> The true circumference of the Earth is about 40,000 km (25,000 sm), a figure established by Eratosthenes in the 2nd century BC,[13] and the distance from the Canary Islands to Japan 19,600 km (12,200 sm).
No ship that was readily available in the 15th century could carry enough food and fresh water for such a journey. Most European sailors and navigators concluded, probably correctly, that sailors undertaking a westward voyage from Europe to Asia non-stop would die of thirst, scurvy or starvation long before reaching their destination.