--- On Wed, 9/3/08, Abram Demski <[EMAIL PROTECTED]> wrote: > From: Abram Demski <[EMAIL PROTECTED]> > Subject: Re: Computation as an explanation of the universe (was Re: [agi] > Recursive self-change: some definitions) > To: agi@v2.listbox.com > Date: Wednesday, September 3, 2008, 7:35 PM > Matt, I have several objections. > > First, as I understand it, your statement about the > universe having a > finite description length only applies to the *observable* > universe, > not the universe as a whole. The hubble radius expands at > the speed of > light as more light reaches us, meaning that the observable > universe > has a longer description length every day. So it does not > seem very > relevant to say that the description length is finite. > > The universe as a whole (observable and not-observable) > *could* be > finite, but we don't know one way or the other so far > as I am aware.
OK, then the observable universe has a finite description length. We don't need to describe anything else to model it, so by "universe" I mean only the observable part. > > Second, I do not agree with your reason for saying that > physics is > necessarily probabilistic. It seems possible to have a > completely > deterministic physics, which merely suffers from a lack of > information > and computation ability. Imagine if the universe happened > to follow > Newtonian physics, with atoms being little billiard balls. > The > situation is deterministic, if only we knew the starting > state of the > universe and had large enough computers to approximate the > differential equations to arbitrary accuracy. I am saying that the universe *is* deterministic. It has a definite quantum state, but we would need about 10^122 bits of memory to describe it. Since we can't do that, we have to resort to approximate models like quantum mechanics. I believe there is a simpler description. First, the description length is increasing with the square of the age of the universe, since it is proportional to area. So it must have been very small at one time. Second, the most efficient way to enumerate all possible universes would be to run each B-bit machine for 2^B steps, starting with B = 0, 1, 2... until intelligent life is found. For our universe, B ~ 407. You could reasonably argue that the algorithmic complexity of the free parameters of string theory and general relativity is of this magnitude. I believe that Wolfram also argued that the (observable) universe is a few lines of code. But even if we discover this program it does not mean we could model the universe deterministically. We would need a computer larger than the universe to do so. > Third, this is nitpicking, but I also am not sure about the > argument > that we cannot predict our thoughts. It seems formally > possible that a > system could predict itself. The system would need to be > compressible, > so that a model of itself could fit inside the whole. I > could be wrong > here, feel free to show me that I am. Anyway, the same > objection also > applies back to the necessity of probabilistic physics: is > it really > impossible for beings within a universe to have an accurate > compressed > model of the entire universe? (Similarly, if we have such a > model, > could we use it to run a simulation of the entire universe? > This seems > much less possible.) There is a simple argument using information theory. Every system S has a Kolmogorov complexity K(S), which is the smallest size that you can compress a description of S to. A model of S must also have complexity K(S). However, this leaves no space for S to model itself. In particular, if all of S's memory is used to describe its model, there is no memory left over to store any results of the simulation. > > --Abram > > > On Wed, Sep 3, 2008 at 6:45 PM, Matt Mahoney > <[EMAIL PROTECTED]> wrote: > > I think that computation is not so much a metaphor for > understanding the universe as it is an explanation. If you > enumerate all possible Turing machines, thus enumerating all > possible laws of physics, then some of those universes will > have the right conditions for the evolution of intelligent > life. If neutrons were slightly heavier than they actually > are (relative to protons), then stars could not sustain > fusion. If they were slightly lighter, then they would be > stable and we would have no elements. > > > > Because of gravity, the speed of light, Planck's > constant, the quantization of electric charge, and the > finite age of the universe, the universe has a finite length > description, and is therefore computable. The Bekenstein > bound of the Hubble radius is 2.91 x 10^122 bits. Any > computer within a finite universe must have less memory than > it, and therefore cannot simulate it except by using an > approximate (probabilistic) model. One such model is quantum > mechanics. > > > > For the same reason, an intelligent agent (which must > be Turing computable if the universe is) cannot model > itself, except probabilistically as an approximation. Thus, > we cannot predict what we will think without actually > thinking it. This property makes our own intelligence seem > mysterious. > > > > An explanation is only useful if it makes predictions, > and it does. If the universe were not Turing computable, > then Solomonoff induction and AIXI as ideal models of > prediction and intelligence would not be applicable to the > real world. Yet we have Occam's Razor and find in > practice that all successful machine learning algorithms use > algorithmically simple hypothesis sets. > > > > > > -- Matt Mahoney, [EMAIL PROTECTED] > > > > --- On Wed, 9/3/08, Terren Suydam > <[EMAIL PROTECTED]> wrote: > > From: Terren Suydam <[EMAIL PROTECTED]> > > Subject: Re: [agi] Recursive self-change: some > definitions > > To: agi@v2.listbox.com > > Date: Wednesday, September 3, 2008, 4:17 PM > > > > > > Hi Ben, > > > > My own feeling is that computation is just the latest > in a series of technical metaphors that we apply in service > of understanding how the universe works. Like the others > before it, it captures some valuable aspects and leaves out > others. It leaves me wondering: what future metaphors will > we apply to the universe, ourselves, etc., that will make > computation-as-metaphor seem as quaint as the old clockworks > analogies? > > > > I believe that computation is important in that it can > help us simulate intelligence, but intelligence itself is > not simply computation (or if it is, it's in a way that > requires us to transcend our current notions of > computation). Note that I'm not suggesting anything > mystical or dualistic at all, just offering the possibility > that we can find still greater metaphors for how > intelligence works. > > > > Either way though, > > I'm very interested in the results of your work - > at worst, it will shed some needed light on the subject. At > best... well, you know that part. :-] > > > > Terren > > > > --- On Tue, 9/2/08, Ben Goertzel > <[EMAIL PROTECTED]> wrote: > > From: Ben Goertzel <[EMAIL PROTECTED]> > > Subject: Re: [agi] Recursive self-change: some > definitions > > To: agi@v2.listbox.com > > Date: Tuesday, September 2, 2008, 4:50 PM > > > > > > > > On Tue, Sep 2, 2008 at 4:43 PM, Eric Burton > <[EMAIL PROTECTED]> wrote: > > > > I really see a number of algorithmic breakthroughs as > necessary for > > > > the development of strong general AI > > > > I hear that a lot, yet I never hear any convincing > arguments in that regard... > > > > So, hypothetically (and I hope not insultingly), > > I tend to view this as a kind of unconscious > overestimation of the awesomeness of our own > > > > species ... we feel intuitively like we're doing > SOMETHING so cool in our brains, it couldn't > > possibly be emulated or superseded by mere algorithms > like the ones computer scientists > > have developed so far ;-) > > > > > > ben > > -- Matt Mahoney, [EMAIL PROTECTED] ------------------------------------------- agi Archives: https://www.listbox.com/member/archive/303/=now RSS Feed: https://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: https://www.listbox.com/member/?member_id=8660244&id_secret=111637683-c8fa51 Powered by Listbox: http://www.listbox.com
