Kite

A kite is a tethered, heavier-than-air craft. It uses wing surfaces to interact with the air. This interaction creates two main forces: lift and drag. Lift is the upward force that keeps the kite in the sky. Drag is the horizontal force that pulls the kite in the direction of the wind. To keep the kite from flying away, it must be attached to a tether. A tether is a line that connects the kite to an anchor. This anchor can be a person, a boat, or even a vehicle.

The science of flight relies on how air moves around the kite's surface. As air flows, it creates low pressure on the top of the wings. At the same time, it creates high pressure underneath the wings. This difference in pressure generates the lift required for flight. The wind also creates horizontal drag. The tension from the tether opposes these forces to maintain a steady position. Some kites use a bridle, which is a set of lines, to help guide the face of the kite. Others, like box kites, might only use a single attachment point.

Kites come in many different shapes and designs. The delta kite and the diamond kite are very popular styles. Some designs are built for stability, while others are built for movement. Modern aerobatic kites often use two or four lines. These extra lines allow a pilot to have fine control over the kite's angle. There are also power kites, which are multi-line steerable kites. These are designed to generate massive forces for pulling people. Other specialized designs include the tetrahedral kite, the sled kite, and the parafoil.

The history of the kite stretches back thousands of years. Some historians claim Chinese philosophers Mozi and Lu Ban invented them in the 5th century BC. They originally flew wooden kites called muyuan. When paper was invented during the Han dynasty, kites became known as zhiyuan.

By 549 AD, kites were being used for rescue missions. During the Tang dynasty, people attached flutes and whistles to kites. This created sound in the wind, leading to the name fengzheng. In India, the kite evolved into the patang, which is flown during festivals like Makar Sankranti.

Kites have played a major role in scientific discovery. In 1752, Benjamin Franklin used a kite to prove that lightning is actually electricity. Kites were also vital to the research of the Wright brothers. They used kites to help develop the first practical airplanes. In the 19th century, kites helped meteorologists measure atmospheric conditions. They were even used to lift radio antennas for wireless communications. For example, Marconi used a kite-carried antenna for his first transatlantic transmission.

Throughout history, kites have also been used for military purposes. During the Song dynasty, the Chinese developed the Fire Crow. This was a kite that carried incendiary powder and a burning stick of incense. In 647 AD, a Korean general named Kim Yu-sin used flaming kites to frighten enemies. In the 20th century, the British Army used man-lifting kites to hoist observers into the air. During World War II, barrage kites were used to protect ships. Even in modern times, kites have been used in conflicts to set fires.

Today, kites are used for many different activities. Many people fly them for recreation or as a form of art. Sport kites are used in aerial ballet competitions. Power kites allow for extreme sports like kite surfing, kite landboarding, and snow kiting. These activities use the kite as a traction source to pull the user. Modern kites are often made from lightweight synthetic materials. These include ripstop nylon, plastic film, and carbon fiber. High-strength ropes like Kevlar or Dyneema are used for the lines.