What if . . . Thanks to a science fair project gone bonkers, you just spent a few days teaching Leonardo da Vinci about gravity and relativity. . . You escaped a bonfire of the vanities-only to come home and find things are not what they were before. . . Now that you know the secrets of time travel, you've set your sights (and your new time machine app) to a new destination and a brilliant person of interest: a science and math genius, first to translate...