For thousands of years people have harnessed the wind's energy. People used wind to sail their ships on the rivers and oceans. Later, windmills were built and used to grind wheat, corn, and other grains as well as to pump water from wells and cut wood in sawmills. Today we use wind energy to generate electricity.
Where does wind come from?
Wind is caused by the uneven heating of the earth's surface by the sun. During the day the air above land heats up faster than the air above water such as oceans and lakes, making the air above water cooler and heavier. The uneven heating of the air is due to the earth being made up of different surfaces and elevations, like the oceans, lakes and rivers, forests and jungles, deserts and mountains. The warm air over the land expands and rises, and the cooler air over the water rushes in to take the place of the warmer air, creating winds.