The people posting here as spork and thinAirDesigns built a wind-powered cart that is capable of going directly downwind, faster than the wind. This has been verified by treadmill tests with miniature performed by them and confirmed by several other posters. A trial was conducted by NALSA (North American Land Sailing Association) that a cart capable of carrying a person achieved 2.7 x windspeed. The science appears to have "checked out". The poster known as humber, who tries to pass himself off as an expert in physics, but makes ridiculous, fundamental errors on nearly every post, asserts otherwise.
The poster known as humber seems to be obsessed with proving that the assertions of the builders of the DDWFTW cart are perpetrating a fraud, but he is remarkably unequipped to do so. Most of the people still participating in the discussion are doing so because humber fails in a remarkably humorous manner.