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

A rocket or balloon carrying instruments to probe conditions in the upper atmosphere.

From Fr. sonde "ounding line; plumb line."

Gomâné "a shaft sunk in order to ascertain the depth of the water when making a subterraneous canal," from Proto-Iranian *vi-mā-, from vi- "apart, away from, out" (cf. Av. vi-; O.Pers. viy- "apart, away;" Skt. vi- "apart, asunder, away, out;" L. vitare "to avoid, turn aside") + mā- "to measure" (cf. O.Pers./Av. mā(y)- "to measure;" Mod.Pers. mâ/mun/mân "measure," as in Pers. terms âzmâ- "to test;" pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl;" PIE base *me- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum).

Of, relating to, or being the speed of sound in a medium.

From L. sonus, → sound.

Sedâyi, pertaining to sedâ, → sound.

A noise caused by a shock wave that emanates from an object traveling at or above the speed of sound.

→ sonic; boom, M.E. bombon, bummyn "to buzz;" cf. Du. bommen, Ger. bummen, word made by sound imitation.

Qariv "shout, clamour, cry;" sedâyi, → sonic.

The point where the → stellar wind makes a transition from → subsonic to → supersonic flow. In the particular case of a spherically symmetric wind (thus with no magnetic field), the distance from star, at which the sonic point occurs, is given by: r_s = (GM_*)/2c_s², where G is the → gravitational constant, M_* is the stellar mass, and c_s the → sound speed at the sonic point.

→ sonic; → point.

To gather on a surface either by absorption, adsorption, or a combination of the two processes.

Verb, from sorption, extracted from → absorption→ adsorption, from L. sorbere "suck in," from PIE base *srebh- "to suck, absorb" (cf. Arm. arbi "I drank;" Gk. rhopheo "to gulp down;" Lith. srebiu "to drink greedily").

Šamidan, from šam, variant of šâm, as in âšâm, âšâmidan "to drink, to sip;" Av. šam- "to drink, sip, swallow;" Skt. cam, camati "to sip, dirink, lick up, absorb."

The process of sorbing. The state of being sorbed. → absorption; → adsorption.

Verbal noun of → sorb

The interval after which the heliacal rising of the star Sirius occurs at the same time of the year. It is a period of 1,460 Sothic years.

From Fr. sothique, from Gk. Sothis, an Egyptian name of Sirius; → period.

Tištari, of or pertaining to Tištar→ serius; dowré, → period.

The Egyptian year of 365 days and 6 hours, as distinguished from them Egyptian vague year, which contained 365 days.

From Fr. sothique, from Gk. Sothis, an Egyptian name of Sirius; → year.

Tištari, of or pertaining to Tištar→ serius; sâl, → year.

1) A physiological sensation received by the ear. It is caused by a vibrating source and transmitted as a longitudinal pressure wave motion through a material medium such as air.
2a) Free from damage, injury, decay, etc.
2b) Describing an → argument→ iff its → reasoning is → valid and all its → premises are → true.
2c) Logic: A formal system is sound if all the → inferences that are permitted by the rules of the system are valid inferences, that is, if no invalid arguments are provable within the system. → soundness.

1) M.E. soun; O.Fr. son, from L. sonus "sound," sonare "to sound;" PIE base *suen- "to sound;" cf. Av. x^van- "to sound;" Pers. x^vân-, x^vândan "to sing, read;" Skt. svana- "sound," svan- "to sound," svanati "it sounds;" O.E. swinn "music, song" (Cheung 2007).
2) M.E. sund, from O.E. gesund "sound, safe, having the organs and faculties complete and in perfect action," cf. O.S. gisund, O.Fris. sund, Du. gezond, O.H.G. gisunt, Ger. gesund "healthy," as in interjection gesundheit.

1) Sedâ "sound," most probably a Pers. term, since it exists also in Indo-Aryan languages: Skt. (late Vedic): sabda "articulate sound, noise," Pali and Prakriti: sadda "sound, noise," Sindhi: sadu, sado "shout, call," Gujrâti sad "call, voice, echo," Marathi: sad "shouting to," Konkani sad "sound," Sinhali: sada "sound." Therefore, sadâ in Ar. "reverberating noise, echo" maybe a loan from Pers., or a coincidence. Note that for the author of the classical Pers. dictionary Borhân-e Qâte' (India, 1652 A.D.), the Ar. term is a loanword from Pers.
2) Dorvâ (Dehxodâ) "whole, right, just;" Qâyeni, Gonâbâdi, Tabasi, Râvari dorvâx "healthy, whole," dorvâxi "health" (related to Pers. dorud "benediction, praise," dorost "whole, healthy, right"); cf. Sogd. žûk (from *druva-) "healthy;" O.Pers. duruwa- "healthy, firm, secure;" Av. druua- "healthy, firm, sound," druuatāt "health, soundness," drvô.cašman- "of sound eyes;" Skt. dhruvá- "fixed, firm;" → integral.

A sharp increase in aerodynamic drag that occurs as the speed of an aircraft approaches the speed of sound. Also called sonic barrier.

→ sound; → barrier.

The energy which → sound waves impart to a medium. Same as acoustic energy.

→ sound; → energy.

The distribution of → sound energy in a defined space.

→ sound; → field.

The maximum distance a → sound wave could have traveled through the ionized plasma from the → Big Bang until the → recombination era. It is 150 → Mpc, or bout 500 million → light-years. Sound horizon is the equivalent of the concept of → cosmic horizon, where one replaces → electromagnetic wave by → sound wave. The sound horizon is a fixed physical scale at the → last scattering surface. Cosmological models relate the value of sound horizon to the angle it subtends on the sky today. Same as acoustic horizon and sonic horizon. See also → CMB angular power spectrum.

→ sound; → horizon.

The average → sound power passing through a unit area perpendicular to the direction that the sound is traveling. It is usually expressed in watts per square meter.

→ sound; → level.

The expression of sound intensity in decibel units. The sound intensity level (L_I), in decibels, is computed as: L_I = 10 log (I/I₀), where I is the measured sound intensity and I₀ is the reference intensity (1 x 10 ^-12 watt per square meter).

→ sound; → intensity; → level.

The → sound energy emitted by a source per unit time, usually expressed in → watts. Sound power causes → sound pressure.

→ sound; → power.

The sound energy emitted by a sound source per unit time and expressed in → decibels. Sound power, in → watts, is converted to sound power level in decibels (L), by L = 10 log (W/W₀), where W₀ is the reference power (1 x 10 ^-12 watt).

→ sound; → power; → level.

The periodic fluctuation above and below atmospheric pressure created by an oscillating body which provides the → sound power. Instantaneous sound pressure is the peak value of air pressure.

→ sound; → pressure.

The number of → overtones present in a sound and their respective intensity. Like → loudness, it is a subjective quantity and cannot be measured with instruments.

→ sound; → quality.

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 (C_P/C_V), 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.