The Milne universe is the empty , FLRW model with scale factor proportional to proper time. It is a hyperbolic-coordinate description of the interior of a future light cone in Minkowski spacetime.
Articles by others on the same topic
The Milne model is a cosmological model that describes a uniform, isotropic universe that is expanding. It was proposed by the British astrophysicist Edward Arthur Milne in the 1930s. The model is significant in the field of cosmology, particularly for its attempt to explain the universe's expansion without relying on the concepts of gravitational attraction that are central to Einstein's General Theory of Relativity.