• hakase ( hakase@lemmy.zip ) 
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          9 months ago

          Sure, the total number of passengers does, but do any of the original passengers stay on the entire time as new passengers cycle on and off?

          • yuri ( yuri@pawb.social ) 
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            9 months ago

            i think that can’t really be answered bc there’s no hard rules on who specifically gets off.

            if it’s first-on, first-off then all the original riders would cycle out in as little as 2 cycles. but if it’s first-on, LAST-off then at least 1 person from the original bunch would always be on the train.

            if it’s random, who knows! someone who took probability and statistics can work that one out lmao

  • If the trolley is moving at light speed by the time it hits the station, it is impossible for anyone to get on or off because—from the trolley’s perspective—no time passes between stops. Ergo, the number of passengers on it must be the same every stop.

    If the initial number of passengers is odd or a non-zero integer, this inability to board/unboard would contradict the rules.

    Thus, in order to satisfy all the conditions, the initial number of people on the trolley must be 0. As an even number it will be subject to halving, but 0/2=0, so the rules are satisfied.

    Hence, pulling the lever is the optimal solution as 0 people will die. QED.

  • Redjard ( Redjard@lemmy.dbzer0.com ) 
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    9 months ago

    It only accelerates to light speed, therefore it will need infinite time to complete the loops. Thus the risk is not the killing but getting stuck.

    If the conjecture holds, naturally there is a small cycle so people can get on and off and use the train as a form of teleporting to the future.

    If there are different loops, then still people can take turns.

    Even if there are values that diverge, if it can be shown that at least one event of division occurs with a certain average frequency in the infinite divergence, then at any such point all previous guests can exit and the train can be ridden for one such span.

    Only if there are no cases of division and endless steps of 3n+1 in the limit, would people be trapped on the train at no subjective time passing, and in essence time travel into the infinitely far future where they are killed.

  • Honytawk ( Honytawk@feddit.nl ) 
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    9 months ago

    This one is easy.

    Either you kill 5 people, or you pull the lever and kill none. Because an infinite loop never ends.

    All the rest is just fluff with no bearing on the question.

  • xxd ( xxd@discuss.tchncs.de ) 
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    9 months ago

    There are two super interesting problems in here.

    One is: would you bet human lives on a conjecture being true? The collatz conjecture does hold for every number we have tried, but there have been conjectures that were disproven with a very large counterexample. You could kill countless humans if wrong, so even if you think the chance of a counterexample is low, is it low enough to outweigh that potentially very hight value counterexample?

    The second one is: Let’s say the collatz conjecture holds, and the number of passsengers just loops 4 -> 2 -> 1 -> 4 -> 2 -> 1 eventually. What is the ‘final’ number, when the trolley is done with the infinite loops? It can’t be 1, because that is always followed by a 4. And it can’t be 4 because it’s always followed by 2 and so on. But it has to be one of those, because any other number is not possible. It reminds me of the Vsauce Video Supertasks, which comes to the conclusion that we can’t know the answer to these type of questions.

    So in conclusion, flipping the switch will either give you an arbitrarily large number of deaths, or an unknown number of deaths. Fun!

      • xxd ( xxd@discuss.tchncs.de ) 
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        9 months ago

        It really depends. For example, if you walk 1m, then 0.5m, then 0.25m and continue infinitely, then “after infinity” you will have walked exactly 2m. This is the classic ‘Achilles and turtle’ example and works fine if the value converges. It’s just mathematics.

        There is only a problem if the value diverges. Imagine the step example, but on even steps, you raise a blue flag, and on odd steps you raise a red flag. Now the question what flag is raised “after infinity” is impossible to answer. It clearly should be either red or blue, but it also can’t really be either, because that would mean infinity is either even or odd, which makes no sense.

    • wizardbeard ( wizardbeard@lemmy.dbzer0.com ) 
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      9 months ago

      Flipping the switch gives you 1, 2, or 4 deaths. It will always end up looping those three numbers, so after an infinite amount of time it has to be one of those three options.

      All three of those options are less than 5, and they occur after an infinite amount of time instead of (relatively speaking) immediately.

      From both a pure numbers perspective and a theoretical minimizing or delaying harm perspective, pulling the lever is the right move.

      • xxd ( xxd@discuss.tchncs.de ) 
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        9 months ago

        You’re assuming the collatz conjecture holds, which is unknown.

        But even if it does hold, you do understand the second problem, right? 1 can not possibly be the outcome, because whenever there is a 1 in that infinite loop, it is followed by a 4. And if 1 is the outcome, then it wasn’t done infinitely, because otherwise there must have been a 4 afterwards. The same argument holds for 4 and 2 as well. So we’re stuck in the reality that it would have to be one of those numbers, but it also can’t really be one of those numbers. It’s paradoxical.

  • Wirlocke ( Wirlocke@lemmy.blahaj.zone ) 
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    9 months ago

    No matter what wouldn’t this grow to infinite passengers? Is that supposed to be the point?

    Because any even number is going to halve itself down to 1, which is odd an odd number, then double plus one will always make another odd number so it would grow to infinity.

    Edit: Misread the problem, read replies for explanations

  • pruwyben ( pruwybn@discuss.tchncs.de ) 
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    9 months ago

    I think everyone inside would die when it accelerated to light speed. And since most numbers are larger than 5 I’d say don’t pull the lever. The only question is what happens to the people inside the trolley if you don’t pull the lever?

    • wonderingwanderer ( wonderingwanderer@sopuli.xyz ) Banned from community
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      9 months ago

      It’ll always reduce to a cycle of 4→2→1→4→2→1 etc.

      Which means people can get on and off so no one is trapped, and since they don’t die until after an infinite number of stops it means no one will get killed

  • how_we_burned ( how_we_burned@lemmy.zip ) 
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    9 months ago

    Wouldn’t the tram require all the energy in the universe to accelerate to light speed whilst the object would create a massive wave of radiation and shock waves thus destroying everything in its path?

    Thus no more station and peoples on the rail meaning no one can get on or off.