You can feel the wind that blows on your face and see it blowing things around. But, what is wind? How it is formed? What does it do? Wind is air in motion. It is created by the uneven (tidak rata) heating of the Earth’s surface by the Sun. Since the Earth’s surface is made of different types of land and water, it absorbs the heat from the Sun at different rates (kadar).During the day, the air above the land heats up more quickly than the air over water. The warm air over the land expands and rises. The cooler air, from the surface of the sea, rushes (menderu) in to take its place. This wind is called sea breeze (bayu laut).
At night, the land cools faster than the surface of the sea. In this case, the warmer air above the surface of the sea rises and pulls in air from the cooler land surface. This wind is called land breeze (bayu darat).
Wind can be named based on its direction (arah) and speed (kelajuan). Wind may blow from east, west, south, north, northeast (timur laut), northwest (barat laut), southeast (tenggara) and southwest (barat daya). To fi nd the wind direction, people use a wind vane (baling-baling angin). A calm wind, called a breeze, can make smoke drift and fl ags fl utter but a very strong wind, called a hurricane, can blow away trees and houses. People also give a special name to the wind that blows over their places and some of the names are Chinook (from Pacifi c Ocean to Rocky Mountains), Mistral (from Central France to Mediterranean) and Bora (from Eastern Europe to Italy).
Winds are very useful to us. It controls the temperature of the Earth, pushes clouds and sailboats, and also generates electricity. Wind is one of the least expensive forms of renewable (boleh diperbaharui) energy available. Some experts say it can sometimes be the cheapest form of energy source. Generating electricity from the wind does not leave dangerous waste products behind. Best of all, its supply is unlimited (tidak terhad).
There are so many interesting facts about winds. Here are some of them:
• The windiest (paling berangin) place in the world is Port Martin, Antarctica. It has an average wind speed of 64 km/h over a year.
• Only 1% of the world electrical energy is generated using winds.
• The first practical windmill was built in Sistan, Afghanistan in 7th century.
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