If a job is useful, you would think that it should always be important. People always need electrical work and plumbing in their homes and offices, for example, and experts […]
The helicopter was invented by the Chinese in the 4th century, more than a 1,000 years before Leonardo da Vinci. It was called the Bamboo Dragonfly and could fly 25 feet (7.6 m) up and down. The first modern helicopter was invented by the French.