A riffle-shuffled deck gives up on order around shuffle seven.

The part that checks out ↘

It really happened.

In 1992, mathematicians Dave Bayer and Persi Diaconis worked out how quickly riffle shuffling mixes a 52-card deck. Order does not fade gradually. It survives the first few shuffles remarkably well, then collapses around the seventh — the point at which the deck becomes reasonably close to random. Extra shuffles after that change very little.

Randomness feels like something that accumulates. Here it arrives almost all at once — order holds, holds, and then is gone.