What is an orbit?
An orbit is the circular or oval path that something follows as it moves through space. For example, the planets move in orbits around the Sun and the moons travel in orbits around the planets. To get into orbit around Earth, a spacecraft must fly out into space at a speed of at least 17,500 miles (28,163 kilometers) per hour. If a spacecraft does not reach this speed, it will fall back to Earth.