Windswept_ The Story of Wind and Weather - Marq de Villiers [25]
Why wasn't it evident to the ancients?
I suppose the answer is to be found in context. The natural philosophers of the past just didn't—yet—have the conceptual framework to understand how wind worked. This is the familiar story of the scientific method, of course. It is the way scientific understanding advances. First come the framing theories, almost always wrong, then the painstaking accumulation of data, then corrected theories, then more data, and only afterward the brilliant insight. After which, the pattern repeats itself . . .
The history of thinking about wind paralleled the thinking about air itself. It was similar, but not the same.
The first of the framing theories, the first quasi-scientific definition of wind, was that of Anaximander, the same Anaximander whose considered view of air (that every thing, earth and the heavens above, came into existence when the primordial sea was dried by celestial fires, source of said fires unspecified) was recounted in the previous chapter. All nature, in this view, was the product of a few simple properties—hotness and coldness, wetness and dryness, lightness and darkness. So far, so familiar. But then he made a big conceptual breakthrough: Wind, he suggested, was a current formed when mists were burned off by the sun. Later, he simplified the notion: Wind, he said, was "a flowing of air."1 Two hundred or so years later Empedocles, the inventor of the four-elements theory of matter, conducted the first experiment to demonstrate what wind really was. He used a simple flow tank to show that air and wind were really the same thing.2
Aristotle, writing three hundred years later, agreed with much of what Anaximander had to say about air—indeed, he codified and improved the earlier man's musings—but on wind he couldn't go along. He rejected the whole idea, just as he had the notion of atoms. He thought it self-evidently false, and that the people who adhered to the theory were bringing the whole idea of philosophical thought once more into disrepute—obviously, scholarly dignity was a sensitive subject in the Athens academies. If winds were indeed a "flowing of air," he wrote, this must mean that all winds were one wind because all air was one air. To him, this was self-evidently false. "This is just like saying all rivers are one and the same river, and an ordinary man's view is better than a [mediocre] philosopher's view like this one," he declared, with rather lumbering irony.3 Still, he wasn't altogether off the mark when he wrote that the sun pushes the winds and checks their speeds; in a way, that is indeed what happens. You can say with some truth that wind is, as Aristotle wrote, an exhalation arising from the earth.
While this philosophical wrangling was going on in the Athenian schools, practical Greeks were making the first attempts to blend legend and fact. In this they were the global forerunners, as they were in much else besides. Homer and his contemporaries had only identified the four cardinal winds, but this was too crude a measure for decent navigation, and the increasingly skilled sailors of later generations began to parse the directions ever more finely into increasingly useful and accurate segments, generally using the sun's movement as a guide, since magnetic north was still unknown. This new precision was graphically depicted in the Tower of the Winds, an eight-sided building erected in the market place of Athens, now the Plaka district, by Andronicus of Cyrrhus, somewhere between ioo and 50 B.C. The tower still stands, in decent though not pristine shape, and the eight winged gods representing the eight important winds can still be seen as a marble frieze, the figures in relief. The tower is only about forty feet tall. Sundials protrude from all sides (it was also called the Horologium, or timepiece) and a water-powered clock was built into the south wall. This clock was said to have