Re: Why no white talking rabbits?
Eric Hawthorne wrote: So the answer to *why* it is true that our universe conforms to simple regularities and produces complex yet ordered systems governed (at some levels) by simple rules, it's because that's the only kind of universe that an emerged observer could have emerged in, so that's the only kind of universe that an emerged observer ever will observe. That's not true--you're ignoring the essence of the white rabbit problem! A universe which follows simple rules compatible with the existence of observers in some places, but violates them in ways that won't be harmful to observers (like my seeing the wrong distribution of photons in the double-slit experiment, but the particles in my body still obeying the 'correct' laws of quantum mechanics) is by definition just as compatible with the existence of observers as our universe is. So you can't just use the anthropic principle to explain why we don't find ourselves in such a universe, assuming you believe such universes exist somewhere out there in the multiverse. Jesse _ Learn how to choose, serve, and enjoy wine at Wine @ MSN. http://wine.msn.com/
Re: Why no white talking rabbits?
Hal Finney wrote: Jesse Mazer writes: Hal Finney wrote: However, I prefer a model in which what we consider equally likely is not patterns of matter, but the laws of physics and initial conditions which generate a given universe. In this model, universes with simple laws are far more likely than universes with complex ones. Why? If you consider each possible distinct Turing machine program to be equally likely, then as I said before, for any finite complexity bound there will be only a finite number of programs with less complexity than that, and an infinite number with greater complexity, so if each program had equal measure we should expect the laws of nature are always more complex than any possible finite rule we can think of. If you believe in putting a measure on universes in the first place (instead of a measure on first-person experiences, which I prefer), then for your idea to work the measure would need to be biased towards smaller program/rules, like the universal prior or the speed prior that have been discussed on this list by Juergen Schimdhuber and Russell Standish (I think you were around for these discussions, but if not see http://www.idsia.ch/~juergen/computeruniverse.html and http://parallel.hpc.unsw.edu.au/rks/docs/occam/occam.html for more details) No doubt I am reiterating our earlier discussion, but I can't easily find it right now. I claim that the universal measure is equivalent to the measure I described, where all programs are equally likely. Feed a UTM an infinite-length random bit string as its program tape. It will execute only a prefix of that bit string. Let L be the length of that prefix. The remainder of the bits are irrelevant, as the UTM never gets to them. Therefore all infinite-length bit strings which start with that L-bit prefix represent the same (L-bit) program and will produce precisely the same UTM behavior. Therefore a UTM running a program chosen at random will execute a program of length L bits with probability 1/2^L. Executing a random bit string on a UTM automatically leads to the universal distribution. Simpler programs are inherently more likely, QED. I don't follow this argument (but I'm not very well-versed in computational theory)--why would a UTM operating on an infinite-length program tape only execute a finite number of bits? If the UTM doesn't halt, couldn't it eventually get to every single bit? If the everything that can exist does exist idea is true, then every possible universe is in a sense both an outer universe (an independent Platonic object) and an inner universe (a simulation in some other logically possible universe). This is true. In fact, this may mean that it is meaningless to ask whether we are an inner or outer universe. We are both. However it might make sense to ask what percentage of our measure is inner vs outer, and as you point out to consider whether second-order simulations could add significantly to the measure of a universe. What do you mean by add significantly to the measure of a universe, if you're saying that all programs have equal measure? If you want a measure on universes, it's possible that universes which have lots of simulated copies running in high-measure universes will themselves tend to have higher measure, perhaps you could bootstrap the global measure this way...but this would require an answer to the question I keep mentioning from the Chalmers paper, namely deciding what it means for one simulation to contain another. Without an answer to this, we can't really say that a computer running a simulation of a universe with particular laws and initial conditions is contributing more to the measure of that possible universe than the random motions of molecules in a rock are contributing to its measure, since both can be seen as isomorphic to the events of that universe with the right mapping. We have had some discussion of the implementation problem on this list, around June or July, 1999, with the thread title implementations. I would say the problem is even worse, in a way, in that we not only can't tell when one universe simulates another; we also can't be certain (in the same way) whether a given program produces a given universe. So on its face, this inability undercuts the entire Schmidhuberian proposal of identifying universes with programs. However I believe we have discussed on this list an elegant way to solve both of these problems, so that we can in fact tell whether a program creates a universe, and whether a second universe simulates the first universe. Basically you look at the Kolmogorov complexity of a mapping between the computational system in question and some canonical representation of the universe. I don't have time to write more now but I might be able to discuss this in more detail later. Thanks for the pointer to the implementations thread, I found it in the archives here:
Re: Why no white talking rabbits?
Hal Finney wrote: What about a universe whose space-time was subject to all the same physical laws as ours in all regions - except in the vicinity of rabbits? And in those other regions some other laws applied which allow rabbits to behave magically? While this may be possible, we seem to have found so far that the universe admits of many simple regularities in its complex systems and its fundamental laws. Therefore many of the essential properties (future-form-and-behaviour-determining properties) of these complex systems admit of accurate description by SIMPLE, SMALL theories that describe these simple regularities in the complex systems. I challenge you to come up with a simple, small, (thus elegant), and accurately explanatory theory of how space-time could be as you propose above, and also how this wouldn't mess up a whole bunch of other observed properties of the universe. My point is I don't think you (or anyone)'d ever be able to come up with a small, simple, yet explanatory theory of the white rabbit universe you suggest. AND THAT THEREFORE, at least according to how we've always seen the essential aspects of the universe conform to simple elegant theories and laws before, THE RABBITS SCENARIO (bizarrely strange yet still straightforwardly observable spacetime pockets) IS UNLIKELY TO BE THE TRUE STATE OF AFFAIRS in the universe. Could such a bizarre universe exist? Well possibly, (I personally think not an observable one), but in any case it would be a highly difficult universe (unmodellable with simple models) and physicists would be unemployed in that universe, as their predictions based on simple, clever theories would never turn out to work. Magicians and wizards (those able to pretend they'd been responsible for the last bit of observed extreme weirdness) would hold sway. Eric
Re: Why no white talking rabbits?
John Collins writes: I described a special case of this in a posting on this list a while ago, suggesting that we're almost certainly not in a simulated, 'second order' universe: Basically, for every arrangement of matter you could append to our universe that would look like some creature controlling/observing us, there would be many more arrangements that looked like no living creature. That's an interesting point, but I'm not sure it's correct. You might want to consider Nick Bostrom's Simulation Argument at www.simulation-argument.com as an alternative. I think the problem with your argument is that you are assuming that all physical arrangements of matter appended to the universe are equally likely. And in that case, you are right that some random arrangement would be far more likely than one which looks like an observer who has set up a computer to simulate our universe. However, I prefer a model in which what we consider equally likely is not patterns of matter, but the laws of physics and initial conditions which generate a given universe. In this model, universes with simple laws are far more likely than universes with complex ones. It seems plausible that our own laws of physics are not particularly complex. If string theory or loop quantum gravity or some other merging of QM and GR can work, we may well find that our entire universe is isomorphic to a few lines of mathematical equations. Similarly there are provocative hints that the initial state of the universe was extremely simple and had low complexity. These prospects lend support to my view, even though the universe contains objects of immense complexity. It's not the complexity of the universe that counts, it's the complexity of the equations that generate the universe. Consider a universe just like ours but where a given person is replaced by a random pattern of matter. Based on matter complexity, such a universe may seem more likely, since the structure of a human being is incredibly complex. But based on generative-law complexity, such a universe is much less likely, since it has a hole where the laws of physics did not apply, where what should have been a human being was artificially replaced by a random pattern. Therefore I'd suggest that when you consider the possibility that our universe is embedded in a larger structure, you can't just look at the matter complexity of that structure. Rather, you should look at the physical-law complexity. And it seems plausible to me that the physical laws of the outer universe don't necessarily have to be much more complex than our own. In fact, it may be that we are capable of simulating our own universe (we don't know the laws of physics well enough to answer that question, IMO). Nick Bostrom proposes in effect that the outer universe could be the mathematically identical to the inner one. He also suggests that there could be many simulations running, so that the number of observers in the simulated universes is far greater than the number in the outer universe. Based on this reasoning, the likelihood of our being in a second-order simulated universe is very considerable and can't be ruled out. Hal Finney
Re: Why no white talking rabbits?
Chris Collins wrote: This paradox has its origin in perception rather than fundamental physics: If I fill a huge jar with sugar and proteins and minerals and shake it, there is no reason why I can't produce a talking rabbit, or even a unicorn with two tails. Yet out out of the vast menagerie of novel objects and creatures I could produce, I always seem to get a bubbling cloudy liquid. The solution, of course, is that there is an even larger menargerie of objects, all of which look the same to me (like a bubbling cloudy liquid, in fact). This is exactly why I suggested the white rabbit example was misleading, and that it would be better to focus on an example where the number of possible outcomes predicted by physical laws is much *smaller* than the number of logically possible outcomes, like in the double-slit experiment. Similarly, there is no reason ehy such object, could not appear out of the quantum vacuum, but it must be the case that this vacuum throws up a lot of different objects and events that look to us like 'empty space' and 'nothing happening' (although I suspect that the case of the paradox you give of the double slit experiment has its origins in considering too large a set of states as 'possible'; the positions of the photons are not really free variables, with the apparently 'artificial' physical laws following from the initial data. It's like asking why the pegs on my washing line always follow the 'coshine law'...). What do you mean by not free? Surely if the everything that can exist, does exist hypothesis is true, then for every possible pattern of photons hitting the screen, there is a reality where some version of you experiences exactly that pattern when he does the experiment (a version of you that has no memory of any previous violations of the laws of physics, mind you). Thus you really need some kind of measure, either on possible universes or possible observer-moments, to justify the belief that you have a very low probability of experiencing one of these outcomes. You can't just take the probabilities predicted by the laws of physics for granted, if you believe in the existence of universes/observer-moments where these laws can change. Jesse _ Have fun customizing MSN Messenger learn how here! http://www.msnmessenger-download.com/tracking/reach_customize
Re: Why no white talking rabbits?
Hal Finney wrote: I think the problem with your argument is that you are assuming that all physical arrangements of matter appended to the universe are equally likely. And in that case, you are right that some random arrangement would be far more likely than one which looks like an observer who has set up a computer to simulate our universe. However, I prefer a model in which what we consider equally likely is not patterns of matter, but the laws of physics and initial conditions which generate a given universe. In this model, universes with simple laws are far more likely than universes with complex ones. Why? If you consider each possible distinct Turing machine program to be equally likely, then as I said before, for any finite complexity bound there will be only a finite number of programs with less complexity than that, and an infinite number with greater complexity, so if each program had equal measure we should expect the laws of nature are always more complex than any possible finite rule we can think of. If you believe in putting a measure on universes in the first place (instead of a measure on first-person experiences, which I prefer), then for your idea to work the measure would need to be biased towards smaller program/rules, like the universal prior or the speed prior that have been discussed on this list by Juergen Schimdhuber and Russell Standish (I think you were around for these discussions, but if not see http://www.idsia.ch/~juergen/computeruniverse.html and http://parallel.hpc.unsw.edu.au/rks/docs/occam/occam.html for more details) Therefore I'd suggest that when you consider the possibility that our universe is embedded in a larger structure, you can't just look at the matter complexity of that structure. Rather, you should look at the physical-law complexity. And it seems plausible to me that the physical laws of the outer universe don't necessarily have to be much more complex than our own. In fact, it may be that we are capable of simulating our own universe (we don't know the laws of physics well enough to answer that question, IMO). If the everything that can exist does exist idea is true, then every possible universe is in a sense both an outer universe (an independent Platonic object) and an inner universe (a simulation in some other logically possible universe). If you want a measure on universes, it's possible that universes which have lots of simulated copies running in high-measure universes will themselves tend to have higher measure, perhaps you could bootstrap the global measure this way...but this would require an answer to the question I keep mentioning from the Chalmers paper, namely deciding what it means for one simulation to contain another. Without an answer to this, we can't really say that a computer running a simulation of a universe with particular laws and initial conditions is contributing more to the measure of that possible universe than the random motions of molecules in a rock are contributing to its measure, since both can be seen as isomorphic to the events of that universe with the right mapping. Jesse Mazer _ Get reliable dial-up Internet access now with our limited-time introductory offer. http://join.msn.com/?page=dept/dialup
Re: Why no white talking rabbits?
Jesse Mazer wrote: Why, out of all possible experiences compatible with my existence, do I only observe the ones that don't violate the assumption that the laws of physics work the same way in all places and at all times? There are two kinds of white rabbits: microscopic and macroscopic. Microscopic white rabbits exist all around us. Particles popping in and out of the vacuum, particles being two places at the same time and so on. Microscopic white rabbits obey statistical rules, distributions etc, which translate into very solid and reproducible macroscopic laws such as the second law of thermodynamics. Because of these solid macroscopic laws, macroscopic white rabbits are extremely rare. The macroscopic laws of physics are the same everywhere because mathematics (statistics) is the same everywhere. In the multiworld context one could say that each multiworld branching is a white rabbit, but these rabbits are too small to notice classically. Thus, overall the number of worlds not containing macroscopic white rabbits is much larger than those containing macroscopic white rabbits. Therefore the transition from one world to the next is extremely unlikely to display a macroscopic white rabbit. Ergo: No observable macroscopic white rabbit. But of course the biggest rabbit is taken for granted. It is right under our nose and so close that we don't see it. George Levy
Why no white talking rabbits?
Jesse Mazer wrote: Why, out of all possible experiences compatible with my existence, do I only observe the ones that don't violate the assumption that the laws of physics work the same way in all places and at all times? Because a universe whose space-time was subject to different physical laws in different regions would not have been able to generate you and sustain you, or more precisely I suppose would only be able to generate and sustain you with infinitesimal probability. And it would be even more highly unlikely that should you have been magically conjured by this inconsistent-or-inconstant-physical-laws universe, that you would observe any other people (or rabbits, white or otherwise) because they themselves would have only infinitesimal probability of being magically, coincidentally conjured into that universe. It's better to find the all of the essential constraints (all the way back to 10^-43 seconds after the big bang) which made it highly probable that you (or something like you) would exist in the universe, and then explain how those constraints are all consistent with each other and with information theory, and then to realize that a set of constraints HAS TO BE consistent with (all of) each other and with information theory and with making your (or equivalent creature's) existence highly probable, in order for you to actually exist with any high probability. By the argument de facto, I think it's safe to say that things in the universe are such that people (or functional equivalents) are highly probable to exist on a small but significant set of planets (those with the right temperature ranges and proportions of different elements) in the galaxies in our observable portion of the universe. It is ONE HELL OF A DETAILED SET OF CONSTRAINTS that made all of this (us) highly probable, White talking rabbits with watches are inconsistent with those constraints, in ways too boring perhaps to get into. Ok, since we're way down here in the post, I'll get into it. General intelligence of human-like level (involving ability to hypothesize, abstract flexibly, construct a wide variety of functional, purposeful constructions out of raw materials, and plan actions and consequences in detail), only evolves by natural selection in critters that are physically equipped to DO SOMETHING with their intelligence. For a rabbit, it's pretty much limited to hopping about in more complex patterns to avoid being eaten, based on some kind of vastly intelligent psyching out of where its preditor is going to strike next, and to determining where to find the very best places to find the most nutritious and tasty grass. This is too limited a domain to require or select for a general, long-range constructing and planning mind-firmware to develop in a rabbit brain.. Another favorite of mine is why dolphins and whales are KIND OF intelligent (like a poodle or parrot is) but not extremely...So what, we're going to develop more complex tricky ways to bump things with our snouts? I don't think so. Group hunting (in a too-easy, too uniform, too acceleration-constrained-because viscous fluid habitat) is as complex as dolphin brains ever need to be. Cheers, Eric
Re: Why no white talking rabbits?
Jesse Mazer wrote: Why, out of all possible experiences compatible with my existence, do I only observe the ones that don't violate the assumption that the laws of physics work the same way in all places and at all times? Eric Hawthorne replied: Because a universe whose space-time was subject to different physical laws in different regions would not have been able to generate you and sustain you, or more precisely I suppose would only be able to generate and sustain you with infinitesimal probability. What about a universe whose space-time was subject to all the same physical laws as ours in all regions - except in the vicinity of rabbits? And in those other regions some other laws applied which allow rabbits to behave magically? Hal Finney
