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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 232 Search : ist
characteristic mass
  جرم ِ سرشتاری   
jerm-e sereštâri

Fr.: masse caractéristique   

A typical or most likely mass for the formation of an astronomical object. In current star formation models, it is of order of a few tenths of a → solar mass.

characteristic; → mass.

characteristic thermal energy
  کاروژ ِ گرمایی ِ سرشتاری   
kâruž-e garmâyi-ye sereštâri

Fr.: énergie thermique caractéristique   

The quantity kT in the → Maxwell-Boltzmann distribution law, where k is → Boltzmann's constant and T the gas temperature. See also → thermal energy.

characteristic; → thermal; → energy

charge distribution
  واباژش ِ بار   
vâbâžeš-e bâr

Fr.: distribution des charges   

The way a number of → electric charges are arranged in space with respect to the point of observation.

charge; → distribution.

chemistry
  شیمی   
šimi (#)

Fr.: chimie   

The science of the composition, structure, properties, and reactions of chemical elements and compounds and their interactions with matter and energy.

Chemistry, from chemist, from Gk. chemia "alchemy" + -ry, from M.E. -rie, from O.Fr.

Šimi, from Fr. as above.

chi-square distribution
  واباژش ِ خی-دو   
vâbâžeš-e Xi-do

Fr.: loi du chi-deux   

A probability density function, denoted χ2, that gives the distribution of the sum of squares of k independent random variables, each being drawn from the normal distribution with zero mean and unit variance. The integer k is the number of degrees of freedom. The distribution has a positive skew; the skew is less with more degrees of freedom. As degrees of freedom increase, the chi-square distribution approaches a normal distribution. The most common application is chi-square tests for goodness of fit of an observed distribution to a theoretical one. If χ2 = 0 the agreement is perfect.

Chi Gk. letter of alphabet; → square; → distribution.

Vâbâžeš, → distribution; do, → two.

Christoffel symbol
  نماد ِ کریستوفل   
namâd-e Christoffel (#)

Fr.: symbole de Christoffel   

A abbreviated notation for various functions associated with quadratic differential forms. Each Christoffel symbol is essentially a triplet of three indices, i, j and k, where each index can assume values from 1 to 2 for the case of two variables, or from 1 to n in the case of a quadratic form in n variables. Christoffel symbols appear in many calculations in geometry where non-Cartesian coordinates are used. These symbols are fundamental in the study of tensor analysis.

Named after Elwin Bruno Christoffel (1829-1900), a German mathematician; → symbol.

comoving distance
  اپست ِ هم‌میاو   
apest-e ham-miyâv

Fr.: distance comobile   

1) A distance in → comoving coordinates between two points in space at a given cosmological time. In other words, the distance between two nearby objects in the Universe which remains constant with epoch if the two objects are moving with the → Hubble flow. More specifically, it is the → proper distance divided by the ratio of the → scale factor of the Universe between then, a(t)em, and now, a(t)obs: DC = Dproper . [a(t)obs/a(t)em]. In terms of → redshift (z), it is the proper distance multiplied by (1 + z). At the present epoch, i.e. a = a(tobs) = 1, DC = Dproper. If the objects have no peculiar velocity their comoving distance at any time is the same as their distance today.
The comoving distance of the → cosmic horizon is about 48 × 109light-years.

2) Transverse comoving distance: In a non-flat Universe, the comoving distance between two events at the same → redshift but separated on the sky by some angle. It is expressed by trigonometric functions of → curvature, → comoving distance, and the → Hubble distance accounting for the curvature of space. In a flat universe (Ωk) it is the same as the → comoving distance.

3) Line-of-sight comoving distance: The total line-of-sight comoving distance from us to a distant object computed by integrating the infinitesimal comoving distance contributions between nearby events along the radial ray from the time temit, when the light from the object was emitted, to the time tobs, when the object is observed.

comoving; → distance.

consist
  ۱) هانسیده شدن؛ ۲) هانسیدن؛ ۳) هانسگار بودن   
1) hânesidé šodan; 2) hânesidan; 3) hânesgâr budan

Fr.: consister   

1) (followed by of) To be composed (of); be formed (of).
2) (followed by: in or of) To have its existence (in); lie (in); be expressed (by).
3) To be compatible or consistent; accord (TheFreeDictionary.com).

M.E., from M.Fr. consister, from L. consistere "to stand firm, take a standing position, halt," from → com- "with, together" + sistere "to place," causative of stare "to stand, be standing," cognate with Pers. ist-/istâdan.

Hânesidan, literally "to put together," from prefix hâ-, → com-, + nesidan "to put, place," variant of nehidan, nehâdan "to put, place," → position.

consistency
  هانسگاری   
hânesgâri

Fr.: cohérence, consistance   

1) Agreement or accordance with facts, form, or characteristics previously shown or stated.
2) Agreement or harmony between parts of something complex; compatibility.
3) Physics: Degree of → viscosity or firmness.
4) The state or quality of holding or sticking together and retaining shape.
5) Conformity with previous attitudes, behaviour, practice, etc. (TheFreeDictionary.com).

consist; → -ency.

consistent
  هانسگار   
hânesgâr

Fr.: cohérent, consistant   

1) Showing consistency; not self-contradictory.
2) In agreement or harmony (with); accordant.
3a) Maths.: The quality of an equation if it has a solution.
3b) Maths.: (of a set of equations) Satisfied by at least one solution.
4) Logic: (of a formal system) Not permitting the deduction of a contradiction from the axioms (TheFreeDictionary.com).

consist; → -ent.

Hânesgâr, from hânes- present stem of hânesidan, → consist, + -gâr agect noun suffix (on the model of sâzgâr), → -or.

cosmic distance scale
  مرپل ِ دورای ِ کیهانی   
marpel-e durâ-ye keyhâni

Fr.: échelle des distances cosmiques   

Measurement of the distances to the farthest objects in the Universe based on a bootstrapping series of methods, each applicable to more distant objects, and each dependent on the previous methods.

cosmic; → distance; → scale.

cosmochemistry
  کیهان-شیمی   
keyhân-šimi

Fr.: cosmochimie   

The study of the chemical composition of the universe and the processes that produced those compositions. Cosmochemistry is an interdisciplinary science that overlaps with geochemistry, geology, astronomy, astrophysics, and geophysics.

cosmo-; → chemistry.

cosmological distance
  دورای ِ کیهان‌شناسیک، ~ کیهان‌شناختی   
durâ-ye keyhânšenâsik, ~ keyhânšenâxti

Fr.: distance cosmologique   

The distance to a remote galaxy based on its redshift assuming that the redshift is caused by the → Doppler effect and reflects the general expansion of the Universe.

cosmological; → distance .

cumulative distribution function
  کریای ِ واباژش ِ کومشی   
karyâ-ye vâbâžeš-e kumeši

Fr.: fonction de distribution cumulée   

A function that gives the probability that a → random variable X is less than or equal to x, at each possible outcome: F(x) = P(X ≤ x), for -∞ < x < ∞. Same as → distribution function.

cumulative; → distribution; → function.

deist
  دادارباور، ایزدباور   
dâdâr-bâvar (#), izad-bâvar

Fr.: déiste   

A person who believes in → deism.

deism; → -ist

deterministic
  آترم‌باور   
âtarmbâvar

Fr.: déterministe   

Of, pertaining to, or dealing with → determinism.

From determinist + → -ic.

deterministic physics
  فیزیک ِ آترم‌باور   
fizik-e âtarmbâvar

Fr.: physique déterministe   

The classical representation of the laws of nature according to which a particular future state (B) will arise from a particular past one (A). In contrast to → quantum physics which deals with the probability for the transition from A to B.

Deterministic, adj. of determinism; → physics.

deterministic theory
  نگره‌ی ِ آترم‌باور   
negare-ye âtarmbâvar

Fr.: théorie déterministe   

A theory in which specification of the initial value of all relevant variables of the system is sufficient to calculate the past values and to predict the future values of such variables for any arbitrary time. Moreover, it is possible, for any arbitrary time, to assign a value to all the variables characterizing the system. In quantum mechanics, the time evolution of the → wave function, governed by the → Schrodinger equation, is deterministic. Quantum mechanics, however, is a non deterministic theory because of the probabilistic nature of the predictions for the values of the → observables of a quantum system.

deterministic; → theory.

distal ejecta
  اشاناک ِ دور   
ešânâk-e dur

Fr.: éjecta distaux   

Geology: Impact ejecta found at distances more than 5 crater radii from the rim of the source crater.

Distal, from dist(ant), → distance + → -al; → ejecta.

Ešânâk, → ejecta; dur, → distance.

distance
  اپست، دورا، دوری   
apest, durâ (#), duri (#)

Fr.: distance   

1) The separation/length in space/time between two things/events.
2) The state of being apart in space or time.
3) In cosmology four main distance definitions are used: → luminosity distance, → angular diameter distance, → comoving distance, and → light-travel distance. In a → flat Universe these four approaches give the same result for the present epoch for distances below 100 Mpc. In a non-flat Universe with the → Robertson-Walker metric they give different but related values.
See also:
apparent distance, → cosmic distance scale, → cosmological distance, → distance function, → distance modulus, → distance to the horizon, → focal distance, → Hubble distance, → perihelion distance, → polar distance, → proper distance, → redshift-distance relation, → velocity-distance relation, → zenith distance.

M.E., from O.Fr., from L. distantia "a standing apart," from distantem (nominative distans) "standing apart, separate, distant," pr.p. of distare "to stand apart," from → dis- "apart, off" + stare "to stand," (cf. Mod.Pers. istâdan "to stand," O.Pers./Av. sta- "to stand, stand still; set," Skt. sthâ- "to stand," Gk. histemi "put, place, weigh," stasis "a standing still").

Apest, literally "standing apart," from apa- prefix denoting "separation, away, off," → dis-, + est variant of ist, present stem of istâdan, to stand," as above;" cf. Choresmian bst "to stand apart," from *apa- + st- "to stand," → stand.
Durâ, duri, noun from dur "far, distant, remote," Mid.Pers. dur, O.Pers. dūra- "far (in time or space)," Av. dūra-, from dav- "to move away," cf. Skt. dūrá- "distant, far."

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