Re: Peculiarities of our universe
- Original Message - From: Hal Finney [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, January 10, 2004 12:24 AM Subject: Peculiarities of our universe There are a couple of peculiarities of our universe which it would be nice if the All-Universe Hypothesis (AUH) could explain, or at least shed light on them. One is the apparent paucity of life and intelligence in our universe. This was first expressed as the Fermi Paradox, i.e., where are the aliens? As our understanding of technological possibility has grown the problem has become even more acute. It seems likely that our descendants will engage in tremendous cosmic engineering projects in order to take control of the very wasteful natural processes occuring throughout space. We don't see any evidence of that. Similarly, proposals for von Neumann self reproducing machines that could spread throughout the cosmos at a large fraction of the speed of light appear to be almost within reach via nanotechnology. Again, we don't see anything like that. So why is it that we live in a universe that has almost no observers? Wouldn't it be more likely on anthropic grounds to live in a universe that had a vast number of observers? Assuming the validity of the AP, we should expect to find ourselves in the most typical of circumstances. We should thus expect that most observers are similar to us. So, most observers are not part of a very advanced civilization. Maybe, as I wrote in the other posting, this is because those civilizations consist of only one individual. This should follow from the AUH, but it is not very clear how. If most observers are like us, then we shouldn't expect to find much evidence of intelligent life, even if there are hundreds of civilizations in our galaxy now. Maybe the fact that we are in a situation in which we don't have controll over our own bodies very much is a clue. This should again be a typical situation observers find themselves in. They are on the verge of understanding how the universe works, but they don't have a cure for deadly diseases or old age. They don't have the capacity to design and build observers like themselves. It should thus be the case that the moment they do develop such capabilities, their numbers should decline dramatically. This should be a universal property of civilizations evolving in a universe with large measure. The second peculiarity is the seemingly narrow range of physical laws which could allow for our form of life to exist. Tegmark writes about this at http://www.hep.upenn.edu/~max/toe.html. He shows a chart of two physical constants and how if they had departed from their observed values by even a tiny percentage, life would be impossible. In the full paper linked from there he offers many more examples of physical paramters which are fine-tuned for life. So why is this? Why does it turn out that our form of life (or perhaps, any form of life) can exist for only a tiny range of variation? Why didn't it turn out that you could change many parameters a great deal and still have life form? I don't see anything a priori in the AUH that would have led to this prediction. Now, it may just be one of those things that happens to happen, a fundamental mathematical property like the distribution of primes or the absence of odd perfect numbers. Self-aware subsystems just mathematically turn out to only be possible in a very tiny region of parameter space. Now, you might be able to make the argument that tiny is not well defined, that there is no natural length scale for judging parameter ranges. Tegmark could as easily have zoomed in on the appropriate region of his graph and shown a huge, enormous area where parameters could be moved around and life would still work. However I think there is a more natural way to put the question, which is, what fraction of computer programs would lead to simulated universes that include observers? And here, if we follow Tegmark's ideas, the answer appears to be that it is a very small fraction. (Of course, you still need to use your own judgement to decide whether that is tiny or not.) I am not sure this is correct, I do agree that there is a problem here. Tegmark looks at what would happen if you change on or more parameters in the standard model and then concludes that the parameter space for life is very tiny. Most physicists believe that a fundamental theory with only a few parameter, e.g. superstring theory, could be behind the standard model. The standard model is what you get if you ''integrate out'' the as of yet unknown physics at the smallest length scales. Given that the fundamental theory is supposed to have only a few parameters, it should have a much larger measure than generic versions of the standard model. So, the problem is actually worse: Why does life only emerge in a tiny fraction of programs describing versions of the standard model? And of those programs that do give
Re: Is the universe computable?
Erick,thanks for your comments on my exchange with GeorgeQ. Although I do not claim to have understood (digested?) all of your post, I feel it may be in my line of thinking (pardon me the offense). I just use less connotations to 'time' related phrases, as may be obvious from below. Over the years I tried in several attempts to voice on this (and other) lists that all our phys-math considerations are secondary, coming from (and by) human understanding of something with/by human logic. I see no evidence that the existence (nature? everything) would follow our approval - 'our' as part/product of it. Physical law is a model of our thinking (I may be crucified for this) and fetishizing our understanding is IMO narrow. Even the 'elephant/rabbit' excursions start from some 'random' arrangement of photons, which are 'our' interpretation about sthing which may be interpreted quite differently by different mindsets. This is the reason - I think - why GeorgeQ found my ideas mystical. In my vocabulary mystical is what has not (yet?) been explained. I work with all unknown/unknowables, trying to make sense of the so far 'undiscovered' within the 'boundaries' of our mind. I call it my scientific agnosticism. Time and space are our crutches (boundaries? see below). Russell St. scolded me several times for my 'non-mathematical' stance as improper, vague, undefinable etc. - he is right, I don't 'force' my (our) understanding onto things beyond it. Equationally or not. I appreciate your remark: as later will be mentioned, boviously perception play a big role in this value, is your definition of the univers from the perspective of a human being, being that self within it's self, as projected outwards from a finite continuum into a supposedly infinite continuum? (whether 'boviously' is a typo for obviously, or a hint to the early style on this list calling adverse ideas bovine excrement). Somebody speculated on the way of 'thinking' on Venus where the clouds prevent any info about the extravenereal world (cosmology, philosophy, etc.). We are sitting closed in by a mental cloud of our understanding, ie boundaries of our mindset (epistemically steadily widening, however). I believe 'computation' here goes beyond the 'binary calculations' as well as (maybe) temporal considerations. Life I consider differently, IMO it is some natural function we overappreciate because we do it (cf the biology etc. in our reductionistic science system). 'Consciousness' I call the acknowledgement (by anything) and response to (incl, storage) of information - absolutely not restricted to functions we would deem 'life'. So I have no problem with 'universes' (not?) containing 'live' products. We muster a reductionistic way of our mindset: using limited models of observables, cut into (select) boundaries in a world of (wholistically) interconnected interaction of things way beyond our cognitive inventory. Regards John Mikes - Original Message - From: Erick Krist [EMAIL PROTECTED] To: [EMAIL PROTECTED]; John M [EMAIL PROTECTED] Sent: Tuesday, January 06, 2004 7:33 PM Subject: Re: Is the universe computable? to your series of questions I would like to add one as first: What do you call universe? i think this question is most temporally cognitively perceptual in nature. as explained: as long as we do not make this identification, it is futile to speculate about its computability/computed sate. as later will be mentioned, boviously perception play a big role in this value, is your definition of the univers from the perspective of a human being, being that self within it's self, as projected outwards from a finite continuum into a supposedly infinite continuum? or are you looking at the univers from the point of view of a rock which site blindly in time without temporant perceptual motion? obviously there are many different perceptual universes, and any of them could be philosphically percieved by the mind, therefor any of them would be physically coorect on a perceptual model of a temporant cyclical universe. we have to keep in mind, the time itself may only be a function of the combined perceptual receptions of our own internally functioning senses biologically simultaneously now. I see not too much value in assuming infinite memories and infinite time of computation, that may lead to a game and i may i beg to ask is a computer supposed to under any assumption compute a continuous value of infinite using binary logic as it's base computational rate? -calling computation the object to be computed. this is quite naturally the function of time works in the first place. time is the measure of the systematic computational functions of an internal system as measured by the temporant singularity of the external structures of that internal system as an alternatively functional singular temporant system of it's own. .: the nature of a coputationally temporant universe involves the notion of a
Re: Peculiarities of our universe
Hal Finney wrote: One is the apparent paucity of life and intelligence in our universe. This was first expressed as the Fermi Paradox, i.e., where are the aliens? As our understanding of technological possibility has grown the problem has become even more acute. It seems likely that our descendants will engage in tremendous cosmic engineering projects in order to take control of the very wasteful natural processes occuring throughout space. We don't see any evidence of that. Similarly, proposals for von Neumann self reproducing machines that could spread throughout the cosmos at a large fraction of the speed of light appear to be almost within reach via nanotechnology. Again, we don't see anything like that. So why is it that we live in a universe that has almost no observers? Wouldn't it be more likely on anthropic grounds to live in a universe that had a vast number of observers? Could be that 1. It's extremely rare to have a window for biological evolution to our level. (I highly recommend the well written basic-level but accurate and comprehensive new book called Origins of Existence by Fred Adams ISBN 0-7432-1262-2 which gives a complete summary of what had to happen for our emergence, and all the many ways how things could have gone differently, very few of which would lead to life anything like we know it.) 2. We're a distinguished member of the successful evolvers in the first available window-of-opportunity club. 3. If you believe 1 and 2, then note that we ourselves have not yet made galactically observable construction projects or self-replicating space-probes. Sure, we talk, but we haven't put our money where our mouth is yet. The (few, lucky to have emerged unscathed) other intelligent lifeforms in our observable universe may also not have done this within out lightcone (space-time horizon) of observability yet.
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/
Maximization the gradient of order as a generic constraint ?
In a previous post in reply to Hal Finnay, I have suggested the use of a particuliar case of additional conditions to the hypothetical set of equation that would rule ou universe. This is an attempt to clarify it while taking it out from the computation perspective with which it has nothing to do. Considering the kind of set of equation we figure up to now, completely specifying our universe from them seems to require two additional things: 1) The specification of boundary conditions (or any other equivalent additional constraint. 2) The selection of a set of global parameters. My suggestion is that for 1), instead of specifying initial conditions (what might be problematic for a number of reasons), one could use another form of additional high level constraint which would be that the solution universe should be as much as possible more ordered on one side than on the other. Of course, this rely on the possibility to give a sound sense to this, which implies to be able to find a canonical way to tell whether one solution of the set of equations in more more ordered on one side than on the other than another solution. This is a way to narrow down the set of solutions that offers several advantages: a) It removes the asymmetry in the choice of initial versus final (or any other combination of) conditions. b) It is consistent with boundaryless universes as proposed by Stephen Hawking for instance. c) It is able to make the flow of time appear as an emergent property instead of being postulated and built upon. d) This kind of condition is very well appropriate to select those in which SASs have chance to emerge. This condition does not seem alone enough to define a unique mathematical structure but there might be a little number of ways according to which the remaining symmetries could be canonically broken. It might well be that this additional constraint can also be used for selecting the appropriate set of global parameter for the set of equations considered in 2). It does not seem counter-intuitive that the sets of global parameters that allows for the maximization of the gradient of order among all possible solutions considering all possible values for global parameters be precisely those for which SASs emerges and therefore those we see in our universe: universes not able to generate complex enough substructures to be self aware would probably equally fail to exhibit large gradients of order and vice versa. The hypothesis of the maximization the gradient of order seems even Popper-falsfiable. At least one prediction can be made: Given the set of equation that describe our universe and the corresponding set of global parameters, if we can find a canonical way to compare the relative global gradient of order within the universes that satisfy this set of equations: 1) It could be possible to determine the subset of universes that maximize the gradient for each set of global parameters (comparing all possible universes for a given set of global parameters), these being called optimal for this set of global parameters. 2) It could be possible to determine the sets of global parameters that maximize the gradient in an absolute way (comparing optimal universes for all possible sets of global parameters). The prediction is that the set of global parameter that we observe is one of those that maximizes the gradient of order within the corresponding optimal universes. A prediction with a weaker version of 2) would be that the set of global parameter that we observe must be consistent with any constraint we can obtain from the maximization constraint. It might be possible to solve problem 2) (finding the optimal sets of global parameter or some constraints on them) from high level considerations without being able to solve problem 1) finding the corresponding optimal universes. Maybe also the constraint could be used at a third level if it can remain consistent as a mean to select the appropriate set of equations. Finally, the hypothesis of the maximization of the gradient of order within universes could offer the additional advanatges: e) It does not involve any arbitrary parameter. f) It might help not to require that a choice be arbitrarily made within an infinite set. Do all of this make sense ? Has it already been considered ? Georges Quénot.
Re: Maximization the gradient of order as a generic constraint ?
Georges Quenot writes: Considering the kind of set of equation we figure up to now, completely specifying our universe from them seems to require two additional things: 1) The specification of boundary conditions (or any other equivalent additional constraint. 2) The selection of a set of global parameters. My suggestion is that for 1), instead of specifying initial conditions (what might be problematic for a number of reasons), one could use another form of additional high level constraint which would be that the solution universe should be as much as possible more ordered on one side than on the other. Of course, this rely on the possibility to give a sound sense to this, which implies to be able to find a canonical way to tell whether one solution of the set of equations in more more ordered on one side than on the other than another solution. I think this is a valid approach, but I would put it into a larger perspective. The program you describe, if we were to actually implement it, would have these parts: It has a certain set of laws of physics; it has a certain order-measuring function (perhaps equivalent to what we know as entropy); and it has a goal of finding conditions which maximize the difference in this function's values from one side to the other of some data structure that it is modifying or creating, and which represents the universe. It would not be particularly difficult to implement a toy version of such a program based on some simple laws of physics, and perhaps as you suggest our own universe might be the result of an instance of such a program which is not all that much more large or complex. In the context of the All Universe Principle as interpreted by Schmidhuber, all programs exist, and all the universes that they generate exist. This program that you describe is one of them, and the universe that is thus generated is therefore part of the multiverse. So to first order, there is nothing particularly surprising or problematical in envisioning programs like this as contributing to the multiverse, along with the perhaps more naively obvious programs which perform sequential simulation from some initial conditions. All programs exist, including ones which create universes in even more strange or surprising ways than these. By the way, Wolfram's book (wolframscience.com) does consider some non-sequential simulations as models for simple 1- and 2-dimensional universes. These are what he calls Systems Based on Constraints discussed in his chapter 5. Where I think your idea is especially interesting is the possibility that the program which creates our universe via this kind of optimization technique (maximizing the difference in complexity) might be much shorter than a more conventional program which creates our universe via specifying initial conditions. Shorter programs are considered to have larger measure in the Schmidhuber model, hence it is of great importance to discover the shortest program which generates our universe, and if optimization rather than sequential simulation does lead to a much shorter program, that means our universe has much higher measure than we might have thought. However, I don't think we can evaluate this possibility in a meaningful way until we have a better understanding of the physics of our own universe. I am somewhat skeptical that this particular optimization principle is going to work, because our universe's disorder gradient is dominated by the Big Bang's decay to heat death, and these cosmological phenomena don't necessarily seem to require the kinds of atomic and temporal structures that lead to observers. If you look at Tegmark's paper http://www.hep.upenn.edu/~max/toe.html which lists a number of the physical-constant coincidences necessary for life, not all of them would have cosmological importance and change the order-to-disorder gradient of the universe. It might well be that this additional constraint can also be used for selecting the appropriate set of global parameter for the set of equations considered in 2). It does not seem counter-intuitive that the sets of global parameters that allows for the maximization of the gradient of order among all possible solutions considering all possible values for global parameters be precisely those for which SASs emerges and therefore those we see in our universe: universes not able to generate complex enough substructures to be self aware would probably equally fail to exhibit large gradients of order and vice versa. Certainly an interesting suggestion. Again, when we look at the larger view of all possible programs, we have optimization programs which have some parameters fixed; and optimization programs which allow the parameters to vary as part of the optimization process. The latter programs would tend to be smaller since they don't have to store the value of the fixed parameters; but on the other hand the need to allow for varying the
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:
