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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Trinity was the code name of the first detonation of a nuclear weapon, conducted by the United States Army at 5:29 a.m. MWT (11:29:21 GMT) on July 16, 1945, as part of the Manhattan Project. The test was of an implosion-design plutonium bomb, nicknamed "The Gadget", of the same design as the Fat Man bomb later detonated over Nagasaki, Japan, on August 9, 1945. Concerns about whether the complex Fat Man design would work led to a decision to conduct the first nuclear test. The code name "Trinity" was assigned by J. Robert Oppenheimer, the director of the Los Alamos Laboratory, possibly inspired by the poetry of John Donne.
The test, both planned and directed by Kenneth Bainbridge, was conducted in the Jornada del Muerto desert about 35 miles (56 km) southeast of Socorro, New Mexico, on what was the Alamogordo Bombing and Gunnery Range (renamed the White Sands Proving Ground just before the test). The only structures originally in the immediate vicinity were the McDonald Ranch House and its ancillary buildings, which scientists used as a laboratory for testing bomb components. Fears of a fizzle prompted construction of "Jumbo", a steel containment vessel that could contain the plutonium, allowing it to be recovered; but ultimately Jumbo was not used in the test. On May 7, 1945, a rehearsal was conducted, during which 108 short tons (98 t) of high explosive spiked with radioactive isotopes was detonated. (Full article...)
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A ferrofluid on a glass plate, being affected by a rare-earth magnet
Image credit: Gregory Maxwell
A ferrofluid is a liquid which becomes strongly polarised in the presence of a magnetic field. Ferrofluids are composed of nanoscale ferromagnetic particles suspended in a carrier fluid, usually an organic solvent or water. The ferromagnetic nano-particles are coated with a surfactant to prevent their agglomeration (due to van der Waals and magnetic forces). Although the name may suggest otherwise, ferrofluids do not display ferromagnetism, since they do not retain magnetisation in the absence of an externally applied field. In fact, ferrofluids display paramagnetism, and are often referred as being "superparamagnetic" due to their large magnetic susceptibility. True ferromagnetic fluids are difficult to create at present.
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Glenn Theodore Seaborg (/ˈsiːbɔːrɡ/ SEE-borg; April 19, 1912 – February 25, 1999) was an American chemist whose involvement in the synthesis, discovery and investigation of ten transuranium elements earned him a share of the 1951 Nobel Prize in Chemistry. His work in this area also led to his development of the actinide concept and the arrangement of the actinide series in the periodic table of the elements.
Seaborg spent most of his career as an educator and research scientist at the University of California, Berkeley, serving as a professor, and, between 1958 and 1961, as the university's second chancellor. He advised ten US presidents—from Harry S. Truman to Bill Clinton—on nuclear policy and was Chairman of the United States Atomic Energy Commission from 1961 to 1971, where he pushed for commercial nuclear energy and the peaceful applications of nuclear science. Throughout his career, Seaborg worked for arms control. He was a signatory to the Franck Report and contributed to the Limited Test Ban Treaty, the Nuclear Non-Proliferation Treaty and the Comprehensive Test Ban Treaty. He was a well-known advocate of science education and federal funding for pure research. Toward the end of the Eisenhower administration, he was the principal author of the Seaborg Report on academic science, and, as a member of President Ronald Reagan's National Commission on Excellence in Education, he was a key contributor to its 1983 report "A Nation at Risk". (Full article...) -
Chien-Shiung Wu (Chinese: 吳健雄; pinyin: Wú Jiànxióng; Wade–Giles: Wu2 Chien4-shiung2; May 31, 1912 – February 16, 1997) was a Chinese-American particle and experimental physicist who made significant contributions in the fields of nuclear and particle physics. Wu worked on the Manhattan Project, where she helped develop the process for separating uranium into uranium-235 and uranium-238 isotopes by gaseous diffusion. She is best known for conducting the Wu experiment, which proved that parity is not conserved. This discovery resulted in her colleagues Tsung-Dao Lee and Chen-Ning Yang winning the 1957 Nobel Prize in Physics, while Wu herself was awarded the inaugural Wolf Prize in Physics in 1978. Her expertise in experimental physics evoked comparisons to Marie Curie. Her nicknames include the "First Lady of Physics", the "Chinese Madame Curie" and the "Queen of Nuclear Research". (Full article...) -
Emilio Gino Segrè (Italian: [seˈgrɛ]; 1 February 1905 – 22 April 1989) was an Italian and naturalized-American physicist and Nobel laureate, who discovered the elements technetium and astatine, and the antiproton, a subatomic antiparticle, for which he was awarded the Nobel Prize in Physics in 1959 along with Owen Chamberlain.
Born in Tivoli, near Rome, Segrè studied engineering at the University of Rome La Sapienza before taking up physics in 1927. Segrè was appointed assistant professor of physics at the University of Rome in 1932 and worked there until 1936, becoming one of the Via Panisperna boys. From 1936 to 1938 he was director of the Physics Laboratory at the University of Palermo. After a visit to Ernest O. Lawrence's Berkeley Radiation Laboratory, he was sent a molybdenum strip from the laboratory's cyclotron accelerator in 1937, which was emitting anomalous forms of radioactivity. Using careful chemical and theoretical analysis, Segrè was able to prove that some of the radiation was being produced by a previously unknown element, named technetium, the first artificially synthesized chemical element that does not occur in nature. (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...) -
Bruno Pontecorvo (Italian: [ponteˈkɔrvo]; Russian: Бру́но Макси́мович Понтеко́рво, Bruno Maksimovich Pontecorvo; 22 August 1913 – 24 September 1993) was an Italian–Russian nuclear physicist, an early assistant of Enrico Fermi and the author of numerous studies in high energy physics, especially on neutrinos. A convinced communist, he defected to the Soviet Union in 1950, where he continued his research on the decay of the muon and on neutrinos. The prestigious Pontecorvo Prize was instituted in his memory in 1995.
The fourth of eight children of a wealthy Jewish-Italian family, Pontecorvo studied physics at the Sapienza University, under Fermi, becoming the youngest of his Via Panisperna boys. In 1934 he participated in Fermi's famous experiment showing the properties of slow neutrons that led the way to the discovery of nuclear fission. He moved to Paris in 1936, where he conducted research under Irène and Frédéric Joliot-Curie. Influenced by his cousin, Emilio Sereni, he joined the Italian Communist Party, whose leader were in Paris as refugees, and as did his sisters Giuliana and Laura and brother Gillo. The Italian Fascist regime's 1938 racial laws against Jews caused his family members to leave Italy for Britain, France and the United States. (Full article...) -
PSR B1937+21 is a pulsar located in the constellation Vulpecula a few degrees in the sky away from the first discovered pulsar, PSR B1919+21. The name PSR B1937+21 is derived from the word "pulsar" and the declination and right ascension at which it is located, with the "B" indicating that the coordinates are for the 1950.0 epoch. PSR B1937+21 was discovered in 1982 by Don Backer, Shri Kulkarni, Carl Heiles, Michael Davis, and Miller Goss.
It is the first discovered millisecond pulsar, with a rotational period of 1.557708 milliseconds, meaning it completes almost 642 rotations per second. This period was far shorter than astronomers considered pulsars capable of reaching, and led to the suggestion that pulsars can be spun-up by accreting mass from a companion. (Full article...) -
A force is an influence that can cause an object to change its velocity unless counterbalanced by other forces. The concept of force makes the everyday notion of pushing or pulling mathematically precise. Because the magnitude and direction of a force are both important, force is a vector quantity. The SI unit of force is the newton (N), and force is often represented by the symbol F.
Force plays an important role in classical mechanics. The concept of force is central to all three of Newton's laws of motion. Types of forces often encountered in classical mechanics include elastic, frictional, contact or "normal" forces, and gravitational. The rotational version of force is torque, which produces changes in the rotational speed of an object. In an extended body, each part often applies forces on the adjacent parts; the distribution of such forces through the body is the internal mechanical stress. In equilibrium these stresses cause no acceleration of the body as the forces balance one another. If these are not in equilibrium they can cause deformation of solid materials, or flow in fluids. (Full article...) -
Ice is water that is frozen into a solid state, typically forming at or below temperatures of 0 °C, 32 °F, or 273.15 K. It occurs naturally on Earth, on other planets, in Oort cloud objects, and as interstellar ice. As a naturally occurring crystalline inorganic solid with an ordered structure, ice is considered to be a mineral. Depending on the presence of impurities such as particles of soil or bubbles of air, it can appear transparent or a more or less opaque bluish-white color.
Virtually all of the ice on Earth is of a hexagonal crystalline structure denoted as ice Ih (spoken as "ice one h"). Depending on temperature and pressure, at least nineteen phases (packing geometries) can exist. The most common phase transition to ice Ih occurs when liquid water is cooled below 0 °C (273.15 K, 32 °F) at standard atmospheric pressure. When water is cooled rapidly (quenching), up to three types of amorphous ice can form. Interstellar ice is overwhelmingly low-density amorphous ice (LDA), which likely makes LDA ice the most abundant type in the universe. When cooled slowly, correlated proton tunneling occurs below −253.15 °C (20 K, −423.67 °F) giving rise to macroscopic quantum phenomena. (Full article...) -
Figure 1. Steam devils on Lake Michigan 31 January 1971, from the paper which first named and reported the phenomenon.
A steam devil is a small, weak whirlwind over water (or sometimes wet land) that has drawn fog into the vortex, thus rendering it visible. They form over large lakes and oceans during cold air outbreaks while the water is still relatively warm, and can be an important mechanism in vertically transporting moisture. They are a component of sea smoke.
Smaller steam devils and steam whirls can form over geyser basins even in warm weather because of the very high water temperatures. Although observations of steam devils are generally quite rare, hot springs in Yellowstone Park produce them on a daily basis. (Full article...) -
As seen from the orbiting Earth, the Sun appears to move with respect to the fixed stars, and the ecliptic is the yearly path the Sun follows on the celestial sphere. This process repeats itself in a cycle lasting a little over 365 days.
The ecliptic or ecliptic plane is the orbital plane of Earth around the Sun. From the perspective of an observer on Earth, the Sun's movement around the celestial sphere over the course of a year traces out a path along the ecliptic against the background of stars. The ecliptic is an important reference plane and is the basis of the ecliptic coordinate system. (Full article...) -
Ernest Orlando Lawrence (August 8, 1901 – August 27, 1958) was an American nuclear physicist and laureate of 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...) -
Albert Einstein (/ˈaɪnstaɪn/, EYEN-styne; German: [ˈalbɛʁt ˈʔaɪnʃtaɪn] ⓘ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence formula E = mc2, which arises from special relativity, has been called "the world's most famous equation". He received the 1921 Nobel Prize in Physics forhis services to theoretical physics, and especially for his discovery of the law of the photoelectric effect
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Born in the German Empire, Einstein moved to Switzerland in 1895, forsaking his German citizenship (as a subject of the Kingdom of Württemberg) the following year. In 1897, at the age of seventeen he enrolled in the mathematics and physics teaching diploma program at the Swiss Federal Polytechnic School in Zurich, graduating in 1900. In 1901, he acquired Swiss citizenship. In 1903, he secured a permanent position at the Swiss Patent Office in Bern. In 1905, he submitted a successful PhD dissertation to the University of Zurich. In 1914, he moved to Berlin to join the Prussian Academy of Sciences and the Humboldt University of Berlin, becoming director of the Kaiser Wilhelm Institute for Physics in 1917; he also became a German citizen again, this time as a subject of the Kingdom of Prussia. In 1933, while Einstein was visiting the United States, Adolf Hitler came to power in Germany. Horrified by the Nazi persecution of his fellow Jews, he decided to remain in the US, and was granted American citizenship in 1940. On the eve of World War II, he endorsed a letter to President Franklin D. Roosevelt alerting him to the potential German nuclear weapons program and recommending that the US begin similar research. (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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Incoming wave (red) reflected at the wall produces the outgoing wave (blue), both being overlaid resulting in the clapotis (black).
In hydrodynamics, a clapotis (from French for "lapping of water") is a non-breaking standing wave pattern, caused for example, by the reflection of a traveling surface wave train from a near vertical shoreline like a breakwater, seawall or steep cliff.
The resulting clapotic wave does not travel horizontally, but has a fixed pattern of nodes and antinodes.
These waves promote erosion at the toe of the wall, and can cause severe damage to shore structures. The term was coined in 1877 by French mathematician and physicist Joseph Valentin Boussinesq who called these waves 'le clapotis' meaning "the lapping".
In the idealized case of "full clapotis" where a purely monotonic incoming wave is completely reflected normal to a solid vertical wall,
the standing wave height is twice the height of the incoming waves at a distance of one half wavelength from the wall.
In this case, the circular orbits of the water particles in the deep-water wave are converted to purely linear motion, with vertical velocities at the antinodes, and horizontal velocities at the nodes. (Full article...) -
Rendering of the LIFE.1 fusion power plant. The fusion system is in the large cylindrical containment building in the center.
LIFE, short for Laser Inertial Fusion Energy, was a fusion energy effort run at Lawrence Livermore National Laboratory between 2008 and 2013. LIFE aimed to develop the technologies necessary to convert the laser-driven inertial confinement fusion concept being developed in the National Ignition Facility (NIF) into a practical commercial power plant, a concept known generally as inertial fusion energy (IFE). LIFE used the same basic concepts as NIF, but aimed to lower costs using mass-produced fuel elements, simplified maintenance, and diode lasers with higher electrical efficiency.
Two designs were considered, operated as either a pure fusion or hybrid fusion-fission system. In the former, the energy generated by the fusion reactions is used directly. In the later, the neutrons given off by the fusion reactions are used to cause fission reactions in a surrounding blanket of uranium or other nuclear fuel, and those fission events are responsible for most of the energy release. In both cases, conventional steam turbine systems are used to extract the heat and produce electricity. (Full article...)
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December anniversaries
- 1610 – Galileo Galilei observes phases of Venus.
- 1900 - The peer reviewed journal "Nature" reports on Duddell's "Singing Arc" American Physical Society.
- 1942 - First self-sustained nuclear chain reaction at the University of Chicago under the supervision of Enrico Fermi. American Physical Society
- 1968 – Apollo 8 Launched
- 1995 – Hubble Deep Field images taken.
Births
- 1852 - Henri Becquerel
- 1900 - George Eugene Uhlenbeck
- 25 December, 1642 - Isaac Newton
- 5 December, 1901 - Werner Heisenberg
- 18 December, 1856 - J. J. Thomson
General images
The following are images from various physics-related articles on Wikipedia.
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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) -
William Thomson (Lord Kelvin)
(1824–1907) (from History of physics) -
Daniel Bernoulli (1700–1782) (from History of physics) -
Albert Einstein (1879–1955), photographed here in around 1905 (from History of physics) -
Chien-Shiung Wu worked on parity violation in 1956 and announced her results in January 1957. (from History of 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) -
The Polish astronomer Nicolaus Copernicus (1473–1543) is remembered for his development of a heliocentric model of the Solar System. (from History of physics) -
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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) -
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) -
René Descartes (1596–1650) (from History of physics) -
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Johannes Kepler.(1571–1630) (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) -
Max Planck (1858–1947) (from History of physics) -
The ancient Greek mathematician Archimedes, developer of ideas regarding fluid mechanics and buoyancy. (from History of physics) -
Galileo Galilei, early proponent of the modern scientific worldview and method (1564–1642) (from History of physics) -
The Standard Model (from History of physics) -
Heike Kamerlingh Onnes and Johannes van der Waals with the helium liquefactor at Leiden in 1908 (from Condensed matter physics) -
Ludwig Boltzmann (1844–1906) (from History of 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) -
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Werner Heisenberg (1901–1976) (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) -
Marie Skłodowska-Curie
(1867–1934) was awarded two Nobel prizes, Physics (1903) and Chemistry (1911) (from History of physics) -
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The quantum Hall effect: Components of the Hall resistivity as a function of the external magnetic field (from Condensed matter physics) -
Sir Isaac Newton (1642–1727) (from History of physics) -
Christiaan Huygens (1629–1695) (from History of physics) -
Gottfried Leibniz (1646–1716) (from History of physics) -
Alessandro Volta (1745–1827) (from History of physics) -
James Clerk Maxwell (1831–1879) (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) -
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) -
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) -
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) -
Richard Feynman's Los Alamos ID badge (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) -
Rudolf Clausius (1822–1888) (from History of physics) -
Image of X-ray diffraction pattern from a protein crystal (from Condensed matter physics) -
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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.
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