4 ms·

What's the reason for the simulation to be smaller than the simulator? Can't it just be the same but slower? This wouldn't be perceivable from the inside.

• azornathogron 3y ago
  Regardless of speed, presumably the simulator must hold at least as much state as the simulation has, and that would put some kind of bound on "size".
  • k__ 3y ago
    I see. So, the universe is assumed to be finite in either time or space?
• PeterisP 3y ago
  Quantity of information - a simulator whose state itself can be expressed in X bits can't possibly have a simulation with X+1 bits of incompressible state.
  • vidarh 3y ago
    Yes, but assuming much incompressible state is already assuming to know a lot about the nature of the simulation, ranging from size, longevity, to the extent which the structure of our perceived universe is the way it is to enable an outside simulator to take shortcuts we don't know about.
    • FartyMcFarter 3y ago
      That assumption is baked into the question being asked though. When we talk about X bits of storage it's generally accepted that this means being able to store any bit string of length X, not just compressible ones.
      • vidarh 3y ago
        The question was: > What's the reason for the simulation to be smaller than the simulator? And the answer to that is that there's no reason. There's no reason to assume the state of a simulation isn't compressible, because have no knowledge about whether or not it is, and we do have plenty of knowledge of how to create simulations that appear complex but that reduces to easily computable sequences "from the outside". The more restricted question isn't meaningful because we have no basis for assuming we can restrict ourselves to consider incompressible state, because we have no way of determining if the state is incompressible. There would be any number of sets of possible simulations that would indeed be smaller than their simulators, but given that within two similarly sized universes, you would be able to fit more simulations that are reducible, the probability that any given simulation is an approximation that allows for shortcuts ought to be higher than that it is a simulation of an irreducible set of data. So much so, that perhaps if we were able to somehow demonstrate aspects that would prove incompressibility (and I'm not convinced that is possible, or even meaningful) that might indicate that we're more likely to be in the "outer" universe. Conversely, the more compressible our universe looks, the more we might want to consider that it's an indication that we're more likely to be in a simulation.
        • PeterisP 3y ago
          I'd (obviously? perhaps not) define the "size" of the simulation as the amount of information (i.e. uncompressible state) it contains, simply because for other measures of size many trivial simulations are infinitely large while having tiny incompressible information, so these other measures of size are not useful and not used. So a more compressible i.e. more regular, simpler simulation is the smaller one, and the simulation still has to be smaller than the simulator, and we literally don't care about the compressibility or incompressibility or uncompressed size, because why would we, that's not information-theory information.
• Karellen 3y ago
  > > But because their simulations will have to run on computers that fit in our universe, presumably the simulated universes will be smaller than ours—in the sense of fewer bits and operations needed to describe them. > Can't it just be the same but slower? The number of bits needed to simulate another universe can't be larger than the number of bits we can store in this universe - there isn't enough space to store them! It's not a matter of simulation speed. Theoretically, we could simulate another universe with the same number of bits that exist in this universe, but then there wouldn't be enough bits to store you in this universe. It's the paperclip problem all over again - the simulator doesn't want to destroy you, but your existence uses up bits that the simulator needs for its own purposes.
  • WithinReason 3y ago
    many algorithms allow trading space for time
    • Karellen 3y ago
      Even if you don't run the simulation at all, you can't hold the state of a single moment of the simulation in this universe, if you need more bits to do so than are available. I don't understand how it might even be possible to get around that by "trading space for time". Can you expand on that, at all?
      • WithinReason 3y ago
        e.g. lossless compression of state space and piecewise evaluation. Better compression = less space, more time
  • b112 3y ago
    That's silly. There are whole regions of space with no actual observer. Those can be swapped to disk, or DB backend until needed. They exist, they are part of the simulation, just not actively rendered. Or they can be as sparse files in linux, null until used. I think the big concern would then be, too many active NPCs would mean too much active universe, and then an OOM issue. But of course people die, so once all the people who lived, and have memories of a thing die, then that global memory can be wiped. There are lots of methods to save space! And to have bits not rendered, or taking active ram. So over-committed sim space is a thing. Heck, maybe the project had plans for adding RAM and DB storage space, before active sim space got too big... but you know, budgets change.
• FartyMcFarter 3y ago
  > What's the reason for the simulation to be smaller than the simulator? Depends on what "smaller" means: - if "smaller" means "not able to contain as much information" then yes, the simulation has to be smaller or equal to the universe containing the simulation. You can't store N bits in N-1 bits in general (a simple counting argument can prove that). - if "smaller" refers to a concept of physical dimension, then it's possible to simulate bigger universes, as long as it's a lower resolution simulation.