The Skeptical Teacher

Musings of a science teacher & skeptic in an age of woo.

How I Use a Card Trick to Teach About Science

Posted by mattusmaximus on July 20, 2010

Every year when I start a new class, I always take some time on the first day to discuss science & the scientific method. But I have my own fun & unorthodox spin on it: I first tell the “Dragon in My Garage” story, and then I go on to describe the scientific method in a very fun manner.  In short, I do a card trick…

The way I start is to ask my students if they’ve ever been to a family reunion or other gathering where someone present is doing card or magic tricks (suppose this person is “Old Uncle Harry”).  And say Uncle Harry does a particularly impressive card trick (some kind of “mind reading” or mentalism trick); what is likely to be the first response from the children present?  If you said “Do it again!” that’s a pretty good guess, but second to that I’d say the next most common response is “How did you do that?”

“How did you do that?” – contained within this question is a lot of information, folks.  First, it shows that even little kids can think critically & skeptically, because if Uncle Harry responds “It’s magic, kid (wink, wink)” even children know something’s fishy.  Second, it shows that kids want to know some kind of plausible, naturalistic solution to the supposedly “magical” phenomenon they just witnessed.

Then I play off this curiosity & natural skepticism: I ask my students what a particularly curious kid might do to figure out Uncle Harry’s trick (because really good magicians don’t reveal their tricks too easily).  Invariably, they respond that perhaps the first step would be to do some research on card tricks by looking up info on the Internet or going to the public library.  Then, once they think they’ve got an idea of the process, what’s the next step?  “Experimentation” comes the reply – in other words, the student might try to replicate just how the trick is performed by getting their own deck of cards and trying to repeat the phenomenon they observed earlier.  Depending upon their relative success or failure at replicating the trick, they may have to go through this process multiple times before coming to a meaningful conclusion as to how the trick is done.

And that, as I tell my students, is the scientific method in action.  Scientists are going through the very same investigative process as are those kids attempting to figure out Uncle Harry’s magic card trick.  They are attempting to figure out the “tricks” that nature is playing upon us all the time, and to do so they must study, research, hypothesize, and experiment in order to form a coherent & naturalistic explanation for the phenomena we observe (sorry, no “magic” allowed ;) )

And then I ask the question I’ve been waiting to ask for the entire class: “So, having said all of that, do you want to see a trick?”  The answer is always yes, and it’s always a satisfying and enjoyable trick.  This very trick I performed at the “Skepticism in the Classroom” workshop at The Amazing Meeting 8 for about 150-200 people, most of whom were teachers, and it was a real hit.  In fact, it was such a hit that I decided to write up the solution for it, and I share it with you here… enjoy… :)

I’ve put the revelation of the trick in white text, like how movie sites do the spoilers on soon-to-be-released movies.  So if you really, really, really want to know how this is done, you’ll have to select the text.

The trick is based upon something called the Si Stebbins technique of stacking a deck of cards – http://en.wikipedia.org/wiki/Si_Stebbins – here’s what to do:

1. Take a standard deck of cards and discard the Jokers & extra stuff (instructions for poker, etc).

2. Arrange the cards according to the following pattern:

8-K-3-10-2-7-9-5-Q-4-A-6-J

The mnemonic that goes with this pattern is “Eight Kings ThreaTened To Save Ninety-Five Queens For One Sick Knave” (knave means jack).  However, there’s more to the pattern…

3. The cards must also be arranged by suit, following the Si Stebbins mnemonic “CHaSeD” – Clubs, Hearts, Spades, Diamonds.  So the full arrangement would be something like this…

8 of clubs
King of hearts
3 of spades
10 of diamonds
2 of clubs
7 of hearts
9 of spades
5 of diamonds
Queen of clubs
4 of hearts
Ace of spades
6 of diamonds
Jack of clubs

And then repeat the pattern, this time starting with the 8 of hearts, and so on all the way through the deck.  Make sure that you memorize the pattern of the cards and their suits – I find the two mnemonics I gave you to work quite well, though I’m sure some people can think of their own which works better for them.  Whatever you are most comfortable with is best.

4. Now once you’ve properly stacked the deck, you must maintain the order of the cards at all costs!  This means NO shuffling of the deck AT ALL!!!  However, you can cut the deck (or have someone else do it) as many times as you like, so long as the cuts are single cuts, and the order of the cards does not change.  Once you’ve grown comfortable with handling the stacked deck, you can work on your routine – here’s how I do mine…

5.  Call up a volunteer from the class, and show them the cards.  Flipping through them in a cursory & casual manner will quickly give them the impression that the deck isn’t stacked at all (but it is).  This is the first deception – the stacking is right in front of them, but without time to really look at the cards, the student can’t catch it right away.

6.  Hand them the deck and tell them to make a single cut – show them what a single cut is beforehand to ensure they don’t mess up the deck.  Allow them to make as many single cuts as they wish (usually 3 or 4 are impressive to the audience).

7.  Shuffle the cards from one hand to the other face down, and tell your volunteer to stop at any point they wish.  When they say stop, hand them the card they stopped on (it doesn’t matter), instructing them to place it in their pocket or an envelope you have handy WITHOUT looking at the card!  This is important, because it’s the big “secret” finish at the end.  Thank them and have them either sit down or stand in front of the class holding the sealed envelope over their head for everyone to see.  This movement of the volunteer is the second deception, because as they are moving into position (and everyone’s watching them), drop the top of the deck onto the table next to you with the cards FACE UP.  The card facing up on the deck is your key card – if you don’t see this key card, you’re screwed, so make sure you get this part down!

8.  Once you know the key card, everything else is simply memorization & showmanship – the actual trick is over at this point and there are a variety of ways in which to finish off the trick.  For example, suppose the key card is the 5 of diamonds – that means, assuming the order of the cards isn’t messed up, the next card (the “secret” card) is the Queen of clubs!

9.  I like to throw in some pizazz, so I mix things up a bit.  Once my “secret” card is safely hustled away and I know the key card, I call up three other volunteers.  They each get a card from the part of the deck still in my hand – NOT the part of the deck on the table with the key card face up!  I tell each one to peek at their card and go back to their seat, whereupon I use my “awesome mental powers” to reveal the cards – really all I’m doing is following the mnemonic pattern while skipping ahead by one, since that is the “secret” card.

10.  As I identify each card in turn, the audience usually grows more and more impressed, and then comes the big finish: revealing the “secret” card that NO ONE has seen, not even the person who picked it.  Applause!!!

Some other hints/tips:

– practice this a lot, especially memorizing the pattern and being able to smoothly call out the cards as you work it into your patter (that is, your monologue during the trick)

– don’t worry about making mistakes – it will happen.  I’ve done the trick where I name 3 out of 4 cards correctly, or I get all of them right but mess up the suit on one, etc.  Chances are they’ll be mostly impressed anyway, and the more you practice it the better you’ll get at it.

– if you want to be particularly devious, right at the conclusion of the trick you can give the deck a quick shuffle to mess up the pattern & then hand it to any students who wish to examine it (yes, I admit it – I’m evil >:)

– have multiple decks prepared, especially if you have back-to-back classes.  It takes too much time to prepare a deck during a single passing period, so I just keep about 3 or 4 prepared decks in my desk drawer so that I can simply grab one during passing period and shove it in my pocket.

– have fun with the trick, and make it your own.  Once you’ve mastered the mnemonic, there’s a lot of variations of this you can do, so go crazy!

That’s it.  I hope you find this of use.  If you have any questions, please let me know.

Cheers — The Skeptical Teacher

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4 Responses to “How I Use a Card Trick to Teach About Science”

  1. Jared said

    I have a scientist type friend who is rather an expert at card tricks and even develops his own. He is so skilled he can actually shuffle a deck perfectly, exactly interleaving the cards to give the appearance of a true shuffle when it’s actually part of the “stacking” the deck phase. Even though I know that all his routines obey the laws of physics and mental math, his skill and speed, and especially fluid, natural manner and showmanship still blow me away every time. To reach that level would require significant practice and meditation, over long periods of his life. Though I do think it would be fun to help develop new tricks from an algorithmic/mathematical point of view and let him do the hard part of getting it down (I’m a programmer and I tend to think of magic tricks as problems to be debugged.)

  2. [...] How I Use a Card Trick to Teach About Science « The Skeptical Teacher [...]

  3. Bruce said

    Love it.

  4. [...] Tricks – These include some nice, off-the-cuff critical thinking exercises for your students: my “Uncle Harry” card trick, and my self-tying knot trick (the solution is here).   [...]

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