From the beginning of history humans have looked up at the stars and wondered about their nature. They developed science to understand their motions (see astronomy). As technology improved in the 20th century, it became possible to send machines and later animals and finally human beings above Earth’s atmosphere into space.
Space exploration has taken many forms, but all missions that take place in outer space must adhere to certain basic physical laws. In addition, they must be able to withstand harsh environments in which people will live and work for extended periods of time.
The first artificial satellite, Sputnik 1, was launched by the Soviet Union on October 4, 1957. Since then thousands of spacecraft have been built to perform a wide variety of tasks. Some are designed to fly by, crash on, or orbit planetary bodies such as the Moon or Saturn’s moons. Others are tasked with conducting scientific research in the gaseous outer planets, or sending data back to Earth from observatories in space. Still others are crewed spacecraft that can carry human passengers.
Until recently, only national governments could afford the very high cost of sending people into space. But private companies that use spacecraft for business purposes have begun to change the landscape of the industry.