# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 relativistic aberration   بیراهش ِ بازانیگی‌مند   birâheš-e bâzânigimandFr.: aberration relativiste   The aberration of light for an object moving with → relativistic speed. In contrast to the classical case, the → Lorentz transformation between the → rest frame of the observer and that of the object must be used. Relativistic aberration is expressed by the equation: cos φ' = (cos φ - )/(1 - cos φ.v/c), where φ is the classical → aberration angle, v the speed of the Earth, and c the → speed of light. It can also be expressed as: tan φ' = -(c/v)(1 - v2/c)1/2. relativistic Doppler effect   اُسکر ِ دوپلر ِ بازانیگی‌مند   oskar-e Doppler-e bâzânigimandFr.: effet Doppler relativiste   The Doppler effect when the relative motion of the source and the observer is comparable to the speed of light. In that case the classical Doppler formula should be corrected for effects of the special theory of relativity (Lorentz transformation). relativistic effect   اسکر ِ بازانیگی‌مند   oskar-e bâzânigimandFr.: effet relativiste   A physical phenomenon described only by the theories of → special relativity or → general relativity.→ relativistic; → effect. relativistic mass   جرم ِ بازانیگی‌مند   jerm-e bâzânigimandFr.: masse relativiste   In → special relativity, the mass that is assigned to a body in motion. Einstein demonstrated that the velocity of the observer has an effect on the way inertial mass is measured. The relativistic mass is expressed by mt = m0 / [1 - (v/c)2]1/2, where m0 is the → rest mass, v is the velocity, and c the → velocity of light. The experimental evidence for this phenomenon is observed in the mass of high-speed electrons accelerated by magnetic fields. This formula shows that it is impossible for a mass to be accelerated to the velocity of light in a vacuum.→ relativistic; → mass. relativistic particle   ذرّه‌ی ِ بازانیگی‌مند   zarre-ye bâzânigimandFr.: particule relativiste   A particle which has a speed comparable to the velocity of light.→ relativistic; → particle. relativistic precession   پیشایان ِ بازانیگی‌مند   pišâyân-e bâzânigimandFr.: précession relativiste   A → general relativistic phenomenon in which the line joining the → apsides of an orbit gradually rotates in a → prograde direction. Also called the → orbital precession and → perihelion precession. Although the general relativistic precession of Mercury's orbit is extremely small, the similar precession observed in the orbit of the → binary pulsar PSR B1913+16 amounts to 4.23 degrees per year, i.e. 36,000 times greater than the → advance of perihelion of Mercury. relativistic quantum mechanics   کو‌آنتوم مکانیک ِ بازانیگی‌مند   kuântom mekânik-e bâzânigimandFr.: mécanique quantique relativiste   A quantum theory that incorporates special relativity, for example, → quantum electrodynamics. relativistic redshift   سرخ‌کیب ِ بازانیگی‌مند   sorx kib-e bâzânigimandFr.: décalage vers le rouge relativiste   A redshift caused by the → relativistic Doppler effect. → gravitational redshift.→ relativistic; → redshift. relativistic speed   تندی ِ بازانیگی‌مند   tondi-ye bâzânigimandFr.: vitesse relativiste   Same as → relativistic velocity.→ relativistic; → speed. relativistic spin precession   پیشایان ِ آسه‌ی ِ چرخش ِ بازانیگی‌مند   pišâyân-e âse-ye carxeš-e bâzânigi-mandFr.: précession de l'axe de rotation relativiste   The change in the direction of the → rotation axis of a → pulsar in a → binary pulsar. In such a system, → geodetic precession leads to a relativistic → spin-orbit coupling, analogous of → spin-orbit coupling in atomic physics. In consequence, the pulsar spin precesses about the total → angular momentum, changing the relative → orientation of the pulsar toward Earth (Damour & Ruffini, 1974). As a result, the angle between the pulsar → rotation axis and our → line of sight changes with time, so that different portions of the emission beam can be observed leading to changes in the measured pulse profile. In extreme cases, the precession may even move the beam out of our line of sight and the pulsar may disappear as predicted for PSR 1913+16 for the year 2025.→ relativistic; → spin; → precession. relativistic velocity   تندای ِ بازانیگی‌مند   tondâ-ye bâzânigimandFr.: vitesse relativiste   The velocity of a body when it is a significant fraction of the → speed of light.→ relativistic; → velocity. relativity   بازانیگی   bâzânigiFr.: relativité   General: The state or fact of being relative. Physics: 1) Short for the → Galilean relativity. 2) Short for the → relativity theory of Einstein.Relativity, from → relative + → -ity. relativity of simultaneity   بازانیگی ِ همزمانی   bâzânigi-ye hamzamâniFr.: relatitivité de simultanéité   A basic concept of → special relativity whereby → events that are simultaneous in one → reference frame are not simultaneous in another reference frame moving with respect to the first.→ relativity; → simultaneity. relativity principle   پروز ِ بازانیگی   parvaz-e bâzânigiFr.: principe de relativité   The requirement employed by Einstein in his relativity theories, that the equations describing the laws of physics are the same in all frames of reference. This statement and that of the constancy of the speed of light constitute the founding principles of special relativity.Relativity; → principle. relativity theory   نگره‌ی ِ بازانیگی   negare-ye bâzânigiFr.: théorie de la relativité   The → theory of relativity.→ theory; → relativity. relativize   بازانی کردن   bâzâni kardanFr.: relativiser   To regard as or make one thing relative to something else.→ relative + → -ize. relax   واهلیدن   vâhelidan (#)Fr.: relaxer, se relaxer   To lessen the force, strength or intensity of something.m M.E., from O.Fr. relaxer from L. relaxare "relax, loosen, open," from → re- "back" + laxare "loosen," from laxus "loose."Vâhelidan, from vâ-, → re-, + helidan, heštan "to place, put" from Mid.Pers. hištan, hilidan "to let, set, leave, abandon;" Parthian Mid.Pers. hyrz; O.Pers. hard- "to send forth," ava.hard- "to abandon;" Av. harəz- "to discharge, send out; to filter," hərəzaiti "releases, shoots;" cf. Skt. srj- "to let go or fly, throw, cast, emit, put forth;" Pali sajati "to let loose, send forth." relaxation   واهلش   vâheleš (#)Fr.: relaxation   1) The evolution of the properties of a physical system which has been disturbed and which regains its equilibrium condition once the disturbing action has ceased. Relaxation is the response of the system to the perturbation. The time required by the system to regain its condition of minimum energy is called the → relaxation time. 2) Math.: In numerical analysis, a method of solving equations in which the errors, or residuals, resulting from an initial approximation are reduced by succeeding approximations until finally all are within the toleration limit.Verbal noun of → relax. relaxation time   زمان ِ واهلش   zamân-e vâhalešFr.: temps de relaxation   The characteristic length of time that is required for a system undergoing → relaxation to move to its equilibrium state. If the system follows an exponential law G = G0 exp(-t / τ), the relaxation time is the time required for G to obtain the fraction 1/e of its initial value G0.→ relaxation; → time. relaxed system   راژمان ِ واهلیده   râžmân-e vâhalidéFr.: système relaxé   A → dynamical system that has regained its → equilibrium. Especially a system in which the kinetic and potential energies obey a specific relationship known as the → virial theorem.P.p. from relax, → relaxation.