Page "Hollow Earth" Paragraph 41

which defines a coordinate transformation such that the interior of the Earth becomes " exterior " and the exterior becomes " interior ".

( For example, in spherical coordinates, let radius r go to R² / r where R is the Earth's radius.

) The transformation entails corresponding changes to the forms of physical laws.

This is not a hypothesis but an illustration of the fact that any description of the physical world can be equivalently expressed in more than one way.