what is this thing?
A device used for measuring wind speed and direction.
Anemometer
An anemometer is a device used for measuring wind speed and direction. 
what is wind? The flow of gases on a large scale. what is the reason behind the flow? It is caused by differences in atmospheric pressure. how is it measured? By anemometers.
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Anemometer [SEP] Introduction
An anemometer is a device used for measuring wind speed and direction. It is also a common weather station instrument. The term is derived from the Greek word "anemos", which means wind, and is used to describe any wind speed instrument used in meteorology. The first known description of an anemometer was given by Leon Battista Alberti in 1450.