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    Tower of The Winds: The World’s First Weather Station

    The Tower of the Winds, or the Horologion of Andronikos Kyrrhestes, is an elegant octagonal marble tower in the Roman Agora in Athens. It is considered to be the world’s first meteorological station. More than 2,000 years old, the tower has eight sides corresponding to the eight principle winds, a sundial to tell time, a wind vane to show the direction of wind and an interior water clock that in antiquity could be read even in darkness.
    Each of the building’s eight sides face a point of the compass and is decorated with a frieze of figures in relief representing the winds that blow from that direction.
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    Tower of the Winds. Photo credit: Viacheslav Lopatin/Shutterstock
    The ancient Greeks believed that winds blew from twelve different directions, and these directions eventually became a way of figuring out one’s geographic orientation just like the four cardinal directions we use today. It’s not known when or why people started using wind as cardinal directions, but it probably began with the farming population. These ancient observant farmers recognized that the quality of winds differed depending on where the wind was blowing from. Some winds were humid, some were dry, some hot and some cold. Sailors too relied heavily on wind directions and could also recognize a particular wind by its qualities.
    The ancient Greeks originally maintained distinct and separate systems of points and winds. The four Greek cardinal points (arctos, anatole, mesembria and dusis) were based on celestial bodies and used for orientation, while the four Greek winds (Boreas, Notos, Eurus, Zephyrus) were confined to meteorology. Eventually, both systems were merged, and wind names gradually came to denote cardinal directions as well.
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    Aristotle’s wind rose
    The Greek philosopher 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). Aristotle explained that each wind had different meteorological properties. For instance, winds on the NW-SE axis are generally dry, while the NE-SW winds are wet. N and NNE winds bring snow, while those from the whole northwestern sector (NW, NNW, N) bring hurricanes.
    However, Aristotle's system was asymmetric. To restore balance, Timosthenes, a Greek navigator and geographer, added two more winds to produce the classical 12-wind rose. But another Greek geographer, Eratosthenes of Cyrene, realizing that many winds presented only slight variations, reduced the twelve winds down to eight principal winds, marking a significant step towards the evolution of the 8-point compass rose that’s still used in almost all navigation systems, including nautical charts, maps, compass and even GPS.
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    An 8-wind compass rose
    The Tower of the Winds was based on Eratosthenes’s eight-wind system, with each side of the octagonal tower facing a wind direction. On the sides facing the sun, are the lines of a sundial. In antiquity, the tower was surmounted by a weather vane in the form of a bronze Triton and contained a water clock to record the time when the sun was not shining. Located in the Roman Agora (market place), the tower was of great value for the merchants who used it to read the weather and predict when their goods would arrive by sea.
    The tower is said to have been built by Andronicus of Cyrrhus (c. 50 BCE) but according to other sources, it might have been constructed in the 2nd century BC. Its use as a weather station, however, was short lived. During the Roman times the tower was vandalized and the mechanism looted. Then, the building became a clock tower for an Eastern Orthodox church. Under Ottoman rule, the monument was also used as a place of worship by Sufi Muslim Whirling Dervishes.
    The monument was largely closed to the public since the Dervishes left in 1828. It was only in 2016 that the tower was restored and opened to the public after nearly two hundred years of neglect.
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    Photo credit: Ava Babili/Flickr
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    Photo credit: Borisb17/Shutterstock

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