Dictionary > Parallax

Parallax

parallax
1. The apparent displacement, or difference of position, of an object, as seen from two different stations, or points of view.
2. (Science: astronomy) 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. 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; as, the annual parallax of a fixed star. 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, 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.
Origin: Gr. Alternation, the mutual inclination of two lines forming an angle, fr. To change a little, go aside, deviate; beside, beyond – to change: cf. F. Parallaxe. Cf. Parallel.


You will also like...

3D rendering of an antibody
Passive and Active Types of Immunity

Lymphocytes are a type of white blood cell capable of producing a specific immune response to unique antigens. In thi..

Growth and Plant Hormones
Growth and Plant Hormones

Plants, like animals, produce hormones to regulate plant activities, including growth. They need these hormones to respo..

Human Reproduction
Human Reproduction

Humans are capable of only one mode of reproduction, i.e. sexual reproduction. Haploid sex cells (gametes) are produced ..

Gene Pool and Speciation
The Gene Pool and Population Genetics

According to Charles Darwin's theory of natural selection, preferable genes are favored by nature in the gene pool, and ..

Electromagnetic spectrum of a brain
Sleep and Dreams – Neurology

While learning and intelligence are associated with the functions of a conscious mind, sleep and dreams are activities o..

Human gastrointestinal tract
Human Biology – Food and Digestion

This tutorial recognizes the importance of food as a source of energy that will fuel many biological processes. A good d..