Henrik,

How big is the universe? Its size, specs? Is it finite or not? Sayng we need a computer or another universe just like this one to answer those questions is no answer. It means we dont know. Kind of like we dont actually know the universe is Deterministic but it suits humans to think of it that way. Like we say "if we knew all initial conditions". Well we dont know all initial conditions. So we are faced with a huge contradiction between our idealistic vision of a Deterministic universe and the reality of the matter which is that Nature is loathe to give up all her secrets.

All through the ages humanity has been chasing the dream of certainty akin to peeling an onion with infinite layers of skin. Each time we think we have arrived at the kernel, another factor - known or unknown - pops up to spoil the party.

In my opinion nature is making the more important statement. It is saying the universe is ultimately non-deterministic because we wont ever know all initial conditions and hence we can not know whether each and every influence upon our universe is Determinstic or not. How can we say we know the nature of something we can not measure or observe? Claiming the universe is Determinstic is doing such, and by extension it is trying to tell nature how it should behave as opposed to accepting it as it is.

However i dont see it as a failure or that it should in any way stop us from trying to make better and better approximations, and peeling back as many skins as possible. Life is an adventure and who knows what's under the next onion layer?

Another onion layer...

It's turtles all the way down.

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.

Or maybe like the story "He who shrank" by Henry Hasse. The protagonist begins to shrink. When he reaches the subatomic level, it corresponds to a another universe, he continues to shrink and reaches a planet. Shrinking further, he again reaches the subatomic level, to find yet another universe. This goes on ad infinitum...

Perhaps the tower is built upon our emotional and instinctual demand for certainty and security? One could argue the whole tower of turtles paradox is a human-centric frustration. Does nature care? I dont think so. If numbers are universal, even a simple infinite set of numbers, may be representative of nature's own tower of turtles.

And if nature insists on turtles all the way down for some components of the universe it doesnt mean everything is turtles all the way down. Perhaps the HUP is the closest we can get to certainty from a predictive perspective. If that is so then what is wrong with it? I cant see what the big hoo-ha is about that. Quantum mechanics is said to be the most proven and unfalsified physcial theory we have. Maybe i heard wrong.

However the old argument "if we knew all intial conditions" is pretty non-sensical if that is considered some sort of proof of an ultimately determinstic universe. HUP is clearly telling us we can not know..for whatever reasons. WE cant even properly solve the n body problem, so the premise we can predict future physcial configurations in the universe based solely on a conditional IF statement is pretty laughable. We are good at comedy though :-)

I think the problem here is that we have forgotten the proper order of logic in science. We invent concepts like "determinism" because they serve a particular model of reality. At what point does our invention transcend the models and become a part of reality itself? At no point. So it is just arse-backwards to say, "hmmm, reality does not always appear to obey our invention of determinism, therefore it must really be deterministic in ways we haven't figured out yet or can't apply in practice." It might be true, or it might not, and it is fine to look for determinism once we have established the usefulness of the concept. But to do anything more than look for it, to assert it is there and we simply haven't found it yet, is simply awful science-- and that was true even before the HUP.

Ken,

"I think the problem here is that we have forgotten the proper order of logic in science. We invent concepts like "determinism" because they serve a particular model of reality. At what point does our invention transcend the models and become a part of reality itself? At no point. So it is just arse-backwards to say, "hmmm, reality does not always appear to obey our invention of determinism, therefore it must really be deterministic in ways we haven't figured out yet or can't apply in practice." It might be true, or it might not, and it is fine to look for determinism once we have established the usefulness of the concept. But to do anything more than look for it, to assert it is there and we simply haven't found it yet, is simply awful science-- and that was true even before the HUP."

Totally agree with everything you wrote. One of the reasons i've always been very skeptical of the whole Deterministic concept is that the universe seems to work fine without us having to know all initial conditions. If QM works well enough without certainty then what more value or usefulness would certainty add if it was available? Would there be a material difference? Could we do things that we could not do with copenhagen non-deterministic qm?

Perhaps someone with the knowledge can answer that. If there is some differential ability set loose by a Determinsitic qm, then its absence in the non-determinstic qm variety might explain some things. However if there is no material change to science or our practical ability to manipulate the universe through an observationally Determinsitic model of qm; then i think that rules out Bohmian or other hidden variables theories. If a particle has defined properties on some other deeper level than the HUP and it made no material difference to the universe there would seem no rational reason for it to be hidden from us, or from some other enquiring emergent biolgy. Why go through the hassle of complicating or masking the true - though unimportant - nature of the universe?

Yeah, and one can ask if the universe even "knows" its own initial conditions. Just how much information can fit in one universe anyway? Why should it need an infinity of information just to function? Nothing else seems to.Right-- it's almost as though we feel that we need certainty, for some kind of reassurance, and so we project that need onto the universe. Why should it care if the future is certain, in the sense of being predictable from a present set of information? What if the future has in some sense already happened, yet there is never enough information in any present to determine it? Maybe the future just is. It could be just like the past-- many things have happened that have left no discernible trace, the events have been simply erased from the record by eons of deterioration. So if there is not enough information in the present to completely reconstruct the past, yet the past existed anyway, why can't the future be like that too?

There's no evidence that we could. At present, QM appears to do everything that can be done, except when that involves unification with general relativity-- and there's no immediate reason to think that making QM deterministic will allow that unification. Most experts seem to think it will require removing the determinism from general relativity. I cannot say why!
And how do we go about deciding what is the true nature of the universe if it is unimportant? Isn't the whole purpose of science to discern, out of the multitudinous complexity of all creation, what actually is important?

You might enjoy reading The Road to Reality, A Complete Guide to the Laws of the Universe by Roger Penrose. He is in the camp of the few who think that relativity will stand and quantum theory will have to be modified. I cannot explain why either, but I am not sure that I would want to bet against the intuition of a Penrose.

It doesn't, it only knows it's current conditions.

It's current state, precisely.

It shouldn't, it only needs to know its current state, which it knows by being in it.

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.

Ken,

"Just how much information can fit in one universe anyway? Why should it need an infinity of information just to function? Nothing else seems to."

I dont know, but I'll take a stab at it: What if infinties are compulsory for a universe to be truly open-ended and non-deterministic? It just seems that maybe the universe would not be as complex, dynamic and creative without infinite values. In a weird way infinity is like an automatic driver of creativity because nothing repeats exactly ever and ever.

"There's no evidence that we could. At present, QM appears to do everything that can be done, except when that involves unification with general relativity-- and there's no immediate reason to think that making QM deterministic will allow that unification. Most experts seem to think it will require removing the determinism from general relativity. I cannot say why!"

That interesting because as far as Im aware the classical macroscopic world is as non-determinstic as is the quantum. I dont understand the need to make GR non-determinstic when we can already observe non-deterministic behaviour in nonlinear (non-idealised) open ended systems. I know many dont agree but i think there is a correlation between the HUP at the quantum level, and unpredictability on the macroscopic scale due to unknowable initial conditions. The key factor in both physical laws or principles is exactly the same; it being that total certainty is not possible.

To me GR is covering completely different part of nature's behaviour. I see qm as way more fundamental on the question of determinism/non-determinism than GR but that is just my personal speculation.

Yes, that would likely be a fascinating book. Most physicists think Penrose is barking up the wrong tree there, but most "experts" thought the Greek Aristarchus was wrong about the Earth being in motion about the Sun.

But why must it know even that? If a question goes unasked, why should we ever imagine that it has an answer?

But we have no understanding of how to specify "precise" information. The concept of a number is an example of precise information, but in all physical contexts, numbers represent approximations. It was always purely a guess that precise numbers have anything to do with reality, and there is no observational evidence that this is the case. Indeed, the observational evidence is quite to the contrary, which is what Jetlack is pointing to.

We can agree that the current state is what the universe is in, and in that sense must "know" it, but at issue is how much information is actually encompassed in that current state. There is no good reason to think the information is precise.

That's an interesting conundrum. Normally, the concept of determinism is associated with infinitely precise information-- say, a location known to an infinite number of decimal places (otherwise, indeterminacy creeps in exponentially over time). But perhaps an infinite amount of information would also lead to indeterminacy, because it would require a higher order of infinity to process that information in an exact way so as to propagate all the interactions forward in time. Either way, it would seem that perfect determinacy is a physical impossibility, which frankly doesn't surprise me in the least-- it was always just in our minds.

That was probably more of an issue in a steady-state universe. But in our dynamical universe, there is really no way to get repetition anyway, at least not in any finite volume, because the global conditions are changing.
Yes, I would agree with that. Many would say that the macro world is ruled by classical physics, which is a deterministic theory, but it is still just a theory-- which means it is designed for a purpose. That the classical world is ruled by a deterministic theory does not mean it "really is" deterministic, that's the common mistake made in science that I see quite often (and many may tire of seeing me point out on this forum!).

I think the difference that people point to is that the HUP encodes an uncertainty that is inherent, built right into the laws, whereas classical uncertainties (like sensitivity to initial conditions) are not independent of the precision of the information you are working with. In principle, you can imagine that classical information asymptotically approaches information that is perfectly precise, whereas you can't even imagine it with the HUP. But the key word there is "imagine"-- what we can imagine, and what we can actually test with experiment, are two very different things. The fact that classical thinking ran into a stumbling block, the HUP, is perfectly natural-- if it hadn't been the HUP, it might well have been something else. So it goes with imagination.

Yes, that is definitely the prevailing view, though DrRocket pointed out the dissenting view of Penrose.

Ken,

"That the classical world is ruled by a deterministic theory does not mean it "really is" deterministic, that's the common mistake made in science that I see quite often (and many may tire of seeing me point out on this forum!)."

Yes this is something that also confuses me. For instance why is it called "deterministic chaos"? I've debated this point with people on the BAUT forums; that while the individual systems in an "idealised" environment could be coined as determinstic; the real world with an open ended dymanic consisting of unknowable conditions, influences or factors should not be called Determinstic. If the system as a whole is inherently unpredictable then calling it Determinstic just seems ..well fraudulent actually.

Going out on a limb here; this charade over so-called Determinsim has seriously dented my belief in the purity of scientific endeavour. That may sound lame but i was genuinely shocked that some scientists still cling to this mantra when all the obervationsal evidence points to the opposite conclusion, at least in practice.

The part that really gets me is that unless a non-science type person does a lot of digging, a lot of questioning, and a lot of logical thinking on their own, they would be left in their state of ignorance and would take for granted that often repeated lie about the universe being Determinstic.

Maybe im too senstive to initial conditions :-)

"In principle, you can imagine that classical information asymptotically approaches information that is perfectly precise, whereas you can't even imagine it with the HUP. But the key word there is "imagine"-- what we can imagine, and what we can actually test with experiment, are two very different things. The fact that classical thinking ran into a stumbling block, the HUP, is perfectly natural-- if it hadn't been the HUP, it might well have been something else. So it goes with imagination."

I think the classical world ran into the non-determinstic signals from nature long before qm was developed. From what Ive read about non-linear equations is that they are simply better and better approximations but there is never an absolutely precise solution or answer.

Or for instance the N body problem which i believe was known ever since some time after Newton. Why is it that we still cant solve the N body problem precisely? Its dealing with a relatiuvely simple problem of 3 or more objects influencing eachothers motion. If we can't solve that to a precise exact determination then its rather dubious and hubristic - might i add - to claim the whole universe is Determinstic. Talk about trying to run before one can even crawl :-)

Yes, "deterministic chaos" is really an oxymoron, though what it labels does have a precise definition (which I believe is essentially exponential growth of uncertainties, such that even though there is no limit on how certain the data could get, even the slightest perturbation will grow relatively rapidly until predictability is lost). So a given path as a mathematical entity is predictable (the "deterministic" part), but in practice we don't have paths, we have neighborhoods of uncertainty that grow with time such that it is impossible in practice to "stay on" a given solution (the "chaos" part). I think the idea that there is an underlying determinism behind the chaos comes from the idea that the position "really is" a mathematically precise entity and we just can't specify it, but of course this reverses the proper role of mathematics in physics, leaving us with just the oxymoron.

Perhaps the error was in originally expecting science to be a "pure" endeavor. It is a human endeavor, no doubt, and is subject to human foibles. It tries to reign in those foibles, moreso than to eliminate them, so the key is for us to actually follow the principles of science and not fall into human nature. Feynman defined science along the lines of instructions for not fooling ourselves, given that we are each the easiest person for us to fool. As always, he was right on the money, it's just especially poignant when we fool ourselves with science, or with an inaccurate application of those careful instructions.
I'm not sure where the sources are that are telling you the universe is deterministic. I do see scientists falling into various determinism traps, but I'm not sure I've seen any come right out and claim that we know the universe is deterministic. Most would classify that as an "interpretation" of quantum mechanics, where "interpretation" basically means that it is not constrained by experiment but is a way that seems reasonable to them to imagine. Some get less careful than that. Quantum mechanics makes this whole issue very subtle indeed, because the core equation of quantum mechanics, the Schroedinger equation, is a deterministic equation that acts on a statistical entity, the wave function. So built right into quantum mechanics is a curious "shotgun marriage" of determinism and stochasticity, reminiscent in some ways (but different in others) of "deterministic chaos", and we've been scrambling to properly interpret that ever since. It quickly falls into what most would have to agree is very much a matter of opinion, and matters of opinion are normally classified as being outside of science proper.
There is a precise solution mathematically, but only to the extent that it is possible to specify a number "perfectly". It is a little like the philosophical question, is there really such a number as pi? We define pi in various ways, using mathematically precise functions or operations (like the ratio of the circumference of a circle to its diameter, or the first zero in the cosine(theta/2) function), but we have no way of knowing if this number "really exists" in practice because our algorithms cannot run for infinite time so cannot generate a number to infinite precision, nor can any measurement. So without getting into how many angels can dance on a pin, I agree with you, we never had any good reason to think that pure numbers could participate in the algebra we need to do physics, we simply pretended they could because it is a pleasing idealization. In terms of anything practical that can actually be done, you are right-- there are only better and better approximations. Science is very much the art of approximation, yet people are always confusing it with a purer form of mathematics, simply because one can usually get away with that confusion-- until one encounters a questioning skeptic like yourself.

Yes, the claims of determinism were always based on a kind of religious idea that the universe could do things that we could not. It was as though the universe had access to a "perfect" computer to solve its equations, whereas we have only better and better computers. Of course there's nothing scientific behind that perspective, it was always just a form of lazy thinking that we could usually get away with. And at some level there's nothing wrong with getting away with things-- that's basically the goal of science, to bring reality into a realm of understanding that clever apes could get away with. The error is when we forget that this is what it is, and we, like Icarus, get too amazed by our own achievements, astounding though they may be.

__________________
Logic is the grammar of truth.

Meaning and absolute certainty are incompatible, and profound meaning and absolute certainty are profoundly incompatible.

The only thing intelligence is capable of is recognizing itself.

Ken,

"Perhaps the error was in originally expecting science to be a "pure" endeavor. It is a human endeavor, no doubt, and is subject to human foibles. It tries to reign in those foibles, moreso than to eliminate them, so the key is for us to actually follow the principles of science and not fall into human nature. Feynman defined science along the lines of instructions for not fooling ourselves, given that we are each the easiest person for us to fool. As always, he was right on the money, it's just especially poignant when we fool ourselves with science, or with an inaccurate application of those careful instructions."

We all have these human biases and thats why we need to constantly ask ourselves if we are being objective. I know I'm always checking myself for bias and very often find it :-) I'm clearly biased towards a non-determinstic universe and I'm sure much of that is an emotional need. However I think I've also thought it all through, and even regardless of my own bias i dont think i am kidding myself. However we all live in our own reality to some extent so i could be a complete self-delusional loonie :-)

"Yes, the claims of determinism were always based on a kind of religious idea that the universe could do things that we could not. It was as though the universe had access to a "perfect" computer to solve its equations, whereas we have only better and better computers. Of course there's nothing scientific behind that perspective, it was always just a form of lazy thinking that we could usually get away with. And at some level there's nothing wrong with getting away with things-- that's basically the goal of science, to bring reality into a realm of understanding that clever apes could get away with. The error is when we forget that this is what it is, and we, like Icarus, get too amazed by our own achievements, astounding though they may be."

Perhaps this is a human malaise which comes from being the most advanced biology on the planet, by what appears to be quite some margin.

I've always thought the Determinist piliosophy of science was more like a self-imposed raison d'etre for scientists. In a way they and the scientific profession remain more valuable to society the more precise their predictions. Its a bit like an alchemist exaggerating to the king in order to get more funding for his experiments.

As you said, our science is fundamentally human-centric.

Wow Ken! I think you might have just changed my mind. If determinism were true, the universe would have to "know" not only its initial conditions absolutely perfectly, but also every other condition in between. And where is this information going to get stored? It can't be in the internal states of particles themselves--there's just not enough of either. So it would have to be in the relations of the particles.

In other words, the "knowledge" of previous states of the universe would be stored in the position and momentum of particles relative to each other.

And here is where the Heisenberg Uncertainty Principle comes in. The HUP is not a property or result peculiar to human consciousness. No, it arises because the instruments we use to measure particles are made out of the same sorts of particles that we are trying to measure. Therefore, particles that interact with each other are subject to the same limitation that we are: they cannot "know" the exact position and momentum of their immediate neighbors. Therefore, it is impossible to store perfect "knowledge" of past states within present states. And since nothing can know the past perfectly, nothing can no the future--even in principle. Therefore, determinism is false.

So, you have changed my mind. I now agree that the Bohmian program is forlorn. If it is to have a future in addition to its history, it will have to be reformed somehow to include indeterminacy. It's main saving grace is that it is not content with mere surface, behavioristic, black-box empiricism, and want's to probe deeper. But it will still find uncertainty and indeterminism. The difference between the Bohmians and the Copenhagenists is that they will take indeterminism to not be an inherent, simple property of the universe. Rather, indeterminism is an emergent property of wholes that emerges mechanically from the interactions of parts. But there is a looseness in the parts, and it is this looseness from which indeterminism arises.

Einstein's famous quip was only partially correct: God doesn't play dice, but everything else does.

Ehrm, no.
At any time it only needs to "know" it's current state, which it does by being in it.
Why would it need to know anything about any other time than now?

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.

I think Ken G's point is that its present state is the only thing a thing can know. Wasn't it LaPlace or someone who said that if you knew everything about the present state, you would know everything about the past or future. God was supposed to be able to do that. The universe was like a big pinball machine. If you knew the position and momentum of the ball perfectly, as well as all of the properties of the bumpers, you would be able to project the trajectory of the ball forward or backward perfectly as if it were like a computer program that has only one choice about what to do based on any given set of initial parameters.

and then comes along deterministic chaos which shows that even for completely deterministic systems you need knowledge of the complete state to predict, which means you can't predict reliably with anything simpler that the system being predicted.

And as HUP limits how much we can measure, in a way it means that whether the universe is deterministic or not can't be determined as we can never know enough to know if any discrepancy between prediction and actual outcome is caused by indeterminism or just insufficient knowledge.

In a way science then becomes the art of identifying those subsets of (possibly syntesized) state variables where useful predictability is achievable and determine the limits of the subsystems, the rules that predict and the limits of the predictability.

An example of what I think of when I say a system of synthesized state variables is the masses of the planets and sun as well as the position and velocity of their centers of gravity.
That makes for a system that has quite high predictability while still ignoring almost all the information in the system, but as the prediction range extends it becomes insufficient because factors that have been left out start to have measurable influence.

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.

Actually what it says is that you need PERFECT knowledge of the state to predict very far into the future with any sort of acceptable accuracy. You need complete knowledge of the state to predict the behavior of a dynamical system even without any notion of chaos. Basically chaotic systems are those for which the trajectory in state space is not a continuous function of the initial data -- this is a bit oversimplified and imprecise but it gets the idea across.

Yes, that's what I tried to say.

__________________
‘To those who regard “crime fiction” as some sacred icon which must follow a rigid formula, I will always be the man who writes 18-syllable haiku.’Trying to make sense of computers, The Error Log.

Yes, I would say that chaos and quantum uncertainty are just detailed ways that we have found our concept of determinacy breaks down. The breakdown could have happened some other way, and might yet. Perhaps it is hindsight, but I would tend to think we should have expected this-- determinacy seems impossible, for all the reasons we've been talking about. But even for those who want to believe it is possible, one has to ask if science is about what is possible, or about what is demonstrable. We can certainly demonstrate that determinism is a useful concept, when it is useful. At what point do we turn around and take our useful constructs and use them to tell the universe how to be? It seems like that is rather reversing the proper direction of the flow of knowledge.

I would also add that determinism breaks down when it comes to free will and moral responsibility.

It seems a rather simple piece of logic to say that if a particle is real then it is in a location and is moving in a direction at a speed. Heisenberg’s discovery that we cannot have access to this information is irrelevant to whether it is true or not. Your description of position as “a certain notion” seems absurdly idealist – as though the location of the quarks in an object is an abstract concept rather than a property of the thing itself. The particles that make up an object are in the object, not somewhere else. By looking at smaller and smaller objects we can, logically if not empirically, narrow down the position of any one particle precisely. Your statement that the purpose of the idea is its usefulness seems equally suspect. After all, we study astronomy to find out the nature of the universe, not primarily for utility. Quantum mechanics is the same, we primarily want to find out the nature of reality, and any use the knowledge may have is secondary.Determinism is more a logical concept than a scientific one. Heisenberg proved that science cannot be deterministic because some information is beyond our perception. However, if we say that a particle is a thing that obeys the laws of physics, determinism seems to flow as a necessary consequence. In the mechanistic Newtonian sense postulated by Laplace, at any given instant all particles have position, direction and momentum, determining their position, direction and momentum at the next instant, and logically implying similar causality for each successive instant, and so that all future events in the universe are ultimately determined by cause and effect. This logical argument does not imply any diminution of human freedom, because a person who behaves as if their behaviour is fated will make different decisions from a person who believes they are free. Nor does it imply the existence of an entity which somehow knows the future fate of the world.

Are you espousing Bohm's Hidden Variables theory here?

Yes, that's an important direction in which the concepts of determinism have been over-applied. I don't know if we really know anything about what physics has to say about those things, but determinism ain't it.

Not necessarily, I'm just trying to apply a common sense logic, going back to Aristotle's principle of non-contradiction, which from my meagre understanding seems at the base of Einstein's objections to the improbable speculations of quantum mechanics as shown by the Schrödinger Cat Paradox. My impression is that the HUP is an example of the observer problem that has been magnified into a claim that just because we can't see causality at quantum scale it does not operate. I agree with Bohm that the problem should be approached from the perspective of ontology rather than the usual scientific emphasis on epistemology, but don't understand why a hidden variable needs to be postulated to save causality.

ETA: Albert Einstein, in a letter to Schrödinger dated 1950:

Robert,
Correct me if I have misunderstood you.

I have the impression that you are taking Einstein's position that QM is an incomplete theory, and he said "I am convinced God does not play dice" — meaning that he believed that physical theories must be deterministic to be complete.

Bohm's hidden variable theory, as I understand it, postulates that QM is incomnplete and a deeper reality is hidden below QM.

Why then do you feel we don't need hidden variables'