The assumption that the Earths radius has not changed is based on the Equivalence Principle derived from General Relativity. The Equivalence Principle has been challenged by satellite experiments.
GPS is based on Lorentzian Relativity and not General or Special Relativity, and experiments measuring the velocity of Light have found that it changes as the direction of measurement changes (Reg Cahill, Adelaide Uni. 2006). The measurement of most physical constants are accurate to 0.001 per cent whereas the Gravitational Constant shows a much greater variation of 0.05 per cent that is no better than that achieved by Cavendish in 1789. Zavier Borg of Blaze Laboratories considers that measurements of the Gravitational Constant have been accurate and measure gravity according to the velocity of the Earth through Space at the time of measurement.
The Earth takes a year to revolve around the Sun 30 km/sec and the Solar system revolves around the centre of the Galaxy (Sagittarius “A”) in 226 Ma at 250 km/sec. If the direction of rotation of the Earth is the same as that of the Galaxy, then the velocity of the Earth is 280 km/sec, and if the Earth is moving in the opposite direction the velocity is 220 km/sec. It follows that the Earth’s velocity increases for 113 Ma and decreases during the next 113 Ma. The relationship between Velocity, Mass and the Gravity is as follows; Mass increases as Velocity increases and Gravity decreases as Velocity increases. As Gravity decreases the Earth expands for 113 Ma and then contracts for the next 113 Ma. (Borg, 2008). Velocity is currently increasing and Gravity is decreasing therefore the Earth is expanding.