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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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J. Robert Oppenheimer (born Julius Robert Oppenheimer; /ˈɒpənhaɪmər/ OP-ən-hy-mər; April 22, 1904 – February 18, 1967) was an American theoretical physicist who served as the director of the Manhattan Project's Los Alamos Laboratory during World War II. He is often called the "father of the atomic bomb" for his role in overseeing the development of the first nuclear weapons.
Born in New York City, Oppenheimer obtained a degree in chemistry from Harvard University in 1925 and a doctorate in physics from the University of Göttingen in Germany in 1927, studying under Max Born. After research at other institutions, he joined the physics faculty at the University of California, Berkeley, where he was made a full professor in 1936. Oppenheimer made significant contributions to physics in the fields of quantum mechanics and nuclear physics, including the Born–Oppenheimer approximation for molecular wave functions; work on the theory of positrons, quantum electrodynamics, and quantum field theory; and the Oppenheimer–Phillips process in nuclear fusion. With his students, he also made major contributions to astrophysics, including the theory of cosmic ray showers, and the theory of neutron stars and black holes. (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?
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Image credit: Luc Viatour
Plasma lamps are a type of electrodeless gas-discharge lamp energized by radio frequency (RF) power. They are distinct from the novelty plasma lamps that were popular in the 1980s.
The internal-electrodeless lamp was invented by Nikola Tesla after his experimentation with high-frequency currents in evacuated glass tubes for the purposes of lighting and the study of high voltage phenomena. The first practical plasma lamps were the sulfur lamps manufactured by Fusion Lighting. This lamp suffered several practical problems and did not prosper commercially. Plasma lamps with an internal phosphor coating are called external electrode fluorescent lamps (EEFL); these external electrodes or terminal conductors provide the radio frequency electric field. (Full article...)
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These are Good articles, which meet a core set of high editorial standards.
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Water bead on a fabric that has been made non-wetting by chemical treatment.
Wetting is the ability of a liquid to displace gas to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. This happens in presence of a gaseous phase or another liquid phase not miscible with the first one. The degree of wetting (wettability) is determined by a force balance between adhesive and cohesive forces. There are two types of wetting: non-reactive wetting and reactive wetting.
Wetting is important in the bonding or adherence of two materials. Wetting and the surface forces that control wetting are also responsible for other related effects, including capillary effects. Surfactants can be used to increase the wetting power of a liquid like water. (Full article...) -
In 1850, Léon Foucault used a rotating mirror to perform a differential measurement of the speed of light in water versus its speed in air. In 1862, he used a similar apparatus to measure the speed of light in the air. (Full article...)
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Pythagoras of Samos (Ancient Greek: Πυθαγόρας; c. 570 – c. 495 BC) was an ancient Ionian Greek philosopher, polymath, and the eponymous founder of Pythagoreanism. His political and religious teachings were well known in Magna Graecia and influenced the philosophies of Plato, Aristotle, and, through them, the West in general. Knowledge of his life is clouded by legend; modern scholars disagree regarding Pythagoras's education and influences, but they do agree that, around 530 BC, he travelled to Croton in southern Italy, where he founded a school in which initiates were sworn to secrecy and lived a communal, ascetic lifestyle.
In antiquity, Pythagoras was credited with many mathematical and scientific discoveries, including the Pythagorean theorem, Pythagorean tuning, the five regular solids, the Theory of Proportions, the sphericity of the Earth, and the identity of the morning and evening stars as the planet Venus. It was said that he was the first man to call himself a philosopher ("lover of wisdom") and that he was the first to divide the globe into five climatic zones. Classical historians debate whether Pythagoras made these discoveries, and many of the accomplishments credited to him likely originated earlier or were made by his colleagues or successors. Some accounts mention that the philosophy associated with Pythagoras was related to mathematics and that numbers were important, but it is debated to what extent, if at all, he actually contributed to mathematics or natural philosophy. (Full article...) -
Hans Albrecht Bethe ForMemRS (German: [ˈhans ˈbeːtə] ; July 2, 1906 – March 6, 2005) was a German-American physicist who made major contributions to nuclear physics, astrophysics, quantum electrodynamics and solid-state physics, and won the 1967 Nobel Prize in Physics for his work on the theory of stellar nucleosynthesis. For most of his career, Bethe was a professor at Cornell University.
During World War II, he was head of the Theoretical Division at the secret Los Alamos laboratory that developed the first atomic bombs. There he played a key role in calculating the critical mass of the weapons and developing the theory behind the implosion method used in both the Trinity test and the "Fat Man" weapon dropped on Nagasaki in August 1945. (Full article...) -
Arthur Holly Compton (September 10, 1892 – March 15, 1962) was an American physicist who won the Nobel Prize in Physics in 1927 for his 1923 discovery of the Compton effect, which demonstrated the particle nature of electromagnetic radiation. It was a sensational discovery at the time: the wave nature of light had been well-demonstrated, but the idea that light had both wave and particle properties was not easily accepted. He is also known for his leadership over the Metallurgical Laboratory at the University of Chicago during the Manhattan Project, and served as chancellor of Washington University in St. Louis from 1945 to 1953.
In 1919, Compton was awarded one of the first two National Research Council Fellowships that allowed students to study abroad. He chose to go to the University of Cambridge's Cavendish Laboratory in England, where he studied the scattering and absorption of gamma rays. Further research along these lines led to the discovery of the Compton effect. He used X-rays to investigate ferromagnetism, concluding that it was a result of the alignment of electron spins, and studied cosmic rays, discovering that they were made up principally of positively charged particles. (Full article...) -
Val Logsdon Fitch (March 10, 1923 – February 5, 2015) was an American nuclear physicist who, with co-researcher James Cronin, was awarded the 1980 Nobel Prize in Physics for a 1964 experiment using the Alternating Gradient Synchrotron at Brookhaven National Laboratory that proved that certain subatomic reactions do not adhere to fundamental symmetry principles. Specifically, they proved, by examining the decay of K-mesons, that a reaction run in reverse does not retrace the path of the original reaction, which showed that the reactions of subatomic particles are not indifferent to time. Thus the phenomenon of CP violation was discovered. This demolished the faith that physicists had that natural laws were governed by symmetry.
Born on a cattle ranch near Merriman, Nebraska, Fitch was drafted into the U.S. Army during World War II, and worked on the Manhattan Project at the Los Alamos Laboratory in New Mexico. He later graduated from McGill University, and completed his PhD in physics in 1954 at Columbia University. He was a member of the faculty at Princeton University from 1954 until his retirement in 2005. (Full article...) -
Sir Rudolf Ernst Peierls, CBE FRS (/ˈpaɪ.ərlz/; German: [ˈpaɪɐls]; 5 June 1907 – 19 September 1995) was a German-born British physicist who played a major role in Tube Alloys, Britain's nuclear weapon programme, as well as the subsequent Manhattan Project, the combined Allied nuclear bomb programme. His 1996 obituary in Physics Today described him as "a major player in the drama of the eruption of nuclear physics into world affairs".
Peierls studied physics at the University of Berlin, at the University of Munich under Arnold Sommerfeld, the University of Leipzig under Werner Heisenberg, and ETH Zurich under Wolfgang Pauli. After receiving his DPhil from Leipzig in 1929, he became an assistant to Pauli in Zurich. In 1932, he was awarded a Rockefeller Fellowship, which he used to study in Rome under Enrico Fermi, and then at the Cavendish Laboratory at the University of Cambridge under Ralph H. Fowler. Because of his Jewish background, he elected to not return home after Adolf Hitler's rise to power in 1933, but to remain in Britain, where he worked with Hans Bethe at the Victoria University of Manchester, then at the Mond Laboratory at Cambridge. In 1937, Mark Oliphant, the newly appointed Australian professor of physics at the University of Birmingham recruited him for a new chair there in applied mathematics. (Full article...) -
Robert Fox Bacher (August 31, 1905 – November 18, 2004) was an American nuclear physicist and one of the leaders of the Manhattan Project. Born in Loudonville, Ohio, Bacher obtained his undergraduate degree and doctorate from the University of Michigan, writing his 1930 doctoral thesis under the supervision of Samuel Goudsmit on the Zeeman effect of the hyperfine structure of atomic levels. After graduate work at the California Institute of Technology (Caltech) and the Massachusetts Institute of Technology (MIT), he accepted a job at Columbia University. In 1935 he accepted an offer from Hans Bethe to work with him at Cornell University in Ithaca, New York. It was there that Bacher collaborated with Bethe on his book Nuclear Physics. A: Stationary States of Nuclei (1936), the first of three books that would become known as the "Bethe Bible".
In December 1940, Bacher joined the Radiation Laboratory at MIT, although he did not immediately cease his research at Cornell into the neutron cross section of cadmium. The Radiation Laboratory was organized into two sections, one for incoming radar signals, and one for outgoing radar signals. Bacher was appointed to handle the incoming signals section. Here he gained valuable experience in administration, coordinating not just the efforts of his scientists, but also those of General Electric and RCA. In 1942, Bacher was approached by Robert Oppenheimer to join the Manhattan Project at its new laboratory in Los Alamos, New Mexico. It was at Bacher's insistence that Los Alamos became a civilian rather than a military laboratory. At Los Alamos, Bacher headed the project's P (Physics) Division, and later its G (Gadget) Division. Bacher worked closely with Oppenheimer, and the two men discussed the project's progress on a daily basis. (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...) -
The nucleon magnetic moments are the intrinsic magnetic dipole moments of the proton and neutron, symbols μp and μn. The nucleus of an atom comprises protons and neutrons, both nucleons that behave as small magnets. Their magnetic strengths are measured by their magnetic moments. The nucleons interact with normal matter through either the nuclear force or their magnetic moments, with the charged proton also interacting by the Coulomb force.
The proton's magnetic moment was directly measured in 1933 by Otto Stern team in University of Hamburg. While the neutron was determined to have a magnetic moment by indirect methods in the mid-1930s, Luis Alvarez and Felix Bloch made the first accurate, direct measurement of the neutron's magnetic moment in 1940. The proton's magnetic moment is exploited to make measurements of molecules by proton nuclear magnetic resonance. The neutron's magnetic moment is exploited to probe the atomic structure of materials using scattering methods and to manipulate the properties of neutron beams in particle accelerators. (Full article...) -
A tau emerald (Hemicordulia tau) dragonfly has flight muscles attached directly to its wings.
Insects are the only group of invertebrates that have evolved wings and flight. Insects first flew in the Carboniferous, some 300 to 350 million years ago, making them the first animals to evolve flight. Wings may have evolved from appendages on the sides of existing limbs, which already had nerves, joints, and muscles used for other purposes. These may initially have been used for sailing on water, or to slow the rate of descent when gliding.
Two insect groups, the dragonflies and the mayflies, have flight muscles attached directly to the wings. In other winged insects, flight muscles attach to the thorax, which make it oscillate in order to induce the wings to beat. Of these insects, some (flies and some beetles) achieve very high wingbeat frequencies through the evolution of an "asynchronous" nervous system, in which the thorax oscillates faster than the rate of nerve impulses. (Full article...) -
Chanda Prescod-Weinstein (born c. 1982) is an American theoretical cosmologist and particle physicist at the University of New Hampshire. She is also an advocate of increasing diversity in science. (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...) -
Boyce Dawkins McDaniel (June 11, 1917 – May 8, 2002) was an American nuclear physicist who worked on the Manhattan Project and later directed the Cornell University Laboratory of Nuclear Studies (LNS). McDaniel was skilled in constructing "atom smashing" devices to study the fundamental structure of matter and helped to build the most powerful particle accelerators of his time. Together with his graduate student, he invented the pair spectrometer.
During World War II, McDaniel used his electronics expertise to help develop cyclotrons used to separate Uranium isotopes. McDaniel is also noted as having performed the final check on the first atomic bomb prior to its detonation in the Trinity test, during a lightning storm. (Full article...) -
Aristotle (‹See Tfd›Greek: Ἀριστοτέλης Aristotélēs; 384–322 BC) was an Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, and the arts. As the founder of the Peripatetic school of philosophy in the Lyceum in Athens, he began the wider Aristotelian tradition that followed, which set the groundwork for the development of modern science.
Little is known about Aristotle's life. He was born in the city of Stagira in northern Greece during the Classical period. His father, Nicomachus, died when Aristotle was a child, and he was brought up by a guardian. At around eighteen years old, he joined Plato's Academy in Athens and remained there until the age of thirty seven (c. 347 BC). Shortly after Plato died, Aristotle left Athens and, at the request of Philip II of Macedon, tutored his son Alexander the Great beginning in 343 BC. He established a library in the Lyceum, which helped him to produce many of his hundreds of books on papyrus scrolls. (Full article...)
November anniversaries
- 1952 - detonation of the first Hydrogen bomb, code named "Ivy Mike".
- 1947 - invention of the first transistor, between November 17 to December 23. APS.
- 1930 - Patent granted for Einstein-Szilard refrigerator designed by Albert Einstein and Leó Szilárd. APS.
- 1919 - Elmer Imes's published work presented the first accurate measurement of the distance between atoms in molecules with high resolution infrared spectroscopy. APS.
- 1915 – Einstein's presentation to the Prussian Academy of Science specifies how the geometry of space and time is influenced by whatever matter is present. (see: General relativity and APS)
- 1895 - Wilhelm Conrad Roentgen discovers X-rays.
- 1887 - Michelson–Morley experiment provided strong evidence against the luminiferous ether. APS.
- 1872 - death of Mary Somerville who gained an international reputation as a scientist in the intervals of raising a family of six children. APS
- 1783 - John Michell predicted the existence of black holes, and the possibility of a luminous twin to aid in detection. APS
- 1676 – using his first quantitative measurement of the speed of light, Ole Rømer accurately predicts the delay of eclipse of Io
Births
- 1934 – Carl Sagan
- 1932 - Melvin Schwartz
- 1929 - Richard E. Taylor
- 1925 - Simon van der Meer
- 1902 - Eugene Wigner
- 1837 - Johannes Diderik van der Waals
- 1867 - Marie Curie (Nov. 7)
- 1828 - Balfour Stewart
- 1878 - Lise Meitner (Nov. 7)
- 1887 - Henry Moseley
- 1888 - C V Raman (Nov. 7)
- 1892 - Dmitri Skobeltsyn (Nov. 24)
General images
The following are images from various physics-related articles on Wikipedia.
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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) -
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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Chien-Shiung Wu worked on parity violation in 1956 and announced her results in January 1957. (from History of physics) -
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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 cylindrical equirectangular projection. (from History of physics) -
William Thomson (Lord Kelvin)
(1824–1907) (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) -
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) -
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Sir Isaac Newton
(1642–1727) (from History of physics) -
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Image of X-ray diffraction pattern from a protein crystal (from Condensed matter physics) -
Heike Kamerlingh Onnes and Johannes van der Waals with the helium liquefactor at Leiden in 1908 (from Condensed matter physics) -
The ancient Greek mathematician Archimedes, developer of ideas regarding fluid mechanics and buoyancy. (from History of physics) -
The Standard Model (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) -
Richard Feynman's Los Alamos ID badge (from History of physics) -
Marie Skłodowska-Curie
(1867–1934) She was awarded two Nobel prizes, Physics (1903) and Chemistry (1911) (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) -
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) -
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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) -
A composite montage comparing Jupiter (lefthand side) and its four Galilean moons (top to bottom: Io, Europa, Ganymede, Callisto) (from History of physics) -
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Galileo Galilei, early proponent of the modern scientific worldview and method
(1564–1642) (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) -
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) -
Albert Einstein (1879–1955), photographed here in around 1905 (from History of physics) -
Christiaan Huygens
(1629–1695) (from History of physics) -
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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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Categories
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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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