I Many Worlds Interpretation and Coffee

[vanhees71]

MWI is another interpretation of QT not a different theory. As far as observable facts are concerned all interpretations lead to the same conclusions as minimally interpreted QT.

 

[phillovix]

I would like to try another angle on trying to find an answer to my initial query, that I understand may not of been worded too well.

Say I pick up a salt shaker and keep going between almost shaking it and not shaking it, without actually shaking it from my perspective, however being very close in the decision to shake it.
Say I keep that up for an hour and am willing to flip a coin on keeping that for another hour and so on.
Say the coin flip dictates that I stop, and I stop.

Does MWI imply that the salt shaker was shook, somewhere? At what point does it become impossible that the salt shaker was shook as a result of that game? When I elected to stop, or when death kicks in?
As stated in an earlier post, is freewill factored into calculations? Or is it being based on a purely mechanical deterministic view that everything that can happens, happens and we are just passengers observing whatever sequences we observe.

Kind regards,
Phill <3

 

[PeterDonis]

Does MWI imply that the salt shaker was shook, somewhere?

It's actually very hard to properly formulate a scenario such that you can even apply the MWI, because we are so used to talking in terms of only one thing happening. To even admit the MWI as a possibility, you would have to formulate your scenario something like this:

Say I have a salt shaker in my hand, and there is some quantum-level uncertainty in whatever part of my brain is determining whether I will shake it or not. Then it is possible that I shake it, and possible that I don't. If the MWI is true, both of these possibilities are realized. If a collapse interpretation of QM is true, only one of them is. But both interpretations make the same predictions about what I will observe; both, for example, will predict that, if my brain ends up determining that I shake the shaker, then others around me will observe it being shaken; whereas if my brain ends up determining that I do not shake the shaker, then others around me will observe it not being shaken. If a collapse interpretation is true, then, again, only one of these possibilities is realized; but if the MWI is true, both of them are.

is freewill factored into calculations?

As far as physics is concerned, "free will" is just a physical process, so of course it is factored into calculations, just like any other physical process.

Or is it being based on a purely mechanical deterministic view that everything that can happens, happens and we are just passengers observing whatever sequences we observe

As far as physics is concerned, this is not a different way things could be from us having free will; "free will" and "everything that can happen, happens" are just two different descriptions of the same reality. If the MWI is true, anything that it is physically possible for you to freely choose to do, you do freely choose to do in some branch of the wave function.

 

[phillovix]

It's actually very hard to properly formulate a scenario such that you can even apply the MWI, because we are so used to talking in terms of only one thing happening. To even admit the MWI as a possibility, you would have to formulate your scenario something like this:

Say I have a salt shaker in my hand, and there is some quantum-level uncertainty in whatever part of my brain is determining whether I will shake it or not. Then it is possible that I shake it, and possible that I don't. If the MWI is true, both of these possibilities are realized. If a collapse interpretation of QM is true, only one of them is. But both interpretations make the same predictions about what I will observe; both, for example, will predict that, if my brain ends up determining that I shake the shaker, then others around me will observe it being shaken; whereas if my brain ends up determining that I do not shake the shaker, then others around me will observe it not being shaken. If a collapse interpretation is true, then, again, only one of these possibilities is realized; but if the MWI is true, both of them are.
As far as physics is concerned, "free will" is just a physical process, so of course it is factored into calculations, just like any other physical process.
As far as physics is concerned, this is not a different way things could be from us having free will; "free will" and "everything that can happen, happens" are just two different descriptions of the same reality. If the MWI is true, anything that it is physically possible for you to freely choose to do, you do freely choose to do in some branch of the wave function.

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.
Even when factoring in a multiverse, I do not think there is an infinite amount of universes. Probably a greater number of them than I can actively fathom, still, not an infinite amount though.

Kind regards,
Phillip
<3

 

[PeterDonis]

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.
Even when factoring in a multiverse, I do not think there is an infinite amount of universes. Probably a greater number of them than I can actively fathom, still, not an infinite amount though.

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".

 

[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?