optimist

It was not our inability to predict something that lead to my abandonment of determinism. The two-slit experiment says much more than that! Here is an idealization of the experiment: A particle has a 50/50 probability of going through either slit (A) or (B). Then, if it goes into slit (A) it will have a 50/50 chance of either hitting spot (i) or spot (ii) on our detector behind the two slits. If the particle goes through slit (B) it will have a 50/50 chance of hitting either spot (ii) or spot (iii).

..........|
..........(A).....(i)
0-........|.......(ii)
..........(B).....(iii)
..........|

(ignore the dots (.), I had to use them so the diagram would post right)

Now, the pattern we would expect on the wall if we fired 20 particles over a period of time (one at a time) is about (i): 5 (ii): 10 and (iii): 5

Think about this, and make sure you understand that before you read on. Okay, now I'll tell you what really happens.

For this thought-experiment our results would actually be (1): 10 (ii): 0 (iii): 10 !

Why? We only sent one particle through at a time, so what could have changed the particles path? Believe it or not (believe it, because it's true), the probability from door (a) to spot (ii) cancelled out the probability from door (b) to spot (iii). How can probabilities hit one another and cancel each other out?!?

Here is a kicker, if you close slit (B) you get the expected pattern of (i) 10 and (ii) 10. But if you open slit (B), simply because you have introduced a new possible path, the particle moves differently.

Disclaimer: This is not actually how the experiment is done or how particles "probabilities" interact, but it is a close enough approximation and it is easier to understand it this way. If you want more I (highly) suggest reading Richard Feynman's Character of Physical Law. It only has one chapter on Quantum Physics, but it is very well done. More importantly, the whole damn book is great. Especially the last chapter on "Seeking New Laws." The book should be cheap ($2-$10 bucks).

This does not "disprove" determinism, but it at least demands my suspension of belief. The fact that probabilities can affect each other suggests they are more than just a lack of knowledge. "Even God does not know where the particle is going to go." Is a quote I heard and forgot who it is from...Hawking maybe?

I am currently close to "agnostic" towards determinism. (well, actually I am leaning towards not believing in determinism at all). The "Multi-World-Interpretation" (MWI) is an attempt to get rid of this indeterminism by introducing parallel universes… however this idea carries a lot of metaphysical baggage (to say the least!). I will not discount MWI on that count, but still indeterminism seems to be the more accepted interpretation of the two-slit experiment.

Anyway, this does not result in the existence of freewill either! This indeterminism takes place only on the smallest scale. There is no reason to think it affects our brains functioning in anyway. "Shrödinger's Cat" is suppose to be an illustration of what happens on the ultra-small scale, not to real cats! The reason is because the particles have to be isolated to act indeterminately (or be in two states at one time as in the case of Shrödinger's Cat). A cat has billions of particles in it all interacting with one another and so a can will not find itself half-dead and half-alive.


Freewill comes into a lot of trouble for other reasons anyway (e.g. I understand what chance is, and I understand what order is…but what is freewill?). I am fairly agnostic towards freewill right now too, but again I tend to think it does not exist.

As a last comment, since we are on the subject of Quantum Physics… on the subject of observation causing the collapse of the particle: I do not, nor do I think many scientists do now or ever, think observing a particle affects it! I think bouncing photons against it does. It isn't the human eye or brain that causes particles to "collapse," but the things we have to do to the particle so our brain can see it. When a physicist says observing the particle caused it to collapse, he is referring to the processes that are involved with making the particle observable.

This is all very complex stuff and so I don't know how well I've done at explaining it (sorry).

[ July 22, 2002: Message edited by: optimist ]</p>

Kharakov

Hi optimist-

The 2 slit experiment was done to verify that electrons behave as both particles and waves. I don't understand how this influences your belief for/against determinism.

Our inability to accurately know something about particles would be part of the determistic nature of the universe- it is outside of our hands. Maybe at some future time, the right configuration of ideas, genetics, experiments, etc. will come together and give us the knowledge of what particles are doing, but this will be determined by whatever forces bring about that action. And that knowledge will in turn change the way we interact with the universe (or maybe some other factor will intervene and prevent our use of that knowledge). The knowledge of determinism comes from the fact that if something influences the outcome of something, it is part of what determines the outcome. If something does not have any influence upon the outcome on something, it does not have an effect upon the outcome. How can things be any other way? Even if things are determined by random events, are they not still determined?

-k

optimist

"The 2 slit experiment was done to verify that electrons behave as both particles and waves."

Waves of probability! You left out the important part, how can probability be a physical wave!? Your understanding of the two-slit experiment is what I first thought it to be, but it is much weirder. I remember thinking to myself, "this just means particles turn into waves, okay good. Determinism is right." Only later did the full meaning of the experiment dawn on me (after a few more books).

"Even if things are determined by random events, are they not still determined?" I think you are getting trapped in word use here. Yes the event is determined, but which event is not determined. In a deterministic universe if event [A] happens, event [B] will follow. From our point-of-view, in the case of a coin toss, [A] happens (flip of the coin) and either event [B] (heads) or [C] (tails) will occur. But, in the case of a coin toss whether [B] or [C] occurs is only apparently random since the randomness is only a function of our ignorance. We do not know exactly how the coin was tossed, and so we cannot predict whether [B] or [C] will result; but "God" knows the result. The first coin toss [A] does determine event [B]. The next coin toss has a different angle to is so it (event [D]) causes event [C] instead. A coin toss is always fully determined.

In the case of the 2-slit exp. the randomness is not a function of our ignorance, event [A] happens and either [B] or [C] could occur. To get rid of the "God" part: "Even the particle doesn't know where it is going." This is indeterminacy. If you want to say the event at time2 (either [B] or [C]) is determined by event at time1 (event [A]) you are correct, but event [A] does not determine which event (B or C) occurs. This is indeterminacy. Not complete indeterminacy, but still indeterminacy. Complete would mean event [A] could cause any event ([B, C, D...Z]).

Even though it is not complete indeterminacy, it is still a big different from the complete determinacy we are use to in our world of large objects. If I throw a ball its path is completely determined even if I don't know it. If it is a particle, its path has several choices and which is not determined at all!

In contrast, Chaos Theory is not indeterminate at all. Chaos Theory is about "Deterministic Chaos." This is about events so complex we are unable to predict the results, but in this case the events are still completely determined from the "God's Eye view."

[ July 22, 2002: Message edited by: optimist ]</p>

Kharakov

optimist-

moved this to the new thread.


-k

[ July 22, 2002: Message edited by: Kharakov ]</p>

WJ

Nial!

You said:

David Matthews...
Define "rational" and "reason".

Here's a couple relavent definitions I've found:

Reason: The intellectual ability to apprehend the truth cognitively, either immediately in intuition, or by means of a process of inference.

reason:
4. The capacity for logical, rational, and analytic thought; intelligence.


What would classify a belief as "rational" rather than "irrational", for theism or atheism?

[end quote]

I was waiting for Dave's response and didn't see one, so I thought I'd try one. To attempt an answer at your last question, your definition of common everyday reason is a good start. And that is by way of *inference*. I believe both theism/atheism relies on inference for its conclusion or choice to believe/disbelieve. I further underscore that point because neither 'inference' is 'wrong' by logical standards.

The 'leap' as it is commonly referred to is made by inference. That also relates to the cosmological argument for EOG. In that vein, it is truly a choice.

Dave? comments?

Walrus

99Percent

Name one God concept that can be plausible to exist.

optimist

The key word here is "plausible." Here is a possible God concept: A conscious thing that has always existed and is responsible for the creation of this universe.

While it is possible, it is not plausible in any way. Not more so than the idea that 102 monkeys are responsible for the creation of this universe.

Excluding possibility is unimportant really. We live our life's by excluding plausibility. I do not pray to the 102 monkeys because I have excluded their plausibility.

slacker

God's only excuse is that he doesn't exist. -- Stendahl

Totalitarianist

The omnipresent, non-sentient laws of nature?

optimist

I would think "sentient" would be a requirement of anything resembling the word "god." You can lessen his powers, make him a woman, say someone else created the universe (maybe not all those together), but you cannot make him non-sentient without inventing a new use of the word God.