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The Physics Portal

Various examples of physical phenomena

Physics (from Ancient Greek: φυσική (ἐπιστήμη), romanized: physikḗ (epistḗmē), lit. 'knowledge of nature', from φύσις phýsis 'nature') is the natural science that studies matter, its motion and behavior through space and time, and that studies the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves.

Physics is one of the oldest academic disciplines and, through its inclusion of astronomy, perhaps the oldest. Over much of the past two millennia, physics, chemistry, biology, and certain branches of mathematics, were a part of natural philosophy, but during the Scientific Revolution in the 17th century these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, and the boundaries of physics are not rigidly defined. New ideas in physics often explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy.

Advances in physics often enable advances in new technologies. For example, advances in the understanding of electromagnetism, solid-state physics, and nuclear physics led directly to the development of new products that have dramatically transformed modern-day society, such as television, computers, domestic appliances, and nuclear weapons; advances in thermodynamics led to the development of industrialization; and advances in mechanics inspired the development of calculus.

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Richard Phillips Feynman, ForMemRS (/ˈfaɪnmən/; May 11, 1918 – February 15, 1988) was an American theoretical physicist, known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, and the physics of the superfluidity of supercooled liquid helium, as well as in particle physics for which he proposed the parton model. For contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin'ichirō Tomonaga.

Feynman developed a widely used pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World he was ranked as one of the ten greatest physicists of all time. Read more...

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...that while Albert Einstein is most famous for his Theory of Relativity, he was awarded the Nobel Prize for his explanation of the photoelectric effect?

...that gravitational tidal accelerations are the result of the curvature of spacetime?

...that the blue glow of the Cherenkov effect is due to electrons moving faster than the speed of light in water?

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A diagram by Valeriy Zagrebaev et al. showing the measured (boxed) and predicted (shaded) half-lives of superheavy nuclides, sorted by number of protons and neutrons. The expected location of the island of stability around Z = 112 is circled.

In nuclear physics, the island of stability is a predicted set of superheavy nuclides that may have considerably longer half-lives than known superheavy nuclides. It is predicted to appear as an "island" in the chart of nuclides, separated from known stable and long-lived primordial radionuclides. Its theoretical existence is attributed to stabilizing effects of predicted magic numbers of protons and neutrons in the superheavy mass region.

Various predictions have been made regarding the exact location of the island of stability, though it is generally thought to center near copernicium and flerovium isotopes in the vicinity of the predicted closed shell at N = 184. These models strongly suggest that the closed shell will confer additional stability towards fission, while also leading to longer half-lives towards alpha decay. While these effects are expected to be greatest near atomic number Z = 114 and N = 184, the region of increased stability is expected to encompass several neighboring elements, and there may also be additional islands of stability around heavier nuclei that are doubly magic (having magic numbers of both protons and neutrons). Estimates of the stability of the elements on the island are usually around a half-life of minutes or days; however, some estimates predict half-lives of millions of years. Read more...

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September anniversaries

6 September 1809 - Sir George Cayley identifies the four aerodynamic forces
3 September 1821 - Faraday discovers electromagnetic rotation (the principle behind the electric motor).
- September 1911 - The Sackur-Tetrode Equation is published in Annalen der Physik.
29 September 1904 - Nature publishes Wood's letter discrediting N-rays.
27 September 1905 - E=mc² --- Annalen der Physik publishes the Mass–Energy equivalence
9 September 1934: The American Rocket Society (ARS) launched Rocket No. 4 to 400 feet.
17 September 1959 - The first powered X-15 flight.
9 September 1959 - The Atlas 10-D rocket is launched.
1 September 1974 - Pioneer 11 sends polar images of Jupiter.
20 September 1979 - The High Energy Astronomical Observatory (HEAO) 3 is launched.
- September 1981 - Invention of the scanning tunneling microscope.

Births

22 September 1791 Michael Faraday (d.1867)
29 September 1901 Enrico Fermi

Deaths

5 September 1906 - Ludwig Boltzmann
7 September 1783 - Leonhard Euler
9 September 2003 - Edward Teller

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Difference between classical and modern physics

The basic domains of physics

While physics aims to discover universal laws, its theories lie in explicit domains of applicability. Loosely speaking, the laws of classical physics accurately describe systems whose important length scales are greater than the atomic scale and whose motions are much slower than the speed of light. Outside of this domain, observations do not match their predictions. Albert Einstein contributed the framework of special relativity, which replaced notions of absolute time and space with spacetime and allowed an accurate description of systems whose components have speeds approaching the speed of light. Max Planck, Erwin Schrödinger, and others introduced quantum mechanics, a probabilistic notion of particles and interactions that allowed an accurate description of atomic and subatomic scales. Later, quantum field theory unified quantum mechanics and special relativity. General relativity allowed for a dynamical, curved spacetime, with which highly massive systems and the large-scale structure of the universe can be well-described. General relativity has not yet been unified with the other fundamental descriptions; several candidate theories of quantum gravity are being developed.

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Physics topics

Classical physics traditionally includes the fields of mechanics, optics, electricity, magnetism, acoustics and thermodynamics. The term Modern physics is normally used for fields which rely heavily on quantum theory, including quantum mechanics, atomic physics, nuclear physics, particle physics and condensed matter physics. General and special relativity are usually considered to be part of modern physics as well.

Fundamental Concepts	Classical Physics	Modern Physics	Cross Discipline Topics
Continuum	Solid Mechanics	Fluid Mechanics	Geophysics
Motion	Classical Mechanics	Analytical mechanics	Mathematical Physics
Kinects	Kinematics	Kinematic chain	Robotics
Matter	Classical states	Modern states	Nanotechnology
Energy	Chemical Physics	Plasma Physics	Materials Science
Cold	Cryophysics	Cryogenics	Superconductivity
Heat	Heat transfer	Transport Phenomena	Combustion
Entropy	Thermodynamics	Statistical mechanics	Phase transitions
Particle	Particulates	Particle physics	Particle accelerator
Antiparticle	Antimatter	Annihilation physics	Gamma ray
Waves	Oscillation	Quantum oscillation	Vibration
Gravity	Gravitation	Gravitational wave	Celestial mechanics
Vacuum	Pressure physics	Vacuum state physics	Quantum fluctuation
Random	Statistics	Stochastic process	Brownian motion
Spacetime	Special Relativity	General Relativity	Black holes
Quanta	Quantum mechanics	Quantum field theory	Quantum computing
Radiation	Radioactivity	Radioactive decay	Cosmic ray
Light	Optics	Quantum optics	Photonics
Electrons	Solid State	Condensed Matter	Symmetry breaking
Electricity	Electrical circuit	Electronics	Integrated circuit
Electromagnetism	Electrodynamics	Quantum Electrodynamics	Chemical Bonds
Strong interaction	Nuclear Physics	Quantum Chromodynamics	Quark model
Weak interaction	Atomic Physics	Electroweak theory	Radioactivity
Standard Model	Fundamental interaction	Grand Unified Theory	Higgs boson
Information	Information science	Quantum information	Holographic principle
Life	Biophysics	Quantum Biology	Astrobiology
Conscience	Neurophysics	Quantum mind	Quantum brain dynamics
Cosmos	Astrophysics	Cosmology	Observable universe
Cosmogony	Big Bang	Mathematical universe	Multiverse
Chaos	Chaos theory	Quantum chaos	Perturbation theory
Complexity	Dynamical system	Complex system	Emergence
Quantization	Canonical quantization	Loop quantum gravity	Spin foam
Unification	Quantum gravity	String theory	Theory of Everything