An Etymological Dictionary of Astronomy and Astrophysics

The ability of something, especially a computer system, to adapt to increased demands.

See also: → scalable; → -ity.

The ability of something, especially a computer system, to adapt to increased demands.

See also: → scalable; → -ity.

The quality of a system that can be expanded or reduced in scale. Scalability allows computer equipment and software programs to be upgraded easily, rather than needing to be replaced.

See also: → scale; → -able.

The quality of a system that can be expanded or reduced in scale. Scalability allows computer equipment and software programs to be upgraded easily, rather than needing to be replaced.

See also: → scale; → -able.

Any quantity which is sufficiently defined only with its magnitude, when given in appropriate units. Compare → vector.
See also:
→ electric scalar potential, → scalar field, → scalar potential, → scalar processor, → scalar product, → scalar wave, → scalar-tensor theory, → tensor-vector-scalar (TeVeS) theory.

See also: Of or pertaining to → scale.

Any quantity which is sufficiently defined only with its magnitude, when given in appropriate units. Compare → vector.
See also:
→ electric scalar potential, → scalar field, → scalar potential, → scalar processor, → scalar product, → scalar wave, → scalar-tensor theory, → tensor-vector-scalar (TeVeS) theory.

See also: Of or pertaining to → scale.

A → tensor density of → order 0.

See also: → scalar; → density.

A → tensor density of → order 0.

See also: → scalar; → density.

A → field whose value at every point of space is independent of → direction and → position. Examples include → temperature distribution throughout space and → pressure distribution in a → fluid. Similarly, a → potential field, such as the Newtonian → gravitational field or the electric potential in → electrostatics are scalar fields. In quantum field theory, a scalar field is associated with → spin zero particles, such as → mesons or → bosons. Therefore, the → Higgs boson is associated with a scalar field. The → derivative of a scalar field results in a → vector field is called the → gradient. In contrast to a vector field, a scalar field is → invariant under the → rotation of the → coordinate system. The → inflation in the → early Universe is supposed to be driven by a scalar field, called the → inflaton field.

See also: → scalar; → field.

A → field whose value at every point of space is independent of → direction and → position. Examples include → temperature distribution throughout space and → pressure distribution in a → fluid. Similarly, a → potential field, such as the Newtonian → gravitational field or the electric potential in → electrostatics are scalar fields. In quantum field theory, a scalar field is associated with → spin zero particles, such as → mesons or → bosons. Therefore, the → Higgs boson is associated with a scalar field. The → derivative of a scalar field results in a → vector field is called the → gradient. In contrast to a vector field, a scalar field is → invariant under the → rotation of the → coordinate system. The → inflation in the → early Universe is supposed to be driven by a scalar field, called the → inflaton field.

See also: → scalar; → field.

The energy density fluctuations in the → photon-baryon plasma
that bring about hotter and colder regions. This perturbation creates velocity distributions that are out of phase with the acoustic density mode. The fluid velocity from hot to cold regions causes blueshift of the photons, resulting in → quadrupole anisotropy.

See also: → scalar; → perturbation.

The energy density fluctuations in the → photon-baryon plasma
that bring about hotter and colder regions. This perturbation creates velocity distributions that are out of phase with the acoustic density mode. The fluid velocity from hot to cold regions causes blueshift of the photons, resulting in → quadrupole anisotropy.

See also: → scalar; → perturbation.

Computers: A type of central processing unit in which only one operation on data is executed at a time. By contrast, in a vector processor, a single instruction operates simultaneously on multiple data items.

See also: → scalar; → processor.

Computers: A type of central processing unit in which only one operation on data is executed at a time. By contrast, in a vector processor, a single instruction operates simultaneously on multiple data items.

See also: → scalar; → processor.

A multiplication of two vectors giving a scalar. The scaler product of V₁ and V₂ is defined by:
V₁.V₂ = V₁.V₂ cos α, where V₁ and V₂ are the magnitudes of the vectors and α is the angle between them. Same as dot product. See also → vector product.

See also: → scalar; → product.

A multiplication of two vectors giving a scalar. The scaler product of V₁ and V₂ is defined by:
V₁.V₂ = V₁.V₂ cos α, where V₁ and V₂ are the magnitudes of the vectors and α is the angle between them. Same as dot product. See also → vector product.

See also: → scalar; → product.

In theories of gravitation, a kind of → gravitational wave, transversal and/or longitudinal, characterized by → spin zero.

See also: → scalar; → wave.

In theories of gravitation, a kind of → gravitational wave, transversal and/or longitudinal, characterized by → spin zero.

See also: → scalar; → wave.

An alternative to the standard → general relativity of gravity that contains not only the → tensor field (or → metric), but also a → scalar field. In this formalism, the → gravitational constant is considered to vary over time. As a consequence, the measured strength of the gravitational interaction is a function of time. Same as → Jordan-Brans-Dicke theory.

See also: → scalar; → tensor; → theory.

An alternative to the standard → general relativity of gravity that contains not only the → tensor field (or → metric), but also a → scalar field. In this formalism, the → gravitational constant is considered to vary over time. As a consequence, the measured strength of the gravitational interaction is a function of time. Same as → Jordan-Brans-Dicke theory.

See also: → scalar; → tensor; → theory.

1a) A succession or progression of steps or degrees.

1b) A standard of measurement or estimation; point of reference by which to gauge or rate.

2. To reduce or increase according to a common proportion (often followed by down or up).

Etymology (EN): M.E., from L. scalae “ladder, stairs.”

Etymology (PE): Marpel, literally “measuring stick, measuring step,” on the model of Ger. Maßstab
from Mass “measure” + Stab “stick, bar, pole, baton.” The first element from
Mod./Mid.Pers. mar “measure, count,” from Av.
mar- “to count, remember;” Skt.
smr, smarati “to remember, he remembers;” L. memor, memoria; Gk.
mermera “care,” martyr “witness.” The second element pel “stick, a bit of wood;” pel can also be interpreted as the contraction of pellé “staircase, ladder.”

1a) A succession or progression of steps or degrees.

1b) A standard of measurement or estimation; point of reference by which to gauge or rate.

2. To reduce or increase according to a common proportion (often followed by down or up).

Etymology (EN): M.E., from L. scalae “ladder, stairs.”

Etymology (PE): Marpel, literally “measuring stick, measuring step,” on the model of Ger. Maßstab
from Mass “measure” + Stab “stick, bar, pole, baton.” The first element from
Mod./Mid.Pers. mar “measure, count,” from Av.
mar- “to count, remember;” Skt.
smr, smarati “to remember, he remembers;” L. memor, memoria; Gk.
mermera “care,” martyr “witness.” The second element pel “stick, a bit of wood;” pel can also be interpreted as the contraction of pellé “staircase, ladder.”

In computer science, to reduce the processing power of the same node/system by reducing its resources (CPU, RAM, etc.). This type of → vertical scaling is opposite to → scale up. See also → scale in, → scale out.

See also: → scale; → down.

In computer science, to reduce the processing power of the same node/system by reducing its resources (CPU, RAM, etc.). This type of → vertical scaling is opposite to → scale up. See also → scale in, → scale out.

See also: → scale; → down.

Math.: A number which scales, or multiplies, some quantity. In the equation y = Cx, C is the scale factor for x. C is also the coefficient of x, and may be called the constant of proportionality of y to x.
Geometry: The ratio of any two corresponding lengths in two similar geometric figures. The ratio of areas of two similar figures is the square of the scale factor.

See also: → scale; → factor.

Math.: A number which scales, or multiplies, some quantity. In the equation y = Cx, C is the scale factor for x. C is also the coefficient of x, and may be called the constant of proportionality of y to x.
Geometry: The ratio of any two corresponding lengths in two similar geometric figures. The ratio of areas of two similar figures is the square of the scale factor.

See also: → scale; → factor.

The height within which some parameter, such as pressure or density, decreases by a factor of e. For example, an atmospheric scale height of 100 km means that the value at 100 km is 1/e the value at the surface.

See also: → scale; → height.

The height within which some parameter, such as pressure or density, decreases by a factor of e. For example, an atmospheric scale height of 100 km means that the value at 100 km is 1/e the value at the surface.

See also: → scale; → height.

In computer science, to reduce the number of nodes (servers), as opposed to → scale out. Scale-in is a type of → horizontal scaling. See also → scale up, → scale down.

See also: → scale; → in.

In computer science, to reduce the number of nodes (servers), as opposed to → scale out. Scale-in is a type of → horizontal scaling. See also → scale up, → scale down.

See also: → scale; → in.

In computer science, to upgrade a system by increasing the number of nodes.
For example, instead of going from a CPU of X and memory of Y to a CPU with 4X and 4Y memory, use 4 machines with CPU of X and memory of Y. This is a type of → horizontal scaling. See also → scale in, → scale up, → scale down.

See also: → scale; → out.

In computer science, to upgrade a system by increasing the number of nodes.
For example, instead of going from a CPU of X and memory of Y to a CPU with 4X and 4Y memory, use 4 machines with CPU of X and memory of Y. This is a type of → horizontal scaling. See also → scale in, → scale up, → scale down.

See also: → scale; → out.

In computer science, to increase the processing power of the same node/system by increasing its resources (CPU, RAM, etc.).
This is a type of → vertical scaling
opposite to → scale down. For example, instead of a machine with a CPU running at speed of X and having Y gigabytes of memory, use a machine with a CPU running at speed of 4X and a memory of 4Y gigabytes. See also → scale in, → scale out.

See also: → scale; → up.

In computer science, to increase the processing power of the same node/system by increasing its resources (CPU, RAM, etc.).
This is a type of → vertical scaling
opposite to → scale down. For example, instead of a machine with a CPU running at speed of X and having Y gigabytes of memory, use a machine with a CPU running at speed of 4X and a memory of 4Y gigabytes. See also → scale in, → scale out.

See also: → scale; → up.

A triangle no two sides of which are equal.

Etymology (EN): From L.L. scalenus, from Gk. skalenos “uneven, unequal, rough,” from skallein “chop, hoe,” related to
skolios “crooked,” from PIE base *(s)qel- “crooked, curved, bent;” → triangle.

Etymology (PE): Sebar, → triangle; nâjur-pahlu “dissimilar sides,” from nâjur “dissimilar, ill-matched” + pahlu “side, flank” (Mid.Pers. pahlug “side, rib,” Av. pərəsu- “rib,” Ossetic fars “side, flank,” cf. Skt. párśu- “rib,” Lith. piršys (pl.) “horse breast”).

A triangle no two sides of which are equal.

Etymology (EN): From L.L. scalenus, from Gk. skalenos “uneven, unequal, rough,” from skallein “chop, hoe,” related to
skolios “crooked,” from PIE base *(s)qel- “crooked, curved, bent;” → triangle.

Etymology (PE): Sebar, → triangle; nâjur-pahlu “dissimilar sides,” from nâjur “dissimilar, ill-matched” + pahlu “side, flank” (Mid.Pers. pahlug “side, rib,” Av. pərəsu- “rib,” Ossetic fars “side, flank,” cf. Skt. párśu- “rib,” Lith. piršys (pl.) “horse breast”).

An electronic circuit devised to give a single pulse after a prescribed number of input pulses have been received.

See also: Agent noun from → scale.

An electronic circuit devised to give a single pulse after a prescribed number of input pulses have been received.

See also: Agent noun from → scale.

1. Altering original variable values (according to a specific function or an algorithm) into a range that meet particular criteria.
   

2. The ability of a system, or process, to handle a growing load in regards to capacity. It has two types: → vertical scaling and → horizontal scaling.

See also: → scale; → -ing.

1. Altering original variable values (according to a specific function or an algorithm) into a range that meet particular criteria.
   

2. The ability of a system, or process, to handle a growing load in regards to capacity. It has two types: → vertical scaling and → horizontal scaling.

See also: → scale; → -ing.

The part of the head where the hair grows from.

Etymology (EN): M.E., perhaps from O.Norse skālpr “sheath,” related to O.Norse skalli “a bald head,” from PIE root *(s)ker- “to cut,” → bark.

Etymology (PE): Keler, from Zâhedân Baloci keler “scalp,” cognate with kâlun, → bark.

The part of the head where the hair grows from.

Etymology (EN): M.E., perhaps from O.Norse skālpr “sheath,” related to O.Norse skalli “a bald head,” from PIE root *(s)ker- “to cut,” → bark.

Etymology (PE): Keler, from Zâhedân Baloci keler “scalp,” cognate with kâlun, → bark.

1. (v.) To sweep a surface with a beam of light or electrons in order to reproduce or transmit a picture.
   In radar, to sweep an airspace or region with a succession of directed beams from a radar aerial system.
   
2. (n.) An act or instance of scanning. The image or display so obtained.

Etymology (EN): M.E. scannen, from L.L. scandere “to read or mark so as to show metrical structure,”
originally, in classical L., “to climb” (the connecting notion is of the rising and falling rhythm of poetry), from PIE *skand- “to spring, leap” (cf. Skt. skandati “he jumps;” Gk. skandalon “a snare, trap, stumbling block;” O.Ir. scendim “I jump”).

Etymology (PE): Rajrub, literally “sweeping along rows,” from raj “row, line”

• rub “to sweep.” The first component raj, variants raž, rak, râk, rezg (Lori), ris, risé, radé, rasté, râsté, related to râst “right, true; just, upright, straight,” → row, → right.

The second component rub stem of rubidan, ruftan “to sweep,” related to robudan “to rub, carry off;” Mid.Pers. rôb- “to rub, sweep, attract;”
Av. urūpaiieinti “to cause racking pain(?);” cf. Skt. rop- “to suffer from abdominal pain,” rurupas “to cause violent pain,” ropaná- “causing racking pain,” rópi- “racking pain;” L. rumpere “to break;” O.E. reofan “to break, tear.”

1. (v.) To sweep a surface with a beam of light or electrons in order to reproduce or transmit a picture.
   In radar, to sweep an airspace or region with a succession of directed beams from a radar aerial system.
   
2. (n.) An act or instance of scanning. The image or display so obtained.

Etymology (EN): M.E. scannen, from L.L. scandere “to read or mark so as to show metrical structure,”
originally, in classical L., “to climb” (the connecting notion is of the rising and falling rhythm of poetry), from PIE *skand- “to spring, leap” (cf. Skt. skandati “he jumps;” Gk. skandalon “a snare, trap, stumbling block;” O.Ir. scendim “I jump”).

Etymology (PE): Rajrub, literally “sweeping along rows,” from raj “row, line”

• rub “to sweep.” The first component raj, variants raž, rak, râk, rezg (Lori), ris, risé, radé, rasté, râsté, related to râst “right, true; just, upright, straight,” → row, → right.

The second component rub stem of rubidan, ruftan “to sweep,” related to robudan “to rub, carry off;” Mid.Pers. rôb- “to rub, sweep, attract;”
Av. urūpaiieinti “to cause racking pain(?);” cf. Skt. rop- “to suffer from abdominal pain,” rurupas “to cause violent pain,” ropaná- “causing racking pain,” rópi- “racking pain;” L. rumpere “to break;” O.E. reofan “to break, tear.”

Any device for exposing an image on film, a sensitized plate, etc., by tracing light along a series of many closely spaced parallel lines.

See also: Agent noun of → scan.

Any device for exposing an image on film, a sensitized plate, etc., by tracing light along a series of many closely spaced parallel lines.

See also: Agent noun of → scan.

The process of analyzing or synthetizing successively the light values of the elements making up a picture area, according to a pre-determined method.

See also: Verbal noun of → scan.

The process of analyzing or synthetizing successively the light values of the elements making up a picture area, according to a pre-determined method.

See also: Verbal noun of → scan.

A → sundial consisting of an inverted half sphere and a central vertical → gnomon used by ancient Greeks. See also → Eratosthenes experiment.

Etymology (EN): Gk. skaphe “boat, skiff; a bowl.”

A → sundial consisting of an inverted half sphere and a central vertical → gnomon used by ancient Greeks. See also → Eratosthenes experiment.

Etymology (EN): Gk. skaphe “boat, skiff; a bowl.”

A flat triangular bone a pair of which form the back part of the shoulder. Commonly known as → shoulder blade.

Etymology (EN): L. scapula “shoulder.”

Etymology (PE): Šâné, Mid.Pers. šânag “shoulder-blade.”
Ketf, loan from Ar. kataf “shoulder.”

A flat triangular bone a pair of which form the back part of the shoulder. Commonly known as → shoulder blade.

Etymology (EN): L. scapula “shoulder.”

Etymology (PE): Šâné, Mid.Pers. šânag “shoulder-blade.”
Ketf, loan from Ar. kataf “shoulder.”

Geology: A line of cliffs produced by faulting, erosion, or landslides. → cliff.

Etymology (EN): From It. scarpa.

Etymology (PE): Tondé “a steep slope of a mountain,” from tond “swift, rapid, brisk; fierce, severe” (Mid.Pers. tund “sharp, violent;” Sogdian tund “violent;” cf. Skt. tod- “to thrust, give a push,” tudáti “he thrusts;” L. tundere “to thrust, to hit” (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere “to thrust or bore through;”
PIE base *(s)teud- “to thrust, to beat”); cf. dialectal Anzali tin, Laki den, Tâleši teš “steep rock.”

Geology: A line of cliffs produced by faulting, erosion, or landslides. → cliff.

Etymology (EN): From It. scarpa.

Etymology (PE): Tondé “a steep slope of a mountain,” from tond “swift, rapid, brisk; fierce, severe” (Mid.Pers. tund “sharp, violent;” Sogdian tund “violent;” cf. Skt. tod- “to thrust, give a push,” tudáti “he thrusts;” L. tundere “to thrust, to hit” (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere “to thrust or bore through;”
PIE base *(s)teud- “to thrust, to beat”); cf. dialectal Anzali tin, Laki den, Tâleši teš “steep rock.”

1. To cause → electromagnetic waves or a → beam of → particles to be irregularly → deflected, → dispersed, or → reflected, or be turned aside in the process of → scattering.
   

2. The act of → scattering; something that is → scattered.

Etymology (EN): M.E. scateren, schateren “to disperse, break up, destroy;” cf. M.Du. schaderen “to scatter.”

Etymology (PE): Parâkandan “to scatter, to disperse;” Mid.Pers. parakandan “to scatter” (cf. apakandan “to throw”), from Proto-Iranian *pari-kan-, from *pari, *par- “around” (cf. Pers. pirâ-, variant par- “around, about,” from Mid.Pers. pêrâ; O.Pers. pariy “around, about,” Av. pairi “around, over,” per- “to pass over, beyond;”
cf. Skt. pari;
PIE base *per- “through, across, beyond;” cf. Gk. peri “around, about,
beyond;” L. per “through”) + *kan- “to throw, place, put” (cf. Pers. afgandan “to throw; to lay, place;” kandan “to dig; to extract;” Mid.Pers. kan-, kandan “to dig;”
O.Pers. kan- “to dig,” akaniya- “it was dug;” Av. kan- “to dig,” uskən- “to dig out;” cf. Skt. khan- “to dig,” khanati “he digs,” kha- “cavity, hollow, cave, aperture”).

1. To cause → electromagnetic waves or a → beam of → particles to be irregularly → deflected, → dispersed, or → reflected, or be turned aside in the process of → scattering.
   

2. The act of → scattering; something that is → scattered.

Etymology (EN): M.E. scateren, schateren “to disperse, break up, destroy;” cf. M.Du. schaderen “to scatter.”

Etymology (PE): Parâkandan “to scatter, to disperse;” Mid.Pers. parakandan “to scatter” (cf. apakandan “to throw”), from Proto-Iranian *pari-kan-, from *pari, *par- “around” (cf. Pers. pirâ-, variant par- “around, about,” from Mid.Pers. pêrâ; O.Pers. pariy “around, about,” Av. pairi “around, over,” per- “to pass over, beyond;”
cf. Skt. pari;
PIE base *per- “through, across, beyond;” cf. Gk. peri “around, about,
beyond;” L. per “through”) + *kan- “to throw, place, put” (cf. Pers. afgandan “to throw; to lay, place;” kandan “to dig; to extract;” Mid.Pers. kan-, kandan “to dig;”
O.Pers. kan- “to dig,” akaniya- “it was dug;” Av. kan- “to dig,” uskən- “to dig out;” cf. Skt. khan- “to dig,” khanati “he digs,” kha- “cavity, hollow, cave, aperture”).

1. Occurring or distributed over widely spaced and irregular intervals in time or space.
   

2. The quality of a particle that has undergone → scattering.

See also: Past participle of → scatter.

1. Occurring or distributed over widely spaced and irregular intervals in time or space.
   

2. The quality of a particle that has undergone → scattering.

See also: Past participle of → scatter.

A → particle that causes → scattering of another particle through interaction with it.

See also: → scatter; → -er.

A → particle that causes → scattering of another particle through interaction with it.

See also: → scatter; → -er.

The process in which the direction of motion of → particles or → waves is changed randomly because of their → interactions (→ collisions) with other particles of the → medium transversed.

Two parameters govern scattering: 1) the wavelength (λ) of the incident radiation, and 2) the size of the scattering particle (r), usually expressed as the nondimensional size parameter, x = 2πr / λ. The size parameter defines three types of scattering:

1. x much less than 1 (or r much smaller than λ), → Rayleigh scattering;
   

2. x ~ 1 (or rλ), → Mie scattering; and
   

3. x much larger than 1 (or r much larger than λ), → geometric scattering.
   

See also: → atmospheric scattering, → backscattering, → Brillouin scattering, → coherent scattering, → Compton scattering, → elastic scattering, → forward scattering, → last scattering, → last scattering surface, → multiple scattering, → noncoherent scattering, → quasi-single-scattering approximation, → Raman scattering, → scattering angle, → scattering coefficient, → scattering of stars, → selective scattering, → single scattering, → spin-flip scattering, → surface of last scattering, → Thomson scattering.

Related terms: → diffraction; → diffusion; → dispersion; → distribution.

See also: Verbal noun of → scatter.

The process in which the direction of motion of → particles or → waves is changed randomly because of their → interactions (→ collisions) with other particles of the → medium transversed.

Two parameters govern scattering: 1) the wavelength (λ) of the incident radiation, and 2) the size of the scattering particle (r), usually expressed as the nondimensional size parameter, x = 2πr / λ. The size parameter defines three types of scattering:

1. x much less than 1 (or r much smaller than λ), → Rayleigh scattering;
   

2. x ~ 1 (or rλ), → Mie scattering; and
   

3. x much larger than 1 (or r much larger than λ), → geometric scattering.
   

See also: → atmospheric scattering, → backscattering, → Brillouin scattering, → coherent scattering, → Compton scattering, → elastic scattering, → forward scattering, → last scattering, → last scattering surface, → multiple scattering, → noncoherent scattering, → quasi-single-scattering approximation, → Raman scattering, → scattering angle, → scattering coefficient, → scattering of stars, → selective scattering, → single scattering, → spin-flip scattering, → surface of last scattering, → Thomson scattering.

Related terms: → diffraction; → diffusion; → dispersion; → distribution.

See also: Verbal noun of → scatter.

The angle between the → incident radiation on a → particle (such as a water droplet in a rainbow) and the scattered radiation (such as the light ray leaving the droplet). Scattering angle is a function of → impact parameter. In other words, The angle along which the change of direction has taken place, irrespective whether radiation is scattered by particles or reflected (refracted) by a surface.

See also: → scattering; → angle.

The angle between the → incident radiation on a → particle (such as a water droplet in a rainbow) and the scattered radiation (such as the light ray leaving the droplet). Scattering angle is a function of → impact parameter. In other words, The angle along which the change of direction has taken place, irrespective whether radiation is scattered by particles or reflected (refracted) by a surface.

See also: → scattering; → angle.

The fraction of light scattered per unit distance in a medium.

See also: → scattering; → coefficient.

The fraction of light scattered per unit distance in a medium.

See also: → scattering; → coefficient.

The progressive increase of random motions of → disk stars with increasing stellar → ages. While some initial random
motion seems likely in the disturbed conditions of disks
when the oldest stars formed, the observation is generally attributed to scattering processes. Both massive gas → clumps and → spiral waves are considered as scattering agents (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).

See also: → scattering; → star.

The progressive increase of random motions of → disk stars with increasing stellar → ages. While some initial random
motion seems likely in the disturbed conditions of disks
when the oldest stars formed, the observation is generally attributed to scattering processes. Both massive gas → clumps and → spiral waves are considered as scattering agents (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).

See also: → scattering; → star.

The second-brightest star in the constellation → Pegasus. It is a giant star of spectral type M2.5 II-III whose magnitude varies between 2.3 and 2.7.

Etymology (EN): Scheat, from Ar. as-sâq “leg,” erroneously taken from the Ar. name of δ Aquarii as-sâq al-sâkib al-ma’ (الساق الساکب‌الماء) “the leg of the water-bearer.”

Etymology (PE): Asb-šâné, literally “the Horse’s Shoulder,” from asb→ horse + šâné “shoulder” (Lori šona, Kurd. šân, Gilaki cân, con), maybe related to Skt. skandhá- “shoulder, trunk of tree, bulk” (Pali khandha-, Ashkun kándä, Bashkarih kân, Tôrwâldi kan “shoulder”), from skand- “to jump, leap, spring out,” skandati “he jumps;” cf. L. scandere “to climb.”

The second-brightest star in the constellation → Pegasus. It is a giant star of spectral type M2.5 II-III whose magnitude varies between 2.3 and 2.7.

Etymology (EN): Scheat, from Ar. as-sâq “leg,” erroneously taken from the Ar. name of δ Aquarii as-sâq al-sâkib al-ma’ (الساق الساکب‌الماء) “the leg of the water-bearer.”

Etymology (PE): Asb-šâné, literally “the Horse’s Shoulder,” from asb→ horse + šâné “shoulder” (Lori šona, Kurd. šân, Gilaki cân, con), maybe related to Skt. skandhá- “shoulder, trunk of tree, bulk” (Pali khandha-, Ashkun kándä, Bashkarih kân, Tôrwâldi kan “shoulder”), from skand- “to jump, leap, spring out,” skandati “he jumps;” cf. L. scandere “to climb.”

A mathematical expression that describes the → luminosity function of galaxies. The function correctly reflects the facts that the luminosity function decreases with increasing luminosity and that the decrease is particularly marked at high luminosities. It is expressed as:

φ(L) = φ(L/L)^α exp (-L/L), which has two parts and three parameters: φ is an empirically determined amplitude, α is an empirically derived exponent, and L is a characteristic luminosity which separates the low and high luminosity parts.
For small luminosities (L much smaller than L) the Schechter function approaches a power law, while at high luminosities (L much larger than L) the frequency of galaxies drops exponentially. φ, L^*, and the faint-end slope α depend on the observed wavelength range, on the → redshift, and on the environment where the galaxies are observed.

See also: Named after the American astronomer Paul Schechter (1948-), who proposed the function in 1976 (ApJ 203, 297); → function.

A mathematical expression that describes the → luminosity function of galaxies. The function correctly reflects the facts that the luminosity function decreases with increasing luminosity and that the decrease is particularly marked at high luminosities. It is expressed as:

φ(L) = φ(L/L)^α exp (-L/L), which has two parts and three parameters: φ is an empirically determined amplitude, α is an empirically derived exponent, and L is a characteristic luminosity which separates the low and high luminosity parts.
For small luminosities (L much smaller than L) the Schechter function approaches a power law, while at high luminosities (L much larger than L) the frequency of galaxies drops exponentially. φ, L^*, and the faint-end slope α depend on the observed wavelength range, on the → redshift, and on the environment where the galaxies are observed.

See also: Named after the American astronomer Paul Schechter (1948-), who proposed the function in 1976 (ApJ 203, 297); → function.

A power-law relation between → star formation rate (SFR) and a corresponding measure of gas density. For external galaxies it is usually expressed in terms of the observable surface density of gas (Σ_gas):

SFR ∝ Σ_gasⁿ. The exponent n is determined to be 1.4 ± 0.15 (Kennicutt 1998, ApJ 498, 541). The validity of the Schmidt law has been tested in dozens of empirical studies.

The Schmidt law provides a tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density.

See also: Named after Maarten Schmidt (1929-), a dutch-born American astronomer, who also discovered the first → quasar (3C 273) in 1963.

A power-law relation between → star formation rate (SFR) and a corresponding measure of gas density. For external galaxies it is usually expressed in terms of the observable surface density of gas (Σ_gas):

SFR ∝ Σ_gasⁿ. The exponent n is determined to be 1.4 ± 0.15 (Kennicutt 1998, ApJ 498, 541). The validity of the Schmidt law has been tested in dozens of empirical studies.

The Schmidt law provides a tight parametrization of the global star formation law, extending over several orders of magnitude in SFR and gas density.

See also: Named after Maarten Schmidt (1929-), a dutch-born American astronomer, who also discovered the first → quasar (3C 273) in 1963.

A telescope with a spherical concave primary mirror in which the aberration produced by the spherical mirror is compensated for by a thin correcting lens placed at the opening of the telescope tube. Its very wide-field performance makes it suitable for surveys.

See also: Named after Bernhard Woldemar Schmidt (1879-1935), a German optician of
Estonian origin, who invented the telescope in 1930; → telescope.

A telescope with a spherical concave primary mirror in which the aberration produced by the spherical mirror is compensated for by a thin correcting lens placed at the opening of the telescope tube. Its very wide-field performance makes it suitable for surveys.

See also: Named after Bernhard Woldemar Schmidt (1879-1935), a German optician of
Estonian origin, who invented the telescope in 1930; → telescope.

A mixture of the → Cassegrain telescope with a very short → focal length and of a Schmidt design (due to the presence of the → corrective plate), used mainly in → amateur astronomy. The main advantage of this telescope is its compact design. However, Schmidt-Cassegrain telescopes produce fainter images with less contrast than other telescope designs with similar → aperture sizes. This is due to the comparatively large → secondary mirror required to reflect the light back the → eyepiece.

See also: → Schmidt telescope; → Cassegrain telescope.

A mixture of the → Cassegrain telescope with a very short → focal length and of a Schmidt design (due to the presence of the → corrective plate), used mainly in → amateur astronomy. The main advantage of this telescope is its compact design. However, Schmidt-Cassegrain telescopes produce fainter images with less contrast than other telescope designs with similar → aperture sizes. This is due to the comparatively large → secondary mirror required to reflect the light back the → eyepiece.

See also: → Schmidt telescope; → Cassegrain telescope.

Same as the → Schmidt law.

See also: Named after the American astrophysicists Maarten Schmidt (1929-), the pioneer of research in this field, and Robert C. Kennicutt, Jr. (1951-), who developed the study; → relation.

Same as the → Schmidt law.

See also: Named after the American astrophysicists Maarten Schmidt (1929-), the pioneer of research in this field, and Robert C. Kennicutt, Jr. (1951-), who developed the study; → relation.

1. A learned or erudite person, especially one who has profound knowledge of a particular subject. → scientist.
   
2. A student who has been awarded a scholarship.

Etymology (EN): M.E. scoler(e); O.E. scolere “student,” from M.L. scholaris, from L.L. scholaris “of a school,” from L. schola, from Gk. skhole “school, lecture, discussion; leisure, spare time.”

Etymology (PE): Dâne&#353pažuh, from dâneš→ science + pažuh agent noun of pažuhidan “to search,” → research. Dânešvar, from dâneš, as befor, + -var possession suffix.

1. A learned or erudite person, especially one who has profound knowledge of a particular subject. → scientist.
   
2. A student who has been awarded a scholarship.

Etymology (EN): M.E. scoler(e); O.E. scolere “student,” from M.L. scholaris, from L.L. scholaris “of a school,” from L. schola, from Gk. skhole “school, lecture, discussion; leisure, spare time.”

Etymology (PE): Dâne&#353pažuh, from dâneš→ science + pažuh agent noun of pažuhidan “to search,” → research. Dânešvar, from dâneš, as befor, + -var possession suffix.

During the → main sequence stage, a star burns the hydrogen in its core and transforms it into helium. When the helium mass amounts to about 10% of the initial stellar mass, the star can no longer maintain the → hydrostatic equilibrium in its core; the star increases its volume and leaves the main sequence in order to become a → red giant.

See also: Named after the Brazilian astrophysicist Mario Schönberg (1914-1990) and Subramahmanyan Chandrasekhar, → Chandrasekhar limit, who were the first to point out this limit and derive it (1942, ApJ 96, 161).

During the → main sequence stage, a star burns the hydrogen in its core and transforms it into helium. When the helium mass amounts to about 10% of the initial stellar mass, the star can no longer maintain the → hydrostatic equilibrium in its core; the star increases its volume and leaves the main sequence in order to become a → red giant.

See also: Named after the Brazilian astrophysicist Mario Schönberg (1914-1990) and Subramahmanyan Chandrasekhar, → Chandrasekhar limit, who were the first to point out this limit and derive it (1942, ApJ 96, 161).

1. An institution where instruction is given, especially to persons under college age.
   

   2. An institution for instruction in a particular skill or field.
      

   3. A college or university (Dictionary.com).

Etymology (EN): M.E. scole, O.E. scôl, from L. schola, from Gk. scholé “spare time, leisure,” from skhein “to get.”

Etymology (PE): Dabestân, from Mid.Pers. dibistân “school,” literally “place of writing” or “the place where documents are kept,” from dib, dip “→ document,” + -istân suffix of place, → summer.

1. An institution where instruction is given, especially to persons under college age.
   

   2. An institution for instruction in a particular skill or field.
      

   3. A college or university (Dictionary.com).

Etymology (EN): M.E. scole, O.E. scôl, from L. schola, from Gk. scholé “spare time, leisure,” from skhein “to get.”

Etymology (PE): Dabestân, from Mid.Pers. dibistân “school,” literally “place of writing” or “the place where documents are kept,” from dib, dip “→ document,” + -istân suffix of place, → summer.

A junction between a metal and a semiconductor, which exhibits rectifying characteristics. A Schottky barrier has a very fast switching action and low forward voltage drop of about 0.3 volts, compared with 0.6 volts in silicon diodes, which use adjacent p-type and n-type semiconductors.

See also: Named after Walter Hans Schottky (1886-1976), German physicist, who described the phenomenon; → barrier.

A junction between a metal and a semiconductor, which exhibits rectifying characteristics. A Schottky barrier has a very fast switching action and low forward voltage drop of about 0.3 volts, compared with 0.6 volts in silicon diodes, which use adjacent p-type and n-type semiconductors.

See also: Named after Walter Hans Schottky (1886-1976), German physicist, who described the phenomenon; → barrier.

An unoccupied position in a crystal lattice which forms when oppositely charged ions leave their lattice sites, creating vacancies.

See also: Named after Walter Hans Schottky (1886-1976), German physicist; → defect.

An unoccupied position in a crystal lattice which forms when oppositely charged ions leave their lattice sites, creating vacancies.

See also: Named after Walter Hans Schottky (1886-1976), German physicist; → defect.

A → semiconductor diode containing a → Schottky barrier. Such a diode has a low forward voltage drop and very fast switching characteristics. Also called Schottky barrier diode and hot electron diode.

See also: → Schottky barrier; → diode.

A → semiconductor diode containing a → Schottky barrier. Such a diode has a low forward voltage drop and very fast switching characteristics. Also called Schottky barrier diode and hot electron diode.

See also: → Schottky barrier; → diode.

Excess voltage generated by random fluctuations in the emission of electrons from a hot cathode, causing a hissing or sputtering sound (shot noise) in an audio amplifier and causing snow on a television screen. Same as → shot effect, → shot noise.

See also: Named after Walter Hans Schottky (1886-1976), German physicist;
→ noise.

Excess voltage generated by random fluctuations in the emission of electrons from a hot cathode, causing a hissing or sputtering sound (shot noise) in an audio amplifier and causing snow on a television screen. Same as → shot effect, → shot noise.

See also: Named after Walter Hans Schottky (1886-1976), German physicist;
→ noise.

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

See also: Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

See also: Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

See also: Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

A fundamental equation of physics in → quantum mechanics the solution of which gives the → wave function, that is a mathematical expression that contains all the information known about a particle. This → partial differential equation describes also how the wave function of a physical system evolves over time.

See also: Named after Erwin Schrödinger (1887-1961), the Austrian theoretical physicist, Nobel Prize 1933, who first developed the version of quantum mechanics known as → wave mechanics; → equation.

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics.
A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an
→ alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat’s fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, “observes” the cat, and “collapses” its wave function. However, Schrödinger’s argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function
becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore “observed” by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Etymology (EN): Named after Erwin Schrödinger (1887-1961), → Schrodinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta “cat.”

Etymology (PE): Gorbé, from Mid.Pers. gurbag “cat;” → Schrodinger equation,

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics.
A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an
→ alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat’s fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, “observes” the cat, and “collapses” its wave function. However, Schrödinger’s argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function
becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore “observed” by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Etymology (EN): Named after Erwin Schrödinger (1887-1961), → Schrodinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta “cat.”

Etymology (PE): Gorbé, from Mid.Pers. gurbag “cat;” → Schrodinger equation,

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics.
A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an
→ alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat’s fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, “observes” the cat, and “collapses” its wave function. However, Schrödinger’s argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function
becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore “observed” by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Etymology (EN): Named after Erwin Schrödinger (1887-1961), → Schrödinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta “cat.”

Etymology (PE): Gorbé, from Mid.Pers. gurbag “cat;” → Schrodinger equation,

A → thought experiment intended to illustrate the → superposition principle in → quantum mechanics.
A cat is put in a steel box which is separated from the outside world. The box also contains a vial of lethal acid, a tiny amount of a radioactive substance, a → Geiger counter, and a hammer. If an atom decays and the Geiger counter detects an
→ alpha particle, the hammer breaks the vial which kills the cat. According to Schrödinger, as long as the box stays closed the cat’s fate is tied to the → wave function of the atom, which is itself in a superposition of decayed and un-decayed states. Thus the cat must itself be in a superposition of dead and alive states before the observer opens the box, “observes” the cat, and “collapses” its wave function. However, Schrödinger’s argument fails because it rests on the assumption that macroscopic objects can remain unobserved in a superposition state. When an atom decays, its wave function
becomes entangled with the enormously complex wave function of the macroscopic Geiger counter. The atom is therefore “observed” by the Geiger counter. Since a Geiger counter cannot, for all practical purposes, be isolated from the rest of the world, the rest of the world observes the atom, and the cat is either dead or alive. → collapse of the wave function.

Etymology (EN): Named after Erwin Schrödinger (1887-1961), → Schrödinger equation, who proposed the thought experiment in 1935 in order to illustrate the inconsistency of the Copenhagen interpretation of quantum mechanics; cat, from M.E. cat, catte; O.E. catt, catte (cf. O.Fris, M.D. katte, O.H.G. kazza, Ir. cat, Welsh cath), probably from L.L. cattus, catta “cat.”

Etymology (PE): Gorbé, from Mid.Pers. gurbag “cat;” → Schrodinger equation,

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

See also: Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

See also: Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

See also: Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

A phenomenon in which the observed and predicted phases of Venus do not coincide. At eastern elongation, when the planet is visible in the evening sky, dichotomy (half-phase) usually comes a day or two earlier than predicted, while at western elongation dichotomy occurs a day or two later.

See also: Named after Johan Schröter (1745-1816), German astronomer, who first described the effect in 1793; → effect.

An upper theoretical limit to the → eccentricity of orbits near a → supermassive black hole (SBH). It results from the impact of → relativistic precession on the stellar orbits. This phenomenon acts in such a way as to “repel” inspiralling bodies from the eccentric orbits that would otherwise lead to capture as → extreme mass ratio inspiral (EMRI)s. In other words, the presence of the Schwarzschild barrier reduces the frequency of EMRI events, in contrast to
that predicted from → resonant relaxation. Resonant relaxation relies on the orbits having commensurate radial and azimuthal frequencies, so they remain in fixed planes over multiple orbits. In the strong-field potential of a massive object, orbits are no longer Keplerian but undergo significant perihelion precession. Resonant relaxation is only efficient in the regime where precession is negligible. The Schwarzschild barrier refers to the boundary between orbits with and without significant precession. Inside this point resonant relaxation is strongly quenched, potentially reducing inspiral rates.

See also: → Schwarzschild black hole; → barrier.

An upper theoretical limit to the → eccentricity of orbits near a → supermassive black hole (SBH). It results from the impact of → relativistic precession on the stellar orbits. This phenomenon acts in such a way as to “repel” inspiralling bodies from the eccentric orbits that would otherwise lead to capture as → extreme mass ratio inspiral (EMRI)s. In other words, the presence of the Schwarzschild barrier reduces the frequency of EMRI events, in contrast to
that predicted from → resonant relaxation. Resonant relaxation relies on the orbits having commensurate radial and azimuthal frequencies, so they remain in fixed planes over multiple orbits. In the strong-field potential of a massive object, orbits are no longer Keplerian but undergo significant perihelion precession. Resonant relaxation is only efficient in the regime where precession is negligible. The Schwarzschild barrier refers to the boundary between orbits with and without significant precession. Inside this point resonant relaxation is strongly quenched, potentially reducing inspiral rates.

See also: → Schwarzschild black hole; → barrier.

A → black hole with zero → angular momentum (non-rotating) and zero electric charge derived from Karl Schwarzschild 1916 exact solution to Einstein’s vacuum → field equations.

See also: Karl Schwarzschild (1873-1916), German mathematical physicist, who carried out the first relativistic study of black holes. → black hole.

A → black hole with zero → angular momentum (non-rotating) and zero electric charge derived from Karl Schwarzschild 1916 exact solution to Einstein’s vacuum → field equations.

See also: Karl Schwarzschild (1873-1916), German mathematical physicist, who carried out the first relativistic study of black holes. → black hole.

In → general relativity, the → metric that describes the → space-time outside a static mass with spherically symmetric distribution.

See also: → Schwarzschild black hole; → metric.

In → general relativity, the → metric that describes the → space-time outside a static mass with spherically symmetric distribution.

See also: → Schwarzschild black hole; → metric.

The critical radius at which a massive body becomes a → black hole, i.e., at which light is unable to escape to infinity:
R_s = 2GM / c², where G is the → gravitational constant, M is the mass, and c the → speed of light. The fomula can be approximated to R_s≅ 3 x (M/Msun), in km. Therefore, the Schwarzschild radius for Sun is about 3 km and for Earth about 1 cm.

See also: → Schwarzschild black hole; → radius.

The critical radius at which a massive body becomes a → black hole, i.e., at which light is unable to escape to infinity:
R_s = 2GM / c², where G is the → gravitational constant, M is the mass, and c the → speed of light. The fomula can be approximated to R_s≅ 3 x (M/Msun), in km. Therefore, the Schwarzschild radius for Sun is about 3 km and for Earth about 1 cm.

See also: → Schwarzschild black hole; → radius.

A region of infinite → space-time curvature postulated to lie within a → black hole.

See also: → Schwarzschild black hole; → singularity.

A region of infinite → space-time curvature postulated to lie within a → black hole.

See also: → Schwarzschild black hole; → singularity.

The first exact solution of → Einstein’s field equations that describes the → space-time geometry outside a spherical distribution of mass.

See also: Briefly following Einstein’s publication of → General Relativity, Karl Schwarzschild discovered this solution in 1916
(Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, Phys.-Math. Klasse, 189); → Schwarzschild black hole.

The first exact solution of → Einstein’s field equations that describes the → space-time geometry outside a spherical distribution of mass.

See also: Briefly following Einstein’s publication of → General Relativity, Karl Schwarzschild discovered this solution in 1916
(Sitzungsberichte der Königlich Preussischen Akademie der Wissenschaften zu Berlin, Phys.-Math. Klasse, 189); → Schwarzschild black hole.

The condition in stellar interior under which → convection occurs. It is expressed as:

|dT/dr|_ad < |dT/dr|rad,

where the indices ad and rad stand for adiabatic and radiative respectively. This condition can also be expressed as: ∇_ad<∇_rad, where ∇ = d lnT / d lnP = P dT / T dP with T and P denoting temperature and pressure respectively.
More explicitly, in order for convection to occur the adiabatic temperature gradient should be smaller than the actual temperature gradient of the surrounding gas, which is given by the radiative temperature gradient if convection does not occur.
Suppose a hotter → convective cell or gas bubble rises accidentally by a small distance in height. It gets into a layer with a lower gas pressure and therefore expands. Without any heat exchange with the surrounding medium it expands and cools adiabatically. If during this rise and → adiabatic expansion the change in temperature is smaller than in the medium the gas bubble remains hotter than the medium. The expansion of the gas bubble, adjusting to the pressure of the medium, happens very fast, with the speed of sound. It is therefore assumed that the pressure in the gas bubble and in the surroundings is the same and therefore the higher temperature gas bubble will have a lower density than the surrounding gas. The
→ buoyancy force will therefore accelerate it upward. This always occurs if the adiabatic change of temperature during expansion is smaller than the change of temperature with gas pressure in the surroundings. It is assumed that
the mean molecular weight is the same in the rising bubble and the medium. See also → Ledoux’s criterion;
→ mixing length.

See also: Named after Karl Schwarzschild (1873-1916), German mathematical physicist (1906 Göttinger Nachrichten No 1, 41); → criterion.

The condition in stellar interior under which → convection occurs. It is expressed as:

|dT/dr|_ad < |dT/dr|rad,

where the indices ad and rad stand for adiabatic and radiative respectively. This condition can also be expressed as: ∇_ad<∇_rad, where ∇ = d lnT / d lnP = P dT / T dP with T and P denoting temperature and pressure respectively.
More explicitly, in order for convection to occur the adiabatic temperature gradient should be smaller than the actual temperature gradient of the surrounding gas, which is given by the radiative temperature gradient if convection does not occur.
Suppose a hotter → convective cell or gas bubble rises accidentally by a small distance in height. It gets into a layer with a lower gas pressure and therefore expands. Without any heat exchange with the surrounding medium it expands and cools adiabatically. If during this rise and → adiabatic expansion the change in temperature is smaller than in the medium the gas bubble remains hotter than the medium. The expansion of the gas bubble, adjusting to the pressure of the medium, happens very fast, with the speed of sound. It is therefore assumed that the pressure in the gas bubble and in the surroundings is the same and therefore the higher temperature gas bubble will have a lower density than the surrounding gas. The
→ buoyancy force will therefore accelerate it upward. This always occurs if the adiabatic change of temperature during expansion is smaller than the change of temperature with gas pressure in the surroundings. It is assumed that
the mean molecular weight is the same in the rising bubble and the medium. See also → Ledoux’s criterion;
→ mixing length.

See also: Named after Karl Schwarzschild (1873-1916), German mathematical physicist (1906 Göttinger Nachrichten No 1, 41); → criterion.

1. The study of the physical and natural phenomena, especially by using systematic observation and experiment.
   

2. A systematically organized body of knowledge about a particular subject.
   See also: → knowledge,
   → cognition.

Etymology (EN): M.E., from O.Fr. science, from L. scientia “knowledge,” from sciens (genitive scientis), pr.p. of scire “to know,” probably originally “to separate one thing from another, to distinguish,” related to scindere “to cut, divide;” PIE base *skei- “to cut, split;” cf. Pers. gosastan “to tear, cut, break,” from Mid.Pers. wisistan “to break, split,” Av. saed-, sid- “to split, break,” asista- “unsplit, unharmed;” Skt. chid- “to split, break, cut off;” Gk. skhizein “to split;”
Goth. skaidan; O.E. sceadan “to divide, separate.”

Etymology (PE): Dâneš, verbal noun of dân-, dânestan “to know” (Mid.Pers. dânistan “to know”), variant šenâxtan, šenâs- “to recognize, to know” (Mid.Pers. šnâxtan, šnâs- “to know, recognize”);
O.Pers./Av. xšnā- “to know, learn, come to know, recognize;” cf. Skt. jñā- “to recognize, know,” jānāti “he knows;” Gk. gignoskein “to know, think, judge,” cognate with L. gnoscere, noscere “to come to know” (Fr. connaître; Sp. conocer); P.Gmc. *knoeanan; O.E. cnawan, E. know; Rus. znat “to know;” PIE base *gno- “to know.”

1. The study of the physical and natural phenomena, especially by using systematic observation and experiment.
   

2. A systematically organized body of knowledge about a particular subject.
   See also: → knowledge,
   → cognition.

Etymology (EN): M.E., from O.Fr. science, from L. scientia “knowledge,” from sciens (genitive scientis), pr.p. of scire “to know,” probably originally “to separate one thing from another, to distinguish,” related to scindere “to cut, divide;” PIE base *skei- “to cut, split;” cf. Pers. gosastan “to tear, cut, break,” from Mid.Pers. wisistan “to break, split,” Av. saed-, sid- “to split, break,” asista- “unsplit, unharmed;” Skt. chid- “to split, break, cut off;” Gk. skhizein “to split;”
Goth. skaidan; O.E. sceadan “to divide, separate.”

Etymology (PE): Dâneš, verbal noun of dân-, dânestan “to know” (Mid.Pers. dânistan “to know”), variant šenâxtan, šenâs- “to recognize, to know” (Mid.Pers. šnâxtan, šnâs- “to know, recognize”);
O.Pers./Av. xšnā- “to know, learn, come to know, recognize;” cf. Skt. jñā- “to recognize, know,” jānāti “he knows;” Gk. gignoskein “to know, think, judge,” cognate with L. gnoscere, noscere “to come to know” (Fr. connaître; Sp. conocer); P.Gmc. *knoeanan; O.E. cnawan, E. know; Rus. znat “to know;” PIE base *gno- “to know.”

A form of fiction that draws imaginatively on scientific knowledge and speculation in its plot, setting, theme, etc. (Dictionary.com).

See also: → science; → fiction.

A form of fiction that draws imaginatively on scientific knowledge and speculation in its plot, setting, theme, etc. (Dictionary.com).

See also: → science; → fiction.

Of or pertaining to science or the sciences.
Systematic or accurate in the manner of an exact science.

Etymology (EN): From M.Fr. scientifique, from M.L. scientificus “pertaining to science,” from L. scientia “knowledge,” → science,

• -ficus “making,” from facere “to make.” → -ic

Etymology (PE): Dâneši, dânešik, from dâneš, → science

• -i, -ik, → ic.

Of or pertaining to science or the sciences.
Systematic or accurate in the manner of an exact science.

Etymology (EN): From M.Fr. scientifique, from M.L. scientificus “pertaining to science,” from L. scientia “knowledge,” → science,

• -ficus “making,” from facere “to make.” → -ic

Etymology (PE): Dâneši, dânešik, from dâneš, → science

• -i, -ik, → ic.

An agreement by competent observers of a series of observations of the same phenomena. From time to time scientific facts are revised by additional data
(G. Smooth, Lawrence Berkeley Lab website).

See also: → scientific; → fact.

An agreement by competent observers of a series of observations of the same phenomena. From time to time scientific facts are revised by additional data
(G. Smooth, Lawrence Berkeley Lab website).

See also: → scientific; → fact.

The process by which scientists, collectively and over time, endeavor to construct an accurate (that is, reliable, consistent, and non-arbitrary) representation of the world.
The scientific method has four steps:

1. Observation and description of a phenomenon or group of phenomena.
   

2. Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.
   

3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.
   

4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.
   

If the experiments bear out the hypothesis it may come to be regarded as a theory or law of nature. If the experiments do not bear out the hypothesis, it must be rejected or modified. What is key in the description of the scientific method just given is the predictive power (the ability to get more out of the theory than you put in) of the hypothesis or theory, as tested by experiment. It is often said in science that theories can never be proved, only disproved. There is always the possibility that a new observation or a new experiment will conflict with a long-standing theory (Frank L. H. Wolfs, University of Rochester).

See also: → scientific; → method.

The process by which scientists, collectively and over time, endeavor to construct an accurate (that is, reliable, consistent, and non-arbitrary) representation of the world.
The scientific method has four steps:

1. Observation and description of a phenomenon or group of phenomena.
   

2. Formulation of an hypothesis to explain the phenomena. In physics, the hypothesis often takes the form of a causal mechanism or a mathematical relation.
   

3. Use of the hypothesis to predict the existence of other phenomena, or to predict quantitatively the results of new observations.
   

4. Performance of experimental tests of the predictions by several independent experimenters and properly performed experiments.
   

If the experiments bear out the hypothesis it may come to be regarded as a theory or law of nature. If the experiments do not bear out the hypothesis, it must be rejected or modified. What is key in the description of the scientific method just given is the predictive power (the ability to get more out of the theory than you put in) of the hypothesis or theory, as tested by experiment. It is often said in science that theories can never be proved, only disproved. There is always the possibility that a new observation or a new experiment will conflict with a long-standing theory (Frank L. H. Wolfs, University of Rochester).

See also: → scientific; → method.

A compact format for writing very large or very small numbers. Numbers are made up of three parts: the coefficient, the base and the exponent.
For example 3.58 x 10⁴ is the scientific notation for 35,800.

See also: → scientific; → notation.

A compact format for writing very large or very small numbers. Numbers are made up of three parts: the coefficient, the base and the exponent.
For example 3.58 x 10⁴ is the scientific notation for 35,800.

See also: → scientific; → notation.

The quality of the practices and theories that aim at establishing reproducible regularities
in phenomena by using experimental method and providing a clearly formulated description.

See also: → scientific + → -ity.

The quality of the practices and theories that aim at establishing reproducible regularities
in phenomena by using experimental method and providing a clearly formulated description.

See also: → scientific + → -ity.

An expert in science, especially one of the physical or natural sciences. → scholar.

Etymology (EN): From → science + -ist an agent noun suffix.

Etymology (PE): Dânešmand, from dâneš, → science, + -mand suffix of possession.

An expert in science, especially one of the physical or natural sciences. → scholar.

Etymology (EN): From → science + -ist an agent noun suffix.

Etymology (PE): Dânešmand, from dâneš, → science, + -mand suffix of possession.

1. Rapid variation in the brightness, wavelength, and mean position of stars caused by turbulence in the Earth’s atmosphere.
   

2. In radio astronomy, rapid fluctuations in the detected intensity of radiation from compact cosmic radio sources due to disturbances in ionized gas through which the radiation has passed. → interstellar scintillation.

Etymology (EN): From L. scintillationem (nominative scintillatio),
from scintillatus p.p. of scintillare “to send out sparks, to flash,” from
scintilla “particle of fire, spark.”

Etymology (PE): Susu, from su “light,” related to suz “burning,” present stem of suxtan; Mid.Pers. sôxtan, sôzidan “to burn,” Av. base saoc- “to burn, inflame” sūcā- “brilliance,” upa.suxta- “inflamed;” cf. Skt. śoc- “to light, glow, burn,” śocati “burns,”
śoka- “light, flame;” PIE base *(s)keuk- “to shine.”

1. Rapid variation in the brightness, wavelength, and mean position of stars caused by turbulence in the Earth’s atmosphere.
   

2. In radio astronomy, rapid fluctuations in the detected intensity of radiation from compact cosmic radio sources due to disturbances in ionized gas through which the radiation has passed. → interstellar scintillation.

Etymology (EN): From L. scintillationem (nominative scintillatio),
from scintillatus p.p. of scintillare “to send out sparks, to flash,” from
scintilla “particle of fire, spark.”

Etymology (PE): Susu, from su “light,” related to suz “burning,” present stem of suxtan; Mid.Pers. sôxtan, sôzidan “to burn,” Av. base saoc- “to burn, inflame” sūcā- “brilliance,” upa.suxta- “inflamed;” cf. Skt. śoc- “to light, glow, burn,” śocati “burns,”
śoka- “light, flame;” PIE base *(s)keuk- “to shine.”

A device for detecting and measuring ionizing radiation by means of flashes produced when the radiation particles strike a sensitive layer of phosphor.

See also: → scintillation; → counter.

A device for detecting and measuring ionizing radiation by means of flashes produced when the radiation particles strike a sensitive layer of phosphor.

See also: → scintillation; → counter.

Relating to a constraint or system that does not contain time explicitly. For example, a pendulum with an inextensible string of length l₀ is described by the equation: x² + y² = l₀² is both → holonomic and scleronomous.

Etymology (EN): From Gk. sclero-, from skleros “hard” + -nomous, → -nomy.

Etymology (PE): Saxtdâtik, from saxt, → hard,

• dâtik, → -nomy.

Relating to a constraint or system that does not contain time explicitly. For example, a pendulum with an inextensible string of length l₀ is described by the equation: x² + y² = l₀² is both → holonomic and scleronomous.

Etymology (EN): From Gk. sclero-, from skleros “hard” + -nomous, → -nomy.

Etymology (PE): Saxtdâtik, from saxt, → hard,

• dâtik, → -nomy.

The Scorpion. A large and impressive constellation in the → Zodiac, which lies between → Libra to the west and → Sagittarius to the east. Scorpius is located in the southern hemisphere near the center of the Milky Way at approximately 17h right ascension, -40° declination. The bright, red star → Antares marks the heart of the scorpion. The constellation contains deep sky objects such as the open clusters M6 and M7, and the globular clusters M4 and M80. Also in the southern end of the constellation there is the open star cluster NGC 6231. Abbreviation: Sco; genitive: Scorpii.

Etymology (EN): M.E., from O.Fr. scorpion, from L. scorpionem (nominative scorpio), from Gk. skorpios “a scorpion,” from PIE base *(s)ker- “to cut,” → shear. According to Gk. mythology, the constellation represents a giant scorpion sent forth by the earth-goddess Gaia to kill the giant Orion when he threatened to slay all the beasts of the earth. Orion and the Scorpion were afterward placed amongst the stars as a pair of constellations. The two opponents are never seen in the sky at the same time, for one constellation sets as the other rises. The scorpion’s claws were originally formed by Libra.

Etymology (PE): Každom “scorpion,” variants kajdom, gaždom literally “crooked tail,”
from Mid.Pers. gazdum literally “stinging tail,” from gaz present stem of gazidan (also Mod.Pers.) “to sting, to bite” + dum, dumb (Mod.Pers. dom, domb) “tail;”
Av. duma- “tail.”

The Scorpion. A large and impressive constellation in the → Zodiac, which lies between → Libra to the west and → Sagittarius to the east. Scorpius is located in the southern hemisphere near the center of the Milky Way at approximately 17h right ascension, -40° declination. The bright, red star → Antares marks the heart of the scorpion. The constellation contains deep sky objects such as the open clusters M6 and M7, and the globular clusters M4 and M80. Also in the southern end of the constellation there is the open star cluster NGC 6231. Abbreviation: Sco; genitive: Scorpii.

Etymology (EN): M.E., from O.Fr. scorpion, from L. scorpionem (nominative scorpio), from Gk. skorpios “a scorpion,” from PIE base *(s)ker- “to cut,” → shear. According to Gk. mythology, the constellation represents a giant scorpion sent forth by the earth-goddess Gaia to kill the giant Orion when he threatened to slay all the beasts of the earth. Orion and the Scorpion were afterward placed amongst the stars as a pair of constellations. The two opponents are never seen in the sky at the same time, for one constellation sets as the other rises. The scorpion’s claws were originally formed by Libra.

Etymology (PE): Každom “scorpion,” variants kajdom, gaždom literally “crooked tail,”
from Mid.Pers. gazdum literally “stinging tail,” from gaz present stem of gazidan (also Mod.Pers.) “to sting, to bite” + dum, dumb (Mod.Pers. dom, domb) “tail;”
Av. duma- “tail.”

The first and the brightest X-ray source in the sky, after the Sun, discovered in 1962. Scorpius X-1 is a low-mass → X-ray binary consisting of a compact object like a → neutron star or a → black hole, and a low-mass stellar companion. The compact object has a mass of 1.4 → solar masses and the companion 0.42 solar masses. The orbital period is 18.9 hours, and the system lies at a distance of about 9,000 → light-years. The X-rays come from → accretion, where material from the companion overflows its → Roche lobe and spirals down onto the compact object. The luminosity results from the transformation of the falling material’s → gravitational potential energy to heat by → viscosity in the → accretion disk.

See also: Named such by the discoverers (Giacconi et al. 1962), because it was the first extrasolar → X-ray source of the sky detected in the constellation → Scorpius.

The first and the brightest X-ray source in the sky, after the Sun, discovered in 1962. Scorpius X-1 is a low-mass → X-ray binary consisting of a compact object like a → neutron star or a → black hole, and a low-mass stellar companion. The compact object has a mass of 1.4 → solar masses and the companion 0.42 solar masses. The orbital period is 18.9 hours, and the system lies at a distance of about 9,000 → light-years. The X-rays come from → accretion, where material from the companion overflows its → Roche lobe and spirals down onto the compact object. The luminosity results from the transformation of the falling material’s → gravitational potential energy to heat by → viscosity in the → accretion disk.

See also: Named such by the discoverers (Giacconi et al. 1962), because it was the first extrasolar → X-ray source of the sky detected in the constellation → Scorpius.

The nearest → OB association to the Sun. It contains several hundred stars, mostly → B stars which concentrate in the three subgroups: Upper Scorpius, Upper Centaurus Lupus, and Lower Centaurus Crux. Upper Scorpius is the youngest subgroup, Upper Centaurus Lupus the oldest subgroup of the association.

Isochrone fitting to the Hertzsprung-Russell diagram indicates that the star formation occurred some 5-20 Myr ago.
Based on data from the → Hipparcos catalog, it turns out that the Sco-Cen association lies at a distance of 118-145 → parsecs, with the exact value depending on the subgroup of the association.

The Sco-Cen association is probably a member of the → Gould Belt (Preibisch & Mamajek, 2008, astro-ph/0809.0407).

See also: → Scorpius; → Centaurus; → association.

The nearest → OB association to the Sun. It contains several hundred stars, mostly → B stars which concentrate in the three subgroups: Upper Scorpius, Upper Centaurus Lupus, and Lower Centaurus Crux. Upper Scorpius is the youngest subgroup, Upper Centaurus Lupus the oldest subgroup of the association.

Isochrone fitting to the Hertzsprung-Russell diagram indicates that the star formation occurred some 5-20 Myr ago.
Based on data from the → Hipparcos catalog, it turns out that the Sco-Cen association lies at a distance of 118-145 → parsecs, with the exact value depending on the subgroup of the association.

The Sco-Cen association is probably a member of the → Gould Belt (Preibisch & Mamajek, 2008, astro-ph/0809.0407).

See also: → Scorpius; → Centaurus; → association.

Vision that occurs when the eye is dark-adapted. In scotopic vision, the level of luminance is so low that the retinal cones are not
stimulated, and there is no color vision. Same as scotopia; → dark adaptation.

Etymology (EN): Scotopic, from L. Gk. skoto- combining form of skotos “darkness” + -opia akin to ope “view, look,” ops “eye, face;” → vision.

Etymology (PE): Did, → vision; târiki noun from târik “dark,” Mid.Pers. târig “dark,” târ “darkness,” Av. taθra- “darkness,” taθrya- “dark,” cf. Skt. támisrâ- “darkness, dark night,” L. tenebrae “darkness,” Hittite taš(u)uant- “blind,” O.H.G. demar “twilight.”

Vision that occurs when the eye is dark-adapted. In scotopic vision, the level of luminance is so low that the retinal cones are not
stimulated, and there is no color vision. Same as scotopia; → dark adaptation.

Etymology (EN): Scotopic, from L. Gk. skoto- combining form of skotos “darkness” + -opia akin to ope “view, look,” ops “eye, face;” → vision.

Etymology (PE): Did, → vision; târiki noun from târik “dark,” Mid.Pers. târig “dark,” târ “darkness,” Av. taθra- “darkness,” taθrya- “dark,” cf. Skt. támisrâ- “darkness, dark night,” L. tenebrae “darkness,” Hittite taš(u)uant- “blind,” O.H.G. demar “twilight.”

1. A large, usually flat surface onto which an image is projected for viewing.
   

2. The portion of a computer terminal or monitor upon which information is displayed.

Etymology (EN): M.E. screne; O.Fr. escren “a screen against heat,” from M.Du. scherm “screen, cover,” or Frank. *skrank “barrier;” cf. O.H.G. skirm, skerm “protection,” scrank “barrier;” Ger. Schrank “cupboard.”

Etymology (PE): Pardé, from Mid.Pers. pardag “curtain, veil, covering;” loaned in Armenian partak “veil,” and Georgian p’ardag-i “curtain;” cognate with Gk. pelas, pella, L. pellis “skin;” O.E. filmen “thin skin;” PIE root *pel- “to cover.”

1. A large, usually flat surface onto which an image is projected for viewing.
   

2. The portion of a computer terminal or monitor upon which information is displayed.

Etymology (EN): M.E. screne; O.Fr. escren “a screen against heat,” from M.Du. scherm “screen, cover,” or Frank. *skrank “barrier;” cf. O.H.G. skirm, skerm “protection,” scrank “barrier;” Ger. Schrank “cupboard.”

Etymology (PE): Pardé, from Mid.Pers. pardag “curtain, veil, covering;” loaned in Armenian partak “veil,” and Georgian p’ardag-i “curtain;” cognate with Gk. pelas, pella, L. pellis “skin;” O.E. filmen “thin skin;” PIE root *pel- “to cover.”

A character used for on-screen → display. See also → printer font.

See also: → screen; → font.

A character used for on-screen → display. See also → printer font.

See also: → screen; → font.

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

See also: → screen; → coulomb; → interaction.

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

See also: → screen; → coulomb; → interaction.

Same as → shielding effect.

See also: → screen; → effect.

Same as → shielding effect.

See also: → screen; → effect.

A piece of metal, consisting of a threaded and usually tapered shank that has a slotted head by which it is turned into something in order to fasten things together.

Etymology (EN): M.E. scrwe, screw, from M.Fr. escroue “nut, cylindrical socket,” of uncertain origin.

Etymology (PE): Pic “screw,” present stem of picidan “to twist, entwine, coil.”

A piece of metal, consisting of a threaded and usually tapered shank that has a slotted head by which it is turned into something in order to fasten things together.

Etymology (EN): M.E. scrwe, screw, from M.Fr. escroue “nut, cylindrical socket,” of uncertain origin.

Etymology (PE): Pic “screw,” present stem of picidan “to twist, entwine, coil.”

A minor and faint → constellation in the southern sky at 0h 30m → right ascension, 33° south → declination. Its brightest star is variable with a mean magnitude of only 4.31. Sculptor contains the south Galactic pole. It also contains the → Sculptor Dwarf, which is a member of the → Local Group. Abbreviation: Scl; Genitive: Sculptoris.

Etymology (EN): Sculptor was introduced by Nicolas Louis de Lacaille (1713-1762).
He originally named it Apparatus Sculptoris “the sculptor’s studio,” but the name was later shortened. From L. sculp(ere) “to carve” + a suffix forming personal agent nouns.

Etymology (PE): Peykartarâš, from peykar “form, figure, body” (from Mid.Pers. pahikar “picture, image;” from O.Pers. patikara- “picture, (sculpted) likeness,” from patiy “against” (Av. paiti; Skt. prati; Gk. poti/proti + kara- “doer, maker,” from kar- “to do, make, build;” Av. kar-; Skt. kr-; cf. Skt. pratikrti- “an image, likeness, model; counterpart”) + tarâš “cutter,” 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 fom 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 minor and faint → constellation in the southern sky at 0h 30m → right ascension, 33° south → declination. Its brightest star is variable with a mean magnitude of only 4.31. Sculptor contains the south Galactic pole. It also contains the → Sculptor Dwarf, which is a member of the → Local Group. Abbreviation: Scl; Genitive: Sculptoris.

Etymology (EN): Sculptor was introduced by Nicolas Louis de Lacaille (1713-1762).
He originally named it Apparatus Sculptoris “the sculptor’s studio,” but the name was later shortened. From L. sculp(ere) “to carve” + a suffix forming personal agent nouns.

Etymology (PE): Peykartarâš, from peykar “form, figure, body” (from Mid.Pers. pahikar “picture, image;” from O.Pers. patikara- “picture, (sculpted) likeness,” from patiy “against” (Av. paiti; Skt. prati; Gk. poti/proti + kara- “doer, maker,” from kar- “to do, make, build;” Av. kar-; Skt. kr-; cf. Skt. pratikrti- “an image, likeness, model; counterpart”) + tarâš “cutter,” 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 fom 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 → dwarf elliptical galaxy that is a satellite of our → Milky Way.
It lies about 285,000 → light-years away in the constellation → Sculptor, and has an → absolute magnitude of -11.28 and a mass of about 3 million → solar masses. The Sculptor Dwarf is a → metal-deficient galaxy containing only 4 percent of the oxygen and carbon elements in our own Galaxy.

See also: → Sculptor; → dwarf; → elliptical; → galaxy.

A → dwarf elliptical galaxy that is a satellite of our → Milky Way.
It lies about 285,000 → light-years away in the constellation → Sculptor, and has an → absolute magnitude of -11.28 and a mass of about 3 million → solar masses. The Sculptor Dwarf is a → metal-deficient galaxy containing only 4 percent of the oxygen and carbon elements in our own Galaxy.

See also: → Sculptor; → dwarf; → elliptical; → galaxy.

The nearest group of galaxies to our → Local Group, lying near the south Galactic pole at about 10 million → light-years distance. The Sculptor Group is dominated by five galaxies, four spiral (NGC 247, 253, 300, and 7793) and one irregular (NGC 55). The brightest of the five is NGC 253. The nearest galaxy in this group is NGC 55 which at a distance of 5 million light-years lies on the border of the Local Group.

See also: → Sculptor; → group.

The nearest group of galaxies to our → Local Group, lying near the south Galactic pole at about 10 million → light-years distance. The Sculptor Group is dominated by five galaxies, four spiral (NGC 247, 253, 300, and 7793) and one irregular (NGC 55). The brightest of the five is NGC 253. The nearest galaxy in this group is NGC 55 which at a distance of 5 million light-years lies on the border of the Local Group.

See also: → Sculptor; → group.

The Shield. A small constellation in the southern Milky Way, at 18h 40m right ascension, 10° south declination. Its brightest star has a visual magnitude of 3.85. Scutum contains several open clusters, as well as a globular cluster and a planetary nebula. The two best known deep sky objects in Scutum
are M11 (NGC 6705), a dense open cluster, and M26, another open cluster also known as NGC 6694. The globular cluster NGC 6712 and the planetary nebula IC 1295 can be found in the eastern part of the constellation. Abbreviation: Sct; Genitive: Scuti.

Etymology (EN): Scutum was created by Johannes Hevelius in 1683, who originally named it L. Scutum Sobiescianum “the shield of Sobieski” to commemorate the victory of the Polish forces led by King John III Sobieski in the Battle of Vienna, and thus refers to Sobieski’s Janina Coat of Arms. Later, the name was shortened to Scutum “shield.”

Etymology (PE): Separ “shield,” from Mid.Pers. spar “shield;” cf. Skt. phalaka- “board, lath, leaf, shield,” phálati “(he) splits;” Gk. aspalon “skin, hide,” spolas “flayed skin,” sphalassein “to cleave, to disrupt;” O.H.G. spaltan “to split;” Goth. spilda “board;” PIE base *(s)p(h)el- “to split, to break off.”

The Shield. A small constellation in the southern Milky Way, at 18h 40m right ascension, 10° south declination. Its brightest star has a visual magnitude of 3.85. Scutum contains several open clusters, as well as a globular cluster and a planetary nebula. The two best known deep sky objects in Scutum
are M11 (NGC 6705), a dense open cluster, and M26, another open cluster also known as NGC 6694. The globular cluster NGC 6712 and the planetary nebula IC 1295 can be found in the eastern part of the constellation. Abbreviation: Sct; Genitive: Scuti.

Etymology (EN): Scutum was created by Johannes Hevelius in 1683, who originally named it L. Scutum Sobiescianum “the shield of Sobieski” to commemorate the victory of the Polish forces led by King John III Sobieski in the Battle of Vienna, and thus refers to Sobieski’s Janina Coat of Arms. Later, the name was shortened to Scutum “shield.”

Etymology (PE): Separ “shield,” from Mid.Pers. spar “shield;” cf. Skt. phalaka- “board, lath, leaf, shield,” phálati “(he) splits;” Gk. aspalon “skin, hide,” spolas “flayed skin,” sphalassein “to cleave, to disrupt;” O.H.G. spaltan “to split;” Goth. spilda “board;” PIE base *(s)p(h)el- “to split, to break off.”

A spiral arm of our Galaxy located between the Sagittarius Arm and the Norma Arm, though it is rather less prominent than either of these two better defined spiral arms. It originates relatively close to the Sun’s present position in the Galaxy, and follows a sweeping arc of about 80,000 light years to the opposite side of the Galactic disk.

See also: → Scutum; → Crux; → arm.

A spiral arm of our Galaxy located between the Sagittarius Arm and the Norma Arm, though it is rather less prominent than either of these two better defined spiral arms. It originates relatively close to the Sun’s present position in the Galaxy, and follows a sweeping arc of about 80,000 light years to the opposite side of the Galactic disk.

See also: → Scutum; → Crux; → arm.

An agricultural implement consisting of a long, curving blade fastened at an angle to a handle, for cutting grass, grain, etc., by hand (Dictionary.com).

Etymology (EN): M.E. sythe, sithe, from O.E. sithe, sigdi “sickle;” cf. West Frisian seine “scythe,” Du. zicht “sickle,” Ger. Sense “scythe;” from PIE root *sek- “to cut.”

Etymology (PE): Dahre “scythe,” variant of dâs, → sickle; dialectal variants (Dari Yazd) dare, (Laki) dara “butcher’s cleaver,” (Gilân, Lâsgard, Sorxe) dâra, (Tabari) dahra, dâhra, darra.

An agricultural implement consisting of a long, curving blade fastened at an angle to a handle, for cutting grass, grain, etc., by hand (Dictionary.com).

Etymology (EN): M.E. sythe, sithe, from O.E. sithe, sigdi “sickle;” cf. West Frisian seine “scythe,” Du. zicht “sickle,” Ger. Sense “scythe;” from PIE root *sek- “to cut.”

Etymology (PE): Dahre “scythe,” variant of dâs, → sickle; dialectal variants (Dari Yazd) dare, (Laki) dara “butcher’s cleaver,” (Gilân, Lâsgard, Sorxe) dâra, (Tabari) dahra, dâhra, darra.