Celestial navigation Celestial navigation Celestial navigation, also known as astronavigation, is the ancient and modern practice of position fixing that enables a navigator to transition through a space without having to rely on estimated calculations, or dead reckoning, to know their position. Celestial navigation uses "sights", or angular measurements taken between a celestial body (e.g. the Sun, the Moon, a planet, or a star) and the visible horizon. The Sun is most commonly used, but navigators can also use the Moon, a planet, Polaris, or one of 57 other navigational stars whose coordinates are tabulated in the nautical almanac and air almanacs.
Abnormal profit industry structure and firm performance were determinants of whether abnormal profits could be sustained by firms. Abnormal profit In economics, abnormal profit, also called excess profit, supernormal profit or pure profit, is "profit of a firm over and above what provides its owners with a normal (market equilibrium) return to capital." Normal profit (return) in turn is defined as opportunity cost of the owner's resources. A related broader term is economic rent, which applies to the owner of a resource, such as land, rather than to the firm as such. According to the theoretical model of perfect competition, abnormal profits