About 31 mm (one 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. Thus, one attoparsec per microfortnight is about one inch per second.This unit is reported to be in use (though probably not very seriously) among hackers in the UK. [Jargon File]
Last updated: 1996-12-08
attenuation ♦ atto- ♦ attoparsec ♦ attribute ♦ Attributed File System
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