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Imagine we had this incredibly powerful computer that can simulate our universe, and that we somehow knew the initial conditions of the big bang (or the planet earth) down to the exact detail. Fast forward the simulation we will uncover the many many secrets of the universe as we can see the cause and effect relationship established clearly (imagine it as a function with x as the time and y as the current state). Okay so what would happen if we fast forward it to the future and see, for example, yourself sitting in the same chair for the next 2 hours, but after seeing it you decide to jump to prove it wrong. I didn't know where to ask this reddit or the physics stackexhange (i was told on the sci fi platform to ask here) but this purely hypothetical situation has been bugging me for a while. The only probable solution i could see was

The simulation itself wouldn't be possible as in the quantum level particles do behave by chance so any outcome becomes equally likely (i personally thought it is determined by things we don't understand yet)

Edit 1: Okay maybe this wasn't the best SE to ask the question my bad, I'm fairly knew to SE as a whole and I'm not that regular either.

Edit 2: The point isn't simulating every atom in the universe, this would work with just Earth being simulated like I have mentioned but thanks I get it now. The problem with the infinite machines having to be simulated by the machine makes sense thank you. I think my problem was with the technical aspects of all this which now I have been referred to Determinism and its philosophy.

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    $\begingroup$ This looks like a fairly typical variation of the classic early-philosophy-class question "Could God create a mountain so heavy that s/he couldn't move it?" designed to examine faulty premises that lead to paradoxes and other assorted silly answers. Lurk a bit in Philosophy SE for tips on how to examine your premises. I don't see any Worldbuilding application to this question. $\endgroup$ – user535733 Apr 1 at 22:01
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    $\begingroup$ There are hard theoretical limits to the speed of computation. (That's because of Mr. Planck and his quantum of action.) Not to mention that it is fundamentally impossible to represent the state of every atom in the universe in a computer which exists in the same universe. (That's because you need more atoms in the computer memory than the atoms whose state you want to represent.) Minus one for complete lack of effort. $\endgroup$ – AlexP Apr 1 at 22:08
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    $\begingroup$ A universe probably can't simulate itself... there aren't enough bits in the state of the parent universe to be a functional universe and to simulate the same universe over again. Moreso, it could never simulate it even at the same rate as our own, let alone the speedup in perceived time in the simulated child universe for us to fast forward and see things near enough our own time to be of interest. Movies and other fiction that deals with these things sort of hand-waves it away or strongly implies that the child universe is a much simpler version of the real. $\endgroup$ – John O Apr 1 at 22:09
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    $\begingroup$ @cowlinator Compression doesn't work like that. Information theory's well tested. It's part of the reason you're able to post silly comments like the one you have here. That's how simulations work. You store every state. You don't get to compress noise losslessly. $\endgroup$ – John O Apr 1 at 23:22
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    $\begingroup$ I'm sorry that SciFi.SE kicked you over to here only for your question to get closed a second time. I hate seeing that happen to people, especially new users. It's not a very good first impression. $\endgroup$ – F1Krazy Apr 2 at 8:58
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Imagine we had this incredibly powerful computer that can simulate our universe, and that we somehow knew the initial conditions of the big bang (or the planet earth) down to the exact detail.

And there's your paradox! How could you possibly have a computer capable of simulation the entirety of the known universe? Think about it logically - there's no way to build such a computer capable of such a calculation, because every if every molecule of the universe is stored in the computer's memory, than you would require more matter than exists in the universe than to build it.

Not to mention that even if you did somehow build it, then it would have to take into account the fact that such a machine exists, because it's perfectly replicating the universe, and simulate that machine as well, and then the second simulation would have to create a third, and so on and so forth, you would wind up with a crashed infinite-recursion program.

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  • $\begingroup$ Imagine how much heat that computer would generate while trying to simulate all the heat in the Universe! Makes me slightly warmer just thinking about it.... $\endgroup$ – user535733 Apr 1 at 22:06
  • $\begingroup$ I believe that the answer in the second paragraph is the key to this answer. That the computer would have to compute in one step the consequences of its own use. Therefore it would know that if you saw yourself sitting in a chair that you would change your actions, and therefore not show you that, only showing you the things which you wouldn't be willing or able to prevent from happening. That's where the paradox lies (assuming you can overcome the practicality of building such a device). $\endgroup$ – Mathaddict Apr 1 at 22:36

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