I don't understand how someone could believe it. The Earth being flat is a secret that every space agency, institute of higher learning, educational system, government, literally any company involved in anything related to aeronautics, compass producer, cartographer, astronomer, or anybody that knows how to use a telescope would have to keep. I've even heard the reasoning that The Manhattan Project involved 130,000 people, and no information was leaked. Which even if that was true, is still terrible reasoning.
