Units of measurement let us describe and compare length, weight, area, volume, density and other values. Units can be imperial or metric.

The parsec is a more technical measurement that is derived from an astronomical unit and is used mainly by scientists. Technically, a parsec is defined as the distance at which 1 AU subtends a one ...

THROUGHOUT MUCH of human history, man has been the measure of many, if not all, things. Lengths were divided up into feet, palms, spans and smaller units derived from the human hand.

SI gets a makeover In daily life, however, the new SI units will have little immediate practical consequence. While the units may be defined differently, the goal has been to keep their size the same.