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More 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 Greek astronomer, Andronicus, was recorded as building the first weather vane. It sat on top of a tower in Athens. It was built in honor of Triton, Greek god of the sea, and was half human, half fish. Triton held a wand that showed the direction in which wind was blowing. The ancient Romans also used weather vanes.

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.

The weather vane is shaped aerodynamically. The one end of its pointer is thicker than the other and has a larger surface area. This enables it to catch wind and turn the pointer. The large end points to where wind is going and the small end to where it is coming from.

A weather vane that is shaped correctly and has balance will spin freely. If it is not precisely balanced, it will shift or topple and even stop moving. The weight needs to be equally distributed on either side of the axis or the vane will not spin freely. Some modern weather vanes do not have the necessary weight balance. They are designed more as architectural ornaments than for determining wind direction.

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.

Farmers relied on weather vanes to help them know more about the weather. This was important when making such decisions as to when and where to plant crops and whether to plant windbreakers. They put the information about the wind together with other knowledge to make these decisions. Today, we do not use weather vanes in the same way. They are still popular and many people have them on their houses or barns but they are used more for ornamental and sentimental reasons.




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