parallax means an apparent shift in the position of two stationary objects relative to each other as viewed by an observer, due to a change in observer position.
parallax is pronounced /ˈpæɹ.əˌlæks/.
Why “parallax” is a great word
The apparent displacement in the position of an object when viewed from two different lines of sight. From Middle French *parallaxe*, from Ancient Greek παράλλαξις (*parállaxis*, 'alteration, change of position'), from παραλλάσσω (*parallássō*, 'to cause to alternate'), from ἀλλάσσω (*allássō*, 'to alter, change'), from ἄλλος (*állos*, 'other'); first recorded in English 1585–95. Unlike perspective, which frames a general point of view, or illusion, which denotes a deceptive impression, parallax is a specific, measurable optical phenomenon—a tool of science, not a trick of the mind. It is the fence-post that races across a distant hill when you shift your head; the moon that drifts against the fixed stars when observed from opposite ends of Earth's orbit; the rifle scope calibrated to the shooter's particular stance. It is the fundamental proof that to see a thing truly, you must regard it from more than one place, for the gap between two viewpoints is itself a measurable, navigable space.
Etymology
From Middle French parallaxe, from Ancient Greek παράλλαξις (parállaxis, “alteration”) from παραλλάσσω (parallássō, “to cause to alternate”) from ἀλλάσσω (allássō, “to alter”) from ἄλλος (állos, “other”). By surface analysis, par- + all- + -ax.
noun
- An apparent shift in the position of two stationary objects relative to each other as viewed by an observer, due to a change in observer position.“[…] Heliocentrick places, to which the Parallaxes being applied, give the Geocentrick.”
- The angle of seeing of the astronomical unit.
verb
- To measure (a distance) based on parallax observations.
- To produce an illusion of levels of distance by shifting layers at different rates.
Words closest in meaning
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