Persi Diaconis in Quanta Magazine

Persi Diaconis shuffled and cut the deck of cards I’d brought for him, while I promised not to reveal his secrets. “I’m not going to give you the chance,” he retorted. In an empty conference room at the Joint Mathematics Meetings in San Antonio, Texas, this January, he casually tossed the cards into four piles in a seemingly random motion — yet when he checked, each pile magically had an ace on top. “Of course, it’s easy to get confused when there are a lot of cards, so let me just take four,” he said, scooping up the aces. He swiveled the four-card pile in his hands — always keeping it in the same flat plane — and sometimes the aces were faceup, sometimes facedown, even though they couldn’t possibly have flipped over.

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