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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



... more luminous guide; and if with an ardent love for truth he has sought her in vain through the ways of this life, he will but turn with the more hope to that better world where all is simple, true and everlasting: for there is no parallax at the zenith;—it is only near our troubled horizon that objects deceive us into vague ...
— The Complete Poems of Sir Thomas Moore • Thomas Moore et al

... differed in an argument on the parallax of a lyrae—the one maintaining that it was three seconds, and the other that it was only two seconds. On being told of this discussion, and that the astronomers parted without arriving at an agreement, Plunket quietly remarked: "It must be a very serious quarrel indeed, when ...
— Law and Laughter • George Alexander Morton

... successively smaller sizes to their greater and greater degrees of remoteness, what becomes of the inferences respecting the dimensions of our sidereal system and the distances of nebulae? If, as has lately been shown, the almost invisible star 61 Cygni has a greater parallax than [Greek: a] Cygni, though, according to an estimate based on Sir W. Herschel's assumption, it should be about twelve times more distant—if, as it turns out, there exist telescopic stars which are nearer to us than Sirius; of what worth ...
— Essays: Scientific, Political, & Speculative, Vol. I • Herbert Spencer

... all original action exerts is explained when we inquire the reason of self-trust. Who is the Trustee? What is the aboriginal Self, on which a universal reliance may be grounded? What is the nature and power of that science-baffling star, without parallax, without calculable elements, which shoots a ray of beauty even into trivial and impure actions, if the least mark of independence appear? The inquiry leads us to that source, at once the essence of genius, the essence of virtue, and the essence of life, which we call Spontaneity ...
— English Prose - A Series of Related Essays for the Discussion and Practice • Frederick William Roe (edit. and select.)

... flight. There is, to be sure, an arcanum of prosodic theory which is the province of specialists. It has its place in the scheme of things; but it is no more necessary for the genuine enjoyment of Milton (or the 'moderns') than a knowledge of the formulae for calculating the parallax of Alpha Leonis is necessary for enjoying the pillared firmament. We must then compromise with a system which reveals the existence of all the phenomena and tries to suggest their ...
— The Principles of English Versification • Paull Franklin Baum

... sense, the objects and the points of view are each indifferent to the rest; but in life the points of views are centres of action that have had something to do with the making of the things looked at. If we could calculate the moral parallax arising from these causes, we should see, by the mere aid of the intellect, how unjust we often are in our complaints of ingratitude, inconstancy, and neglect. But without these nice calculations, such errors of view ...
— Friends in Council (First Series) • Sir Arthur Helps



Words linked to "Parallax" :   stellar parallax, geocentric parallax, horizontal parallax, optical phenomenon, solar parallax, heliocentric parallax



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