In the early days of seafaring, sailors operated solely through a process known as "piloting", in which the position and course of the ship was determined by referring to geographical landmarks. The need to stay in view of the shore severely limited the extent of sea voyages. Through experience, sailors learned to applu the science of astronomy to their profession, noting the positions and movement of particular stars. They realized that even when the shore was out of sight, they could steer by certain reliable stars. This crude, yet practical application of astronomy allowed the adventurous to sail into the unknown with a reasonable chance of finding their way. As a result, ship building technology quickly improved, producing larger, more stable ships designed for longer voyages.