How as an individual can I know if the Earth is a sphere or a flat disc? What experiment can I do that doesn't involve trusting information from a 3rd party that would prove what the geometry really is?
https://i.imgur.com/O8IpMmi.jpgThe fact that the shape of the Earth must be different from the sphere was first shown by Newton. He suggested that it has the shape of an ellipsoid and proposed the following thought experiment. It is necessary to dig two mines: from the pole to the center of the Earth and from the equator to the center of the Earth. These mines are flooded with water. If the Earth has the shape of a sphere, then the depth of the mines is the same. But the water in the equatorial shaft operates centrifugal force, while the water in the polar mine - no. Therefore, to balance the water in both mines, it is necessary that the equatorial shaft be longer.
Further development of the theory of the figure of the Earth is reflected in the works of Huygens, Cassini, Clairaux, McLauren, d'Alembert, Lagrange, Laplace, Legendre, Jacobi, Dirichlet, Poincaré and others.
