balloon

An early example of the lighter-than-air balloon in a demonstration that took place indoors in 1784. Within a few years, balloon ascents were made and considerable distances travelled, but it was not until the late 19th century that weather conditions were understood sufficiently for balloonists to predict a destination.

Launching balloons at a wind festival. The use of balloons for recreational purposes such as this, and for advertising, has increased as their military importance has declined.

Hot air ballooning is a sport enjoyed by tens of thousands of people worldwide. The safest times to fly are early in the morning or in the evening just before sunset, when the sun is low in the sky and the wind is calm.

Lighter-than-air craft that consists of a gasbag filled with gas lighter than the surrounding air and an attached basket, or gondola, for carrying passengers and/or instruments. In 1783, the first successful human ascent was in Paris, in a hot-air balloon designed by the Montgolfier brothers Joseph Michel and Jacques Etienne. In 1785, a hydrogen-filled balloon designed by French physicist Jacques Charles travelled across the English Channel.

During the French Revolution balloons were used for observation; in World War I they were used by all sides as aerial observation posts for artillery spotters and as a form of air defence; in World War II they were used to defend London, England, against low-flying aircraft. They are now used for recreation and advertising, and as a means of meteorological, infrared, gamma-ray, and ultraviolet observation. The first transatlantic crossing by balloon was made in 1978 by a US team. In the late 1990s, NASA developed an Ultra-Long Duration Balloon to circle the Earth at the edge of space, but initial test flights in 2001 were unsuccessful.

Coal gas was substituted as a cheap alternative to hydrogen 1821, and this allowed for voyages by later 19th-century and early 20th-century explorers, scientists, and fairground performers. By the 1920s and 1930s balloons were used for high-altitude scientific research, especially before the development of high-altitude aircraft and Earth-orbiting satellites; for other kinds of research and exploration they were found to be generally unreliable, since they cannot be guided but go where the wind blows. They have become popular for sport and recreation, and continue in use as instrument-only observers for meteorology, and for monitoring infrared, ultraviolet, and gamma rays.

Balloons are also used with space probes, such as the Soviet Vega probes that placed atmospheric balloons in Venus's atmosphere in 1985.