Explaining the Quantum Mystery: Are Parallel Universes the Answer?

[Evo]

I think he puts it at level III, but I haven't read the paper. Max gets away with this cause he does a lot of useful stuff too.

That's too funny.

Isn't that how it goes? As long as you're doing something useful, they'll let you play with your pet theories?

How does someone like me sort the wheat from the chaff?

 

[SpaceTiger]

How does someone like me sort the wheat from the chaff?

There's nothing wrong with his multiverse classification, it's just not very useful. Even the multiverse predicted by inflation is highly speculative, I would say, since it assumes that we've a full grasp of the physical limits of the theory. I'm afraid I can't give a very helpful description beyond that, however.

It's difficult to near impossible for a novice to judge the plausibility of the results reported in the media. They're very often wrong, misleading, or irrelevant in mainstream astronomy. Even an astronomer wouldn't be able to give you a useful judgement on the majority of the things reported, since they will only be fully aware of the events related to their own work. It's a shame that there isn't more control over what actually gets reported. Universities will allow an article on anything that interests the journalists, and the researchers usually don't mind because they get free publicity.

 

[Chris Hillman]

Shut a door, start a conspiracy theory?

Yep. What interested me most were questions that don't generate grant money or careers.

Well, call me Dr. Pangloss, but it seems to me that genuine scientific success always generates grants and students, so isn't this simply a lamentation of personal failure to make sufficient scientific progress toward solving your favorite enigma?

However, this doesn't mean that those questions should be ignored or forgotten.

We might offer different answers to the question "what are the deepest enigmas in science?", but whatever our respective lists might be, no-one is suggesting that we should collectively ignore/forget deep questions!

And I think it is true that orthodoxy can stifle valid discussions of the deepest issues. I once had a physics professor close her door so that she could freely discuss her views on such matters, and I was quite struck by this.

I think you're making too much of that incident. Maybe she realized that with rising passions you and she were disturbing her neighbors?

I have a different interpretation: raising the bar when it comes to revolutionary change by adopting some proposed solution to some fundamental enigma internalizes and intensifies discussion and debate. Those obsessed with their own pet theory "solving" the enigma spend far more time in internal critiques than they might with humdrum science (or else become the butt of a jest by Kibo*). This is a good thing and should be encouraged, since it ensures that when scientifically useful "revolutionary" solutions do emerge, they are accompanied by spectacularly well argued and carefully expressed arguments. Einstein 1905 is a good example, in which overwhelmingly persuasive arguments from a scientific unknown quickly captured the attention and indeed the support of the leaders of physics (well, Planck and friends; those who couldn't make the transition to relativistic physics were unceremoniously deposited in the dustbin of science, which was also a good thing).

*You know, the Guy that Runs the Internet.

I happen to think that as a rule, the best papers are singly authored (is Christine Dantas hereabouts, by any chance?), and if so, this simply reinforces my suspicion that laments about the alleged "discouragement of open discourse" concerning some fundamental enigma reduce upon closer examination to the confession "no Einstein I".

(I assume we are discussing something like the interpretation of QM; if not maybe this is one time when you should not disabuse me! Also, I stress that I am assuming that we all belong to the group of individuals who have struggled and failed by dint of our own efforts to resolve some deep enigma of science, whatever humdrum successes we may have enjoyed.)

IOW, scientific revolutions, unlike political revolutions, are best accomplished by lone pioneers, in private. After that it is simply a matter of publishing the enunciation of the new marching orders.

To toss another idea into the mix: with the exponential growth of the hierarchical structure of mathematics, which I like to define as the art of reliable reasoning about simple phenomena, and which is the foundation of science, humans are becoming obsolete as the agents of science. Clearly longer-lived and far more intelligent scientists are needed. If they do not exist they must be invented.

(Some cry COI when I say this.)

 

[Chris Hillman]

Who gets to play in the sandbox of science?

Isn't that how it goes? As long as you're doing something useful, they'll let you play with your pet theories?

Even better, we/they will pay some mind to your musings. This actually makes perfect sense, since doing manifestly useful "ordinary science" (to adopt the phrase of Kuhn) provides an easy check on the continued sanity of someone like Tegmark.

How does someone like me sort the wheat from the chaff?

I think you need to know some minimal number of experts you can canvass.

 

[Evo]

I think you need to know some minimal number of experts you can canvass.

That's why I am glad I'm here. I can't tell you how much my understanding and level of acceptance has changed/increased since coming here. Of course I will always be just a listener, it helps to know what to listen to among all of the noise.

 

[vanesch]

Not sure I agree with the analogy, but agree that things like closed timelike curves in Lorentzian manifolds do present a challenge to the physical interpretation of such spacetimes. It might also be worth mentioning that the dividing line between classical physics and quantum physics has been increasingly blurred as mathematicians have discovered more and more analogies/generalizations unifying various mathematical ideas underlying "quantum" and "classical" physics, and as physicists have found more and more applications of "quantum physics" notions in "classical physics".

I was simply pointing out that assuming the "physical, ontological existence" of a spacetime manifold is to GR what the "physical, ontological existence" of statespace and the state vector is to quantum theory. So in as much as you give a genuine existence to spacetime in GR - as opposed to just a mathematical trick to calculate observations in GR - you can give a genuine existence to quantum states in quantum theory, as opposed to consider that it is just a calculational trick to calculate probabilities of outcomes.

You don't need closed timelike curves or anything: the very assumption of a physical existence of spacetime is enough. You give an ontological status to the axiomatically introduced basic mathematical structure in GR. If you do the same in QM, you arrive at giving an ontological status to what's commonly called "the wavefunction", and if you don't do anything else, you have an ontology like MWI.

A question in MWI like "why do I only observe 1 world" is then equivalent to the GR-spacetime interpretation as "why do I only observe 1 spacelike slice". You can really push the two analogies quite far. "Is there really someone else in another universe who looks a lot like me but had another outcome ?" versus "Does Julius Caesar have some physical existence somewhere in another slice of spacetime ?"

This is BTW where I find some utility of the MWI view. In as much as contemplating a genuine existence of a physical spacetime helps one understand GR (whether this spacetime "really" exists or not, and is only a mathematical trick) in the same way, taking on an MWI view on quantum theory gives one some "intuition" for it, whether superposition 'really' exists or not.

 

[Astronuc]

classical physics and quantum physics has been increasingly blurred as mathematicians have discovered more and more analogies/generalizations unifying various mathematical ideas underlying "quantum" and "classical" physics, and as physicists have found more and more applications of "quantum physics" notions in "classical physics".

I think therein lies part of the problem, which is the belief that the models we contruct and the mathematics reflect the reality, or for some, are the reality. The mathematics and models provides a description as best as we can, but its not the reality, and at best its an approximation.

I do predictive analysis and I know the limitations of the math and models (and computational systems), and also the limitations of the inputs (I.C and B.C), and we often find exceptions and nonlinearities, some of which become significant in time, while others are trivial and insignificant. In some cases, we simply construct better models and get better predictions, and being a few percent off in 4-6 years is pretty darn good.

The greatest challenge (and greatest pressure) is predictive failure analysis.

The foundation of predictive analysis is a robust model and the experimental work (testability) involving both separate and integral experiments upon which individual models and the integral models are based.

Is there anything in astronomy or QM that requires MWI in order to make some model/mathematics fit what is observed in this universe - or rather what is observed locally? And then if so, does the fact that MWI is required to make a model work mean that something is wrong with the model?

 

[Chris Hillman]

Seeking clarification

I was simply pointing out that assuming the "physical, ontological existence" of a spacetime manifold is to GR what the "physical, ontological existence" of statespace and the state vector is to quantum theory. So in as much as you give a genuine existence to spacetime in GR - as opposed to just a mathematical trick to calculate observations in GR - you can give a genuine existence to quantum states in quantum theory, as opposed to consider that it is just a calculational trick to calculate probabilities of outcomes.

OK, I misunderstood.

You give an ontological status to the axiomatically introduced basic mathematical structure in GR.

Actually, I don't, and have often posted warning against that attitude!

At least, assuming I am correct in assuming that by saying "you give an ontological status to the axiomatically introduced basic mathematical structure in GR" you mean "you believe that spacetime exists in Nature and really has the structure of a Lorentzian manifold". If you meant only that when working with gtr I behave as if I believe this when interpreting results of some computation in a Lorentzian manifold, then I am probably guilty as charged

A question in MWI like "why do I only observe 1 world" is then equivalent to the GR-spacetime interpretation as "why do I only observe 1 spacelike slice". You can really push the two analogies quite far.

Sorry, I don't understand what you mean by asking (in the context of Lorentzian manifolds interpreted as a model spacetime, I take it) "why do I only observe 1 spacelike slice"? And what does this have to do with "blocks"? (I understood you to be using that term as it is used in the gtr literature, e.g. in discussing various "blocks" making up a Carter-Penrose diagram depicting the conformal structure of some Lorentzian manifold.)

 

[Chris Hillman]

Hi Astronuc,

I think you might have misunderstood my remark, which was tangential to this discussion. I was simply saying that upon adopting a more sophisticated view of the underlying mathematics, the old distinction between "classical physics math" and "quantum physics math" becomes blurred.

part of the problem, which is the belief that the models we contruct and the mathematics reflect the reality, or for some, are the reality. The mathematics and models provides a description as best as we can, but its not the reality, and at best its an approximation.

That's what I've always said whenever the subject has come up; in fact, in my experience not understanding this is one indication that my correspondent doesn't really understand what theoretical physics is all about.

Sorry for any confusion my choice of words may have caused!

 

[vanesch]

Actually, I don't, and have often posted warning against that attitude!

At least, assuming I am correct in assuming that by saying "you give an ontological status to the axiomatically introduced basic mathematical structure in GR" you mean "you believe that spacetime exists in Nature and really has the structure of a Lorentzian manifold". If you meant only that when working with gtr I behave as if I believe this when interpreting results of some computation in a Lorentzian manifold, then I am probably guilty as charged

Oh, that's interesting ! I didn't know that. The few relativists I know take - as far as I understood them - the spacetime manifold as "real" (ontological). It was in that respect that I considered MWI versus the spacetime manifold in GR. If you do not take that manifold for real - even for the sake of getting an intuition for the way GR (as a theory) behaves - then I fully understand how you cannot take MWI seriously, even for the sake of getting a better feeling of how QM works...

And what does this have to do with "blocks"? (I understood you to be using that term as it is used in the gtr literature, e.g. in discussing various "blocks" making up a Carter-Penrose diagram depicting the conformal structure of some Lorentzian manifold.)

No, not at all, I'm not that sophisticated (although I vaguely understand what you are alluding to). I was alluding to the "static spacetime manifold block universe" which, I thought, was used in interpretational issues with GR - but given your earlier paragraph, this point is moot.

 

[Chris Hillman]

The few relativists I know take - as far as I understood them - the spacetime manifold as "real" (ontological).

Are you sure about that? Did you ever politely but firmly interrogate them about their ontological attitude toward spacetime models? I would be quite amazed if any specialists in gtr truly believe that our universe is literally a Lorentzian manifold. C.f. "quantum foam" and all that.

(If you assiduously Google for my posts to UseNet and elsewhere years ago, you can probably verify that in previous comments I have noted a rare emotional outburst by Chandrasekhar in which he seemed to say that he was awed by the realization that the exterior of a black hole in Nature is literally a Kerr spacetime [sic]. Since he was an expert on perturbations, he can't possibly have believed any such thing, but since he is dead, I can't ask what he did mean, so I think it best we shrug helplessly and move on.)

No, not at all, I'm not that sophisticated (although I vaguely understand what you are alluding to). I was alluding to the "static spacetime manifold block universe" which, I thought, was used in interpretational issues with GR - but given your earlier paragraph, this point is moot.

I'll go out on a limb and guess that you often read hep-th papers but rarely read gr-qc papers. I, OTH, often read gr-qc papers but rarely read hep-th papers. I will guess further that whatever you read (perhaps in a section discussing some aspect of the "philosophy of spacetime"?) about "block universe" might refer to a decomposition of a Lorentzian four-manifold as a disjoint union of infinitely many spacelike hyperslices (Riemannian three-manifolds). If so, I still don't understand the question "why do I observe only one hyperslice?"

 

[Ivan Seeking]

Well, call me Dr. Pangloss, but it seems to me that genuine scientific success always generates grants and students, so isn't this simply a lamentation of personal failure to make sufficient scientific progress toward solving your favorite enigma?

I was too smart to go far enough to fail.

 

[Ivan Seeking]

For questions that are purely philosophical, it's not clear that the scientific community should even be involved.

I hardly think this applies. For example, the measurement problem is a problem of physics, not philosphy.

In fact I think this demonstrates the problem that I observed. When we don't have an answer, call it philosophy. I was talking about foundational problems in physics, and by the end of your post, you made this about religion.

 

[SpaceTiger]

I hardly think this applies. For example, the measurement problem is a problem of physics, not philosphy.

In fact I think this demonstrates the problem that I observed. When we don't have an answer, call it philosophy. I was talking about foundational problems in physics, and by the end of your post, you made this about religion.

I think you may have a bit of a persecution complex, here. I never said that the measurement problem was a religious issue, nor did I say that it was a matter of pure philosophy. The example I used was primarily in astrophysics and was meant to help explain the attitude of scientists towards "sweeping" questions.

I would, however, say that if the "interpretations" of the measurement problem are not producing any new predictions or ways of distinguishing them, scientists would be right to avoid expending a great deal of energy studying the topic. I am not a theoretical physicist, so I don't know the extent to which this is the case, but my impression is that we haven't seen much progress in the last 50 years or so.

The other point I was making was that people in the scientific community that spend a great deal of time worrying about things of this nature are often working with religious or philosophical baggage and are therefore viewed with suspicion. In that regard, I was trying to explain to you why this is sometimes a "closed door" topic of discussion. It is not a conspiracy to enforce scientific dogma, as you seem to be making it out to be.