Longitude: A journey through time, astronomy, and horology

by Dava Sobel

In 1884, at the International Meridian Conference held in Washington, D.C., representatives from twenty-six countries voted to make the common practice official. They declared the Greenwich meridian the prime meridian of the world. This decision did not sit well with the French, however, who continued to recognize their own Paris Observatory meridian, a little more than two degrees east of Greenwich, as the starting line for another twenty-seven years, until 1911. (Even then, they hesitated to refer directly to Greenwich mean time, preferring the locution “Paris Mean Time, retarded by nine minutes twenty-one seconds.”)