In a heliocentric model the Sun, not the Earth, is in the center and all other objects including the Earth orbit the Sun. In this model the Earth is moving in two ways. It revolves arround the Sun and it also rotates on an axis.
According to Pythagoras theorem the diagonal length of a square with each side measuring one unit would be square root of two.
The assumption that square root of two could be expressed as a ratio of two integers deduces a contradiction.