Anemometer Anemometer An anemometer is a device used for measuring wind speed, and 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. The anemometer has changed little since its development in the 15th century. Leon Battista Alberti (1404–1472) is said to have invented the first mechanical anemometer around 1450. In following centuries, numerous others, including Robert Hooke (1635–1703), developed their own versions, with some
Lebesgue measure not have some curious properties which causes a discrepancy in the measure of another set when formula_6 is used as a "mask" to "clip" that set, hinting at the existence of sets for which the Lebesgue outer measure does not give the Lebesgue measure. (Such sets are, in fact, not Lebesgue-measurable.) The Lebesgue measure on R has the following properties: All the above may be succinctly summarized as follows: The Lebesgue measure also has the property of being "σ"-finite. A subset of R is a "null set" if, for every ε > 0, it can be covered with countably many