Parallaxes

Part of speech: noun, verb

Definitions

1. A measured difference in the apparent position of an object from two different viewpoints
2. An astronomical term used to describe the method of determining distances to celestial bodies based on positional shifts
3. The concept in optics explaining how objects appear to change position from varying angles of observation

Etymology: "Parallaxes" is simply the plural of "parallax," so the story is that of the singular. The Greek "parallaxis" meant "alteration" or "change," built from "parallassein," "to cause to alternate," which itself grew from "allassein," "to alter," rooted in "allos," "other." The sense of one thing shifting into another is still visible in the word's logic: the apparent position of an object changes when the observer moves to a different place. The term passed into European scholarly language through Middle French "parallaxe," and English adopted it for the astronomical sense that made it famous. Astronomers measured the tiny shift in a nearby star's position against distant stars as Earth moved around the Sun, and that measurement became a way of gauging distance.