Nearly a century ago, Edgar Buckingham published a seminal work on the movement of soil moisture that is part of the foundation of modern soil physics. It also constitutes a pioneering contribution in the study of multiphase flow in porous media. A physicist, Buckingham took on an earth science issue of importance to society and produced superb basic science as a byproduct. Buckingham impresses us with his ability to combine experiment and theory and his capacity to intuitively explain difficult ideas to a wide audience. Science progresses both by gradual accretion of knowledge and by sudden influx of ideas. Buckingham's contribution belongs in the latter category. After a brief, four-year rendezvous with soil science, he went on to pursue a long and distinguished career in physics with the National Bureau of Standards. This paper is an appreciation of Buckingham's contribution on soil moisture in the context of contemporary developments in diffusion theory and the rapid growth of science in America at the turn of the 20th century.