Comment by joecot

Columbus thought India was closer than it was because birds could be seen returning to the West Coast of England with twigs and leaves from somewhere. Portugal, Spain and anyone else he asked thought he was wrong because that would've required the Earth to be around 20k miles in circumference, when the Ancient Greeks had calculated it to be 24k miles in circumference (and they were very close in their calculations). Columbus turned out to be right that there was land there, he was just wrong about what the land was.