Shankar Vedantam

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Turn on the TV, and you'll find no shortage of people who claim to know what's going to happen: who's going to get picked for the NBA draft, who will win the next election, which stocks will go up or down.

These pundits and prognosticators all have an air of certainty. And why shouldn't they? We, as the audience, like to hear the world's complexity distilled into simple, pithy accounts. It doesn't help that these commentators rarely pay a serious price when their predictions don't pan out.

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President Trump has often accused the news media of not covering terrorist attacks adequately. In a speech in February he said, "Radical Islamic terrorists are determined to strike our homeland as they did on 9/11, as they did from Boston to Orlando to San Bernardino [...] It's gotten to a point where it's not even being reported."

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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.

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