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Reading this made me think of the question of whether our universe is actually a simulation.

danbruc 10y ago
The universe as a simulation is one of those ideas that sound interesting at first but are actually pretty useless the longer you think about them. There is for example also solipsism, the idea that only you exist and the rest of the world is just in your mind, or Last Thursdayism, the idea that the world came into existence last Thursday with all our minds filled with fake memories of the time before last Thursday. Those ideas put you - if you believe in them - in a spot where you can learn nothing about the world. There is nothing that allows you, even in principle, to figure out if there was a universe before last Thursday or if there is a world outside of your mind. There is not much more that would allow you to figure out whether the universe is a simulation or not. Many people talking about that idea suggest to look for indicators of limited computing resources, rounding error or whatnot. But that is totally misguided in my opinion because it presupposes that you know what at least one of the two options, the universe or a simulation of it, looks like. Who is to say that the laws of physics of the universe do not look like they are using floating numbers? Who is to say that a simulation of a universe may have to deal with limited resources? The outside world could be so foreign to us, time, space and laws of physics may not even be a thing there. Realistically the only way to distinguish between a real universe and simulation would be if the owner of the simulation told you in a pretty obvious way like with small serial numbers printed on all the electrons. I kind of understand that people don't like the idea of not even seriously considering a substantial class of ideas that are not in conflict with what we see and that could therefore actually be correct. It also seems not very satisfying to throw some probabilities at them, last Thursday, unlikely, a simulation, totally reasonable thing to do, pretty likely. In the end, if it is not falsifiable, just ignore it and have one fewer things to worry about.
- RobertoG 10y ago
  I don't think universe as a simulation is epistemologically equivalent to solipsism or this "Last Thursdayism" thing (love the name, by the way). Solipsism is meaningless. What it means to say that there is nothing outside of your mind? Surely you can't predict or control what is going to happen to your experience, so how can you say that everything is "inside" your mind? what that even means? And if you are a solipsist and wanted to predict what is going to happen next, what you should be doing? You should start to associate causation to patterns in your experience, and observe carefully that patterns. Those patterns behaviour are not decided by you, so, by definition, they are outside your mind. "Last Thursdayism" have the same problem that all the religions: OK, maybe it's true, but.. why do you choose Thursday, why not Monday? why not one minute ago? It's totally arbitrary. Simulation argument has serious experimental issues, but I would not discard it yet. Maybe we can think of something.
  - Koshkin 10y ago
    > Solipsism is meaningless Not in all contexts. A healthy dose of solipsism is a good thing - in the sense of it giving us some means of defense against what one could call "reality hypnosis", which is giving too much significance to the status quo, i.e. to what is happening (at present). Reality, too, can be "meaningless", and once that has been realized, it often turns out that changing it is not that difficult.
  - danbruc 10y ago
    I would argue that solipsism and a universe simulation are actually very close. You observe x and it might be A or B but you have no ground truth on what A or B looks like or how to distinguish them. In case of solipsism you experience a universe around you but there seems to be nothing you could use to decide whether you are experiencing an independent outside universe through your senses or whether your mind is just hallucinating this whole outside universe. In case of the universe simulation you experience a universe around you but you have no a priori knowledge what a real universe and what a simulation of a universe is supposed to look like, you seem to be stuck in more or less the same place as with solipsism. You should start to associate causation to patterns in your experience, and observe carefully that patterns. Those patterns behaviour are not decided by you, so, by definition, they are outside your mind. I think mind is probably not the right word here because it has the connotation of control, brain might be the better choice because there are things going on you can not control (ignoring whether you actually have any control to begin with). It may have not been clear from my first comment, but I was especially referring to metaphysical solipsism, denying the existence of an independent outer reality. Simulation argument has serious experimental issues, but I would not discard it yet. Maybe we can think of something. Personally I just don't think about it for the moment. There is surely the possibility that we make progress one way or another, but every time I try thinking about it, it leads nowhere. Maybe one day we discover the fundamental laws of physics, logical self-consistent and the only self-consistent laws of physics possible. With mathematical proof. Do we now know that our universe is real, it is after all nothing less than the only way it could ever have been? Or did the simulator just mess with us again? We could be using inconsistent logic all day long, writing wrong mathematical proofs and be teaching them to the next generation in our universities. But just before someone realizes the error, just after we observed the contradicting consequences of our wrong reasoning, the simulator erases the relevant memory and life goes on as if nothing happened. Unless somebody wants you to find out, you will never find out. The potential enemy in this scenario is just so powerful, you can not win.
- krohling 10y ago
  The difficulty I have with the "universe as a simulation" hypothesis is that it pre-supposes a fundamental difference between simulation and reality, which I strongly suspect is not the case. Everything we have observed about our physical reality indicates that it is 1) composed of mathematical structures and 2) it is computable. Given these characteristics it is clear that the universe we experience could be executed by any system capable of computation [Universal Raspberry Pi if you will :)]. As such, it is highly likely (almost a certainty) that whatever more foundational reality exists outside of our experience it is very different than ours and is responsible for the computational effort that generates the universe we experience. Given that any physical system is capable of computation when properly organized one could easily imagine a higher dimensional structure that did not require an intelligent being to build it that just "happens" to compute this reality. Would that be considered a "simulation"? Or is a simulation something that requires an intelligent being to build it? Obviously this turns into a bit of semantics.
- RichardCA 10y ago
  The idea that the universe is a simulation is just a different way to express the religious impulse.
  - SOMMS 10y ago
    Actually its just the opposite - most folks who invoke 'the universe is a simulation' view this as a 'scientific' way of positing a creator of the universe that is not God. Rather it is a program being run on some fantastical computer.
    - RichardCA 10y ago
      Yes, but how does this bring us any closer to answering any of the unanswered questions in Cosmology? I assert that it doesn't.

The universe as a simulation is one of those ideas that sound interesting at first but are actually pretty useless the longer you think about them. There is for example also solipsism, the idea that only you exist and the rest of the world is just in your mind, or Last Thursdayism, the idea that the world came into existence last Thursday with all our minds filled with fake memories of the time before last Thursday. Those ideas put you - if you believe in them - in a spot where you can learn nothing about the world. There is nothing that allows you, even in principle, to figure out if there was a universe before last Thursday or if there is a world outside of your mind. There is not much more that would allow you to figure out whether the universe is a simulation or not. Many people talking about that idea suggest to look for indicators of limited computing resources, rounding error or whatnot. But that is totally misguided in my opinion because it presupposes that you know what at least one of the two options, the universe or a simulation of it, looks like. Who is to say that the laws of physics of the universe do not look like they are using floating numbers? Who is to say that a simulation of a universe may have to deal with limited resources? The outside world could be so foreign to us, time, space and laws of physics may not even be a thing there. Realistically the only way to distinguish between a real universe and simulation would be if the owner of the simulation told you in a pretty obvious way like with small serial numbers printed on all the electrons. I kind of understand that people don't like the idea of not even seriously considering a substantial class of ideas that are not in conflict with what we see and that could therefore actually be correct. It also seems not very satisfying to throw some probabilities at them, last Thursday, unlikely, a simulation, totally reasonable thing to do, pretty likely. In the end, if it is not falsifiable, just ignore it and have one fewer things to worry about.

RobertoG 10y ago
I don't think universe as a simulation is epistemologically equivalent to solipsism or this "Last Thursdayism" thing (love the name, by the way). Solipsism is meaningless. What it means to say that there is nothing outside of your mind? Surely you can't predict or control what is going to happen to your experience, so how can you say that everything is "inside" your mind? what that even means? And if you are a solipsist and wanted to predict what is going to happen next, what you should be doing? You should start to associate causation to patterns in your experience, and observe carefully that patterns. Those patterns behaviour are not decided by you, so, by definition, they are outside your mind. "Last Thursdayism" have the same problem that all the religions: OK, maybe it's true, but.. why do you choose Thursday, why not Monday? why not one minute ago? It's totally arbitrary. Simulation argument has serious experimental issues, but I would not discard it yet. Maybe we can think of something.
- Koshkin 10y ago
  > Solipsism is meaningless Not in all contexts. A healthy dose of solipsism is a good thing - in the sense of it giving us some means of defense against what one could call "reality hypnosis", which is giving too much significance to the status quo, i.e. to what is happening (at present). Reality, too, can be "meaningless", and once that has been realized, it often turns out that changing it is not that difficult.
- danbruc 10y ago
  I would argue that solipsism and a universe simulation are actually very close. You observe x and it might be A or B but you have no ground truth on what A or B looks like or how to distinguish them. In case of solipsism you experience a universe around you but there seems to be nothing you could use to decide whether you are experiencing an independent outside universe through your senses or whether your mind is just hallucinating this whole outside universe. In case of the universe simulation you experience a universe around you but you have no a priori knowledge what a real universe and what a simulation of a universe is supposed to look like, you seem to be stuck in more or less the same place as with solipsism. You should start to associate causation to patterns in your experience, and observe carefully that patterns. Those patterns behaviour are not decided by you, so, by definition, they are outside your mind. I think mind is probably not the right word here because it has the connotation of control, brain might be the better choice because there are things going on you can not control (ignoring whether you actually have any control to begin with). It may have not been clear from my first comment, but I was especially referring to metaphysical solipsism, denying the existence of an independent outer reality. Simulation argument has serious experimental issues, but I would not discard it yet. Maybe we can think of something. Personally I just don't think about it for the moment. There is surely the possibility that we make progress one way or another, but every time I try thinking about it, it leads nowhere. Maybe one day we discover the fundamental laws of physics, logical self-consistent and the only self-consistent laws of physics possible. With mathematical proof. Do we now know that our universe is real, it is after all nothing less than the only way it could ever have been? Or did the simulator just mess with us again? We could be using inconsistent logic all day long, writing wrong mathematical proofs and be teaching them to the next generation in our universities. But just before someone realizes the error, just after we observed the contradicting consequences of our wrong reasoning, the simulator erases the relevant memory and life goes on as if nothing happened. Unless somebody wants you to find out, you will never find out. The potential enemy in this scenario is just so powerful, you can not win.
krohling 10y ago
The difficulty I have with the "universe as a simulation" hypothesis is that it pre-supposes a fundamental difference between simulation and reality, which I strongly suspect is not the case. Everything we have observed about our physical reality indicates that it is 1) composed of mathematical structures and 2) it is computable. Given these characteristics it is clear that the universe we experience could be executed by any system capable of computation [Universal Raspberry Pi if you will :)]. As such, it is highly likely (almost a certainty) that whatever more foundational reality exists outside of our experience it is very different than ours and is responsible for the computational effort that generates the universe we experience. Given that any physical system is capable of computation when properly organized one could easily imagine a higher dimensional structure that did not require an intelligent being to build it that just "happens" to compute this reality. Would that be considered a "simulation"? Or is a simulation something that requires an intelligent being to build it? Obviously this turns into a bit of semantics.
RichardCA 10y ago
The idea that the universe is a simulation is just a different way to express the religious impulse.
- SOMMS 10y ago
  Actually its just the opposite - most folks who invoke 'the universe is a simulation' view this as a 'scientific' way of positing a creator of the universe that is not God. Rather it is a program being run on some fantastical computer.
  - RichardCA 10y ago
    Yes, but how does this bring us any closer to answering any of the unanswered questions in Cosmology? I assert that it doesn't.