Consider the power of wind. This invisible, uncontrollable force affects commerce, agriculture, military strategy, transportation, recreation, and industry. With knowledge (and some luck), we can harness it to generate power and aid in flight. And we can measure it, hoping to interpret wind’s clues about future conditions -- observations that can make the difference between life and death.
Long ago, scientists discovered that reading the wind’s signals aided in predicting the weather, an ability we often take for granted as little more than a modern convenience to help us choose comfortable clothing or plan outdoor activities. Catastrophic storms remind us that weather forecasts can be vital to survival — whether for taking shelter, scheduling a journey, timing the planting and harvesting of crops or planning a military battle.
One of the oldest tools for predicting the weather is the wind vane. Also called weather vanes, these devices indicate the source of wind, providing clues about the incoming air’s temperature and moisture. For example, if wind is from the south, conditions are likely to become warm and more humid. Wind from the north signals a potential drop in temperature. A sudden shift in the wind’s direction foretells a more severe change in the weather, possibly a storm.
Photo shown above: In the ninth century, Rome decreed (by papal edict) that churches prominently display the figure of a rooster as a reminder of Peter’s betrayal of Christ. Because a town’s wind vane typically sat atop the church steeple (where it could best capture the wind), the rooster design was incorporated as an enhancement to the arrow indicator. The term weathercock was soon synonymous with weather vane.
The design of a wind vane is simple. Unlike a windsock or a flag (both of which indicate wind direction), the wind vane has a fixed base that designates north, south, east and west. From its center, a vertical post supports a freely revolving figure such as an arrow or an animal. The shape is balanced side-to-side but has a smaller surface area on the front; the larger “tail” end offers the most wind resistance and is pushed away from the wind’s source. The pointer (or head) therefore aims into the direction from which wind is coming.
Once bearing symbolic value, the figures used in wind vanes have embraced aesthetic sensibilities, often representing the owner’s interests and tastes. The classic rooster motif had its origin in the Catholic church (see photo below), and that design has endured. But today style often takes precedence over function; you can find wind vanes in all kinds of shapes and perched away from open wind, such as on a coffee table or atop a dog house.
In 1450 Italian architect Leon Battista Alberti devised the anemometer, a slightly more complex instrument, which measures wind speed and pressure. Since then inventors have created many variations, but the basic instrument — along with the simple weather vane — still claim high standing in weather stations throughout the world.
The Tower of the Winds in Athens (built circa 50 B.C.) once supported what is considered by many to be the first true weather vane. Greek astronomer Andronicus designed the octagonal structure to bear representations of the eight wind deities. A bronze figure of Triton (also a Greek god) rotated on the top, pointing in the direction of the god whose wind prevailed, indicating which deity was presently in control of the weather.