10 ms·

This should be a sobering account to the remarkably popular theory, that given enough time we should inevitably make powerful enough processors to model a unive

• quickthrower2 9y ago
  If I were to do that, I'd put some constraints in to limit how much the creatures can explore of that universe. For example a maximum speed at which any matter can travel, for one.
  • doyoulikeworms 9y ago
    Why does this universe have a speed limit? Where does it come from? What enforces it?
    • irrational 9y ago
      https://aeon.co/essays/why-is-the-speed-of-light-the-speed-of-light https://aeon.co/essays/why-is-the-speed-of-light-the-speed-o...
    • ChrisSD 9y ago
      It's simply a consequence of our physical laws rather than something that's "enforced". And Relativity tells us that anything travelling faster than that would allow information to travel back in time, thus screwing up cause and effect thus our universe wouldn't exist as it does.
      • fjsolwmv 9y ago
        There's nothing logically impossible about time loops.
        • goatlover 9y ago
          Except for when they create logical paradoxes.
          • goldenkey 9y ago
            The universe doesn't enforce logic in the form of twins paradoxes and all that tomfoolery. Spacetime is a physical object not a logically consistent human centric clone enforcer.
      • raducu 9y ago
        Do you know any simple thought experiment that shows this "ftl means information traveling back in time"? What I've seen is that ftl travel breaks causality in our MODELS of spacetime.
    • resource0x 9y ago
      Suppose at some point of your universe you have some event the consequences of which you don't like. You'd like to roll it back. Due to the speed limit, said rollback affects only a limited area of the Universe. The "people" inside this area won't feel anything unusual during the operation, b/c their memory will be rolled back, too. You also need reversible physical laws for that to be feasible :)
    • raattgift 9y ago
      These are fairly good questions, and are the topics of study in a variety of fields touching on fundamental physics (e.g. physical cosmology, foundations of physics, ultra-high energy particle physics, etc.). > Where does [the speed limit] come from? Initial conditions. More on that in a moment. > What enforces it? We can parameterize c in our fundamental theories (or expansions thereof) and take a rigorous if mathematical approach to asking questions like: what if the (arbitrary) value of c were not constant everywhere -- for example, if it were different in the past of every point we can currently observer, or if it is different in one spacelike direction from another spacelike direction. We can also fix various sets of units and adjust c's arbitrary value up or down everywhere in spacetime. It turns out that astrophysical observables are highly sensitive to the universality of c, and that it would be virtually impossible for us to notice even a very small gradient in c since the very very early universe, and when we use just about any set of units to describe physics and then adjust the value of c in those units up or down we also get strongly different observables in astronomy and laboratory physics. So, it's not so much that it's "enforced", but rather that a different value of c, or a non-universal value of c, is strongly constrained by physics achievable in Victorian-era laboratories or by modern amateur enthusiasts. There are further types of "breaking" of the invariance of c, wherein one can have some fundamental interaction be constrained by a constant other than c. Most variable speed of light theories are directly written as (or clearly equivalent to) bimetric theories of gravitation, wherein some microscopic component of the Einstein Field Equation couples to a metric other than the standard one that everything else couples to. A toy example would be some form of exotic matter moving superluminally in Schwarzschild blackhole spacetime, such that there is an "inner" horizon that affects this exotic matter, and at high energies an interaction between normal matter and this exotic matter that transfers information from the former to the latter between the two horizons, allowing that information to escape to infinity encoded in the exotic matter. There are other examples from cosmology designed to do away with some aspects of the observed universe that support Cosmic Inflation (e.g. some exotic matter couples to a metric that allows it to spread heat evenly across the very early universe faster than heat could propagate if constrained by "c"). Such examples again are highly constrained: in both cases the second metric has to decay away so as to avoid being readily detected by our modern instruments. In the cosmological case, it has to be gone well before primordial nucleosynthesis, or it would leave obvious fingerprints in the cosmic microwave background and in the distribution of galaxies on our sky; the BH toy requires at least a cutoff that depends on the mass of the black hole, and so suffers badly when trying to apply the "toy" to real astrophysical situations involving collapsing stars. An anthropic argument answer is that the state of the universe around us humans is highly sensitive to conditions in our distant past, and thus our own existence is strong evidence supporting c as a constant everywhere in the past of the stuff that makes us human. Since that includes the views of objects in our sky as we make better and better telescopes, that [a] is further supporting evidence that [b] c is very likely a universal constant. Is that enforcement? That's probably more a metaphysical question than a physical one. (We can tone down the anthropic argument a bit and ask for evidence for a statement like: if c takes on an experimental value in one point in a spacetime filled with fields like ours, it must take on the same value at every other point in that spacetime too). Finally, "where does [the constant c and its value] come from": we don't know yet, but obviously there are scientists working in the subdisciplines listed in my first paragraph (and more) who are trying to find out. On the one hand, the parenthetical comment above suggests that we bend our own thinking and just accept that it doesn't "come from" anywhere, it just is; on the other hand we're pretty biased culturally with ideas about sequencing of cause and effect and about there being a real difference between past and future, so we like to slice up spacetimes into space and time and then think about how each space-like slice is related to its neighbours, and then to their respective neighbours, and so on. This cultural habit may be fruitful, or it may be a handicap, when it comes to answering questions about c. However, returning to "initial conditions", our present spacelike slice was determined by its immediate predecessor in the past, and that was determined by its immediate predecessor, and so on. If we keep regressing we might expect to come to "the start of time", and find some mechanism which sets c on that initial spacelike hypersurface. However, there are lots of ways to avoid having such an initial spacelike hypersurface even in a big bang cosmology! So while "initial conditions" is culturally the most favoured answer, and is well supported by evidence from physical cosmology, that may not be a sufficiently full answer. And that's going to be a topic for scientific research for some years to come...
    • hokus 9y ago
      Like conservation of energy this is the modern mythology. Not sure who is insulting who here, surely our ancestors "knew" all kinds of now know to be nonsensical things. They too believed to be advanced beyond that point. Its actually rather funny this stacking of "if we assume"'s into facts. You have to admire us for trying our best tho :-)
      • garmaine 9y ago
        Speed of light is mythology? Is this some sort of parody?
      • EpicEng 9y ago
        If you can disprove conservation of energy and faster than light travel I suggest you go claim your Nobel.
    • Retra 9y ago
      It comes from the inherent sloppy irrelevance of the notion of speed compared with the actual behavior of reality. If you cared about a different variable instead, it would not be so limited.
  • strainer 9y ago
    Even with the parallelism afforded by speed limits, a computer many trillions of times as powerful as we have today could not model the thoughts and life experiences of the billions of human beings and other creatures in this planet. Its not even clear that modelling thought in a virtual world has any equivalence to thinking in this world. It is clear that we are unlikely to ever model anything nearly as complicated as this.
    • eloff 9y ago
      I don't think it's clear. How long before our digital neural networks exceed the complexity of our human biological ones? It's possible today with a super cluster of sorts. That is to have roughly the same number of connections between neuron type thingies - it still wouldn't be able to match our brains functionally - that's another problem. And yes our biological neurons are way more sophisticated than what we use today for AI, but again that can be overcome eventually. This suggests that it's possible one day to have computers some orders of magnitude better. If you look at it from first principles, of course it's possible. The brain is unlikely to be the most efficient design of neural network allowable in this universe. So given enough time, we'll learn how to build it better. Then it's just a manufacturing and energy problem to match the number of human minds on the planet. So no, I don't think it's impossible at all. Just ridiculously freaking hard, and not likely to happen in our lifetimes.
      • mjburgess 9y ago
        It's not a matter of it being "hard". Nor is it a matter of "complexity" (how many parts something has). A simulation is a model which picks out a tiny subset of regularities in the target to model. There is an infinite density of such regularities to pick upon, because we are imposing the structure on the target in order to model it. The target of the model has no "model structure" it has causal structure. That is, when light interacts with the surface of a mirror its interaction isnt "abstract", ie., some description. It is an actual photon interacting with an actual electric field, etc. To "model to infinite density", ie., to have every single test that can possibly be applied to a model come out identical to that test of the target, the model needs to be just another example of the target. The only thing which can be investigated in any way to behave as light hitting a mirror, is light hitting a mirror. A digital computer is just an electric field oscillating across a silicon surface. It cannot be programmed into being a mirror, nor into being light. Programming gives the electric field a "model structure". Chalk gives a blackboard a "model structure". Lego gives a bridge a "model structure". Programming cannot not -- it is impossible -- give silicon the causal structure of light interacting with a mirror. Model structure is actually just an observer-relative isomorphism: when the user of the computer (chalkboard, lego,...) looks at it, the user, is able to inform himself of the target by use of the model. To do so the user identifies certain aspects of the model with the target. The model is not at all causally alike the target. No amount of lego will make a lego brain. No amount of oscillation in an electric field will make a thought. Neurological activity, and indeed every causal mechanism of the universe, is only described by a model.
  • russdill 9y ago
    But then make it much more complicated by throwing away simultaneity.
  • spectrum1234 9y ago
    Actually the world could be procedurally generated. And time in this world wouldn't have to be directly proportional to the base level world.
    • carlmr 9y ago
      It might be procedurally generated just for me, and everyone else is an NPC that only gets spawned randomly when I see them. They can keep my close friends in Cache, my acquaintances in RAM and the outside world on hard disk.
  • jayd16 9y ago
    We can also do some lazy loading and only calculate values when they're observed.
    • confluence 9y ago
      Some improvements are ensuring that when there are too many interactions, we slow down time, and speed it up when there aren't.
      • goldenkey 9y ago
        Relativity in a nut shell.
  • asfdsfggtfd 9y ago
    I would also not bother to calculate things like the momentum or position of particles until I had to... I'd probably use some sort of hybrid wave/particle model to facilitate the last minute calculations.
    • nnq 9y ago
      THIS is what really freaks me out about quantum mechanics... how eerily close it seems to what a computer engineer working on optimizing a simulation would design...
      • Retra 9y ago
        Humans discovered the laws of nature by solving language optimization problems. It's not a coincidence that things must be this way. The solution to every problem will look like it is the solution to an optimization problem, because optimization is how we solve problems. We basically perceive the world by simulating it. So we're kind of obligated to model the world as a simulation. That doesn't mean it can't be something different underneath, but we won't understand it in any other terms.
        • kirubakaran 9y ago
          "by solving language optimization problems" <= can you please explain?
          • Retra 9y ago
            We try to come up with language that accurately describes our experiences and models. Over time that language has come to incorporate a large variety of mathematical notation and physical descriptors that were selected by optimizing for usefulness, completeness, and pedagogical clarity.
  • super_mario 9y ago
    Interestingly enough the universe we find ourselves in already has such constraints. The speed of light is the upper limit for anything that has a mass (and is impossible to reach), and other stars are prohibitively far away for us to visit or explore in any detail. Perhaps the simulation did this on purpose, so they don't have to render far away galaxies in high resolution :D.
    • coryfklein 9y ago
      I think his comment was an oblique reference to the speed of light.
    • DtnB 9y ago
      C in m/s does fit into max int with room to spare. What I'm more concerned with is that our Universe might be running on SQL and that dark matter is actually table whitespace.
• itronitron 9y ago
  you mean like Minecraft?
  • freeflight 9y ago
    More like Dwarf Fortress
    • strainer 9y ago
      Indeed -its a small world :)
• tzahola 9y ago
  You don’t need huge processing power for that. You can do it on a - large enough - piece of paper by hand. Or with a bunch of rocks: https://imgs.xkcd.com/comics/a_bunch_of_rocks.png https://imgs.xkcd.com/comics/a_bunch_of_rocks.png
• beefield 9y ago
  Creatures? Why the plural, would not one be enough? I mean, what makes you think that this piece of text is written by a sentient human being instead of some buggy and crappy text generator script written by a school kid somewhere in the vastness of multiverse?
• carlmr 9y ago
  Say we live in a simulation, who is to say that the layer above is not a simulation as well? Every subsequent layer of simulation will be slower than the enveloping one. So you kind of get a VM inside a VM inside a VM at some point running out of resources.
• adynatos 9y ago
  can't you just slow the simulation down? processing one second would take (for example) one year, but the creatures inside the simulation wouldn't know that, would they?
• randyrand 9y ago
  In order to simulate something, you generally need 10x the compute. Physics is the architecture of the universe and it runs natively with a ton of "computations"/interactions per second. Maybe we could simulate the earth with a computer the size of 10 earths.