The Flat Earth.
How can people believe the Earth is flat. All one has to do is take an overseas flight or at least get up to about 30,000 feet and the curvature of our planet can be seen with your own eyes. The whole B.O.B vs. Neil Degrasse Tyson thing going on is getting quite ridiculous. It's not needed, all that is needed is for people to do their own research, use their own mind and they'll come to the same conclusion. The Earth is NOT flat. It's an archaic, very primitive way of thinking. I can not believe that in our day of age people can believe in such a thing. Check out this quick video from the Mashable channel on YouTube, nice and to the point.