Système universitaire de documentation
The système universitaire de documentation or SUDOC is a system used by the libraries of French universities and higher education establishments to identify and manage the documents in their possession. The catalog, which contains more than 10 million references, allows students and researcher to search for bibliographical and location information in over 3,400 documentation centers, it is maintained by the Bibliographic Agency for Higher Education. Official website
Not to be confused with the Rumford Prize The Rumford Medal is an award bestowed by Britain's Royal Society every alternating year for "an outstandingly important recent discovery in the field of thermal or optical properties of matter made by a scientist working in Europe". First awarded during 1800, it was created after a 1796 donation of $5000 by the scientist Benjamin Thompson, known as Count Rumford, is accompanied by a gift of £1000. Since its inception, the award has been granted to 101 scientists, including Rumford himself during 1800, it has been awarded to citizens of the United Kingdom fifty-four times, Germany seventeen times, France fourteen times, the Netherlands seven times, Sweden four times, the United States three times, Italy twice and once each to citizens of Australia, Belgium and New Zealand. General "The Rumford Medal". Specific
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy. It includes radio waves, infrared, ultraviolet, X-rays, gamma rays. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields that propagate at the speed of light, which, in a vacuum, is denoted c. In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave; the wavefront of electromagnetic waves emitted from a point source is a sphere. The position of an electromagnetic wave within the electromagnetic spectrum can be characterized by either its frequency of oscillation or its wavelength. Electromagnetic waves of different frequency are called by different names since they have different sources and effects on matter. In order of increasing frequency and decreasing wavelength these are: radio waves, infrared radiation, visible light, ultraviolet radiation, X-rays and gamma rays.
Electromagnetic waves are emitted by electrically charged particles undergoing acceleration, these waves can subsequently interact with other charged particles, exerting force on them. EM waves carry energy and angular momentum away from their source particle and can impart those quantities to matter with which they interact. Electromagnetic radiation is associated with those EM waves that are free to propagate themselves without the continuing influence of the moving charges that produced them, because they have achieved sufficient distance from those charges. Thus, EMR is sometimes referred to as the far field. In this language, the near field refers to EM fields near the charges and current that directly produced them electromagnetic induction and electrostatic induction phenomena. In quantum mechanics, an alternate way of viewing EMR is that it consists of photons, uncharged elementary particles with zero rest mass which are the quanta of the electromagnetic force, responsible for all electromagnetic interactions.
Quantum electrodynamics is the theory of. Quantum effects provide additional sources of EMR, such as the transition of electrons to lower energy levels in an atom and black-body radiation; the energy of an individual photon is greater for photons of higher frequency. This relationship is given by Planck's equation E = hν, where E is the energy per photon, ν is the frequency of the photon, h is Planck's constant. A single gamma ray photon, for example, might carry ~100,000 times the energy of a single photon of visible light; the effects of EMR upon chemical compounds and biological organisms depend both upon the radiation's power and its frequency. EMR of visible or lower frequencies is called non-ionizing radiation, because its photons do not individually have enough energy to ionize atoms or molecules or break chemical bonds; the effects of these radiations on chemical systems and living tissue are caused by heating effects from the combined energy transfer of many photons. In contrast, high frequency ultraviolet, X-rays and gamma rays are called ionizing radiation, since individual photons of such high frequency have enough energy to ionize molecules or break chemical bonds.
These radiations have the ability to cause chemical reactions and damage living cells beyond that resulting from simple heating, can be a health hazard. James Clerk Maxwell derived a wave form of the electric and magnetic equations, thus uncovering the wave-like nature of electric and magnetic fields and their symmetry; because the speed of EM waves predicted by the wave equation coincided with the measured speed of light, Maxwell concluded that light itself is an EM wave. Maxwell's equations were confirmed by Heinrich Hertz through experiments with radio waves. According to Maxwell's equations, a spatially varying electric field is always associated with a magnetic field that changes over time. A spatially varying magnetic field is associated with specific changes over time in the electric field. In an electromagnetic wave, the changes in the electric field are always accompanied by a wave in the magnetic field in one direction, vice versa; this relationship between the two occurs without either type of field causing the other.
In fact, magnetic fields can be viewed as electric fields in another frame of reference, electric fields can be viewed as magnetic fields in another frame of reference, but they have equal significance as physics is the same in all frames of reference, so the close relationship between space and time changes here is more than an analogy. Together, these fields form a propagating electromagnetic wave, which moves out into space and need never again interact with the source; the distant EM field formed in this way by the acceleration of a charge carries energy with it that "radiates" away through space, hence the term. Maxwell's equations established that some charges and currents produce a local type of electromagnetic field near them that does not have the behaviour of EMR. Currents directly produce a magnetic field, but it is of a magnetic dipole type that dies out with distance from the current. In a similar manner, moving charges pushed apart in a conductor by a changing electrical potential produce an electric dipole type electric
Physics is the natural science that studies matter, its motion, behavior through space and time, that studies the related entities of energy and force. Physics is one of the most fundamental scientific disciplines, its main goal is to understand how the universe behaves. Physics is one of the oldest academic disciplines and, through its inclusion of astronomy the oldest. Over much of the past two millennia, chemistry and certain branches of mathematics, were a part of natural philosophy, but during the scientific revolution in the 17th century these natural sciences emerged as unique research endeavors in their own right. Physics intersects with many interdisciplinary areas of research, such as biophysics and quantum chemistry, the boundaries of physics which are not rigidly defined. New ideas in physics explain the fundamental mechanisms studied by other sciences and suggest new avenues of research in academic disciplines such as mathematics and philosophy. Advances in physics enable advances in new technologies.
For example, advances in the understanding of electromagnetism and nuclear physics led directly to the development of new products that have transformed modern-day society, such as television, domestic appliances, nuclear weapons. Astronomy is one of the oldest natural sciences. Early civilizations dating back to beyond 3000 BCE, such as the Sumerians, ancient Egyptians, the Indus Valley Civilization, had a predictive knowledge and a basic understanding of the motions of the Sun and stars; the stars and planets were worshipped, believed to represent gods. While the explanations for the observed positions of the stars were unscientific and lacking in evidence, these early observations laid the foundation for astronomy, as the stars were found to traverse great circles across the sky, which however did not explain the positions of the planets. According to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia, all Western efforts in the exact sciences are descended from late Babylonian astronomy.
Egyptian astronomers left monuments showing knowledge of the constellations and the motions of the celestial bodies, while Greek poet Homer wrote of various celestial objects in his Iliad and Odyssey. Natural philosophy has its origins in Greece during the Archaic period, when pre-Socratic philosophers like Thales rejected non-naturalistic explanations for natural phenomena and proclaimed that every event had a natural cause, they proposed ideas verified by reason and observation, many of their hypotheses proved successful in experiment. The Western Roman Empire fell in the fifth century, this resulted in a decline in intellectual pursuits in the western part of Europe. By contrast, the Eastern Roman Empire resisted the attacks from the barbarians, continued to advance various fields of learning, including physics. In the sixth century Isidore of Miletus created an important compilation of Archimedes' works that are copied in the Archimedes Palimpsest. In sixth century Europe John Philoponus, a Byzantine scholar, questioned Aristotle's teaching of physics and noting its flaws.
He introduced the theory of impetus. Aristotle's physics was not scrutinized until John Philoponus appeared, unlike Aristotle who based his physics on verbal argument, Philoponus relied on observation. On Aristotle's physics John Philoponus wrote: “But this is erroneous, our view may be corroborated by actual observation more than by any sort of verbal argument. For if you let fall from the same height two weights of which one is many times as heavy as the other, you will see that the ratio of the times required for the motion does not depend on the ratio of the weights, but that the difference in time is a small one, and so, if the difference in the weights is not considerable, that is, of one is, let us say, double the other, there will be no difference, or else an imperceptible difference, in time, though the difference in weight is by no means negligible, with one body weighing twice as much as the other”John Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries during the Scientific Revolution.
Galileo cited Philoponus in his works when arguing that Aristotelian physics was flawed. In the 1300s Jean Buridan, a teacher in the faculty of arts at the University of Paris, developed the concept of impetus, it was a step toward the modern ideas of momentum. Islamic scholarship inherited Aristotelian physics from the Greeks and during the Islamic Golden Age developed it further placing emphasis on observation and a priori reasoning, developing early forms of the scientific method; the most notable innovations were in the field of optics and vision, which came from the works of many scientists like Ibn Sahl, Al-Kindi, Ibn al-Haytham, Al-Farisi and Avicenna. The most notable work was The Book of Optics, written by Ibn al-Haytham, in which he conclusively disproved the ancient Greek idea about vision, but came up with a new theory. In the book, he presented a study of the phenomenon of the camera obscura (his thousand-year-old
Thermal expansion is the tendency of matter to change its shape and volume in response to a change in temperature. Temperature is a monotonic function of the average molecular kinetic energy of a substance; when a substance is heated, the kinetic energy of its molecules increases. Thus, the molecules begin vibrating/moving more and maintain a greater average separation. Materials which contract with increasing temperature are unusual; the relative expansion divided by the change in temperature is called the material's coefficient of thermal expansion and varies with temperature. If an equation of state is available, it can be used to predict the values of the thermal expansion at all the required temperatures and pressures, along with many other state functions. A number of materials contract on heating within certain temperature ranges. For example, the coefficient of thermal expansion of water drops to zero as it is cooled to 3.983 °C and becomes negative below this temperature. Pure silicon has a negative coefficient of thermal expansion for temperatures between about 18 and 120 kelvins.
Unlike gases or liquids, solid materials tend to keep their shape. Thermal expansion decreases with increasing bond energy, which has an effect on the melting point of solids, so, high melting point materials are more to have lower thermal expansion. In general, liquids expand more than solids; the thermal expansion of glasses is higher compared to that of crystals. At the glass transition temperature, rearrangements that occur in an amorphous material lead to characteristic discontinuities of coefficient of thermal expansion and specific heat; these discontinuities allow detection of the glass transition temperature where a supercooled liquid transforms to a glass. Absorption or desorption of water can change the size of many common materials. Common plastics exposed to water can, in the long term, expand by many percent; the coefficient of thermal expansion describes how the size of an object changes with a change in temperature. It measures the fractional change in size per degree change in temperature at a constant pressure.
Several types of coefficients have been developed: volumetric and linear. The choice of coefficient depends on the particular application and which dimensions are considered important. For solids, one might only be concerned over some area; the volumetric thermal expansion coefficient is the most basic thermal expansion coefficient, the most relevant for fluids. In general, substances expand or contract when their temperature changes, with expansion or contraction occurring in all directions. Substances that expand at the same rate in every direction are called isotropic. For isotropic materials, the area and volumetric thermal expansion coefficient are approximately twice and three times larger than the linear thermal expansion coefficient. Mathematical definitions of these coefficients are defined below for solids and gases. In the general case of a gas, liquid, or solid, the volumetric coefficient of thermal expansion is given by α V = 1 V p The subscript p indicates that the pressure is held constant during the expansion, the subscript V stresses that it is the volumetric expansion that enters this general definition.
In the case of a gas, the fact that the pressure is held constant is important, because the volume of a gas will vary appreciably with pressure as well as temperature. For a gas of low density this can be seen from the ideal gas law; when calculating thermal expansion it is necessary to consider whether the body is free to expand or is constrained. If the body is free to expand, the expansion or strain resulting from an increase in temperature can be calculated by using the applicable coefficient of Thermal Expansion. If the body is constrained so that it cannot expand internal stress will be caused by a change in temperature; this stress can be calculated by considering the strain that would occur if the body were free to expand and the stress required to reduce that strain to zero, through the stress/strain relationship characterised by the elastic or Young's modulus. In the special case of solid materials, external ambient pressure does not appreciably affect the size of an object and so it is not necessary to consider the effect of pressure changes.
Common engineering solids have coefficients of thermal expansion that do not vary over the range of temperatures where they are designed to be used, so where high accuracy is not required, practical calculations can be based on a constant, value of the coefficient of expansion. Linear expansion means change in one dimension as opposed to change in volume. To a first approximation, the change in length measurements of an object due to thermal expansion is related to temperature change by a "Coefficient of linear th
Jean Bernard Léon Foucault was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation. He made an early measurement of the speed of light, discovered eddy currents, is credited with naming the gyroscope. Foucault was the son of a publisher in Paris, where he was born on 18 September 1819. After an education received chiefly at home, he studied medicine, which he abandoned in favour of physics due to a blood phobia, he first directed his attention to the improvement of Louis Daguerre's photographic processes. For three years he was experimental assistant to Alfred Donné in his course of lectures on microscopic anatomy. With Hippolyte Fizeau he carried out a series of investigations on the intensity of the light of the sun, as compared with that of carbon in the arc lamp, of lime in the flame of the oxyhydrogen blowpipe. In 1849, Foucault experimentally demonstrated that absorption and emission lines appearing at the same wavelength are both due to the same material, with the difference between the two originating from the temperature of the light source.
In 1850, he did an experiment using the Fizeau–Foucault apparatus to measure the speed of light. In 1851, he provided an experimental demonstration of the rotation of the Earth on its axis; this experimental setup had been used by Vincenzo Viviani but became well known to the public by Foucault's work. Foucault achieved the demonstration by showing the rotation of the plane of oscillation of a long and heavy pendulum suspended from the roof of the Panthéon, Paris; the experiment caused a sensation in both the learned and popular worlds, "Foucault pendulums" were suspended in major cities across Europe and America and attracted crowds. In the following year he used the gyroscope as a conceptually simpler experimental proof. In 1855, he received the Copley Medal of the Royal Society for his'very remarkable experimental researches'. Earlier in the same year he was made physicien at the imperial observatory at Paris. In September 1855 he discovered that the force required for the rotation of a copper disc becomes greater when it is made to rotate with its rim between the poles of a magnet, the disc at the same time becoming heated by the eddy current or "Foucault currents" induced in the metal.
In 1857 Foucault invented the polarizer which bears his name, in the succeeding year devised a method of testing the mirror of a reflecting telescope to determine its shape. The so-called "Foucault knife-edge test" allows the worker to tell if the mirror is spherical or has non-spherical deviation in its figure. Prior to Foucault's publication of his findings, the testing of reflecting telescope mirrors was a "hit or miss" proposition. Foucault's knife edge test determines the shape of a mirror by finding the focal lengths of its areas called zones and measured from the mirror center. In the test, light from a point source is focused onto the center of curvature of the mirror and reflected back to a knife edge; the test enables the tester to quantify the conic section of the mirror, thereby allowing the tester to validate the actual shape of the mirror, necessary to obtain optimal performance of the optical system. The Foucault test is in use to this date, most notably by amateur and smaller commercial telescope makers as it is inexpensive and uses simple made equipment.
With Charles Wheatstone’s revolving mirror he, in 1862, determined the speed of light to be 298,000 km/s – 10,000 km/s less than that obtained by previous experimenters and only 0.6% in error of the accepted value. In 1862 Foucault was made a member of the Bureau des Longitudes and an officer of the Legion of Honour, he became a member of the Royal Society of London in 1864, member of the mechanical section of the Institute a year later. In 1865 he published his papers on a modification of James Watt's centrifugal governor. Foucault showed how, by the deposition of a transparently thin film of silver on the outer side of the object glass of a telescope, the sun could be viewed without injuring the eye, his chief scientific papers are to be found in the Comptes Rendus, 1847–1869. Near his death he returned to Roman Catholicism that he abandoned. Foucault died of what was a developing case of multiple sclerosis on 11 February 1868 in Paris and was buried in the Montmartre Cemetery; the asteroid 5668 Foucault was named for him.
His is one of the 72 names inscribed on the Eiffel Tower. Collected Works: Recueil des travaux scientifiques de Léon Foucault Volume One, Volume Two, 1878. Or Internet Archive Donné & Foucault Atlas of medical micrographs 1845 Amir D. Aczel, Pendulum: Léon Foucault and the Triumph of Science, Washington Square Press, 2003, ISBN 0-7434-6478-8 Umberto Eco, Foucault's Pendulum. Secker & Warburg, 1989. William Tobin, Perfecting the Modern Reflector. Sky & Telescope, October 1987. William Tobin, Evolution of the Foucault-Secretan Reflecting Telescope. Journal of Astronomical History and Heritage, 19, 106-184 pdf & 361-362 pdf, 2016. William Tobin, Léon Foucault. Scientific American, July