Friday 16 February 2018

Facts About Weathervanes And How They Work

By Melissa Davis


A weather vane only works if wind can flow freely and is not obstructed. This is why these instruments are usually placed at the highest point on a structure like a church or a house. They are used to show the direction from which wind blows. In the past, farmers relied on weathervanes whereas today technological advances have given us instruments to accurately measure wind speed and direction.

The earliest weather vane in recorded history was built by the astronomer, Andronicus. It honored the Greek God Triton and was a combination of man and fish. In ancient Greece and Rome, weather vanes depicting the gods adorned the dwellings of wealthy landowners.

With the conversion of the Roman Empire to Christianity, a rooster began to appear on church steeples. It reminded believers of the need to be watchful because Jesus prophesied that Peter would deny him before the cock crowed three times. The tail of a rooster is just the right shape to catch the wind and its force is greater on the tail than the head. It gets pushed away so the head turns into the wind. This is probably why the rooster design remains so popular to this day. It also has symbolic relevance in that it welcomes the dawn and the triumph of light over darkness.

On a wind vane, the free-swinging directional pointer or arrow is thicker at the one end and thinner at the other. The larger end with the greater surface area catches the breeze. The small end turns to point in the direction from which a wind is coming, and the larger end turns to point where it is going.

A wind vane must be precisely balanced in order to be able to turn freely. Otherwise, it can topple or not move at all. To spin freely, weight has to be distributed equally on both sides of its axis. Some modern weather vanes are made purely for ornamental reasons and do not have this type of balance. They do not show wind direction because they lack this balance.

Directional markers are fixed below the pointer. They indicate north, south, east and west. When the arrow points towards the west, the marker for west shows that wind is blowing from that direction and toward the east. If the marker shows north, wind is blowing from the north and toward the south.

When people see wind direction, they start noticing patterns and when they put this together with knowledge about the local climate, they start being able to make simple forecasts. They may notice, for example, that wind from a certain direction usually brings rain or that wind from another direction may mean that a storm is coming.

Determining wind direction and what this meant was a daily consideration for farmers. Their first-hand observations, experience and local knowledge helped them in this exercise. Today, we do not need weather vanes for this reason but they continue to retain their appeal. A wide variety are available today in many different designs. Those that are designed correctly, still work in exactly the same way as they have through the centuries whilst others are valued for their aesthetic appeal.




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