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grating efficiency kârâyi-ye turi (#) Fr.: efficacité de réseau The measure of the light intensity diffracted from a grating. → grating; → efficiency. |
grating groove šiyâr-e turi (#) Fr.: trait du réseau, sillon ~ ~ One of thousands of long, narrow indentations in the surface of a → diffraction grating. |
gravitate gerânidan (#) Fr.: graviter To move or tend to move under the influence of gravitational force. From L. gravitatus, p.p. of gravitâre, from gravis "heavy," → gravity. Gerânidan, infinitive of gerân, → gravity. |
gravitation gerâneš (#) Fr.: gravitation 1) The universal phenomenon of attraction between material bodies.
→ Newton's law of gravitation. Verbal noun of → gravitate. |
gravitational gerâneši (#) Fr.: gravitationnel Of or relating to or caused by → gravitation. Adj. of → gravitation. |
gravitational acceleration šetâb-e gerâneši (#) Fr.: accélération gravitationnelle The acceleration caused by the force of gravity. At the Earth's surface it is determined by the distance of the object form the center of the Earth: g = GM/R^{2}, where G is the → gravitational constant, and M and R are the Earth's mass and radius respectively. It is approximately equal to 9.8 m s^{-2}. The value varies slightly with latitude and elevation. Also known as the → acceleration of gravity. → gravitational; → acceleration. |
gravitational attraction darkešeš-e gerâneši Fr.: attraction gravitationnelle The force that pulls material bodies toward one another because of → gravitation. → gravitational; → attraction. |
gravitational collapse rombeš-e gerâneši (#) Fr.: effondrement gravitationnel Collapse of a mass of material as a result of the mutual → gravitational attraction of all its constituents. → gravitational; → collapse. |
gravitational constant pâyâ-ye gerâneši (#) Fr.: constante gravitationnelle A fundamental constant that appears in → Newton's law of gravitation. It is the force of attraction between two bodies of unit mass separated by unit distance: G = 6.673 x 10^{-8} dyn cm^{2} g^{-2} or 6.673 x 10^{-8} cm^{3}s^{-2}g^{-1}, or 6.673 x 10^{-11} N m^{2} kg^{-2} or 6.673 x 10^{-11} m^{3}s^{-2}kg^{-1}. It was first measured in 1798 by Henry Cavendish (1731-1810), 71 years after Newton's death. Same as the → Newtonian constant of gravitation. → gravitational; → constant. |
gravitational contraction terengeš-e gerâneši Fr.: contraction gravitationnelle Decrease in the volume of an astronomical object under the action of a dominant, central gravitational force. → gravitational; → contraction. |
gravitational coupling constant pâyâ-ye jafsari-ye gerâneši Fr.: constante de couplage gravitationnel The dimensionless gravitational constant defined as the gravitational attraction between pair of electrons and normally given by: α_{G} = (Gm_{e}^{2}) / (ħc) = (m_{e} / m_{P})^{2} ~ 1.7518 × 10^{-45}, where ħ is → Planck's reduced constant, c the → speed of light, m_{e} is the → electron mass, and m_{P} is the → Planck mass. → gravitational; → coupling; → constant. |
gravitational encounter ruyâruyi-ye gerâneši Fr.: rencontre gravitationnelle An encounter in which two moving bodies alter each other's direction and velocity by mutual → gravitational attraction. → gravitational; → encounter. |
gravitational energy kâruž-e gerâneši Fr.: énergie gravitationnelle Same as → gravitational potential energy. → gravitational; → energy. |
gravitational equilibrium tarâzmandi-ye gerâneši (#) Fr.: équilibre gravitationnel The condition in a celestial body when gravitational forces acting on each point are balanced by some outward pressure, such as radiation pressure or electron degeneracy pressure, so that no vertical motion results. → gravitational; → equilibrium. |
gravitational field meydân-e gerâneši (#) Fr.: champ gravitationnel The region of space in which → gravitational attraction exists. → gravitational; → field. |
gravitational force niru-ye gerâneši (#) Fr.: force gravitationnelle The weakest of the four fundamental forces of nature. Described by → Newton's law of gravitation and subsequently by Einstein's → general relativity. → gravitational; → force. |
gravitational instability nâpâydâri-ye gerâneši (#) Fr.: instabilité gravitationnelle The process by which fluctuations in an infinite medium of size greater than a certain length scale (the Jeans length) grow by self-gravitation. → gravitational; → instability. |
gravitational interaction andaržireš-e gerâneši Fr.: interaction gravitationnelle Mutual attraction between any two bodies that have mass. → gravitational; → interaction. |
gravitational lens adasi-ye gerâneši (#) Fr.: lentille gravitationnelle A concentration of matter, such as a galaxy or a cluster of galaxies, that bends light rays from a background object, resulting in production of multiple images. If the two objects and the Earth are perfectly aligned, the light from the distant object appears as a ring from Earth. This is called an Einstein Ring, since its existence was predicted by Einstein in his theory of general relativity. → gravitational; → lens. |
gravitational lens equation hamugeš-e adasi-ye gerâneši Fr.: équation de lentille gravitationnelle The main equation of gravitational lens theory that sets a relation between the angular position of the point source and the observable position of its image. → gravitational; → lens; → equation. |
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