Space probes continuously move in outer space because most of them are launched into orbits around the Earth or other planets, which require them to move in order to stay in their orbits. Some probes also travel long distances to explore other planets and moons in our solar system, so they must move to reach their destinations. Additionally, many probes take advantage of a phenomenon called gravity assist, where they use the gravitational pull of celestial bodies to help them travel faster and more efficiently.