Centurylength

Centurylength is a neologism used to denote a unit of length defined by the distance light travels during a century. It is not a standard unit in any scientific system and is mainly encountered in speculative writing, thought experiments, or educational demonstrations of scale.

In its typical definition, a centurylength equals the distance light covers in 100 years in vacuum. Using the Julian year of 365.25 days, this is about 9.46 × 10^17 meters, roughly 100 light-years or about 30.7 parsecs. Because it is based on the speed of light, its theoretical value is relatively fixed, but there is no official standard, and the term is not part of established nomenclature.

Usage is mostly limited to illustrate vast cosmic distances in a single figure. In science fiction, centurylengths help convey interstellar spacetime scales; in teaching contexts, they can help students compare speed, time, and distance without invoking multiple units. The term can serve as a didactic shortcut rather than a precise measurement.

Relation to other units: 1 centurylength equals 100 light-years and about 30.7 parsecs. It is far larger than typical terrestrial units and, in practice, less precise than established astronomical units because the term is not standardized and can be defined differently if used at all.

See also: light-year, parsec, astronomical unit.