People knew the world was round long before anyone attempted to prove it by sailing around it instead of just illustrating it with math. Knowing isn't the same as proving it in the real world. Also, the knowledge the world is round doesn't establish that there's a continuous body of water encircling the entire globe. We had to get out there and see what was beyond the known.

I can't even imagine how exciting that must have been, to see parts of the world that no human had ever seen before. I was just thinking last night that I miss not knowing things about the world. We have all the information about the entire earth at our fingertips now. When I was a kid there was still a lot of mystery left, but the information age destroyed that.