Ford has beaten General Motors for the first time in nearly a century, in terms of number of US factory workers. Ford has 50,703 to GM's 50,300 or so.
Answers. Well, the simplest answer is that the astrolabe pretty well had to be used at night and could not be used in bad weather. The compass, which relys on the magnetic field of the Earth rather than a visualiztion of the stars, works at any time, and in any weather.
Evidence suggests that the magnetic compass was invented in China between 221 and 206 B.C. The earliest compasses were not used for navigation, but for fortune-telling. Chinese compasses became navigational orienteering devices between 1040 and 1044 A.D. and were used as maritime navigational devices by 1117 A.D.