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Parallax   /pˈɛrəlˌæks/   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



... processes. We see the rock strata bent and folded, we see the whole mountain-chains flexed and shortened by the flexure; but had we been present, we should not have suspected what was going on. Our little span of life does not give us the parallax necessary. The rock strata, miles thick, may be being flexed now under our feet, and we know it not. The earth is shrinking, but so slowly! When, under the slow strain, the strata suddenly give way or sink, and an earthquake results, then we know ...
— Time and Change • John Burroughs
... inference points, if we are careful to set the logical conditions with complete impartiality. But the ulterior question remains, whether, so far as science is concerned, it is here possible to point any inference at all: the whole orbit of human knowledge may be too narrow to afford a parallax for measurements so vast. Yet even here, if it be true that the voice of science must thus of necessity speak the language of agnosticism, at least let us see to it that the language is pure; let us not tolerate any barbarisms introduced from the side of aggressive ...
— Mind and Motion and Monism • George John Romanes
... periodical part. In both cases the motion may be either a reflex of the motion of the observer, and is then called parallactic motion, or it may be caused by a real motion of the star. From the parallactic motion of the star it is possible to deduce its distance from the sun, or its parallax. The periodic parallactic proper motion is caused by the motion of the earth around the sun, and gives the annual parallax ([pi]). In order to obtain available annual parallaxes of a star it is usually necessary for ...
— Lectures on Stellar Statistics • Carl Vilhelm Ludvig Charlier
... our lazy men, of whom there were too many. In calling us up he began with the A's, following down the class in alphabetic regularity. While Brooks was reciting, it was easy for Brown, sitting next, to open his book, and calculating narrowly the parallax, to hold it concealed below the rail, while he diligently conned the page following. In his turn he rose well-primed, and spouted glibly, and so on down the class. Rumour went that our childlike professor declared he had never known ...
— The Last Leaf - Observations, during Seventy-Five Years, of Men and Events in America - and Europe • James Kendall Hosmer
... to some intent of the Maker therein. Things, therefore, in his view are no longer empty and hollow like old cast-off shoes, but pieces of sublime design. A beetle is sustained by earth, air, fire, and water, needs the sun and the sea, winter and summer, earth's orbit and parallax, needs whatever has been made, to set him on his legs. He carries the world in little, and is a creeping ...
— The Atlantic Monthly, Vol. 13, No. 76, February, 1864 • Various
... in the more complicated problems of mathematical astronomy. Give a woman ten minutes and she will describe a heliocentric parallax of the heavens. Give her twenty minutes and she will find astronomically the longitude of a place by means of lunar culminations. Give that same woman an hour and a half with the present fashions, and she can not find ...
— Model Speeches for Practise • Grenville Kleiser


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