Predicting the Future

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Predicting the Future

Postby quintopia » Tue Dec 04, 2007 5:13 pm UTC

Is the universe deterministic?
That is, given a magical oracle that can give a complete description of the universe at a certain moment in time, and a uber-powerful universe simulator that can calculate the interactions of particles and forces so small no one yet understands them, could we accurately and completely predict the future?
Is the universe reversible?
That is, does it never reach ambiguous states? Could the above oracle and simulator use a current state of the universe to completely describe the past?

Yes, I know the question is, scientifically speaking, irrelevant, since such an oracle could never exist and since such a simulator would need to contain and operate on as much information as the universe contains (which means a duplicate but faster running universe would probably be the optimal solution).

However, such questions are theologically interesting, so I thought a survey would be in order.

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Re: Predicting the Future

Postby Indon » Tue Dec 04, 2007 7:00 pm UTC

While I personally am a determinist, physics as we know it do not appear to be deterministic in nature; with what we know, such an oracle would merely be probabilistic; it could tell you the chances for any given future event.
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Re: Predicting the Future

Postby Rook » Tue Dec 04, 2007 7:16 pm UTC

quintopia wrote:Is the universe deterministic?
That is, given a magical oracle that can give a complete description of the universe at a certain moment in time, and a uber-powerful universe simulator that can calculate the interactions of particles and forces so small no one yet understands them, could we accurately and completely predict the future?

Yes and no. If you asked for a prediction of what a person or persons were going to do at some future date, simply receiving the answer could change events. For example, if you asked 'will I buy item-x' tomorrow, regardless of the answer you would buy item-D (which is any item not mentioned), just to be a bitch.

You can't account for this either, because in changing the answer to account for bitchiness, you would change your action just to prove it wrong. There is also the possibility that receiving a prediction of some set of events could change those events in some way, even if you did nothing and the events happened nowhere near you (think quantum butterfly, but replace butterfly with oracle). In such a situation, the oracle is useless, because every time she makes a prediction, she changes the event in some way.

Note, it might be so small an effect as to be negligible, but the point is that it might not.
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Re: Predicting the Future

Postby quintopia » Tue Dec 04, 2007 9:16 pm UTC

Let's assume that the simulator files the information away so it is never seen or heard by anyone or anything until after the time period in question has passed. The point. . .could it be that in retrospect the machine was always correct?

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Re: Predicting the Future

Postby Indon » Tue Dec 04, 2007 9:19 pm UTC

Even if the oracle tells you what's going to happen, such a hypothetical oracle capable of perfectly predicting events could be correct; it would simply do so by preemptively taking your reaction to its' statement into account.
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Re: Predicting the Future

Postby VannA » Tue Dec 04, 2007 9:41 pm UTC

In such a situation, the oracle is useless, because every time she makes a prediction, she changes the event in some way.


This summation of the issues surrounding interaction/prediction/observational change regarding quantum-level physics made me giggle.

This thread has been discussed quite a lot elsewhere, but buggered if I can remember what it was in.

Where you outside the system, then perhaps you could make a predictive model of the universe.. whether or not it is feasible to be able to observe a system without interaction is a very serious question, however.
Once you interact with a system, you then become part of it.. which means you are no longer capable of accurate predictions, merely, as indon said, capable of determining probabilities.
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Re: Predicting the Future

Postby 22/7 » Tue Dec 04, 2007 10:01 pm UTC

Is this not the same thing as the threads that have discussed predestination?
Totally not a hypothetical...

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Re: Predicting the Future

Postby quintopia » Tue Dec 04, 2007 10:06 pm UTC

I wouldn't know. . .I was just wondering how many people thought everything behaved deterministically. Right now, people seem focused more on Gödelian and Heisenbergian paradoxes, rather than the questions posed.

There are many ways to construct the situation so it gets at the question while avoiding the paradoxes. However, the second question (about reconstucting the past) is not subject to them.

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Re: Predicting the Future

Postby Nath » Tue Dec 04, 2007 10:16 pm UTC

quintopia wrote:Is the universe deterministic?
That is, given a magical oracle that can give a complete description of the universe at a certain moment in time, and a uber-powerful universe simulator that can calculate the interactions of particles and forces so small no one yet understands them, could we accurately and completely predict the future?
Is the universe reversible?
That is, does it never reach ambiguous states? Could the above oracle and simulator use a current state of the universe to completely describe the past?

I am not a physicist, but my impression is that the answer to both questions is 'no'.

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Re: Predicting the Future

Postby Rook » Tue Dec 04, 2007 10:32 pm UTC

quintopia wrote:I wouldn't know. . .I was just wondering how many people thought everything behaved deterministically. Right now, people seem focused more on Gödelian and Heisenbergian paradoxes, rather than the questions posed.

There are many ways to construct the situation so it gets at the question while avoiding the paradoxes. However, the second question (about reconstucting the past) is not subject to them.

If you really couldn't tell, I'm a 'no'.

The only thing that stops me from proving my standpoint is that I care about the consequences of doing something completely random. I mean, doing something on the order of XKCD randomness could be justified as having been influenced by the comics and my own temperament. The only way I have ever been able to think of that would prove the non-deterministic nature of the universe would be by killing someone I was sitting next to, for absolutely no reason.

Unfortunately, doing so in an effort to disprove determinism could mean I had been influenced to do it, because the argument got to me so much, making it a wasted effort.


This is why I hate determinism; it's a slippery bugger when you try to disprove it, and it makes no real odds anyway; just because I have no 'real' choice in what I do, doesn't mean I can't enjoy myself.
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Re: Predicting the Future

Postby mister k » Tue Dec 04, 2007 11:07 pm UTC

Of course you could have random determinism, which would sort of allow for free will within the frame work of determinism. That is, at the start of the universe there are various factors that are randomly chosen which then determine the universe for the rest of time. Although actually I would take issue with that. Actually I don't think free will as we understand it is infringed unless the deterministic nature of the universe has been decided by something at a concious level.

I lean towards determinism in the universe, simply because I don't really get randomness. Actually thinking to hard about things makes my head hurt, simply because humans aren't wired to understand how the alpha and omega of the universe could work. If rules are set up a certain way, why are they- if something is random, why is it random? Why does blue look blue? Ultimately pointless questions. I rather like the idea of the clockwork universe because it's neat, but certainly as I understand it quantum physics declares the universe to be random. Certainly nuclear decay appears to be random but there could be hidden determinism which is either completely undetectable or undetectable to current methods.
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Re: Predicting the Future

Postby Hexadecimator » Wed Dec 05, 2007 6:27 am UTC

I would agree that the univers is mostly deterministic to people within it and might be entirely deterministic to a hypothetical observer outside of it who could determine both an object's position and velocity with no uncertainty.

Reversible? I suppose so, but only to the extent that the above is true. As far as I can tell, all the equations work just as well in the reverse. I played around with a universe consisting only of floating rocks and gravity. It works for 2 rocks, but I couldn't / was too lazy prove anything beyond that.
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Re: Predicting the Future

Postby blob » Wed Dec 05, 2007 10:55 am UTC

Is the question one of determinism vs randomness or determinism vs free will? I don't think those are the same.
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Re: Predicting the Future

Postby photosinensis » Wed Dec 05, 2007 2:55 pm UTC

Personally, I believe in a deterministic universe, so yes, it's possible, if you know all the variables. However, knowing all the variables is generally impossible, and thus charting the function is also impossible. Thus, we're stuck with probability.

That said, all of my divination attempts have a little disclaimer that says "for entertainment purposes only". Of course, I don't say whose entertainment they're for (usually mine).
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Re: Predicting the Future

Postby 22/7 » Wed Dec 05, 2007 5:12 pm UTC

When you say reversible... are you speaking in the thermodynamic sense?
Totally not a hypothetical...

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Re: Predicting the Future

Postby Maurog » Wed Dec 05, 2007 6:13 pm UTC

Pah, floating rocks. If you enter a room filled with air that was sealed for a hundred years, and you see two balls lying still in there, do you really think that even with the complete information about the position of each particle in the room, you can tell exactly how someone threw them in, some hundred years ago?

I find it highly unlikely.
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Re: Predicting the Future

Postby 22/7 » Wed Dec 05, 2007 6:45 pm UTC

Maurog wrote:Pah, floating rocks. If you enter a room filled with air that was sealed for a hundred years, and you see two balls lying still in there, do you really think that even with the complete information about the position of each particle in the room, you can tell exactly how someone threw them in, some hundred years ago?

I find it highly unlikely.


You're making a lot of assumptions that are (I assume) based on the present state of knowledge of things like entropy and our current inability to make such calculations as to the interactions between atoms that actually happen all the time. However, if we set as a given that we are both able to predict the amount of entropy formed in each interaction and that we are able to quickly and accurately model such a room (i.e. our formulas get much better/more complex than they are now), then it would theoretically be possible to model that. Right now, no, we most certainly cannot.
Totally not a hypothetical...

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Re: Predicting the Future

Postby Vaniver » Wed Dec 05, 2007 10:10 pm UTC

Determinism is, at some level, wrong. Hidden variables appear to not exist (look up Bell's theorem, but getting a physics degree first will help).
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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 1:45 am UTC

photosinensis wrote:Personally, I believe in a deterministic universe, so yes, it's possible, if you know all the variables.

Do you believe this based on some evidence, or just because?

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Re: Predicting the Future

Postby Hexadecimator » Thu Dec 06, 2007 2:29 am UTC

Maurog wrote:Pah, floating rocks. If you enter a room filled with air that was sealed for a hundred years, and you see two balls lying still in there, do you really think that even with the complete information about the position of each particle in the room, you can tell exactly how someone threw them in, some hundred years ago?

I find it highly unlikely.
I actually thought about that one for awhile before posting my previous claim (my example was, pick a crater on the moon, and tell me when the meteor hit). However, if you knew the state of every atom in the room, you could continue tracing each collision backwards until you had waves consistent with a moving rock or a closing door. Also, the rocks themselves are dampened springs, and the effects of a collision can be measured indefinitely. A wave will continually reverbebrate through the rock, dampening over time at a known rate, but never going away. Given perfect knowledge with infinite precision, you could determine when the rock hit the ground.
Even given an ideal gas, this would take thousands of years with current technology, but this is a hypothetical, so we don't care.

Yes, it goes against common sense, but it makes sense that you can calculate 1 particle interation into the past and 2 particle interactions into the past, and 3, and 4, etc. Work your way back to n and n+1 interactions, and you can calculate anything, assuming infinite precision in your measurements.
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Re: Predicting the Future

Postby 22/7 » Thu Dec 06, 2007 2:31 am UTC

Nath wrote:
photosinensis wrote:Personally, I believe in a deterministic universe, so yes, it's possible, if you know all the variables.

Do you believe this based on some evidence, or just because?

Are you saying that with knowledge of all the variables and a perfect set of equations one would not be able to make an accurate prediction as to the outcome of the system?
Totally not a hypothetical...

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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 3:12 am UTC

22/7 wrote:
Nath wrote:
photosinensis wrote:Personally, I believe in a deterministic universe, so yes, it's possible, if you know all the variables.

Do you believe this based on some evidence, or just because?

Are you saying that with knowledge of all the variables and a perfect set of equations one would not be able to make an accurate prediction as to the outcome of the system?

I am not a physicist, but my understanding is that this is true according to the predominant interpretations of quantum mechanics.

My objection wasn't so much to the claim that the universe was deterministic: I don't know enough physics to dismiss that out of hand. I just don't see how someone can simply believe a scientific claim; I wanted to know if that was just photosinensis' gut feeling, or the result of some evidence he or she didn't mention.

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Re: Predicting the Future

Postby 22/7 » Thu Dec 06, 2007 7:03 am UTC

Nath wrote:I am not a physicist, but my understanding is that this is true according to the predominant interpretations of quantum mechanics.

My objection wasn't so much to the claim that the universe was deterministic: I don't know enough physics to dismiss that out of hand. I just don't see how someone can simply believe a scientific claim; I wanted to know if that was just photosinensis' gut feeling, or the result of some evidence he or she didn't mention.

The question I would posit is simply, 'is our understanding (as a species) of quantum mechanics an accurate description of how things actually work, or is it simply our best guess, educated as it may be, and if we had a perfect description of the world around us, could we accurately predict what would happen?'
Totally not a hypothetical...

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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 7:32 am UTC

22/7 wrote:
Nath wrote:I am not a physicist, but my understanding is that this is true according to the predominant interpretations of quantum mechanics.

My objection wasn't so much to the claim that the universe was deterministic: I don't know enough physics to dismiss that out of hand. I just don't see how someone can simply believe a scientific claim; I wanted to know if that was just photosinensis' gut feeling, or the result of some evidence he or she didn't mention.

The question I would posit is simply, 'is our understanding (as a species) of quantum mechanics an accurate description of how things actually work, or is it simply our best guess, educated as it may be, and if we had a perfect description of the world around us, could we accurately predict what would happen?'

That's really two separate questions:
1. Is our understanding (as a species) of quantum mechanics an accurate description of how things actually work, or is it simply our best guess?
2. If we had a perfect description of the world around us, could we accurately predict what would happen?

The answer to the first question is that quantum mechanics is simply our best guess. The answer to the second question is unknown. However, according to our best guess (as I understand it), the answer is no. In other words, as far as we can tell, even a complete description of the present, including perfectly accurate equations, will not tell us for sure what the future will be.

It is possible that our best guess is wrong, but that does not necessarily mean that the world is deterministic.

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Re: Predicting the Future

Postby Sarcio » Thu Dec 06, 2007 8:01 am UTC

personally...
yes, the universe is deterministic.

deterministic being a fancy term for 'only one thing can happen at a time.'

which is true. I can't roll a single die and get both a two and a six.

so if i knew every vector, every constant, every degree, every minute force, and every position/velocity of every subatomic particle, i could conclude the results of everything, and predict the future.

practically...no. no you can't.
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Re: Predicting the Future

Postby 22/7 » Thu Dec 06, 2007 8:11 am UTC

Sarcio wrote:personally...
yes, the universe is deterministic.

deterministic being a fancy term for 'only one thing can happen at a time.'

which is true. I can't roll a single die and get both a two and a six.

so if i knew every vector, every constant, every degree, every minute force, and every position/velocity of every subatomic particle, i could conclude the results of everything, and predict the future.

practically...no. no you can't.

This is what I'm getting at, Nath.
Totally not a hypothetical...

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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 11:50 am UTC

22/7 wrote:
Sarcio wrote:so if i knew every vector, every constant, every degree, every minute force, and every position/velocity of every subatomic particle, i could conclude the results of everything, and predict the future.

practically...no. no you can't.

This is what I'm getting at, Nath.

I see what you're saying, and I see why it's intuitively a nice idea. Einstein liked it, too. I just don't see any evidence that it's true.

Perhaps even if we knew every vector, every constant, every degree, every minute force, and every position/velocity of every subatomic particle, and every other variable in the universe, that may not be all we need to predict the future. It isn't a question of whether it's practical to predict the universe with certainty: it clearly isn't. The question is whether it's theoretically possible to do so, and it isn't at all clear to me that the answer is yes.

'Deterministic' is not a fancy word for 'only one thing can happen at a time'. Even in a non-deterministic system, only one thing happens at a time. The only difference is that for a non-deterministic system, however complete our description of the state is, we cannot always predict the next state with certainty. It's not a question of hidden variables; it's that the fundamental rules that govern the system are probabilistic.

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Re: Predicting the Future

Postby daydalus » Thu Dec 06, 2007 3:40 pm UTC

The fact that both a particle's location and velocity can't be determined (quantum mechanics) doesn't disprove a deterministic universe. It only means we can't do the determining. Our best model for predicting the state of a particle is probability, but that doesn't mean the particle doesn't possess an exact vector at any point in time. It's just impossible for us to determine what that vector is.

Therefore, if we could magically obtain the vectors of all particles in the universe and knew the exact formulas under which they operated, we could simulate the universe. Hence determinism still holds...

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Re: Predicting the Future

Postby Indon » Thu Dec 06, 2007 4:27 pm UTC

daydalus wrote:The fact that both a particle's location and velocity can't be determined (quantum mechanics) doesn't disprove a deterministic universe. It only means we can't do the determining. Our best model for predicting the state of a particle is probability, but that doesn't mean the particle doesn't possess an exact vector at any point in time. It's just impossible for us to determine what that vector is.

Therefore, if we could magically obtain the vectors of all particles in the universe and knew the exact formulas under which they operated, we could simulate the universe. Hence determinism still holds...


Perhaps, if the universe were in fact deterministic. We, as you note, don't have the ability to verify if it is because all the information we get implies a nondeterministic universe.

Sure, particles may have definitive locations and velocities that we just can't determine 'cause we aren't awesome enough. Or, particles might honestly not have definitive locations and velocities at the same time, and what we're seeing is the best we, or any being, will ever get.
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Re: Predicting the Future

Postby quintopia » Thu Dec 06, 2007 4:57 pm UTC

Nath wrote:'Deterministic' is not a fancy word for 'only one thing can happen at a time'. Even in a non-deterministic system, only one thing happens at a time.


This is poor wording on his part, but that's not what he meant. He's saying, rather, "any given event can have only one outcome (with probability 1)"

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Re: Predicting the Future

Postby The Mighty Thesaurus » Thu Dec 06, 2007 5:00 pm UTC

Are we doomed to repeat this conversation over and over? Damn you, determinism!
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Re: Predicting the Future

Postby Indon » Thu Dec 06, 2007 5:07 pm UTC

The Mighty Thesaurus wrote:Are we doomed to repeat this conversation over and over? Damn you, determinism!


Only if the total state of the universe should ever match a previous total state of the universe, combined with determinism, will events ever definitely repeat.
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Re: Predicting the Future

Postby TizzyFoe » Thu Dec 06, 2007 5:19 pm UTC

perhaps this would be best for another thread, but does anyone think that free will is still possible in a deterministic world? Personal i'd say no, but i guess it depends on how exactly define free will.
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Re: Predicting the Future

Postby daydalus » Thu Dec 06, 2007 5:51 pm UTC

quintopia wrote:
Nath wrote:'Deterministic' is not a fancy word for 'only one thing can happen at a time'. Even in a non-deterministic system, only one thing happens at a time.


This is poor wording on his part, but that's not what he meant. He's saying, rather, "any given event can have only one outcome (with probability 1)"


Well, unless you follow the multi-universe "theory" - whereby every possible decision a particle can take in turn "splits" the universe. (http://en.wikipedia.org/wiki/Multiverse ... um_physics). So we end up with all possibilities occuring throughout the multiverse.

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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 7:03 pm UTC

daydalus wrote:The fact that both a particle's location and velocity can't be determined (quantum mechanics) doesn't disprove a deterministic universe. It only means we can't do the determining. Our best model for predicting the state of a particle is probability, but that doesn't mean the particle doesn't possess an exact vector at any point in time. It's just impossible for us to determine what that vector is.

OK, this is getting repetitive. True, the uncertainty principle by itself does not necessarily prove that the universe is fundamentally non-deterministic. However, my previous sentence does not prove that the universe is fundamentally deterministic.

daydalus wrote:Therefore, if we could magically obtain the vectors of all particles in the universe and knew the exact formulas under which they operated, we could simulate the universe. Hence determinism still holds...

This claim is baseless. Not necessarily false, but baseless. "Hence determinism holds"? Why assume that the universe is deterministic just because we don't currently have proof to the contrary?

That said, from what we know right now, it does seem that the universe is not deterministic, and it isn't just a matter of not knowing all the right vectors and formulae. The uncertainty principle isn't the only consequence of quantum mechanics. It has been experimentally shown that quantum mechanics cannot be explained away with hidden variables (unless information is being transmitted faster than light).

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Re: Predicting the Future

Postby 22/7 » Thu Dec 06, 2007 7:22 pm UTC

Just because the idea has been stated a couple of times, I'd like to ask for a citation for it. The idea, by the by, is 'all the evidence points to the world being non-deterministic.'
Totally not a hypothetical...

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daydalus
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Re: Predicting the Future

Postby daydalus » Thu Dec 06, 2007 7:55 pm UTC

Nath wrote:This claim is baseless. Not necessarily false, but baseless. "Hence determinism holds"? Why assume that the universe is deterministic just because we don't currently have proof to the contrary?

That said, from what we know right now, it does seem that the universe is not deterministic, and it isn't just a matter of not knowing all the right vectors and formulae. The uncertainty principle isn't the only consequence of quantum mechanics. It has been experimentally shown that quantum mechanics cannot be explained away with hidden variables (unless information is being transmitted faster than light).


Lots of this stuff is over my head, seems to lean to the side of determinism.

http://en.wikipedia.org/wiki/Determinis ... al_physics

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quintopia
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Re: Predicting the Future

Postby quintopia » Thu Dec 06, 2007 8:32 pm UTC

Nath wrote:t has been experimentally shown that quantum mechanics cannot be explained away with hidden variables (unless information is being transmitted faster than light).


Or the law of the excluded middle doesn't apply to quantum mechanics or there does not exist a non-experiential reality. . .

but yes, non-locality is the most intuitive/interesting saving constraint. There need be no reason for information to travel as slow as light.

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wst
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Re: Predicting the Future

Postby wst » Thu Dec 06, 2007 9:47 pm UTC

Rook wrote: If you asked for a prediction of what a person or persons were going to do at some future date, simply receiving the answer could change events. For example, if you asked 'will I buy item-x' tomorrow, regardless of the answer you would buy item-D (which is any item not mentioned), just to be a bitch.


Isn't there something in one of the laws of physics (not the thermodynamic 3, you will know what I mean later this post) (and I can't remember the name of it, and I don't want to look a total muppet) that basically says that particles do one thing whne they're observed, but if they're observed they don't do it, because the observation somehow affects them?

Well, maybe it works into future events as well. Basically meaning it's impossible to predict the future because if you say, "This will definitely happen" out loud, and think "I'm going to bluff science, actually this will happen", it will do neither just to be (quoth Rook) 'a bitch'.
Anything I said pre-2014 that you want to quote me on, just run it past me to check I still agree with myself.

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Nath
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Re: Predicting the Future

Postby Nath » Thu Dec 06, 2007 10:15 pm UTC

22/7 wrote:Just because the idea has been stated a couple of times, I'd like to ask for a citation for it. The idea, by the by, is 'all the evidence points to the world being non-deterministic.'

That isn't the idea I've been trying to convey. What I've been trying to say is this:
"Not all evidence points to the world being deterministic."

The question hasn't been settled. That said, I can cite at least a couple of papers in favour of non-determinism:
http://puhep1.princeton.edu/~mcdonald/examples/QM/stapp_ajp_65_300_97.pdf
http://www.nature.com/nature/journal/v446/n7138/abs/nature05677.html
If you want more, both seem to have some interesting citations.

daydalus wrote:Lots of this stuff is over my head, seems to lean to the side of determinism.

http://en.wikipedia.org/wiki/Determinis ... al_physics

It's over my head, too -- and that seems reason enough not to assume determinism without further research. However, that Wikipedia article doesn't seem to lean towards determinism in the sense that we are discussing. It is deterministic in the sense that (given perfect information) you can deterministically predict the wave function of a particle, but the wave function itself is still probabilistic. But I might be misunderstanding that.

quintopia wrote:Or the law of the excluded middle doesn't apply to quantum mechanics or there does not exist a non-experiential reality. . .

but yes, non-locality is the most intuitive/interesting saving constraint. There need be no reason for information to travel as slow as light.

Well, the law of excluded middle kind of follows from how you define your logical rules. It isn't determined by your physical theory. However, you do make the valid point that there are several caveats to any claim that reality is fundamentally non-deterministic. As I said, the question has not been settled. It's just that there's no reason to assume that things are deterministic.


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