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Why Quantum Mechanics?

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Re: Why Quantum Mechanics?

#81

Post by MattPalmer1086 »

trixie_ wrote: post #45
MattPalmer1086 wrote: post #41

Earlier quoted context omitted.

Physicists don't largely choose physical theories on whether they make life meaningful or not. I think you're thinking of religious people.

I'm not. Otherwise why would physicists support the concept of free will so strongly without any evidence for it. It is borderline religious. The video I posted above says as much.

IANAP, but the actual definition of Bell's free will argument is a bit more nuanced, and was probably an unfortunate term to use to describe it.

The reason that super determinism is rejected is because (in the usual understanding) that it requires that the initial state of the universe is set up incredibly precisely to make all subsequent measurements appear to violate Bell's inequality, even though reality isn't actually like that.

So if we set up a quantum measurement and make a decision based on photons of light emitted from distant stars, the experimenter deterministically chooses to make just the right measurement that would make the universe look like it was violating the inequality. Including all the matter between us, and the atoms in the neurons in the experimenters brain, and the photons that were emitted before any of that existed.

This is why super determinism is rejected. It would mean that we are not "free" to choose the experiments and measurements we perform. The universe would be essentially conspiring to deceive us at all levels, including what science we do, the results we receive and the conclusions drawn from it. Which is why it would invalidate the scientific method itself. We couldn't trust anything we thought we knew.

Sabine has a different take from what I can tell. If you allow backwards causality, the measurement act is not independent of the thing being measured. See this blog entry and the comments:

http://backreaction.blogspot.com/2019/07/the-forgotten-solut...

Re: Why Quantum Mechanics?

#82

Post by dskloet »

MichaelRazum wrote: post #80

Im just taking the easy course of QM by Suesskind. He had an example like you have two coins and give them randomy to your kids. The they move far away. Then one kid discovers what it got, it knows what the other has. So what I dont get is why QM you could argue that there is some hidden shared state. Guess this is a typical question. But anyway I‘m somehow not convinced that it is really random.

You'll be convinced once you understand the EPR paradox and Bell's inequality. So look those up if you want to be convinced.

Re: Why Quantum Mechanics?

#84

Post by [deleted] »

EMM_386 wrote: post #24
trixie_ wrote: post #11

Randomly found a link to this video on super determinism from his blog and found it super interesting. 100% agree, what is 'free will' anyways? A concept with no scientific definition. Why is it even used to explain anything in quantum mechanics? https://www.youtube.com/watch?v=ytyjgIyegDI

I strongly feel that the mystery of consciousness is somehow deeply tied into why we have things like QM and not classical physics. If it was just classical physics, then you get yourself into the thinking that you can rewind time and all the "billiard balls" knock into each other the same way, which is why you order a soup and not a sandwich every single time on that day. That eliminate free will. There is something…

[deleted]

Re: Why Quantum Mechanics?

#85

Post by feanaro »

guerrilla wrote: post #72
feanaro wrote: post #65

Earlier quoted context omitted.

The fact that your process knows about and is able to comprehend and reason about its own workings gives it the opportunity to change itself based on this knowledge. To hear about it and to then decide "this absolves me of any guilt, because I couldn't have done it any differently" is also a choice your process made. Counterfactually, it could've made the opposite choice (though it didn't do so). Now, me pointing thi…

Why do we absolve some people of guilt for being a product of their genes and environment and not others? Where do you draw the line? It would seem that "they couldn't help it" just as much as the people that you describe.

The line is subjective and arbitrary.

> just as much as the people that you describe.

I'm not sure which people you mean. I'm saying that it is both true that you "cannot help it" in one sense and false in another sense.

There is always a causal level in which you could not have helped it. But it is never correct to conclude that there is nothing you could've done to help it, because this is also a choice and making it prevents higher-order changes.

Re: Why Quantum Mechanics?

#86

Post by bawolff »

deltaonefour wrote: post #44
bawolff wrote: post #10

Earlier quoted context omitted.

We may not find the answer, but it seems really different than say predicate logic. It seems easy to imagine a non-quantum world. I can't imagine a world where predicate logic doesn't work.

The universe seems to be built in layers. Science, Math, and logic in that order with logic at the very bottom. So logic is always PART of the answer as it's just a layer on the bottom of everything. The thing is, I would imagine the answer to the question "why?" is on some hidden layer below logic. But the buck stops there. Even the very thought of predicting that there's a hidden layer has to involve logic. To get…

Not entirely what my view is. Although arguably much depends on the meaning of the word "why"

My original point was: say logic is false. That's hard to concieve of, and if so we basically can't reason. The rules of logic are independent of the physical world in a way the physical world following QM is not. I wouldn't say it is gradual layers but a hard line between physical and non-physical theories.

As to your point - i disagree although i think we have different conceptions of "why". We'll never answer it in the sense of some creator saying "because i thought it'd be funny", but we can motivate the choice. We can make arguments that it is the most "natural" or "simple" system that meets requirements. Or most "elegant". Arguably that would probably all be post-hoc justification, but its still an interesting exercise.

Re: Why Quantum Mechanics?

#87

Post by simonh »

seiferteric wrote: post #15
trixie_ wrote: post #11

Randomly found a link to this video on super determinism from his blog and found it super interesting. 100% agree, what is 'free will' anyways? A concept with no scientific definition. Why is it even used to explain anything in quantum mechanics? https://www.youtube.com/watch?v=ytyjgIyegDI

I think the question of free will is even simpler. It doesn't come down to determinism vs indeterminism because either way it's not "you" making a decision. At the lowest level (neuron or whatever) when a decision is "made" it is either deterministic (determinism) or probabilistic (indeterminism) based on physics but either way, where is the "you" in the process? Only way free will makes sense is if something superna…

I see the relationship of determinism to free will completely differently. Without determinism there is no agency. If my state - my memories, preferences, experiences, skills, personality and emotions do not determine my actions, how can those actions be truly mine?

I know many people are very uncomfortable with this, but I don't really know what they actually want. I think appealing to QM to wave an indeterminism wand and 'somehow' resolve the problem is wishful thinking. Randomness, as pointed out by others here, is no answer and if all QM contributes is randomness then it's no real help. I'm perfectly willing to accept that there's a certain degree of randomness in our choices, that's fine, but it's not the answer to the question of free will.

I also don't see how appeals to some non-material source of decisions helps either, surely such a source must also have a state? It's simply punts the question, and I see no reason to suppose it actually helps answer it. Aside from the fact that if a 'non-material' source of choices interacts with real matter, surely that makes it real, right? It's just nonsense on stilts.

IMHO we are real, material beings. Our state determines our actions, with some randomness sprinkled in, and I'm fine with that. Yes this has some uncomfortable philosophical implications, but that's ok. In fact I think it's a good thing. If we're all driven by our state, and that's determined by factors outside our control, it humanises us. We're flawed beings living in a dangerous universe. We need to stick together and learn to understand and tolerate our flaws and weaknesses. Coming to this realisation has changed my attitude to a lot of things, and to me that capacity for change is all the free will I need.

Re: Why Quantum Mechanics?

#88

Post by TheOtherHobbes »

robbedpeter wrote: post #30
seiferteric wrote: post #15

Earlier quoted context omitted.

I think the question of free will is even simpler. It doesn't come down to determinism vs indeterminism because either way it's not "you" making a decision. At the lowest level (neuron or whatever) when a decision is "made" it is either deterministic (determinism) or probabilistic (indeterminism) based on physics but either way, where is the "you" in the process? Only way free will makes sense is if something superna…

It's not that easy, unfortunately. The problem lies in the relationship between a mind - the system of patterns of connections and processes that constitute whatever it is that allows a subjective experience to occur as an emergent property - and the external world. That singleton which has experience, and the infinite outside which it experiences. Free will could be framed as unpredictable behavior arising from the…

Yes exactly - "free will" is shorthand for "There's a mind with subjective experiences involved in all of this, and we have no idea what that means or if it even means anything."

We don't know what minds or qualia are, and until we know for sure - as opposed to hoping and guessing and "well obviously..." - these speculations are just hand-waving.

The problem is that all of physics is filtered through our minds. We literally have no way to experience reality without experiencing it through a human mind.

So although we've managed to persuade ourselves our experiences of science are "objective", all that really means is that other human minds are very likely to have similar experiences if we set up similar circumstances in similar situations.

Potentially our minds could be operating in the conceptual and experiential equivalent of the visible light spectrum, and the range of possible "objective" experiences is very much wider.

Re: Why Quantum Mechanics?

#89

Post by emptyfile »

srcreigh wrote: post #61
adrianN wrote: post #33

Earlier quoted context omitted.

You seem to suggest some kind of hidden variable theory for free will: https://en.wikipedia.org/wiki/Hidden-variable_theory . As far as I know they're not particularly popular among physicists, although we haven't (completely) ruled out such an explanation.

Newton and Einstein both seem to be on the side of hidden variables, so I'm not sure if it's unpopular among the elites. I have a lot of trouble imagining any experiment which could completely rule out every other influencing factor. There are silly thought experiments such as what if the world has been objective for the last x00 years - prior to that and after, the laws we've observed during the period would bend; t…

> Newton and Einstein both seem to be on the side of hidden variables, so I'm not sure if it's unpopular among the elites.

Everyday posters on this website amaze me. I should really stop coming here...

Re: Why Quantum Mechanics?

#90

Post by Schroedingers2c »

MichaelRazum wrote: post #80

Im just taking the easy course of QM by Suesskind. He had an example like you have two coins and give them randomy to your kids. The they move far away. Then one kid discovers what it got, it knows what the other has. So what I dont get is why QM you could argue that there is some hidden shared state. Guess this is a typical question. But anyway I‘m somehow not convinced that it is really random.

You can think of scenarios in which any classical state (i.e. the shared state is completely specified by the local states of the two kids) does the task with some success probability that is upper bounded, say by 75%. And you can even include some unspecified hidden variable in your classical state and could even allow the two kids to share some classical randomness (think: each of them has a button that returns the same random number for both kids). This hidden variable could be anything (a single unknown property, a whole collection of unknown properties or whatever really) and represents possibly incomplete knowledge, for example due to imperfect microscopes or equipment. Since you don't specify what this hidden variable is, it encapsulates anything that is allowed by classical physics (remember we started out with a classical state).

Now lets allow entangled states between the kids (states that can only be specified if you have both subsystems, locally if you measured such a state your result will look at least a bit random or even completely random). Then you can prove that the two kids can do the task (that has classical success probability 75%) with success probability ~85% all of a sudden.

You can write down general inequalities that describe such behaviour and that's what Bell inequalities are. The fact that entangled states in quantum mechanics violate the classical bound (which you cannot break if you demand your two kids can only share states allowed by classical physics, even if you allow unspecified hidden variables), proves that nature is not classical. It doesn't prove that nature is quantum, it just proves that nature is not classical. Bell inequalities have also been unambiguously experimentally verified [1].

In conclusion, nature allows for two-party (or multi-party) states that cannot be described by just describing the local parts of it. There is no information in the local parts, but if you look at both parts together then there is information. Think "the whole is more than the sum of its parts". Classically, the whole is the sum of its parts. Classically, you read a book page by page. If your pages are entangled with each other, you could only read your book by looking at all pages together, because if you looked a single pages separately anything written there would look like random garbage to you.

The question that remains is: Where is the information then, physically? In some sense you could say it does not exist before measurement, because only when you look at the correlations between the local measurement results of the two kids will you find out that the underlying state must have been entangled (which you get to know if the state violates a Bell inequality). But that is just one possible interpretation, there still is a lot of scientific debate about what quantum mechanics really means.

These are exactly the scenarios that make quantum so weird but fascinating at the same time.

[1] https://www.nature.com/articles/nature15759

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