Against Realism: Examining the Meaning of Local Realism

[Chaos' lil bro Order]

Selfadjoin

I repeat. Do you know of any other realities other than the one we live in? I think the burden of proof lies on those who claim there is an underlying reality beyond our sensory perceptions. In fact that view is unattenable and unfalsifiable and does not sound like good science to me. My view in this matter is not fixed and NO it is not my religion, nor do I have a religion, nor have I ever had a religion. I'm completely open to being convinced that there is an underlying reality beyond our sensory perceptions, but as I say, I think this impossible to prove, even in theory.
Interestingly, even the definitions of 'reality' do not agree with each other. Some seem to say reality is observer-independent (underlying reality), while others say reality is a collection of your experiences. Its no wonder we can't agree then! haha.


Dictionary.com - Reality

'all of your experiences that determine how things appear to you;'

'The totality of all things possessing actuality, existence, or essence'

Philosophy. a. 'something that exists independently of ideas concerning it. '
b. 'something that exists independently of all other things and from which all other things derive.'

 

[Hurkyl]

I think the burden of proof lies on those who claim there is

The burden of proof lies with the person doing the claiming. Since you have asserted there is "one underlying reality", you have a burden to prove your claim.

If selfAdjoint had claimed there were multiple underlying realities, he would also have a burden to prove that claim. As it is, though, he's simply prodding you for making unsubstantiated assertions.

 

[Chaos' lil bro Order]

The burden of proof lies with the person doing the claiming. Since you have asserted there is "one underlying reality", you have a burden to prove your claim.

If selfAdjoint had claimed there were multiple underlying realities, he would also have a burden to prove that claim. As it is, though, he's simply prodding you for making unsubstantiated assertions.

Wrong. I am simply saying that if we agree that our sensory perceptions neccessarily bias our observations of any supposed 'underlying reality'. Then we can never know if there is an 'underlying reality' by definition. For how else can we ever observe this 'underlying reality' without our senses? We cannot. Therefore there is only the reality of sensory perception.

If you still do not understand me (and at this point I don't see how you possibly could not), try imagining this simple example:
Take a tennis ball and hide it under a box. Call your wife in the room and ask her to tell you what is inside the box. You will be amazed to see that she cannot tell you what's inside the box. Do you know why? Because none of her senses can penetrate the box, it is impossible for her to know the contents. Now call your son into the room and ask him the same question and he will also not be able to answer what is inside the box. Now you leave the room and tell your wife and son to discuss what the possible contents of the box are. Given sufficient time, they will come up with every object imaginable that could fit the dimensional constraints of the box, but all of their guesses will be equally wrong and equally correct since they have no way to falsify them. Now imagaine that this box's size is infinite. Your wife and son will exhaust every possible object they can think of and still be no further to a solution as to what the box's contents are.
To finalize my construction, I put forth to the reader that arguing whether there even is an object inside the box is futile and unknowable. But what can be agreed upon is that there is a box that can be sensed by both observers. Therefore the only reality that can be known to your wife and son and anyone else really, is that there is a box, in which there may or may not be an object inside. Barring the notion that your wife and son develop a new sense like X-ray vision, their reality-horizon can only ever be that which they can sensorily perceive, pure and simple.

Maybe you can tell me what is beyond the Universe's observable horizon please? Then you can also tell me what is beyond a human's reality-horizon as well please?

I am open to speculation, but alas, the only truth we can agree upon about reality or anything else for that matter, is what is true at this very moment.

 

[AnssiH]

Well I think the last 6 posts are a good showcase how different our semantical concepts can be. Chaos clearly is using "reality" to simply refer to "everything that exists", whatever that may be. Whereas others may consider reality to mean "things that we can have information about", i.e. things that interact one way or another with the stuff we are made of, directly or indirectly (perhaps there exists other complex structures and systems that just don't interact with what we call matter at all), and yet others may consider physical reality to be one reality and some sort of spiritual reality to be another reality. Some make distiction between "objective reality" and "subjective reality", and some think only the latter one exists.

I think this same sort of confusion is evident it all kinds of arguments about whether it was "reality" that began with "the big bang".

So here it is also visible how our sense of reality is based on certain assumptions about what meaning certain concepts have and what things may exist and in what ways. When you are making statements about just what is "reality", it becomes pretty clear how impossible it is to get the hang of it with semantical concepts. Even if we can make everybody understand these concepts in the same manner, who is to say that is metaphysically "the correct way" to understand reality?

The statement that we are all part of and sharing our experiences in one single objective universe at the same time (and so on), that's a statement of belief that belongs to materialistic paradigm. Hmmm, well a materialist usually considers spacetime to be true also, so that makes it all a bit convoluted, as then we are not in fact experiencing things "at the same time" in any sense at all... :I (And here's the reason I would like to be careful with assertions about the metaphysical existence of spacetime)

 

[RandallB]

The burden of proof lies with the person doing the claiming. Since you have asserted there is "one underlying reality", you have a burden to prove your claim.

I disagree; all logic must come from a beginning foundation and belief.
Logic tells us that there may be many views of reality QM, BM, QED, SED etc. that may all give accurate predictions as an analogy of reality. But no one can claim to be CORRECT as in COMPLETE until it can demonstrate a complete explanation of how the others produced accurate results but within there own more complete detail of the correct one reality. Thus making it clear where, when and why the other views produce the accurate results they give.

What is the foundation of the logic the can bring this conclusion. The same foundation that gives you the most fundamental basis for even asking for a proof.

Before you can ask you must "be".
If you accept the foundational logic that “you think therefore you are”
This provides sufficient fundament logic to build on to come to the conclusion there is only one reality.
If you do not agree that “you think therefore you are” then you need to offer some proof that you exist before you can even ask the question. Preferably a proof that does not lead to the rules of logic we know.

 

[setAI]

I repeat. Do you know of any other realities other than the one we live in?

not only are there other 'realities'- but we now use them to perform computations that would be impossible in just one reality


"there are indeed other, equally real, versions of you in other universes, who chose differently and are now enduring the consequences. Why do I believe this? Mainly because I believe quantum mechanics... Furthermore, the universes affect each other. Though the effects are minute, they are detectable in carefully designed experiments... When a quantum computer solves a problem by dividing it into more sub-problems than there are atoms in the universe, and then solving each sub-problem, it will PROVE to us that those sub-problems were solved somewhere - but not in our universe, for there isn't enough room here. What more do you need to persuade you that other universes exist? " -David Deutsch

 

[AnssiH]

not only are there other 'realities'- but we now use them to perform computations that would be impossible in just one reality


"there are indeed other, equally real, versions of you in other universes, who chose differently and are now enduring the consequences. Why do I believe this? Mainly because I believe quantum mechanics... Furthermore, the universes affect each other. Though the effects are minute, they are detectable in carefully designed experiments... When a quantum computer solves a problem by dividing it into more sub-problems than there are atoms in the universe, and then solving each sub-problem, it will PROVE to us that those sub-problems were solved somewhere - but not in our universe, for there isn't enough room here. What more do you need to persuade you that other universes exist? " -David Deutsch

...like I said, we all use the world "reality" to mean so many different things... :P
And btw, why is MWI becoming into some sort of religion all over the place? There must be something very tempting to a model of reality that implies there's more to reality than we readily perceive... After all, this is what tempts people to believe in any religion :)
Oh boy, next I'm going to hear how MWI "cannot be proven wrong" and how it's "the only possibility".

 

[Hurkyl]

I disagree; all logic must come from a beginning foundation and belief...

I'm confused -- I don't see anything in your post that talks about burdens of proof. In fact, I can't figure out what your point is at all.

 

[kvantti]

...like I said, we all use the world "reality" to mean so many different things... :P
And btw, why is MWI becoming into some sort of religion all over the place? There must be something very tempting to a model of reality that implies there's more to reality than we readily perceive... After all, this is what tempts people to believe in any religion :)
Oh boy, next I'm going to hear how MWI "cannot be proven wrong" and how it's "the only possibility".

Well, here is a challenge for you (and for everyone who doesn't believe in the MWI) from Deutsch (as presented in his book The Fabric of Reality):

Explain where the calculations made by a quantum computer are performed when it solves the sub-problems associated with a single problem. Eg. when factoring a 250-number digit using the algorithm[/url], the number of sub-problems is about 10^500 (the number of particles in the universe is about 10^80).
And yet, a quantum computer solves all the sub-problems at the same time. So how can it solve 10^500 problems during only one calculation, if we have only one computer in only one universe?

(It would take classical computer 10^500 times the time of a quantum computer to perform the same operation)

And for the question why the MWI has become "some sort of religion": it gives a coherent, local and deterministic description of reality and in my point of view, it would be illogical that there would be only one universe. Didn't you think that there are "other dimensions" when you were a kid?

 

[setAI]

A few years ago, BBC Horizon did a documentary on time travel in which you explained the parallel universes theory and suggested that there was ‘hard evidence’ for it. Well, it is a controversial theory and is accepted only by a minority of physicists, as you yourself acknowledge in your book. Why do you think there is such a strong reaction to this theory in the scientific community? And how do you reply to their criticism?

David Deutsch: I must confess that I am at a loss to understand this sociological phenomenon, the phenomenon of the slowness with which the many universes interpretation has been accepted over the years. I am aware of certain processes and events that have contributed to it. For instance Niels Bohr, who was the inventor of the Copenhagen interpretation, had a very profound influence over a generation of physicists and one must remember that physics was a much smaller field in those days. So, the influence of a single person, especially such a powerful personality as Niels Bohr, could make itself felt much more than it would be today. So that is one thing – that Niels Bohr’s influence educated two generations of physicists to make certain philosophical moves of the form "we must not ask such and such a question." Or, "a particle can be a wave and a wave can be a particle," became a sort of mantra and if one questioned it one was accused of not understanding the theory fully. Another thing is that quantum theory happened to arise in the heyday of the logical positivists. Many physicists – perplexed by the prevailing interpretations of quantum physics – realized that they could do their day-to-day job without ever addressing that issue, and then along came a philosophy which said that this day-to-day job was, as a matter of logic, all that there is in physics. This is a very dangerous and stultifying approach to science but many physicists took it and it is a very popular view within physics even to this day. Nobody will laugh at you if, in reply to the question "are there really parallel universes or not?", you answer "that is a meaningless question; all that matters is the shapes of the traces in the bubble chamber, that is all that actually exists." Whereas philosophers have slowly realized that that is absurd, physicists still adopt it as a way out. It is certainly no more than ten percent, or probably fewer, of physicists talking many universes language. But it is heartening that the ones who do tend to be the ones working in fields where that question is significant, which are quantum cosmology and quantum theory of computation. By no means all, even in those fields, but those are the strongholds of the many-worlds interpretation. Those also tend to be the physicists who have thought most about that issue. But why it has taken so long, why there is such resistance, and why people feel so strongly about this issue, I do not fully understand.

 

[Hurkyl]

kvantti, setAI: people have already responded to your assertions many times. If you don't want to be crackpots, you would do well to stop mindlessly repeating them without any regard to the received criticism.

Explain where the calculations made by a quantum computer are performed when it solves the sub-problems associated with a single problem.

In the quantum computer: where else?


In fact, when I learned quantum computation in one of my classes, we learned it from a solidly Copenhagenist viewpoint.

 

[setAI]

kvantti, setAI: people have already responded to your assertions many times. If you don't want to be crackpots, you would do well to stop mindlessly repeating them without any regard to the received criticism.

this is the irony- the MWI IS now the mainstream/orthodox/dominant/whatever interpretation of QM- as acknowledged by virtually every major and minor professional physicist on the planet [minus a few slow-pokes in the USA and Penrose on odd-numbered-days]

it is rather shocking that even some of the moderators on this forum are actually going against what is considered the most rigorous empirically verified concept in physics- and they are mis-representing it here as something less- even crankish?!

the so-called 'received criticism" was a joke- totally refuting facts- and rejecting peer-reviewed science that is the basis for the most successful technology in human history!

you are firmly representing the crackpot view here- not us- I have 100 years of empirical QM data and the opinions of nearly every professional physicist in the world to back it up- you have a head-in-the-sand interpretation that tells you to "shut up and calculate"- how can you possibly think you represent the interests of real science here?

how do you reconcile your "crackpot" comment against the fact that the MWI [and similar interpretations] is now the only interpretation that professional physicists accept? what next? are you guys going to try and convince people that Darwinian Evolution or Plate Tectonics are crackpot pseudoscience as well? and that is not just a cheap shot- MWI has as much if not MORE experimental support than Natural Selection or PT- in fact it is the most empirically supported idea in physics at this time in history

of course the MWI is not complete- not the whole answer- but it is BY DEFINITION the only actual interpretation we have- as DD mentioned in the above interview- Copenhagen/Hidden Variable/ etc 'interpretations' are illogical and absurd- there aren't interpretations AT ALL- by definition MWI is the only version of QM that is a viable version of the theory-

ignorance is not an alternative to understanding! just becasue a handful of stick-in-the-muds haven't bothered to pick-up a physics journal for the last 6 years doesn't mean those of us who have should have to play nice and pretend that there are still other interpretations of QM worth discussing-

this is a moderated forum that discusses peer-reviewed QM- thanks to DD's work right now that is MWI and only MWI [follow the funding]

 

[setAI]

And for the question why the MWI has become "some sort of religion": it gives a coherent, local and deterministic description of reality and in my point of view, it would be illogical that there would be only one universe.

quite illogical- I never understood the 'single universe' conjecture- as it requires something like God: all empiricality shows that the world possesses causality and laws- and any such causal system has transfinite possible states and histories- for our universe to be the only one would require some process that neatly prevents/destroys/cancels out all other possibilities ins space AND time and only allows this one- this would be the grandest epicycle of all- and totally renders any theory assuming one universe as utterly moot and unphysical [or at least very limited ]

which is why as technology and theory advance more and more theories have a fundamental multiverse structure- QM/ Inflation/ M-Theory/ LQG all posit a phase space of possible structures in which the observed world is only a small region-

some form of multiverse is a self-evident fact unless you believe in a filtering deity- the MWI is the only version of QM that corroborates the physical necessity of the multiverse

 

[RandallB]

I'm confused -- I don't see anything in your post that talks about burdens of proof. In fact, I can't figure out what your point is at all.

Not meeting the Burden is stuff like:
“When a quantum computer solves a problem ………..it will PROVE
What more do you need to persuade you that other universes exist?" -David Deutsch

He didn’t say it had been proven; just that when and IF they actually make a true Q-C it will, (IMO they won’t). That is way short of any reasonable logic, and provides no proof for MWI or multiple realities.

All I’m saying is well founded logic (They teach it in University) IMO is sufficient to prove there must only be one complete reality.
If not, then Logic it self is wrong! - back to the beginning where you claim “I think therefore I am”.
If logic cannot carry the burden to prove the claim of one reality,
Then no one can use Logic to claim there own existence to be able to even question the claim or demand addition proof.

Just simple logic - works for a simple kind of guy like me

 

[setAI]

Not meeting the Burden is stuff like:
“When a quantum computer solves a problem ………..it will PROVE
What more do you need to persuade you that other universes exist?" -David Deutsch

He didn’t say it had been proven; just that when and IF they actually make a true Q-C it will, (IMO they won’t).

he said this will prove it to those who don't currently accept it- actual professional physicists have accepted the proof of MWI since it was demonstrated that separate computations on universal CNOT gates could be performed in parallel on BOTH possible paths of a photon in the two-slit experiment simultaneously-

All I’m saying is well founded logic (They teach it in University) IMO is sufficient to prove there must only be one complete reality.

Just simple logic - works for a simple kind of guy like me

so tell me what do you name the God/filter that murders all other possible outcomes of a physical processes in which all possible outcomes are observed?

 

[RandallB]

he said this will prove it to those who don't currently accept it- actual professional physicists have accepted the proof of MWI since it was demonstrated that separate computations on universal CNOT gates could be performed in parallel on BOTH possible paths of a photon in the two-slit experiment simultaneously-

so tell me what do you name the God/filter that murders all other possible outcomes of a physical processes in which all possible outcomes are observed?

Now there is one that " I can't figure out what your point is at all."
Care to prove you exist so I'll know you are real & not something from an unreal reality.

 

[Hurkyl]

this is the irony- the MWI IS now the mainstream/orthodox/dominant/whatever interpretation of QM- as acknowledged by virtually every major and minor professional physicist on the planet [minus a few slow-pokes in the USA and Penrose on odd-numbered-days]

It would be interesting to see the study that determined that. But this is a digression...

I have 100 years of empirical QM data

You just don't seem to understand what the criticism is. Copenhagen has the exact same 100 years of empirical QM data supporting it too. And if the Bohm interpretation ever figures out how to work in the relativistic setting, then it will too.

The whole problem is that you present a piece of evidence which is predicted by the Copenhagen interpretation (and Bohm too, I think), and somehow conclude that it proves MWI is the only tenable interpretation.

And, in your lashing out at any criticism, you seem to have missed the fact that I actually like the MWI interpretation, and find it the most natural of the "popular" interpretations. (Though I think I will change my mind once we can consider the relational interpretation popular)

which is why as technology and theory advance more and more theories have a fundamental multiverse structure- QM/ Inflation/ M-Theory/ LQG all posit a phase space of possible structures in which the observed world is only a small region-

Pretty much every scientific theory permits a very large space of configurations that will never be realized by our observed world...

some form of multiverse is a self-evident fact

Are you sure you meant "self-evident"? I thought that, even to you, it is only evident because you find it a natural consequence of QM.

IF they actually make a true Q-C it will, (IMO they won’t).

They already have. They just haven't made a "big" one.

Now there is one that " I can't figure out what your point is at all."
Care to prove you exist so I'll know you are real & not something from an unreal reality.

This is an ad hominem fallacy. The argument stands or falls on its own merit. It doesn't matter if it originated from an existing speaker.

 

[Chaos' lil bro Order]

Well, here is a challenge for you (and for everyone who doesn't believe in the MWI) from Deutsch (as presented in his book The Fabric of Reality):

Explain where the calculations made by a quantum computer are performed when it solves the sub-problems associated with a single problem. Eg. when factoring a 250-number digit using the algorithm[/url], the number of sub-problems is about 10^500 (the number of particles in the universe is about 10^80).
And yet, a quantum computer solves all the sub-problems at the same time. So how can it solve 10^500 problems during only one calculation, if we have only one computer in only one universe?

(It would take classical computer 10^500 times the time of a quantum computer to perform the same operation)

And for the question why the MWI has become "some sort of religion": it gives a coherent, local and deterministic description of reality and in my point of view, it would be illogical that there would be only one universe. Didn't you think that there are "other dimensions" when you were a kid?

Tell me then, how does the quantum computer in our Universe communicate with all the other 'virtual quantum computers' in the other Universes? Also, where is this quantum computer you speak of? This is such an abstract idea that the quantum computer calculates some of the sub-problems in other dimensions that I'm not sure it warrants a response. I'm ignorant on this subject, but what experiments have been done to confirm your quote?

 

[Careful]

** quote Hurkyl
And, in your lashing out at any criticism, you seem to have missed the fact that I actually like the MWI interpretation, and find it the most natural of the "popular" interpretations. (Though I think I will change my mind once we can consider the relational interpretation popular)
**

I must congratulate you for the ability to decide upon these fundamental matters according to the latest fashion in town. Perhaps, we should organize miss elections about these issues in the same way as this is done on some other forum - that would constitute the ultimate downfall of science.

Careful

 

[Hurkyl]

I must congratulate you for the ability to decide upon these fundamental matters according to the latest fashion in town. Perhaps, we should organize miss elections about these issues in the same way as this is done on some other forum - that would constitute the ultimate downfall of science.

Huh? I mean to say that I think RQM > MWI > Copenhagen > Bohm.

 

[kvantti]

kvantti, setAI: people have already responded to your assertions many times. If you don't want to be crackpots, you would do well to stop mindlessly repeating them without any regard to the received criticism.

Umm, sorry, I think this was my first message in this thread... I apologie if I have missed something (I don't follow these forums too often). :tongue:

In the quantum computer: where else?

In fact, when I learned quantum computation in one of my classes, we learned it from a solidly Copenhagenist viewpoint.

Yes, you can always say something like "all the different calculations are performed simultanously as a superposition of every possible calculation", but that isn't exactly a physical description of what is happening in a quantum computer... it is more or less a description of the mathematics.

OK, let's assume that the MWI is false (which it, ofcourse, might be). How would you explain the physical behaviour of a quantum computer?

 

[kvantti]

Tell me then, how does the quantum computer in our Universe communicate with all the other 'virtual quantum computers' in the other Universes?

Through quantum interference. Different universes can interfere with each other if the quantum state of the system involved is coherent (as in a quantum computer).

Also, where is this quantum computer you speak of? This is such an abstract idea that the quantum computer calculates some of the sub-problems in other dimensions that I'm not sure it warrants a response. I'm ignorant on this subject, but what experiments have been done to confirm your quote?

IBM has the most advanced quantum computer nowadays with seven qubits. See this.

Oh and mathematically you can just say that "all the different calculations are in a superposition in the quantum computer during the calculation", if you don't want to think the MWI way.

 

[Careful]

Huh? I mean to say that I think RQM > MWI > Copenhagen > Bohm.

But what is YOUR idea about quantum mechanics ?! This entire discussion is about one's favorite color of spaghetti, while all the pasta tastes the same. It seems to be much more intelligent to place this question in the light of some problematic aspects of modern theoretical physics : (a) the problem of vacuum energy vis a vis the cosmological constant (b) the issue of realism (c) the problem of time (d) the validity of special relativity at all energy scales. Then, depending upon your answers on these (and other) issues you will find yourself confined to one of these religions, or you feel the logical need to dig deeper into QM itself. One question to start with for example is wheter one truly believes gravity to be necessary to even obtain a well defined theory of quantum electrodynamics.

Careful

 

[NateTG]

OK, let's assume that the MWI is false (which it, ofcourse, might be). How would you explain the physical behaviour of a quantum computer?

That's not a useful stipulation. MWI, Bohmian Mechanics, and the Plug and Chug interpretation all make identical predictions so the only way that MWI can be scientifically falsified is if all of the other interpretations also have the same problems.

Moreover, and this is something people love to ignore, physics does not and will never explain anything rather, physics is a collection of theories that make predictions. Statements like 'things fall because of gravity' are misleading - it would be better to say 'we call the tendency of things to fall gravity'.

As such, interpretations of quantum mechanics are (from a scientific point of view) really primarily interesting because they can lead to experimentally verifiable predictions. Otherwise, we might as well be discussing how many angels can dance on the head of a pin.

The fact is that (assuming the physics is correct) the quantum computer will work regardless of whether you think of it as a bunch of intereacting 'worlds', a winding maze of particle paths, or a black box.

 

[RandallB]

They said IF they actually make a true Quantum-Computer, it will, (IMO they won’t).

They already have. They just haven't made a "big" one.

What does that mean – something like a little bit pregnant but not really yet?

Plus even if they can come up with Q-C or other proof of MWI convincing to those that are not already convinced, that still only ‘proves’ one reality.

MWI is one thing but it doesn’t call for more than one reality!
The idea that one reality where say MWI is correct and BM is wrong;
and a second reality where say BM is right and there are no MW’s of MWI; ----- And Are both true ?

IMO that is beyond an ‘ad hominem fallacy’ it just logically ridiculous.
What argument would not fall on its own merit trying to support such a thing with anything like rational logic?

 

[AnssiH]

Well, here is a challenge for you (and for everyone who doesn't believe in the MWI) from Deutsch (as presented in his book The Fabric of Reality):

Explain where the calculations made by a quantum computer are performed when it solves the sub-problems associated with a single problem. Eg. when factoring a 250-number digit using the algorithm[/url], the number of sub-problems is about 10^500 (the number of particles in the universe is about 10^80).
And yet, a quantum computer solves all the sub-problems at the same time. So how can it solve 10^500 problems during only one calculation, if we have only one computer in only one universe?

(It would take classical computer 10^500 times the time of a quantum computer to perform the same operation)

And for the question why the MWI has become "some sort of religion": it gives a coherent, local and deterministic description of reality and in my point of view, it would be illogical that there would be only one universe. Didn't you think that there are "other dimensions" when you were a kid?

Like I've said in about every post to this thread, we make certain assumptions about "what exists" in reality and about how they behave to come to explain how the reality works to our selves. The above questions, about where the "calculations" happen and so on, only make sense in so far that you want to talk about "calculations" (and the related entities and concepts that you imagine is performing these "calculations", in this case in multiple universes) and MWI makes sense only in so far that you make certain assumptions about such things as the reality of a photon and interference between universes.

In fact, if you take a look at the opening post here:
https://www.physicsforums.com/showthread.php?t=130623
you'll notice how one can say the "calculations" happen or rather simply "exist" in static manner in spacetime just by insisting that spacetime really exists the way Einstein believed it to exist (Of course it will be difficult to explain why there seems to exist any "moments" at all, but that's a different discussion). One way to put it would be to say that the photon moves back and forth in time so that all its possible trajectories interfere, but this is wrong vocabulary because there is no motion in spacetime.

I am confident that all interpretations have their own answers about how the phenomena happen so to come to predict the exact same observable phenomena. So after all is said and done, many-worlds interpretation is just that, an "interpretation". At this stage we cannot pick and choose any QM interpretation to be the real deal.

Also if you have followed my posts in this thread you might have noticed how I've asserted that - quite likely - the reason why QM seems so damn odd to us is that we are trying to explain a behaviour of such entities that do not exist in such manner as we imagine them to exist. It is like explaining the behaviour of a rainbow after asserting it is an object which originates from a pot of gold, and only once one realizes how rainbow is rather the interference pattern on the surface of the observer, its behaviour starts to make sense.

Likewise, if you insist on the information between atoms to travel in the form of tiny billiard balls and on top of that imagine the motion of those billiard balls to exist in Newtonian sense (only look at it from one inertial frame) you may be forced to assert that the photon exists in many worlds so to exhibit the behaviour we observe. We may have to question the nature of many things to come up with more accurate answers, like the nature of space, matter, light, motion(/time), energy... Maybe even discard these concepts to understand this system we call "reality" from a completely new angle.

(On a related note, have people formed opinions about this idea of discrepte, stepwise spacetime expansion causing quantum behaviour?
http://www.estfound.org/
Haven't had time to really look into it, does it show some obvious weaknesses right off the bat?)

So, just what NateTG is saying, physics really is quite literally a collection of theories or rather assumptions about what exists and how they behave. And like I said before, because of how our understanding works physically, we can only deal with reality by assuming there exists such and such entities and asserting they have such and such relationships between each others. Because this is the only thing we are capable of, it seems to us that reality really is like this, but little bit of philosophy can show that this is not exactly true; reality does not actually work with concepts. The mental model we have about reality in our head really is just an expression of the real thing, and it is not accurate or even "the metaphysically correct way" to express reality. (And any math you produce is also merely describing the behaviour of some "entity" you imagine to exist metaphysically in that sense)

And btw, MWI gaining ground as the "favourite way" to describe reality in some circles doesn't mean it is true, it just means it is one of the easiest ways to "imagine/visualize" QM phenomena in your mind. Think about how you try to visualize any black-box system when you are trying to back-engineer how its behaviour comes about, and you will realize how the assumptions with which you find it easiest to imagine the functions of the black box don't mean that is actually what happens inside. There are always many ways to produce some desired behaviour. Any system builder/programmer knows this very well.

And my comments about MWI becoming a religion are referring to how I find that MWI-people are continuously asserting theirs is "the only possible interpretation". Please understand that no one is saying it "cannot be true", but that it is not something that has been proven to be true in any sense. I am certainly happy to see many sensible people at this thread who still understand this, and I hope MWI won't become so standard that considering other options will be viewed as heretical or crackpot. It is important to be honest about it being just an interpretation unless you want to see everyone believe in it like a religion. And you don't want this to happen if you believe in scientific method, yes?

 

[Chaos' lil bro Order]

Through quantum interference. Different universes can interfere with each other if the quantum state of the system involved is coherent (as in a quantum computer).
.

Are you talking about p-branes?

What defines two events in MWI anyways? I mean what is the smallest increment of information, whether it be spacial, temporal, or any other physical property you can think of, that must occur before the 'father' universe splits into two and the 'daughter' universe is birthed?

 

[Hurkyl]

This entire discussion is about one's favorite color of spaghetti, while all the pasta tastes the same.

Right -- but I was talking to someone who thinks spaghetti has to be purple, and thinks that my motivation for saying all pasta tastes the same is because I'm an idiot that doesn't like purple.

 

[AnssiH]

I believe the idea is rather, that all the possible universes exist "all the time" and interfere with each others. So the model is relying on certain ideas about how photons exist and how they interfere with other photons in other universes.

So, when someone is claiming this is the only way QM could work, I might just as well start asserting that when a rainbow seems to mimic the motion of the observer without delay, it can be explained in non-local terms only by assuming we are seeing a rainbow of a "different universe" every time we move.

Sure, this would make the phenomenon local, but in the case of rainbow we now know enough about how it exists to be able to see how its observed "motion" occurs in completely classical terms and within one universe, and yet there is a different rainbow visible for every observer, or rather that we should not assign identity to a rainbow; there is no rainbow at all without an observer. (This is a case of realism where something cannot exist without an observer, in completely classical sense)

Likewise with QM, the motion or the "apparent trajectory" of the photon really does depend on where it's going to be observed (one way or another), and to assume there really was a photon (with identity) in flight is already an assumption that is likely to be wrong to some extent, and will lead you to assert there must be multiple universes and we are merely observing photons from one.

So, what I'm saying is... dig deeper gentlemen.

 

[Careful]

Right -- but I was talking to someone who thinks spaghetti has to be purple, and thinks that my motivation for saying all pasta tastes the same is because I'm an idiot that doesn't like purple.

Hehe, I noticed that, but you also said that you might choose for the relational colored one, once this color would gain more popularity. My point being that whatever interpretation you pick, you keep on being stuck with some embarrasing shortcomings of the formalism itself. For example, I have to think hard about Bell inequality violation and spin statistics in Barut self field (although I could put them in by hand), but there is absolutely no problem with realism, time, special relativity and vacuum energy (tell that to some QG people - all their deep problems vanish in thin air).

Cheers,

Careful

 

[Hurkyl]

Hehe, I noticed that, but you also said that you might choose for the relational colored one, once this color would gain more popularity.

I prefer RQM over MWI now -- but if I was asked to choose between the popular interpretations I'd have to pick MWI since AFAIK, RQM isn't one of them yet.

you keep on being stuck with some embarrasing shortcomings of the formalism itself

Embarassing shortcomings are in the eye of the beholder.

 

[Careful]

I prefer RQM over MWI now -- but if I was asked to choose between the popular interpretations I'd have to pick MWI since AFAIK, RQM isn't one of them yet. Embarassing shortcomings are in the eye of the beholder.

This is exactly the miss-election attitude I was referring to in the beginning, I remember asking you what YOUR view towards QM is. Embarrasing shortcomings are not in the eyes of who perceives them, but in those minds which do not wish to adress them even when it is well known that the latter issues are definitely problematic. String theory does adress the vacuum problem by making a supersymmetric ansatz : at that moment, you can say whether you find such mechanism using exotic particles credible or not (I certainly don't). Anyway, if you do not believe some detailed matter content to be responsible for the cancellation of the vacuum energy, then the most direct step would be to question the phenomenon (in either the renormalization procedures) at its very roots.

Careful

 

[kvantti]

I was writing a long post and my computer crashed so I'm pretty frustrated at the moment and therefore I will state my matter briefly:

NateTG:

That is an instrumentalist point of view. I'm glad that not all physicists are instrumentalists.

AnssiH:

You obviously believe in some sort of "hidden variable" theory. Fair enough. But keep in mind that even you are interpreting quantum mechanics from your own point of view, and in my eyes it doesn't differ from the Copenhagen interpretation; you and CoI state that the formulas of quantum mechanics do not describe reality as it is, but only probabilities of observations within reality. The difference between CoI and your interpretation is that the CoI doesn't explain how the "probablities" can interfere and entangle... it just says they do. You seem to have your own vision how they actually do interfere (as we all do).

The MWI says just the opposite: the formulas of quantum mechanics describe reality as it is. What would be simpler? The concept of multiverse emerges naturally from this kind of thinking. It also explains quantum interference and entanglement in a very simple manner.

It is important to be honest about it being just an interpretation unless you want to see everyone believe in it like a religion. And you don't want this to happen if you believe in scientific method, yes?

Yes, it is "just an interpretion" of quantum mechanics. But it also a "theory" of multiverse. A theory that most quantum cosmologists and quantum computer researchers find compelling, because it offers explenations of the physical behaviour of the quantum system they study, rather than just "cold mathematics".

-- you'll notice how one can say the "calculations" happen or rather simply "exist" in static manner in spacetime just by insisting that spacetime really exists the way Einstein believed it to exist.

This isn't true in the case of quantum computers; the calculations are based upon quantum effects, such as quantum interference and entanglement, so you can't just say "it just acts as if the different calculations would interfere, but actually they don't; the calculation and the result just already exist in a static spacetime." Quantum computers actually prove that quantum interference and entanglement are real phenomenom; not just illusions of "static spacetime." And that been said, you can't say that a photon moves as if it would interfere with itself; it actually does interfere with itself.

 

[tehno]

Sorry for interrupting this discussion,I'm really no expert on this but I can't resist not to ask.
With their capability of processing information can a quantum computer one day answer the ethernal question of finite strategy games:say Chess or GO?Estimation is that there are about $$~10^{60}$$ legal chess positions.

 

[kvantti]

Are you talking about p-branes?

What defines two events in MWI anyways? I mean what is the smallest increment of information, whether it be spacial, temporal, or any other physical property you can think of, that must occur before the 'father' universe splits into two and the 'daughter' universe is birthed?

Here is a FAQ considering the MWI. You'll probably find answers for your future questions there. A single universe is irreversibly split into many universes when the quantum system involved in the splitting decoheres. But that doesn't mean the decoherence causes the splitting; the universes split all the time, be there interactions or not. Decoherence only distinguishes the universes from each other and therefore they can't interfere with each other anymore.

Sorry for interrupting this discussion,I'm really no expert on this but I can't resist not to ask.
With their capability of processing information can a quantum computer one day answer the ethernal question of finite strategy games:say Chess or GO?Estimation is that there are about $$~10^{60}$$ legal chess positions.

Yes, a quantum computer can resolve this kind of calculation very fast.