### Slugs, Parsecs, and Other Units of Measure

Sometimes, scientists use unusual units of measure when conventional units prove impractical. For example, in physics, a slug is the unit of mass that is accelerated at the rate of one foot per second per second when acted on by a force of one pound. In astronomy, a parsec is a unit of length for interstellar distances, equal to 206,265 times the distance from the Earth to the Sun—3.26 light-years or about 19 million million miles (3.08 × 1013 km). What are some other unusual units of measure?