An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 72 Search : light
space flight
  پرواز ِ فضایی   
parvâz-e fazâyi

Fr.: vol spatial   

A travel outside the Earth by manned or unmanned vehicle requiring space technology.

space; → flight.

speed of light
  تندی ِ نور   
tondi-ye nur

Fr.: vitesse de la lumière   

Same as → velocity of light.

speed; → light.

âftâb (#)

Fr.: lumière solaire   

The light of the Sun.

sun; → light.

Âftâb, "sun(shine);" Mid.Pers. âftâp; Proto-Iranian *abi-tap-, from *abi- "to, upon, against" (O.Pers./Av. abiy-/aiwi- "to, upon, against;" Skt. abhi-, Gk. amphi-) + *tap- "to shine" (Mod.Pers. tâbidan, variants tâftban "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm").

supernova light curve
  خم ِ نور ِ اَبَرنووا، ~ ~ اَبَر-نو‌اختر   
xam-e nur-e abarnovâ, ~ ~ abar-now-axtar

Fr.: courbe de lumière de supernova   

The graph of luminosity as a function of time after a → supernova explosion. The → light curve goes up rapidly to a → peak luminosity, then decays away slowly over time, with different rates, depending on the → supernova type. The temporal evolution of a supernova's luminosity contains important information on the physical processes driving the explosion. The observed → bolometric light curves provide a measure of the total output of converted radiation of → Type Ia supernovae, and hence serve as a crucial link to theoretical models of the explosion and evolution.

supernova; → light; → curve.

tangentially polarized light
  نور ِ قطبیده‌ی ِ سایانی   
nur-e qotbide-ye sâyâni

Fr.: lumière polarisée tangentiellement   

The → linearly polarized light that vibrates perpendicularly to an imaginary line joining the source to the point of observation.

Tangentially, adverb of → tangential; → polarized; → light.

tired light
  نور ِ خسته   
nur-e xasté

Fr.: fatigue de la lumière   

The hypothesis that photons from distant objects lose energy during their intergalactic journey to us, thereby increasing in wavelength and becoming redshifted. This would provide an alternative to the → Big Bang model in accounting for the → redshifts of distant galaxies. However, there is no evidence for any such tired-light effect. First discussed by F. Zwicky (1929, Proceedings of the National Academy of Sciences, 15, 773).

tired; → light.

nimtâb (#)

Fr.: crépuscule   

The diffused light from the sky when the Sun is below the → horizon, either from daybreak to → sunrise or, more commonly, from → sunset to → dusk or nightfall. There are three types of twilight: → astronomical twilight, → nautical twilight, and → civil twilight. They are divided on the basis of the → solar depression angle.

M.E., cognate with Du. tweelicht, Ger. zwielicht, from twi- a combining form meaning "two, twice," but it appears to refer to "half" light, rather than the fact that twilight occurs twice a day + → light.

Nimtâb, from nim, nimé, → half, + tâb "light," present stem of tâbidan "to shine," → luminosity.

unpolarized light
  نور ِ ناقطبیده   
nur-e nâqotbidé (#)

Fr.: lumière non polarisée   

A light whose electric vector of vibration is randomly oriented. Light is an → electromagnetic wave possessing an electric vector and an associated orthogonal magnetic vector. Both vectors are → transverse to the axis of propagation. In unpolarized light the electric and magnetic vibrations occur in all possible planes. Ordinary light emitted by the Sun, by a living room lamp, or by a candle flame is unpolarized light. → polarization.

un-; → polarized light.

velocity of light
  تندی ِ نور، تندای ِ ~   
tondi-ye nur, tondâ-ye ~

Fr.: vitesse de la lumière   

A → physical constant which represents the ultimate speed limit for anything moving through space, according to the theory of → special relativity. It is the speed of propagation of → electromagnetic waves in a vacuum, equal to 299,792.458 km/s (nearly 3 x 108 m/s). The velocity of light appears as the connecting link between mass and energy in the → mass-energy relation. Usually denoted by c, from L. celeritas "swiftness," from celer "swift," → acceleration.

velocity; → speed; → light.

visible light
  نور ِ دیار، ~ دیدنی   
nur-e diyâr, ~ didani

Fr.: lumière visible   

The portion of the → electromagnetic radiation that can be seen by the human → eye. The → wavelengths extend from about 400 nm (violet) to 750 nm (red). The wavelengths of various colors of the visible spectrum are as follows: → violet: 390-455 nm; → blue: 455-492 nm; → green: 492-577; → yellow: 577-597; → orange: 597-622; → red: 622-780 nm.

visible; → light.

wave theory of light
  نگره‌ی ِ موجی ِ نور   
negare-ye mowji-ye nur

Fr.: théorie ondulatoire de la lumière   

The theory that describes light as waves that spread out from the source that generates the light. It contradicts the → corpuscular theory of light proposed by Newton (1704). The idea of the wave nature of light was first put forward by Robert Hooke (1660). The wave theory was originally stated by Huygens (1690), who showed reflection and refraction could be explained by this theory. It was supported by → Young's experiment (1802) and established by the work of Fresnel (1814-1815). The wave theory received its most important support from Maxwell's → electromagnetic theory. See also → Huygens-Fresnel principle.

wave; → theory; → light.

zodiacal light
  نور ِ برجگانی   
nur-e borjgâni

Fr.: lumière zodiacale   

A cone-shaped faint glow along the → ecliptic, visible to the naked eye in the west after sunset or in the east before sunrise. Zodiacal light results from sunlight reflected by interplanetary dust concentrated in the plane of the ecliptic.

zodiacal; → light.

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