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Universal machine

  1. Feb 17, 2009 #1
    There's a handful of cosmologists and QM types who claim "the universe computes".
    There's another crowd who insist this is rubbish - the universe isn't a computer.

    However, it certainly appears to be 'computational'; this is demonstrable: if we can write a program that simulates a real physical process (the gas laws, say), and do this for all of the processes we know about (so all the simulations then prove that we do know, if they exactly reproduce these processes in "computer-space", i.e. virtually), then a simulation of the known universe exists.

    If there is no actual physical computation (the universe we simulate is only our imaginary version of whatever it really is) then we should be able to write a program that demonstrates 'no physical computation exists', using a real physical computer, since the computer (we use to write the simulation) really isn't physical...

    See where this is going?

    Alternately, we should be able to write a program (on a real/imaginary computer) that proves "no computation occurs, the universe does not compute, it isn't computational". So why haven't we?
     
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  3. Feb 17, 2009 #2

    marcus

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    Name a few scientists in that crowd, please.

    I'd be interested in seeing links to actual articles by these people insisting that the universe is not a computer.
     
  4. Feb 17, 2009 #3
    Hmm. Well, I can't say I have found any that specifically deny it, or even argue why it isn't.

    I keep running into "crusty&old" types on forums who claim it's wrong, anytime I bring up the subject. I would guess they are only pseudo-cosmologists.

    Me, I'm a cosmologist who hasn't done any "real" study other than on my own.
     
  5. Feb 17, 2009 #4

    Vanadium 50

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    That's an interesting description. How does that differ from someone who is "interested in cosmology"?
     
  6. Feb 17, 2009 #5

    marcus

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    If I remember correctly there was a brief time like 2003-2005 when some in the professional research community tried thinking of the universe as a network of finite-state automata.
    Space was a network of cells, each cell was a computer of some simple sort.

    Then it seems like everybody lost interest. They found out some stuff. Proved some theorems. And moved on.

    Currently there seem to be other concepts getting more attention---other ways of imagining the most fundamental building blocks of reality and how they interact.

    That's just my impression. I could be wrong.

    As I recall the brightest most excited person in that bunch was
    Seth Lloyd. He's at MIT. You could look up his papers. I think they would be mostly 2004 and 2005. I think he has moved on to other stuff since then.
    Here's a sample 2005 paper of Lloyd's
    http://arxiv.org/pdf/quant-ph/0501135v8
    I never heard of anyone in the professional research community attacking the idea.
    It is, for a lot of people, just not the most interesting way to approach the fundamental nature of space, time, and matter.

    If something is not too interesting and just produces a few results, then people don't attack they just pay less attention.

    There is a new book coming out next month called Approaches to Quantum Gravity,
    Towards a New Understanding of Space, Time, and Matter
    . It will give a semi-up-to-date picture of the different research areas and which ideas are getting the attention now.
    You might check out the table of contents. It could even be that Seth or one of the other who pursued that idea has been included. The book is broadly inclusive of all the current approaches.
    http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=9780521860451
     
    Last edited: Feb 17, 2009
  7. Feb 17, 2009 #6
    Bingo - I "took on" his online course on QIS (I have a 1/2 postgrad in IS) and have only really started to think about the informational angle - which is kind of obvious if you've done any Optics lately, or EE (which I have), so uh huh, etc.

    Dr Lloyd led to various other online lecture notes, encoding anyon states and the Hall effect-AB link (if that's what it is) superconduction, trapped ion research.

    Eventually, if you've done any (real) IS, you have to ask yourself, "which part is the signal" when you look at QM.
     
  8. Feb 17, 2009 #7
    Well, there's forum stuff, like this, there's online lecture notes, then there's actual lectures, I suppose.
     
  9. Feb 17, 2009 #8
    I have this 'kind-of' model of spin as a 'smallest' potential that generates virtual particles; because spin is binary (and has a dual space in the EM field) we get a smallest process - which is a spin-flip.

    Because you have to have minimum 1 d.o.f. to flip something, the dual space has to occupy two others. The signal here is photon momentum or p, and a single flip in arbitrary t and s is a virtual photon, in spacetime. There's a Planck 'process' driving a background 'noise' that is a medium for transmission. the dual space has a dual transmission limit, overall transmission limit is then the interactions between background noise and the signal, or p.
     
  10. Feb 18, 2009 #9
    Re: Universal machine. Nature as a computer?

    Nature as a computer?

    Nature can not be calculating orbits. If it did, then there would have to be rounding off at certain significant number of digits; hence accumulated error and instability. Alternatively, if the calculation continued to any degree of accuracy, then the Turing tape (i.e. universal computing machine) would never end. http://en.wikipedia.org/wiki/Turing_machine" [Broken] So it would seem that nature has a geometric description for orbits; hence not a computer analogy.
     
    Last edited by a moderator: May 4, 2017
  11. Feb 18, 2009 #10

    Chronos

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    The computational model is attractive. The universe does appear to be mathematically consistent.
     
  12. Feb 18, 2009 #11
    A TM can't enumerate irrational numbers, but e.g. pi can be encoded - any exact geometrical number can be. But any TM, even a UTM, can only enumerate rationals. We can only rationalise the universe with TMs, but we can rationalise the TMs are complete.
     
  13. Feb 18, 2009 #12

    Chalnoth

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    Well, there is a fundamental difference between the basic building blocks of the universe acting as computers, and the universe as a whole acting as one. There is no question, really, that the universe as a whole does not act like a computer. There is also no question that at least certain parts of the universe do (i.e. computers).

    But do the fundamental building blocks act like very simple, interacting computers acting out a simple program? I would tend to suspect that any method of interaction between fundamental particles could be described in this way, so it sounds more like a potentially useful tool for understanding or calculating these interactions than a deep statement about the nature of reality.
     
  14. Feb 18, 2009 #13
    But there is so a question, that the universe is not a computer. When you say computers (the one you use to post in threads, e.g.), are you excluding things like chemistry, spectroscopy, instrumentation - oscilloscopes, counter-timers, voltmeters etc?

    The universal question is: Is the universe made of computers, and if so, is the universe also a computer?

    (translation: is the universe made of processes, and is the universe a process?)

    Alternately, can you write a program that gives a result = "the universe is not a computer?" (see OP)
     
  15. Feb 18, 2009 #14

    Chalnoth

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    There are a multitude of reasons why the universe as a whole does not act like a computer.

    One simple reason is that it is impossible for regions of the universe far enough away from one another to communicate.
     
  16. Feb 18, 2009 #15
    So these parts that can't communicate as far as we can define regions, imply that much of the universe isn't 'in' communication?

    But since it's expanding, the parts that are now "informationally separated", are the result of expansion = a process.
    Therefore, the result of this process = informationally separated parts of the universe, including all the parts that have expanded beyond an informational horizon at infinity"

    What you mean is, when you include real noise, communication is attenuated for a signal p.
    Attenuation is infinite for an infinite real noise = mass. Mass separated by a distance greater than the universal signal limit cannot communicate.
     
    Last edited: Feb 18, 2009
  17. Feb 18, 2009 #16
    It is impossible for people to communicate, but does that mean it is impossible for the universe to communicate? We cannot use entanglement for example to exchange information but maybe the universe can?
     
  18. Feb 18, 2009 #17

    Chalnoth

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    Entanglement doesn't exchange information.
     
  19. Feb 18, 2009 #18

    how do particles become entangled? Is it merely proximity? so since the universe was in the beginning a singularity does that mean all particles are quantum entangled? Doesn't seem to be so.

    Also....
    how are we defining what a computer is?
     
  20. Feb 18, 2009 #19
    We might consider entanglement as a kind of superposition; connections between mass (with intrinsic spin) that are 'distance-free', or fixed in time.
    Measurement appears here as an operator that fixes one end of a connection to a local frame; distance is then an operator that measures entanglement.

    Entanglement entropy is the weight of the connection(s) over a time interval of distances. Or the entropy is a distance measure which is time-independent.

    Although it can't exchange information, it is an exchange; in what degree of freedom though?
     
  21. Feb 18, 2009 #20

    Chalnoth

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    They undergo some interaction which forces them into a superposition of states where neither particle is in a definite state, but with a definite correlation.

    For example, if we examine the two electrons in the ground state of the helium atom, they are entangled: Both of the electrons are in a superposition of spin up and spin down, but the physics of being in the ground state necessitates that their spins be opposite. Therefore if we measure one to be spin up, a measurement of the other will necessarily generate spin down.


    The universe wasn't a singularity, though everything we observe today was once very close together. Either way, though, this doesn't mean that stuff far away is entangled, as entanglement is lost through interaction with the environment. In the above example with the helium atom in the ground state, for instance, once I've measured the spins of the two particles, they are no longer entangled, as the way in which I disturbed the electrons in order to obtain their spins messed that up.

    Well, in the most general sense, a computer is a device which takes some sort of input and produces an output. This is one reason why it's difficult to consider the universe as a whole as a computer: different regions become causally disconnected from one another, meaning that it's impossible to determine this "output".
     
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