Orientation and Navigation

By the Stars

As seen from a particular location on Earth, a given fixed star always rises and sets at the same two places on the horizon (if it rises and sets at all). That is, a star rising above a particular reference point on the horizon on a given day will appear to rise at that same location every day throughout the year.

 
1. Sailors learned to guide their ships according to the rising and setting locations of fixed stars. This allowed them to determine their own position in latitude relative to their home or harbor. Anthony Aveni reports that the "people of Oceania created linear constellations, the member stars of which rose and set in vertical tracks over the ocean horizon at approximately the same azimuth. Such a system had considerable utility among races interested in navigation" (Skywatchers of Ancient Mexico, University of Texas Press, p. 56).

    

2. Similarly, Arabian nomads relied on the stars to navigate across trackless desert sands. The Quran affirms (6:95): "It is God who has appointed for you the stars, that by them you might be guided in the shadows of land and sea."

The altitude of Polaris is the quickest way to ascertain terrestrial latitude. Click here for an explanation of why the altitude of Polaris always equals the latitude of the observer. For example, the Pilgrims who landed in Plymouth Rock expected a relatively mild winter, comparable to that of England, for during their ocean journey they had maintained their ship's direction on the same latitude. However, due to unanticipated effects of ocean currents, the New England winter is much harsher than that in the same latitude in England.