John Cleves Symmes was a popular lecturer back in the 1820's. Not only did Symmes believe that Newton got the concept of gravity totally wrong, he proposed that the Earth had a hollow interior and that one could enter this subterranean world via large holes at each of our poles. Symmes attracted a large number of supporters and his planned voyage to the North Pole was, at one point, debated and voted on by Congress. Also learn about the groundbreaking publication that Sir Edmund Halley financed, a scientist who suggested that the two moons of Mars were artificial, the relationship between gout and intelligence, and that the best cure for the hiccups may be sticking a rubber tube up your nose.  Retrosponsor: DuPont. Learn more about your ad choices. Visit megaphone.fm/adchoices