Re:Change = Calculation? (Score:5, Interesting) by 2nd Post! (louis_wang@h p . com) on Monday June 03, @02:05PM (#3632474) (User #213333 Info | http://nekobox.org/~sillyoldbear) As far as I can recall, one of the basic premises of entropy and information theory is that *everything* can be expressed in bits. If everything can be expressed in bits, then everything is computable. A stupid question is whether the universe is a determinstic Turing machine or not, or whether it is by very nature indeterministic :P It's not that something has to be made into a computer so much as redefining one's perspective of what a computer is to accomodate the realities of the universe; that DNA is a storage mechanism, with RNA and DNA replication and protein synthesis being complex computation processes. Or that the universe is really expressible as a bunch of states (read his article, and you'll see that), and as such the traversal from state to state is no more complex than following a state diagram in a really big state machine... Which is just a computer, doncha know? [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by gibi on Monday June 03, @02:53PM (#3632911) (User #581962 Info) "A stupid question is whether the universe is a determinstic Turing machine or not, or whether it is by very nature indeterministic :P" I'm not that experienced in physics but I would say that the existence of quantum effects indicates to a indeterministic nature. That would also explain how the universe can cope with the large amount of computation. [ Reply to This | Parent ] Re:Change = Calculation? (Score:2) by 2nd Post! (louis_wang@h p . com) on Monday June 03, @03:17PM (#3633090) (User #213333 Info | http://nekobox.org/~sillyoldbear) Unless I misunderstand quantum, there's no conflict between determinism and quantum mechanics. I think the point being that if something is unobserved, an object is the sum of all it's possible states until it is observed. Technically the wavefunction collapses. Quantum mechanics doesn't tell us about determinism or nondeterminism except that the act of observing a state will change the state, meaning the universe is technically deterministic (perhaps) while being practically nondeterministic. [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by mschachter on Monday June 03, @04:19PM (#3633588) (User #539568 Info) I think the point being that if something is unobserved, an object is the sum of all it's possible states until it is observed. I think it's more along the lines of the fact that you're observing something means that there's an uncertainty either in it's momentum or position; wheter it be an electron, proton, atom or photon. The fact that there's built-in uncertainty allows for that aforementioned particle to have either an unpredictable momentum, or an unpredictable position, thereby making it unpredictable and indeterministic. Now, if the fundamental particles of the universe are all indeterministic, the universe itself therefore becomes indeterministic. I think thats how it goes. [ Reply to This | Parent ] Re:Change = Calculation? (Score:2) by 2nd Post! (louis_wang@h p . com) on Monday June 03, @05:01PM (#3633943) (User #213333 Info | http://nekobox.org/~sillyoldbear) This is where it gets philosophical. Does the uncertainty exist in the particle or in the observer? Just because *we* don't know the characteristics of an electron, does that mean the electron doesn't know it's own mass, momentum, velocity, spin, etc? [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by gibi on Monday June 03, @05:22PM (#3634190) (User #581962 Info) Good question. So is schroedinger not quite right and his cat determines her own state? In school I always wondered why the cat does not count as observer. If she counts, we know that the uncertainty lays in the observer, don't we? Well, I drift away a little and nobody knows THE answer, so... [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by mschachter on Monday June 03, @05:25PM (#3634209) (User #539568 Info) Well, an unobserved electron would theoretically have no real mass, momentum, velocity, spin, etc. It would exist in a superposition of all it's possible states, I think. I guess the question is what is an observer? I think the "observer" in this case would be the apparatus used to measure the state of the electron. If you could use a photon to measure the state of the electron, then the photon would be the observer... (again, I think, i'd hope if i'm wrong somebody jumps in and says so). Then the interaction between the photon and the electron is what causes the collapse of the superposition. But the act of observation makes something uncertain, and therefore indeterministic. But if nothing's being observed, then would everything exists in a state of superposition, making determinism meaningless, because everything exists everywhere? [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by statusbar (jeff at statusbar dot com) on Monday June 03, @07:22PM (#3635002) (User #314703 Info | http://www.jdkoftinoff.com/) It is not just the 'act of observation making something uncertain'. Energy is proportional to planck's constant times frequency. Since frequency is 1/time, this means that energy depends on time. The point is that the unobserved electron frozen in a 'snapshot' in time has no energy. --jeff++ [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by Idylwyld on Monday June 03, @05:25PM (#3634212) (User #324288 Info) Quantum mechanics does not rule out determinism. In fact, due to the exist of a finite set of constants and physical laws it is obvious that the universe is, at base deterministic. Quantum uncertainty only makes it harder for us to determine the base state of the universe. Obviously we are playing a game without having been told the rules. Not only that but the umpires won't let us watch the whole game so we can't even make a good guess at the rules. Whoever started this whole thing up really didn't want us to be able to see how it's going to turn out... [ Reply to This | Parent ] Re:Change = Calculation? (Score:2) by martyn s on Monday June 03, @02:42PM (#3632825) (User #444964 Info | http://slashdot.org/) The thing is, mathematically you can solve a halting problem. In other words, you can prove mathematically whether any specific program will end or not. If a person (a brain) can solve this, why can't any sufficiently advanced computer do the same? [ Reply to This | Parent ] Re:Change = Calculation? (Score:1) by protonman on Monday June 03, @02:50PM (#3632897) (User #411526 Info | http://slashdot.org/) Sure they can, they just can't do it for *EVERY* given problem, just like you (probably) ;-) [ Reply to This | Parent ] Re:Change = Calculation? (Score:4, Insightful) by Mr. Slippery (tms@infamous.nCHEETAHet minus cat) on Monday June 03, @03:16PM (#3633082) (User #47854 Info | http://www.infamous.net/) In other words, you can prove mathematically whether any specific program will end or not. Uh, no. You can't. There are individual cases for which you can make an ad-hoc proof, yes, but there is no general algorithm that, given a computer program (more properly, a Turing machine), tells you if it halts. I'll leave the gory details to Wikipedia [wikipedia.com]. [ Reply to This | Parent ] The Halting Problem? (Score:1) by einer on Monday June 03, @04:56PM (#3633900) (User #459199 Info) The details aren't that gory. Say for instance you have a program that's running. Will it halt? The answer is unkown until it halts. If it doesn't halt, that doesn't mean that it will run to completion, it just means that it may not have halted... yet... [ Reply to This | Parent ] Re:The Halting Problem? (Score:1) by Mr. Slippery (tms@infamous.nCHEETAHet minus cat) on Monday June 03, @05:26PM (#3634221) (User #47854 Info | http://www.infamous.net/) But it is gorier than that. Sometimes you can prove halting - that's what formal correctness proofs are all about. But if you've ever done them, you may recall that there's a "creative" aspect involved in picking loop invarients; it's not a paint-by-numbers sort of thing.