xkcd #3125: Snake-in-the-Box Problem

Title text:

Chemistry grad students have been spotted trying to lure campus squirrels into laundry hampers in the hope that it sparks inspiration.

Transcript:

Transcript will show once it’s been added to explainxkcd.com

Source: https://xkcd.com/3125/

explainxkcd for #3125

Chemistry grad students have been spotted trying to lure campus squirrels into laundry hampers in the hope that it sparks inspiration.

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[–] 42 points 1 year ago (5 children)

What about goats in circular pens? A goat is tied to the fence of a circular pen. How long does the rope need to be so that the goat can reach exactly half of the pen's area? What sounds like a high school math problem was eventually solved in 2020 via complex analysis.

Here's the answer:

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  • [–] 15 points 1 year ago (2 children)

    I feel like the answer should be much simpler than that equation salad.

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  • [–] 12 points 1 year ago

    The difficulty is that the goat is tied to the fence.

    It would be a lot easier to put a pole in the center of the circle.

    The length of the rope would then be 0.5 x sqr(2) x fence radius.

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  • [–] 32 points 1 year ago (2 children)

    Randall forgot psychology, which has involved a ton of putting animals in boxes...

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  • [–] 11 points 1 year ago

    I guess a key thought experiment doesn’t qualify as a reason, and also we are supposed to conveniently forget about putting spherical cows in a vacuum just because.

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  • [–] 8 points 1 year ago* (last edited 1 year ago) (8 children)

    Either I'm misunderstanding the problem or a length of 8 is possible.

    Edit: found my mistake, far left edge has two non-consecutive segments on adjacent corners. Leaving this up in case anyone else tries for a better score.

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  • [–] 7 points 1 year ago*

    We have one for combinatorics: Ask Fibonacci about his rabbits.

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  • [–] 5 points 1 year ago

    There really is an xkcd for everything.

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  • [–] 5 points 1 year ago

    I'm still trying to fill that hotel with infinite monkeys

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  • [–] 5 points 1 year ago (5 children)

    I'd expect something around ~200 for n=9 and ~400 for n=10, but I imagine this is too big to be brute forced by raw computing

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  • [–] 2 points 1 year ago (1 child)

    I'd think that it's not "too much to be brute forced", but probably no one has thrown enough resources at that recently

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  • [–] 4 points 1 year ago

    My combinatorics professor used gnomes!

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  • [–] 4 points 1 year ago (1 child)

    In biology it’s less of a “thought” experiment

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  • [–] 1 point 1 year ago* (last edited 1 year ago) (2 children)

    [This comment has been deleted by an automated system]

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  • [–] 5 points 1 year ago

    Took me a while to follow that too! The three examples of fails at the top each show instances where there are non-consecutive parts of the snake on adjacent corners - it's the lines highlighted in red.

    Basically no two parts of the snake that aren't directly joined to each other in the snake are allowed to be on corners which are only a line apart.

    I think.

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  • [–] 2 points 1 year ago*

    Any two coils that are not directly connected. For example, suppose we number from the head, coil 1, 2, 3, 4. Then pairs that are not directly connected are: (1, 3), (1, 4), (2, 4). The endpoints of these pairs of segments cannot be connected by an edge of the cube.

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