Aerial photographer George Steinmetz, shooting from a motorized paraglider, has created an unparalleled portrait of Rub' al-Khali, or "the Empty Quarter," the largest and most likely the hottest sand desert in the world. Although only a fraction of the size of its giant neighbor, the Sahara, the Empty Quarter's punishing terrain has rarely been captured on film, and never from such a striking perspective. Old maps, satellite images, and a dose of...