Review Series to Celebrate Our 100th Volume Kimura's contributions on Earth polar motion studies

Kimura's discovery of z-term in the polar motion (Astron. J. 22, 107 (1902) and Astron. Nachr. 158, 233 (1902)) was recognized as an epoch-making scientific achievement for modern Japan, opening its doors to the world in 1868. Although Kimura served as the chair of the International Latitude Service during 1922-1934 and made efforts to interpret the z-term, it was unsuccessful. The physical interpretation of the z-term was given decades later by Wako (PASJ, 22, 525 (1970)). This article highlights Kimura's additional contributions that led to the interpretation by Wako.