An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A branch of medicine that replaces or regenerates injured or diseased human cells, tissue, or organs, to restore or establish normal function.

→ regenerative; → medicine.

An acceleration that results from the vector addition of two or more distinct accelerations.

→ resultant; → acceleration.

A → number system in which letters represent numbers, still used occasionally today. The cardinal numbers are expressed by the following seven letters: I (1), V (5), X (10), L (50), C (100), D (500), and M (1,000). If a numeral with smaller value is written on right of greater value then smaller value is added to the greater one. If it is preceded by one of lower value, the smaller numeral is subtracted from the greater. Thus VI = 6 (V + I), but IV = 4 (V - I). Other examples are XC (90), CL (150), XXII (22), XCVII (97), CCCXCV (395). If symbol is repeated then its value is added. The symbols I, X, C and M can be repeated maximum 3 times. A dash line over a numeral multiplies the value by 1,000. For example V^- = 5000, X^- = 10,000, C^- = 100,000, and DLIX^- = 559,000.

→ numeral; → system.

The → Coulomb interaction reduced owing to the presence of other electrons. See → shielding effect.

→ screen; → coulomb; → interaction.

A star whose formation is induced by an older star itself formed previously in the same region. See also → stimulated star formation, → sequential star formation, → triggered star formation.

→ second; → generation; → star.

The head or chief administrative officer of a secretariat.

→ secretary; → general.

The apparent gradual increase in the → Moon's motion in its orbit, as measured relative to → mean solar time. Secular acceleration corresponds to an extremely gradual reduction in the speed of the → Earth's rotation. The slow-down of the Earth's spin comes mainly from → tidal frictions from the Moon. Historically, Edmond Halley (1656-1742) was the first to suggest that the Moon's mean rate of motion relative to the stars was gradually increasing. In 1693, Halley compared eclipses of recent, medieval, and classical Babylonian time, and discovered that the Moon's mean motion had been gradually increasing. Using Lunar Laser Ranging measurement, based on laser reflectors left by the Apollo astronauts on the Moon's surface (1969 to 1972), the secular acceleration is derived to be -25".4 ± 0".1 century ² (Xu Huaguan et al., 1996, in Earth, Moon and Planets 73, 101). This corresponds to a linear increase of about 3.5 cm yr^-1 in the mean Earth-Moon distance.

→ secular; → acceleration.

A classical method of finding all → prime numbers up to any given number n. The method consists of listing all positive integers from 2 up to the given number and then deleting some of them sequentially in steps. For example, if we wish to find the primes less than or equal to 50, we proceed as follows. All integers from 2 to 50 are first written. The integers that are divisible by 2, other than 2, are crossed out from the list. Since 3 is the first integer greater than 2 that is not removed, all the integers divisible by 3, other than 3, are crossed out. We do the same with 5 and then 7. Since all composite integers ≤ 50 are divisible by 2, 3, 5, or 7 (i.e. ≤ √50), all the remaining integers not deleted are prime numbers: 2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, and 47.

M.E. sive, O.E. sife "sieve;" cf. M.Du. seve, Du. zeef, O.H.G. sib, Ger. Sieb, of unknown origin. Related to sift.

Qarbâl (variants qarbil, qarbir, qelber, qalbur, gerbâl), probably related to the PIE base *krei- "to sieve, separate;" cf. Gk. krinein "to separate, decide, judge," krisis "decision;" L. cribrum "sieve" (Fr. crible), cernere "to sift, separate;" O.E. hriddel "sieve;" O.Ir. criathar; O.Welsh cruitr "sieve." Pers. qarbâl loaned in Ar. as gharbala "to sift," itself loaned in It. garbellare; M.Fr. garbeler "to sift;" E. garble "to sift impurities from."

The → range of → wavelengths or frequencies (→ frequency) at which a → detector is sensitive. Same as → bandwidth.

→ spectral; → coverage.

The situation in which spectroscopic features in a certain optical region are not sensitive enough to distinguish adjacent → luminosity classes, for instance → dwarf stars from → giant stars.

→ spectroscopic; → degeneracy.

The → excitation temperature of the → hyperfine structure levels of the → neutral hydrogen→ 21-centimeter line.

→ spin; → temperature.

1) The most commonly used definition is temperature of 273.15 K (0 °C) and pressure of 1 → atmosphere.
2) Chemistry: Temperature of 273.15 K (0 °C) and pressure of 10⁵  → pascal (Pa)s (1 → bar). International Union of Pure and Applied Chemistry (IUPAC) recommends that the former use of the pressure of 1 atm as standard pressure (equivalent to 1.01325 × 10⁵ Pa) should be discontinued.

→ standard; → temperature; → pressure.

The solid angle subtended at the center of a sphere by an area on its surface numerically equal to the square of the radius. → square degree.

From ste(reo)-, → stereo- + → radian.

The interaction between quarks that is transmitted by gluons. The characteristic range of the strong interaction is 10^-13 cm, and the time scale over which it operates is on the order of 10^-23 second. Also called → strong force.

→ strong; → interaction.

A condition in which there is an excess of the actual temperature gradient over the → adiabatic temperature gradient corresponding to the same pressure gradient. A region with superadiabatic temperature gradient is convectively unstable. → Hayashi forbidden zone.

→ super-; → adiabatic; → temperature; → gradient.

Exceeding the usual or prescribed number; extra; additional.

L.L. supernumarius "excess, counted in over" (of soldiers added to a full legion), from L. super numerum "beyond the number," → super- "beyond, over" + numerum, accusative of numerus, → number.

Faršomâr, from far- intensive prefix "much, abundant; elegantly;" also "above, upon, over; forward, along," → pro-, + šomâr, → number.

An additional faint arc or series of arcs just below the → primary rainbow. Supernumerary bows are caused by → interference and are more common toward the top of the bow.

→ supernumerary; → rainbow.

1) For a star, same as → effective temperature.
2) Meteo.: The air temperature at or near the earth's surface.

→ surface; → temperature.

A physical quantity characterizing the mean random motion of molecules in a physical body. In other words, a measure of the average kinetic energy of the particles of a system.

From L. temperatura "a tempering, moderation," from temperatus, p.p. of temperare "to moderate, to mix." Sense of "degree of heat or cold" first recorded 1670 (Boyle), from L. temperatura, used in this sense by Galileo.

Damâ, from dam "breath of an owen; bellows; smoke; air," also "moment, time," from Mid./Mod.Pers. damidan "to blow, breathe;" Av. dāδmainya- "blowing up;" cf. Skt. dahm- "to blow," dhámati "blows;" Gk. themeros "austere, dark-looking;" Lith. dumti "to blow;" PIE dhem-/dhemə- "to smoke, to blow."

Cosmology: Minute temperature variations of the cosmic microwave background radiation.

→ temperature; → anisotropy.