Thousand of years ago, in China & the Aegean, some thinkers knew the Earth was a sphere floating in space and orbiting the Sun. Those insights were suppressed and forgotten. Priests and rulers opted for superstition. So, in Northern Europe, Aegean, Egypt, Mid-East and Asia, folk thought the Earth was flat, covered by various types of solid `sky', with fresh waters below and salt waters surrounding.
[MOUSE-OVER for DESCRIPTION]
Later, to account for the movements of the Sun, Moon and Planets against the background of Fixed Stars, folk devised more `scientific' theories; Aristotle described how objects `want' to behave, and Ptolemy invented (invisible) crystal spheres which `wanted' to carry the Sun, Moon & Planets around the Earth, which of course was still static and fixed, in the center of the Universe.
Al-Khwarizmi and other Persian/Arab mathematicians improved the calculations but the Dark Ages degraded things, only eventually cleared up by Regiomontanus. Tycho Brahe vastly improved observations, allowing Kepler (via Copernicus's idea) to prove that Earth and the other Planets actually orbit the Sun freely, in ellipses, due to Gravity - and Galileo bravely confirmed this.