When I bought this book, I didn't realize how complementary to my Pick for Marchit would turn out to be. I thought that Poincare's "maps" referred to were his geometric depictions of deterministic chaotic systems, which he was first to discover, and the book was going to be largely about mathematics. Instead, it turned out to a history of the very concrete problems of synchronizing clocks for the benefit of both science and commerce (especially railroads) around the turn of the 20th century. It included some political (as well as practical) considerations, such as the location of the Prime Meridian and whether days should start at noon or midnight. Peter Galison does an excellent job of showing that Einstein's idea that motion and time are inherently relativistic did not spring full-blown from the mind of one man, but was the culmination of concepts that many - especially Poincare, but also Lorentz and Mach, were wrestling with. This very readable book is also a resource for those who wish to dig deeper, with about 30 pages of notes and 15 pages of references. I did not realize until I read this book, that Lorentz' formula predicting that objects in motion are contracted in the direction the are moving, predated Einstein's special relativity.