Balloon is a bag filled with heated air or a light gas so that it rises and floats in the air. A balloon rises because the heated air or gas inside is lighter and less dense than the surrounding air.
Balloons are made in many sizes, shapes, and designs and have many uses. Children play with toy balloons. Scientists use balloons to carry instruments that gather information about the weather. Balloons equipped with transmitters are used to relay radio and television programs to remote areas. Some balloons have a basket attached beneath the bag to carry a pilot and passengers. Such large, piloted balloons are used by people who enjoy the thrill of sport ballooning. Piloted balloons are also used for scientific research.
Balloons may be captive, free-floating, or powered. A captive balloon is anchored to the ground by a cable. A free-floating balloon travels in whatever direction the wind blows. A pilot can control the vertical movement of a piloted, free-floating balloon but cannot steer it. However, the pilot can control the course of a balloon flight to some degree by rising or descending to find a wind blowing in the desired direction. A powered balloon is called an airship. An airship has an engine and propellers to power it, along with rudders and instruments that enable a pilot to steer it.
