Sunday, May 14, 2017

A Magic Trick

I would like to do a magic trick in which an audience member has to bring an unopened can of ground coffee to the performance. The can is set down on a table out of my reach. I never come into contact with it. I then give them an unopened pack of playing cards. They are to inspect it, open it, and then inspect the cards. It is an ordinary deck of cards.

I now ask them to shuffle the cards thoroughly and set the cards down on the table beside the can of coffee. I touch neither the cards nor the can. I produce an envelope from my pocket and hand it to the audience member. I ask them to take the top card off the deck, show it to the audience, and to me, and put it in the envelope and hand the envelope back to me. I return the envelope to my pocket.

At this point I explain how the trick works. Some time in the future, I, or one of my descendants, will invent (or purchase) a time machine. I, or they, will go back in time and work out where the coffee was put into the can. At the crucial moment, before the can is sealed, they will slip the card that is now in the envelope into the can. The envelope along with the instructions for what to do when the time machine is acquired will be passed down from generation to generation.

If I am right, then, a double of the card from the future has been in the can all along. No one could have known what card would be selected during this performance. Only a visitor from the future could put the right card in the can before it was sealed and subsequently sold to the audience member.

At this point, still not having touched the can myself, I ask the audience member to open it and to dump the contents on the table. What, I wonder, would we find?


Chris Cooper said...

I know exactly what will happen. There will be a duplicate card. Because it's a magic show, duh.

But Thomas, a few questions:

* Is this a trick you've designed, or just one you'd like to see?
* If/when the duplicate card is discovered, how would you respond if challenged to put it alongside the original for comparison?
* Tracing the origin of the coffee and getting access to the packaging process sounds almost as hard as building a time machine. Will you have a plausible story to tell the audience about how you or your descendant can achieve this?


Thomas said...

Thanks for the comment, Chris! It's only an effect I've imagined. (I'm not a magician.) I'm pretty sure that it's impossible to do as I've described it. Since I handle neither the cards nor the can, there's no way to get card into the can on the stage. Unless the can and the audience member have been planted (which would be a lame way to do the trick), it can't be done, as far as I can tell.

It would actually require time travel. I'm guessing that, the fictional "rules" of time travel notwithstanding, if it is possible, it can land you anytime and anywhere, which should make it easy to trace the can back to it's point of origin. Thinking about it now, maybe I should pick an a package with a uniquely identifying serial number.

I left the ending open because I think it would be fun just to do the trick and rely on the invention of time travel sometime in the future. So it's really just a thought experiment to prove that time travel is definitely impossible. You are making a target and giving the universe forever to hit it. And still it doesn't happen.

PS. There's no problem with the existence of the original. The narrative requires that it is still in the envelope.

Chris Cooper said...

I'm worried that failure of the duplicate card to appear won't prove your point. Future time-travellers will need a powerful incentive to reveal themselves. After all, something's apparently restraining them from doing so: doubtless some future multiversal legislation designed to stop reckless interference with the fabric of space-time - you know the sort of thing. So they need a countervailing threat of some kind.

Are you planning to have kids in the near future? If not, recruit someone who is. All they have to do is build some foolproof, failsafe apparatus to commit suicide - say, in a week's time, unless a traveller from the future stops them. The potential suicide simply writes down their plan and arranges to have it passed down the family line, starting with any kids they have *after that date*, into the indefinite future. Descendants who have access to a time machine will realize it's up to them to guarantee their own existence by going back and stopping great-great-granddaddy's suicide. If they don't, they'll start becoming transparent and finally fading out altogether, as in Back To The Future.

Or something.

Thomas said...

I like that plot! And it could be turned into an amazing guillotine stage performance! Much more dramatic than my little car-in-a-sealed-can trick.