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#20825 - 04/24/07 04:37 PM Questions of physicists.
TheFallibleFiend Offline
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Registered: 06/08/05
Posts: 1940
Loc: http://thefalliblefiend.blogsp...

1. Is the universe actually random at a fundamental level or is the randomness only "apparent"?
2. Does QM imply a random universe?
3. Does "random" just mean "we don't understand this"?
4. Does "indeterminism" imply randomness?




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#20826 - 04/24/07 04:50 PM Re: Questions of physicists. [Re: TheFallibleFiend]
DA Morgan Offline
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Registered: 10/17/04
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1. I am not sure the intent of the question so it is hard to answer.

Certainly when viewed through the lens of the Casimir Effect one could say it is. But when viewed through the lens of a quark or electron or photon might answer differently.

My feeling is that we are looking at a hologram generated by a recursive fractal formula. Look to closely and you see the hologram. Nothing but wavy lines and pixels. Look at the projection and you get space. Add another dimension and perhaps also time.

2. No.

3. In the case of what you are asking ... possibly ... we just don't know but the universe, to me, doesn't look like the result of throwing a stack of cards into the air. So at some level it is definitely not.

4. No.
_________________________
DA Morgan

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#20831 - 04/24/07 07:32 PM Re: Questions of physicists. [Re: TheFallibleFiend]
redewenur Offline
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Registered: 02/14/07
Posts: 1840
1. Is the universe actually random at a fundamental level or is the randomness only "apparent"?

On the macro scale, the universe doesn't appear to be random because 'probability' averages out quantum events. The question appears to reduce to: -

"Can a single quantum event be random?" - If so, then the universe is random (and indeterministic).

My own opinion - I still don't know. "Random" is a subset of "unpredictable". Unpredictable events are not necessarily random.
_______

2. Does QM imply a random universe?

It appears that quantum mechanics actually defines the universe as unpredictable; but it doesn't follow that it's random (see answer 3).
_______

3. Does "random" just mean "we don't understand this"?

Maybe that is what it means - that we just can't identify a cause

Does the fact that a quantum event appears random really prove that it is? I doubt it, but it may never be possible to prove that it's not.
_______

4. Does "indeterminism" imply randomness?

Indeterminism, by definition, requires truly random events. Unpredictability and indeterminism are quite different. The former doesn't require random events, the latter does.

_________________________
"Time is what prevents everything from happening at once" - John Wheeler

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#20903 - 04/25/07 02:52 PM Re: Questions of physicists. [Re: redewenur]
TheFallibleFiend Offline
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Registered: 06/08/05
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thanks much for responses...hoping for more.
k

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#20929 - 04/25/07 09:35 PM Re: Questions of physicists. [Re: TheFallibleFiend]
dr_rocket Offline
Member

Registered: 12/06/06
Posts: 196
Loc: Palo Alto, CA, USA
Hi FF,

I've been a little busy lately, but I couldn't pass this one up.


1. Is the universe actually random at a fundamental level or is the randomness only "apparent"?

The answer to this question is not known.

2. Does QM imply a random universe?

It does not. QM was formed to describe the universe. Certain aspects of the universe seem to be governed by the rules of chance and these rules are captured by QM. (See 4)


3. Does "random" just mean "we don't understand this"?

The word "random" is too non-specific. For example, random number generators used in all sorts of computer software are very much non-random. They are simple computable functions with an output that to all intents and purposes look random.

In the same way how could you tell if the universe is random or deterministic? Perhaps you see the logical difficulty with this. Suppose you say "random" = "we don't understand". Then when you eventually get to a point where you don't comprehend something and you ask is it random or have you reached my limits there is a problem. Is it really the "real random" that hops around - well randomly? Is it something that is really incomprehensible with an explanation you cannot take in? How could you know.


4. Does "indeterminism" imply randomness?

No. This has nothing to do with randomness. Indeterminism, of the Heisenberg kind, comes from the facts of quantization and duality.

You really have to be careful when discussing ideas like randomness, indeterminacy, uncertainty. This is especially true if you are interested in the free will/determinism dichotomy. Physicists use these terms differently than in common usage or even philosophical discourse.

One observation that might help is that the Schrodinger equation, a very important part of QM, is completely deterministic in that it describes the evolution of the wave function. The form Schrodinger equation reminds me of a diffusion equation. (The non-relativistic time dependent one.) Once a system has been "prepared" to be in some state, then this state will evolve with no uncertainty at all according Schrodinger equation.

If you are from the Copenhagen school you would say that the wave function has no independent reality. To get anything from the wave function you use a mathematical trick (devised originally by Max Born) to get a probability density function from it. This is were all the probability stuff comes from in QM. (I'm glossing over this, but this is the general idea.)

The Copenhagen interpretation of QM is not the only game in town: Bohm's hidden variable; the Relational interpretation; the Transactional Interpretation; various Modal Interpretations; Many-Worlds; many collapse interpretations and so on. There are many more and there is no agreement.

Dan thinks that the universe is a hologram. If I am not mistaken this idea was originally put forward by Michael Talbot in a book called "The Holographic Universe" which appeared in 1991. This was based on a combination David Bohm's ideas on hidden variables and the holonomic brain theory of Karl Pribram. Bohm was a theoretical physicist and Pribram a neurophysiologist. I have found that some of Bohm's calculations are suspect and most physicists don't believe in hidden variable.

The problem with this approach is that once we find the projector and the screen these two things still need to be explained. What are they, where are they, how did they come about? Such a theory doesn't explain anything it simply transfers a mystery to another place. I have no problem with infinite regress, but it still begs the question is it a shell game. (Sorry Dan, no offense meant - I just don't agree with you on this.)

I hope this helps you FF.Well I should get back to work. (BTW: there is value in the saying that one should always look busy. You get more chances for afternoon naps that way.)

Dr. R.

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#20930 - 04/25/07 09:58 PM Re: Questions of physicists. [Re: TheFallibleFiend]
redewenur Offline
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Registered: 02/14/07
Posts: 1840
TFF

To quote Dr.R.
"You really have to be careful when discussing ideas like randomness, indeterminacy, uncertainty. This is especially true if you are interested in the free will/determinism dichotomy. Physicists use these terms differently than in common usage or even philosophical discourse."

His initial answer to Q.4. is the physicists answer. Mine is the philosophers answer. Take your pick.

_________________________
"Time is what prevents everything from happening at once" - John Wheeler

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#20935 - 04/25/07 11:12 PM Re: Questions of physicists. [Re: redewenur]
TheFallibleFiend Offline
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Registered: 06/08/05
Posts: 1940
Loc: http://thefalliblefiend.blogsp...
I'm aware that there are different definitions:

1. One common lay definition is: anything goes.
(not much of a definition, but laymen don't always define words in ways that are useful for scientific purposes)

2. Lacking structure or pattern.

3. Another common def: Being unpredictable.

4. Incapable of being compressed (info theoretic definition).

There are others I might think of, if I took a moment or used google. Anyway, take your pick which definition applies - just tell me which you're using.

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#20952 - 04/26/07 11:26 AM Re: Questions of physicists. [Re: TheFallibleFiend]
redewenur Offline
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Registered: 02/14/07
Posts: 1840
TFF, re question 4, and those words "indeterminism" and "randomness". Did you originally have a particular definition in mind? - i.e. did you think of them in 'absolute' terms, or merely as related to a particular discipline?
_________________________
"Time is what prevents everything from happening at once" - John Wheeler

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#20956 - 04/26/07 05:53 PM Re: Questions of physicists. [Re: redewenur]
TheFallibleFiend Offline
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Registered: 06/08/05
Posts: 1940
Loc: http://thefalliblefiend.blogsp...
On purpose, I left the definitions and leave them up to the discretion of each respondent, hoping he will explain what he means by the term.

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