10 ms·

Digital physics

62 points by xd 13y ago

ignostic 13y ago
This philosophy doesn't sit well with me. Physics at a particle or even mass scale can be described mathematically, I'll give you that. That said, if you are to understand the relationship between one particle and another, you need some way to explain that relationship. For example, the pull of one celestial body of matter on another (really the sum of particles, but let's simplify) can be explained with math. But you cannot communicate the RELATIONSHIP between the two without understanding the concept of gravity and space-time. It would be claiming the universe is all 1s and 0s, ignoring the fact that there must be a en/decoding method - a meaning to the numbers - for them to make any sense. The weaker claim that the universe CAN BE computed is to me fairly obvious, but that adds little to any discussion among those who believe in causality.
- TeMPOraL 13y ago
  What exactly is this "relationship"? Quarks dancing around in fields are quarks dancing around in fields, whether they together make planets or plants or something else is irrelevant to the laws of physics.
- aa0 13y ago
  I think you are misunderstanding what digital physics proposes. Yes the information is 0s and 1s but the actual program does not have to be. Physics is modeled by information and inherently seems to be connected to physical values. Seems logical to me.
  - ignostic 13y ago
    That may well be, as I'm not a physicist or mathematician. I take issue with the claim that the universe and the interactions therein can be described mathematically. That seems to imply that you can explain it to a human mathematically. Without context, concept, and relationship, how could this be?
    - aa0 13y ago
      Mathematics is just another flavor of language. English, French, Math...what's to doubt? Math just requires some extra context in the form of natural speech because it is a more narrow subset. It isn't limited, just less coherent when variables are used without prior definition. It's amusing that you find it hard for the universe to be described mathematically when physics does just that. I should note that digital physics does not imply that physics are purely mathematical..they can be procedural -- ie. akin to a C program. When you get down to it though..whatever is doing the higher level computation, the processor, could be accomplishing the instruction set using purely boolean logic.
    - deleted 13y ago
      [deleted]
    - chriswarbo 13y ago
      Something could be described Mathematically without it being explainable to a human: it could be vastly more complex than any person could ever comprehend. For example, every chess position can be enumerated, but no human can ever enumerate them all; although a Turing Machine could, given enough time and tape.
JonnieCache 13y ago
Greg Chaitin has lots of lectures about this up on youtube http://www.youtube.com/results?search_query=greg+chaitin http://www.youtube.com/results?search_query=greg+chaitin He is a very watchable speaker. There's an amusing moment in one of them where he talks about getting high on hyperoperators. I wish I could remember which one it was. Among other things he tries to convince you that real numbers are a figment of our imagination, an obvious consequence of digital physics, but still quite startling. He has decent arguments.
- chii 13y ago
  is there any one particular lecture you recommend? i don't have time to sift thru the large number of results from that search to find the gems.
  - JonnieCache 13y ago
    The one at lisbon and the one at Mälardalen university are good. They're all good as far as I can tell.
dchichkov 13y ago
That quote from John Archibald Wheeler [a doctoral advisor of Feynman] ... just beautiful: """ [...] it is not unreasonable to imagine that information sits at the core of physics, just as it sits at the core of a computer. (John Archibald Wheeler 1998: 340) It from bit. Otherwise put, every 'it'—every particle, every field of force, even the space-time continuum itself—derives its function, its meaning, its very existence entirely—even if in some contexts indirectly—from the apparatus-elicited answers to yes-or-no questions, binary choices, bits. 'It from bit' symbolizes the idea that every item of the physical world has at bottom—a very deep bottom, in most instances—an immaterial source and explanation; that which we call reality arises in the last analysis from the posing of yes–no questions and the registering of equipment-evoked responses; in short, that all things physical are information-theoretic in origin and that this is a participatory universe. (John Archibald Wheeler 1990: 5)
- deleted 13y ago
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aa0 13y ago
Chatlin's constant (http://en.wikipedia.org/wiki/Chaitin's_constant http://en.wikipedia.org/wiki/Chaitin's_constant), linked by Digital physics, is also very interesting. It is the probability that a random program will halt. When we get into 'random program' all kinds of interesting questions come up. For me, I immediately think of: What instruction set are we considering? Is the instruction set bounded by human language? Human language does not have the same extent as thought -- or does it? Is the indescribable as cardinal as the unthinkable? What is the Chatlin's constant for average human thought process.. ie. a subset of our brain programming? Man, what an interesting subject.
- chriswarbo 13y ago
  The instruction set doesn't matter. To calculate (the first few bits of) Chaitin's Constant we can enumerate and run every program in some instruction set, say x86 assembly, and measure the proportion of programs which eventually halt. One efficient way to do this is to interleave their executions using FAST http://www.idsia.ch/~juergen/toesv2/node28.html http://www.idsia.ch/~juergen/toesv2/node28.html Any (Turing-complete) instruction set can be translated/compiled/interpreted-by any other (Turing-complete) instruction set, given a suitable translator/compiler/interpreter. Since we're running all programs, we will eventually run all translators/compilers/interpreters, so no matter what instruction set we choose, we will start running programs from every other. The longer we leave it running, the more of a mixture we end up with. Since Chaitin's Constant is the (uncomputable) result of letting such a scheme run forever, it contains a perfect mixture of all instruction sets, and is thus independent of whichever one we choose.
- andyjohnson0 13y ago
  For a deep look at Omega (Chaitin's constant) I'd recommend Chaitin's book Meta Math: The Quest for Omega [1]. A fascinating book. Chaitin has also uploaded the full text (pdf) of the book to Arxiv.org [2]. [1] http://www.amazon.co.uk/Meta-Maths-Gregory-J-Chaitin/dp/184354525X/ref=sr_1_2?s=books&ie=UTF8&qid=1375795373&sr=1-2 http://www.amazon.co.uk/Meta-Maths-Gregory-J-Chaitin/dp/1843... [2] http://arxiv.org/abs/math/0404335 http://arxiv.org/abs/math/0404335
aa0 13y ago
Just a thought. If physical information is stored as bits in a computer. And the universe is essentially that memory plus a compute unit, Is consciousness the derivative of information with respect to the difference of information (ie. a clock cycle -- time?)
- eru 13y ago
  Almost probably not, at least not like that. You might like to read The User Illusion (http://www.amazon.com/The-User-Illusion-Cutting-Consciousness/dp/0140230122 http://www.amazon.com/The-User-Illusion-Cutting-Consciousnes...) for some more thought along these lines.
  - leod 13y ago
    I quite enjoyed The User Illusion (the author has a great way of looking at the world). I think its chapters on consciousness are mostly about what consciousness gets to see. Building up from the idea that there is a very limited amount of information (as in Shannon) going to consciousness per second, plus some other experimental evidence (e.g. Benjamin Libet's experiments), to his thesis that consciousness is essentially a "user illusion". But if I recall correctly, the book doesn't touch the question of how consciousness can arise to begin with, other than making a passing reference to GEB's strange loops. I can see some value, for example, in the idea that consciousness (maybe I should rather say subjective perception or awareness) somehow emerges out of a reasonably complex system. But that wouldn't explain what it is in our universe that allows awareness to emerge to begin with. I think some fun questions to think about are: * Can we create awareness in a circuit by making it complex enough? What are the requirements? * If we simulate a universe, does it inherit the ability to create awareness from our universe? * How the heck do you validate any of these answers? Well, I'm confused now, consciousness is too hard. Sorry if I sound like gibberish. EDIT: This isn't meant to be a criticism of the book, which I can only recommend to anyone.
    - bonobo 13y ago
      This idea that consciousness emerges from complexity is the study field of Giulio Tononi[1], and I find his point of view particularly interesting. This is not to say that we have something concrete in hands yet, but I like his approach nonetheless. [1] http://www.nytimes.com/2010/09/21/science/21consciousness.html?pagewanted=all http://www.nytimes.com/2010/09/21/science/21consciousness.ht...
mathattack 13y ago
It's intriguing, if perhaps an incorrect model. I am no physicist, but what makes us sure there's a bottom?
- chriswarbo 13y ago
  IMHO "bottom" is the point where any lower levels can only be pure philosophical speculation. For example, if we exist as a pure computation inside some computer, it makes no difference which of the myriad Turing-equivalent models it's based on, since they're all equivalent. Note that such a computer wouldn't have to be constrained by any of the Physics that apply inside our computation; ie. there don't need to be space or time limits.
  - mathattack 13y ago
    At the risk of sounding obtuse... When you say philosophical, do you mean non-measurable? (Such as parts of string theory?) To use an analogy, why can't particle physics be like a Mandelbrot which doesn't have a bottom?
virtualritz 13y ago
I just noticed the Process Physics article on WP has been deleted (because it is deemed fringe science by some) and isn't mentioned in there, even though this is very related, imho. http://www.flinders.edu.au/science_engineering/caps/staff-postgrads/info/cahill-r/process-physics/ http://www.flinders.edu.au/science_engineering/caps/staff-po...
iliis 13y ago
Nice to know there's a name for this concept! You can take the idea further and abandon any notion of time or even discreteness altogether: If the universe is essentially information, this information can be _completely_ described by some (mathemtical) language. Note, this description doesn't have to be finite. For the finite and discrete case this description may simply be a very long bitstring/vector which contains every detail of our universe. If time is discrete as well we can write a whole timeline as a matrix, a set of bitstrings each representing one slice of 'now'. Notice how we now have one static thing being a perfect representation of the universe. No need for a computer or interpreter. Just a big table of ones and zeroes representing everything from the big bang to your mother. However, our universe might be continuous. You might still be able to describe it with finite amount of information tough. A function like x -> x*x is continuous and defined for infinitiely many values but can still be written down just fine. Even infinite complex things like fractals can have a very short descriptions. Or take pi. An infinite sequence of numbers describable in a few sentences. Point is, a universe need not to be discrete in order to be written down on a sheet of paper. It just needs to be finite in an information theoretical sense. And you may need a lot of paper. I strongly suspect the universe is bounded. But what if it isn't? Can we still se it as a mathematical entitiy? I think so, but I'd like some comments on that. We have the well-defined set of real numbers and it contains _every_ real number, even those who are completely random up until the last of their infinite digit. There are numbers in R which have an infinite Kolmogorov complexity [1]. And yet, we can put them all in one set. We can even draw a picture of all these numbers (it's just a line, but that's more than our analysis professor would draw to illustrate something). In conclusion: I think (and didn't proof) that even if the universe contains infinite information and cannot be the result of some turing machine it can still be tought of as a mathematical object. A thing like sqrt(2) or a triangle. ---- A second and orthogonal tought is about the 'reality' of all this. This is a bit metaphysical and philosophical. If you are still reading please tell me I went crazy. The idea is, if you have a perfect description of our universe (be it a turing machine, a big matrix or some other complicated mathematical thingumabob) is there a difference between the description and the real thing? Obviously not, one is just words on a paper or bits in a computer and the other a world full of loving and caring people and other stuff. How can I even ask such a question? (Hint: I'm on the Internet and can write what I want.) Well, imagine doing this whole computer simulation of our universe. Would you feel any different when being run on some sort of computer? If you and everything around you would be perfectly simulated would you notice it? Would you even be able to? For the ones running the simulation the difference would be obvious. But being part of the simulation you may have no way of knowing that you are a piece of software. It would all seem and feel real. It would BE real. And yet you are just bits. You could stop the computer, dump it's memory and write it all down. Doesn't seem like such a difference between words on paper and reality after all. What I'm trying to explain is that a perfect description of something is actually, in some sense, the _same_ thing as the object being described. It's a bit like uploading the whole universe instead of just a brain. In the end all you have is information. Doesn't matter if this information flows trough transistors, is written in ink or just an element of the set of real numbers. And if you say the number '4' 'exists' and so does 'pi' then why not 'the universe' as well? If you say this then you just answered the question 'why do we exist?' Because _everything_ exists. In the same sense as every possible triangle 'exists' so does every universe. We just happen to observe one specific instance. The sad thing is: This doesn't really explain anything. If you say absolutely everything exists you haven't made any predictable or verifiable claim. So it may give you a philosophical answer to why are we here but it isn't much more than '42'... ---- [1] Some formal proof would be nice here. I didn't think it trough down to the simplest axiom. Maybe it's enough to argue that there are only countable many turing machines but uncountable many real numbers and therefore some real numbers cannot have a finite description.
ashleyw 13y ago
I'm certainly not qualified in this field, but I think it's inevitable that we as a species will eventually simulate a universe. And if that's the case, we've really got to ask whether we're a simulation ourselves. At the macro level this seemingly arbitrary universe makes a lot of sense, which makes me wonder if our universe is one in a long 'family' of simulated universes, each making modifications along the way, deliberate or otherwise, evolving towards the universe we have before us today (and beyond.) After all, once you have the computational power to simulate one universe, it'll not be long before you can simulate 10,000 simultaneously (..and only keep the fittest!)
- JonnieCache 13y ago
  Presumably you've read http://www.simulation-argument.com http://www.simulation-argument.com ? If not, then enjoy yourself.
  - ashleyw 13y ago
    No I haven't seen that, it's fantastic -- Thanks!
- bonobo 13y ago
  You might find this story quite interesting: http://qntm.org/responsibility http://qntm.org/responsibility
AsymetricCom 13y ago
hasnt this line of philosophy been logically killed by quantum physics? Also digits are purely human concept.
- pivnicek 13y ago
  I'm not sure if a digital universe would necessarily equate to a knowable universe. My main point of disagreement with the philosophy would lie in the ultimate weakness inherent to a digital explanation: the infinite points in between.
  - kaoD 13y ago
    Which infinite points? http://en.wikipedia.org/wiki/Planck_length http://en.wikipedia.org/wiki/Planck_length
- flumbaps 13y ago
  No, not really, quantum physics could be simulated using symbolic computation. Digits are not a purely human concept. They belong to mathematics, which is something that humans uncover, not invent.
  - AsymetricCom 13y ago
    I'm not really of persuasion that Math is the only way to understand and predict the universe. http://www.dailygalaxy.com/my_weblog/2008/04/is-mathematics.html http://www.dailygalaxy.com/my_weblog/2008/04/is-mathematics....
- marcosdumay 13y ago
  Aren't "digital" and "quantum" two names for the same concept? (But, no, quantum physics didn't settle on the quantization of all data.)
mkrecny 13y ago
Digital Digital Philosophy: "Digital philosophy grew out of an earlier digital physics (both terms are due to Fredkin), which proposes to ground much of physical theory in cellular automata." http://en.wikipedia.org/wiki/Digital_philosophy http://en.wikipedia.org/wiki/Digital_philosophy
helloTree 13y ago
As a computer scientist I like the idea as I also believe that information (and time or a unifying concept of them) is one of the most fundamental building blocks of the universe, however we have to keep in mind that we leave the territory of science here. The statement: "The universe is just a simulation." is just not a scientific theory as this is probably unfalsifiable [0] or am i wrong? [0] http://en.wikipedia.org/wiki/Falsifiability http://en.wikipedia.org/wiki/Falsifiability
- chriswarbo 13y ago
  Most digital physics proposals seem to be unfalsifiable, but there are exceptions. For example, statistical Physics tells us that a system can be full of complex, random fluctuations, but it can still be 'stable' if those fluctuations cancel each other out. Boltzmann hypothesised that we could just be a random fluctuation in some otherwise stable system (perhaps a vast cloud of gas). This hypothesis is falsifiable, since large fluctuations are far less likely than small fluctuations. It's very unlikely that the room I'm in, including me, is a fluctuation in a gas cloud, but the anthropic principle says that I wouldn't notice all those small fluctuations which don't produce me. If I am a fluctuation then I can predict that it's incredibly likely that the fluctuation is limited to this room, as anything larger would be far less likely. However, when I step outside I find a whole city, which falsifies the hypothesis. Likewise we can observe a whole planet, solar system, galaxy, local group, cosmic web, etc. which goes exactly against the predictions of the fluctuation hypothesis. However, from a digital physics perspective we can get the opposite result. Let's hypothesise that we're running on a giant Turing Machine and our program is a random fluctuation on its tape; ie. a random series of bit flips on an otherwise empty tape. Since small fluctuations are vastly more likely than large fluctuations, we would expect to be part of a small program rather than a large one. Again, the anthropic principle says that I'll never observe tiny programs that don't produce me, but what can I say about tiny programs which do produce me? Well, randomness and asymmetry is hard to produce using a computer program: it must be encoded as part of the program, since it can't be produced spontaneously. Hence I would predict small programs to have less randomness and asymmetry than large programs, so I would predict a symmetric and uniform Universe, which is largely what we see. One falsifiable prediction of such a digital physics theory is that quantum phenomena are actually pseudorandom, ie. deterministic and predictable, since the only way to encode unpredictable values in a program is to write them out bit-for-bit in the source. A pseudorandom number generator would require far fewer bits, and hence is more likely; also, a smaller pseudorandom number generator is more likely than a large one. If we find that quantum phenomena cannot be predicted by any short program, we can falsify this hypothesis.
DanielBMarkham 13y ago
I've believed in a "computational substrate" ever since I read Wolfram's NKS. Great to see it getting more attention. What with the holographic principle, it may be that the "real" universe in a huge sphere, and the effects we observe simply due to overlap. Sort of like Conway's Life played on a cosmic scale. Cool stuff.
dsizzle 13y ago
Conceiving the universe as the "output of a computer program" seems like an empty idea, as computation depends on a physical substrate (its laws of physics). It leads to an infinite regress: What laws of physics govern that physical substrate? David Deutsch (mentioned in the WP article) has a discussion of this (and many other related deep topics!) in his excellent "The Beginning of Infinity" http://www.amazon.com/The-Beginning-Infinity-Explanations-Transform/dp/0143121359 http://www.amazon.com/The-Beginning-Infinity-Explanations-Tr...

62 points by xd 13y ago

This philosophy doesn't sit well with me. Physics at a particle or even mass scale can be described mathematically, I'll give you that. That said, if you are to understand the relationship between one particle and another, you need some way to explain that relationship. For example, the pull of one celestial body of matter on another (really the sum of particles, but let's simplify) can be explained with math. But you cannot communicate the RELATIONSHIP between the two without understanding the concept of gravity and space-time. It would be claiming the universe is all 1s and 0s, ignoring the fact that there must be a en/decoding method - a meaning to the numbers - for them to make any sense. The weaker claim that the universe CAN BE computed is to me fairly obvious, but that adds little to any discussion among those who believe in causality.

TeMPOraL 13y ago
What exactly is this "relationship"? Quarks dancing around in fields are quarks dancing around in fields, whether they together make planets or plants or something else is irrelevant to the laws of physics.
aa0 13y ago
I think you are misunderstanding what digital physics proposes. Yes the information is 0s and 1s but the actual program does not have to be. Physics is modeled by information and inherently seems to be connected to physical values. Seems logical to me.
- ignostic 13y ago
  That may well be, as I'm not a physicist or mathematician. I take issue with the claim that the universe and the interactions therein can be described mathematically. That seems to imply that you can explain it to a human mathematically. Without context, concept, and relationship, how could this be?
  - aa0 13y ago
    Mathematics is just another flavor of language. English, French, Math...what's to doubt? Math just requires some extra context in the form of natural speech because it is a more narrow subset. It isn't limited, just less coherent when variables are used without prior definition. It's amusing that you find it hard for the universe to be described mathematically when physics does just that. I should note that digital physics does not imply that physics are purely mathematical..they can be procedural -- ie. akin to a C program. When you get down to it though..whatever is doing the higher level computation, the processor, could be accomplishing the instruction set using purely boolean logic.
  - deleted 13y ago
    [deleted]
  - chriswarbo 13y ago
    Something could be described Mathematically without it being explainable to a human: it could be vastly more complex than any person could ever comprehend. For example, every chess position can be enumerated, but no human can ever enumerate them all; although a Turing Machine could, given enough time and tape.

JonnieCache 13y ago

Greg Chaitin has lots of lectures about this up on youtube http://www.youtube.com/results?search_query=greg+chaitin http://www.youtube.com/results?search_query=greg+chaitin He is a very watchable speaker. There's an amusing moment in one of them where he talks about getting high on hyperoperators. I wish I could remember which one it was. Among other things he tries to convince you that real numbers are a figment of our imagination, an obvious consequence of digital physics, but still quite startling. He has decent arguments.

chii 13y ago
is there any one particular lecture you recommend? i don't have time to sift thru the large number of results from that search to find the gems.
- JonnieCache 13y ago
  The one at lisbon and the one at Mälardalen university are good. They're all good as far as I can tell.

dchichkov 13y ago

That quote from John Archibald Wheeler [a doctoral advisor of Feynman] ... just beautiful: """ [...] it is not unreasonable to imagine that information sits at the core of physics, just as it sits at the core of a computer. (John Archibald Wheeler 1998: 340) It from bit. Otherwise put, every 'it'—every particle, every field of force, even the space-time continuum itself—derives its function, its meaning, its very existence entirely—even if in some contexts indirectly—from the apparatus-elicited answers to yes-or-no questions, binary choices, bits. 'It from bit' symbolizes the idea that every item of the physical world has at bottom—a very deep bottom, in most instances—an immaterial source and explanation; that which we call reality arises in the last analysis from the posing of yes–no questions and the registering of equipment-evoked responses; in short, that all things physical are information-theoretic in origin and that this is a participatory universe. (John Archibald Wheeler 1990: 5)

deleted 13y ago
[deleted]

aa0 13y ago

Chatlin's constant (http://en.wikipedia.org/wiki/Chaitin's_constant http://en.wikipedia.org/wiki/Chaitin's_constant), linked by Digital physics, is also very interesting. It is the probability that a random program will halt. When we get into 'random program' all kinds of interesting questions come up. For me, I immediately think of: What instruction set are we considering? Is the instruction set bounded by human language? Human language does not have the same extent as thought -- or does it? Is the indescribable as cardinal as the unthinkable? What is the Chatlin's constant for average human thought process.. ie. a subset of our brain programming? Man, what an interesting subject.

chriswarbo 13y ago
The instruction set doesn't matter. To calculate (the first few bits of) Chaitin's Constant we can enumerate and run every program in some instruction set, say x86 assembly, and measure the proportion of programs which eventually halt. One efficient way to do this is to interleave their executions using FAST http://www.idsia.ch/~juergen/toesv2/node28.html http://www.idsia.ch/~juergen/toesv2/node28.html Any (Turing-complete) instruction set can be translated/compiled/interpreted-by any other (Turing-complete) instruction set, given a suitable translator/compiler/interpreter. Since we're running all programs, we will eventually run all translators/compilers/interpreters, so no matter what instruction set we choose, we will start running programs from every other. The longer we leave it running, the more of a mixture we end up with. Since Chaitin's Constant is the (uncomputable) result of letting such a scheme run forever, it contains a perfect mixture of all instruction sets, and is thus independent of whichever one we choose.
andyjohnson0 13y ago
For a deep look at Omega (Chaitin's constant) I'd recommend Chaitin's book Meta Math: The Quest for Omega [1]. A fascinating book. Chaitin has also uploaded the full text (pdf) of the book to Arxiv.org [2]. [1] http://www.amazon.co.uk/Meta-Maths-Gregory-J-Chaitin/dp/184354525X/ref=sr_1_2?s=books&ie=UTF8&qid=1375795373&sr=1-2 http://www.amazon.co.uk/Meta-Maths-Gregory-J-Chaitin/dp/1843... [2] http://arxiv.org/abs/math/0404335 http://arxiv.org/abs/math/0404335

aa0 13y ago

Just a thought. If physical information is stored as bits in a computer. And the universe is essentially that memory plus a compute unit, Is consciousness the derivative of information with respect to the difference of information (ie. a clock cycle -- time?)

eru 13y ago
Almost probably not, at least not like that. You might like to read The User Illusion (http://www.amazon.com/The-User-Illusion-Cutting-Consciousness/dp/0140230122 http://www.amazon.com/The-User-Illusion-Cutting-Consciousnes...) for some more thought along these lines.
- leod 13y ago
  I quite enjoyed The User Illusion (the author has a great way of looking at the world). I think its chapters on consciousness are mostly about what consciousness gets to see. Building up from the idea that there is a very limited amount of information (as in Shannon) going to consciousness per second, plus some other experimental evidence (e.g. Benjamin Libet's experiments), to his thesis that consciousness is essentially a "user illusion". But if I recall correctly, the book doesn't touch the question of how consciousness can arise to begin with, other than making a passing reference to GEB's strange loops. I can see some value, for example, in the idea that consciousness (maybe I should rather say subjective perception or awareness) somehow emerges out of a reasonably complex system. But that wouldn't explain what it is in our universe that allows awareness to emerge to begin with. I think some fun questions to think about are: * Can we create awareness in a circuit by making it complex enough? What are the requirements? * If we simulate a universe, does it inherit the ability to create awareness from our universe? * How the heck do you validate any of these answers? Well, I'm confused now, consciousness is too hard. Sorry if I sound like gibberish. EDIT: This isn't meant to be a criticism of the book, which I can only recommend to anyone.
  - bonobo 13y ago
    This idea that consciousness emerges from complexity is the study field of Giulio Tononi[1], and I find his point of view particularly interesting. This is not to say that we have something concrete in hands yet, but I like his approach nonetheless. [1] http://www.nytimes.com/2010/09/21/science/21consciousness.html?pagewanted=all http://www.nytimes.com/2010/09/21/science/21consciousness.ht...

mathattack 13y ago

It's intriguing, if perhaps an incorrect model. I am no physicist, but what makes us sure there's a bottom?

chriswarbo 13y ago
IMHO "bottom" is the point where any lower levels can only be pure philosophical speculation. For example, if we exist as a pure computation inside some computer, it makes no difference which of the myriad Turing-equivalent models it's based on, since they're all equivalent. Note that such a computer wouldn't have to be constrained by any of the Physics that apply inside our computation; ie. there don't need to be space or time limits.
- mathattack 13y ago
  At the risk of sounding obtuse... When you say philosophical, do you mean non-measurable? (Such as parts of string theory?) To use an analogy, why can't particle physics be like a Mandelbrot which doesn't have a bottom?

virtualritz 13y ago

I just noticed the Process Physics article on WP has been deleted (because it is deemed fringe science by some) and isn't mentioned in there, even though this is very related, imho. http://www.flinders.edu.au/science_engineering/caps/staff-postgrads/info/cahill-r/process-physics/ http://www.flinders.edu.au/science_engineering/caps/staff-po...

iliis 13y ago

Nice to know there's a name for this concept! You can take the idea further and abandon any notion of time or even discreteness altogether: If the universe is essentially information, this information can be _completely_ described by some (mathemtical) language. Note, this description doesn't have to be finite. For the finite and discrete case this description may simply be a very long bitstring/vector which contains every detail of our universe. If time is discrete as well we can write a whole timeline as a matrix, a set of bitstrings each representing one slice of 'now'. Notice how we now have one static thing being a perfect representation of the universe. No need for a computer or interpreter. Just a big table of ones and zeroes representing everything from the big bang to your mother. However, our universe might be continuous. You might still be able to describe it with finite amount of information tough. A function like x -> x*x is continuous and defined for infinitiely many values but can still be written down just fine. Even infinite complex things like fractals can have a very short descriptions. Or take pi. An infinite sequence of numbers describable in a few sentences. Point is, a universe need not to be discrete in order to be written down on a sheet of paper. It just needs to be finite in an information theoretical sense. And you may need a lot of paper. I strongly suspect the universe is bounded. But what if it isn't? Can we still se it as a mathematical entitiy? I think so, but I'd like some comments on that. We have the well-defined set of real numbers and it contains _every_ real number, even those who are completely random up until the last of their infinite digit. There are numbers in R which have an infinite Kolmogorov complexity [1]. And yet, we can put them all in one set. We can even draw a picture of all these numbers (it's just a line, but that's more than our analysis professor would draw to illustrate something). In conclusion: I think (and didn't proof) that even if the universe contains infinite information and cannot be the result of some turing machine it can still be tought of as a mathematical object. A thing like sqrt(2) or a triangle. ---- A second and orthogonal tought is about the 'reality' of all this. This is a bit metaphysical and philosophical. If you are still reading please tell me I went crazy. The idea is, if you have a perfect description of our universe (be it a turing machine, a big matrix or some other complicated mathematical thingumabob) is there a difference between the description and the real thing? Obviously not, one is just words on a paper or bits in a computer and the other a world full of loving and caring people and other stuff. How can I even ask such a question? (Hint: I'm on the Internet and can write what I want.) Well, imagine doing this whole computer simulation of our universe. Would you feel any different when being run on some sort of computer? If you and everything around you would be perfectly simulated would you notice it? Would you even be able to? For the ones running the simulation the difference would be obvious. But being part of the simulation you may have no way of knowing that you are a piece of software. It would all seem and feel real. It would BE real. And yet you are just bits. You could stop the computer, dump it's memory and write it all down. Doesn't seem like such a difference between words on paper and reality after all. What I'm trying to explain is that a perfect description of something is actually, in some sense, the _same_ thing as the object being described. It's a bit like uploading the whole universe instead of just a brain. In the end all you have is information. Doesn't matter if this information flows trough transistors, is written in ink or just an element of the set of real numbers. And if you say the number '4' 'exists' and so does 'pi' then why not 'the universe' as well? If you say this then you just answered the question 'why do we exist?' Because _everything_ exists. In the same sense as every possible triangle 'exists' so does every universe. We just happen to observe one specific instance. The sad thing is: This doesn't really explain anything. If you say absolutely everything exists you haven't made any predictable or verifiable claim. So it may give you a philosophical answer to why are we here but it isn't much more than '42'... ---- [1] Some formal proof would be nice here. I didn't think it trough down to the simplest axiom. Maybe it's enough to argue that there are only countable many turing machines but uncountable many real numbers and therefore some real numbers cannot have a finite description.

ashleyw 13y ago

I'm certainly not qualified in this field, but I think it's inevitable that we as a species will eventually simulate a universe. And if that's the case, we've really got to ask whether we're a simulation ourselves. At the macro level this seemingly arbitrary universe makes a lot of sense, which makes me wonder if our universe is one in a long 'family' of simulated universes, each making modifications along the way, deliberate or otherwise, evolving towards the universe we have before us today (and beyond.) After all, once you have the computational power to simulate one universe, it'll not be long before you can simulate 10,000 simultaneously (..and only keep the fittest!)

JonnieCache 13y ago
Presumably you've read http://www.simulation-argument.com http://www.simulation-argument.com ? If not, then enjoy yourself.
- ashleyw 13y ago
  No I haven't seen that, it's fantastic -- Thanks!
bonobo 13y ago
You might find this story quite interesting: http://qntm.org/responsibility http://qntm.org/responsibility

AsymetricCom 13y ago

hasnt this line of philosophy been logically killed by quantum physics? Also digits are purely human concept.

pivnicek 13y ago
I'm not sure if a digital universe would necessarily equate to a knowable universe. My main point of disagreement with the philosophy would lie in the ultimate weakness inherent to a digital explanation: the infinite points in between.
- kaoD 13y ago
  Which infinite points? http://en.wikipedia.org/wiki/Planck_length http://en.wikipedia.org/wiki/Planck_length
flumbaps 13y ago
No, not really, quantum physics could be simulated using symbolic computation. Digits are not a purely human concept. They belong to mathematics, which is something that humans uncover, not invent.
- AsymetricCom 13y ago
  I'm not really of persuasion that Math is the only way to understand and predict the universe. http://www.dailygalaxy.com/my_weblog/2008/04/is-mathematics.html http://www.dailygalaxy.com/my_weblog/2008/04/is-mathematics....
marcosdumay 13y ago
Aren't "digital" and "quantum" two names for the same concept? (But, no, quantum physics didn't settle on the quantization of all data.)

mkrecny 13y ago

Digital Digital Philosophy: "Digital philosophy grew out of an earlier digital physics (both terms are due to Fredkin), which proposes to ground much of physical theory in cellular automata." http://en.wikipedia.org/wiki/Digital_philosophy http://en.wikipedia.org/wiki/Digital_philosophy

helloTree 13y ago

As a computer scientist I like the idea as I also believe that information (and time or a unifying concept of them) is one of the most fundamental building blocks of the universe, however we have to keep in mind that we leave the territory of science here. The statement: "The universe is just a simulation." is just not a scientific theory as this is probably unfalsifiable [0] or am i wrong? [0] http://en.wikipedia.org/wiki/Falsifiability http://en.wikipedia.org/wiki/Falsifiability

chriswarbo 13y ago
Most digital physics proposals seem to be unfalsifiable, but there are exceptions. For example, statistical Physics tells us that a system can be full of complex, random fluctuations, but it can still be 'stable' if those fluctuations cancel each other out. Boltzmann hypothesised that we could just be a random fluctuation in some otherwise stable system (perhaps a vast cloud of gas). This hypothesis is falsifiable, since large fluctuations are far less likely than small fluctuations. It's very unlikely that the room I'm in, including me, is a fluctuation in a gas cloud, but the anthropic principle says that I wouldn't notice all those small fluctuations which don't produce me. If I am a fluctuation then I can predict that it's incredibly likely that the fluctuation is limited to this room, as anything larger would be far less likely. However, when I step outside I find a whole city, which falsifies the hypothesis. Likewise we can observe a whole planet, solar system, galaxy, local group, cosmic web, etc. which goes exactly against the predictions of the fluctuation hypothesis. However, from a digital physics perspective we can get the opposite result. Let's hypothesise that we're running on a giant Turing Machine and our program is a random fluctuation on its tape; ie. a random series of bit flips on an otherwise empty tape. Since small fluctuations are vastly more likely than large fluctuations, we would expect to be part of a small program rather than a large one. Again, the anthropic principle says that I'll never observe tiny programs that don't produce me, but what can I say about tiny programs which do produce me? Well, randomness and asymmetry is hard to produce using a computer program: it must be encoded as part of the program, since it can't be produced spontaneously. Hence I would predict small programs to have less randomness and asymmetry than large programs, so I would predict a symmetric and uniform Universe, which is largely what we see. One falsifiable prediction of such a digital physics theory is that quantum phenomena are actually pseudorandom, ie. deterministic and predictable, since the only way to encode unpredictable values in a program is to write them out bit-for-bit in the source. A pseudorandom number generator would require far fewer bits, and hence is more likely; also, a smaller pseudorandom number generator is more likely than a large one. If we find that quantum phenomena cannot be predicted by any short program, we can falsify this hypothesis.

DanielBMarkham 13y ago

I've believed in a "computational substrate" ever since I read Wolfram's NKS. Great to see it getting more attention. What with the holographic principle, it may be that the "real" universe in a huge sphere, and the effects we observe simply due to overlap. Sort of like Conway's Life played on a cosmic scale. Cool stuff.

dsizzle 13y ago

Conceiving the universe as the "output of a computer program" seems like an empty idea, as computation depends on a physical substrate (its laws of physics). It leads to an infinite regress: What laws of physics govern that physical substrate? David Deutsch (mentioned in the WP article) has a discussion of this (and many other related deep topics!) in his excellent "The Beginning of Infinity" http://www.amazon.com/The-Beginning-Infinity-Explanations-Transform/dp/0143121359 http://www.amazon.com/The-Beginning-Infinity-Explanations-Tr...