In the 1990s, Carmeli developed a new cosmological theory called cosmological general relativity. He took Einstein's theory of general relativity and extended it into five dimensions, adding the radial velocity of galaxies expanding in the Hubble flow as the fifth dimension. This fifth dimension is known as space-velocity. He published his initial special relativistic version of the theory in 1997 in his book Cosmological Special Relativity: The Large-Scale Structure of Space, Time, and Velocity. He then developed the complete general relativistic theory called cosmological general relativity, publishing several papers on its implications over the next decade.