The Universe is Deterministic

[martu]

Quantum uncertainty doesn't mean "Any old thing can happen"---it means something very specific about how a wavefunction can be broken down into a set of eigenfunctions; an observation forces it to leap (randomly) into one of these available eigenfunctions.

How is it random? If we're measuring position don't we force this eigenfunction to be 'picked'?

My language could be way off here I think I get the idea but I may have confused you with this, please shout if so and I'll try to rephrase.

 

[Tumbleweed]

Ok c was set at the Big Bang. If the Big Bang had been slightly different c would be (perhaps slightly) different. Does that answer your question?

Can you show me an equation for acceleration that does not include the mass of the object involved?

Yes, now I get it. F= ma. If light had mass there would have to be acceleration involved. Since there is no mass no acceleration is possible

 

[ben m]

How is it random? If we're measuring position don't we force this eigenfunction to be 'picked'?

My language could be way off here I think I get the idea but I may have confused you with this, please shout if so and I'll try to rephrase.

Let's stick with spin, if that's OK, since it's less complicated. Suppose I prepare a particle which is a quantum superposition of a spin-up eigenfunction and a spin-down eigenfunction. (This is very easy to do in practice.) When I try to measure the spin direction, the particle has to "choose" one and only one eigenfunction. Yes, I've forced it to make a choice, but which option it chooses is random. (Roughly speaking, Copenhagen interpretation, etc., YMMV, etc.)

The position-vs-momentum uncertainty is of the same nature---it so happens that when you try to measure a position, you force the particle into a position eigenstate; but that position eigenstate is a superposition of many, many different momentum states. This goes into the part of the problem I labeled "Suppose I prepare a particle ..." in the spin example; if you "prepare" a particle in a position eigenstate, you're also (like it or not) preparing a superposition of many momentum eigenstates. And vice-versa.

 

[sol invictus]

Well then this must mean that QM is inconsistent with relativity. Non local interaction is assumed* there isn't it?

No, it doesn't say that.

It says either the world is non-deterministic, or it's deterministic but one or both of those two assumptions isn't valid. In the deterministic case since we have strong evidence for (2), my bet is on (1).

If you agree, you have to accept one of two things:

(a) The world is non-deterministic. Many people find that hard to accept.
(b) The world is non-unique. Many people find that hard to accept.

 

[Tumbleweed]

Okay, being a big believer in free will and independence, QM leaves me no choice but to jump in and stake claim to a definition: I get to do the coin tossing that determines your reality and NOT the other way around. Gonna go down and get a copyright this very afternoon before its too late!

 

[Tumbleweed]

I have a set of numbers that are solutions to an equation. I know what some the numbers are. Lets say its x y and z. I have another set of numbers within the set that are solutions that are not known. By choosing x as a solution, -x becomes one of the unknown solutions. But it is a solution ONLY if x is chosen. If y is chosen -x cannot be an unknown solution, only -y can. Ditto for z. If only one known solution is chosen, there can be only one unknown solution.. But if two known solutions are chosen by two different choosers then two unknown solutions arise, each pertinent to the specific chooser. So reality is simply based on the known solution you choose, and only one solution allowed per chooser at a time. And if there is only one known solution, then everybody shares the same reality and they agree on what the unknown solution turned out to be
So basically I end up with a set that has the original xyz as known solutions with a second subset within the set that POTENTIALLY contains -x-y-z, dependent upon the choice of known solutions

 

[Xulld]

If you do not try to mix both epistemic and ontic descriptions into determinism it works just fine with QM at least that is what I get from this paper . . . perhaps I have misread somewhere . . . http://philsci-archive.pitt.edu/archive/00000948/00/HiddenDeterminismus.pdf

Its funny to me that I posted a paper by Hans Primas pages back that deals with this very notion and it is ignored in favor of detailed conversations regarding the nature of physics in specific circumstances and how that relates to a vague definition of determinism, when Primas suggests this kind of conversation is due to a categorical mistake. I was really looking forward to some professional physicists commenting on that paper.

I find this topic fascinating, but cant seem to understand how a concept like determinism can be understood at all in terms of predictions based on statistics. So I hesitate to use or acknowledge such a term that adds no new understanding and only elicits such confusion.


He states that:

On the other hand, there are ontically deterministic systems
which produce epistemically irreducible random outcomes.

Which makes me wonder how many of the specific examples used in this thread to support the notion of non-deterministic universe are ontically deterministic, its only what we can know that is random??

 

[Elf Grinder 3000]

Nope, neither of those statements are true. Simple examples:

1) A 211-Bismuth nucleus has two "choices" of how to decay; it can alpha-decay into 207-Tellurium or beta-decay into 211-Polonium. Totally distinct end states from identical initial states. There are many, many examples like this just in nuclear physics, and many more in any other quantum system. I know exactly what the choices are, but I don't know which one way the nucleus is going to go.

If there is only 1 force in my example universe and the force can act only 2 ways. And if it acts (-) on Bismuth then it decays to 207 but if it is (+) then it decays to 211. Maybe you can never predict which way the force will act on Bismuth.

But then what causes it to act (-) or (+). You seem to be saying that nothing causes the force to act (-) or (+). Or are you saying we just cant tell which way the force will act. If the force is (+) then it either happened because of some cause or it happened to be (+) for no reason "magic". I dont think QM says it happens for no reason this doesnt make sense?

If something caused the force to be (+) then the world is non-deterministic because when the force causing the (+) or (-) was set in motion only one possible state was possible given state A. Even though you cannot predict it.

 

[ben m]

But then what causes it to act (-) or (+). You seem to be saying that nothing causes the force to act (-) or (+).

Yes, nothing causes it to "choose" one or the other. As far as we can tell, this choice is perfectly, fundamentally random. As Sol points out, Bell's Theorem (discovered in the 1960s, heavily studied since then---including by people who fully expected to disprove it---and so far still standing) tells us, subject to the assumptions Sol mentioned, that there is no internal decision-making process which guides this choice. (This is different than "we can't see the internal process precisely enough" or "we don't yet know what the internal process is". No, experiments seem to tell us that there is no internal process.)

 

[Elf Grinder 3000]

Yes, nothing causes it to "choose" one or the other. As far as we can tell, this choice is perfectly, fundamentally random. As Sol points out, Bell's Theorem (discovered in the 1960s, heavily studied since then---including by people who fully expected to disprove it---and so far still standing) tells us, subject to the assumptions Sol mentioned, that there is no internal decision-making process which guides this choice. (This is different than "we can't see the internal process precisely enough" or "we don't yet know what the internal process is". No, experiments seem to tell us that there is no internal process.)

If there is no internal process that determines a + or - then does it happens for no reason? That seems very strange.

 

[ben m]

If there is no internal process that determines a + or - then does it happens for no reason? That seems very strange.

I agree, quantum mechanics is very strange. But that's what the Universe has handed to us.

ETA: Let me be a little more careful before saying "no reason". There are physical laws that set up (+) and (-) (in this example) as the complete list of possibilities---there's a reason that we're talking about (+) vs (-), not (+) vs (-) vs (#$*&). There are physical laws that determine the probability of (-) per unit time, and also the probability of (+) per unit time. But as to which probability comes up lucky---no, there's no set of internal lotto balls which make the decision. It happens "for no reason".

 

[Tumbleweed]

I agree, quantum mechanics is very strange. But that's what the Universe has handed to us.

ETA: Let me be a little more careful before saying "no reason". There are physical laws that set up (+) and (-) (in this example) as the complete list of possibilities---there's a reason that we're talking about (+) vs (-), not (+) vs (-) vs (#$*&). There are physical laws that determine the probability of (-) per unit time, and also the probability of (+) per unit time. But as to which probability comes up lucky---no, there's no set of internal lotto balls which make the decision. It happens "for no reason".

So is radioactive decay linked to qm in some way since it too apparently happens "for no reason"? It seems atoms are randomly "chosen" to decay.

 

[ben m]

So is radioactive decay linked to qm in some way since it too apparently happens "for no reason"? It seems atoms are randomly "chosen" to decay.

Yes, radioactive decay is entirely quantum mechanical.

 

[martu]

Let's stick with spin, if that's OK, since it's less complicated. Suppose I prepare a particle which is a quantum superposition of a spin-up eigenfunction and a spin-down eigenfunction. (This is very easy to do in practice.) When I try to measure the spin direction, the particle has to "choose" one and only one eigenfunction. Yes, I've forced it to make a choice, but which option it chooses is random. (Roughly speaking, Copenhagen interpretation, etc., YMMV, etc.)

Why do you use the word choose? I know you've put it in quotes so I don't think it is a conscious choice but aren't we just saying that this object can be either 'up' or 'down' and we don't know which one it is until we measure it? This is no different to putting a spider in an empty dark room with one half of the floor red and the other blue (with magical walls it can't get up...) and letting it wander about. Until we turn on the light we don't know where the spider is but we know it is either on red or blue. By turning on the light we don't make the spider 'choose', the choice depends on the time we measure it which is the time we turn on the light.

I guess this goes to the heart of the Copenhagen interpretation and that famous cat.

The position-vs-momentum uncertainty is of the same nature---it so happens that when you try to measure a position, you force the particle into a position eigenstate; but that position eigenstate is a superposition of many, many different momentum states. This goes into the part of the problem I labeled "Suppose I prepare a particle ..." in the spin example; if you "prepare" a particle in a position eigenstate, you're also (like it or not) preparing a superposition of many momentum eigenstates. And vice-versa.

Thanks that's clear.

 

[martu]

No, it doesn't say that.

It says either the world is non-deterministic, or it's deterministic but one or both of those two assumptions isn't valid. In the deterministic case since we have strong evidence for (2), my bet is on (1).

If you agree, you have to accept one of two things:

(a) The world is non-deterministic. Many people find that hard to accept.
(b) The world is non-unique. Many people find that hard to accept.

Right that's clear thank you.

Surely if spin does not have classical analogue that means that QM is fundamentally non-deterministic? Or is it not as simple as that?

 

[martu]

Yes, nothing causes it to "choose" one or the other. As far as we can tell, this choice is perfectly, fundamentally random. As Sol points out, Bell's Theorem (discovered in the 1960s, heavily studied since then---including by people who fully expected to disprove it---and so far still standing) tells us, subject to the assumptions Sol mentioned, that there is no internal decision-making process which guides this choice. (This is different than "we can't see the internal process precisely enough" or "we don't yet know what the internal process is". No, experiments seem to tell us that there is no internal process.)

What experiment(s) are the best evidence for Bell's Theorem?

 

[sol invictus]

If you do not try to mix both epistemic and ontic descriptions into determinism it works just fine with QM at least that is what I get from this paper . . . perhaps I have misread somewhere . . . http://philsci-archive.pitt.edu/archive/00000948/00/HiddenDeterminismus.pdf

Anything that uses the word "ontic" is hard to take seriously. But go on...

Its funny to me that I posted a paper by Hans Primas pages back that deals with this very notion and it is ignored in favor of detailed conversations regarding the nature of physics in specific circumstances and how that relates to a vague definition of determinism, when Primas suggests this kind of conversation is due to a categorical mistake. I was really looking forward to some professional physicists commenting on that paper.

There's nothing remotely ambiguous or vague about the definition of determinism I presented.

I find this topic fascinating, but cant seem to understand how a concept like determinism can be understood at all in terms of predictions based on statistics. So I hesitate to use or acknowledge such a term that adds no new understanding and only elicits such confusion.

The problem I suspect you're having, and the problem many philosophers have, is that they become confused about the distinction between models and reality.

Models are mathematical objects about which one can prove things. Reality is another matter, at best one can collect evidence that supports one model and falsifies another, but one can never be certain the model is correct. Once you accept that, most of these philosophical debates are deflated.

Which makes me wonder how many of the specific examples used in this thread to support the notion of non-deterministic universe are ontically deterministic, its only what we can know that is random??

We can know that the model is deterministic or not. We'll never know for certain whether the universe is.

Surely if spin does not have classical analogue that means that QM is fundamentally non-deterministic? Or is it not as simple as that?

Why spin? Just because QM has new features, why does that mean it's non-deterministic?

What experiment(s) are the best evidence for Bell's Theorem?

Bell's theorem is a mathematical theorem that applies to a class of models, so it doesn't require evidence. The relevant evidence are experiments that show Bell's inequality is violated, which means that the certain class of theories to which his theorem applies (deterministic, local, and "real") are not good descriptions of the world.

Alain Aspect did many such experiments, you can google him.

 

[ben m]

Why do you use the word choose? I know you've put it in quotes so I don't think it is a conscious choice but aren't we just saying that this object can be either 'up' or 'down' and we don't know which one it is until we measure it? This is no different to putting a spider in an empty dark room with one half of the floor red and the other blue (with magical walls it can't get up...) and letting it wander about. Until we turn on the light we don't know where the spider is but we know it is either on red or blue. By turning on the light we don't make the spider 'choose', the choice depends on the time we measure it which is the time we turn on the light.

Hi martu, the Many-Worlds interpretation ends up working a bit like your spider, but the Copenhagen interpretation does not. When a state is said to said to be "in superposition", we really do mean superposition---both states are really there, and it's easy to provide evidence of this. (The double-slit experiment is an easy example. The electron goes through both slits, (as evidenced by an interference pattern) and is perfectly happy going through both slits unless you insist on asking it "which slit are you in?", in which case it "chooses" one or the other, probabalistically. The word "choose" isn't quite right, so I put it in quotes---a more common term is "collapses"---but for anthropomorphism purposes it does look a bit like a choice.

 

[martu]

Why spin? Just because QM has new features, why does that mean it's non-deterministic?

Hmmm you're right, for some reason I was thinking a classical analogue would be required but as we can measure spin that is a nonsense.

Bell's theorem is a mathematical theorem that applies to a class of models, so it doesn't require evidence. The relevant evidence are experiments that show Bell's inequality is violated, which means that the certain class of theories to which his theorem applies (deterministic, local, and "real") are not good descriptions of the world.

Alain Aspect did many such experiments, you can google him.

I will, thank you.

 

[martu]

Hi martu, the Many-Worlds interpretation ends up working a bit like your spider, but the Copenhagen interpretation does not. When a state is said to said to be "in superposition", we really do mean superposition---both states are really there, and it's easy to provide evidence of this. (The double-slit experiment is an easy example. The electron goes through both slits, (as evidenced by an interference pattern) and is perfectly happy going through both slits unless you insist on asking it "which slit are you in?", in which case it "chooses" one or the other, probabalistically. The word "choose" isn't quite right, so I put it in quotes---a more common term is "collapses"---but for anthropomorphism purposes it does look a bit like a choice.

Understood, thanks for the explanation.