Magic. That's what it feels like when you bump into your childhood friend on the first day of college ... or meet someone at a party in Paris, only to discover she lives in your dad's childhood home in Poughkeepsie, N.Y. But mathematician Joseph Mazur says these coincidences are not as extraordinary as we might think. "People think that their address book is essentially the people they know, and it turns out any address book is about one percent of the people they know in some way," Mazur explains. In other words, the odds of bumping into someone you know are greater than you might think, because you know many more people than you realize. Understanding these odds can help us wrap our heads around stories of people who seem inexplicably fortunate. People like Joan Ginther, who won the lottery not once, not twice, but four times. What are the odds? "The odds are about 18 septillion to one against it happening," Mazur says. A septillion is 1 followed by 24 zeros. But if you reframe the
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