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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1298
spark gap
  گاف ِ جرقه   
gâf-e jaraqé (#)

Fr.: éclateur   

A device consisting of two electrodes separated by a small gap that is filled by a gas, usually air. A high → potential difference applied to the electrodes ionizes the gas and current flows across it for a brief time causing a spark across the gap. Spark gaps have a wide application. As spark plugs, they are used to ignite a mixture of fuel and air in the piston cylinders of an internal combustion engine. The electricity is provided by the battery and ignition coil, and the spark timing is controlled by the distributor. Spark gaps are also used as safety devices on equipment to prevent damage from voltage surges.

spark; → gap.

spark spectrum
  بیناب ِ اخگر، ~ جرقه   
binâb-e axgar, ~ jaraqé

Fr.: spectre d'étincelle   

The emission spectrum produced through a gas or vapor as a result of a high-voltage discharge between metallic electrodes.

spark; → spectrum.

spatial coherence
  همدوسی ِ فضایی   
hamdusi-ye fazâyi

Fr.: cohérence spatiale   

In a wave train, a correlation between the phases of waves at points separated in space at a given time.

spatial; → coherence.

spatial resolution
  واگشود ِ فضایی   
vâgošud-e fazâyi

Fr.: résolution spatiale   

The smallest detail that can be seen in an image. Same as → angular resolution.

spatial; → resolution.

Spörer minimum
  کمینه‌ی ِ اشپورر   
kamine-ye Spörer

Fr.: minimum de Spörer   

A period of low → solar activity that lasted from about A.D. 1420 to 1570. It occurred before → sunspots had been studied, and was discovered by analysis of the proportion of carbon-14 in tree rings, which is strongly correlated with solar activity.

Named for the German astronomer Gustav Spörer (1822-1895); → minimum.

Spörer's law
  قانون ِ اشپورر   
qânun-e Spörer

Fr.: loi de Spörer   

The empirical law that predicts the variation of → sunspot latitudes during a → solar cycle. At the start of a sunspot cycle, sunspots tend to appear around 30° to 45° latitude on the Sun's surface. As the cycle progresses, they appear at lower and lower latitudes, until 5° to 10°, at the end of the cycle. This tendency is revealed on a → butterfly diagram. Although named after Gustav Spörer, the "law" was first discovered by Richard Carrington.

Sporer minimum; → law.

special
  ویژه   
vižé (#)

Fr.: spécial, particulier   

Of a distinct or particular kind or character; having a particular function or purpose; not common, usual, or general.

M.E., from O.Fr. especial, from L. specialis "individual, particular," from → species "appearance, kind, sort."

Vižé, from Mid.Pers. apēcak "pure, sacred," from *apa-vēcak "set apart," from prefix apa- + vēcak, from vēxtan (Mod.Pers. bixtan) "to detach, separate, sift, remove," Av. vaēk- "to select, sort out, sift," pr. vaēca-, Skt. vic-, vinakti "to sift, winnow, separate; to inquire."

special relativistic
  بازانیگی‌مند ِ ویژه   
bâzânigimand-e vižé

Fr.: de relativité restreinte   

Of, relating to, or subject to the theory of → special relativity.

special; → relativistic.

special relativity
  بازانیگی ِ ویژه   
bâzanigi-ye vižé

Fr.: relativité restreinte   

The theory formulated by A. Einstein in 1905, which is based on the following two → postulates:
1) → Principle of relativity: The laws of physical phenomena are the same when studied in terms of two reference systems moving at a constant velocity relative to each other.
2) → Principle of constancy: The → velocity of light in free space is the same for all observers and is independent of the relative velocity of the source of light and the observer.
The term "special theory of relativity" refers to the restriction in the first postulate to reference systems moving at a constant velocity relative to each other (→ inertial reference frame). See also → general relativity.

special; → relativity.

species
  آرز   
âraz

Fr.: espèce   

1) A class of individuals having some common characteristics or qualities; distinct sort or kind.
2) Biology: The major subdivision of a genus or subgenus, regarded as the basic category of biological classification, composed of related individuals that resemble one another, are able to breed among themselves, but are not able to breed with members of another species.
3) Logic: One of the classes of things included with other classes in a genus. The set of things within one of these classes (Dictionary.com).

From L. species "a particular sort, kind, or type," originally "a sight, look, view, appearance," from specere "to look at, to see, behold;" PIE root spek- "to look around," → scope.

Âraz, from intensive/nuance â- + raz-, from Av. razan "order, → rule," from rāz- "to put in line, direct set," cf. Mod.Pers. raj "line, row," variants raž, rak, râk, rezg (Lori), radé, râdé "line, rule, row," rasté, râsté "row, a market with regular ranges of shops;" ris, risé "straight;" → right.

specific
  آبیزه   
âbizé

Fr.: précis, explicite, spécifique   

1) Clearly defined or identified; precise; particular.
2) Belonging or relating uniquely to a particular subject; not general.
3) Biology: Relating to species or a species.
4) Physics: Of or denoting a physical quantity expressed in terms of a unit mass, volume, or other measure, in order to give a value independent of the properties or scale of the particular system studied. → specific angular momentum; → specific charge; → specific density; → specific gravity; → specific heat; → specific humidity; → specific intensity; → specific volume.

From Fr. spécifique and directly from L.L. specificus "constituting a kind or sort," from L. species "kind, sort," → species.

Âbizé, from Mid.Pers. apēcak "pure, sacred" (older form of vižé, → special), from *apa-vēcak "set apart," from prefix apa- + vēcak, from vēxtan (Mod.Pers. bixtan) "to detach, separate, sift, remove," Av. vaēk- "to select, sort out, sift," pr. vaēca-, Skt. vic-, vinakti "to sift, winnow, separate; to inquire."

specific angular momentum
  جنباک ِ زاویه‌ای ِ آبیزه   
jonbâk-e zâvie-yi-ye âbizé

Fr.: moment angulaire spécifique   

Angular momentum per unit mass.

specific; → angular; → momentum.

specific charge
  بار ِ آبیزه   
bâr-e âbizé

Fr.: charge spécifique   

The electric charge to mass ratio of an elementary particle.

specific; → charge.

specific density
  چگالی ِ آبیزه   
cagâli-ye âbizé

Fr.: densité spécifique   

Same as → relative density.

specific; → density.

specific gravity
  گرانی ِ آبیزه   
gerâni-ye âbizé

Fr.: gravité spécifique   

The ratio of the density of a substance at the temperature under consideration to the density of water at the temperature of its maximum density (4 °C).

specific; → gravity.

specific heat
  گرمای ِ آبیزه   
garmâ-ye âbizé

Fr.: chaleur spécifique   

1) The quantity of heat required to raise the temperature of 1 gm of a substance through 1 °C. More generally, the → heat capacity of a unit mass of a substance. For a homogeneous body it is expressed as: C = dQ/M dT, where dQ is the quantity of heat transferred to a mass of M to raise the temperature by dT. It is often convenient to use the gram-mole as a unit of mass, → molar heat capacity.
2) For a gas there are two principal specific heats depending on the way in which the temperature is increased: i) that measured at constant pressure, CP, and ii) that measured at constant volume, CV. The specific heat CP is greater than CV, because a gas heated at constant pressure expands, and heat energy must be supplied equivalent to the work done in the expansion. The ratio γ = CP/CV is called the → adiabatic index. It varies from 1.66 for mono-atomic gases to a little over 1 for gases with complex molecules.

specific; → heat.

specific humidity
  نم ِ آبیزه   
nam-e âbizé

Fr.: humidité spécifique   

The dimensionless ratio of the mass of water vapor to the total mass in a particular volume. → humidity

specific; → humidity.

specific intensity
  درتنویی ِ آبیزه   
dartanuyi-e âbizé

Fr.: intensité spécifique   

A measure of the amount of radiation received per unit solid angle per unit time per unit area normally from an element of surface.

specific; → intensity.

specific volume
  گنج ِ آبیزه   
gonj-e âbizé

Fr.: volume spécifique   

The volume occupied by unit mass of a substance. Specific volume is the reciprocal of density.

specific; → volume.

specification
  آبیزش   
âbizeš

Fr.: précision, spécification   

1) The act of specifying.
2) A particular item, aspect, calculation, etc., in such a description.
3) Something specified, as in a bill of particulars; a specified particular, item, or article (Dictionary.com).

Verbal noun of → specify.

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