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Newtonian approximation nazdineš-e Newtoni Fr.: approximation newtonienne A particular solution of the → general relativity when the → gravitational mass is small. The → space-time is then approximated to the → Minkowski's and this leads to → Newtonian mechanics. → Newtonian; → approximation. |
Newtonian constant of gravitation pâyâ-ye gerâneš-e Newton Fr.: constante de la gravitation newtonienne Same as the → gravitational constant. → Newtonian; → constant; → gravitation. |
Newtonian cosmology keyhânšenâsi-ye Newtoni Fr.: cosmologie newtonienne The use of → Newtonian mechanics to derive homogeneous and isotropic solutions of → Einstein's field equations, which represent models of expanding Universe. The Newtonian cosmology deviates from the prediction of → general relativity in the general case of anisotropic and inhomogeneous models. |
Newtonian fluid šârre-ye Newtoni Fr.: fluide newtonien Any → fluid with a constant → viscosity at a given temperature regardless of the rate of → shear. |
Newtonian focus kânun-e Newton, ~ Newtoni Fr.: foyer de Newton The focus obtained by diverting the converging light beam of a reflecting telescope to the side of the tube. |
Newtonian limit hadd-e Newtoni Fr.: limite newtonienne The limit attained by → general relativity when velocities are very smaller than the → speed of light or gravitational fields are weak. This limit corresponds to the transition between general relativity and the → Newtonian mechanics. See also → Newtonian approximation. |
Newtonian mechanics mekânik-e Newtoni (#) Fr.: mécanique newtonienne A system of mechanics based on → Newton's law of gravitation and its derivatives. Same as → classical mechanics. |
Newtonian potential tavand-e Newtoni Fr.: potentiel newtonien A potential in a field of force obeying the inverse-square law such as → gravitational potential. |
Newtonian principle of relativity parvaz-e bâzânigi-ye Newton Fr.: principe de relativité de Newton The Newton's equations of motion, if they hold in any → reference frame, they are valid also in any other reference frame moving with uniform velocity relative to the first. → Newtonian; → principle; → relativity. |
Newtonian relativity bâzânigi-ye Newtoni Fr.: relativité newtonienne The laws of physics are unchanged under → Galilean transformation. This implies that no mechanical experiment can detect any intrinsic diff between two → inertial frames. Same as → Galilean relativity. → Newton; → relativity. |
Newtonian telescope durbin-e Newton, teleskop-e ~ Fr.: télescope de Newton, ~ newtonien A telescope with a concave paraboloidal objective mirror and a small plane mirror that reflects rays from the primary mirror laterally outside the tube where the image is viewed with an eyepiece. |
overtone abarton (#) Fr.: harmonique A note of lesser intensity and higher frequency than the fundamental note, and superimposed upon the latter to give a note of characteristic quality. Overtones whose frequencies are an integral multiple of the fundamental are said to form a harmonic series. The fundamental with a frequency f1 is the first harmonic. The frequency 2f1 is the first overtone and so on. |
parton pârton (#) Fr.: parton In particle physics, a constituent of the hadron originally postulated in the theoretical analysis of high-energy scattering of particles off hadrons. In modern usage, the term parton is often used to mean a quark or a gluon. Coined by the American physicist Richard Feynman (1918-1988), from part, from → particle + → -ion |
Phaeton Phaeton Fr.: Phaéton A hypothetical → planet which once was postulated to have existed between the orbits of → Mars and → Jupiter and its destruction supposedly led to the formation of the → asteroid belt. The idea of such a hypothetical planet was first put forward by the German astronomer Heinrich Wilhelm Olbers (1758-1840). In Greek mythology Phaeton was the sun god Helios. Phaeton tried to drive his father's solar chariot but crashed after almost setting fire to the whole earth. |
phlogiston fložiston (#) Fr.: phlogiston A hypothetical substance that, prior to the discovery of → oxygen, was thought to be released during → combustion. → phlogiston theory. From New Latin, from Gk. phlogiston, neuter of phlogistos "inflammable, burnt up," from phlogizein "to set on fire, burn," from phlox "flame, blaze;" from PIE root *bhel- "to shine, burn." Fložiston, loan from Fr, as above. |
phlogiston theory negare-ye fložiston Fr.: phlogistique An obsolete theory of combustion in which all flammable objects were supposed to contain a substance called → phlogiston, which was released when the object burned. The existence of this hypothetical substance was proposed in 1669 by Johann Becher, who called it terra pinguis "fat earth." For example, as wood burns it releases phlogiston into the air, leaving ash behind. Ash was therefore wood minus phlogiston. In the early 18th century Georg Stahl renamed the substance phlogiston. The theory was disproved by Antoine Lavoisier in 1783, who proved the principle of conservation of mass, refuted the phlogiston theory and proposed the oxygen theory of burning. → phlogiston; → theory. |
photon foton (#) Fr.: photon The → quantum of the → electromagnetic field, which mediates the interaction between charged particles. It is the mass-less → boson with zero → electric charge, which propagates with the → speed of light in vacuum. The energy of a photon is connected to its → frequency ν, through the formula E = hν, where h is → Planck's constant. From phot-, variant of → photo- before a vowel + → -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon, graviton), and other minimal entities or components. The term photon was coined by Gilbert N. Lewis in 1926 in a letter to the editor of Nature magazine (Vol. 118, Part 2, December 18, page 874). |
photon escape time zamân-e goriz-e foton Fr.: temps d'échappement des photons The time required for a photon created in the Sun's core to attain the → photosphere and leave the Sun. If the photons were free to escape, they would take a time of only R/c (a couple of seconds) to reach the surface, where R is the Solar radius and c the speed of light. The solar material is, however, very opaque, so that photons travel only a short distance before interacting with other particles. Therefore, photons undergo a very large number of → random walks before arriving at the surface by chance. The typical time is approximately 5 x 104 years for a constant density Sun. |
photon gas gâz-e fotoni Fr.: gaz de photons → Electromagnetic radiation in equilibrium in a → black body cavity. Photons can be treated as the simplest → ideal gas because all the particles move at the same velocity, the → speed of light. There are, nevertheless, two main differences. 1) Photons are → bosons and → Bose-Einstein statistics must be used. However, photons do not interact with each others so that no approximation is made by neglecting inter-particle forces. 2) Some photons scatter off the walls, with some being absorbed and new ones being emitted continually; so that no constraint can be placed on their number. |
photon hardening saxteš-e foton Fr.: durcissement des photons An effect occurring in the outer zones of → H II regions where the number of high-energy ultraviolet photons with energies well above the → ionization potential of hydrogen increases with respect to the number of → Lyman continuum photons. The effect is due to stronger absorption of weaker photons. |
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