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#41
11-06-2005, 02:17 AM
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Re: How can randomness possibly exist?
[ QUOTE ]
[ QUOTE ] At present the evidence is that at a quatum level there IS randomness, so to base an argument on "I can't think how .." seems to leap ahead of the evidence. Now, with the M-string brane theories perhaps some hidden variables will show up ( there's been some strong cases made that they can't show up ) [/ QUOTE ] I talked to a physics major who's studying quantum right now, and the way he discussed it, it said it is more likely that the randomness is merely apparent due to the lack of precision in our measurement tools, and hidden variables. Even in the scientific world, the jury is still out. [/ QUOTE ] I have a Ph.D. in physics, and I can tell you unequivocably that this is incorrect. Randomness at the quantum level is not due to lack of precision in our measurement devices. [ QUOTE ] I'm not saying that there isn't true randomness at the quantum level. I'm not saying there is. I'm saying that I don't know, and that you probably don't either. Quantum physics gets tossed around like a hacky-sack whenever there's a deterministic argument by people who really don't know dick about it. [/ QUOTE ] It's been a while, but I know a little bit more than dick about it. [ QUOTE ] On both occasions when I held a discussion group IRL on free will vs determinism, it ALWAYS boiled down to the libertarians saying "science says I'm right" and the determinists saying "no it doesn't." It will be a VERY long time, if ever, that science conclusively proves the existence of randomness that is not attributable to lack of precision in measuring tools. I think we need to accept that this is something that is a little beyond our comprehension. [/ QUOTE ] Think about it this. You have a sample of some radioactive material. Each atom in the material has some probability of decaying in the next x minutes. But there is no possible way to predict when an individual atom will decay. You can measure each atomic decay essentially perfectly. There is no imprecision. Either an atom pops off, or it does not. Uncertainty in your measuring device has no bearing on the process at all. 
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#43
11-06-2005, 02:38 AM
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Re: How can randomness possibly exist?
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I think of the universe the same way I think of a computer program. The universe has a set of laws (or algorithms) that determine how the matter that the universe is made up of moves about. Just like an algorithm, someone can look at the "script" of the universe and predict what will happen next. [/ QUOTE ] It sounds to me like you have very little imagination. We have been designed by nature and evolution to have a fairly intuitive understanding of approximately 1000 m length scales in a fairly low gravity system. We have deduced many surprising things that in retrospect we call "intuitive", but how "intuitive" is Electricity and Magnetism if it took us 10000 years to develop? By the way, there are perfectly well understood, simple, and predictable mathematical models that can be used to generate "random" numbers. I believe that currently, there is no strict mathematical definition for "random", although there are a number of tests that we believe "random" numbers should satisfy. This basically comes from the fact that mathematically we cannot define something negatively (i.e. there are huge consistency problems if we define random as being the lack of repeating patterns). So the fact that we have an intuitive idea of "random" probably means that it is somehow useful. I also think the idea that there must be some final simple theory beneath everything is also a quest for God in some sense. I will believe in it when they find it.
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#44
11-06-2005, 02:47 AM
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Re: How can randomness possibly exist?
[ QUOTE ]
[ QUOTE ] I guess unpredictability given infinite knowledge is what I'm talking about. I don't think such a thing exists. I think the entire outcome of all the particles in the universe has already been determined. We certainly don't have the knowledge to predict that outcome, but hypothetically, the answer exists. [/ QUOTE ] Infinite knowledge is not possible. We know this to be true. Infinite knowledge, of course, would forbid randomness. Your problem is not with randomness but your belief that infinite knowledge is possible. [/ QUOTE ] This is a very interesting point, but I'm not sure that I agree with your conclusion. It's reasonable to assume infinite knowledge is not possible to obtain. I'm not sure what infinite knowledge entails. Let's make a bold assumption (that almost certainly isn't true) that the universe is nothing but an infinite number of locations, and those locations either have or don't have the smallest possible unit of matter. The amount of matter in the universe is finite, so if we simply map out all the known peices of matter in the universe, we are working on a finite scale. Obviously we cannot do this for every particle in the universe, but theoretically, we could do it for any particle in the universe. If every particle is mappable, that means that the information that would lead to infinite knowledge is out there. It wouldbe impossible for humans to ever obtain all of that data, but it's out there. I dont think that whether or not we can gather all of the information is relevant. The point is that it's out there. I oversimplified things w/ my false assumption, but hopefully you get what I'm trying to say. I'm not sure how to phrase it better.
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#45
11-06-2005, 02:49 AM
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Re: How can randomness possibly exist?
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If you re-read my earlier post, I tried to create a simple universe. This universe contains a bag, two marbles, and me. I have "infinite knowledge" of the system right? All I have to do know is show that there is something about the system that I cannot predict. I chose to use the result of 100 choices of the marble from the bag. [/ QUOTE ] The bag would be transparent if you had infinite knowledge. You would always know which color the marble would be.
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#46
11-06-2005, 02:57 AM
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Re: How can randomness possibly exist?
Do you see how far from our actual universe your "model" is? I don't think there are any conclusions one could draw from your model that would actually coincide with reality. Your analogy is sub-par.
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#47
11-06-2005, 03:02 AM
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Re: How can randomness possibly exist?
[ QUOTE ]
Alternatively I could show that there is no such thing as "infinite knowledge." You talked about the Heisenberg Uncertainty principle before. One version of this principle states that if you know one thing really precisely(position) then that knowledge comes at the expense of the precision of knowledge of another thing(momentum). In effect, no observer can know everything about a system to begin with, so there is no challenge to the existence of randomness. [/ QUOTE ] Actually, the uncertainty principle itsself doesn't have much to say about the availability of information. I could tell you complete information about a quantum system without violating the UP. The UP simply says that certain questions (like knowing exact position and momentum simultaneously) are undefined in the context of quantum mechanics. You might know a state exactly -- but it will simply never turn out to be an eigenstate of both position and momentum, because states like those don't exist in the theory.
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#48
11-06-2005, 03:06 AM
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Re: How can randomness possibly exist?
Not sure. I could probably be misinterpreting what he said. However, the uncertainty principle as you described it is suggestive of apparent randomness, not true randomness. It outrules practical determinism (I don't think anyone believes in that though), but I don't think it effectively disproves it.
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#49
11-06-2005, 03:07 AM
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Re: How can randomness possibly exist?
[ QUOTE ]
Do you see how far from our actual universe your "model" is? I don't think there are any conclusions one could draw from your model that would actually coincide with reality. Your analogy is sub-par. [/ QUOTE ] Yes, I was hoping you would understand where I was going with that, but I guess not. Basically I'm just saying that the fact that we will never be able to gather infinite knowledge as people does not matter. The fact that the solution is out there is what matters, even if we will never have the complete solution.
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#50
11-06-2005, 03:13 AM
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Re: How can randomness possibly exist?
I knew there was a reason I'm an experimentalist. Of course I could construct a quantum system and completely describe any state I want to. Also of course I'll never be able to measure them unless they fit the selection rules etc...(i.e. they won't be an eigenstate of the system).
FWIW, I really meant to talk about DeltaX in my post not xbar. My phrasing always lapses when I type things unless I really get down to editing...
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