Indications from space geodesy, gravimetry and seismology for slow Earth expansion at present – comment on “The Earth expansion theory and its transition from scientific hypothesis to pseudoscientific belief” by Sudiro (2014)

Abstract. In a recent article in this journal, Paolo Sudiro (2014) considered the long history of the expanding Earth theory and its recent descent into what he termed “pseudoscientific belief”. The expanding Earth theory contends that the radius of the Earth was once one-half to two-thirds of its current value, with the Earth's continents forming a continuous sialic cover over the Earth. The theory has had two main variants: slow expansion at about 0.5 mm yr⁻¹ radial increase since the time of Earth's formation and fast expansion at about 5 mm yr⁻¹ since the Triassic. Focusing on Maxlow's model, Sudiro thoroughly addresses the possibly insurmountable difficulties of the fast version, such as an improbably high density and surface gravity prior to 200 Ma. He omits, however, any discussion of the slow expansion model, which has a longer history and far fewer theoretical difficulties. Moreover, recent evidence from space geodesy, gravimetry and seismology indicates that the Earth at present may be slowly expanding at 0.1–0.4 mm yr⁻¹. It is concluded that Sudiro's obituary of the expanding Earth theory as a whole must be considered premature at this time.