This map is part of a series of 16 animated maps showing the history of The Age of Discovery.
During the 15th century, the Portuguese did not know that the world turned on its own axis
nor did they have the scientific knowledge for understanding atmospheric circulation.
It was thanks to their wide range of experiences as navigators that they overcame the difficult sailing conditions encountered in the Atlantic Ocean.
Sailing south from Portugal along the African coast was not very difficult: they had only to sail with the trade winds. However, the voyage home was not so easy.
Once they crossed the Tropic of Cancer, the trade winds blew them further out to sea. By allowing their ships to take their course, the Portuguese discovered other regular winds from the west that gave them a faster return to Portugal than by sailing close to shore.
The discovery of this first ‘loop,’ called the “Volta”, allowed for regular journeys between Portugal and the Gulf of Guinea.
Once they had crossed the Equator, the prevailing winds made it more difficult to sail south along the coast. Once again, the Portuguese navigators discovered that they had nothing to fear by sailing further away from the coast in the opposite direction from their ultimate target, because this allowed them to pick up more favourable winds.
So, in order to travel to India and return, Vasco da Gama and his successors made a second loop further west into the Atlantic Ocean. This gave them the advantage of strong westerly winds in the South Atlantic, which increased their speed towards the Indian Ocean.
Navigation using these two loops, with the benefit of strong sea currents, continued to be the norm for all ships sailing between Europe and Asia until the introduction of steamships.