First, to get some myths out of the way. Europeans knew that the earth was round. They also had a fairly accurate estimate that the circumference of the earth was some 24,000 miles.

The first Europeans to find a way to sail to India and its spices were the Portuguese, in 1488, when Bartolomeu Dias rounded the Cape of Good Hope sailing to the east. Though Portugal would only later reach India on the voyage of Vasco de Gama of 1497-1499, it was apparent that Portugal had already won the race in reaching India by sea and that Lisbon would become the next center of the European spice trade after Venice.

Sailing to the west of Europe was considered dangerous, especially because European ships could only sustain trips of some 10,000 miles, while Asia was considered to be 10,000 to 12,000 away. Columbus, however, thought the earth was much smaller. He thought the earth’s circumference was not 24,000 miles, but only 18,000. No doubt this was why his proposal to sail west to Asia was rejected by the courts of Portugal, France, and England.

When Columbus finally turned to Spain for sponsorship of his voyage, Portugal had already found a way to Asia. So, this might have influenced the Catholic Monarchs’ agreement to sponsor the trip: Why not? They had little to lose.

It was quickly realized by Europeans that Columbus had not arrived in India, but rather had landed at a new land. This realization is apparent in the Treaty of Tordesillas of 1494, just two years after Columbus landed. So, it took little time at all that one could reach Asia either sailing to the east or by sailing to the west.

The first person to actually sail to Asia from the Americas was Magellan, in his 1519–1522 voyage.