Convert from mark twain to hubble

Unit Definition (mark twain)
The mark twain or twain is an old word for the number two, derived from the Anglo-Saxon twegen. The American author Samuel Clemens (1835-1910), who had been a riverboat pilot on the Mississippi in his youth, took his literary name from a traditional riverboat phrase "mark twain", meaning "exactly two" fathoms of water. This was the minimum depth needed for the boats to operate safely without running aground.

Unit Definition (hubble)
The hubble is a unit of distance sometimes used in astronomy. The hubble is a gigantic unit, equal to 10E9 light years. This is 9.4605 x 10E21 kilometers (9.4605 yottameters, if you please), 5.8785 sextillion miles (U.S.), 63.240 x 10E12 astronomical units, or 306.595 megaparsecs. In practice, most astronomers use the megaparsec for measuring such stupendous distances. The unit honors the American astronomer Edwin Hubble (1889-1953), who discovered the expansion of the Universe later explained by the Big Bang theory.