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.
Discuss thermal knockdown and the limitations in various magnet materials. All magnetic materials are at all times as fully magnetized as their thermal state permits. Prior to magnetization their magnetic domains arrange randomly to minimize their internal (and external) energy state.