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

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

Homepage

Number of Results: 9 Search : third
 Bohr's third postulate   فراوس ِ سوم ِ بؤر   farâvas-e sevom-e BohrFr.: troisième postulat de Bohr   One of the postulates used in the → Bohr model, whereby the atom emits (absorbs) a quantum of electromagnetic energy (→ photon) when the electron passes from an orbit with a greater (lesser) n value to one with a lesser (greater) value. The energy of the quantum is equal to the difference between the energies of the electron on its orbits before and after the transition or "jump": hν = ε1 - ε2, where h is the → Planck's constant and ν the frequency of the transition.→ Bohr; → third; → postulate. Kepler's third law   قانون ِ سوم ِ کپلر   qânun-e sevom-e Kepler (#)Fr.: troisième loi de Kepler   The ratio between the square of a planet's → orbital period (P) to the cube of the mean distance from the Sun (a) is the same for all planets: P2∝ a3 (year 1618). More accurately, P2 = (4π2a3) / [G(M1 + M2)], where M1 and M2 are the masses of the two orbiting objects in → solar masses and G is the → gravitational constant. In our solar system M1 = 1. The → semi-major axis size (a is expressed in → astronomical units and the period (P) is measured in years.→ Kepler; → third; → law. Newton's third law of motion   سومین قانون ِ نیوتنی ِ جنبش   sevomin qânun-e Newtoni-ye jonbeš (#)Fr.: troisième loi newtonienne de mouvement   In a system where no external forces are present, every action force is always opposed by an equal and opposite reaction.→ Newton; → third; → law; → motion. principle of excluded third   پروز ِ سومی سکلانده   parvaz-e sevomi sokalândéFr.: principe du tiers exclu   Same as → principle of excluded middle.→ principle; → exclude; → third. third   سوم   sevom (#)Fr.: troisième   Next after the second; the ordinal number for three. → Newton's third law of motion; → third contact; → third dredge-up; → third law of thermodynamics.M.E. thirde, O.E. (north) thirda, variant of ridda, from P.Gmc. *thridjas (cf. O.Fris. thredda, O.S. thriddio, M.L.G. drudde, Du. derde, O.H.G. dritto, Ger. dritte, Goth. thridja).Sevom, ordinal number for sé, → three. third contact   پرماس ِ سوم   parmâs-e sevomFr.: troisième contact   The end of the total phase of a solar eclipse marked by the trailing edge of the Moon first revealing the Sun.→ third; → contact. third dredge-up   برونکشید ِ سوم   borunkešid-e sevomFr.: troisième dragage   A → dredge-up process that occurs in the stellar interior during He shell burning, as in → asymptotic giant branch (AGB) stars. These stars consist of a degenerate carbon-oxygen core, surrounded by a helium-rich region, above which lies a hydrogen-rich convective envelope. Following thermal pulses of the helium-burning shell, the convective envelope moves inward in mass, penetrating the hydrogen-exhausted regions. This is known as third dredge-up. As convection moves inward, nuclear processed materials are carried to the surface.→ third; → dredge-up. third law of thermodynamics   قانون ِ سوم ِ گرماتوانیک   qânun-e sevom-e garmâtavânikFr.: troisième loi de la thermodynamique   The → entropy of an idealized state of maximum order is zero at the temperature of → absolute zero. Another version of this law: As a system approaches absolute zero, all processes cease and the entropy of the system approaches a minimum value.→ third; → law; → thermodynamics. third quarter   چارک ِ سوم   cârak-e sevomFr.: troisième quartier   The phase of the Moon when half the visible disk of the waning Moon is illuminated. This quarter occurs when the celestial longitude of the Moon is 270° greater than the Sun's.→ third; → quarter.