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Parallax   Listen
noun
Parallax  n.  
1.
The apparent displacement, or difference of position, of an object, as seen from two different stations, or points of view.
2.
(Astron.) The apparent difference in position of a body (as the sun, or a star) as seen from some point on the earth's surface, and as seen from some other conventional point, as the earth's center or the sun.
3.
(Astron.) The annual parallax. See annual parallax, below.
Annual parallax, the greatest value of the heliocentric parallax, or the greatest annual apparent change of place of a body as seen from the earth and sun; it is equivalent to the parallax of an astronomical object which would be observed by taking observations of the object at two different points one astronomical unit (the distance of the Earth from the sun) apart, if the line joining the two observing points is perpendicular to the direction to the observed object; as, the annual parallax of a fixed star. The distance of an astronomical object from the Earth is inversely proportional to the annual parallax. A star which has an annual parallax of one second of an arc is considered to be one parsec (3.26 light years) distant from the earth; a star with an annual parallax of one-hundredth second of an arc is 326 light years distant. See parsec in the vocabulary, and stellar parallax, below.
Binocular parallax, the apparent difference in position of an object as seen separately by one eye, and then by the other, the head remaining unmoved.
Diurnal parallax or Geocentric parallax, the parallax of a body with reference to the earth's center. This is the kind of parallax that is generally understood when the term is used without qualification.
Heliocentric parallax, the parallax of a body with reference to the sun, or the angle subtended at the body by lines drawn from it to the earth and sun; as, the heliocentric parallax of a planet.
Horizontal parallax, the geocentric parallx of a heavenly body when in the horizon, or the angle subtended at the body by the earth's radius.
Optical parallax, the apparent displacement in position undergone by an object when viewed by either eye singly.
Parallax of the cross wires (of an optical instrument), their apparent displacement when the eye changes its position, caused by their not being exactly in the focus of the object glass.
Stellar parallax, the annual parallax of a fixed star.






Collaborative International Dictionary of English 0.48








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"Parallax" Quotes from Famous Books



... that I can get a parallax to any of the fixed stars in a moment, with only the breadth of my nose for the base," answered Heinrich, responding at once to the fun, and careless of the personal defect insinuated. "She was near enough for even me to ...
— The Portent & Other Stories • George MacDonald

... parallax, or the differing views of the same solid object obtained by the two eyes. Hold a small, three-dimensional object a foot in front of the face, and notice carefully the view of it obtained by each eye separately. A pencil, pointing towards the face, gives very different views. ...
— Psychology - A Study Of Mental Life • Robert S. Woodworth

... A star-picture along the ecliptic. An hour's run on interplanetary drive—no overdrive field in use. Another picture. The two prints had only to be compared with a blinker for planets to stick out like sore thumbs, as contrasted with stars that showed no parallax. Sirene I—the innermost planet—was plainly close to a transit. II was away on the far side of its orbit. III was also on the far side. IV was in quadrature. There was the usual gap where V should have been. VI—it didn't ...
— A Matter of Importance • William Fitzgerald Jenkins

... address, I think, will tax My intellectual organ till it cracks; The Association British isn't wanted to be skittish, Wear the motley, nor to run a race in sacks; But 'twas getting awkward rather when my youngest asked his father What the President implied by parallax. ...
— Punch, Or The London Charivari, Vol. 101, August 29, 1891 • Various

... a lens-shaped, flattened, and everywhere detached stratum, whose major axis is estimated at seven or eight hundred, and its minor axis at a hundred and fifty times, the distance of Sirius. If we assume that the parallax of Sirius does not exceed that accurately determined for the brightest stars in Centaur (0.9128 sec.), it will follow that light traverses one distance of Sirius in three years, while nine years and a quarter are required ...
— The World's Greatest Books - Volume 15 - Science • Various

... of Saturn's ring, having perceived that instead of one there are two concentric rings separated by a dark space. He also discovered four of the planet's satellites—viz. Japetus, Rhea, Dione, and Tethys. He made a near approximation to the solar parallax by means of researches on the parallax of Mars, and investigated some irregularities of the Moon's motion. Cassini discovered the belts of Jupiter, and also the Zodiacal Light, and established the coincidence of the nodes of ...
— The Astronomy of Milton's 'Paradise Lost' • Thomas Orchard

... that room, you know, is half-way between the ground-floor and first floor. Still, sound does travel so! We must betake ourselves to measurement, I fear.—But another thing came into my head last night which may serve to give us a sort of parallax. You said you heard the music in your own room: would you let me look about in it a little? something might suggest itself!—Is it the room I saw you ...
— Donal Grant • George MacDonald

... separately. If you hold up a finger and look at it, with each eye separately, you will see that the finger is projected by each eye on to a different part of the background; the angle which the lines of sight, from each eye, make when they meet at the object, is called the angle of parallax, and the further the object is away the smaller that angle becomes; it is, in fact, the angle subtended, at the object, by the distance between the two eyes. As the object is brought nearer the eyes have ...
— Science and the Infinite - or Through a Window in the Blank Wall • Sydney T. Klein

... where it will frequently recur, and always in connection with the measurement of celestial distances. "Do not let us fear," wrote Lalande in his Astronomie des Dames, "do not let us fear to use the term parallax, despite its scientific aspect; it is convenient, and this term explains a very simple and ...
— Astronomy for Amateurs • Camille Flammarion

... the sun's apogee as well as its mean motion. Their calculations on the eccentricity of the moon prove that they had a rectilinear trigonometry and tables of chords. They had an approximate knowledge of parallax; they could calculate eclipses of the moon, and use them for the correction of their lunar tables. They understood spherical trigonometry, and determined the motions of the sun and moon, involving an accurate definition ...
— Beacon Lights of History, Volume III • John Lord

... safely presume to be in proportion to their actual size and the distance at which they are placed from us. Attempts have been made to ascertain the distance of some of the stars by calculations founded on parallax, it being previously understood that, if a parallax of so much as one second, or the 3600th of a degree, could be ascertained in any one instance, the distance might be assumed in that instance as not less than 19,200 millions of miles! In the case of the most brilliant ...
— Vestiges of the Natural History of Creation • Robert Chambers

... a moment too soon, for, as if the previous proofs had not been sufficient, each of the motions of the earth was now absolutely demonstrated anew, so as to be recognised by the ordinary observer. The parallax of fixed stars, shown by Bessel as well as other noted astronomers in 1838, clinched forever the doctrine of the revolution of the earth around the sun, and in 1851 the great experiment of Foucault with the pendulum showed to the human eye the earth in motion around its own axis. To make ...
— History of the Warfare of Science with Theology in Christendom • Andrew Dickson White



Words linked to "Parallax" :   horizontal parallax, solar parallax, annual parallax, diurnal parallax



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