‘To look at ourselves from afar,’ Julian Barnes wrote in Levels of Life, ‘to make the subjective suddenly objective: this gives us a psychic shock.’ The context of Barnes’s remark is the 100-year span in which aerial photography evolved from its 19th-century birth in the wicker cradle of a gas balloon to the miraculous moment in 1968 when an astronaut aboard Apollo 8 took the photograph known as ‘Earthrise’: the darling blue ball of planet Earth rising up over the arid, inhospitable surface of the moon.