How unique is a random shuffle?
The chances that anyone has ever shuffled a pack of cards (fairly) in the same way twice in the history of the world, or ever will again, are infinitesimally small. The number of possible ways to order a pack of 52 cards is ’52!’ (“52 factorial”) which means multiplying 52 by 51 by 50… all the way down to 1. The number you get at the end is 8×10^67 (8 with 67 ‘0’s after it), essentially meaning that a randomly shuffled deck has never been seen before and will never be seen again. So next time you shuffle a deck, you should feel pretty special for holding something so unique! Try for yourself – if you make friends with every person on earth and each person shuffles one deck of cards each second, for the age of the Universe, there will be a one in a trillion, trillion, trillion chance of two decks matching.