Word origin · etymology
Greek through French.
Greek parallaxis means alteration, from a verb meaning to change. Astronomy applies the name to a viewpoint-dependent shift.
How we know · epistemology
Observable geometry
A baseline change produces a geometrically testable directional shift. Its size depends on distance and observer separation; a single geocentric longitude does not capture the full local effect.
Connected concepts
Mentioned in 1 other entry
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Sources & provenance
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