An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 130 Search : plan
Planck function
  کریای ِ پلانک   
karyâ-ye Planck

Fr.: fonction de Planck   

Same as → Planck's blackbody formula.

Planck; → function.

Planck length
  درازای ِ پلانک   
derâzâ-ye Planck (#)

Fr.: longueur de Planck   

The size limit, lP = √ (ħ G/ c3), about 10-33 cm, at which Einstein's notions of space-time are supposed to break down, and space is predicted to become "foam like."

Planck; → length.

Planck mass
  جرم ِ پلانک   
jerm-e Planck

Fr.: masse de Planck   

The unit of mass in Planck's system of physical units, mP = √ (ħ c/ G) = 2.176 x 10-8 kg. It is also the mass of a black hole whose Compton wavelength is comparable to its Schwarzschild radius.

Planck; → mass.

Planck postulate
  فراوَس ِ پلانک   
farâvas-e Planck

Fr.: postulat de Planck   

The postulate that the energy of oscillators in a blackbody is quantized by E = nhν, where n = 1, 2, 3, ..., h is Planck's constant, and ν the frequency.

Planck; → postulate.

Planck Satellite
  ماهواره‌ی ِ پلانک   
mâhvâre-ye Planck

Fr.: Satellite Planck   

A European Space Agency (ESA) mission to map the full sky in the 30 GHz to 1 THz range and to measure the → anisotropies of the → cosmic microwave background (CMB) with a sensitivity set by fundamental limits, i.e. photon noise and contamination by foregrounds. It was launched on 14 May 2009, together with the → Herschel Satellite. Its observing position is a halo orbit around the L2 → Lagrangian point, some 1.5 million km from Earth. Its → Gregorian-like off-axis telescope has an effective aperture of 1.5 m and images the sky on two sets of feed-horns. The Low Frequency Instrument (LFI, at frequencies 30, 44, 70 GHz) amplifies with High Electron Mobility Transistors cooled at 20 K the radiation collected by 13 horns. The High Frequency Instrument (HFI, at 100, 143, 217, 353, 545, 857 GHz) detects the shorter waves with 52 bolometers cooled at only 0.1 degree above the → absolute zero. Both instruments can detect both the total intensity and polarization of photons. The Planck mission is intended to provide maps with a sensitivity of a few micro-Kelvin and an angular resolution down to 5 arcmin, which is considered as a major improvement with respect to the Wilkinson Microwave Anisotropy Probe (→ WMAP) launched by the NASA in 2002. Planck will provide a major source of information relevant to several cosmological and astrophysical issues, such as testing theories of the early Universe and the origin of cosmic structure. It will also provide to astronomers 9 complete maps of the full sky at wavelengths from 0.3 mm to 1 cm, that complement the 4 maps taken by the → IRAS satellite in the 2.5 to 100 micrometer range.

Planck; → satellite.

Planck scale
  مرپل ِ پلانک   
marple-e Planck

Fr.: échelle de Plancck   

1) A general term for anything roughly the size of the → Planck length.
2) Similarly, an energy on the order of the → Planck energy.

Planck; → scale.

Planck spectrum
  بیناب ِ پلانک   
binâb-e Planck

Fr.: spectrum de Planck   

Same as → blackbody spectrum.

Planck; → spectrum.

Planck time
  زمان ِ پلانک   
zamân-e Planck

Fr.: temps de Planck   

The time representing the → Planck length divided by the → speed of light. It is expressed by: tP = (Għ/c5)1/2≅ 5.4 x 10-44 s, where G is the → gravitational constant, ħ is the → reduced Planck's constant, and c is the → speed of light. At the Planck time, the mass density of the Universe is thought to approach the → Planck density.

Planck; → time.

Planck units
  یکاهای ِ پلانک   
yekâhâ-ye Planck (#)

Fr.: unités de Planck   

A set of → natural units in which the normalized units are: the gravitational constant, Planck's constant, the speed of light, the Coulomb constant, and Boltzmann's constant.

Planck; → unit.

Planck's blackbody formula
  دیسول ِ سیه‌جسم ِ پلانک   
disul-e siyah jesm-e Planck

Fr.: formule du corps noir de Planck   

A formula that determines the distribution of intensity of radiation that prevails under conditions of thermal equilibrium at a temperature T: Bv = (2hν3 / c2)[exp(hν / kT) - 1]-1 where h is Planck's constant and ν is the frequency.

Planck; → blackbody; → formula.

Planck's constant
  پایای ِ پلانک   
pâyâ-ye Planck (#)

Fr.: constante de Planck   

Planck constant.

Planck; → constant.

Planck's radiation law
  قانون ِ تابش ِ پلانک   
qânun-e tâbeš-e Planck

Fr.: loi du rayonnement de Planck   

An equation that expresses the energy radiated per unit area per unit time per unit wavelength range by a blackbody as a function of temperature. It is expressed by → Planck's blackbody formula.

Planck; → radiation; → law.

  ۱) هامُن؛ ۲) تخت   
1) hâmon (#); 2) taxt (#)

Fr.: plan   

1) (n.) a flat or level surface.
2) (adj.) Of or pertaining to planes or plane figures.

1) From L. plantum "flat surface," noun use of adj. planus "flat, level, plain."
2) From L. planus, as above.

1) Hâmon, variant of hâmun "plain, level ground;" Mid.Pers. hâmôn "level, flat;" Proto-Iranian *hāma-van-, from *hāma- "same, equally, even; together, with" (Mod.Pers./Mid.Pers. ham-; O.Pers./Av. ham-; cf. Skt. sam-; also O.Pers./Av. hama- "one and the same;" Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + *-van- suffix.
2) Taxt "flat;" Mid.Pers. taxtag "tablet, plank, (chess)board."

plane figure
  شکل ِ هامن، ~ تخت   
šekl-e hâmon, ~ taxt

Fr.: figure plane   

A two-dimensional geometric figure. The points of the figure lie entirely in a plane.

plane; → figure.

plane mirror
  آینه‌ی ِ تخت   
âyene-ye taxt (#)

Fr.: miroir plan   

A mirror whose reflective surface is neither concave nor convex.

plane; → mirror.

plane of polarization
  هامن ِ قطبش   
hâmon-e qotbeš

Fr.: plan de polarisation   

In a → linearly polarized light, a plane perpendicular to the → plane of vibration and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the magnetic vector (H) of the electromagnetic light wave.

plane; → polarization.

plane of rotation
  هامن ِ چرخش   
hâmon-e carxeš

Fr.: plan de rotation   

For a rotating object, the plane → perpendicular to the → rotation axis.

plane; → rotation.

plane of the sky
  هامن ِ آسمان   
hâmon-e âsmân

Fr.: plan du ciel   

An imaginary plane that is perpendicular to the → line of sight.

plane; → sky.

plane of vibration
  هامن ِ شیوش   
hâmon-e šiveš

Fr.: plan de vibration   

In a → linearly polarized light, a plane perpendicular to the → plane of polarization and containing the direction of propagation of light. It is also the plane containing the direction of propagation and the electric vector (E) of the electromagnetic light wave.

plane; → polarization.

plane polarization
  قطبش ِ هامنی   
qotbeš-e hâmoni

Fr.: polarisation plane   

Same as → linear polarization.

plane; → polarization.

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