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

→ space-time.

→ space; → time.

A digging tool with a flat blade attached to a shaft so that it can be pushed into the ground with the foot.

M.E., from O.E. spadu; cognate with Gk. spathe "blade of a sword or oar."

Bil "spade," variants Kurd. bêr, Baluci bard, Gabri bard(a); Mid.Pers. bêl, bêr; Proto-Iranian *barda- metathesis of *badar-; cf. Av. vadar- "weapon" (Gershevitch 1962).

1) A chip or splinter.
2) To break up into small chips, flakes, or splinters, or to cause to break off in flakes.

M.E. spalle "a chip," verb spald "to split," from M.L.G. spalden, cognate with O.H.G. spaltan "to split."

Terišé "a chip," from tarâšidan "to cut, hew; scape; shave;" Mid.Pers. tâšitan "to cut, cleave; create by putting together different elements;" Av. taš- "to cut off, fashion, shape, create," taša- "axe" (Mod.Pers. taš, tišé "axe"), tašan- "creator;" cf. Skt. taks- "to form by cutting, tool, hammer, form," taksan- "wood-cutter, carpenter;" Gk. tekton "carpenter," tekhne "art, skill, craft, method, system;" L. textere "to weave;" PIE *teks- "to fashion."

A nuclear reaction in which a high energy particle that collides with a nucleus causes the target to eject several particles, thus changing both its mass number and its atomic number.

From → spall + -ation.

Verbal noun from terišidan, → spall.

1) Aeronautics: The distance between the wing tips of an airplane.
2) Math.: The smallest subspace of a → vector space that contains a given element or set of elements.

M.E. spanne, sponne, spayn; O.E. span(n), spon(n) "distance between the thumb and little finger of an extended hand;" cf. Ger. Spanne, Du. span.

Bâzé "extension of both arms when streched out," related to bâzu "arm" (Mid.Pers. bâzûk "arm;" Av. bāzu- "arm;" cf. Skt. bāhu- "arm, forearm;" Gk. pechys "forearm, arm, ell;" O.H.G. buog "shoulder;" Ger. Bug "shoulder;" Du. boeg; O.E. bôg, bôh "shoulder, bough;" E. bough " a branch of a tree;" PIE *bhaghu- "arm"); from Av. vībāzu- "fathom, measure of the outstretched arms."

Visible disruptive discharge of electricity between two places at opposite high potential. It is preceded by ionization of the path.

M.E., from O.E. spearca; cf. M.L.G. sparke, M.Du. spranke.

Laki âger "fire accompanied by flame," Lori azgel daaneh-ye aatash-e sorx shodeh va godaaxteh Kurd. agir "fire" Gilaki val "prominence, flame" Tâleši kel "blazing flame" standard Pers. gorr Laki gorron "flame;" jaraqé, probably word made by sound imitation.

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.

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

→ spark; → spectrum.

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

→ spatial; → coherence.

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

→ spatial; → resolution.

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.

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.

To utter words with the ordinary voice (not singing) to communicate; to talk.

From M.E. speken "to speak," from O.E. specan, alteration of earlier sprecan "to speak;" cf. Low Germ. spreken "to speak," Du. spreken, Ger. sprechen "to speak;" ultimately from PIE *spreg- "to make a sound, utter, speak."

From M.P. saxwanitan "to speak, to talk," → speech.

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."

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

→ special; → relativistic.

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.

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.

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."

→ Angular momentum per unit mass.

→ specific; → angular; → momentum.

The electric charge to mass ratio of an elementary particle.

→ specific; → charge.