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

A group of seven stars, an → asterism, lying inside the Northern constellation → Ursa Major. They are: → Dubhe, → Merak, → Phad, → Megrez, → Alioth, → Mizar, and → Alkaid. The group is also known as the Plough in Great Britain.

→ big; dipper a popular U.S. name for the asterism known in Britain as The Plough or Charles' Wain, from dip O.E. dyppan "immerse," from P.Gmc. *dupjanan.

Haft barâdarân "the seven brothers," from haft "seven" (Mid.Pers. haft, Av. hapta, cf. Skt. sapta, Gk. hepta, L. septem, P.Gmc. *sebun, Du. zeven, O.H.G. sibun, Ger. sieben, E. seven; PIE *septm) + barâdarân, plural of barâdar "brother" (Mid.Pers. brad, bardar, O.Pers./Av. brātar-, cf. Skt. bhrátar-, Gk. phrater, L. frater, P.Gmc. *brothar; PIE base *bhrater- "brother").
Haftowrang, Mid.Pers. haptôiring, from Av. haptôiringa- "with seven marks," from hapto- "seven,"as above, + iringa- "mark," cf. Skt. linga- "mark, token, sign."
Camcé "a spoon, ladle; a wooden bowl or cup;" bozorg "big, large."

1) Navigation: The angular difference between the visible horizon and the true horizon. Same as → dip of the horizon.
2) Geodesy: The angle between the horizontal and the lines of force of the Earth's magnetic field at any point. → magnetic dip.
3) Aviation: The angle between the true and apparent horizon, which depends on flight height, the Earth's curvature, and refraction.

O.E. dyppan "to immerse," cognate with Ger. taufen "to baptize," and with → deep.

Našib, → depression.

The angular difference between the → visible horizon and the → true horizon. Same as → dip of the horizon.

→ dip; → angle.

The angle created by the observer's line of sight to the → apparent horizon and t he → true horizon. Neglecting the → atmospheric refraction, dip of the horizon can be expressed by θ (radians) = (2h/R)^1/2, where h is the observer's height and R the Earth's radius. An an example, for a height of 1.5m above the sea, and R = 6.4 x 10⁶ m, the dip angle is about 0.00068 radians, or 0.039 degrees, about 2.3 minutes of arc, quite appreciable by the eye. See also → distance to the horizon. Same as → dip angle.

→ dip; → horizon.

The brightest star in the constellation → Cetus; a → red supergiant (K0 III) of visual magnitude 2.04.

Diphda, from Ar. zafda' (ضفدع) "frog." It is also designated as Deneb Kaitos, from zanab al-qaytusذنب القیطس "tail of Cetus."

Mid.Pers. wazaγ, vak; Av. vazaγa- "frog," → tadpole orbit.

Phonetics: A → vowel sound produced by a blended sequence of two separate vowels in a single syllable, where the sound begins as one vowel and moves toward another (as in loud, light, and lair).

From M.Fr. diphthongue, from L.L. diphthongus, from Gk. diphthongos "having two sounds," from → di- "double" + phthongos "sound, voice."

Dovâké, from do "two, → di-" + vâké, vâk, → voice.

A pathological condition of vision in which a single object appears double because the eyes are not focusing properly. Same as → double vision.

From L. diplo- "double, in pairs," from Gk., combining form of diplos "twofold" + -opia, from Gk. -opia, from ops "eye."

Dobini, from do→ two + bini "vision, seeing," from bin "to see; seer" (present stem of didan; Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see").

Of or relating to a → dipole.

→ dipole; → -ar.

A → magnetic field produced by a system possessing a net magnetic → dipole moment.

→ dipolar; → magnetic; → field.

1) A combination of two electrically or magnetically charged particles of opposite signs, which are separated by a very small distance.
2) Chemistry: A molecule containing both positively and negatively charged groups.

→ di- "two, twice, double," + → pole.

A form of anistropy in the temperature of the → cosmic microwave background radiation, appearing as one hot pole and one cold pole, caused by our motion with respect to the cosmic background radiation. The temperature variations, amounting to 1 part in 1000, yield a velocity of about 600 km/sec for our Galaxy with respect to the background. → cosmic microwave background anisotropy.

→ dipole; → anisotropy.

One of the simplest kinds of antenna which is connected at the center to a radio-frequency feed line for transmitting or receiving radio frequency energy. It differs from the dish antenna in that it consists of many separate antennas that collect energy by feeding all their weak individual signals into one common receiving set.

→ dipole; → antenna.

1) The product of the strength of either of the charges in an → electric dipole and the distance separating the two charges. It is expressed in → coulomb meters. Dipole moment is a → vector quantity. Its direction is defined as toward the positive charge. In chemistry dipole moment is a quantitative measure of polarity in a molecule; the unit is the → debye.
2) The product of the strength of either of the poles in a → magnetic dipole and the distance separating the two poles. Dipole moment is a vector quantity. Its direction is defined as toward the magnetic north pole.

→ dipole; → moment.

The electromagnetic radiation produced by an oscillating → electric dipole or → magnetic dipole.

→ dipole; → radiation.

An → isotope of → helium that consists of two → protons, without any → neutrons. It is extremely → unstable.

→ di-; → proton.

1) A type of → charge distribution consisting of two charges, a positive and a negative charge of the same magnitude separated by a distance s, which is small compared to the distance r to the point P at which the → electric potential is V and the → electric field intensity is E.The potential falls as the square of the distance (1/r²) and the electric field intensity decreases as the cube of the distance (1/r³).
2) A simple → antenna consisting of a pair of oppositely charged → conductors capable of radiating an → electromagnetic wave in response to the movement of an electric charge from one conductor to the other.

→ electric; → dipole.

An asterism in the constellation → Ursa Minor. This group of stars ends at → Polaris, the pole star of the Northern Hemisphere.

Little, from M.E., O.E. lytel, from W.Gmc. *lutila- (cf. Du. luttel, O.H.G. luzzil, Ger. lützel, Goth. leitils), from PIE *leud- "small;" dipper, from dip, O.E. dyppan "immerse," from P.Gmc. *dupjanan.

Haft xâharân "the seven sisters," from haft "seven" (Mid.Pers. haft; Av. hapta; cf. Skt. sapta; Gk. hepta; L. septem; P.Gmc. *sebun; Du. zeven; O.H.G. sibun; Ger. sieben; E. seven; PIE *septm) + xâharân plural of xâhar "sister;" Mid.Pers. xwâhar "sister;" Av. x^vanhar- "sister;" cf. Skt. svásar- "sister;" Sogdian xwār; Gk. eor; L. soror (Fr. soeur); Arm. k'oyr; O.C.S., Rus. sestra; Lith. sesuo; O.Ir. siur; Welsh chwaer; M.Du. suster; Du. zuster; O.H.G. swester; Goth. swistar; Ger. Schwester; Swed. sister; Dan. søster; O.E. sweostor, swuster; E. sister.
Camcé "a spoon, ladle; a wooden bowl or cup;" kucak "small" (Mid.Pers. kucak "small"), related to kutâh "short, small, little," kudak "child, infant," kutulé, → dwarf, Mid.Pers. kôtâh "low," kôtak "small, young; baby;" Av. kutaka- "little, small").

In terrestrial magnetism, the angle that a → magnetic needle makes with the horizontal plane at any specific location. The angle of magnetic dip at the → magnetic poles of Earth is 90°. Also called → inclination and → dip.

→ magnetic; → dip.

A system that generates a → magnetic field in which the field is considered to result from two opposite poles, as in the north and south poles of a magnet, much as an → electric field originates from a positive and a negative charge in an → electric dipole. A loop carrying an electric current also acts as a magnetic dipole. Magnetic dipoles experience a torque in the presence of magnetic fields. → dipole moment; → magnetic moment.

→ magnetic; → dipole.

Same as → magnetic moment.

→ magnetic; → dipole; → moment.