The true position of these stars is only approximate to their theoretical equidistant rhumbs on the sidereal compass. The western half of the rose would be the same stars in their setting position. Reading from North to South, in their rising and setting positions, these are: Point The other thirty points on the sidereal rose were determined by the rising and setting positions of fifteen bright stars. In the northern hemisphere, the steady Pole Star ( Polaris) was used for the N-S axis the less-steady Southern Cross had to do for the southern hemisphere, as the southern pole star, Sigma Octantis, is too dim to be easily seen from Earth with the naked eye. Arab navigators in the Red Sea and the Indian Ocean, who depended on celestial navigation, were using a 32-point sidereal compass rose before the end of the 10th century. The sidereal compass rose demarcates the compass points by the position of stars in the night sky, rather than winds. The following table gives a rough equivalence of the classical 12-wind rose with the modern compass directions (Note: the directions are imprecise since it is not clear at what angles the classical winds are supposed to be with each other some have argued that they should be equally spaced at 30 degrees each for more details, see the article on Classical compass winds). During the Migration Period, the Germanic names for the cardinal directions entered the Romance languages, where they replaced the Latin names borealis with north, australis with south, occidentalis with west and orientalis with east. 830), the Frankish king Charlemagne himself came up with his own names for the classical 12 winds. Ĭlassical 12-wind rose, with Greek (blue) and Latin (red) names (from Seneca)Īccording to the chronicler Einhard ( c. The De architectura of the Roman architect Vitruvius describes 24 winds. Septentrio, Subsolanus, Auster, Favonius, etc. Seneca, Pliny) adopted the Greek 12-wind system, and replaced its names with Latin equivalents, e.g. Eratosthenes deducted two winds from Aristotle's system, to produce the classical 8-wind rose. To restore balance, Timosthenes of Rhodes added two more winds to produce the classical 12-wind rose, and began using the winds to denote geographical direction in navigation. In his meteorological studies, Aristotle identified ten distinct winds: two north-south winds ( Aparctias, Notos) and four sets of east-west winds blowing from different latitudes-the Arctic circle ( Meses, Thrascias), the summer solstice horizon ( Caecias, Argestes), the equinox ( Apeliotes, Zephyrus) and the winter solstice ( Eurus, Lips). Nonetheless, both systems were gradually conflated, and wind names came eventually to denote cardinal directions as well. The four Greek winds ( Boreas, Notos, Eurus, Zephyrus) were confined to meteorology. The four Greek cardinal points ( arctos, anatole, mesembria and dusis) were based on celestial bodies and used for orientation. The ancient Greeks originally maintained distinct and separate systems of points and winds.
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