Comment on What are the most mindblowing fact in mathematics?

_pheel_@lemmy.world ⁨1⁩ ⁨year⁩ ago

• Nibodhika@lemmy.world ⁨1⁩ ⁨year⁩ ago

  An extension of that is that every time you shuffle a deck of cards there’s a high probability that that particular arrangement has never been seen in the history of mankind.

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  • billiam0202@lemmy.world ⁨1⁩ ⁨year⁩ ago

    With the caveat that it’s not the first shuffle of a new deck. Since card decks come out of the factory in the same order, the probability that the first shuffle will result in an order that has been seen before is a little higher than on a deck that has already been shuffled.

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    • Steeve@lemmy.ca ⁨1⁩ ⁨year⁩ ago

      Since a deck of cards can only be shuffled a finite number of times before they get all fucked up, the probability of deck orders is probably a long tail distribution

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      • ialvoi@feddit.de ⁨1⁩ ⁨year⁩ ago

        The most efficient way is not to shuffle them but to lay them all on a table, shift them around, and stack them again in arbitrary order.

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  • Elderos@lemmings.world ⁨1⁩ ⁨year⁩ ago

    assuming a perfect mechanical shuffle, I think the odds are near zero. humans don’t shuffle perfectly though!

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    • TitanLaGrange@lemmy.world ⁨1⁩ ⁨year⁩ ago

      perfect mechanical shuffle

      What’s perfect in this context? It’s maybe a little counterintuitive because I’d think a perfect mechanical shuffle could be perfectly deterministic (assuming no mechanical failure of the device) so that it would be repeatable. Like, you would give it a seed number (about 67 digits evidently) and the mechanism would perform a series of interleaves completely determined by the seed. Then if you wanted a random order you would give the machine a true random seed (from your wall of lava lamps or whatever) and you’d get a deck with an order that is very likely to never have been seen before. And if you wanted to play a game with that particular deck order again you’d just put the same seed into the machine.

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      • Elderos@lemmings.world ⁨1⁩ ⁨year⁩ ago

        Perfect is the sense that you have perfect randomness. Like the Fisher-Yates shuffle.

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      • CodexArcanum@lemmy.world ⁨1⁩ ⁨year⁩ ago

        In order to have a machine that can “pick” any possible shuffle by index (that’s all a seed really is, a partial index into the space of random numbers), you’d need a seed 223 bits long.

        But you wouldn’t want perfect mechanical shuffles though because 8 perfect riffles will loop the deck back to it’s original order! The minor inaccuracies are what makes actual shuffling work.

        I’d probably have the machine do it all electronically and then sort the physical deck to match, not sure you could control the entropy in a reliable way with actual paper cards otherwise.

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