Portal:Physics
The Physics Portal
Physics is the scientific study of matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. Physics is one of the most fundamental scientific disciplines. A scientist who specializes in the field of physics is called a physicist.
Physics is one of the oldest academic disciplines. 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 branched into separate research endeavors. 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 these and other academic disciplines such as mathematics and philosophy.
Advances in physics often enable new technologies. For example, advances in the understanding of electromagnetism, solid-state physics, and nuclear physics led directly to the development of technologies that have transformed modern 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. (Full article...)
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Edward Teller (Hungarian: Teller Ede; January 15, 1908 – September 9, 2003) was a Hungarian and American theoretical physicist and chemical engineer who is known colloquially as "the father of the hydrogen bomb" and one of the creators of the Teller–Ulam design based on Stanisław Ulam's design.
Born in Austria-Hungary in 1908, Teller emigrated to the United States in the 1930s, one of the many so-called "Martians", a group of prominent Hungarian scientist émigrés. He made numerous contributions to nuclear and molecular physics, spectroscopy (in particular the Jahn–Teller and Renner–Teller effects), and surface physics. His extension of Enrico Fermi's theory of beta decay, in the form of Gamow–Teller transitions, provided an important stepping stone in its application, while the Jahn–Teller effect and the Brunauer–Emmett–Teller (BET) theory have retained their original formulation and are still mainstays in physics and chemistry. (Full article...)
Did you know -
- ... the mirage of astronomical objects is an optical phenomenon, which produces distorted or multiple images of astronomical objects such as the Sun, the Moon, the planets, bright stars and very bright comets
- ... that your watch would run slower when orbiting a black hole than it would on Earth?
- ... that homing pigeons wouldn't be able to navigate on Mercury because the planet has no magnetic field or atmosphere?
Selected image -
The Hubble Deep Field (HDF) is an image of a small region in the constellation Ursa Major, constructed from a series of observations by the Hubble Space Telescope. It covers an area 2.5 arcminutes across, two parts in a million of the whole sky
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The Hubble Deep Field -
Details from the Hubble Deep Field illustrate the wide variety of galaxy shapes, sizes and colours found in the distant universe.
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Luis Walter Alvarez (June 13, 1911 – September 1, 1988) was an American experimental physicist, inventor, and professor who was awarded the Nobel Prize in Physics in 1968 for his discovery of resonance states in particle physics using the hydrogen bubble chamber. In 2007 the American Journal of Physics commented, "Luis Alvarez was one of the most brilliant and productive experimental physicists of the twentieth century."
After receiving his PhD from the University of Chicago in 1936, Alvarez went to work for Ernest Lawrence at the Radiation Laboratory at the University of California, Berkeley. Alvarez devised a set of experiments to observe K-electron capture in radioactive nuclei, predicted by the beta decay theory but never before observed. He produced tritium using the cyclotron and measured its lifetime. In collaboration with Felix Bloch, he measured the magnetic moment of the neutron. (Full article...) -
Seth Henry Neddermeyer (September 16, 1907 – January 29, 1988) was an American physicist who co-discovered the muon, and later championed the implosion-type nuclear weapon while working on the Manhattan Project at the Los Alamos Laboratory during World War II. (Full article...) -
Eugene Paul Wigner (Hungarian: Wigner Jenő Pál, pronounced [ˈviɡnɛr ˈjɛnøː ˈpaːl]; November 17, 1902 – January 1, 1995) was a Hungarian-American theoretical physicist who also contributed to mathematical physics. He received the Nobel Prize in Physics in 1963 "for his contributions to the theory of the atomic nucleus and the elementary particles, particularly through the discovery and application of fundamental symmetry principles".
A graduate of the Technical Hochschule Berlin (now Technische Universität Berlin), Wigner worked as an assistant to Karl Weissenberg and Richard Becker at the Kaiser Wilhelm Institute in Berlin, and David Hilbert at the University of Göttingen. Wigner and Hermann Weyl were responsible for introducing group theory into physics, particularly the theory of symmetry in physics. Along the way he performed ground-breaking work in pure mathematics, in which he authored a number of mathematical theorems. In particular, Wigner's theorem is a cornerstone in the mathematical formulation of quantum mechanics. He is also known for his research into the structure of the atomic nucleus. In 1930, Princeton University recruited Wigner, along with John von Neumann, and he moved to the United States, where he obtained citizenship in 1937. (Full article...) -
The Type Ib supernova SN 2008D in galaxy NGC 2770, shown in X-ray (left) and visible light (right), at the corresponding positions of the images. (NASA image.)
Type Ib and Type Ic supernovae are categories of supernovae that are caused by the stellar core collapse of massive stars. These stars have shed or been stripped of their outer envelope of hydrogen, and, when compared to the spectrum of Type Ia supernovae, they lack the absorption line of silicon. Compared to Type Ib, Type Ic supernovae are hypothesized to have lost more of their initial envelope, including most of their helium. The two types are usually referred to as stripped core-collapse supernovae. (Full article...) -
The radioactive beta decay is due to the weak interaction, which transforms a neutron into a proton, an electron, and an electron antineutrino.
In nuclear physics and particle physics, the weak interaction, also called the weak force, is one of the four known fundamental interactions, with the others being electromagnetism, the strong interaction, and gravitation. It is the mechanism of interaction between subatomic particles that is responsible for the radioactive decay of atoms: The weak interaction participates in nuclear fission and nuclear fusion. The theory describing its behaviour and effects is sometimes called quantum flavordynamics (QFD); however, the term QFD is rarely used, because the weak force is better understood by electroweak theory (EWT).
The effective range of the weak force is limited to subatomic distances and is less than the diameter of a proton. (Full article...) -
Matteucci's frog battery, 1845 (top left); Aldini's frog battery, 1818 (bottom); apparatus for controlled exposure of gases to frog battery (top right).
A frog battery is an electrochemical battery consisting of a number of dead frogs (or sometimes live ones), which form the cells of the battery connected in a series arrangement. It is a kind of biobattery. It was used in early scientific investigations of electricity and academic demonstrations.
The principle behind the battery is the injury potential created in a muscle when it is damaged, although this was not fully understood in the 18th and 19th centuries; the potential being caused incidentally due to the dissection of the frog's muscles. (Full article...) -
Alvin Martin Weinberg (/ˈwaɪnbɜːrɡ/; April 20, 1915 – October 18, 2006) was an American nuclear physicist who was the administrator of Oak Ridge National Laboratory (ORNL) during and after the Manhattan Project. He came to Oak Ridge, Tennessee, in 1945 and remained there until his death in 2006. He was the first to use the term "Faustian bargain" to describe nuclear energy.
A graduate of the University of Chicago, which awarded him his doctorate in mathematical biophysics in 1939, Weinberg joined the Manhattan Project's Metallurgical Laboratory in September 1941. The following year he became part of Eugene Wigner's Theoretical Group, whose task was to design the nuclear reactors that would convert uranium into plutonium. (Full article...) -
A bouncing ball. The motion is not quite parabolic due to air resistance.
The physics of a bouncing ball concerns the physical behaviour of bouncing balls, particularly its motion before, during, and after impact against the surface of another body. Several aspects of a bouncing ball's behaviour serve as an introduction to mechanics in high school or undergraduate level physics courses. However, the exact modelling of the behaviour is complex and of interest in sports engineering.
The motion of a ball is generally described by projectile motion (which can be affected by gravity, drag, the Magnus effect, and buoyancy), while its impact is usually characterized through the coefficient of restitution (which can be affected by the nature of the ball, the nature of the impacting surface, the impact velocity, rotation, and local conditions such as temperature and pressure). To ensure fair play, many sports governing bodies set limits on the bounciness of their ball and forbid tampering with the ball's aerodynamic properties. The bounciness of balls has been a feature of sports as ancient as the Mesoamerican ballgame. (Full article...) -
Sir Ernest William Titterton CMG FRS FAA (4 March 1916 – 8 February 1990) was a British nuclear physicist.
A graduate of the University of Birmingham, Titterton worked in a research position under Mark Oliphant, who recruited him to work on radar for the British Admiralty during the first part of the Second World War. In 1943, he joined the Manhattan Project's Los Alamos Laboratory, where he helped develop the first atomic bombs. He eventually became one of the laboratory's group leaders. He participated in the Operation Crossroads nuclear tests at the Bikini Atoll in 1946, where he performed the countdown for both tests. With the passage of the Atomic Energy Act of 1946, known as the McMahon Act, all British government employees had to leave. He was the last member of the British Mission to do so, in April 1947. (Full article...) -
Geocentric celestial spheres; Peter Apian's Cosmographia (Antwerp, 1539)
The celestial spheres, or celestial orbs, were the fundamental entities of the cosmological models developed by Plato, Eudoxus, Aristotle, Ptolemy, Copernicus, and others. In these celestial models, the apparent motions of the fixed stars and planets are accounted for by treating them as embedded in rotating spheres made of an aetherial, transparent fifth element (quintessence), like gems set in orbs. Since it was believed that the fixed stars did not change their positions relative to one another, it was argued that they must be on the surface of a single starry sphere.
In modern thought, the orbits of the planets are viewed as the paths of those planets through mostly empty space. Ancient and medieval thinkers, however, considered the celestial orbs to be thick spheres of rarefied matter nested one within the other, each one in complete contact with the sphere above it and the sphere below. When scholars applied Ptolemy's epicycles, they presumed that each planetary sphere was exactly thick enough to accommodate them. By combining this nested sphere model with astronomical observations, scholars calculated what became generally accepted values at the time for the distances to the Sun: about 4 million miles (6.4 million kilometres), to the other planets, and to the edge of the universe: about 73 million miles (117 million kilometres). The nested sphere model's distances to the Sun and planets differ significantly from modern measurements of the distances, and the size of the universe is now known to be inconceivably large and continuously expanding. (Full article...) -
Maria Goeppert Mayer (German: [maˈʁiːa ˈɡœpɐt ˈmaɪɐ] ⓘ; née Göppert; June 28, 1906 – February 20, 1972) was a German-American theoretical physicist and Nobel laureate in Physics for proposing the nuclear shell model of the atomic nucleus. She was the second woman to win a Nobel Prize in Physics, the first being Marie Curie. In 1986, the Maria Goeppert-Mayer Award for early-career women physicists was established in her honor.
A graduate of the University of Göttingen, Goeppert Mayer wrote her doctoral thesis on the theory of possible two-photon absorption by atoms. At the time, the chances of experimentally verifying her thesis seemed remote, but the development of the laser in the 1960s later permitted this. Today, the unit for the two-photon absorption cross section is named the Goeppert Mayer (GM) unit. (Full article...) -
The Saffir–Simpson hurricane wind scale (SSHWS) classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished by the intensities of their sustained winds. This measuring system was formerly known as the Saffir–Simpson hurricane scale, or SSHS.
To be classified as a hurricane, a tropical cyclone must have one-minute-average maximum sustained winds at 10 m (33 ft) above the surface of at least 74 mph (64 kn, 119 km/h; Category 1). The highest classification in the scale, Category 5, consists of storms with sustained winds of at least 157 mph (137 kn, 252 km/h). The classifications can provide some indication of the potential damage and flooding a hurricane will cause upon landfall. (Full article...) -
The missing aircraft (9M-MRO) seen in 2011.
The analysis of communications between Malaysia Airlines Flight 370 and Inmarsat's satellite telecommunication network provide the primary source of information about Flight 370's location and possible in-flight events after it disappeared from military radar coverage at 02:22 Malaysia Standard Time (MYT) on 8 March 2014 (17:22 UTC, 7 March), one hour after communication with air traffic control ended and the aircraft departed from its planned flight path while over the South China Sea.
Flight 370 was a scheduled commercial flight with 227 passengers and 12 crew which departed Kuala Lumpur, Malaysia at 0:41 and was scheduled to land in Beijing, China at 6:30 China Standard Time (6:30 MYT; 22:30 UTC, 7 March). Malaysia has worked in conjunction with the Australian Transport Safety Bureau to co-ordinate the analysis, which has also involved the UK's Air Accidents Investigation Branch, Inmarsat, and US National Transportation Safety Board. Other groups have also made efforts to analyse the satellite communications, albeit challenged by a lack of publicly available information for several months after the disappearance. On 29 July 2015, debris was discovered on Réunion Island which was later confirmed to have come from Flight 370; it is the first physical evidence that Flight 370 ended in the Indian Ocean. (Full article...) -
Mujaddid Ahmed Ijaz, Ph.D. (Urdu: مجدد احمد اعجا ز; June 12, 1937 – July 9, 1992), was a Pakistani-American experimental physicist noted for his role in discovering new isotopes that expanded the neutron-deficient side of the atomic chart. Some of the isotopes he discovered enabled significant advances in medical research, particularly in the treatment of cancer, and further advanced the experimental understanding of nuclear structures. Ijaz conducted his research work at Oak Ridge National Laboratories (ORNL). He and his ORNL colleagues published more than 60 papers in physics journals announcing isotope discoveries and other results of their accelerator experiments from 1968 until 1983.
Ijaz participated in the U.S. Atoms for Peace initiative during the 1970s. The program provided a number of third-world countries, including Pakistan, with civilian nuclear reactor technology to develop energy for peaceful purposes. As a tenured professor of physics at Virginia Tech, he acted as thesis adviser to graduate students from around the world in experimental physics disciplines. Ijaz made extensive trips abroad during his career, including sabbaticals as a visiting professor at Saudi Arabia's King Fahd University of Petroleum and Minerals. in the early 1980s and as a visiting faculty member at the Abdus Salam International Centre for Theoretical Physics in Trieste, Italy in 1985. He retired Professor Emeritus of Physics from Virginia Tech in December 1991 after a 27-year career in teaching and research. Ijaz and his wife emigrated to the United States and settled in Virginia, where they had five children. He died in 1992 after a battle with cancer. (Full article...) -
James Clerk Maxwell FRS FRSE (13 June 1831 – 5 November 1879) was a Scottish physicist and mathematician who was responsible for the classical theory of electromagnetic radiation, which was the first theory to describe electricity, magnetism and light as different manifestations of the same phenomenon. Maxwell's equations for electromagnetism achieved the second great unification in physics, where the first one had been realised by Isaac Newton. Maxwell was also key in the creation of statistical mechanics.
With the publication of "A Dynamical Theory of the Electromagnetic Field" in 1865, Maxwell demonstrated that electric and magnetic fields travel through space as waves moving at the speed of light. He proposed that light is an undulation in the same medium that is the cause of electric and magnetic phenomena. The unification of light and electrical phenomena led to his prediction of the existence of radio waves, and the paper contained his final version of his equations, which he had been working on since 1856. As a result of his equations, and other contributions such as introducing an effective method to deal with network problems and linear conductors, he is regarded as a founder of the modern field of electrical engineering. In 1871, Maxwell became the first Cavendish Professor of Physics, serving until his death in 1879. (Full article...)
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January anniversaries
1 January
- 1894 - Satyendra Nath Bose's birthday.
- 1801 - Giuseppe Piazzi is the first to notice the dwarf planet Ceres. However, very soon astronomers lose sight of its orbital path. After some months, Giuseppe Piazzi finally calculates its correct position on December 31.
- 1985 - Ernie Wise, a comedian, places the first mobile phone call in the UK.
2 January
- 2 January 1822 - Rudolf Clausius was born.
8 January
- 8 January 1942 - Stephen Hawking was born, on the same day that Galileo Galilei died in 1642.
15 January
- 15 January 1908 - Edward Teller was born.
General images
The following are images from various physics-related articles on Wikipedia.
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Max Planck (1858–1947) (from History of physics) -
Chien-Shiung Wu worked on parity violation in 1956 and announced her results in January 1957. (from History of physics) -
Computer simulation of nanogears made of fullerene molecules. It is hoped that advances in nanoscience will lead to machines working on the molecular scale. (from Condensed matter physics) -
Ludwig Boltzmann (1844–1906) (from History of physics) -
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Gottfried Leibniz (1646–1716) (from History of physics) -
Sir Isaac Newton (1642–1727) (from History of physics) -
Galileo Galilei, early proponent of the modern scientific worldview and method (1564–1642) (from History of physics) -
The Polish astronomer Nicolaus Copernicus (1473–1543) is remembered for his development of a heliocentric model of the Solar System. (from History of physics) -
J. J. Thomson (1856–1940) discovered the electron and isotopy and also invented the mass spectrometer. He was awarded the Nobel Prize in Physics in 1906. (from History of physics) -
Image of X-ray diffraction pattern from a protein crystal (from Condensed matter physics) -
Einstein proposed that gravitation is a result of masses (or their equivalent energies) curving ("bending") the spacetime in which they exist, altering the paths they follow within it. (from History of physics) -
One possible signature of a Higgs boson from a simulated proton–proton collision. It decays almost immediately into two jets of hadrons and two electrons, visible as lines. (from History of physics) -
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Richard Feynman's Los Alamos ID badge (from History of physics) -
Johannes Kepler.(1571–1630) (from History of physics) -
René Descartes (1596–1650) (from History of physics) -
Werner Heisenberg (1901–1976) (from History of physics) -
A Feynman diagram representing (left to right) the production of a photon (blue sine wave) from the annihilation of an electron and its complementary antiparticle, the positron. The photon becomes a quark–antiquark pair and a gluon (green spiral) is released. (from History of physics) -
Christiaan Huygens (1629–1695) (from History of physics) -
Albert Einstein (1879–1955), photographed here in around 1905 (from History of physics) -
Daniel Bernoulli (1700–1782) (from History of physics) -
The first Bose–Einstein condensate observed in a gas of ultracold rubidium atoms. The blue and white areas represent higher density. (from Condensed matter physics) -
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James Clerk Maxwell (1831–1879) (from History of physics) -
Star maps by the 11th century Chinese polymath Su Song are the oldest known woodblock-printed star maps to have survived to the present day. This example, dated 1092, employs the cylindricalequirectangular projection. (from History of physics) -
A composite montage comparing Jupiter (lefthand side) and its four Galilean moons (top to bottom: Io, Europa, Ganymede, Callisto) (from History of physics) -
Heike Kamerlingh Onnes and Johannes van der Waals with the helium liquefactor at Leiden in 1908 (from Condensed matter physics) -
Classical physics (Rayleigh–Jeans law, black line) failed to explain black-body radiation – the so-called ultraviolet catastrophe. The quantum description (Planck's law, colored lines) is said to be modern physics. (from Modern physics) -
Classical physics is usually concerned with everyday conditions: speeds are much lower than the speed of light, sizes are much greater than that of atoms, yet very small in astronomical terms. Modern physics, however, is concerned with high velocities, small distances, and very large energies. (from Modern physics) -
Michael Faraday (1791–1867) (from History of physics) -
The Hindu-Arabic numeral system. The inscriptions on the edicts of Ashoka (3rd century BCE) display this number system being used by the Imperial Mauryas. (from History of physics) -
Rudolf Clausius (1822–1888) (from History of physics) -
The Standard Model (from History of physics) -
Alessandro Volta (1745–1827) (from History of physics) -
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An artist's rendition of Kepler-62f, a potentially habitable exoplanet discovered using data transmitted by the Kepler space telescope, named after Kepler. (from History of physics) -
Marie Skłodowska-Curie
(1867–1934) was awarded two Nobel prizes, Physics (1903) and Chemistry (1911) (from History of physics) -
A magnet levitating above a high-temperature superconductor. Today some physicists are working to understand high-temperature superconductivity using the AdS/CFT correspondence. (from Condensed matter physics) -
William Thomson (Lord Kelvin)
(1824–1907) (from History of physics) -
The quantum Hall effect: Components of the Hall resistivity as a function of the external magnetic field (from Condensed matter physics) -
The ancient Greek mathematician Archimedes, developer of ideas regarding fluid mechanics and buoyancy. (from History of physics)
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Categories
Fundamentals: Concepts in physics | Constants | Physical quantities | Units of measure | Mass | Length | Time | Space | Energy | Matter | Force | Gravity | Electricity | Magnetism | Waves
Basic physics: Mechanics | Electromagnetism | Statistical mechanics | Thermodynamics | Quantum mechanics | Theory of relativity | Optics | Acoustics
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Background: Physicists | History of physics | Philosophy of physics | Physics education | Physics journals | Physics organizations
Other: Physics in fiction | Physics lists | Physics software | Physics stubs
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.
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