Afficionados of hot-air ballooning flock to Albuquerque, New Mexico, for an experience that’s not possible in most other parts of the world. From a launch site to the north of the city, balloon pilots fly south across the metropolitan area. Then, astonishingly, they turn around and return to the starting point. To learn about the geographic and atmospheric conditions that enable such a feat, turn to the Quick Study on page 54 . (Image by Mark Newman/Rainbow/RGB Ventures/SuperStock/Alamy Stock Photo.)