Can a computer be an observer?

[cesiumfrog]

Yes. in BM 'universe wavefunction' is exactly the same as in MWI. (In fact, wavefunction is the same in ANY non-collapse int. one can imagine). However, BM declares that only one (what we call in MWI 'branch') forms 'reality'. [...] empty waves are 'half real'

Thanks, that's a really forthright description. Would all proponents of BM find that uncontroversial?

MWI is BM(0) [...] BM(2) has 4 flavors of reality,

Could you point me to a reference on this?

 

[Dmitry67]

Could you point me to a reference on this?

It is just my argument against BM I used in coversation with Demystifier.

Imagine the generalization of BM with N sorts of particles. Say, N=2 and there are RED and BLUE particles. So we have:

1. Empty waves
2. Waves with BLUE particles only
3. Waves with RED particles only
4. Waves with both types of particles inside

What of above is real? The answer was obvious in BM(1), bot not in BM(2)

Finally, one can imagine an inverse BM(1) : only EMPTY waves are real. The question is, how can you tell the difference between BM(1) and iBM(1) ? My point is that BM uses physical axiom, which can't be reduced to formalas and can't be expressed mathematically. That axiom is 'only waves with particles are 'REAL''.

 

[Demystifier]

Demistifier, I am just curious, how would you answer the question:
Are empty waves real?

According to BI - yes, they are real.
But why then don't we see them? Because "we" are (made of) particles, so we are not there to see the empty waves.

Satisfied?

 

[Demystifier]

It is just my argument against BM I used in coversation with Demystifier.

Imagine the generalization of BM with N sorts of particles. Say, N=2 and there are RED and BLUE particles. So we have:

1. Empty waves
2. Waves with BLUE particles only
3. Waves with RED particles only
4. Waves with both types of particles inside

What of above is real? The answer was obvious in BM(1), bot not in BM(2)

Finally, one can imagine an inverse BM(1) : only EMPTY waves are real. The question is, how can you tell the difference between BM(1) and iBM(1) ? My point is that BM uses physical axiom, which can't be reduced to formalas and can't be expressed mathematically. That axiom is 'only waves with particles are 'REAL''.

In BI, there is no axiom that "only waves with particles are 'REAL'". Instead, BI explains why it APPEARS that empty waves are not real, even though they are real. In your variant 4., both blue and red particles would be real, but they would not mutually interact, so observers made of red particles would think that blue particles are not real and vice versa.

 

[Dmitry67]

According to BI - yes, they are real.
But why then don't we see them? Because "we" are (made of) particles, so we are not there to see the empty waves.

Satisfied?

partly :)
So if fact you admit that when I open a box and see a dead cat, then alive cat is real as well but just not detectable Note that it is different from a canonic way to explain BM :)

You say: Assuming that I am tagged (have particels inside) I can interact (observe) only tagged branches. So yes, according to BM, for tagged observer only tagged reality is real.

However, why observers are tagged in the first place? non-tagged observer can observe non-tagged reality as well as tagged observers can observe tagged reality.

 

[Dmitry67]

In BI, there is no axiom that "only waves with particles are 'REAL'". Instead, BI explains why it APPEARS that empty waves are not real, even though they are real. In your variant 4., both blue and red particles would be real, but they would not mutually interact, so observers made of red particles would think that blue particles are not real and vice versa.

Yes, we are on the same page.
Then 2 another questions.

1. I (tagged observer) open a box and see a cat which is alive. I know that there is a dead cat in another branch. Assuming that poison works slowly, does that another cat experience pain?

2. How do I know that I am tagged?

 

[Demystifier]

So if fact you admit that when I open a box and see a dead cat, then alive cat is real as well but just not detectable

That's wrong. The cat is also made of particles, so alive cat is not real.

You say: Assuming that I am tagged (have particels inside) I can interact (observe) only tagged branches. So yes, according to BM, for tagged observer only tagged reality is real.

That's not what I say. I am not merely tagged, but I am the tag itself.

However, why observers are tagged in the first place? non-tagged observer can observe non-tagged reality as well as tagged observers can observe tagged reality.

Observers are not tagged. Observers are the tags themselves.

 

[Demystifier]

1. I (tagged observer) open a box and see a cat which is alive. I know that there is a dead cat in another branch. Assuming that poison works slowly, does that another cat experience pain?

You are not the tagged observer. You are observer the tag. There is no cat the tag in another branch.

2. How do I know that I am tagged?

You are not tagged. You are the tag.

See also this analogy
https://www.physicsforums.com/blog.php?b=6
The recipe for preparing food is not the food.

 

[Dmitry67]

Now we are not on the same page.
By the word 'tagged' I meant simple 'contains particles' or 'not made of empty waves'
So some places of global universe wavefunction are tagged, but most of it are not.
Do we agree on it?

 

[Demystifier]

Now we are not on the same page.
By the word 'tagged' I meant simple 'contains particles' or 'not made of empty waves'
So some places of global universe wavefunction are tagged, but most of it are not.
Do we agree on it?

With that, I agree. The wave function can be tagged. But, according to BI, the observer cannot be tagged because he is not the wave function but the tag itself.

 

[Dmitry67]

Ok, I don't know what you mean but the 'tag' in that case.
Anyway

That's wrong. The cat is also made of particles, so alive cat is not real.

Is it correct to use what you explained before and translate "alive cat is not real" into more accurate "alive cat is REAL, but just APPEARS not real?"

 

[cesiumfrog]

In BI, there is no axiom that "only waves with particles are 'REAL'". Instead, BI explains why it APPEARS that empty waves are not real, even though they are real. In your variant 4., both blue and red particles would be real, but they would not mutually interact, so observers made of red particles would think that blue particles are not real and vice versa.

You are not tagged. You are the tag.

In standard BI (so there is only one "colour" of particle surfing the universe's wave-function), how many particles (of that colour) are there?

Is it just one? I think this seems sufficient for a wave-function in configuration space, consistent with basic many-body QM. It would mean the tag is not just you, but it is all of us.

Or is it many (one for each physical particle)? As in "you are made of tags". This seems more consistent with the motivation behind BI, with the tag particles living in ordinary space-time, but I don't get how exactly the universe's wave function would pilot the coordination between these particles.

 

[alxm]

Well, there's http://en.wikipedia.org/wiki/Henry_Stapp" , who believes that consciousness is a series of measurements that the brain performs on its own superposed physical states (if I understand him correctly).

Never heard of him, and the article there seems to imply he's only really known for his quantum-consciousness stuff.

Are we certain that this question is closed?

It's closed to the same extent that the 'question' of whether molecules are held together by gravity is 'closed':
There is no evidence this is the case, there's no reason to believe this is the case, there is no big void in our current understanding
that requires such a radical new theory to explain it, and the existing theory says that the two phenomena are orders of magnitude apart.

Or is it that some physicists just want to make it go away, because it's so messy?

I work with quantum-chemical studies of biochemical systems. (i.e. 'quantum biochemistry'). There's nothing stopping you from studying this,
except for the fact that there's no plausible theory worth studying, nor any big unexplained experimental phenomenon which requires such a theory.

 

[Demystifier]

Is it just one? I think this seems sufficient for a wave-function in configuration space, consistent with basic many-body QM. It would mean the tag is not just you, but it is all of us.

That's true. If by a particle you mean a particle in the configuration space, then the tag (the particle) is not just me but all of us.

 

[Galap]

Anything that makes a measurement is an observer.

 

[cesiumfrog]

That's true. [..in BM..] the tag (the particle) is not just me but all of us.

Thanks. Would you mind explaining how proponents of BM (like yourself) deal with some possible criticisms?

1) Since you've said that the entire wave-function of the universe is real, we can at least consider parts of it which the tag never encounters. We could identify what those parts would represent if they were encountered by the tag: for example, we can identify the potential states of people that those parts represent (e.g., the actions they would be carrying out, stimuli they would be responding to, external discussion and internal thoughts and emotions they would be experiencing, memories they would possess, their preceptions of the progression of time, etc). In particular, how would you be able to detect that society corresponds with the part the universal wave-function that is tagged, and not just some other part?
2) It seems terribly abstract, that everything in the determinate universe is really just one single elementary tag-particle. What justification is there to adopt such an extremely abstract view AND simultaneously dismiss MWI?

Perhaps to express differently... Imagine if we were to discover that gravity, or some other force, allows interaction (without decoherence) between superpositions so that we can build a telephone and speak to people from parallel worlds. How exactly would BMics answer if those people told us that they are the part of the universe's wavefunction where the tag is located?

 

[Fra]

Lee Smolin writes, "The question that comes up in these interpretations revolves around what actually causes the collapse of the quantum wavefunction...The principle of decoherence is, to many, the explanation -- interaction with the environment causes the quantum collapse. Even more significantly, physicists are able to solve the equations, perform experiments, and practice physics without resolving the questions of what exactly is happening at a fundamental level, and so most physicists don't want to get near these bizarre questions with a 20 foot pole."

Forgive me, but I just don't see this kind of fundamental unease happening in discussions about perpetual motion.

What I would like to understand is, how serious are these ongoing foundational questions within the legitimate physics community? Is it really just the crackpots and charlatans who bring them up, or does Smolin have a point?

I think there are some serious issues here, but there are two parallell threads:

Even for those that wants to see a new mathematical framework for physics, and a new way to pose questions in order to solve the set of open problems in physics, and that this may require quite radical reconstructions, it's clear thta business as usuall must continue, and after all all the technology and current "mainstream" research are after all making some steady but slow progress by walking the mainstream path.

So I think it's makes perfect sense that a lot of people, do stick do the theories and frameworks that are the de facto best theories we have, and work from there.

But in parallell to that, I think it's also needed that a group of people try to work of more radical and thus relative to the first way "speculative" paths, in order to question the framework and methodology of the current state of physics.

So the two threads aren't really contradicting from the science perspecive, it's quite sound to keep the two focuses. But the fact that it's sound to keep a good focus on the de facto standard formalisms and theories, should not be confused with thining that it means that some of the more radical views are wrong or crackpottery. The progression of science needs variety.

The decoherence view, mentions the environment, which is easy to imagine when you picture an localized apparatous in a laboratory room. The apparatous is the "observer" and the laboratory environment is the environment. But then let's not forget that then we are introducing a new observer, a birds view, which can encode a larger state space, the apparatous, what's beeing measured, AND the entire state of the laboratory! That MIGHT still make pretty good sense for human laboratories, from the point of us beeing outside the lab.

But, this scheme totally fails it you picture cosmological model, where the observer observes not a small subsystem, but it's own entire environment. In this case, there is clearly no "exernal environment", beucase the observer somehow "IS" the environment, captures INSIDE an open subsystem.

This is another problem that Smolin also has raised. It's not a problem specific to QM, it's rather a problem common to the abstraction framework commong to classical mechanics, SR, GR and QM. Where you picture a timless configuration space and then eternal laws of evolution.

See http://pirsa.org/08100049/ for philoosophical arguments on this. This is one of the quite radical and borderline crazy ideas, but IMHO Smolin happens to be perfectly right here ;)

/Fredrik

 

[Demystifier]

Thanks. Would you mind explaining how proponents of BM (like yourself) deal with some possible criticisms?

1) Since you've said that the entire wave-function of the universe is real, we can at least consider parts of it which the tag never encounters. We could identify what those parts would represent if they were encountered by the tag: for example, we can identify the potential states of people that those parts represent (e.g., the actions they would be carrying out, stimuli they would be responding to, external discussion and internal thoughts and emotions they would be experiencing, memories they would possess, their preceptions of the progression of time, etc). In particular, how would you be able to detect that society corresponds with the part the universal wave-function that is tagged, and not just some other part?
2) It seems terribly abstract, that everything in the determinate universe is really just one single elementary tag-particle. What justification is there to adopt such an extremely abstract view AND simultaneously dismiss MWI?

The best way to answer this is through an analogy:
https://www.physicsforums.com/blog.php?b=6

Perhaps to express differently... Imagine if we were to discover that gravity, or some other force, allows interaction (without decoherence) between superpositions so that we can build a telephone and speak to people from parallel worlds. How exactly would BMics answer if those people told us that they are the part of the universe's wavefunction where the tag is located?

In that case, the concept of parallel worlds would not make sense, for the "worlds" would no longer be "parallel". Yet, the Bohmian interpretation would still make sense. In fact, I have argued elsewhere
http://xxx.lanl.gov/abs/quant-ph/0505143 [Found.Phys.Lett. 19 (2006) 553]
http://xxx.lanl.gov/abs/0707.2319 [AIPConf.Proc.962:162-167,2007]
that in that case the Bohmian interpretation is the only interpretation of QM that would make sense. Other interpretations are meaningfull when QM is linear, but your case corresponds to nonlinear QM.

 

[Dmitry67]

Demistifier,
could you agree or disagree on the subject we discussed on the previous page?

in BM
1 wavefunction is real
2 so all 'parralel' worlds and another oucomes are real as well,
3 but they are not detectable for tagged observer.

Please look at it *from vird's view*, not by the eyes of the observer. "You are the tag" is meaningless in the birds view.

 

[Demystifier]

Demistifier,
could you agree or disagree on the subject we discussed on the previous page?

in BM
1 wavefunction is real
2 so all 'parralel' worlds and another oucomes are real as well,
3 but they are not detectable for tagged observer.

Please look at it *from vird's view*, not by the eyes of the observer. "You are the tag" is meaningless in the birds view.

I almost agree. More precisely, I would agree if you would slightly reformulate it as follows:
in BM
1 wavefunction is real
2 so all 'parallel' worlds are real as well,
3 but they are not detectable for the observer made up of tags.

Compare it also with the tree-and-ant analogy:
in biology
1 the tree is real
2 so all "parallel" branches are real as well,
3 but they are not detectable for the observer made up of animal cells - the ant.

If you still don't get it, there is another way to explain it: MWI is a theory describing how the tree looks to the tree. BI is a theory describing how the tree and the ant look to the ant.

 

[Dmitry67]

Cool! So we agreed! I 100% agree with your formulation.

But now let me ask the most important question:
as based on (2) parallel worlds are real as well,

are observers there (in these parallel worlds) conscious?
do they feel pain?

 

[Demystifier]

Cool! So we agreed! I 100% agree with your formulation.

But now let me ask the most important question:
as based on (2) parallel worlds are real as well,

are observers there (in these parallel worlds) conscious?
do they feel pain?

Since I have no idea how consciousness arises, I will answer you through an analogous question:
Are tree branches without ants conscious?
Do they feel pain?

By the way, IMHO the problem of consciousness is the most difficult problem in science. Compared to it, the problem of interpretation of QM is trivial.

 

[Dmitry67]

Yes, this problem of consciousness is very difficult. Note that my question led you to a trap.

If you answer: Yes, they are conscious, then I say: then what is a difference between BM and MWI? All other beings in the alternative branches feel, think, they are conscious… Their world is exactly the same as ours. Then there is absolutely no advantage in BM, as all branches are equal.

If you answer: No, they are not conscious, then I say: so you claim that consciousness is actually *created* by the BM particles, because the same human – receiving signals, replying something, with fully functional brain (wavefunction of fully functional brain) is not conscious just because waves are empty! And as particles are undetectable in principle and do not affect the wavefunction, then it looks as pure magic.

By answering ‘I don’t know’ you don’t avoid the problem – we just don’t know what problem to address.

 

[Demystifier]

Yes, this problem of consciousness is very difficult. Note that my question led you to a trap.

If you answer: Yes, they are conscious, then I say: then what is a difference between BM and MWI? All other beings in the alternative branches feel, think, they are conscious… Their world is exactly the same as ours. Then there is absolutely no advantage in BM, as all branches are equal.

If you answer: No, they are not conscious, then I say: so you claim that consciousness is actually *created* by the BM particles, because the same human – receiving signals, replying something, with fully functional brain (wavefunction of fully functional brain) is not conscious just because waves are empty! And as particles are undetectable in principle and do not affect the wavefunction, then it looks as pure magic.

By answering ‘I don’t know’ you don’t avoid the problem – we just don’t know what problem to address.

All that I can also say to you for the tree and the ant. So your trap caught you as well.

But more seriously, you made two mistakes above.

First, if I answer Yes, they are conscious, it is not true that there is absolutely no advantage in BM. As I stressed many times (and you ignored the same number of times), the advantage of BM is that it can explain the Born rule.

Second, if I answer No, they are not conscious, it is not true that particles are undetectable in principle. Roughly, this is like saying that consciousness is not detectable in principle. Just the opposite, if anything is detectable, then it is consciousness. Yet, nothing is more difficult to detect by scientific means than consciousness. This is indeed a paradox of consciousness which I don't know how to solve. But whatever the solution is (maybe you know?), the problem with detection of Bohmian particles is of a similar kind.

But since consciousness is so problematic, vague and paradoxical concept, it is better not to use consciousness in physics discussions. If arguments based on consciousness are your only arguments for or against some physical hypothesis, then you arguments are very shaky.

 

[Dmitry67]

Ok, let's begin from the flavor of BM where observers in ‘empty’ branches are conscious (conscious-BM, or c-BM. Another flavor is nc-BM :) )

But more seriously, you made two mistakes above.
First, if I answer Yes, they are conscious, it is not true that there is absolutely no advantage in BM. As I stressed many times (and you ignored the same number of times), the advantage of BM is that it can explain the Born rule.

Yes and no.
Yes, BM explains the Born rule in branching events, but only in the branching events between one ‘real’ branch and others ‘empty’ branches. If the original (source) branch is already empty, then the whole sub-tree is empty and is equivalent to MWI.
Also, as observers in empty branches are conscious in c-BM, then the question I asked before is applicable: how do you know that YOU are ‘real’ observer, not an ‘empty’ one? In either case you are conscious. What if the real branch had gone away 5 billion years ago, when Earth had formed in a different place, and our whole history – is an ‘empty’ sub-tree from the very beginning?

 

[Demystifier]

Also, as observers in empty branches are conscious in c-BM, then the question I asked before is applicable: how do you know that YOU are "real" observer, not an "empty" one?

There is an experimental way to answer this question.
I repeat the same kind of measurement many times. If the statistics of my measurement outcomes obeys the Born rule, then I am the "real" observer. If the statistics obeys the rule that each branch (originating from the same parrent branch) is equally probable, then I am (mostly) the "empty" one. If the statistics obeys some intermediate rule, then I am sometimes "real" observer and sometimes the "empty" one.

Needless to say, such measurements have been performed many times. We all know the results.

 

[Dmitry67]

So if you repeat the same experiment many times, you create billions sub-branches every time. In c-BM, in all these branches YOU are conscious too. So in minutes you end with 100000000000000000 you’s, and only one is non-empty. So why your consciousness systematically falls into the non-empty branch? If you pick randomly any consciousness from universe wavefunction, you have almost no chance to pick up ‘real’ branch!

Isnt it an argument against c-BM?

 

[lugita15]

I don't know of a single big-name physicist (or perhaps even reputable physicist) today who believes in quantum-consciousness ideas. (Roger Penrose is a gifted mathematician, but he is not a physicist)

Based on reading Emperor's New Mind, I think Penrose believes in objective collapse. He thinks that gravity collapses the wave function, but he doesn't think that the state the wave collapses into is random or probabilistic. He believes that there is a deeper, fully deterministic theory underlying quantum theory. He thinks that collapse consists of an object "acquiring information" from some Platonic mathematical heaven. (Yes, it sounds absurd at first glance, but he defends it at length.)

 

[Count Iblis]

Uhm, Penrose certrainly is a physicist (by definition, a physicist is someone who does research in one or more physics topics), one of the most brilliant theoretical physicists. That doesn't mean he is right on this issue, of course.

If you look back at how new theories of physics were developped, what choices one has had to made when formulating the theories, what the motivations for the choices were, you see the following pattern:

Making the most reasonable choice in resolving very academic, often ridiculous sounding thought experiments is far more important than trying to make ad hoc fixes to existing theories (that already work extremely well in practice). The latter approach is often preferred by experimentalists and people who use the theory in practice (the "phenomenologists"). This leads to an inertia against progress.

 

[cesiumfrog]

If you look back at how new theories of physics were developped, what choices one has had to made when formulating the theories, what the motivations for the choices were, you see the following pattern: Making the most reasonable choice in resolving very academic, often ridiculous sounding thought experiments is far more important than trying to make ad hoc fixes to existing theories (that already work extremely well in practice). The latter approach is often preferred by experimentalists and people who use the theory in practice (the "phenomenologists"). This leads to an inertia against progress.

Against progress? No. I think progress in physics comes from those experimentalists you deride, or specifically from opening avenues of novel experimental data. Accumulating a wide variety of speculative and untested (let alone testable) theories isn't quite progress. If Einstein's relativity (I assume that's the historical example you have in mind?) hadn't had a Newtonian limit, or if we lacked the technological refinement to verify it, how would we distinguish it from somebody else's total crackpottery?