Fr.: vitesse de lecture
In computing and data processing, the number of words, characters, fields, etc. sensed by an input sensing device per unit of time.
Reading, verbal noun of read, from M.E. reden, O.E. rædan, redan "to counsel, read;" cf. Du. raden, Ger. raten "to advise, counsel, guess;" akin to Skt. rādh- "to succeed, accomplish;" Gk. arithmos "number amount;" L. ratio; Pers. rây, râ "because of, for the sake of;" → reason; → rate.
Nerx, → rate; xâneš verbal noun of xândan "to read; to sing; to call;" Mid.Pers. xwân- "to resound; to call;" Av. xvan- "to sound," Proto-Iranian *huan- "to call;" cf. Skt. svan-, sváranti "to sound, make a sound, sing;" L. sonus "sound," sonare "to sound;" O.E. swinn "music, song," PIE base *suen- "to sound" (Cheung 2007).
Fr.: bruit de lecture
The noise added in the process of reading a detector such as a CCD.
Fr.: rayonnement de recombinaison
Radiation produced when a free electron in a plasma is captured by an ionized atom.
reductio ad absurdum
bâzhâzeš bé yâvé
Fr.: raisonnement par l'absurde
Logic, Math.: A method of → reasoning in which one assumes some statement to be → true and from that → assumption proceeds to deduce a logical → absurdity and hence to a conclusion that the original assumption must have been → false.
pasrow (#), pasraft (#)
Moving backward; having a backward motion or direction. → retrograde motion.
M.E., from L. retrogradus "going backward," from retrogradi "move backward," from retro- "backward" + gradi "to go, step."
Pasrow, pasraft, from pas- "back, behind," → back, + row, raft present and past stems of raftan "to go, walk;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").
Fr.: mouvement rétrograde
The orbital motion or rotation of a solar system body in a clockwise direction (East to West) when viewed from the north pole of the ecliptic. It is a motion opposed to the → direct motion of the great majority of solar system bodies.
Fr.: objet rétrograde
An object which has a retrograde orbit around its primary.
Fr.: orbite rétrograde
An orbit with an inclination between 90° and 270° such as those of some comets and small asteroids orbiting the Sun.
Fr.: cascade de Richarson
Same as → energy cascade
Named after L. F. Richardson (1922), Weather Prediction by Numerical Process (Cambridge Univ. Press); → cascade.
Fr.: élargissement rotationnel
The spectral line broadening caused by stellar rotation. Light from two rims of the star will be Doppler shifted in opposite directions, resulting in a line broadening effect. The line broadening depends on the inclination of the star's pole to the line of sight. The derived value is a function of ve. sini, where ve is the rotational velocity at the equator and i is the inclination, which is not always known. The fractional width (Δλ/λ) is of the order of 10-3 for B stars.
S Doradus star
setâre-ye S Zarrin-mâhi
Fr.: étoiles S Doradus
A type of massive, → blue supergiant, → variable star, also known as a → Hubble-Sandage variable or a → Luminous Blue Variable (LBV). S Doradus stars are the most luminous stars in the Galaxy and are easily identified in other nearby galaxies. They are named after the prototype, S Doradus, in the → Large Magellanic Cloud.
Sadalmelik (α Aquarii)
A supergiant star of type G2 Ib situated in the constellation → Aquarius. At a distance of 750 light-years, it has a luminosity 3000 times that of the Sun, and a diameter about 60 times the solar diameter. Variant designations: Sadalmelek; Sadlamulk; El Melik; Saad el Melik.
From Ar. Sa'd al-Malik (
Sadr (γ Cygni)
From Ar. as-sadr (
Fr.: rayon de Schwarzschild
The critical radius at which a massive body becomes a → black hole, i.e., at which light is unable to escape to infinity: Rs = 2GM / c2, where G is the → gravitational constant, M is the mass, and c the → speed of light. The fomula can be approximated to Rs≅ 3 x (M/Msun), in km. Therefore, the Schwarzschild radius for Sun is about 3 km and for Earth about 1 cm.
gerde-ye xod-pardé, disk-e ~
Fr.: disque auto-écranté
A model of → accretion disk around a → pre-main sequence star or a → protostar in which the outer parts of the disk are geometrically flat, in contrast to a → flared disk. Inward of a certain radius (0.5-1 AU from the star) the dust in the disk evaporates. Because the dust is the main source of opacity and the gas in the disk is usually optically thin, the irradiation burns a hole in the disk. Moreover, the inner rim puffs up, similarly to the case of flared disks. The difference lies in the outer parts. The inner rim casts its shadow over the disk all the way out. Since the disk thickness is almost constant, no photons can reach the surface of the disk and the outer parts of the disk remain shadowed by the inner rim and the midplane temperatures decrease accordingly. This model explains the observed → spectral energy distribution of some pre-main sequence stars, such as HD 101412. It also accounts for the observed weak → far infrared→ excess, weak or no → PAH emission, and weak or no [O I] emission.
1) The comparative darkness caused by the interception or screening of rays of
light from an object, place, or area.
M.E. schade; O.E. scead "partial darkness; shelter," → shadow.
Sivân, from Kurd. sayvân "shadow, shade," variants si, sâ, sâyé, → shadow.
A dark patch formed by a body which obstructs rays of light.
M.E. sch(e)adew(e), schadow, shadw(e), O.E. sceadwe, sceaduwe, sceadu "shade, shadow, darkness;" cf. O.S. skado, M.Du. scade, Du. schaduw, O.H.G. scato, Ger. Schatten, Goth. skadus; from PIE base *skot- "dark, shade."
Sâyé "shadow," from Mid.Pers. sâyak "shadow;" Av. a-saya- "throwing no shadow;" Skt. chāya- "shadow;" Gk. skia "shade;" Rus. sijat' "to shine;" M.H.G. schinen, O.H.G. skinan, Ger. Schein "glow, shine;" PIE base *skai- "bright."
navârhâ-ye sâyé, bândhâ-ye ~
Fr.: ombres volantes
Faint wavy lines of alternating light and dark that sometimes can be seen on flat, light-colored surfaces just before and just after a total solar eclipse. The phenomenon results from sunlight distortion by irregularities in the Earth's atmosphere.
Fr.: cône d'ombre
A cone-shaped shadow cast by Earth or the Moon pointing away from the Sun. The dark inner portion of the shadow cone is called the → umbra. The lighter outer portion of the shadow is called the → penumbra. Its extension is called the → antumbra.
šâné (#), ketf (#)
→ shoulder; blade, M.E.; O.E. blæd "blade of grass;" cognate with Du. blad, Ger. Blatt.
Šâné, ketf, → scapula.