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

A technique for making three-dimensional images by recording → interference patterns from a split → laser beam on a medium such as photographic film. One of the → coherent beams irradiates the object, the second beam illuminates a recording medium. The two beams produce an interference pattern, called → hologram, on the film. The hologram contains information on both → phase and → amplitude of the object. However, this information is in a coded form, and the image must be reconstructed. When the object is removed and the hologram is illuminated by the laser from the original direction, a 3-dimensional image of the object appears where the object was originally, as if it were not removed. The visible object seems so real that the observer can detect → parallax by changing the position of one's head.

From → holo- "whole" + → -graphy. By using the term holography, Dennis Gabor (1900-1979), the Hungarian-British electrical engineer and inventor, wanted to stress that the technique records complete information about a wave, both about its amplitude and its phase, in contrast to the usual photography in which only the distribution of the amplitude is recorded.

A material system in which the → constraints can be expressed in the form of an equation relating the coordinates.

From Gk. → holo- "whole" + -nomic, related to nomos "law, managing, governing, custom," → -nomy; → system.

1) Respect or reverence paid or rendered.
2) Something done or given in acknowledgment or consideration of the worth of another (Dictionary.com).

M.E. (h)omage, from O.Fr. homage "allegiance or respect for one's feudal lord," from homme "man," → human, + -age.

Bozordgâšt, literally "considered to be great," from bozorg "large, magnificent, great," → magnify, + dâšt, dâštan "to maintain, consider, possess, keep in mind, hold, have," → property.

A combining form meaning "same" used in the formation of compound words. Also, especially before a vowel, hom-.

Homo-, from Gk. homos "one and the same," also "belonging to two or more jointly," from PIE *somos; cf. Pers. ham-, as below; Lith. similis "like," Goth. sama "the same," samana "together."

Ham- "together, with; same, equally, even," Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, 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-.

Concentric → spheres of Eudoxus.

→ homo-; → center; → -ic; → sphere.

Of, or pertaining to the process of combining two waves, such as → electromagnetic waves, of the same → frequency. See also: → heterodyne.

Homodyne, from → homo- + -dyne, from Gk. dynamics→ dynamics.

State or quality of having a uniform appearance or composition, being homogeneous

→ homogeneous + → -ity.

1) Of uniform composition or having a common property throughout.
2) Math.: Of the same kind so as to be commensurable. Of the same degree or dimension. → anisotropic homogeneous cosmological model, → homogeneous fluid, → homogeneous linear differential equation, → homogeneous Universe, → homogeneous turbulence, → inhomogeneous, → nonhomogeneous, → nonhomogeneous linear differential equation.

Homogeneous, from M.L. homogeneus, from Gk. homogenes "of the same kind," from homos "same," → homo-, + genos "race, kind," gonos "birth, offspring," from PIE base *gen-/*gon-/*gn- "to produce, beget, be born," cf. Av. zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born," zana- "race" (in sruuô.zana- "belonging to the race of the horned ones"), O.Pers. zana- "tribe" (in paru-zana- "consisting of many tribes"), Skt. janati "begets, bears," jana- "creature, human being, race, tribe, people;" L. genus "race, stock, kind," gignere "to beget."

Hamgen "of the same kind, like each other; friend, partner," from ham-, → homo-, + gen "kind," O.Pers./Av. zana- "race; tribe," cognate with L. genus, as above). Alternatively, gen may be a variant of Mid./Mod.Pers. gôn/gun "kind, type; manner; color, skin color," from Av. gaona- "hair, hair color, color."

A fluid with uniform properties throughout, but meteorologists sometimes designate as homogeneous a fluid with constant density.

→ homogeneous, → fluid.

A → linear differential equation if the right-hand member is zero, Q(x) = 0, on interval I.

→ homogeneous; → linear; → differential; → equation.

→ Turbulence in which spatial derivatives of all mean turbulent quantities are negligible.

→ homogeneous, → turbulence.

A model Universe which is homogeneous and → isotropic on large scales. It is modeled by a → Robertson-Walker cosmology. A homogeneous Universe is filled with a constant density and negligible pressure. Any small spatial region is characteristic for the whole Universe.

→ homogeneous; → Universe.

A → mapping between two mathematical → objects that preserves the object structure. A general → morphism.

→ homo-; → morphism.

A molecule that is composed of only one type of → chemical element, e.g. the → molecular hydrogen and → ozone.

→ homo-; → nuclear; → molecule.

The altitude at which → molecular diffusion replaces → eddy diffusion as the dominant vertical transport mechanism. Light gases separate out from heavier ones above this altitude. The flux of hydrogen through the homopause is limited by diffusion.

→ homo-; + pause "break, cessation, stop," from M.Fr. pause, from L. pausa "a halt, stop, cessation," from Gk. pausis "stopping, ceasing," from pauein "to stop, to cause to cease."

Hamgen, → homogeneous, + marz "frontier, border, boundary," → frontier. frontier.

Based on chemical composition, the Earth atmosphere is divided into two broad layers: the homosphere and the → heterosphere. The homosphere extends from the surface of the Earth up to the height of about 90 km. It is characterized by an almost homogeneous composition of nitrogen (78%), oxygen (21%), argon (10%), carbon dioxide as well as traces of constituents like dust particles, → aerosols and cloud droplets.

→ homo-; → shere.

A nebula of gas and dust (about 17" x 12" in size), which surrounds the massive star Eta Carinae and lies about 7500 light-years away. The surrounding material was ejected by the massive star in 1843 during its violent eruption, and is now expanding at about 500 km/sec.

Homunculus, "a diminutive human being; little man" (since the nebula resembled a small human to early observers), from L. homin-, homun-, homo "eartly being," humus "the earth" (cf. Pers. zamin "earth, ground," Mid.Pers. zamig "earth;" Av. zam- "the earth;" Skt. ksam; Gk. khthôn, khamai "on the ground;" PIE root *dh(e)ghom "earth") + → -ula, -ule; → nebula.

Miq, → nebula; âdamak "little man."

1) A curved or bent piece of metal or other hard material for catching, holding, or hanging something.
2) Something curved or bent like a hook.

M.E. hoke, O.E. hoc "hook, angle;" cf. M.Du. hoek, Du. haak, Ger. Haken "hook."

Qollab "a hook, a hooked device," probably ultimately from Proto-Ir. gart- "to turn;" cf. Pers. gard-, gardidan, gaštan "to turn, to wind;" cognate with dialectal qellidan "to roll."

The law stating that if a body is deformed the → strain produced is directly proportional to the applied → stress. If the elastic limit is not exceeded, the material returns to its original shape and size on the removal of the stress. Hooke's law forms the basis of the theory of → elasticity.
More specifically, within certain limits, the force required to stretch an elastic object such as a metal spring is directly proportional to the extension of the spring. It is commonly written: F = -kx, where F is the force, x is the length of extension/compression and k is a constant of proportionality known as the spring constant.

Named after Robert Hooke (1635-1703), British scientist who described the relationship in 1676; → law.

1) To move by a quick springy leap or in a series of leaps. (Of a person) Move by jumping on one foot. (Of a bird or other animal) move by jumping with two or all feet at once.
2) An act of hopping; short leap.

M.E. hoppen; O.E. hoppian; cognate with Ger. hopfen, O.N. hoppa.

Kopidan, from kop; cf. (Bašâgardi) kup, (Lârestâni) komp, (Bardesiri) gopak, (Sistâni) job, (Kermâni) pok, pokidan "jump, leap."