Someday not so soon Washington, D.C., may find itself about where San Francisco is now. According to a recent study, Earth's surface may be slipping slowly westward, dragged by the same lunar forces that produce tides.In a study published in the January-February issue of the Geological Society of America's journal Bulletin, Doglioni and a team of Italian and U.S. scientists argue that the westward motion is due to the tidal attraction of the moon.