to keep sending a signal into the world, trusting that somewhere, sometime, there will be someone capable of receiving it.… Every morning at six, Aki walked along the same narrow road to the coastal research center. The road was unremarkable. A convenience store stood at one end, a drainage canal at the other, and between them ran a strip of neglected land where weeds grew through cracks in the pavement. Nobody had designed it as a garden. Nobody watered it. Nobody maintained it. Yet in early summer, a small yellow flower appeared there. Aki did not know its name at first. She stopped one morning and took a photograph with her phone. The flower was not particularly large. Its petals were slightly uneven, and one leaf had been damaged by something that had crawled across it during the night. Still, Aki thought it was beautiful. She uploaded the photograph to a plant-identification application. Within seconds, the application suggested several possibilities,...