Sigmund Freud Sigmund Freud (/frɔɪd/; German pronunciation: [ˈziːkmʊnt ˈfʁɔʏ̯t]; born Sigismund Schlomo Freud; 6 May 1856 – 23 September 1939) was an Austrian neurologist, now known as the father of psychoanalysis. Freud qualified as a doctor of medicine at the University of Vienna in 1881, and then carried out research into cerebral palsy, aphasia and microscopic neuroanatomy at the Vienna General Hospital. Upon completing his habilitation in 1895, he was appointed a docent in neuropathology in the same year and became an affiliated professor (professor extraordinarius) in 1902. Psychoanalysis remains influential within psychotherapy, within some areas of psychiatry, and across the humanities. As such, it continues to generate extensive and highly contested debate with regard to its therapeutic efficacy, its scientific status, and whether it advances or is detrimental to the feminist cause. Nonetheless, Freud's work has suffused contemporary Western thought and popular culture.
Matter wave The de Broglie relations redirect here. In quantum mechanics, the concept of matter waves or de Broglie waves /dəˈbrɔɪ/ reflects the wave–particle duality of matter. The theory was proposed by Louis de Broglie in 1924 in his PhD thesis. The de Broglie relations show that the wavelength is inversely proportional to the momentum of a particle and is also called de Broglie wavelength. Historical context At the end of the 19th century, light was thought to consist of waves of electromagnetic fields which propagated according to Maxwell’s equations, while matter was thought to consist of localized particles (See history of wave and particle viewpoints). where is the frequency of the light and h is Planck’s constant. In 1926, Erwin Schrödinger published an equation describing how this matter wave should evolve—the matter wave equivalent of Maxwell’s equations—and used it to derive the energy spectrum of hydrogen. de Broglie relations Quantum mechanics using the definitions
Relativistic Doppler effect Diagram 1. A source of light waves moving to the right, relative to observers, with velocity 0.7c. The frequency is higher for observers on the right, and lower for observers on the left. The relativistic Doppler effect is the change in frequency (and wavelength) of light, caused by the relative motion of the source and the observer (as in the classical Doppler effect), when taking into account effects described by the special theory of relativity. The relativistic Doppler effect is different from the non-relativistic Doppler effect as the equations include the time dilation effect of special relativity and do not involve the medium of propagation as a reference point. They describe the total difference in observed frequencies and possess the required Lorentz symmetry. Visualization In Diagram 2, the blue point represents the observer, and the arrow represents the observer's velocity vector. Diagram 3. Analogy Motion along the line of sight away from him (where where and . to
Minkowski diagram Minkowski diagram with resting frame (x,t), moving frame (x′,t′), light cone, and hyperbolas marking out time and space with respect to the origin. The Minkowski diagram, also known as a spacetime diagram, was developed in 1908 by Hermann Minkowski and provides an illustration of the properties of space and time in the special theory of relativity. It allows a quantitative understanding of the corresponding phenomena like time dilation and length contraction without mathematical equations. The term Minkowski diagram is used in both a generic and particular sense. Basics A photon moving right at the origin corresponds to the yellow track of events, a straight line with a slope of 45°. For simplification in Minkowski diagrams, usually only events in a universe of one space dimension and one time dimension are considered. Each point in the diagram represents a certain position in space and time. Path-time diagram in Newtonian physics Minkowski diagram in special relativity and
Cubism A primary influence that led to Cubism was the representation of three-dimensional form in the late works of Paul Cézanne, which were displayed in a retrospective at the 1907 Salon d'Automne. In Cubist artwork, objects are analyzed, broken up and reassembled in an abstracted form—instead of depicting objects from one viewpoint, the artist depicts the subject from a multitude of viewpoints to represent the subject in a greater context. Conception and origins Pablo Picasso, 1909-10, Figure dans un Fauteuil (Seated Nude, Femme nue assise), oil on canvas, 92.1 x 73 cm, Tate Modern, London Cubism began between 1907 and 1911. By 1911 Picasso was recognized as the inventor of Cubism, while Braque’s importance and precedence was argued later, with respect to his treatment of space, volume and mass in the L’Estaque landscapes. John Berger identifies the essence of Cubism with the mechanical diagram. Technical and stylistic aspects "M. Cubism before 1914
Energy All of the many forms of energy are convertible to other kinds of energy, and obey the conservation of energy. Common energy forms include the kinetic energy of a moving object, the radiant energy carried by light, the potential energy stored by an object's position in a force field,(gravitational, electric or magnetic) elastic energy stored by stretching solid objects, chemical energy released when a fuel burns, and the thermal energy due to an object's temperature. According to mass–energy equivalence, any object that has mass when stationary,(called rest mass) also has an equivalent amount of energy whose form is called rest energy. Conversely, any additional energy above the rest energy will increase an object's mass. Living organisms require available energy to stay alive, such as the energy humans get from food. Forms Heat and work are special cases in that they are not properties of systems, but are instead properties of processes that transfer energy. History Measurement and units
Maxwell's equations Maxwell's equations are a set of partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These fields in turn underlie modern electrical and communications technologies. Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents. They are named after the Scottish physicist and mathematician James Clerk Maxwell, who published an early form of those equations between 1861 and 1862. The equations have two major variants. The term "Maxwell's equations" is often used for other forms of Maxwell's equations. Since the mid-20th century, it has been understood that Maxwell's equations are not exact laws of the universe, but are a classical approximation to the more accurate and fundamental theory of quantum electrodynamics. Formulation in terms of electric and magnetic fields Flux and divergence
Twin paradox In physics, the twin paradox is a thought experiment in special relativity involving identical twins, one of whom makes a journey into space in a high-speed rocket and returns home to find that the twin who remained on Earth has aged more. This result appears puzzling because each twin sees the other twin as traveling, and so, according to an incorrect naive application of time dilation, each should paradoxically find the other to have aged more slowly. However, this scenario can be resolved within the standard framework of special relativity: Acceleration is not relative, unlike position and velocity, and one twin is accelerated more than the other. Starting with Paul Langevin in 1911, there have been numerous explanations of this paradox, many based upon there being no contradiction because there is no symmetry—only one twin has undergone acceleration and deceleration, thus differentiating the two cases. History Max von Laue (1911, 1913) elaborated on Langevin's explanation.
Fauvism Artists and style Press clipping, Les Fauves: Exhibition at the Salon d'Automne, in L'Illustration, 4 November 1905 Besides Matisse and Derain, other artists included Albert Marquet, Charles Camoin, Louis Valtat, the Belgian painter Henri Evenepoel, Maurice Marinot, Jean Puy, Maurice de Vlaminck, Henri Manguin, Raoul Dufy, Othon Friesz, Georges Rouault, Jean Metzinger, the Dutch painter Kees van Dongen and Georges Braque (subsequently Picasso's partner in Cubism). The paintings of the Fauves were characterized by seemingly wild brush work and strident colors, while their subject matter had a high degree of simplification and abstraction. Fauvism can be classified as an extreme development of Van Gogh's Post-Impressionism fused with the pointillism of Seurat and other Neo-Impressionist painters, in particular Paul Signac. Fauvism can also be seen as a mode of Expressionism. Origins Salon D'Automne 1905 Gallery See also Notes and references
Kinetic energy In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is . In relativistic mechanics, this is only a good approximation when v is much less than the speed of light. History and etymology The adjective kinetic has its roots in the Greek word κίνησις (kinesis) meaning motion. The dichotomy between kinetic energy and potential energy can be traced back to Aristotle's concepts of actuality and potentiality. The principle in classical mechanics that E ∝ mv² was first developed by Gottfried Leibniz and Johann Bernoulli, who described kinetic energy as the living force, vis viva. The terms kinetic energy and work in their present scientific meanings date back to the mid-19th century. Introduction Energy occurs in many forms, including chemical energy, thermal energy, electromagnetic radiation, gravitational energy, electric energy, elastic energy, nuclear energy, and rest energy. Kinetic energy can be passed from one object to another. .
Kennedy–Thorndike experiment Figure 1. The Kennedy–Thorndike experiment Improved variants of the Kennedy–Thorndike experiment have been conducted using optical cavities or Lunar Laser Ranging. For a general overview of tests of Lorentz invariance, see Tests of special relativity. The experiment The original Michelson–Morley experiment was useful for testing the Lorentz–FitzGerald contraction hypothesis only. The principle on which this experiment is based is the simple proposition that if a beam of homogeneous light is split […] into two beams which after traversing paths of different lengths are brought together again, then the relative phases […] will depend […] on the velocity of the apparatus unless the frequency of the light depends […] on the velocity in the way required by relativity. Referring to Fig. 1, key optical components were mounted within vacuum chamber V on a fused quartz base of extremely low coefficient of thermal expansion. Theory Basic theory of the experiment Figure 2. where
Do Frequent Fliers Age More Slowly Is it just me, or is this flight taking forever? [Credit: MarinaAvila, flickr.com] You’re squeezed into a middle seat, two rows from the back of the plane. It’s barely two hours into your cross-country flight, though you’d swear it’s been longer. Does it just seem like the minutes of your trip are crawling by — or does time actually pass more slowly for people who are mid-flight than for people on the ground? Many of us have heard the idea that time doesn’t pass at the same rate for everyone. This familiar — and paradoxical — plotline comes from a particular tenet of relativity theory known as time dilation. Scientists have shown that time dilation doesn’t just happen on near-speed-of-light journeys. So if time dilation occurs under these everyday conditions, is the slowed-down aging experienced by the space-faring twin also experienced — in a much subtler way — by that more familiar airborne traveler, the frequent flier?
Impressionism Impressionism is a 19th-century art movement that originated with a group of Paris-based artists. Their independent exhibitions brought them to prominence during the 1870s and 1880s, in spite of harsh opposition from the conventional art community in France. The name of the style derives from the title of a Claude Monet work, Impression, soleil levant (Impression, Sunrise), which provoked the critic Louis Leroy to coin the term in a satirical review published in the Parisian newspaper Le Charivari. Overview Radicals in their time, early Impressionists violated the rules of academic painting. Impressionism emerged in France at the same time that a number of other painters, including the Italian artists known as the Macchiaioli, and Winslow Homer in the United States, were also exploring plein-air painting. Beginnings In the middle of the 19th century—a time of change, as Emperor Napoleon III rebuilt Paris and waged war—the Académie des Beaux-Arts dominated French art.
Quantum mechanics Wavefunctions of the electron in a hydrogen atom at different energy levels. Quantum mechanics cannot predict the exact location of a particle in space, only the probability of finding it at different locations. The brighter areas represent a higher probability of finding the electron. Quantum mechanics (QM; also known as quantum physics, quantum theory, the wave mechanical model, or matrix mechanics), including quantum field theory, is a fundamental theory in physics which describes nature at the smallest scales of energy levels of atoms and subatomic particles. Quantum mechanics gradually arose from theories to explain observations which could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and from the correspondence between energy and frequency in Albert Einstein's 1905 paper which explained the photoelectric effect. History In 1838, Michael Faraday discovered cathode rays. where h is Planck's constant.