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I think this is a much harder problem than you make it seem. A tree no one is looking at, sure, you can take shortcuts, but if I'm not looking at my computer, i

I think this is a much harder problem than you make it seem. A tree no one is looking at, sure, you can take shortcuts, but if I'm not looking at my computer, it still has to run my programs and you cannot approximate its answers. If I, a being in your simulation, was to hypothetically build a simulator of the kind that you use to simulate me, it is obvious that it could not work: if it could approximate the running of itself to a sufficient level of detail, it already would be doing that. So the question is: what else wouldn't work? The closer the technology I build gets to physical optimality, the more it will act as a bottleneck in the simulation. If I build a physically optimal circuit to perform any useful calculation that I can verify, for example, the simulation speed will have to drop below one second per second. What this means is that modern times are probably too expensive to simulate, so you would likely stick to simulating medieval times (we may also have to eschew simulating the brains themselves, if it turns out the biological ones are too close to optimality for what they do). At least that's what we would have to do. You can imagine that the universe that simulates us works differently, but hypothesizing a world that has different laws of physics doesn't really help us to understand ours. It's fun to think about, but nothing more than that.

rendall 3y ago
> You can imagine that the universe that simulates us works differently Moreover, you have to make that assumption, or the equivalent assumption that computers can become so advanced that we are the equivalent to their middle ages. My objection to the simulation hypothesis is that, if one must make those assumptions to make it work, why precisely and only those assumptions that make our Universe a "simulation": that we are here because of the intentions of creatures, that "simulation" applies to whatever it is they're doing, that the creatures are human enough to find simulating us useful.
- breuleux 3y ago
  The probabilistic simulation argument ("we are probably in a simulation") actually requires you to reject that assumption (edit: not reject outright, but you need the assumption that observers of the real and simulated universes cannot tell the difference, so no 6D stuff). People who raise the point that the universe doing the simulation could be very different from ours don't understand what is required for the argument to work. The simulation argument is that if you observe a universe X, and you work out that a real universe X will simulate two universes just like it, then someone who observes that they are in a universe that looks like X is probably in a simulation. That is because for every real X you have two simulated X: even if you assume that there exists a truly real and physical X, it still follows that most observers of X are simulated. I don't think our universe will simulate more observers than there are real observers, but at least this is something we can meaningfully argue about. If, in contrast, you say that there is a universe Y, and Y simulates X, there are no interesting conclusions you can draw from that. You are comparing "X is real" to "Y is real, and Y simulates X", but there's no reason to think Y is more likely to be real than X. It's possible, but a lot of things are possible. It's not interesting.
  - rendall 3y ago
    If I understand the argument, it seems that case is even more unlikely. Not only must one assume that the composition of our Universe just happens to be a super version of one of our own latest technological innovations, one must also take on faith that a computer could one day spin off multiple instantiations of entire Universes that are indistinguishable from the Universe the computer itself is within. Personally, I don't find the argument compelling because of its unexamined, embedded assumptions. What is meant by computer? What is meant by a simulation? What is meant by Universe? What is an observer? How is it falsifiable? By the time these terms are pinned down, the argument disappears in ontological haze.
    - breuleux 3y ago
      It's the kind of argument people conjure when they think, not consciously, but subconsciously, that computers are magic. I've been there. You view the world as simple and slow, and computers as this complex and magical technology that is getting twice as fast every five years. You don't properly understand the limits of physics, so you extrapolate the progress of technology well past them until you believe it will be possible for a computer the size of a fist to simulate an entire planet. In a nutshell, some people believe in Moore's law more than they believe in the laws of physics: the failure of the former would surprise them more than the failure of the latter. > What is meant by computer? What is meant by a simulation? These are especially interesting questions once you think about the low hanging fruits for optimizing a world simulator. If you want to simulate the interaction between two systems as efficiently as possible, you want the states for these two systems to be located as closely together as possible, in order to minimize communication overhead. And if you are trying to simulate a 3D universe, and calculate what would minimize internal communication delays, the best computer architecture to do this is, well... it's going to be isomorphic to what you are simulating. That is to say, if you travel around the planet in the most efficient computer simulator, an external observer would probably see a bunch of photons and electrons travelling in a physical circle inside the simulator. And the ensemble of transistors that simulate you at any given moment would probably physically look like you. When your simulator physically looks like the universe it is simulating, is it still a simulation? Or is it in the middle of some spectrum between real and simulated? Ontological haze indeed.

rendall 3y ago

> You can imagine that the universe that simulates us works differently Moreover, you have to make that assumption, or the equivalent assumption that computers can become so advanced that we are the equivalent to their middle ages. My objection to the simulation hypothesis is that, if one must make those assumptions to make it work, why precisely and only those assumptions that make our Universe a "simulation": that we are here because of the intentions of creatures, that "simulation" applies to whatever it is they're doing, that the creatures are human enough to find simulating us useful.

breuleux 3y ago
The probabilistic simulation argument ("we are probably in a simulation") actually requires you to reject that assumption (edit: not reject outright, but you need the assumption that observers of the real and simulated universes cannot tell the difference, so no 6D stuff). People who raise the point that the universe doing the simulation could be very different from ours don't understand what is required for the argument to work. The simulation argument is that if you observe a universe X, and you work out that a real universe X will simulate two universes just like it, then someone who observes that they are in a universe that looks like X is probably in a simulation. That is because for every real X you have two simulated X: even if you assume that there exists a truly real and physical X, it still follows that most observers of X are simulated. I don't think our universe will simulate more observers than there are real observers, but at least this is something we can meaningfully argue about. If, in contrast, you say that there is a universe Y, and Y simulates X, there are no interesting conclusions you can draw from that. You are comparing "X is real" to "Y is real, and Y simulates X", but there's no reason to think Y is more likely to be real than X. It's possible, but a lot of things are possible. It's not interesting.
- rendall 3y ago
  If I understand the argument, it seems that case is even more unlikely. Not only must one assume that the composition of our Universe just happens to be a super version of one of our own latest technological innovations, one must also take on faith that a computer could one day spin off multiple instantiations of entire Universes that are indistinguishable from the Universe the computer itself is within. Personally, I don't find the argument compelling because of its unexamined, embedded assumptions. What is meant by computer? What is meant by a simulation? What is meant by Universe? What is an observer? How is it falsifiable? By the time these terms are pinned down, the argument disappears in ontological haze.
  - breuleux 3y ago
    It's the kind of argument people conjure when they think, not consciously, but subconsciously, that computers are magic. I've been there. You view the world as simple and slow, and computers as this complex and magical technology that is getting twice as fast every five years. You don't properly understand the limits of physics, so you extrapolate the progress of technology well past them until you believe it will be possible for a computer the size of a fist to simulate an entire planet. In a nutshell, some people believe in Moore's law more than they believe in the laws of physics: the failure of the former would surprise them more than the failure of the latter. > What is meant by computer? What is meant by a simulation? These are especially interesting questions once you think about the low hanging fruits for optimizing a world simulator. If you want to simulate the interaction between two systems as efficiently as possible, you want the states for these two systems to be located as closely together as possible, in order to minimize communication overhead. And if you are trying to simulate a 3D universe, and calculate what would minimize internal communication delays, the best computer architecture to do this is, well... it's going to be isomorphic to what you are simulating. That is to say, if you travel around the planet in the most efficient computer simulator, an external observer would probably see a bunch of photons and electrons travelling in a physical circle inside the simulator. And the ensemble of transistors that simulate you at any given moment would probably physically look like you. When your simulator physically looks like the universe it is simulating, is it still a simulation? Or is it in the middle of some spectrum between real and simulated? Ontological haze indeed.