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Originally Posted by Jetlack
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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.
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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.