On a windy day, it may seem to you that the wind is moving at tremendous speed. Then you hear the weather report and it says, “Winds of 10 to 15 miles per hour.” It’s easy for us to be fooled about the speed of the wind. But the exact wind speed is important to many people, so there are scientific ways of measuring the wind.

The first instrument for measuring the speed of the wind was invented in 1667 by an Englishman named Robert Hooke. The instrument is called an anemometer. There are many kinds of anemometers, but the most common type now used has a number of aluminum cups on a spindle. They are free to turn with the wind, and the harder the wind blows, the faster the cups will turn. By counting the number of turns made by the cups in a given time, the speed of the wind may be calculated.

When men began to fly, it was necessary to measure the winds at high altitudes. This was done by sending weather balloons up into the atmosphere and watching them with a special kind of telescope called a theodolite. But this wasn’t much good when clouds hid the balloon. In 1941, weather radar was invented. And now a radar set can observe the balloon even through clouds and measure the winds in the upper air!

People have long been interested in knowing the direction of the wind. As long ago as A.D. 900, wind vanes were put on church steeples to show the direction of the wind!