attoparsec

n.

About an inch.*atto-* is the standard SI prefix for multiplication by \(10^{-18}\). A parsec (parallax-second) is 3.26 light-years; an attoparsec is thus \(3.26 × 10^{-18}\) light years, or about 3.1 cm (thus, 1 attoparsec/ microfortnight equals about 1 inch/sec). This unit is reported to be in use (though probably not very seriously) among hackers in the U.K. See micro-.