John Green teaches you about the beginning of the so-called Age of Discovery. You've probably heard of Christopher Columbus, who "discovered" America in 1492, but what about Vasco da Gama? How about Zheng He? Columbus gets a bad rap from many modern historians, but it turns out he was pretty important as far as the history of the world goes. That said, he wasn't the only pioneer plying the seas in the 1400s. In Portugal, Vasco da Gama was busy integrating Europe into the Indian Ocean Trade by sailing around Africa. Chinese admiral Zheng He was also traveling far and wide in the largest wooden ships ever built. Columbus, whether portrayed as hero or villain, is usually credited as the great sailor of the 15th century, but he definitely wasn't the only contender. What better way to settle this question than with a knock-down, drag-out, no holds barred, old-fashioned battle royal? We were going to make it a cage match, but welding is EXPENSIVE. [10:36]