|≈||approximately equal to|
|digits||indicates that digits repeat infinitely (e.g. 8.294 369 corresponds to 8.294 369 369 369 369 …)|
An attometer is a unit of length, a combination of the metric prefix atto (symbol a) and the SI unit of length meter (symbol m), equal to 10−18 meter or 1.0E-18 meter and its symbol is am. Plural name is attometers.
The light-second is a unit of length useful in astronomy, telecommunications and relativistic physics. It is defined as the distance that light travels in free space in onesecond, and is equal to exactly 299792458 metres (just over 186282 miles).