Re: Peculiarities of our universe
Why aren't we our own much smarter descendents? If you see quantum measurement events as 'uncovering' or 'choosing' from a larger set of, in some sense, pre-existing earlier possibilities, then this problem solves itself: the future looks 'bigger' than the present, but in terms of the real microstates, whatever they may be, it would be smaller. So your earliest observer moments would create a history of thermal, galactic, stellar, and biological evolution that traces back the shortest possible route to some sort of generic early universe condition with a very large measure. It is only the first of these evolutionary stages, explaining the origin of matter, that we do not yet understand. But I don't think we're to far off --Chris Collins - Original Message - From: Jesse Mazer [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Saturday, January 10, 2004 9:41 PM Subject: Re: Peculiarities of our universe One possibility for why we do not find ourself in an old, galaxy-spanning civilization has already been mentioned--perhaps after a certain point all the individual minds in a civilization unite into a single Borg-like hivemind, and this reduction in the number of minds might imply that the self-sampling assumption would predict we'll find ourselves in a time before this happens (although if the hivemind lasts for billions of years, the argument might not work because this individual mind would probably have more separate observer-moments than the total number of observer-moments of the hundred billion or so individuals who lived before the mind-merging). Another possibility is suggested by a theory about how the measure on observer-moments could be influenced by the likelihood of future duplications, which I discussed a bit in this post (in response to a post by Bruno Marchal discussing the same idea): http://www.escribe.com/science/theory/m4841.html If observer-moments which are more likely to have more copies of themselves existing in the future have higher measure, then this might also suggest why I find myself living before civilization has spread throughout the galaxy--perhaps observers who are alive right at the time when the technological singularity occurs are the ones who are most likely to become the earliest uploads and to have the most copies of themselves living in the future galaxy-spanning civilization, thus giving the pre-singularity versions of themselves a much higher measure than any post-singularity observer-moments. Jesse _ Learn how to choose, serve, and enjoy wine at Wine @ MSN. http://wine.msn.com/
Re: Peculiarities of our universe
Why don't we see Others? I think the anthropic principle neatly explains both scenarios: why we're here, yet nobody else seems to be. If life nucleation density is arbitrarily low (e.g. 1/visible univers) we still wouldn't fail to observe our existance. It is also worthwhile to mention that the deep universe is young, and hasn't yet bred sufficient amount of metals (in the astronomic, not the chemical sense), so due to delayed hatching we're not yet in the lightcone of an advanced culture. I.e., don't look at the visible universe without a probability bias, proportional but thresholded (no H/He life for sure). It is relatively straightforward to show that an advanced culture is expansive, in fact relativistically so, and everything past pioneer wave will be transformed to become unsuitable for an ursoup. Arguably, we're about to enter that expansive stage (notice that computational physics seem to allow cognition at a 10^6 speedup, so the time from zero to hero is less than a year), and we've only become observable within less than a century, the high-power emitters less than three decades. What's the probability to observe a 0.9 c pioneer expansion wavefront, which will kill subexpansive observers (observation window: about a century?), will prevent emergence of new observers, and will only start in systems with sufficient metallicity, with a yet unknown (yet probably very low) nucleation density? Arbitrarily close to zero, obviously. So I would be very, very surprised if SETI people actually found the sky hanging full of ~lighthour 300 K blackbodies, or even if we found independant life nucleation events within our solar system (which have to compete with impact ejecta crosscontamination, a very frequent event). pgp0.pgp Description: PGP signature
Strange Anthropic Probabilities
Hi all, I have a query about Tegmark's argument I hope some of you might be able to address. First, let me say I am not a physicist or computer science person but a humble sociologist with some lay physics knowledge on this topic. Let me also say I find it a morally ghastly proposition that each of us is duplicated an infinite number of times in an infinite number of universes. If so, why ever bother to do the right thing? Some infinite set of me's will be doing the wrong thing, so why not be one of them? So I have been thinking of possible counter considerations. Here is one: Is it possible that the parametric coincidences required for the existence of advanced (beyond microbial) life are so improbable that (i) even in the right kind of universe, advanced life is likely to occur only once; and (ii) it requires an infinite number of universes even to get one occurrence of a me-ish person? I am wondering whether probabilistically, (ii) is a coherent theoretical possibility. It seems to suggest a probability that would be represented as (1 / infinity) or perhaps as the limit as N goes to infinity of 1 / N. Then, according to this scenario (I think), the likelihood of a me-ish person is equal to the limit as N goes to infinity of N * (1 / N) = 1. As I say, I am just a sociologist, not a mathematician. So I don't know whether what I am suggesting is plain nonsense. It is certainly speculative, but no more so than Tegmark's scenario. Thanks for any feedback. doug -- doug porpora dept of culture and communication drexel university phila pa 19104 USA [EMAIL PROTECTED]
Re: Peculiarities of our universe
There has been a huge amount written about the Fermi Paradox (why are there no aliens) over the years, and I don't want to reiterate that here. You can come up with scenarios in which intelligent life is common but where they just aren't visible, but IMO such explanations are not very natural. Instead I propose that for the purpose of our discussion here, we accept the apparent fact that there are no other intelligent life forms within the visible universe. Then let us consider the implications with regard to the All Universe Hypothesis (AUH), which says that all universes exist. This observation points to the fact that with our laws of physics, the evolution of intelligent life is extremely unlikely. The question is, why? Not, why do our laws of physics make it hard for life to form, but why do we live in a universe whose laws of physics have this property? Presumably, there are universes whose laws make life essentially impossible. For example, they may be completely static, or equally bad, utterly chaotic. But on the other extreme, there must exist universes where intelligent life is common. At a minimum, we could create a such a universe in an ad hoc way by letting it be born full of intelligent life via forced initial conditions. And probably there are other laws of physics which would be much more congenial for the formation and sustenance of intelligent life than our own. So we have some universes which are full of life, others which are devoid of life, and others where there is a chance for life to form but it is relatively small. We appear to live in the third class. We talk about measure with regard to universes, and however it is defined, it seems that some such principle is needed to allow some universes to be more probable than others. Otherwise we have our flying rabbit paradox where the universe could suddenly stop being lawful, or could have arbitrary exceptions to lawfulness. Since there are more ways for things to go wrong than to go right, these exception-full universes would superficially be more numerous than those where the laws are universal. So there must be some property of the universal-law universes which makes it more probable for us to experience them than the others, and this is basically what we mean by measure. Universes with more measure somehow play a larger role in the multiverse and we are more likely to live in one of them. If universes with more consistent and uniform laws have greater measure, then this explains why we don't see exceptions like flying rabbits. However, it seems that the measure of a universe is not the only factor which should determine how likely it is to be observed; but in addition there should be a factor related to how many observers there are. The obvious case is for high-measure universes where observers are impossible. No one will observe such universes. This is the basic anthropic principle. But I would extend this principle to say that the probability of observing a universe is proportional to the product of its intrinsic measure and some factor relating to the number of observers in that universe. There are a few different ways this factor might work. The simplest would be to count the number of observers. A universe with similar measure but twice as many observers would be twice as likely to be experienced. Another possibility would be to use observer-moments. If two universes had the same number of observers, but in one they lived for twice as long as the other, then perhaps the second one would be twice as likely to be observed. Yet another alternative would be to base the factor on the fraction of the universe's total resources incorporated into observers, rather than just the number of observers. This would give a bonus to universes which were relatively efficient at creating observers, compared to universes which gained large numbers of observers merely be being inordinately large. The question of why we live in a sparsely populated universe, then, comes down to a comparison between the measure of a typical universe with many observers versus the measure of a typical universe with few. The former universes would get a large bonus factor for their many observers, while universes like ours don't have that. So for our observations to be consistent with the AUH, it must be that universes like ours have much larger intrinsic measure than universes with many observers. And since, as far as we can tell, our universe is not just sparsely populated, but extremely so, the measure differential in these two classes of universes must be extremely large. That is (turning to the Schmidhuber interpretation) it must be much simpler to write a program that just barely allows for the possibility of life than to write one which makes it easy. This is a prediction of the AUH, and evidence against it would be evidence against the AUH. On the face of it, this prediction doesn't seem too plausible to me. Of course, no one
Re: Strange Anthropic Probabilities
Doug Porpora writes: Let me also say I find it a morally ghastly proposition that each of us is duplicated an infinite number of times in an infinite number of universes. If so, why ever bother to do the right thing? Some infinite set of me's will be doing the wrong thing, so why not be one of them? I'll offer some thoughts on this below. So I have been thinking of possible counter considerations. Here is one: Is it possible that the parametric coincidences required for the existence of advanced (beyond microbial) life are so improbable that (i) even in the right kind of universe, advanced life is likely to occur only once; and (ii) it requires an infinite number of universes even to get one occurrence of a me-ish person? That would require that it is infinitely improbable that you could exist. But I don't think that is the case, because there are only a finite number of possible arrangements of matter of the size of a human being. (Equivalently, humans embody only a finite amount of information.) So it would seem that the probability of a human appearing in some universe must be finite and greater than zero, hence there would be an infinite number of instances across an infinity of universes. As far as the issue of human action and free will, here is how I look at it. There are really two issues. The first is that in some sense the multiverse makes our actions deterministic. That is, there is no longer any true unpredictability in what we do, because we do everything in one universe or another. So how can we have free will if there are no choices? Well, this problem has been considered many times in the philosophical literature going back hundreds of years (where it was asked how free will was compatible with God's omniscience). Recent works by Daniel Dennett, his books Elbow Room and his new book (which I haven't read) Freedom Evolves, discuss how free will can be said to coexist with determinism. The basic idea is that the acting out of deterministic processes and the considerations involved in making a free choice are two equally valid ways of explaining the same phenomenon, at different levels of description. These books could be good sources to explore these concepts further. The second part of the problem is specific to the multiverse model, which is, even assuming that in some sense you have free will, what is the practical point of acting, since your decisions will be in effect cancelled out by being done differently in other universes? Larry Niven's science fiction short story All the Myriad Ways explores the problems which sweep society when a technology is invented to visit parallel universes, leading to a widespread surrender to nihilism and social ennui. However this perspective ignores the concept of measure, where some universes are more prominent than others. Although you may make different choices in different universes, the probabilities are not equal. Your decision making processes influence the measure of the universes in which your different choices occur. By giving matters careful thought and making wise decisions, you can maximize the measure of the universes in which your choices have good outcomes. This justifies the necessity of careful choice and eliminates the descent into nihilistic horror and despair. Hal Finney
