Columbus was convinced that he could reach Asia by sailing west across the Atlantic Ocean. His theory was based on the writings of ancient geographers, who believed that the Earth was much smaller than it actually is. Columbus also knew that the Portuguese had been exploring the west coast of Africa, and he believed that he could find a passage through the Atlantic to the Indian Ocean.
Columbus's primary goal was to find a new route to Asia so that he could trade for spices, gold, and other valuable goods. At the time, the Ottoman Turks controlled the traditional trade routes to Asia, and European merchants were looking for a way to bypass the Ottoman monopoly. Columbus believed that he could find a new route to Asia that would be faster and more efficient than the existing routes.