An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1307
sound speed
  تندی ِ صدا   
tondi-ye sedâ

Fr.: vitesse du son   

The velocity of propagation of a → longitudinal wave in a medium under specified conditions. Also known as sonic speed, sonic velocity, acoustic velocity, sound velocity, velocity of sound, speed of sound. The speed of sound is a thermodynamic property that relates to the change in pressure and density of the medium and can be expressed as C = (dP/dρ)1/2, where C is the sound velocity, dP is the change in pressure, and dρ the change in density. It can also be expressed as C = (E/ρ)1/2, where E is the bulk modulus elasticity. This equation is valid for liquids, solids and gases. The sound travels faster through media with higher → elasticity and/or lower density. If a medium is → incompressible the speed of sound is infinite. For → ideal gases, a simple relationship exists between the sound speed and temperature: C = (γR T)1/2, where γ is the → specific heat ratio (CP/CV), and R is the → gas constant. We see that for ideal gases it the speed is independent of pressure. In air at 0°C it is 332 m/sec. The speed of sound in a gas of hydrogen is 1315 m/s. → Mach number.

sound; → speed.

sound wave
  موج ِ صدا   
mowj-e sedâ (#)

Fr.: onde sonore   

A → longitudinal wave which when striking the ear gives rise to the sensation of sound. Such waves can be propagated in solids, liquids, and gases. The material particles transmitting sound waves oscillate in the direction of propagation of the wave itself. There is a large range of frequencies within which longitudinal waves can stimulate the human ear and brain to the sensation of hearing. This range is from about 20 → Hz to about 20,000 Hz and is called the audible range. → ultrasound; → infrasound.

sound; → wave.


Fr.: sondage, radiosondage   

1) In geophysics, any penetration of the natural environment for scientific observation.
2) In meteorology, a free, unmanned balloon carrying instruments aloft to make atmospheric measurements, esp. a radiosonde balloon.
3) The measurement of the depth of water beneath a vessel.

From Fr. sonder, → sonde.

From gomâné, → sonde, + zani verbal noun of zadan "to do; to strike, beat; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *gwhen- "to strike, kill").

sounding balloon
  بالون ِ گمانه‌زنی   
bâlon-e gamâne-zani

Fr.: ballon-sonde   

A small, free balloon sent into the upper atmosphere to measure, record, and transmit meteorological reports to a ground station.

sounding; → balloon.


Fr.: santé   

1) The quality of being → sound.
2) Logic: The quality or condition of a → deductive reasoning if it meets the two conditions of → valid arguments and → truepremises. These are the → necessary and sufficient conditions for soundness.

sound; → -ness.


Fr.: source   

General: Any thing or place from which something comes, arises, or is obtained.
Physics: A point, line, or area in space from which the lines of force in a vector field originate.
Electricity: Any active component, battery, or generator that supplies energy.
Thermodynamics: Any body, device, or system that provides energy.

M.E., from O.Fr. sourse "a rising, beginning, fountainhead of a river or stream," from p.p. of sourdre "to rise, spring up," from L. surgere "to rise," → surge.

Xan "source," variant xân (Gilaki xoni, Tabari xoni,Laki kyani, Tâleši xâni, xoni,); Mid.Pers. xân, xânig "source, spring," Av. xâ-, xan- "source, fountain, spring," xayana- "belonging to a spring;" cf. Khotanese khâhâ- "spring, fountain;" Skt. khâ'- "spring, source."

source function
  کریای ِ خن   
karyâ-ye xan

Fr.: fonction source   

For a radiating material, the ratio of emissivity to opacity.

source; → function.


Fr.: Sud   

The cardinal point which is opposite to north. It is also the direction of the Sun at local noon (in the northern hemisphere).

M.E. suth(e), south(e), from O.E. suth "southward, in the south;" cf. O.S., O.Fris. suth "southward, in the south," M.Du. suut), O.H.G. sund, perhaps related to base of *sunnon "sun," with sense of "the region of the sun."

Note: South is related to right since it is to the right when one faces the rising Sun. This occurs in, for example, in Av., Skt., and O.Ir., as below.

Daštar, from Mid.Pers. dašn "right hand;" Av. dašina- "right; south;" Ossetic dæsni "skillful, dexterous;" cf. Skt. dáksina- "right; southern;" Gk. dexios (<*deks-i-uo-) "right," dexiteros "located on the right side;" L. dexter "right;" Goth. taihswo "right hand;" O.Ir. dess "on the right hand, southern;" PIE base *deks- "right." The second element -tar direction suffix, as in Mid.Pers. ošastar "east" (Av. ušastara- "eastern"), dôšastar "west" (Av. daôšatara-, daôšastara- "western"), abâxtar "north" (Av. apāxtara- "northern"), Mod.Pers. bâxtar, → west.

South Atlantic Anomaly (SAA)
  ناسانی ِ اتلسی ِ دشتر   
nâsâni-ye Atlas-e daštar

Fr.: Anomalie Atlantique Sud   

A region of the Earth where the inner → Van Allen belt comes closest to the Earth's surface. It is due to the fact that the → geomagnetic field is offset from the center of the Earth. The region is centered near 25 degrees South 50 degrees West, close to the Atlantic coast of Brazil. The excess of trapped energetic particles in that region presents a problem for satellites in orbit around the Earth.

south; → Atlantic; → anomaly.

south celestial pole
  قطب ِ آسمانی ِ دشتر   
qotb-e âsmâni-ye daštar

Fr.: pôle sud céleste   

The point in the → southern hemisphere where the → rotation axis of the Earth touches the → celestial sphere. In contrast to the → north celestial pole, no bright star is visible in that direction.

north; → celestial; → pole.

south pole
  قطب ِ دشتر   
qotb-e daštar

Fr.: pôle Sud   

1) An → imaginary point in the → southern hemisphere representing the intersection of the → Earth's → rotation axis with the → globe with the → celestial sphere.
2) For a → magnet, the pole which points toward the geographic south.
3) In a → magnetic field, the point which receives a → line of force coming from the → north pole.

south; → pole.


Fr.: du Sud, méridional   

Of or pertaining to the south.

M.E., O.E. suðerne, from suð, → south, + -erne, suffix denoting direction.

Daštari, relating to daštar, → south.

Southern Cross
  چلیپای ِ دشتری   
calipâ-ye daštari

Fr.: Croix du Sud   

Popular name for the constellation → Crux. Its four brightest stars form a distinctive cross shape.

southern; → Crux.

southern hemisphere
  نیم‌سپهر دشتری   
nimsepehr-e daštari

Fr.: hémisphère sud   

The half of the → Earth or another → north pole between the → south pole and the → equator.

southern; → hemisphere.

  گذر ِ دشتر-سو   
gozar-e daštar-su


The transit of a celestial object, especially the Sun, across the meridian due south of the observer.

Verbal noun from → south (v.).

Gozar-e daštar-su, literally "passage southward," from gozar, → passage; daštarsouth; su, → direction.

fazâ (#)

Fr.: espace   

1) Physics: That part of the boundless four dimensional continuum in which matter can be physically extended.
2) Astro.: That part of the Universe which lies beyond the Earth's atmosphere and in which the density of matter is low. Also known as outer space.

M.E., from O.Fr. espace, from L. spatium "room, area, distance, stretch of time," of unknown origin.

Fazâ, loan from Ar.

space charge
  بار ِ فضایی   
bâr-e fazâyi (#)

Fr.: charge d'espace   

Electricity: An electric charge belonging to a cloud of electrons lying between a cathode and plate within an electric tube.
Geophysics: An excess of either negatively or positively charged ions in a layer of the atmosphere, giving that layer either a negative or positive charge.

space; → charge.

space debris
  تیفال ِ فضایی   
tifâl-e fazâyi

Fr.: débris spatial   

Man-made objects in orbit around the Earth that no longer serve any useful purpose. The estimated number of debris include about 22,000 tractable objects larger than 10 cm in all orbits, of which 2,200 are dead satellites and last stages of the rocket that put them in orbit. There are also left-overs from spacecraft and mission operations, such as bolts, lens caps, clamp bands, auxiliary motors, etc. The debris presents a threat because of their high speeds, which ranges between 15 and 20 km/sec. Also called space junk, space waste, orbital debris.

space; → debris.

space flight
  پرواز ِ فضایی   
parvâz-e fazâyi

Fr.: vol spatial   

A travel outside the Earth by manned or unmanned vehicle requiring space technology.

space; → flight.

space group
  گروه ِ فضایی   
goruh-e fazâyi

Fr.: groupe d'espace   

Set of operations (rotation about an axis, reflection across a plane, translation, or combination of these) which when carried out on a periodic arrangement of points in space brings the system of points to self-coincidence.

The word group comes from the mathematical notion of a group.

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