All of us living things have to find out where we are and where we are going. Earth’s first cell had only a dim chemical feel for its immediate liquid surroundings. But it multiplied fruitfully, and the animals that flowed from its lineages are able to navigate whole seas and continents. Birds have developed an inner sense of the Earth that allows them to traverse entire hemispheres. By animal standards, these are impressive feats of orientation, but they are crude compared with those that human beings have achieved. Our most sublime such effort is a global collaboration to build, over the course of decades, a network of more than 30 radio observatories that work together to situate our planet within a mind-bending volume of space. These radio dishes span the planet, top to bottom. The northernmost one is wedged into an ice field in Svalbard, Norway. On-site staff are required to carry rifles in case of polar-bear attacks. Six other dishes are strung across the islands of the Japanese archipelago. The United States has several …