In beautiful and sometimes moving prose, Hall (Invisible Frontiers, 1987) argues here that the common ground of space exploration, medical tomography, cosmology, greenhouse-effect modeling, and biotechnology is the map--and then offers a Grand Tour of the charting of these realms. It's a common story, but never better told, how the two Voyager spacecraft almost never made it off the ground because of wrangles deep within NASA; how a graduate student named Gary Flandro helped save the project when he stumbled onto the gravity-assist method of boosting trajectories, and saw how the planets lined up in the 1980's so that they could be visited in one mission. With a sort of inspired doodling, Flandro had produced a primitive navigational chart; the Voyagers plunged into the almost-unknown, and when they got there, Neptune wasn't where it was supposed to be. That's what maps are for, Hall says: To condense what we've said to be true into graphic, comprehensible form--and then, if necessary, we can change the map. Hall reflects passionately on the way exploration has generated maps that are then lost to imperial interests, or to the military (the US Navy, for example, resisted satellite mapping of the ocean floor because it feared it would make submarine routes obvious). Maps of genes, Hall says, point toward a sort of de facto eugenics, and there is precious tittle debate on the matter. And a new map of titanium deposits on the moon may only foster the sorts of abuses that lewis and Clark inadvertently brought to the West. ""Maps inspire action,"" Hall says. It may even be, in a sick world, that better maps mean more sickness. Hall quotes the philosopher Sandra Harding: ""More science in a socially regressive society...will increase the movement of the resources from the many to the few."" For the generalist striving mightily to keep up, this is a godsend.