Via the Zeitgeister, a fun panel discussion at the Perimeter Institute between Seth Lloyd, Leonard Susskind, Christopher Fuchs and Sir Tony Leggett, moderated by Bob McDonald of CBC Radio’s Quirks & Quarks program. The topic is “The Physics of Information,” and as anyone familiar with the participants might guess, it’s a lively and provocative discussion.
A few of the panel members tried to pin down Seth Lloyd on one of his favorite catchphrases, “The universe is a computer.” I tackled this one myself at one point, at least half-seriously. If the universe is a computer, what is it computing? Its own evolution, apparently, according to the laws of physics. Tony Leggett got right to the heart of the matter, however, by asking “What kind of process would not count as a computer?” To which Lloyd merely answered, “Yeah, good question.” (But he did have a good line — “If the universe is a computer, why isn’t it running Windows?” Insert your own “blue screen of death” joke here.)
So I tried to look up the definition of a “computer.” You can open a standard text on quantum computation, but “computer” doesn’t appear in the index. The dictionary is either unhelpful — “a device that computes” — or too specific — “an electronic device designed to accept data, perform prescribed mathematical and logical operations at high speed, and display the results of these operations.” Wikipedia tells me that a computer is a machine that manipulates data according to a list of instructions. Again, too specific to include this universe, unless you interpret “machine” to mean “object.”
I think the most general definition of “computer” that would be useful is “a system that takes a set of input and deterministically produces a set of output.” The big assumption being that the same input always produces the same output, but I don’t think that’s overly restrictive for our present purposes. In that sense, the laws of physics act as a computer: given some data in the form of an initial configuration, the laws of physics will evolve the configuration into some output in the form of a final configuration. Setting aside the tricky business of wavefunction collapse, you have something like a computer. I suppose you could argue about whether the laws of physics are “the software” or the computer itself, but I think you are revealing the limitations of the metaphor rather than learning something interesting.
But if we take the metaphor at face value, it makes more sense to me to think of the universe as a calculation rather than as a computer. We have input data in the form of the conditions at early times, and the universe has calculated our current state. It could have been very different, with different input data.
And what precise good does it do to think in this way? Yeah, good question. (Which is not to imply that there isn’t an answer.)
Can we make any predictions from that “Universe is a computer” idea?
If all the randomness is pseudo-randomness then the random routine should start repeating the same random sequence. Can we see it somehow? Is repeating the history an evidence? I do not think so. What if that random sequence is rather short, would it help to discover it?
If the universe is a computer and there is a “quantum” of time when nothing changes. Can we somehow sense it? Can we somehow protect a word from being changed by the universe?
Can we test somehow if the world is in fact deterministic? I would say no. Anyone? 😉
If we fail to come up with any prediction, even a crazy one, I am afraid the idea to see the universe as a computer if not that interesting. ;(
Pingback: No numerable · El universo, ¿computadora o computación?.
Pingback: » El universo, ¿computadora?, ¿computación?, ¿o qué?. deUgarte.com
Pingback: Is the Universe a Computer? at Orbiting Frog
For what I can see from the past discussion, I seams that most people commenting here is confusion the question “is the universe a computer”, with other aspects like “is it useful?” or “what is it computing”. Not every computer needs to be useful, not its computation intelligible to us.
The is an underlying question which is: If it is a computer, is it a self replicating computer? a computer built by an external entity? or an emergent computer that became a computer as part of it’s evolution? or …fill in the blank…?
There can’t be any outside forces acting on the universe as a whole (by definition). So, if the universe is running a program, it has to come from within. We don’t have any examples of programs that evolved completely within a system. Even the genetic code was acted upon and optimized by forces outside the system (life). So, perhaps a better question is – are any parts of the universe a computer?
Of course, if the universe were a computer, we would try to find the program which would be the most concise description of the universe (isn’t that what we are doing while looking for a theory of everything?).
It makes more sense to say the universe is conscious. It would give you the same result, a self-motivated universe would “behave” the same as a programed universe, but you wouldn’t need an outside force or programmer.
There can’t be any outside forces acting on the universe as a whole (by definition).
Nope, this is the sometimes-called (IIRC, but fallacy in any case) analytical fallacy – you wrongly take the inner content or insinuation of a term or even phrase that has become used by custom to draw unwarranted conclusion. Just because we call this thing out here “the universe” does not mean there aren’t others or something else. You can say that we *shouldn’t* call this “the universe” or even “a universe” which sounds contradictory, but once a name becomes useful and habitual, it is usually too late to force a change to a more “appropriate” designation. That’s the breaks, and you should realize that to avoid similar misconstructions.
I do dig your idea of the “universe” being conscious, albeit very hard to get a handle on. Look into some exotic quantum philosophy diversions by John A. Wheeler et al on this.
tyrannogenius
Regarding the question:
“What kind of process would not count as a computer”
A process which cannot be effectively simulated by a computer would not count as a computer. So if you propose a physics theory based on things that are uncomputable it is probably false.
(The very precise scope of “effectively computed” is still a little disputed.)
On the positive side, processes that can be described by general computational models are potentially more complex and may allow richer modeling power than standard physics models. (If this is useful is left to be seen.)
Pingback: No numerable · El universo, ¿computadora?, ¿computación?, ¿o qué?.
@59 NeilB,
Zurek:
DECOHERENCE, EINSELECTION,
AND THE QUANTUM ORIGINS OF THE CLASSICAL
arXiv:quant-ph/0105127 v3
Meanwhile, Dennis Overbye asks if cosmology has jumped the shark…
The above is kind of off-topic, but hey, we’re talking about whether the universe can be regarded as a computer.
(Actually, I think this notion can be very fruitful, if get the right handle on it. We don’t have it yet. Further elaboration will not fit in a blog comment…)
Uhm, nobody is pretending that the universe is like the pc you are using now! A computer is an abstract mathematical device to analyze certain processes. I’m not an expert but from what I know, nothing in the concept of a computer implies an external source.
Also, there is a nice example of self-generated “computers”: the life itself, at least according to Maturana and others.
“Uhm, nobody is pretending that the universe is like the pc you are using now! A computer is an abstract mathematical device to analyze certain processes. I’m not an expert but from what I know, nothing in the concept of a computer implies an external source.”
But, if we live in a quantum world, bounded by human intelligence, will not the computer accelerate the growth of human consciousness??
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 would never end. So it would seem that nature has a geometric description for orbits; hence not a computer analogy.
Pingback: The basic dichotomy of quantum gravity « Shores of the Dirac Sea
Pingback: The universe is probably not a quantum computer « Shores of the Dirac Sea
Why are people always searching for an alternative to the obvious?
I want you to think of a dream. In that dream you created things. If you have vivid dreams like me and many others your dreams contain objects that are solid, have weight, and operate–sometimes defying the laws of physics.
God gave us dreams to allow us to see how THOUGHT itself can create. The universe is not a computer program–it is pure thought. It actually has no substance–just as your dream actually has no substance although you could swear it does while your asleep. Is yellow really bright? Not to someone without eyes. Is rock really hard? Not to someone without a body. In a sense you could think of what God created as some type of program, in that rock is programmed to feel hard to us–but just as when you dream the rock is just thought.
The universe is sustained by God’s thought. If you wanted you dead he would not have to kill you–he could simply stop thinking of you. But unlike our dreams God has given that which he creates much independence. It can operate apart from him and has real life of its own. But make no mistake it resides in God’s thought–not in any physical place.
Scientists often state that miracles are impossible because of the laws of physics. But those laws were set by God and are just as meaningless as those laws are in our dreams. To turn water into wine, or to raise Christ is just as easy as it is in our dreams for God. Its no feat–its no miracle for him. The real miracle is that we invent new ways of denying him. In our arrogance we uncreate the one who created life. You have to really work to deny something so obvious. No mathematician in the world can reconcile the universe with the laws of probablity–and thats the *Result of the universe—its not even taking into account that it must have Laws to even begin running the program. A child can see the odds cannot be beat–Plus, the odds of something coming out of nothing in a spacetime universe are not even odds–they are Zero. God is not in Spacetime–it was his idea.
Like a child, and not like a know it all, ask Him tonight if Christ was real–and if he is— you will trust him—do that tonight and God promises he will not leave such an innocent heart in disbelief. Its not about a fact finding mission, a detective story–its about God revealing the truth to you supernaturally. Then you will really get a chance to experience the entire universe forever.
Dont think a witty retort—a clever response that you can impress yourself with–just ask God.