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More About Weathervanes And How They Work

By Melissa Davis


A weather vane will point in the direction from which the wind is blowing. It is placed in the highest, most unobstructed location on a structure. It only works properly if the wind flows freely and is not blocked by trees or other buildings. For those who did not have our modern instruments for measuring wind direction and speed, weathervanes had great significance.

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.

It was in the ninth century that it was decreed that all churches must have a rooster weather vane on their domes or steeples. Roosters were used for hundreds of years after that on churches in Britain and America and they are still popular today. Perhaps this is because of their significance as a symbol of light conquering darkness and bringing in the dawn, or it could be simply because the tail of a rooster catches wind well. The force on the tail is greater than on the head and so the head swings to face the wind.

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 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.

On the weather vane, just underneath the pointer, are fixed directional markers. They point towards the north, south, east and west. If the arrow is pointing toward the marker for north on the weather vane, wind is blowing from the north to the south.

When observers look at changing directions and wind patterns, they can make simple forecasts. Forecasts are based on other factors too, such as knowledge or experience of local climatic conditions. If they know that the north is cold and the south is warm, for example, they know what to expect when wind comes from that direction.

Knowing about where the wind was coming from was a great help to farmers in the past. They would examine the signs daily and put together their knowledge about the local area and climate to make their predictions. This could help them plant their crops in the right places and protect them. Today, we no longer need to determine weather by using weather vanes. We have plenty of modern instruments that are far superior. However, the appeal of this instrument remains and many people still enjoy placing them on their homes.




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