RE: Is the universe computable
David Barrett-Lennard writes: Why is it assumed that a multiple runs makes any difference to the measure? One reason I like this assumption is that it provides a natural reason for simpler universes to have greater measure than more complex ones. Imagine a Turing machine with an infinite program tape. But suppose the actual program we are running is finite size, say 100 bits. The program head will move back and forth over the tape but never go beyond the first 100 bits. Now consider all possible program tapes being run at the same time, perhaps on an infinite ensemble of (virtual? abstract?) machines. Of those, a fraction of 1 in 2^100 of those tapes will start with that 100 bit sequence for the program in question. And since the TM never goes beyond those 100 bits, all such tapes will run the same program. Therefore, 1/2^100 of all the executions of all possible program tapes will be of that program. Now consider another program that is larger, 120 bits. By the same reasoning, 1 in 2^120 of all possible program tapes will start with that particular 120-bit sequence. And so 1/2^120 of all the executions will be of that program. Therefore runs of the first program will be 2^20 times more numerous than runs of the second. If we use the assumption that each of these multiple executions or runs contributes to the measure, we therefore can conclude that the measure of the universe generated by the first program is 2^20 times greater than the measure of the universe generated by the second. And more generally, the measure of a universe is inversely related to the size of the program which creates it. Therefore, QED, universes with simple programs have a higher measure than universes with more complex programs. This conclusion then allows us to further conclude that observers are likely to evolve in lawful universes, that is, universes without flying rabbits, i.e. rare, magical exceptions to otherwise universal laws. And we can conclude that the physical laws are likely to be stable or at least predictable over time. All of these are very properties of the universe which are otherwise difficult or impossible to explain. The fact that the multiverse hypothesis can provide some grounds for explaining them is one of the main sources of its attractiveness, at least for me. However, all this is predicated on the assumption that multiple runs of the same program all contribute to the measure. If that is not true, then it would be harder to explain why simple programs are of higher measure than more complex ones. If the computation is reversible we could run the simulation backwards - even though the initial state make seem contrived because it leads to a low entropy at the end of the computation. Given that the simulated beings don't know the difference (their subjective time runs in the direction of increasing entropy) the fact that the simulation is done in reverse is irrelevant to them. Would a simulation done in reverse contribute to the measure? When I think of the abstract notion of a universal TM that runs all possible programs at once, I don't necessarily picture an explict time element being present. I think of it more as a mapping: TM + program == universe. The more programs which create a given universe, the higher the measure of that universe. However, I don't think I can escape from your question so easily. We could alternately imagine an actual, physical computer, sitting in our universe somewhere, simulating another universe. And that should contribute to that other universe's measure. In that case we should have some rule that would answer questions about how much reversible and reversed simulations contribute. I would consider applying Wei Dai's heuristic, which I discussed the other day. It says that the measure of an object is larger if the object is easier to find in the universe that holds it. I gave some rough justifications for this, such as the fact that a simple counting program eventually outputs every million bit number, but no one would say that this means that the complexity of a given million bit number is as small as the size of that program. In this context, the heuristic would say that the contribution of a physical computer simulating another universe to the measure of that simulated universe should be based on how easy it is to find the computation occuring in our own universe. Computations which occur multiple times would be easier to find, so by Wei's heuristic would have higher measure. This is another path to justify the assumption that multiple simulations should contribute more to measure. I'd say that a computation running backwards contributes as well, by making it easier to locate. Now take a complex case, where a computation ran forwards for a while, then backwards, then forwards. I'd say that this heuristic suggests that the portion of the simulated universe which was repeated 3 times (forwards, backwards, forwards) would have
RE: Is the universe computable
At 1/18/04, Hal Finney wrote: Now consider all possible program tapes being run at the same time, perhaps on an infinite ensemble of (virtual? abstract?) machines. Of those, a fraction of 1 in 2^100 of those tapes will start with that 100 bit sequence for the program in question. [snip] Now consider another program that is larger, 120 bits. By the same reasoning, 1 in 2^120 of all possible program tapes will start with that particular 120-bit sequence. And so 1/2^120 of all the executions will be of that program. Yes, but if we're really talking about all possible finite bit strings, then the number of bit strings that begin with that 100 bit program is exactly the same as the number that begin with the 120 bit program - countably infinite. You can put them into a 1 to 1 correspondence with each other, just like you can put the integers into a 1 to 1 correspondence with the squares. The intuition that there must be more integers than squares is simply incorrect, as Galileo pointed out long ago. So shouldn't your two programs have the exact same measure? I don't mean to sound so critical - I'm genuinely asking for information. I know virtually nothing about measure theory. Is there some well-defined way of getting different measures for countably infinite sub-sets of a countably infinite ensemble? -- Kory
Papers of Lockwood, Albert-Loewer
I wish to read these 3 papers, which I have not found on the net in full text. Would anyone have them or know where they can be found? Thanks Albert, D and Loewer, B.: 1988, `Interpreting the Many Worlds Interpretation', Synthese, 77, 195-213 Lockwood, M. [1996a]: Many Minds Interpretations of Quantum Mechanics , British Journal for the Philosophy of Science, 47, pp.159-88 Lockwood, M. [1996b]: Many Minds Interpretations of Quantum Mechanics: Replies to Replies , British Journal for the Philosophy of Science, 47, pp.445-61
Re: Papers of Lockwood, Albert-Loewer
The latter two papers can be found on JSTOR. I've placed copies at http://www.ibiblio.org/weidai/Many_Minds.pdf http://www.ibiblio.org/weidai/Many_Minds_Replies.pdf The first paper doesn't seem to be online anywhere. There's an online archive for Synthese at http://www.kluweronline.com/issn/0039-7857/contents, but it only goes back to 1997. You'll have to find the physical journal in an academic library. Or try writing to the authors and asking for a copy to be mailed to you. On Mon, Jan 19, 2004 at 10:52:09AM +, Giu1i0 Pri5c0 wrote: I wish to read these 3 papers, which I have not found on the net in full text. Would anyone have them or know where they can be found? Thanks Albert, D and Loewer, B.: 1988, `Interpreting the Many Worlds Interpretation', Synthese, 77, 195-213 Lockwood, M. [1996a]: Many Minds Interpretations of Quantum Mechanics , British Journal for the Philosophy of Science, 47, pp.159-88 Lockwood, M. [1996b]: Many Minds Interpretations of Quantum Mechanics: Replies to Replies , British Journal for the Philosophy of Science, 47, pp.445-61
Re: Is the universe computable
At 17:36 16/01/04 +0100, Eugen Leitl wrote: On Fri, Jan 16, 2004 at 02:28:27PM +0100, Bruno Marchal wrote: of brain and the like. I of course respect completely that opinion; but I point on the fact that once you make the computationnalist hypothesis then it is the reverse which becomes true: even if locally pi is a production of the human brain, globally the laws of physics logically develop on the set of all possible beliefs of all possible universal and immaterial (mathematical) machines embedded in all possible computations (computationnal histories). I respect that opinion, Actually it is more a theorem than an opinion. But I don't want to insist on this at this stage, I guess it would be premature. I'm just interested in theories which are instrumental in solving this universe's problems. You know, trivial stuff: wars, famines and death. A TOE which says: universe is information, every possible pattern exists, observers which can observe themselves will, is a bit sterile in that respect. That's my point: the comp hyp is popper falsifiable, because it put very strong constraint on any possible measure on the set of all computational histories (as seen from any possible sound first person). Unfortunately the notion of first person is hard to make precise without going into the modal logics. There's a little problem with some practical relevance I don't have an answer, though, which I'd like to have your opinion on. We have a finite system, iteratively evolving along a trajectory in state space. We have observers within that system, subjectively experiencing a flow of time. I have trouble alternating between the internal and the external observer view. So we have a machine crunching bits, sequentially falling from state to state. This spans a continous trajectory. We can make a full record of that trajectory, eliminating a time axis. When does the subjective observation of existence assemble into place? The first time the computation was made? The type of approach advocated in this list makes indeed possible to answer such a question. Of course I will ask you, if only for the sake of the argument, to accept that idea that all arithmetical true propositions are true in a atemporal way (and a-spatial way too btw). Now a computation can be described as a purely arithmetical object (to make this precise you need Church thesis aswell). Such computation are never run, they exist like the decimals of PI once and forall (by Arithmetical realism of course). The subjective observation as such will then also exists out of space and time, and will be felt as a time ordered, or as a space-time structured scenario only from the point of view of the observer which is related to that computation. If you want, from each instant an observer can think, that instant is now. In philosophy such a treatment of subjective time is called an indexical. This is counterintuitive because people (including many defender of comp) are used to believe in the following psycho-physical relation: (the sensation of pain/pleasure) at space-time point (x,t) is associated with the physical state of some device at space-time (x,t) But comp precludes this and forces instead: the sensation of (pain/pleasure at space-time point (x,t)) is associated with a (infinite set of equivalent) relative computational state(s). That is the space-time qualia is completely part of the sensation. I have trouble seeing my subjective observer experience as a sequence of frames, already computed. No problem. It is totally unbelievable. As it should be in case it is true. *that* can be proved. Such unbelievable but true proposition belongs to the family of undecidable but true arithmetical propositions. Is the first run magical, and the static record dead meat? I'm confused. The static record (here it is the set of all true arithmetical proposition) is similar to any block universe view in which time is internal. Note that this is the case for quantum cosmology where time disappears from the fundamental equation without precluding internal time to be defined. Remember the DeWitt Wheeler equation H = 0. With comp, space itself is illusion, although that word is misleading in the sense that comp justify the solidity and stability of such illusion. Actually this has not yet be shown, but It has been shown how to translate that problem into a mathematical question. In case the math leads to not enough stability, that will give a falsification of comp. Let's bring a little dust into the run. Let's say we use a HashLife approach, which assembles the flow from lightcone hashes. Does this screw up the subjective experience? If yes, how? I don't think this will screw up the subjective experience. The illusion of time makes part of the relativeness of the computational states. What about computing a record of all possible trajectories? Is enumerating all possible states sufficient to create an observer
Re: Is the universe computable?
At 15:05 16/01/04 +0100, Georges Quenot wrote: Possibly making you not better than them. But this not that simple. They do not disagree with dialog and argumentation. Rather they argue in different ways and/or with different premises. OK, so I perhaps did not understand you fully. I thought they did not even accept AR, or 2+2=4 for the sake of the argument. If they finally have to abandon these positions due to the amount of evidence in favor of it, the last line of defence for their conception of a personal God and for a significant role for Him could be at the level of artihmetical realism. Artihmetical realism by itself (not from a distinct personal God) is therefore seen as evil by them. As I mentionned, they usually do not put it that way. Rather they argue that such a view would prevent the foundation of human dignity and the like. They make probably the same confusion of those who believe that determinism is in contradiction with free will. I would say that one of the concern they have behind this is the question of free will versus determinism (and/or randomness). You and others might see this as making the same confusion of those who believe that determinism is in contradiction with free will. But there might also be more than one conception of free will and we could also consider that what they are doing is trying to defend another conception of free will that the one which is not in contradiction with determinism (and/or randomness). Look, I have no problem at all with any people open to defend they point, I am always prepared to make evolve my own position. But I really don't appreciate those who wants to impose any position (even mine). By its very nature free-will is hard to define and I quite believe there is as many conception of free-will than there are free-person. Though we may or may not share this conception, I don't think that we can dismiss it. The only thing we can say is that they cannot convince us of it or possibly even of its meaningfulness but in the same way we have no ground to prove them they are wrong. No problem as long as they don't use authoritative argument. Basically, they want to believe that we humans are not reducible to numbers and I think that such a reductibility cannot be proved either way. Er... No scientific proposition can *ever* be proved. Only refuted, or confirm. Except perhaps a tiny part of intuistionist mathematics. Also I understand that one could feel offended by the idea that he could be reduced to mere numbers (not more but not less he would feel offended by the idea it could be reduced to a set of interacting molecules) even if these ideas are considered as just hypotheses. They want to believe (and they want to be generally believed) that there is (much) more than this in human beings (and incidently in themselves). It is ok, in principle. It all depend on the way they will make us to believe their proposition. I am used to met people who are shocked by the idea of being a machine. I think those people ahave just a lack of trust in themselves. If I like myself and if I learn that I am a machine, then I will say formidable, some machine can be nice like me. If I dislike myself, and I learn that I am a machine, then I will say I knew I was just a stupid machine. Just to say that if someone has the faith (or some deep faith) he/she will not be afraid by *and* hypothesis. Those who are afraid by hypotheses are really afraid of the fragility of their own ideas or of their own faith. Actually I tend to think that Godel's and other incompleteness result makes comp a sort of vaccine against reductionist view of self and reality (and arithmetic). This is not obvious to me. Maybe what reductionist actually means needs to be clarified. Sure. It is a very big thread by itself. You know reason works only through doubt, and through the ability to listen to different opinions. I tend to agree but it does not seem enough just to say it. I guess it is not enough. As I said it is linked to trusting oneself. This trust is given, I think, by appropriate love and education from generation through generation. That is, a very long work. may be some shortcut exists, but there is probably no universal simple recipe. Now with Godel we can say more, which is that good faith never fears reason and rationality. Sincere Faith can only extend Ratio, and is always open to dialog. It seems that there exists other conceptions of what good faith and/or Sincere Faith should be. Idem for Ratio. Which one? Bruno
Re: Dualism
At 15:38 16/01/04 -0500, Jesse Mazer wrote: Is Chalmers really a dualist? Although he does label his views this way at times, from his writings he does not seem to believe in matter per se, rather he thinks the fundamental stuff of reality is likely to be something like information which has both an objective description (a particular bit string, computation, whatever) and a subjective what-it-is-like to *be* that bit-string/computation/whatever. It seems to me that any formal mathematical theory of consciousness or of observer-moments must work the same way. If you want to have a mathematical theory that assigns measure to different observer-moments, for example, you need to have a mathematical framework for listing all possible observer-moments, perhaps something like treating each distinct computation (or any finite sequence of steps in a distinct computation) as a distinct observer-moment. And yet, even if I understand this mathematical framework, from the inside I will not be sure which of these formally-described observer-moments corresponds to my own current experience, the qualia that I am percieving at this moment. So just as in Chalmers' system, there is a difference between the objective mathematical description of an observer-moment and the subjective what-it-is-like-to-be of the observer-moment corresponding to that description. There's a case for calling this dualism, but also a case for labelling it as a monist theory, an eliminative spiritualism as you described it (although I'd prefer the label 'eliminative idealism', since 'spiritualism' has mystical connotations). So we agree completely (from a personal conversation with Chalmers I am not sure he would agree, but that is beside the point). What you say corresponds to the 1-3 distinction. You know I tend to make precise that distinction by the use of modal logic. (I mean the arithmetical modal logic, i.e; those who are defined from the Godelian self-reference). But I don't think a lot in this list adhere to dualist positions, but please correct me if I'm wrong). I think there are people on this list who *implicitly* hold dualist positions. There are a number of people who would use the following sort of procedure to find the first-person likelihood of experiencing a universe with a given set of properties: 1. First, find a measure on all universes, regardless of whether a given universe is capable of supporting complex observers 2. Then use the anthropic principle to take into account the idea that you're more likely to experience a universe with lots of observers than one with few or none, assuming each universe's measure is equal (see, for example, Hal Finney's post at http://www.escribe.com/science/theory/m5006.html on how to find the likelihood we will find ourself in a universe with no other intelligent life within communicating distance) If this is just taken as a heuristic procedure, in lieu some more fundamental procedure that does not involve two separate steps, then perhaps it need not be labeled dualist. But if this is really seen as the way the ultimate theory of everything would work, with no more fundamental theory to be found, then I think such a view is committed to a fundamentally dualist metaphysical view. Since I find dualism inelegant but I do think the anthropic principle has to be taken into account somehow, I prefer a TOE which only involves a measure on observer-moments rather than universes, with this measure determined by a theory that already takes into account the anthropic principle somehow (see my posts on the 'Request for a glossary of acronyms' thread at http://www.escribe.com/science/theory/index.html?by=OneThreadt=Request%20for%20a%20glossary%20of%20acronyms for some speculations on what such a theory would look like). I agree with you completely. Just replace anthropic by turing-tropic, and just accept that observer-moment are dual to the sheaves of comp histories going through those (first person) moment. In my thesis it is shown than at this stage the measure, ... well actually only the particular case of measure 1, will be extracted from the modal logics of those first person moments. It is there that I get a quasi-quantum logic (the one I called Z1*). I am not yet sure how *you are intending* to make precise the distinction between inside-view/outside-view, though. Perhaps I did not understood some of your point? By itself I am not convinced the anthropic way is enough. You can remind me other of your post perhaps? Bruno
Re: How to u-n-s-u-b-s-c-r-i-b-e
I hate u I have been trying to unsubscribe for weeks and it turns out nothing. pls unsubscribe me from your fucking list cause I don't wanna receive any message from U guys EVER Thank you! Silvia Axinescu - Original Message - From: Benjamin Udell [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, January 15, 2004 7:19 AM Subject: How to u-n-s-u-b-s-c-r-i-b-e Wei Dai's everything mailing list Webpage at http://www.eskimo.com/~weidai/everything.html has the instruction for unsubscribing oneself, as follows === To unsubscribe, please send an email with the subject unsubscribe to [EMAIL PROTECTED] === Members might consider moving this post to a separate folder for easy retrieval of contained information. - Original Message - From: Maragtas S.V. Amante [EMAIL PROTECTED] To: Moderator [EMAIL PROTECTED] Sent: Wednesday, January 14, 2004 11:09 PM Subject: Kindly unsubscribe please --- Connex scaneaza automat toate mesajele impotriva virusilor folosind RAV AntiVirus. Connex automatically scans all messages for viruses using RAV AntiVirus. Nota: RAV AntiVirus poate sa nu detecteze toti virusii noi sau toate variantele lor. Va rugam sa luati in considerare ca exista un risc de fiecare data cand deschideti fisiere atasate si ca MobiFon nu este responsabila pentru nici un prejudiciu cauzat de virusi. Disclaimer: RAV AntiVirus may not be able to detect all new viruses and variants. Please be aware that there is a risk involved whenever opening e-mail attachments to your computer and that MobiFon is not responsible for any damages caused by viruses. --- Connex scaneaza automat toate mesajele impotriva virusilor folosind RAV AntiVirus. Connex automatically scans all messages for viruses using RAV AntiVirus. Nota: RAV AntiVirus poate sa nu detecteze toti virusii noi sau toate variantele lor. Va rugam sa luati in considerare ca exista un risc de fiecare data cand deschideti fisiere atasate si ca MobiFon nu este responsabila pentru nici un prejudiciu cauzat de virusi. Disclaimer: RAV AntiVirus may not be able to detect all new viruses and variants. Please be aware that there is a risk involved whenever opening e-mail attachments to your computer and that MobiFon is not responsible for any damages caused by viruses.
Re: How to u-n-s-u-b-s-c-r-i-b-e
I'm not the moderator have no control over this list. The most appealing explanation of your problem is that you failed to follow the instructions properly. However if, despite sending an email with unsubscribe in the subject line to [EMAIL PROTECTED] , you remain subscribed, why haven't you tried going to the everything-list page at the address that I provided, where you would find the list moderator's email address? I'll save you the trouble. Wei Dai's email address is [EMAIL PROTECTED] . Why don't you write him a polite note saying that you have been unable to unsubscribe, that you would please like to be unsubscribed? If you have already done this have received no reply, then I would feel definite concern for Wei Dai hope that he's all right. Meanwhile, in that case, you might try learning enough about your browser to block messages coming from [EMAIL PROTECTED], or to block messages to you that are also cc'd TO the [EMAIL PROTECTED], or whatever it takes. If you are unable to accomplish this, perhaps you should consider giving up the use of computers. - Original Message - From: Silvia Axinescu [EMAIL PROTECTED] To: Benjamin Udell [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Monday, January 19, 2004 2:03 PM Subject: Re: How to u-n-s-u-b-s-c-r-i-b-e I hate u I have been trying to unsubscribe for weeks and it turns out nothing.pls unsubscribe me from your f*g list cause I don't wanna receive any message from U guys EVER Thank you! Silvia Axinescu - Original Message - From: Benjamin Udell [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, January 15, 2004 7:19 AM Subject: How to u-n-s-u-b-s-c-r-i-b-e Wei Dai's everything mailing list Webpage at http://www.eskimo.com/~weidai/everything.html has the instruction for unsubscribing oneself, as follows === To unsubscribe, please send an email with the subject unsubscribe to [EMAIL PROTECTED] === Members might consider moving this post to a separate folder for easy retrieval of contained information.
Corrected: How to u-n-s-u-b-s-c-r-i-b-e
I'm not the moderator have no control over this list. The most appealing explanation of your problem is that you failed to follow the instructions properly. However if, despite sending an email with unsubscribe in the subject line to [EMAIL PROTECTED] , you remain subscribed, why haven't you tried going to the everything-list page at the address that I provided, where you would find the list moderator's email address? I'll save you the trouble. Wei Dai's email address is [EMAIL PROTECTED] . Why don't you write him a polite note saying that you have been unable to unsubscribe, that you would please like to be unsubscribed? If you have already done this have received no reply, then I would feel definite concern for Wei Dai hope that he's all right. Meanwhile, in that case, you might try learning enough about your browser to block messages coming from [EMAIL PROTECTED], or to block messages to you that are also cc'd TO the [EMAIL PROTECTED], or whatever it takes. If you are unable to accomplish this, perhaps you should consider giving up the use of computers. - Original Message - From: Silvia Axinescu [EMAIL PROTECTED] To: Benjamin Udell [EMAIL PROTECTED]; [EMAIL PROTECTED] Sent: Monday, January 19, 2004 2:03 PM Subject: Re: How to u-n-s-u-b-s-c-r-i-b-e I hate u I have been trying to unsubscribe for weeks and it turns out nothing.pls unsubscribe me from your f*g list cause I don't wanna receive any message from U guys EVER Thank you! Silvia Axinescu - Original Message - From: Benjamin Udell [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Thursday, January 15, 2004 7:19 AM Subject: How to u-n-s-u-b-s-c-r-i-b-e Wei Dai's everything mailing list Webpage at http://www.eskimo.com/~weidai/everything.html has the instruction for unsubscribing oneself, as follows === To unsubscribe, please send an email with the subject unsubscribe to [EMAIL PROTECTED] === Members might consider moving this post to a separate folder for easy retrieval of contained information.
Re: Determinism - Mind and Brain
Would a artificial self-aware entity emerging from human technology represent mind? (depends on YOUR definition of mind, of course) - but self-aware? does that mean that if the program calls for some math-churning, the computer will say I rather play some Bach music now and does so? or would you assume in that (hard) AI to program EVERYTHING what a human (callable normal or derailed) might react by? We are back to the infinite time comp with unlimited memory. My limited little 'mind' does not go that far. John Mikes - Original Message - From: CMR [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, January 18, 2004 9:54 PM Subject: Re: Determinism - Mind and Brain
Re: Peculiarities of our universe
- Original Message - From: Fred Chen [EMAIL PROTECTED] To: Everything [EMAIL PROTECTED] Sent: Saturday, January 10, 2004 10:17 PM Subject: Re: Peculiarities of our universe One other scenario is that a civilization has indeed reached this pervasive state, but not in a form we'd readily recognize. They may be nano-lifeforms or microorganisms, for example. This is probably harder to believe because only so much complexity can be stored in such an organism, but you never know. Maybe you could have trillions of these nonolifeforms that are no more than the eyes and ears of one superintelligent being.
Re: Tegmark is too physics-centric
I don't think there are many intelligent beings per cubic Plank length in our universe at all! In fact, string theorists don't know how to get to the standard model from their favorite theory, yet they still believe in it. Simple deterministic models could certainly explain our laws of physics, as 't Hooft explains in these articles: Determinism beneath Quantum Mechanics: http://arxiv.org/abs/quant-ph/0212095 Quantum Mechanics and Determinism: http://arxiv.org/abs/hep-th/0105105 How Does God Play Dice? (Pre-)Determinism at the Planck Scale: http://arxiv.org/abs/hep-th/0104219 - Original Message - From: Kory Heath [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Sunday, January 18, 2004 1:15 PM Subject: Re: Tegmark is too physics-centric At 1/17/04, Hal Finney wrote: But let me ask if you agree that considering Conway's 2D Life world with simply-specified initial conditions as in your example, that conscious life would be extraordinarily rare? I certainly agree that it would be extraordinarily rare, in the sense that the size of the lattice would need to be very big, and the number of clock-ticks required would need to be very large. But big and large are such relative terms! Clearly, our own universe is very, very big. The question is, how can we sensibly determine whether life is more likely in our universe or in Conway's Life universe? I don't believe we have anywhere near enough data to answer this question, but I don't think it's unanswerable in principle. Fredkin actually believes that our universe is a 3+1D cellular automata, and if anyone ever found such a description of our physics (or some other fundamentally computational description), then we could directly compare it with Conway's Life, determining for each one how big the lattice needs to be, and how many clock-ticks are required, for life to appear with (say) 90% probability. (Of course, this determination might be difficult even when we know the rules of the CAs. But we can try.) One thing that you'd have to take into account is the complexity of the rules you're comparing, including the number of states allowed per cell. Not only are the rules to Conway's Life extremely simple, but the cells are binary. All things being equal, I would expect that an increase in the complexity of the rules and the number of cell-states allowed would decrease the necessary lattice-size and/or number of clock-ticks required for SASs to grow out of a pseudo-random initial state. I mention this to point out a problem with our intuitions about our universe vs. Conway's Life: the description of our universe is almost certainly more complex than the description of Conway's Life with a simple initial state. If Fredkin actually succeeds in finding a 3+1D CA which describes our universe, it will almost certainly require more than 2 cell-states, and its rules will certainly be more complex than those of the Life universe. We have to take this difference into account when trying to compare the two universes, but we have nowhere near enough data to quantify the difference currently. We really don't know what size of space in the Life universe is equivalent to (say) a solar system in this universe. In a way, this is all beside the point, since I have no problem believing that one CA can evolve SASs much more easily than some other CA whose rules and initial state are exactly as complex. (In fact, this must be true, since for any CA that supports life at all, there's an equally complex one that isn't even computation universal.) I have no problem believing that the Life universe is, in some objective sense, not very conducive to SASs. Perhaps it's less conducive to SASs than our own universe, although I'm not convinced. What I have a problem believing is that CAs as a class are somehow less conducive to observers than quantum-physical models as a class. In fact, I think it's substantially more likely that there are relatively simple CA models (and other computational models) that are much more conducive to SASs than either Conway's Life universe or our own. Models in which, for instance, neural-net structures arise much more naturally from the basic physics of the system than they do in our universe, or the Life universe. In many ways, our universe seems tailor made for creating observers. I understand this perspective, but for what it's worth, I'm profoundly out of sympathy with it. In my view, computation universality is the real key - life and consciousness are going to pop up in any universe that's computation universal, as long as the universe is big enough and/or it lasts long enough. (And there's always enough time and space in the Mathiverse!) When I think about the insane, teetering, jerry-rigged contraptions that we call life in this universe - when I think about the tortured complexity that matter has to twist itself into just to give us single-celled replicators - and when I
Re: Peculiarities of our universe
One other scenario is that a civilization has indeed reached this pervasive state, but not in a form we'd readily recognize. They may be nano-lifeforms or microorganisms, for example. This is probably harder to believe because only so much complexity can be stored in such an organism, but you never know. Maybe you could have trillions of these nonolifeforms that are no more than the eyes and ears of one superintelligent being. AKA: some distributed intelligence's smart dust?; geez there really isn't anything new under the sun!
Re: Corrected: How to u-n-s-u-b-s-c-r-i-b-e
I hate u I have been trying to unsubscribe for weeks and it turns out nothing.pls unsubscribe me from your f*g list cause I don't wanna receive any message from U guys EVER Thank you! Silvia Axinescu Guess somebody should have told her that she needed to unsubscribe in all possible universes to get off this list. Cheers
Re: Is the universe computable
I find it hard to believe that the measure of a
program/book/movie/experience is proportional to the number it is
executed/read/seen/lived, independently of everything else.
I have an alternative proposition:
Measure is a function of how accessible a particular
program/book/movie/experience is from a given observer moment.
More formally we can say that the measure of observer-moment B with
respect observer-moment A is the probability that observer moment B
occurs following observer moment A. Measure is simply a conditional
probability.
Thus, it is the probability of transition to the
program/book/movie that defines the measure. The actual number of
copies is meaningless.
This definition of measure has the advantage of conforming with
everyday experience. In addition, it is a relative quantity
because it requires the specification of an observer moment from which
the transition can be accomplished.
For example the measure of the book Digital Fortress is much
higher for someone who has read The Da Vinci Code than for
someone who hasn't, independently of how many copies of Digital
Fortress has actually been printed, or read and not understood, or
read and understood. (These books have the same author).
If one insists in using the context of program to define measure, than
one could define measure as the probability that program B be called as
a subroutine from another given program A, or more generally, from a
set of program A{}. The actual number of copies of the subroutine B is
meaningless. It is the number of calls to B from A{}that matters.
George Levy
Hal Finney wrote:
David Barrett-Lennard writes:
Why is it assumed that a multiple "runs" makes any difference to the
measure?
One reason I like this assumption is that it provides a natural reason
for simpler universes to have greater measure than more complex ones.
Imagine a Turing machine with an infinite program tape. But suppose the
actual program we are running is finite size, say 100 bits. The program
head will move back and forth over the tape but never go beyond the
first 100 bits.
Now consider all possible program tapes being run at the same time,
perhaps on an infinite ensemble of (virtual? abstract?) machines.
Of those, a fraction of 1 in 2^100 of those tapes will start with that
100 bit sequence for the program in question. And since the TM never
goes beyond those 100 bits, all such tapes will run the same program.
Therefore, 1/2^100 of all the executions of all possible program tapes
will be of that program.
Now consider another program that is larger, 120 bits. By the same
reasoning, 1 in 2^120 of all possible program tapes will start with that
particular 120-bit sequence. And so 1/2^120 of all the executions will
be of that program.
Therefore runs of the first program will be 2^20 times more numerous
than runs of the second.
