An Easy-Sounding Problem Yields Numbers Too Big for Our Universe

It’s not often that 5-year-olds can grasp questions at the frontiers of computer science, but it can happen. Suppose, for instance, that a kindergartner named Alice has two apples, but she prefers oranges. Fortunately, her classmates have developed a healthy fruit-trading system with strictly enforced exchange rates: Give up an apple, say, and you can get a banana. Can Alice execute a series of...


文 » A