What is "parallax"

Parallax \Par"al*lax\, n. [Gr. ? alternation, the mutual inclination of two lines forming an angle, fr. ? to change a little, go aside, deviate; para` beside, beyond + ? to change: cf. F. parallaxe. Cf. Parallel.]

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.
   --Brande & C.

   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.

1570s, from Middle French parallaxe (mid-16c.), from Greek parallaxis "change, alteration, inclination of two lines meeting at an angle," from parallassein "to alter, make things alternate," from para- (see para- (1)) + allassein "to change," from allos "other" (see alias (adv.)). Related: Parallactic.

n. 1 The change of angular position of two stationary points relative to each other as seen by an observer, due to the motion of an observer. 2 The apparent shift of an object against a background due to a change in observer position. 3 The angle of seeing of the astronomical unit.

n. the apparent displacement of an object as seen from two different points that are not on a line with the object

Parallax is a displacement or difference in the apparent position of an object viewed along two different lines of sight, and is measured by the angle or semi-angle of inclination between those two lines. The term is derived from the Greek word παράλλαξις (parallaxis), meaning "alteration". Due to foreshortening, nearby objects have a larger parallax than more distant objects when observed from different positions, so parallax can be used to determine distances.

Astronomers use the principle of parallax to measure distances to the closer stars. Here, the term "parallax" is the semi-angle of inclination between two sight-lines to the star, as observed when the Earth is on opposite sides of the Sun in its orbit. These distances form the lowest rung of what is called "the cosmic distance ladder", the first in a succession of methods by which astronomers determine the distances to celestial objects, serving as a basis for other distance measurements in astronomy forming the higher rungs of the ladder.

Parallax also affects optical instruments such as rifle scopes, binoculars, microscopes, and twin-lens reflex cameras that view objects from slightly different angles. Many animals, including humans, have two eyes with overlapping visual fields that use parallax to gain depth perception; this process is known as stereopsis. In computer vision the effect is used for computer stereo vision, and there is a device called a parallax rangefinder that uses it to find range, and in some variations also altitude to a target.

A simple everyday example of parallax can be seen in the dashboard of motor vehicles that use a needle-style speedometer gauge. When viewed from directly in front, the speed may show exactly 60; but when viewed from the passenger seat the needle may appear to show a slightly different speed, due to the angle of viewing.

__NOTOC__ "Parallax" is the third episode of the science fiction television series Star Trek: Voyager.

A parallax is the difference in the angular position of two stationary points relative to each other from different viewing positions. Parallax may also refer to:

Parallax is the fourth studio album by guitarist Greg Howe, released on November 7, 1995 through Shrapnel Records.

Parallax is the third studio album from Bradford Cox's solo project Atlas Sound, released November 7, 2011 on 4AD. The album debuted at #97 on the Billboard 200 and has received mostly positive reviews.

Parallax is a fictional comic book supervillain in the DC Comics universe. Created by writer Ron Marz and artist Darryl Banks for Green Lantern vol. 3, #48 (January 1994), Parallax was originally devised as the new supervillain identity for then-former Green Lantern protagonist Hal Jordan. After further changes for the Hal Jordan character over the subsequent years (sacrificing his life in order to reignite Earth’s Sun in the 1996 crossover storyline " The Final Night", and Jordan’s soul subsequently becoming the newest host of the Spectre in the 1999 miniseries Day of Judgment), 2004's Green Lantern: Rebirth once again cast Jordan as a heroic Green Lantern and explained Parallax as an ancient entity embodying the yellow light of fear which possessed Jordan and drove him to villainous action. Parallax was revealed to have been once imprisoned within the Central Power Battery on the planet Oa, from which all Green Lanterns derive their power, and was the reason for the yellow impurity that in the past rendered the rings useless against anything yellow.

In 2009, Parallax was ranked as IGN's 92nd Greatest Comic Book Villain of All Time.

Parallax is an Australian children's television series that screened on the Nine Network. It is a 26 episode series funded by the Film Finance Corporation Australia and supported by Lotterywest. The series was filmed in various locations around Perth, Western Australia. These include Kings Park, East Perth, and many beach and South West forest locations.

The series is about a boy named Ben Johnson, who discovers a portal to multiple parallel universes, and explores them with his friends: Francis Short, Melinda Bruce, Una, Due, Tiffany and Mundi as well as newfound sister, Katherine Raddic.

parallax is a quarterly peer-reviewed academic journal publishing work in cultural studies, critical theory and philosophy. Each issue has a theme and issues are regularly compiled by guest-editors. The journal was established in 1995 by Adrian Rifkin, Marq Smith and Joanne Morra, and is now published by Routledge. The editors are Agnieszka Jasnowska, Thomas Hastings, Elizabeth Stainforth and Lenka Vrablikova ( University of Leeds).