Comment on He's gonna be walking for a little bit

• teft@lemmy.world ⁨1⁩ ⁨month⁩ ago

  www.youtube.com/watch?v=3P6DWAwwViU

  Here is a Numberphile video that describes how large a number we are talking.

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  • bdonvr@thelemmy.club ⁨1⁩ ⁨month⁩ ago

    Thanks, I get it now!

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• Thedogdrinkscoffee@lemmy.ca ⁨1⁩ ⁨month⁩ ago

  I am one of them. I still can’t get past the Hotel paradox. To me an infinite number of guests cancels out an infinite number of rooms.

  Infinite guests = infinite rooms Infinity + n = infinity To say the bus of unbound guests could just move into infinite rooms seems to give a property of rooms without limit that is not shared with the original infinite guests.

  The original premize states the hotel is full. Because the only thing that matches infinite rooms are infinite guests.

  Apparently I am very stupid. My sister was right all along.

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  • ftbd@feddit.org ⁨1⁩ ⁨month⁩ ago

    There are different “kinds” of infinity. For example, there is an infinite amount of natural numbers, and there is an infinite amount of real numbers. Still, natural numbers only make up a tiny part of real numbers, so while both are infinite, the set of real numbers is bigger. Hilbert’s Hotel is an analogy meant to convey how to deal with these different notions of infinity.

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    • Klear@sh.itjust.works ⁨1⁩ ⁨month⁩ ago

      Not really. The guests move to a room with double the number, freeing up an infinite number of rooms.

      So the change is from natural numbers to even numbers, freeing up odd numbers. Those infinities are the same, but you can still do this because infinities are weird.

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  • bdonvr@thelemmy.club ⁨1⁩ ⁨month⁩ ago

    Infinite hotel has infinity guests. You have all the guests move down 10 rooms. Rooms 1-10 are now free. Zero to Infinity and 11 to infinity are equally infinity, since numbers extend into infinity.

    In the same manner if you have one sit of infinite guests occupy all the even numbered rooms, you will still have an infinite number of rooms open, because the set of all odd (and even) numbers extends infinitely. You could have the first set of infinite guests take each hundredth room (100, 200, 300, etc), then the next set take 99, 199, 299, etc. in that way you could fit 100 sets of infinite guests.

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    • Thedogdrinkscoffee@lemmy.ca ⁨1⁩ ⁨month⁩ ago

      What doesn’t make sense to me is infinite rooms and infinite guests and is full. You ask everyone to move down 10 rooms, why is 1-10 now free? You had infinite guests too, wouldn’t more filled rooms appear?

      Or Is infinite only infinite (undefined) on the upper end, but defined on the lower? E.g. 1.

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      • bdonvr@thelemmy.club ⁨1⁩ ⁨month⁩ ago

        You can define the start of an infinite series, just not the end. (Except as ∞ or -∞). You could also have an infinite set that extends both ways.

        0 to ∞ contains an infinite amount of numbers. But so does 11 to ∞.

        More filled rooms do not “appear”, the rooms just go on without end. These is no “last” guest who moves into some previously unoccupied room. It’s just… endless. Infinite.

        It really only makes sense in abstract. Our minds aren’t built to deal with infinity.

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  • Semjaza@lemmynsfw.com ⁨1⁩ ⁨month⁩ ago

    So, some infinities are bigger than others.

    How many numbers are there? An infinite number.

    How many even numbers are there? An infinite amount, but half the size of the first infinity.

    This is how there are empty rooms in the infinitely large hotel with infinite guests.

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    • LwL@lemmy.world ⁨1⁩ ⁨month⁩ ago

      Funnily enough that’s an example of two infinities that mathematically have the same cardinality (which is very often conflated with size since for general mathematical purposes that’s what it is) since you can map a bijection (i.e. every number in the first set has one and only one mapping in the second) between the two (and it’s as simple as f(n)=2n).

      And intuitively that makes about as much (or rather, little) sense as the infinite hotel.

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      • Semjaza@lemmynsfw.com ⁨1⁩ ⁨month⁩ ago

        OK, thanks for the extra info. When I see that function it kinda makes sense but stops if I think about it too much.

        Would even numbers and prime numbers have different cardinality?

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    • Thedogdrinkscoffee@lemmy.ca ⁨1⁩ ⁨month⁩ ago

      Half of infinity is still infinity, but smaller?

      Can you hand me that spatula. I need to scrape my brains off the walls.

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