The Total Solar Eclipse of June 25, A.D. 1275 and the ΔT Value

Abstract Variations in the Earth’s rotation are intimately linked to geodynamical processes. Investigating secular change in the Earth’s rotation can provide a profound understanding of the Earth system. Currently, continuous sequence of the Earth’s variable rotation spans less than 400 years. Some researchers have employed historical records of ancient astronomical phenomena, particularly observations of solar and lunar eclipses, to study the ΔT value, which characterizes the secular change in the Earth’s rotation. This study examines the corresponding ΔT value by combining total solar eclipse observations from Chinese historical documents on June 25, A.D. 1275.