physics, High-energy astrophysics, Planetary astrophysics, Plasma physics, Space physics, Stellar astrophysics Big Bang, Lambda-CDM model, cosmic inflation, General relativity, Law of universal gravitation black hole, Cosmic background radiation, Cosmic string, Cosmos, Dark energy, Dark matter, Galaxy, gravity, Gravitational radiation, gravitational singularity, planet, Solar System, star, supernova, universe
atomic, molecular, and optical physics Atomic physics, Molecular physics, Atomic and Molecular astrophysics, Chemical physics, Optics, Photonics Quantum optics, Quantum chemistry, Quantum information science atom, Molecule, Diffraction, electromagnetic radiation, laser, Polarization, Spectral line, Casimir effect
Particle physics Nuclear physics, Nuclear astrophysics, Particle astrophysics, Particle physics phenomenology Standard Model, Quantum field theory, Quantum chromodynamics, Electroweak theory, Effective field theory, Lattice field theory, Lattice gauge theory, gauge theory, supersymmetry, Grand unification theory, superstring theory, M-Theory Fundamental force ( gravitational, electromagnetic, weak, strong), Elementary particle, Spin, antimatter, Spontaneous symmetry breaking, Brane, String, Quantum gravity, Theory of everything, Vacuum energy
condensed matter physics solid state physics, High pressure physics, Low-temperature physics, Nanoscale and Mesoscopic physics, Polymer physics BCS theory, Bloch wave, Fermi gas, Fermi liquid, Many-body theory Phases (gas, liquid, solid, Bose-Einstein condensate, superconductor, superfluid), Electrical conduction, magnetism, Self-organization, Spin, Spontaneous symmetry breaking

Classical, quantum and modern physics.

Since the construction of quantum mechanics in the early twentieth century, it generally became evident to the physical community that it would be preferable for many known descriptions of nature to be quantized, that is, to follow the postulates of quantum mechanics. To this effect, all results that were not quantized are called classical: this includes the Special Theory and General Theory of Relativity. Simply because a result is classical does not mean that it was discovered before the advent of quantum mechanics. Classical theories are, generally, much easier to work with and much research is still being conducted on them without the express aim of quantization. However, there exist problems in physics in which classical and quantum aspects must be combined to attain some approximation or limit that may acquire several forms as the passage from classical to quantum mechanics is often difficult - such problems are termed semiclassical.

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).

Theoretical and experimental physics.

The culture of physics research differs from the other sciences in the separation of theory and experiment. 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 biochemistry Linus Pauling) have also been experimentalists, though this is changing as of late.

Roughly speaking, theorists seek to develop through abstractions and mathematical models theories that can both describe and interpret existing experimental results and successfully predict future results, while experimentalists devise and perform experiments to explore new phenomena and test theoretical predictions. Although theory and experiment are developed separately, they are strongly dependent on each other. However, theoretical research in physics may further be considered to draw from mathematical physics and computational physics in addition to experimentation. 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.

Discredited theories of physics.

Scientific theories sometimes end up being discredited or superseded. In some of these cases the theory was announced prematurely and gained press attention before being discredited. Other times an established theory is overthrown and a new one erected in its place. Some famous examples are:

  • Cold fusion - Announced in a press conference in 1989 but never confirmed.
  • Dynamic theory of gravity - Announced in a press release by Nikola Tesla in 1937 but never published.
  • steady state theory - An established theory of cosmology in the early and middle 20th century, made obsolete by the success of Big Bang theory.
  • Luminiferous aether - An established theory in the late 19th century, which was contradicted by observations and made "superfluous" by relativity.
  • Phlogiston theory - An established theory of the 18th century that attributed combustion to the liberation of phlogiston from a material.

Physics: Phenomenology.

Phenomenology is intermediate between experiment and theory. It is more abstract and includes more logical steps than experiment, but is more directly tied to experiment than theory. The boundaries between theory and phenomenology, and between phenomenology and experiment, are somewhat fuzzy and to some extent depend on the understanding and intuition of the scientist describing these. An example is Einstein's 1905 paper on the photoelectric effect, "On a Heuristic Viewpoint Concerning the Production and Transformation of Light".

Applied physics.

Applied physics is physics that is intended for a particular technological or practical use, as for example in Engineering, as opposed to basic research. This approach is similar to that of applied mathematics. Applied physics is rooted in the fundamental truths and basic concepts of the physical sciences but is concerned with the utilization of scientific principles in practical devices and systems, and in the application of physics in other areas of science. "Applied" is distinguished from "pure" by a subtle combination of factors such as the motivation and attitude of researchers and the nature of the relationship to the technology or science that may be affected by the work.

Branches of Applied Physics
Accelerator physics, Acoustics, Agrophysics, Biophysics, Chemical physics, Communication Physics, Econophysics, Engineering physics, Fluid dynamics, Geophysics, Materials physics, Medical physics, Nanotechnology, Optics, Optoelectronics, Photovoltaics, Physical chemistry, Physics of computation, plasma physics, Solid-state devices, Quantum chemistry, Quantum electronics, Quantum information science, Vehicle dynamics

History of physics. Famous physicists, Nobel Prize in physics.

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. The character of the universe was also a mystery, for instance 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 first 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 Dignaga and Dharmakirti; the optical theory of Muslim scientist Ibn al-Haitham (Alhazen); the Astrolabe invented by the Persian astronomer Muhammad al-Fazari; and the significant flaws in the Ptolemaic system pointed out by Persian scientist Nasir al-Din Tusi.

As the influence of the Arab Empire 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. This eventually led to the scientific revolution which culminated with the publication of the Philosophiae Naturalis Principia Mathematica in 1687 by the mathematician, physicist, alchemist and inventor Sir Isaac Newton (1643-1727).

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.

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.

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.

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.

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.

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, which proved to be the opening argument in the edifice that would become quantum mechanics. By introducing discrete energy levels, Planck, Einstein, Niels Bohr, and others developed quantum theories to explain various anomalous experimental results. Quantum mechanics was formulated in 1925 by Heisenberg and in 1926 by Schrödinger and Paul Dirac, in two different ways that both 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 Schrödinger, 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.

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 (Yang, Mills 1954). 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 Felix 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.

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.

Future directions of physics.

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 prophesied the success of the theory of quantum electrodynamics and the near-stagnant progress in the study of turbulence:

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.

Notes about physics.

    "physical science - Britannica Concise" (all physical sciences), Britannica Concise, 2006, Concise.Britannica.com webpage: CBritannica-phys-science.
  • 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.

Further reading

Popular reading

  • Coward, David (1988). An Advanced Guide to Physics. Bantam. ISBN 0-681-08016-X.
  • Feynman, Richard (1994). Character of Physical Law. Random House. ISBN 0-679-60127-9.
  • Greene, Brian (2000). The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory. Vintage. ISBN 0-375-70811-1.
  • Kaku, Michio (1995). Hyperspace: A Scientific Odyssey Through Parallel Universes, Time Warps, and the 10th Dimension. Anchor. ISBN 0-385-47705-8.
  • Leggett, Anthony (1988). The Problems of Physics. Oxford University Press. ISBN 0-19-289186-3.
  • Penrose, Roger (2004). Road to Reality: A Complete Guide to the Laws of the Universe. Knopf. ISBN 0-679-45443-8.
  • Rogers, Eric (1960). Physics for the Inquiring Mind: The Methods, Nature, and Philosophy of Physical Science. Princeton University Press. ISBN 0-691-08016-X.
  • Walker, Jearl (1977). The Flying Circus of Physics. Wiley. ISBN 0-471-02984-X.

University-level textbooks

Survey texts

  • Crowell, Benjamin (2001). Simple Nature.
  • Feynman, Richard; Leighton, Robert; Sands, Matthew (1989). Feynman Lectures on Physics. Addison-Wesley. ISBN 0-201-51003-0.
  • Feynman, Richard. Exercises for Feynman Lectures Volumes 1-3. Caltech. ISBN 2-35648-789-1.
  • Knight, Randall (2004). Physics for Scientists and Engineers: A Strategic Approach. Benjamin Cummings. ISBN 0-8053-8685-8.
  • Halliday, David; Resnick, Robert; Walker, Jearl. Fundamentals of Physics 7th ed. ISBN 0-471-21643-7.
  • Hewitt, Paul (2001). Conceptual Physics with Practicing Physics Workbook (9th ed.). Addison Wesley. ISBN 0-321-05202-1.
  • Giancoli, Douglas (2005). Physics: Principles with Applications (6th ed.). Prentice Hall. ISBN 0-13-060620-0.
  • Serway, Raymond A.; Jewett, John W. (2004). Physics for Scientists and Engineers (6th ed.). Brooks/Cole. ISBN 0-534-40842-7.
  • Tipler, Paul (2004). Physics for Scientists and Engineers: Mechanics, Oscillations and Waves, Thermodynamics (5th ed.). W. H. Freeman. ISBN 0-7167-0809-4.
  • Tipler, Paul (2004). Physics for Scientists and Engineers: Electricity, Magnetism, Light, and Elementary Modern Physics (5th ed.). W. H. Freeman. ISBN 0-7167-0810-8.
  • Wilson, Jerry; Buffa, Anthony (2002). College Physics (5th ed.). Prentice Hall. ISBN 0-13-067644-6.
  • Schiller, Christoph (2005). Motion Mountain: The Free Physics Textbook.
  • H. C. Verma (2005). Concepts of Physics. Bharti Bhavan. ISBN 81-7709-187-5.

Undergraduate texts on specific topics

  • Thornton, Stephen T.; Marion, Jerry B. (2003). Classical Dynamics of Particles and Systems (5th ed.). Brooks Cole. ISBN 0-534-40896-6.
  • Griffiths, David J. (1998). Introduction to Electrodynamics (3rd ed.). Prentice Hall. ISBN 0-13-805326-X.
  • Wangsness, Roald K. (1986). Electromagnetic Fields (2nd ed.). Wiley. ISBN 0-471-81186-6.
  • Fowles, Grant R. (1989). Introduction to Modern Optics. Dover Publications. ISBN 0-486-65957-7.
  • Hecht, Eugene (2001). Optics (4th ed.). Pearson Education. ISBN 0-8053-8566-5.
  • Schroeder, Daniel V. (1999). An Introduction to Thermal Physics. Addison Wesley. ISBN 0-201-38027-7.
  • Kroemer, Herbert; Kittel, Charles (1980). Thermal Physics (2nd ed.). W. H. Freeman Company. ISBN 0-7167-1088-9.
  • Griffiths, David J. (2004). Introduction to Quantum Mechanics (2nd ed.). Prentice Hall. ISBN 0-13-805326-X.
  • Liboff, Richard L. (2002). Introductory Quantum Mechanics. Addison-Wesley. ISBN 0-8053-8714-5.
  • Bohm, David (1989). Quantum Theory. Dover Publications. ISBN 0-486-65969-0.
  • Eisberg, Robert; Resnick, Robert (1985). Quantum Physics of Atoms, Molecules, Solids, Nuclei, and Particles (2nd ed.). Wiley. ISBN 0-471-87373-X.
  • Taylor, Edwin F.; Wheeler, John Archibald (1992). Spacetime Physics: Introduction to Special Relativity (2nd ed.). W.H. Freeman. ISBN 0-7167-2327-1.
  • Taylor, Edwin F.; Wheeler, John Archibald (2000). Exploring Black Holes: Introduction to General Relativity. Addison Wesley. ISBN 0-201-38423-X.
  • Schutz, Bernard F. (1984). A First Course in General Relativity. Cambridge University Press. ISBN 0-521-27703-5.
  • Bergmann, Peter G. (1976). Introduction to the Theory of Relativity. Dover Publications. ISBN 0-486-63282-2.
  • Tipler, Paul; Llewellyn, Ralph (2002). Modern Physics (4th ed.). W. H. Freeman. ISBN 0-7167-4345-0.
  • Griffiths, David J. (1987). Introduction to Elementary Particles. Wiley, John & Sons, Inc. ISBN 0-471-60386-4.
  • Perkins, Donald H. (1999). Introduction to High Energy Physics. Cambridge University Press. ISBN 0-521-62196-8.
  • Povh, Bogdan (1995). Particles and Nuclei: An Introduction to the Physical Concepts. Springer-Verlag. ISBN 0-387-59439-6.
  • Menzel, Donald Howard (1961). Mathematical Physics. Dover Publishications. ISBN 0-486-60056-4.
  • Joos, Georg; Freeman, Ira M. (1987). Theoretical Physics. Dover Publications. ISBN 0-486-65227-0.

Graduate texts

  • Landau, L. D.; Lifshitz, E. M. (1976). Course of Theoretical Physics. Butterworth-Heinemann. ISBN 0-7506-2896-0.
  • Morse, Philip; Feshbach, Herman (2005). Methods of Theoretical Physics. Feshbach Publishing. ISBN 0-9762021-2-3.
  • Arfken, George B.; Weber, Hans J. (2000). Mathematical Methods for Physicists (5th ed.). Academic Press. ISBN 0-12-059825-6.
  • Goldstein, Herbert (2002). Classical Mechanics. Addison Wesley. ISBN 0-201-65702-3.
  • Jackson, John D. (1998). Classical Electrodynamics (3rd ed.). Wiley. ISBN 0-471-30932-X.
  • Landau, L. D.; Lifshitz, E. M. (1972). Mechanics and Electrodynamics, Vol. 1. Franklin Book Company, Inc. ISBN 0-08-016739-X.
  • Huang, Kerson (1990). Statistical Mechanics. Wiley, John & Sons, Inc. ISBN 0-471-81518-7.
  • Merzbacher, Eugen (1998). Quantum Mechanics. Wiley, John & Sons, Inc. ISBN 0-471-88702-1.
  • Peskin, Michael E.; Schroeder, Daniel V. (1994). Introduction to Quantum Field Theory. Perseus Publishing. ISBN 0-201-50397-2.
  • Thorne, Kip S.; Misner, Charles W.; Wheeler, John Archibald (1973). Gravitation. W.H. Freeman. ISBN 0-7167-0344-0.
  • Wald, Robert M. (1984). General Relativity. University of Chicago Press. ISBN 0-226-87033-2.
  • Weinberg, Steven (1972). Gravitation and Cosmology: Principles and Applications of the General Theory of Relativity. John Wiley & Sons. ISBN 0-471-92567-5.


  • Cropper, William H. (2004). Great Physicists: The Life and Times of Leading Physicists from Galileo to Hawking. Oxford University Press. ISBN 0-19-517324-4.
  • Gamow, George (1988). The Great Physicists from Galileo to Einstein. Dover Publications. ISBN 0-486-25767-3.
  • Heilbron, John L. (2005). The Oxford Guide to the History of Physics and Astronomy. Oxford University Press. ISBN 0-19-517198-5.
  • Weaver, Jefferson H. (editor) (1987). The World of Physics. Simon and Schuster. ISBN 0-671-49931-9. A selection of 56 articles, written by physicists. Commentaries and notes by Lloyd Motz and Dale McAdoo.

More About Physics.

Have the Constants of Physics Remained Unchanged?

Dec 20, 2005 - The physical constants of the Universe are thought to have remained unchanged since the Big Bang; many predictions made by cosmologists depend on it. An international team of researchers are using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT) to see if things really have gone on unchanged for billions of years. They're looking to measure two universal constants: the ratio of mass between protons and electrons, and something called the fine structure constant.

Questions for Dr. Lawrence M. Krauss

Nov 25, 2005 - Theoretical physicist Dr. Lawrence M. Krauss from Case Western University and author of Hiding in the Mirror: The Mysterious Allure of Extra Dimensions, from Plato to String Theory and Beyond has agreed to answer questions from the Bad Astronomy/Universe Today forum. If you've got puzzling questions about physics, multiple dimensions, or any of his books, and post a question. We'll gather up the best questions and pass them along to Dr. Krauss to answer. I'll post his answers back in Universe Today when I get them.

Gravity Probe B Will Tell Us If Einstein Was Right

Nov 17, 2005 - NASA/Stanford's Gravity Probe B spacecraft recently wrapped up a year of gathering data about the Earth's gravity field. If Einstein was correct, the Earth's rotation should twist up our planet's gravity field like a vortex. Scientists at NASA and Stanford are now analyzing the mountains of data sent back by the spacecraft to detect any shift in its orientation, which would indicate this vortex of gravity.

Our Universe Favours Three and Seven Dimensions

Sep 28, 2005 - Scientists working to understand the nature of the Universe have developed some interesting theories that propose we have many more dimensions curled up inside the three we're comfortable with. A pair of researchers have done the math to calculate how the Universe could shape up after the Big Bang, and found that it favours three and seven dimensions. In a seven dimension Universe, gravity would diminish greatly with distance, and planets would have difficulty forming stable orbits around stars.

Quark-Gluon Plasma Created

Aug 1, 2005 - Physicists have used the Brookhaven National Laboratory's Relativistic Heavy Ion Collider to create quark-gluon plasma; a mysterious form of matter that was probably present in the first moments after the Big Bang. The team created it by smashing the nuclei of gold atoms together at relativistic speeds. The resulting explosion of particles lasted just 10-20 seconds. Astronomers think that large neutron stars might go into a quark-gluon phase before they collapse into black holes.

New Form of Matter Created

Jun 22, 2005 - Physicists at MIT have successfully created a new form of matter in their laboratory; a gas that shows superfluidity at higher temperatures. Superfluid gasses, which can flow without resistance, have been created before, but only at very cold temperatures just above Absolute Zero. Matter like this could exist in the Universe's most extreme places, like at the heart of black holes, neutron stars, or in the early stages of the Big Bang.

Fundamental Aspect of the Universe has Remained Unchanged

Apr 18, 2005 - Researchers from UC Berkeley have looked into the past to confirm that a fundamental aspect of the Universe - the fine structure constant, or alpha - has remain unchanged for at least 7 billion years. This constant shows up in many formulae dealing with electricity and magnetism, and helps describe how radiation is emitted by atoms. This conflicts with a recent announcement from Australian researchers that described a change in alpha over time.

Universal Constant Might Not Be Constant

Apr 11, 2005 - An international researchers has found evidence that a universal constant in nature which governs the strength of the molecular bonds between atoms - called "alpha" - might have changed over time. The strength of alpha is very important, and life couldn't exist if it was much different from its current value. The team examined the light from distant quasars billions of light-years away, and measured the unique fingerprint of its light being absorbed by clouds of gas. They compared this fingerprint to known values here on Earth to measure the difference.

Detector Ready to Receive Beam of Neutrinos

Mar 5, 2005 - Scientists have begun firing a beam of neutrinos through the Earth to a target 735 km (456 miles) away. This experiment will help the team understand how neutrinos can pass through tremendous amounts of matter, but barely interact. And if they're lucky, they'll catch the particles as they morph into different varieties: electron, muon and tau. One detector, at Fermilab, near Chicago, will sample the beam as it leaves the Main Injector. Another detector is stationed deep underground at the Soudan Mine in Northern Minnesota. Only muon neutrinos will be generated, so if the other varieties show up, scientists will know it happened in between the detectors.

Searching for Antimatter in Antarctica

Dec 21, 2004 - An international team of researchers have recently launched a huge balloon, the size of a football field, in Antarctica. The instrument, called BESS-Polar launched from McMurdo Station on December 13, and will spend at least 10 days at an altitude of 39 km (24 miles); at the edge of space. The experimenters hope that BESS-Polar will be able to detect any evidence of antimatter created during the Big Bang. And as a bonus, if the instrument can find low-energy antiprotons, it would be evidence of radiation from evaporating black holes, predicted by Stephen Hawking.

Why Time Might Flow in One Direction

Nov 1, 2004 - Physicists have puzzled for more than a century about the nature of time. Why does it go in one direction? Time could go backwards, and physics formulas would still work properly. Researchers from the University of Chicago think they might have an answer: we live in a universe of ever increasing entropy. Instead of one Big Bang going off, and then the Universe expands and cools forever, small fluctuations in nearly empty space could set off new Big Bangs - the Universe would never reach equilibrium.

Links For Physics.

DC Physics - A physics search engine and website directory plus extensive crosslinks and monthly feature articles.
Free Astronomy Wallpapers - Various astronomy related wallpapers for the desktop.
General Relativity Theory - an elementary introduction in two picture stories and mathematical appendix
Hector Parr's Essays - Essays on a number of topics including Infinity, The Collapse of the Universe, Quantum Measurement and Bell's Inequality.
Light and Matter - educational materials for physics and astronomy
Photon Structure - Positronic/negatronic nature of light, pair formation generating matter and photon decay as an explanation of the background red-shift
Physics Forums - The premier science community. Discuss science topics with other members. Vote in polls, read articles and more!
PhysicsWeb - Global news, Physics World magazine and TIPTOP: the essential web resource for physicists
Theory for Gravitic Propulsion - Theory and computer model for Matter, Energy, Space-Time and the Gravitic Effect
ToeQuest - A growing community of researchers seeking the Theory of Everything. Explore topics on quantum anomalies, physics, philosophy, consciousness, and mind.
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