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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James Emory Boyd (July 18, 1906 – February 18, 1998) was an American physicist, mathematician, and academic administrator. He was director of the Georgia Tech Research Institute from 1957 to 1961, president of West Georgia College (now the University of West Georgia) from 1961 to 1971, and acting president of the Georgia Institute of Technology from 1971 to 1972.
A graduate of the University of Georgia, Duke University, and Yale University, Boyd began in academia as an instructor of physics at the University of Georgia, then head of the Mathematics and Science Department at West Georgia College. Subsequently, he became a professor at Georgia Tech and a prominent researcher at the Engineering Experiment Station, now known as the Georgia Tech Research Institute. At the Engineering Experiment Station, Boyd helped spur the organization's mainstay: federally funded electronics research and development. Along with fellow Georgia Tech researchers Gerald Rosselot and Glen P. Robinson, Boyd was influential in the founding of Scientific Atlanta, where he was a board member for 25 years. As director of the Engineering Experiment Station, Boyd focused on the recruitment of talented engineers and an increase in physical space available to the organization, including the establishment of nuclear research at Georgia Tech with a radioisotopes laboratory and the construction of the Frank H. Neely Research Reactor. (Full article...)
Did you know -
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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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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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These are Good articles, which meet a core set of high editorial standards.
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Norris Edwin Bradbury (May 30, 1909 – August 20, 1997), was an American physicist who served as director of the Los Alamos National Laboratory for 25 years from 1945 to 1970. He succeeded Robert Oppenheimer, who personally chose Bradbury for the position of director after working closely with him on the Manhattan Project during World War II. Bradbury was in charge of the final assembly of "the Gadget", detonated in July 1945 for the Trinity test.
Bradbury took charge at Los Alamos at a difficult time. Staff were leaving in droves, living conditions were poor and there was a possibility that the laboratory would close. He managed to persuade enough staff to stay and got the University of California to renew the contract to manage the laboratory. He pushed continued development of nuclear weapons, transforming them from laboratory devices to production models. Numerous improvements made them safer, more reliable and easier to store and handle, and made more efficient use of scarce fissionable materiel. (Full article...) -
A computed tomography scan (CT scan), formerly called computed axial tomography scan (CAT scan), is a medical imaging technique used to obtain detailed internal images of the body. The personnel that perform CT scans are called radiographers or radiology technologists.
CT scanners use a rotating X-ray tube and a row of detectors placed in a gantry to measure X-ray attenuations by different tissues inside the body. The multiple X-ray measurements taken from different angles are then processed on a computer using tomographic reconstruction algorithms to produce tomographic (cross-sectional) images (virtual "slices") of a body. CT scans can be used in patients with metallic implants or pacemakers, for whom magnetic resonance imaging (MRI) is contraindicated. (Full article...) -
Haroutune Krikor Daghlian Jr. (May 4, 1921 – September 15, 1945) was an American physicist with the Manhattan Project, which designed and produced the atomic bombs that were used in World War II. He accidentally irradiated himself on August 21, 1945, during a critical mass experiment at the remote Omega Site of the Los Alamos Laboratory in New Mexico and died 25 days later from the resultant radiation poisoning.
Daghlian was irradiated as a result of a criticality accident that occurred when he accidentally dropped a tungsten carbide brick onto a 6.2 kg bomb core made of plutonium–gallium alloy. This core, subsequently nicknamed the "demon core", was later involved in the death of another physicist, Louis Slotin. (Full article...) -
Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American physicist who received the Nobel Prize in Physics in 1939 for his invention of the cyclotron. He is known for his work on uranium-isotope separation for the Manhattan Project, as well as for founding the Lawrence Berkeley National Laboratory and the Lawrence Livermore National Laboratory.
A graduate of the University of South Dakota and University of Minnesota, Lawrence obtained a PhD in physics at Yale in 1925. In 1928, he was hired as an associate professor of physics at the University of California, Berkeley, becoming the youngest full professor there two years later. In its library one evening, Lawrence was intrigued by a diagram of an accelerator that produced high-energy particles. He contemplated how it could be made compact, and came up with an idea for a circular accelerating chamber between the poles of an electromagnet. The result was the first cyclotron. (Full article...) -
Leo Szilard (/ˈsɪlɑːrd/; Hungarian: Szilárd Leó [ˈsilaːrd ˈlɛoː]; born Leó Spitz; February 11, 1898 – May 30, 1964) was a Hungarian-born physicist, biologist and inventor who made numerous important discoveries in nuclear physics and the biological sciences. He conceived the nuclear chain reaction in 1933, and patented the idea in 1936. In late 1939 he wrote the letter for Albert Einstein's signature that resulted in the Manhattan Project that built the atomic bomb, and then in 1944 wrote the Szilard petition asking President Truman to demonstrate the bomb without dropping it on civilians. According to György Marx, he was one of the Hungarian scientists known as The Martians.
Szilard initially attended Palatine Joseph Technical University in Budapest, but his engineering studies were interrupted by service in the Austro-Hungarian Army during World War I. He left Hungary for Germany in 1919, enrolling at Technische Hochschule (Institute of Technology) in Berlin-Charlottenburg (now Technische Universität Berlin), but became bored with engineering and transferred to Friedrich Wilhelm University, where he studied physics. He wrote his doctoral thesis on Maxwell's demon, a long-standing puzzle in the philosophy of thermal and statistical physics. Szilard was the first scientist of note to recognize the connection between thermodynamics and information theory. (Full article...) -
Sir Chandrasekhara Venkata Raman (/ˈrɑːmən/; 7 November 1888 – 21 November 1970) was an Indian physicist known for his work in the field of light scattering. Using a spectrograph that he developed, he and his student K. S. Krishnan discovered that when light traverses a transparent material, the deflected light changes its wavelength. This phenomenon, a hitherto unknown type of scattering of light, which they called modified scattering was subsequently termed the Raman effect or Raman scattering. In 1930, Raman received the Nobel Prize in Physics for this discovery and was the first Asian and the first non-White to receive a Nobel Prize in any branch of science.
Born to Tamil Brahmin parents, Raman was a precocious child, completing his secondary and higher secondary education from St Aloysius' Anglo-Indian High School at the age of 11 and 13, respectively. He topped the bachelor's degree examination of the University of Madras with honours in physics from Presidency College at age 16. His first research paper, on diffraction of light, was published in 1906 while he was still a graduate student. The next year he obtained a master's degree. He joined the Indian Finance Service in Calcutta as Assistant Accountant General at age 19. There he became acquainted with the Indian Association for the Cultivation of Science (IACS), the first research institute in India, which allowed him to carry out independent research and where he made his major contributions in acoustics and optics. (Full article...) -
John Tucker "Chick" Hayward (15 November 1908 – 23 May 1999) was an American naval aviator during World War II. He helped develop one of the two atomic bombs that was dropped on Japan in the closing days of the war. Later, he was a pioneer in the development of nuclear propulsion, nuclear weapons, guidance systems for ground- and air-launched rockets, and underwater anti-submarine weapons. A former batboy for the New York Yankees, Hayward dropped out of high school and lied about his age to enlist in the United States Navy at age 16. He was subsequently admitted to the United States Naval Academy at Annapolis, from which he graduated 51st in his class of 1930. He volunteered for naval aviation.
During World War II, he served at the Naval Aircraft Factory in Philadelphia, where he was involved in an effort to improve aircraft instrumentation, notably the compass and altimeter. He attended the University of Pennsylvania's Moore School of Electrical Engineering, and studied nuclear physics. In June 1942, he assumed command of a new patrol bomber squadron, VB-106, equipped with PB4Y-1 Liberators, which he led in a daring raid on Wake Island, in the Solomon Islands campaign, and in the Southwest Pacific Area. Returning to the United States in 1944, he was posted to the Naval Ordnance Test Station at Inyokern, California, where he joined the Manhattan Project, participating in Project Camel, the development of the non-nuclear components of the Fat Man bomb, and in its drop testing. (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...) -
Quantum Reality is a 1985 popular science book by physicist Nick Herbert, a member of the Fundamental Fysiks Group which was formed to explore the philosophical implications of quantum theory. The book attempts to address the ontology of quantum objects, their attributes, and their interactions, without reliance on advanced mathematical concepts. Herbert discusses the most common interpretations of quantum mechanics and their consequences in turn, highlighting the conceptual advantages and drawbacks of each. (Full article...)
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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...) -
Stanisław Marcin Ulam (Polish: [sta'ɲiswaf 'mart͡ɕin 'ulam]; 13 April 1909 – 13 May 1984) was a Polish mathematician, nuclear physicist and computer scientist. He participated in the Manhattan Project, originated the Teller–Ulam design of thermonuclear weapons, discovered the concept of the cellular automaton, invented the Monte Carlo method of computation, and suggested nuclear pulse propulsion. In pure and applied mathematics, he proved a number of theorems and proposed several conjectures.
Born into a wealthy Polish Jewish family in Lemberg, Austria-Hungary; Ulam studied mathematics at the Lwów Polytechnic Institute, where he earned his PhD in 1933 under the supervision of Kazimierz Kuratowski and Włodzimierz Stożek. In 1935, John von Neumann, whom Ulam had met in Warsaw, invited him to come to the Institute for Advanced Study in Princeton, New Jersey, for a few months. From 1936 to 1939, he spent summers in Poland and academic years at Harvard University in Cambridge, Massachusetts, where he worked to establish important results regarding ergodic theory. On 20 August 1939, he sailed for the United States for the last time with his 17-year-old brother Adam Ulam. He became an assistant professor at the University of Wisconsin–Madison in 1940, and a United States citizen in 1941. (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...) -
Figure 2: The radius r of the green and blue planets are the same, but their angular speed differs by a factor k. Examples of such orbits are shown in Figures 1 and 3–5.
In classical mechanics, Newton's theorem of revolving orbits identifies the type of central force needed to multiply the angular speed of a particle by a factor k without affecting its radial motion (Figures 1 and 2). Newton applied his theorem to understanding the overall rotation of orbits (apsidal precession, Figure 3) that is observed for the Moon and planets. The term "radial motion" signifies the motion towards or away from the center of force, whereas the angular motion is perpendicular to the radial motion.
Isaac Newton derived this theorem in Propositions 43–45 of Book I of his Philosophiæ Naturalis Principia Mathematica, first published in 1687. In Proposition 43, he showed that the added force must be a central force, one whose magnitude depends only upon the distance r between the particle and a point fixed in space (the center). In Proposition 44, he derived a formula for the force, showing that it was an inverse-cube force, one that varies as the inverse cube of r. In Proposition 45 Newton extended his theorem to arbitrary central forces by assuming that the particle moved in nearly circular orbit. (Full article...) -
Max Born (German: [ˈmaks ˈbɔʁn] ⓘ; 11 December 1882 – 5 January 1970) was a German-British physicist who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics, and supervised the work of a number of notable physicists in the 1920s and 1930s. Born shared the 1954 Nobel Prize in Physics with Walther Bothe "for his fundamental research in quantum mechanics, especially in the statistical interpretation of the wave function".
Born entered the University of Göttingen in 1904, where he met the three renowned mathematicians Felix Klein, David Hilbert, and Hermann Minkowski. He wrote his PhD thesis on the subject of the stability of elastic wires and tapes, winning the university's Philosophy Faculty Prize. In 1905, he began researching special relativity with Minkowski, and subsequently wrote his habilitation thesis on the Thomson model of the atom. A chance meeting with Fritz Haber in Berlin in 1918 led to discussion of how an ionic compound is formed when a metal reacts with a halogen, which is today known as the Born–Haber cycle. (Full article...) -
Mary Jackson (née Winston; April 9, 1921 – February 11, 2005) was an American mathematician and aerospace engineer at the National Advisory Committee for Aeronautics (NACA), which in 1958 was succeeded by the National Aeronautics and Space Administration (NASA). She worked at Langley Research Center in Hampton, Virginia, for most of her career. She started as a computer at the segregated West Area Computing division in 1951. In 1958, after taking engineering classes, she became NASA's first black female engineer.
After 34 years at NASA, Jackson had earned the most senior engineering title available. She realized she could not earn further promotions without becoming a supervisor. She accepted a demotion to become a manager of both the Federal Women's Program, in the NASA Office of Equal Opportunity Programs and of the Affirmative Action Program. In this role, she worked to influence the hiring and promotion of women in NASA's science, engineering, and mathematics careers. (Full article...)
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March anniversaries
- 1 March 1966 – first spacecraft crash-lands on Venus
- 14 March 1879 – Albert Einstein's birthday
- 14 March 2018 – Stephen Hawking died
- 20 March 1942 - Gabriele Veneziano's Birthday
- 24 March 1993 – Comet Shoemaker–Levy 9 discovered
General images
The following are images from various physics-related articles on Wikipedia.
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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) -
Albert Einstein (1879–1955), ca. 1905 (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) -
Rudolf Clausius (1822–1888) (from History of physics) -
Ludwig Boltzmann (1844–1906) (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) -
Johannes Kepler (1571–1630) (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) -
Christiaan Huygens (1629–1695) (from History of physics) -
The Standard Model (from History of 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) -
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) -
René Descartes (1596–1650) (from History of physics) -
Heike Kamerlingh Onnes and Johannes van der Waals with the helium liquefactor at Leiden in 1908 (from Condensed matter physics) -
Einstein proposed that gravitation results from masses (or their equivalent energies) curving ("bending") the spacetime in which they exist, altering the paths they follow within it. (from History of physics) -
Image of X-ray diffraction pattern from a protein crystal (from Condensed matter physics) -
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Nicolaus Copernicus (1473–1543) developed a heliocentric model of the Solar System. (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) -
Composite montage comparing Jupiter (left) and its four Galilean moons (from top: Io, Europa, Ganymede, Callisto) (from History of physics) -
Galileo Galilei (1564–1642), early proponent of the modern scientific worldview and method (from History of physics) -
Max Planck (1858–1947) (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) -
Gottfried Leibniz (1646–1716) (from History of physics) -
Chien-Shiung Wu worked on parity violation in 1956 and announced her results in January 1957. (from History of physics) -
Alessandro Volta (1745–1827) (from History of physics) -
James Clerk Maxwell (1831–1879) (from History of physics) -
Marie Skłodowska-Curie
(1867–1934) received Nobel prizes in physics (1903) and chemistry (1911). (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) -
Werner Heisenberg (1901–1976) (from History of physics) -
Daniel Bernoulli (1700–1782) (from History of 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) -
Richard Feynman's Los Alamos ID badge (from History of physics) -
Michael Faraday (1791–1867) (from History of physics) -
Artist's rendition of Kepler-62f, a potentially habitable exoplanet discovered using data transmitted by Kepler space telescope, named for Kepler (from History of physics) -
J.J. Thomson (1856–1940), discoverer of electron and isotopy, and inventor of mass spectrometer, received 1906 Nobel Prize in Physics. (from History of physics) -
Sir Isaac Newton (1642–1727) (from History of physics) -
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The ancient Greek mathematician Archimedes, developer of ideas regarding fluid mechanics and buoyancy. (from History of physics) -
William Thomson (Lord Kelvin)
(1824–1907) (from History of physics) -
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1927 Solvay Conference included prominent physicists Albert Einstein, Werner Heisenberg, Max Planck, Hendrik Lorentz, Niels Bohr, Marie Curie, Erwin Schrödinger, Paul Dirac (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
Specific fields: Acoustics | Astrophysics | Atomic physics | Molecular physics | Optical physics | Computational physics | Condensed matter physics | Nuclear physics | Particle physics | Plasma physics
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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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