I suggest reading about Erastothenes and his elegant experiment that conclusively proved the spherical shape of the earth in 200 BCE. Go look at a pendulum in action to experience the rotation of earth. No sane man has ever thought the earth as flat for the past 3000 years. The concept or term "flat earth" was coined by the mediocre American writer Washington Irving to mock the Catholic church in one of his ludicrous fictions.