Many Worlds Interpretation and Coffee

[phillovix]

The MWI does not say there are "an infinite amount of universes". It says there is just one universe, but its quantum wave function does not have any interpretation as a single classical "world".

Oh fascinating!
Thank you again for your reply! ^_^

<3 Phillip

 

[Zafa Pi]

Or to quote R. M. Wald, "If you really believe in quantum mechanics, then you can't take it seriously."

How do you interpret that?

 

[nikkkom]

Wonderful, thank you for your response, given me a lot to think about.
Given what I've read, I am favoring a collapse style interpretation. I think there is an infinite repetition of a finite amount of possibilities.

Collapse interpretation has a problem with nested Schrödinger's cat experiments. It basically says that cat state collapses when it is observed, but only if the "observer+cat" system itself is not in another, bigger box. If it is, then "observer+cat" system is still in a superposition until it is in turn observed by an outer observer (unless the "observer2 + [observer+cat]" system itself is not in another, bigger box...).

This, or course, is not logically inconsistent. It just sounds ridiculous: cat knows when its state should collapse based on the number of nested boxes it sits in?

 

[secur]

If the only problem with "logically consistent" collapse is that it "sounds ridiculous" to some people - a purely subjective judgment - then, there's really no problem with collapse.

 

[nikkkom]

If the only problem with "logically consistent" collapse is that it "sounds ridiculous" to some people - a purely subjective judgment - then, there's really no problem with collapse.

All QM interpretations are ridiculous in one way or another. Looks like people pick ones they like based on which kind of "ridiculous" is more tolerable to them.

I am mathematician by education, so infinities and infinitesimals of various kinds are not a problem for me, hence MWI with its infinite branching and very low probabilities of "almost anything happening" does not sound especially problematic to me (evidently, some people are finding *that part* "ridiculous").

 

[houlahound]

Why bother talking about other world's/ universes if it is impossible to detect their existence?

Seems like mental masturbation.

What's the motivation for the discussion?

What can possibly be learned about this universe from these discussions?

Genuinely curious.

 

[secur]

@houlahound, it's a good question although I can't endorse your negative characterization ... The best answer to "what good is MWI?" I've seen is in Hugh Everett's original paper:

"Relative State" Formulation of Quantum Mechanics, by Hugh Everett III, in REVIEWS OF MODERN PHYSICS VOLUME 29. NUMBER 3. JULY 1957 http://www.univer.omsk.su/omsk/Sci/Everett/paper1957.html

His focus on GR is a bit limited, I think MWI is useful when applying QM in many theoretical contexts. Regardless, Everett's justification of MWI is very good IMHO. See what you think of it.

Relevant quote:

1. INTRODUCTION

The task of quantizing general relativity raises serious questions about the meaning of the present formulation and interpretation of quantum mechanics when applied to so fundamental a structure as the space-time geometry itself. This paper seeks to clarify the formulations of quantum mechanics. It presents a reformulation of quantum theory in a form believed suitable for application to general relativity.

The aim is not to deny or contradict the conventional formulation of quantum theory, which has demonstrated its usefulness in an overwhelming variety of problems, but rather to supply a new, more general and complete formulation, from which the conventional interpretation can be deduced.

 

[houlahound]

No prob with squeezing what you can out of a theory, that's all good.

Worrying about events in extra universes IMO is idle.

 

[stevendaryl]

No prob with squeezing what you can out of a theory, that's all good.

Worrying about events in extra universes IMO is idle.

Well, when it comes down to it, advanced physics and mathematics are just extremely sophisticated forms of entertainment. Unless you're building semiconductors or working on superconductors, (or maybe a small number of other careers), physics isn't for practical purposes.

 

[houlahound]

Unless you're building semiconductors or working on superconductors, (or maybe a small number of other careers), physics isn't for practical purposes.

sssshhhhhh!

Everyone ignore this quote.

you never ever say that in public... Have you forgotten the F word man, the F word;

FFFFFFunding.

 

[rbelli1]

Well, when it comes down to it, advanced physics and mathematics are just extremely sophisticated forms of entertainment. Unless you're building semiconductors or working on superconductors, (or maybe a small number of other careers), physics isn't for practical purposes.

Semiconductors are such a small area of research and industry. I can't for the life of me remember the last time I used something as esoteric as semiconductors. What do they do again?

BoB

 

[stevendaryl]

Semiconductors are such a small area of research and industry. I can't for the life of me remember the last time I used something as esoteric as semiconductors. What do they do again?

BoB

Ha. Ha. Everybody USES semiconductors, but I'm guessing that a very tiny number of people actually research, design and build them. For the rest of us, physics is mostly for entertainment.

 

[houlahound]

I prefer valves, yeah laugh until EMP Armageddon and yr cheap little semiconductors are all crying.

Oh and yr semiconductor enabled digital music sounds like crap, analog forever.

 

[rbelli1]

For the rest of us, physics is mostly for entertainment.

I have to remember not to feed the trolls.

BoB

 

[secur]

Applied physics has many other achievements than just semiconductors. Some topics and technologies include lasers, MRI, nukes, sonar, radar, electronics, nanotechnology, all sorts of materials science ... probably one could list hundreds of items, if one wanted to go to the trouble. The improvements in plastic, metal, glass, weapons, engines, ... in our lifetimes are evident. True, much of this comes under the heading, instead, of chemistry and engineering. But I'd say many key advances could reasonably be considered part of physics.

It's only most topics in theoretical physics which have become virtually meaningless in the last 65 years or so. Equivalent, in spirit and utility, to the study of angels dancing on heads of pins.

 

[secur]

Actually theoretical physics also has many worthwhile aspects. It's very simple: the worth of a theory is proportional to the amount of data, experimental and observational, it encompasses. And inversely proportional to the publicity.

How does this relate to OP? MWI as a mathematical tool is justified, almost, by all QM data. (Except for the unresolved issue of Born's rule.) However MWI as reality has no contact with experiment, or observation, at all. We (almost certainly) can never detect those "many worlds". So as a convenient mathematical formulation - somewhat analogous to Hamilton and Lagrange formulations - it's fine. But it's extremely pointless to worry about cups of coffee, twins becoming president, twins murdering or committing suicide, etc, in those many worlds. Very much like angels dancing on pins.

Not surprisingly the worthwhile aspect of MWI - just as a mathematical tool - gets almost no publicity. Everett's original idea is ignored. Instead the useless aspect appears often in pop-sci. That's why many members of the public interested in physics, such as OP, ask about that so often.

Of course very few physicists concern themselves with theory that has no contact with data. Perhaps, 1%. That's not much, and after all, some good may come of string theory, etc - who knows? The only problem concerns the public. There's only a limited "bandwidth" for physics in popular media, and I guess more than half of it is completely wasted. This has many negative ramifications for society. It's a major factor in the decline in STEM disciplines in the US (I don't really know about elsewhere). Physics could be charging ahead, attracting the best and brightest, receiving great respect from non-physicists, if the public image was presented well. Basically, just stick to the data, and almost ignore theory. (Astronomical imagery is a good example of the right kind of publicity.) Instead ...

 

[Zafa Pi]

All QM interpretations are ridiculous in one way or another. Looks like people pick ones they like based on which kind of "ridiculous" is more tolerable to them.

I am mathematician by education, so infinities and infinitesimals of various kinds are not a problem for me, hence MWI with its infinite branching and very low probabilities of "almost anything happening" does not sound especially problematic to me (evidently, some people are finding *that part* "ridiculous").

The Tarsi-Banach Theorem is a mathematical result that I've proved in lectures several times, but would never accept as a result of physics.

 

[Demystifier]

How do you interpret that?

I interpret it as a special case of another quote:
"Truth and clarity are complementary." - Niels Bohr

 

[Demystifier]

The Tarsi-Banach Theorem is a mathematical result that I've proved in lectures several times, but would never accept as a result of physics.

Is it just because of the existence of atoms, or because you don't think that the axiom of choice represents a physical choice?

 

[Zafa Pi]

I interpret it as a special case of another quote:
"Truth and clarity are complementary." - Niels Bohr

Oh, I get it, the truth and clarity operators don't commute, they work at home.
Don't you think it's about time you changed your moniker to Mystifier?

 

[Demystifier]

Don't you think it's about time you changed your moniker to Mystifier?

There is no demystification without prior mystification. In most of my posts I do my best to demistify things. But sometimes I go in the opposite direction, as in https://www.physicsforums.com/threads/what-is-quantum-theory-about.767672/ .

 

[vanhees71]

I interpret it as a special case of another quote:
"Truth and clarity are complementary." - Niels Bohr

Well, then Bohr definitely wrote only about true things.

 

[Zafa Pi]

Is it just because of the existence of atoms, or because you don't think that the axiom of choice represents a physical choice?

Atoms?? I thought your view of reality was continuous. I don't accept the T-B Thm for physics because by now some alchemist would have the would's weight in gold.
The axiom of choice is not a sufficiently well ordered topic for QM , and should be maximally filtered out using the Zorn rule.

 

[Zafa Pi]

There is no demystification without prior mystification. In most of my posts I do my best to demistify things. But sometimes I go in the opposite direction, as in https://www.physicsforums.com/threads/what-is-quantum-theory-about.767672/ .

OMG, that referenced post of yours is more depressing than Donald Trump.

 

[Demystifier]

OMG, that referenced post of yours is more depressing than Donald Trump.

What if I tell you that I have a theory that solves all these questions at once?

 

[Demystifier]

Well, then Bohr definitely wrote only about true things.

Except the Bohr model of atom (with the so called "old QM"), which is clear but not true.

 

[Zafa Pi]

What if I tell you that I have a theory that solves all these questions at once?

Oh sure, butter me up with something I won't be able to follow. I'm holding out for comprehension.
OK. let's see it, maybe it will work as a soporific.

 

[PeroK]

Is it just because of the existence of atoms, or because you don't think that the axiom of choice represents a physical choice?

I tend to view physics as finite, in the sense that any experiment only has a finite number of outcomes. The mathematics and theoretical physics extrapolates this to countable and uncountable infinities. A classical example is modelling a body as a continuous mass distribution, even though the physics is a large, finite number of particles.

In QM you can practically only carry out a finite number of measurements, so there is always a mathematical extrapolation to a continuous wave function defined on an uncountable set of points.

The extent to which the underlying reality is infinite is perhaps unknowable, as we will only ever have a finite set of data.

In particular, I can't see that the axiom of choice would be relevant in a physical situation.