I'm confused

[Satya]

It proves that everything is weird. Way to weird to wrap your head around. Go with it.

[jotabe]

Standard interpretation of Quantum Mechanics (Copenhagen school) rules out determinism. Quantum indeterminacy doesn't arise from our inability to measure it, but it would be a property of the Physical world itself. Phenomena like quantum entaglement gives credit to this interpretation, otherwise quantum entaglement would imply that information could travel faster than light.

[CezeN]

Standard interpretation of Quantum Mechanics (Copenhagen school) rules out determinism. Quantum indeterminacy doesn't arise from our inability to measure it, but it would be a property of the Physical world itself.

Can you explain this more indepth? (sorry, have not taken physics yet)
It seems like you're saying that the Universe is random by nature.

However, though this isn't a super credible source
http://en.wikipedia.org/wiki/Quantum_Mechanics

The time evolution of wave functions is deterministic in the sense that, given a wavefunction at an initial time, it makes a definite prediction of what the wavefunction will be at any later time.[34] During a measurement, the change of the wavefunction into another one is not deterministic, but rather unpredictable, i.e., random. A time-evolution simulation can be seen here.[1]

The probabilistic nature of quantum mechanics thus stems from the act of measurement.

Which I interpret to mean that it's only probabilistic to us because our experiments screw with whatever pattern.
Not to mention, someone on another forum compared it to:
Basically it's saying something along the lines of this: since all human eyes can only process a small range of lightwaves, only the lightwaves we can see exist. The point being that there are many things that we cannot perceive and so just because we cannot perceive the universe in its entirety and how each atom moves in relation to each other doesn't rule out the possibility of determinism on a higher consciousness that can.

Which makes it sound as if it's like scientists are saying "we can't predict it or see the pattern, thus no one can".

[jotabe]

No, it's doesn't mean it like that. This is the deal: what a particle, or a wave, or whatever, is... what is it? What is that defines it? It's the wavefunction.

A wavefunction will give you all the properties of any particle, if you know how to talk to it. But... you can't measure a wavefunction. We can only measure certain properties, properties that make sense to us, like position, momentum, energy... but they aren't part of what the particle really is.
If we try to measure those other properties, what we do experimentally is collapsing that wavefunction, projecting it into the property we are looking for. And here comes the probability: due to the mathematical nature of how wavefunctions work, you will have an uncertainty in the magnitude you measure. This uncertainty doesn't come from a limitation of the measurement devices, but from the mathematical nature of the wavefunction itself.

It comes from the act of measurement, yes, but because the act of measurement is forcing the wavefunction to give us one piece of information, losing the rest.

I advice to read this follow up article in the wiki:
http://en.wikipedia.org/wiki/Interpreta ... _mechanics

Btw, wiki is very reliable when it comes to science.
When it comes to hot topics, it isn't less reliable than any other encyclopedia, and it's a lot more reliable than blogs, pundits and otherwikis.

[CezeN]

Oh okay. So now, can you tie up how all of this has to do with free will and determinism?

I'm going back and forth between Determinism might be possible and Determinism according to science is ruled out. I'm getting opposing viewpoints from people in different forums.

He's saying this:

It's saying that the human mind doesn't possess the ability to know everything about the universe in a given moment and thus can't know what is going to happen. Thus we can only predict a set of outcomes and list their probability. But they wrongly conclude since the human mind can't reach that level of awareness that determinism isn't possible.

tl;dr* Humans are stupid

You're saying that
tl;dr* Determinism is bs sciencewise, wavefunctions are random, probabilistic because of there mathematical nature. *insert other stuff that I don't/am too lazy to understand*

Which one is true?

*too long didn't read

[jotabe]

The other guy you are quoting is thinking about chaos theory type of indeterminacy. Non-linear, complex systems. In such systems, precise outcomes are unpredictable because you would need to know all variables with absolute accuracy, and that's an unrealistic expectation.
But even chaotic systems, like atmospheric physics, for example, are perfectly deterministic if you reduce the number of variables and the time scale to something computable.

On the other hand, quantum indeterminacy comes from the very nature of things, to the mathematical structure of the universe. Particles don't have positions, but if we "violate" a wavefunction to have it tell us the particle position, the wavefunction will give us a probability distribution.

I'd like to note that while things like position and momentum are probabilistic, and hence not-deterministic... the calculation of probabilities is perfectly deterministic. So we can know with perfect accuracy the probability of events taking place.

[Graff^]

Now I'm confused.........if you'd be so kind to rephrase that.

[jotabe]

Let's see: indetermination can come from both classical systems and quantic ones. But the nature is different.

In classical systems (that is, systems that are perfectly described by the laws of classical mechanics), indetermination comes from non-linearity. What are non linear systems? Let's try an example:

Think of making a box on a very smooth surface, with a certain friction. You push that box and give it a starting speed, and it will slide for a certain length, that you can calculate very easily. This length depends on the initial speed you give, and the friction with the surface. The speed and the friction are completely independent from each other: this is a linear system.
Now, instead of sliding the box over a surface, you throw it to the air, only subjected to the gravity and the air friction. The point where the box will land can be determined by knowing the initial speed (and direction) you imprint, and the air friction. BUT air friction depends on the box shape, on the air density and on the speed of the box! So we cannot separate the initial speed contribution from the friction contribution. This is a non-linear system.

Non-linear systems are systems with feedbacks among variables, which makes analytical solving impossible for more than 2 particles. So when extended to a great number of particles (think of weather forecast) we have to use other methods to predict what will happen: rather than solving it, we study how the system behaves, where the solutions exist and where they don't exist, and how solutions evolve along time. This is the indetermination: we can't solve it, we can only find probabilities that one initial situation will lead to another.
On the other hand, the individual behaviour of each particle of these systems is perfectly deterministic: if we had a sufficiently large computer to computer every particle, we could have solutions as accurate as we would like.
So, indetermination here stems from our lack of computing power and our lack of patience.

On the other hand, indetermination in the quantum mechanics stems from the very nature of things. Particles do not really posses momentum or position, they are just convenient variables, so calculating them accurately is not possible. A good way to see it is realizing the particle-wave duality: all particles are actually highly localized waves (wave packets). Think of a particle: if you want to know its position exactly, you take a pic of it with very short exposure. With that pic you can tell its position... but nothing about its speed. Now think of a wave: does it have a position? No, all you can know about a wave is the amplitude, the period, and the speed (in wave mechanics, these three things make up the moment of the wave).

So, if we try to force-in our classical mechanics, the answers we will get will be only probabilities. "Real" properties in Quantum Mechanics, like energy levels, transitions, matrix elements and other such blasphemies, have perfectly accurate values, on the other hand.

Edit: i have the nagging feeling i just made it worse to understand

[starlooker]

Jota, I am starting to develop the kind of crush on you that I used to have on Ollie when he would talk about math.

I love people who know their stuff and like to talk about it.

[jotabe]

lol
I would like to be able to lay clearly some of the more unfamiliar points of science... i like popularization ^_^ But often get the feeling that my way of explaining isn't up to the task... a matter of practice, i guess, lol.
Rahl knows his stuff, he does

[Graff^]

Ok that clears it up thanks

[Karachi123]

Are you satisfied now?

[Satya]

I'm surfing a wave of particles.

[Psudo]

This is the impression I get of virtually all quantium mechanics, as explained by xkcd:

I'm sure it makes more sense than that to other people, but it never has to me.

[jotabe]

Unlike strings, Quantum Mechanics has lots of real-life implications (unlike strings lol): laser, semiconductors (hence integrated circuits and chips) are just 2 things you likely have at less than 50 cm from yourself atm.

[elfprince13]

To explain this somewhat more briefly and with less of the technical jargon, but also to touch on some different points, the understanding of nondeterminism from a classical mechanics perspective is that while human beings may not be capable of determining precisely how a complex system will play out, it is at least theoretically calculable given a powerful enough computer simulation and a proper understanding of the physical laws governing the interactions in that system. This idea plays out in the study of chaos theory, and (for you sci-fi buffs out there) forms the basis of Isaac Asimov's Foundation series with the development of psychohistory.

On the other hand quantum mechanics can not be deterministic without violating either "counterfactual definiteness" (a fancy way of saying that measuring the same thing will always produce the same result) or the principle of locality. Assuming locality you end up with either the standard Copenhagen Interpretation of Quantum Mechanics (which is nondeterministic in the truest sense) or the Many-Worlds Interpretation (where all possible universes develop simultaneously, but with the appearance of nondeterminism from within any given universe). Assuming counterfactual definiteness, you end up with the Bohm interpretation of quantum mechanics (which is deterministic, but nonlocal) which says that while the outcome of a quantum experiment is deterministic, the initial configuration is not controllable by the experimenter giving an appearance of random results. These interpretations are empirically indistinguishable which lives you to decide between them on philosophical grounds.

Over in the free will topic I posted a link to a talk (with an admittedly theological bent) I gave at camp last summer which explains the scientific understanding of determinism at a reading level targeted for 14 year olds with no scientific background.