Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

A Brief Explanation of Greg Egan’s Dust Theory

cephalopods.blog

Post reply on HN
Print view View original

121–130 of 133 posts

Re: A Brief Explanation of Greg Egan’s Dust Theory

#121

Post by drdeca »

guscost wrote: post #119
drdeca wrote: post #115

Earlier quoted context omitted.

There is a difference between a mathematical object and a formal system. Surely you would not call a differential equation with a given initial condition describing a simple harmonic oscillator along with an initial condition “inconsistent”. Would you call it incomplete? Doing so would seem rather odd seeing as there is exactly one solution (given the initial condition). And the sense of “incomplete” that the incompl…

> Surely you would not call a differential equation with a given initial condition describing a simple harmonic oscillator along with an initial condition “inconsistent”. No, certainly not. > Would you call it incomplete? Yes, absolutely. There is no such thing as a harmonic oscillator that exactly follows an equation like that. Show me one. Either the formal system has nothing to do with the real world, or it is an…

> Either the formal system has nothing to do with the real world, or it is an incomplete approximation of it.

Ok, but this is a totally separate meaning of “incomplete” than what the incompleteness theorems are talking about.

So, if that is what you meant by “incomplete” in your original comment, you should know that your comment looked like it was appealing to Gödel’s incompleteness theorems, which do not deal with that sense of “completeness”.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#122

Post by scbrg »

athriren wrote: post #67
codethief wrote: post #41

Earlier quoted context omitted.

Thank you, that's the first intelligible explanation I've read here on this thread!

yeah, i was struggling too. egan’s books are too much for me because i feel like i need a highlighter and a graphing calculator, but i totally admire them and wish i was smarter.

I had the same feeling when reading some of them. In fact, you can just gloss over some of the parts that go to deep into maths or physics land. I did so, primarily with the Orthogonal Trilogy. You can enjoy the books even if some of the details are a bit too much.

Yeah, you have to live with feeling a bit stupid... but you don't have to tell anyone :-)

Re: A Brief Explanation of Greg Egan’s Dust Theory

#123

Post by Schiphol »

canjobear wrote: post #50

Very interesting to think about. Here's my interpretation of the argument: Suppose you have some system X whose dynamics are those of conscious agents in a world. For example, maybe X is the real world. Suppose that the agents in X really experience consciousness. Now suppose we apply some one-to-one function f to X, yielding Y = f(X). Then Y contains all the same information as X. So who's to say that the agents in…

I think the idea is thst you get to pick and choose from the 'dust': if you have a perfectly Kolmogorov-random string, it's still trivial to go jumping from one bit here to another it there like so: 10101010..., or in any other, however complicated pattern.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#124

Post by ajconway »

chr1 wrote: post #88
ajconway wrote: post #77

Earlier quoted context omitted.

If you believe in mathematical realism than the fact that there surely exists a mapping between a random set of data and a simulation with conscious agents in it, that should be enough.

It's not enough if the mapping function does not use the information from the random set. For instance it is easy to construct a mapping from ordered digits of pi to ordered letters of your comment, but all of the information of your comment will be in the mapping.

I believe the argument goes like this: assume that conscious agents can be simulated (that is, consciousness is computable). What is computation? If sudden wind arranges leaves on the ground into a pattern that looks like “2 + 2 = 4”, was there a computation? We would usually answer “no”, as computation, like many other things, requires causal connection. But Greg Egan states that “there is nothing more to causality than the correlations between states”.

Now, a deterministic simulation can be represented as a series of states recorded on a medium. Then you, an observer, can rewind and inspect what’s going on there, similar to reading a book or watching a movie. But the inhabitants of the simulation couldn’t care less about you observing their states. They already “exist”. In that case, why do we need the states of the simulation be recorded on the “film” in the order that makes sense for an outside observer? Surely a random arrangement would not affect the “simulation”. The same goes for the encoding.

Now, if the arrangement doesn’t matter, and the encoding doesn’t matter, why there needs to be a specific physical medium at all? Surely somewhere in the Universe you can find arrangements of “dust” that “encode” the same states (in no particular order).

Re: A Brief Explanation of Greg Egan’s Dust Theory

#125

Post by 3pt14159 »

jbotz wrote: post #71
3pt14159 wrote: post #57

Earlier quoted context omitted.

Almost a decade ago I independently invented the same idea. Discussion was here: https://news.ycombinator.com/item?id=2727750 It's a pretty simple theory, which I ultimately reject even to this day. If it were true, however, the expanse of existence is truly terrifying. This theory leads to any possible existence existing, short of maybe self-contradiction[0]. Well, so if that is true, then there exists a relation of…

> This theory leads to any possible existence existing, [...] This statement maybe superficially correct, but I interpret it differently. Every possible existence may exist, but not every imaginable existence. For something to exist in this manner, it has to be possible to generate it in a logically consistent manner from some initial conditions and simple rules, and while that allows for a "terrifying expanse of exi…

> it has to be possible to generate it in a logically consistent manner from some initial conditions and simple rules

Though I agree with the overall thrust of your response, I don't think it necessarily follows that an existence must be logically consistent, that it must be from some initial conditions, or that the rules must be simple.

First, an existence could be illogical to the beings within it. Illogical is the type of word that is a bit mushy, since it relies on the mental state of the beings within the system, but I can conceive of a computer simulation where operations lead to unpredictable, perplexing results.

Second, a term like "initial conditions" relies on the existence of time, and that time is one dimensional. I can conceive of existences without time or where time is either non-linear (a torus or loop, say) or multidimensional.

Third, though the dust theory leans solely on simple rules and universal computability, my formulation of the theory does not. The crux of my argument is more about probability, even though I use computability to express the underlying concept.

But I do agree with you that Infinity != Everything. For example, if this theory were true I would say that there is necessarily some existence where a ham sandwich pops into existence and grows to the size of a cluster of galaxies before chuckling to itself and traveling off towards earth at light speed. Or something even more ridiculous than that. Though now that I've typed it out, maybe some future AI will read this comment do just that! Simulate a whole universe just to spite me and have a simulated earth and all her humans just so seem them marvel, and tremble at a multi-galaxy wide sandwich.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#126

Post by db48x »

a1369209993 wrote: post #111
codethief wrote: post #21

Earlier quoted context omitted.

I would counter that by saying that: 1) this has nothing to do with computation. 2) my subjective experience is objectively there. No one questions what I am thinking. (That is, no one else looks inside my brain and claims: This is not what your thinking! ) My thoughts might be my own personal view and differ from other people's thoughts but their existence is not up for debate.

> my subjective experience is objectively there. Nitpick: you (or anyone else) don't actually have subjective experience; you have objective experience that some people mistakenly call subjective due to the practical difficulty of fully communicating it. Compare, eg someone claiming there is no objective truth about the[0] text of the Illiad on the basis that there are multiple equally valid ways of translating it in…

Whether one's internal experience is subjective or objective is not really germane to the book. Nobody can reach into another person's mind and grasp the totality of their experience, which makes it effectively subjective even if it is in principle objective.

What is relevant is that some minds have internal experiences which are correlated, and that correlation points to an objective reality. If I tell you that the sky is pink, and you look outside and see that it is actually black with white polka-dots, are we in different realities, is one of us a solipsist (meaning that the other doesn't even exist), is one of us insane, or are we just in different time zones? One of these explanations is simplest, of course, but the book is about the others.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#127

Post by chr1 »

ajconway wrote: post #124
chr1 wrote: post #88

Earlier quoted context omitted.

It's not enough if the mapping function does not use the information from the random set. For instance it is easy to construct a mapping from ordered digits of pi to ordered letters of your comment, but all of the information of your comment will be in the mapping.

I believe the argument goes like this: assume that conscious agents can be simulated (that is, consciousness is computable). What is computation? If sudden wind arranges leaves on the ground into a pattern that looks like “2 + 2 = 4”, was there a computation? We would usually answer “no”, as computation, like many other things, requires causal connection. But Greg Egan states that “there is nothing more to causality…

What does “encode” mean here? If it is supposed to contain the whole state in one chunk, the space of possible deterministic algorithms is too huge compared to the amount of dust, so it can't contain that. If it is supposed to find small chunks and rearrange them, it will not be using any information from the dust, and with same success encoder could use just any set of 0s and 1s. To circumvent finiteness of dust One could use digits of an irrational number or simple counting, but that is a very strange definition of existence. By that logic every possible history is just a number, so everything exists. The Important question is how to construct these numbers, find them in the sea of other meaningless numbers.

I think Stephen Wolfram's idea of computational irreducibility is very useful here. It says that most computations (even very simple systems like some of cellular automata) cannot be replaced by other computations, and even to verify that a number represents result of a computation, one have to carry out that same computation. So the part of the book where states of the simulation are computed out of order is simply wrong, the latter state of the simulation could not have been computed without computing the intermediate states, and all the methods of computing that state were equivalent to the person living through that interval of time.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#128

Post by saeranv »

canjobear wrote: post #50

Very interesting to think about. Here's my interpretation of the argument: Suppose you have some system X whose dynamics are those of conscious agents in a world. For example, maybe X is the real world. Suppose that the agents in X really experience consciousness. Now suppose we apply some one-to-one function f to X, yielding Y = f(X). Then Y contains all the same information as X. So who's to say that the agents in…

> One issue with this argument that hasn't been brought up yet is Kolmogorov complexity. Must random blobs of dust Z will be algorithmically random, not containing any real structure.

This is my issue as well, and something Greg Egan brings up in his FAQ on Dust theory as well. If my state is simply the result of a sampling of domain Y, why is my continuous state so stable? If we're assuming I'm sampling from a uniform (maximally random) distribution of potential states, there are many more state configurations where (for example) the physical laws should break down, then a stable configuration.

So there must be some missing element in Dust theory that explains away this randomness.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#129

Post by ajconway »

chr1 wrote: post #127
ajconway wrote: post #124

Earlier quoted context omitted.

I believe the argument goes like this: assume that conscious agents can be simulated (that is, consciousness is computable). What is computation? If sudden wind arranges leaves on the ground into a pattern that looks like “2 + 2 = 4”, was there a computation? We would usually answer “no”, as computation, like many other things, requires causal connection. But Greg Egan states that “there is nothing more to causality…

What does “encode” mean here? If it is supposed to contain the whole state in one chunk, the space of possible deterministic algorithms is too huge compared to the amount of dust, so it can't contain that. If it is supposed to find small chunks and rearrange them, it will not be using any information from the dust, and with same success encoder could use just any set of 0s and 1s. To circumvent finiteness of dust One…

You are still talking about mapping the simulation to a representation that will make sense to you.

The episode that I found fascinating to think about is when a simulated character reflects on his existence: “And if the computations behind all this had been performed over millennia, by people flicking abacus beads, would he have felt exactly the same? It was outrageous to admit it-but the answer had to be yes.”

It looks like the physical medium and the representation do not matter to the simulation, as long as computation occurs. Then the question is, what is computation. If you believe that all digits of Pi exist, then every possible computation should also exist.

We don’t usually believe that. It seems that information in our universe cannot exist without some physical medium.

The out of order computation was added to the story to make it more dramatic, the author states.

Re: A Brief Explanation of Greg Egan’s Dust Theory

#130

Post by chr1 »

ajconway wrote: post #129
chr1 wrote: post #127

Earlier quoted context omitted.

What does “encode” mean here? If it is supposed to contain the whole state in one chunk, the space of possible deterministic algorithms is too huge compared to the amount of dust, so it can't contain that. If it is supposed to find small chunks and rearrange them, it will not be using any information from the dust, and with same success encoder could use just any set of 0s and 1s. To circumvent finiteness of dust One…

You are still talking about mapping the simulation to a representation that will make sense to you. The episode that I found fascinating to think about is when a simulated character reflects on his existence: “And if the computations behind all this had been performed over millennia, by people flicking abacus beads, would he have felt exactly the same? It was outrageous to admit it-but the answer had to be yes.” It l…

>You are still talking about mapping the simulation to a representation that will make sense to you.

I am talking about mapping that will make sense to anybody at all, be that inside or outside the simulation. If such mapping cannot be constructed, then how can we state that information about these computations exists in dust?

The part about abacus is very good, but it is also very different from dust theory, since with abacus there is a process of computation, states are obtained one from another sequentially, and the positions of abacus beads are not random. In the case of dust the information about the simulation is clearly not contained in the dust, so it's unclear how dust can cause the simulation to exist.

> It seems that information in our universe cannot exist without some physical medium

isn't that simply due to the definition of the word exist?

Post reply on HN