06 September 2009

Impressive magic trick using stacked deck


I saw this trick at Futility Closet and didn't believe it. Tried it a couple times and it worked. I couldn't understand how it worked, so I requested the book from the library.

Impossible? Surprising Solutions to Counterintuitive Conundrums, by Julian Havil is not really a book of magic tricks. It's about mathematics - very advanced math. You can browse it at Google Books; I consider it too complex to add to my list of recommended books. But it was worth struggling through just to retrieve this card trick.

The trick itself is impressive. The deck has to be fixed as shown in the image above. It can then be cut as many times as desired without changing the result. After cutting, the deck is shuffled - but not shuffled in the typical sense of cut and then shuffle. Before shuffling, cards are dealt from the top to form the second pile, and that second pile is then shuffled into the first one. Basically one reverses the order of half the pile, then shuffles the piles together.

After the cutting and the shuffling, the deck will still be arranged in 13 consecutive sets of four cards of four different suits. Also, alternatively, it will also be arranged in four sets of 13 cards deuce through ace (mixed-suit straights). I've tried this several times, and it has always worked. The explanation starts out something like this...

My understanding is that what it boils down to is that a single shuffle of a deck of cards (in-shuffle, out-shuffle, perfect or imperfect) is not sufficient to randomize the order of the cards. Whether the shuffle is clumsily done or professionally done, the deck will still be "ordered" to the extent that ordered groups can be dealt from it.

The nice thing about the trick is that it doesn't require any sleight-of-hand. That means you can hand the deck to someone else, and they can do the trick. This will be entertaining some of my family and friends in the winter months to come...

10 comments:

  1. Minnesotastan- I was looking at your sidebar pictures, and the dark moth you have labeled as a Royal Walnut moth is misidentified. It's a photo by Igor Siwanowicz, and the species is Eupackardia calleta

    ReplyDelete
  2. forgot the link... http://photo.net/photodb/photo?photo_id=4829626

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  3. You're absolutely correct. The mistake has been there for two years and I never noticed it.

    Fixed - with credit.

    Thanks so much.

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  4. I tried this twice without success.

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  5. Ross - You may be doing it wrong. Did you deal the cards face down to make the second pile?

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  6. Yes, I ordered the deck, so that the Ace of clubs is on top, then the 8 of hearts and so on. Then I cut the deck two times. The first attempt I dealt exactly 26 cards face down to the second pile, the other time I didn't count and did about half. Shuffled the piles together and... nothing.

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  7. Ross - the last thing to check (and this is the mistake I made before I got the book from the library) - is that when the deck is completed as you describe you don't "deal" hands as you would deal bridge hands.

    With the deck (post-cuts, post-shuffle), you deal four CONSECUTIVE cards to the SAME person and they will be four different suits. You should be able to do that 13 times.

    OR - You deal 13 CONSECUTIVE cards to the SAME person and they should be 13 different cards, 2-A (not in order).

    stan

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  8. i think we'd have to see it done, because i couldn't figure it out either.

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  9. Ricky Jay did a similar trick, but with a lot of sleights and flourishes. I'm still hunting for a demo of the Futility Closet trick.

    Meanwhile, Here's Ricky Jay.

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  10. Here's the other stacked deck mechanic that I was thinking of, but it's still not the FC trick. It's cool anyway. Click here.

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