I Quantum Immortality without MWI?

[akvadrako]

I don't see any advocates of QI talking about how human technological innovations are going to increase the human lifespan. That's why I specifically excluded that possibility in my previous posts.

Who are these advocates of QI? The only significant scientist I know of who seemed to give it credence was Everett, and that's only because of one second hand quote in a biography.

I do agree that what some people claim doesn't seem likely. Like David Lewis, who thought that you'll age normally then somehow escape death at the last moment.

The part about QI that does make sense (at least given the assumptions) is to say, at point X in the future, there will be some future versions of me in worlds that still exist and other worlds where I don't exist at all. And when X is 200 years, most of those surviving worlds will happen because of advances in technology.

 

[PeterDonis]

Who are these advocates of QI?

The ones discussed in the Wikipedia article linked to in the OP of this thread. (David Lewis, whom you mention, is one of them.)

 

[akvadrako]

The ones discussed in the Wikipedia article linked to in the OP of this thread. (David Lewis, whom you mention, is one of them.)

I think, based on discussions on that wiki talk page, that there are only two camps besides Everett. There are those that don't think MWI is real and those that don't think it implies QI. So there are not really advocates in the sense of people writing papers about how it would plausibly work.

 

[Physicuser]

"Ceased to experience" doesn't mean "ceased to exist". In a branch where you die, your dead body is still there, and still discernible from the live body in the other branch. So no, dying is a divergence. Experience is part of what exists, but not all of it; and indiscernibility has to take into account all of what exists.

That could be the fundamental question, and I am not sure... Objectively you die, but subjectively you are what you experience, so I don't know...
If the Principle of Indiscernibles is true, then, the next-second you and a Boltzmann Brain identical to him are the same person. And then, wouldn't this apply to a Boltzmann Brain experiencing having survived your death, so, from a subjective point of view, the same as if you had survived?

 

[PeterDonis]

If the Principle of Indiscernibles is true, then, the next-second you and a Boltzmann Brain identical to him are the same person.

No, they aren't, because a "person" is not a snapshot at one instant of time. A "person", as I have already described in previous posts, is a full sequence of experiences throughout an entire lifetime. A Boltzmann Brain is not. These two things are easily distinguishable.

 

[PeterDonis]

Objectively you die, but subjectively you are what you experience

We are talking about physics here, not philosophy or psychology. Yes, your physical body can no longer support having subjective, conscious experiences when you die. But your physical body is still a physical thing. It doesn't just stop existing if you stop having conscious experiences with it.

 

[Physicuser]

Despite some interesting remarks, unfortunately, it seems to me that some kind of Subjective Immortality is probably true, let's summarise and debate if there are flaws and try to debunk it.

I think, essentially this is required:

- Possiblity: it's possible to live indefinitely. There are some ways this could happen, not only through quantum miracles that keep you barely alive (Quantum Immortality), but medical advancement in life extension, crionics, or if physical continuity is not needed, Brain in a vat, Boltzmann brains, or Digital simulations (if this is possible)

- Infinites: the Infinite Monkeys Theorem, and the Poincaré Recurrence Theorem. All possible happens in an infinite universe. With current knowledge, the universe is most probable infinite in some way: if its shape is flat or hyperbolic, is infinite in space, and probably in time (Random fluctuations after the Heat Death, leading eventually to another Big Bang, or just infinites Boltzmann Brains); if spherical, it will collapse and probably, bounce again; if a 3-thorus, its cyclical... Even if it is finite, small and don't last forever, several mainstream theories imply a big or infinite multiverse (String Theory, MWI, Mathematical Universe...).

- Identity: the Principle of Identity of Indiscernibles. Conciousness is nothing special or unique, a person/brain exactly like you is you and have the same "conciousness".

So, if there are infinite "yous", and the universe is infinite, happening all possible, one way or another, one future version of you will survive, and he will be "you" with respect to "this-you" (and then, don't make sense ask who of them you will be, you are all, since they are different with respect each other, but not with you now).Objections:
- These means of immortality could fail: it's not clear if quantum effects can prevent death, if crionics works, if it's possible to simulate a person, etc.
- Infinite space/time does not necessarily imply that all possible happens.
- Conciousness and mind are not well known, it's not sure if the Principle of Identity applies to it, if another "you" is you, if it is required continuity of the body or experience, etc.

Let's see if this can be refuted.

 

[PeterDonis]

it's possible to live indefinitely

Physically, I think this is true, yes. I personally don't think it's possible by the "quantum miracle" route (because I don't think such "miracles" are actually possible), but it should be by technological advancement.

if physical continuity is not needed

I don't think this makes sense. A person is not a single snapshot at an instant of time. A person is a coherent sequence of experiences over a length of time. That requires physical continuity (although quite possibly not physical continuity in the sense of having a human brain like the ones we have now through the entire sequence of your personal experiences--technological advancement might make it possible to keep physical continuity of experience while changing the underlying substrate to something more reliable and less error prone than the current human brain).

All possible happens in an infinite universe.

Yes. This is one of the basic points of the Tegmark paper.

Conciousness is nothing special or unique, a person/brain exactly like you is you and have the same "conciousness".

This is true as long as you recognize how extremely strong the "exactly like" condition is. It requires the exact same entire sequence of experiences, which means the exact same entire sequence of physical events down to whatever level is required to ensure an identical sequence of experiences.

To put this another way: if it is possible for technological advancement to produce a future-infinite sequence of experiences that starts with the exact sequence of experiences that you have had up to now, then somewhere in the infinite multiverse there will be such a future-infinite sequence of experiences--a person who shares all of the experiences of "you" up to now. But that does not mean that you--the person here on Earth who is reading this post right now--are that person. The fact that there is some future-infinite sequence of physical events that instantiates a person whose experiences up to whatever age you are now are exactly the same as the ones you have had up to now, does not mean the sequence of physical events that underlie your experience here on Earth is such a future-infinite sequence.

In other words, even if there is an immortal person somewhere in the infinite multiverse who shares all of your experiences up to now, you don't know if that person is you, because "you" does not just mean the sequence of your experiences up to now: it means the entire sequence of experiences that the sequence of your experiences up to now, here on Earth, at this location in the multiverse, is the start of. And you don't know whether that sequence of experiences will be future-infinite or not. Nothing in Tegmark's paper or the Quantum Immortality literature can tell you that.

 

[Jarvis323]

Despite some interesting remarks, unfortunately, it seems to me that some kind of Subjective Immortality is probably true, let's summarise and debate if there are flaws and try to debunk it.

I think, essentially this is required:

- Possiblity: it's possible to live indefinitely. There are some ways this could happen, not only through quantum miracles that keep you barely alive (Quantum Immortality), but medical advancement in life extension, crionics, or if physical continuity is not needed, Brain in a vat, Boltzmann brains, or Digital simulations (if this is possible)

- Infinites: the Infinite Monkeys Theorem, and the Poincaré Recurrence Theorem. All possible happens in an infinite universe. With current knowledge, the universe is most probable infinite in some way: if its shape is flat or hyperbolic, is infinite in space, and probably in time (Random fluctuations after the Heat Death, leading eventually to another Big Bang, or just infinites Boltzmann Brains); if spherical, it will collapse and probably, bounce again; if a 3-thorus, its cyclical... Even if it is finite, small and don't last forever, several mainstream theories imply a big or infinite multiverse (String Theory, MWI, Mathematical Universe...).

- Identity: the Principle of Identity of Indiscernibles. Conciousness is nothing special or unique, a person/brain exactly like you is you and have the same "conciousness".

So, if there are infinite "yous", and the universe is infinite, happening all possible, one way or another, one future version of you will survive, and he will be "you" with respect to "this-you" (and then, don't make sense ask who of them you will be, you are all, since they are different with respect each other, but not with you now).Objections:
- These means of immortality could fail: it's not clear if quantum effects can prevent death, if crionics works, if it's possible to simulate a person, etc.
- Infinite space/time does not necessarily imply that all possible happens.
- Conciousness and mind are not well known, it's not sure if the Principle of Identity applies to it, if another "you" is you, if it is required continuity of the body or experience, etc.

Let's see if this can be refuted.

Here are some of my thoughts.

If you make the assumption that people are discrete and identified only by their discrete properties, then you don't necessarily have a model of consciousness that defines humans as conscious, but not rocks, or any discrete objects. So let's just simplify the problem to that of a rock. Maybe over time, it erodes, gets chipped at, things get cemented to it, maybe eventually it turns to sand, gets scattered around and mixed with other things, goes into a black hole. Where do we draw the line at it still being something that we can call an object that was that rock? If we say, after it splits in half, then we have to reconcile with the fact that you have also shed matter through time. Then there would be hardly any objectively defined continuation of you. Each iteration is someone else. If we say never, then you just need conservation of energy for you to go on forever as this you, even if that you has turned into gamma-rays.

If we include a definition of alive. Then we can say there are the yous that goes on forever, as energy, and there are the yous that live forever. But the you-ness we've defined doesn't distinguish the living you from the dead you. They are either both you or neither is.

If it's by assumption in the first place that we guarantee the discrete you will go on in a living form, then I guess that's all there is to say about an indefinitely surviving/living branch. It will be you as much as any other branch is you, including those that have long since mixed back into the environment.

So I guess in my opinion, it would be more interesting if there were some more special definition of consciousness and youness.

 

[PeterDonis]

it would be more interesting if there were some more special definition of consciousness and youness

This is the same general point I was trying to get at in the latter part of post #58, about how strong the "exactly like" condition is.

 

[votingmachine]

...

If the universe is infinite in space or time, or there are an infinite number of universes like ours (several mainstream theories imply it), is supposed that all possible happens, so there are infinite versions of you out there, and some of them will scape death miraculously.

There are different sizes to infinity. For instance is there ever an instance in all those infinities where you enumerate all the decimals of pi?

I am inclined to disbelieve the MW interpretation. But if you take that as a supposition, you cannot just blindly state all things must happen. There are things that cannot happen, like calculating every digit of pi.

This reminds me of the claims that the arrangement of air molecules in a room could be all on the left half, with the right half a vacuum, or some other highly improbable thing. The arrangement is one that can be considered in the infinite number of arrangements of the individual molecules and their individual properties.

Not all infinitely large sets are the same size. The set of Many-Worlds is infinite. But is still much smaller than the set of Imaginary-Many-Worlds (again just imagine calculating the infinite number of irrational numbers to completion). (Is there one with an infinite number of monkeys, all with typewriters, producing Shakespeare's plays flawlessly?)

 

[PeterDonis]

is there ever an instance in all those infinities where you enumerate all the decimals of pi?

If the universe goes on forever, then yes, in principle there would be.

There are things that cannot happen if the universe only exists for a finite time, like calculating every digit of pi.

See the insert in bold in the quote above.

The set of Many-Worlds is infinite. But is still much smaller than the set of Imaginary-Many-Worlds

What is this "set of Imaginary-Many-Worlds"? What physical theory is it based on?

 

[PeroK]

- Infinites: the Infinite Monkeys Theorem,
Let's see if this can be refuted.

The infinite monkey theorem has been refuted. There was a zoo that gave a monkey a typewriter. It typed out a few characters, got bored and defecated on the typewriter. No Shakespeare ever came out.

https://www.theguardian.com/uk/2003/may/09/science.arts

 

[PeroK]

Objections:
- Infinite space/time does not necessarily imply that all possible happens.

Here's an idea. Let's get rid of the monkey and have a typewriter produce the complete works of Shakespeare purely by "quantum fluctuations".

Somewhere in the infinite universe, there must be an old-fashioned typewriter producing the complete works of Shakespeare at normal typing speed purely by quantum fluctuations.

One possible approach to analysing this is to ask what we mean by "happens". In QM we can only say what happens as a result of a measurement. You can't say that an electron "must be somewhere"; you have to say that if you look for the electron you will find it somewhere.

You could apply this principle to some extent to these statements about what happens in an infinite universe: you have to devise an experiment to look for such a typewriter. You can't claim that such a typewriter exists until have a viable experiment to look for one. And, something like "look at the whole universe at once" is not a viable experiment.

And, if we have any sort of ultimate physical constraints on how much we can do in a given time, then we have a maximum finite probability of finding such a typewriter (in the lifetime of the universe). And, of course, that probability would be extremely small (*).

You end up with something like: given the optimal search capability within the laws of physics, the probability of finding a Boltzmann Brain or a "magic" typewriter is $p$, where $p$ is very small. And, you would intepret that as being the maximum probability that there "is" such a thing. As opposed to concusing that an infinitude of such things "exists", you conclude that the overwhelmingly probability is that none exist in any meaningful experimental sense.

I'd be interested if anyone has explored this idea, as an antedote to the "everything must happen" ideas.

(*) As an example, suppose every atom in the observable universe could be made into a computer that generates 130,000 random characters every Planck time and this ran for the lifetime of the universe. Then, the probability of any of those computers ever randomly producing Hamlet (130,000 characters) is still almost zero. So, there appear to be basic practicalities in even simulating these rare events. In other words, you run the best simulation of the universe that you can and ask: did a Bolzmann Brain evolve. The answer is not only "no", but that nothing evolved that was remarkable in any macroscopic sense.

 

[Jarvis323]

If MWI is correct, I could set up a machine that generates binary strings based on quantum fluctuations, and interpret them as ASCII. Just by having done that, it would mean that some branches of me would watch the machine print out Hamlet on repeat over and over. Another would see complete proofs of long standing problems in mathematics. Others would see blueprints for advanced technologies. Some would see this exact thread. Some would see detailed instructions on how to develop the most advanced possible technology that could be developed to extend a persons life. Others would see messages telling to go and get lotto tickets with the winning numbers. One would appear to think they were you, and know things only you would know, and appear to be able to communicate with you.

I guess if you really want some "you" to do all of these things and more, and you believe in MWI, then you might want to set such a device up and watch it for a while.

 

[akvadrako]

This is true as long as you recognize how extremely strong the "exactly like" condition is. It requires the exact same entire sequence of experiences, which means the exact same entire sequence of physical events down to whatever level is required to ensure an identical sequence of experiences.

To put this another way: if it is possible for technological advancement to produce a future-infinite sequence of experiences that starts with the exact sequence of experiences that you have had up to now, then somewhere in the infinite multiverse there will be such a future-infinite sequence of experiences--a person who shares all of the experiences of "you" up to now. But that does not mean that you--the person here on Earth who is reading this post right now--are that person. The fact that there is some future-infinite sequence of physical events that instantiates a person whose experiences up to whatever age you are now are exactly the same as the ones you have had up to now, does not mean the sequence of physical events that underlie your experience here on Earth is such a future-infinite sequence.

I don't think the criteria is that strong and maybe in the next few centuries we'll be able to test it with experiments on AI or maybe even people. We could copy a brain, even a rough copy, and ask if it feels like a continuation of the original. The more essential elements copied and the more similar the body, probably the more it'll feel like the original.

Requiring an exact copy is too much; people are not even exact copies of themselves from moment to moment. Our memories change and our perspectives of them change. If you change someone's body or situation drastically, that's also enough to feel like someone else. Consciousness can also be discontinuous, say if the brain is shutdown for a while due to extreme cold.

I suppose the deeper question is: is there anything more to the expectation of a future experience than the existence (in all of reality) of an entity feeling like it's a future version of you now.

 

[PeroK]

If MWI is correct, I could set up a machine that generates binary strings based on quantum fluctuations, and interpret them as ASCII. Just by having done that, it would mean that some branches of me would watch the machine print out Hamlet on repeat over and over.

Of course you couldn't! That's the point. You have no capacity to process an infinite amount of data. And, the amount of data you need to collate to see Hamlet appear even once involves processing something like $100^{130,000}$ bytes of data, which you cannot do.

 

[entropy1]

Don't we have to be careful invoking infinities? Like the hotel that accommodates an infinite number of guests and that sort? Anything may be possible!

 

[PeroK]

Don't we have to be careful invoking infinities? Like the hotel that accommodates an infinite number of guests and that sort? Anything may be possible!

I agree. Hilbert's Hotel is well-defined mathematically, but it's at least unclear whether one could ever be built, and it may be physically impossible. Until such time as someone can give a plausible argument for how one might build Hilbert's Hotel, then it's meaningless to talk about it as something physical.

It's not enough, IMHO, to wave your arms and say "infinite universe" or "MWI". If someone says that somewhere in Hilbert's Hotel there is a monkey who has just randomly typed Hamlet, then that's a physically meaningless statement, IMO.

If you have a computer in every room that produces 130,000 characters at random, then mathematically there are an infinite number of rooms where those characters are precisely the full play Hamlet. That's a mathematical result that is not physically meaningful.

 

[votingmachine]

What is this "set of Imaginary-Many-Worlds"? What physical theory is it based on?

The two things I was thinking on were the sizes of infinite sets and Godel's incompleteness theorem.

The set of irrational numbers is infinite, but larger than the set of rational numbers. There are more irrational numbers than rational numbers, even though there are an infinite amount of both. If there is an infinite amount of time that allows one to conjecture it is sufficient to enumerate the rational numbers, it is insufficient to enumerate the irrational numbers.

Godel's incompleteness theorem is often hand-waved with the idea that one can take the set of all the complete and consistent things that follow from a mathematical system, that set is incomplete. I was doing a similar "hand-waving" statement that the set of all possible universes created by splitting universes at every quantum event (all outcomes happen) leaves out the impossible ones.

So if I consider an atom as a particle in a box, there are allowed solutions and unallowed solutions. Yet I can IMAGINE unallowed ones. I can imagine the electron disappears and never comes back.

That is "Hand-waving". But the underlying principle is still that infinite sets are not all the same size. If one takes the set of all possible "Many-Worlds" it is not definitive that much larger infinite sets are likely. Especially the ones based on wishful thinking.

EDIT: Another hand-wave: MWI is based on a quantum mechanics view of the things happening in the universe. It can never include a universe that is NOT based on quantum mechanics ... or a Newtonian one with faster than light rockets.

 

[Physicuser]

he will be "you" with respect to "this-you" (and then, don't make sense ask who of them you will be, you are all, since they are different with respect each other, but not with you now).

I am having troubles with this reasoning. It's seems that if you say "you will win the lottery in 2030", is true, but then this apply too if you say "next second you will tunnel into the moon", but well, you are still here...

 

[PeterDonis]

people are not even exact copies of themselves from moment to moment

You're misunderstanding my definition of a "person". As I have already emphasized, a person is not a snapshot at a single instant of time. A person is an entire sequence of experiences. Obviously for a sequence of experiences to be instantiated by any physical system, the state of that physical system must change from moment to moment. But to think of that as "the person changing" is a misunderstanding. The sequence of physical experiences, instantiated by a physical system that is changing from moment to moment to instantiate those experiences, is the person.

is there anything more to the expectation of a future experience than the existence (in all of reality) of an entity feeling like it's a future version of you now.

Yes: the question is whether the particular person here on Earth is that entity--whether the sequence of experiences that is going on here on Earth is the one that is going to include that future experience at some point. The fact that some such sequence exists somewhere in the infinite multiverse does not prove that the particular sequence here on Earth is that sequence.

 

[PeterDonis]

The two things I was thinking on were the sizes of infinite sets and Godel's incompleteness theorem.

Which are mathematical things, not physical things. We are not talking about abstract mathematics in this thread. We are talking about our actual universe and what is possible within it. So it's not enough to wave your hands and say "mathematically we know there are infinite sets with different cardinalities". Yes, we know that. But that says nothing about the cardinalities of the actual infinite sets (if there are any) that appear in our physical models, which is what we are talking about in this thread.

I was doing a similar "hand-waving" statement that the set of all possible universes created by splitting universes at every quantum event (all outcomes happen) leaves out the impossible ones.

Um, this isn't a "hand-waving statement", it's a tautology: obviously the set of possible universes does not include impossible universes.

Another hand-wave: MWI is based on a quantum mechanics view of the things happening in the universe. It can never include a universe that is NOT based on quantum mechanics

This is not a hand-wave either: it's another obvious statement that contributes nothing useful to the discussion in this thread.

If you don't have anything useful to contribute to the discussion in this thread, please refrain from further posting.

 

[PeterDonis]

I am having troubles with this reasoning.

Because you're not thinking through the implications of what "you" actually means. I suggest re-reading my post #58 in response to you again, particularly the last part of it. (I reiterated some of the same points in post #72.)

 

[Physicuser]

Because you're not thinking through the implications of what "you" actually means. I suggest re-reading my post #58 in response to you again, particularly the last part of it. (I reiterated some of the same points in post #72.)

It seems a good point, thanks.

 

[Jarvis323]

Of course you couldn't! That's the point. You have no capacity to process an infinite amount of data. And, the amount of data you need to collate to see Hamlet appear even once involves processing something like $100^{130,000}$ bytes of data, which you cannot do.

But there would be many worlds/yous. Every world would have a you, and a different message, and all of the possible messages would be seen by some you. One of them would see Hamlet.

This is one reason why MWI is disregarded by some people, because it implies absurdly statistically unlikely outcomes in some worlds.

 

[PeterDonis]

there would be many worlds/yous

Please, please be clear about exactly what you mean by "you". I have posted repeatedly about this already.

You, here and now on Earth, represent an initial portion (from your first experience up to now) of a particular entire sequence of human experiences--a particular person. But you, here and now on Earth, do not know exactly which entire sequence of experiences you are--which entire sequence the sequence of you here on Earth up to now is an initial portion of.

If Tegmark's reasoning is correct, whichever entire sequence of experiences your experience here on Earth up to now is an initial portion of, there are many other entire sequences of experiences elsewhere in the infinite multiverse that are identical. But that statement tells you nothing about which entire sequence of experiences your experience here on Earth up to now is an intial portion of. So it tells you nothing about what future experiences you, here and now on Earth, you should expect. Whichever future experiences you end up having, yes, there will be many other sequences of experiences, realized elsewhere in the infinite multiverse, that are the same; but that tells you nothing about which future experiences those will be.

In other words, there are many different possible entire sequences of experiences, all of which start with the same initial portion as your experience here on Earth up to now. Only one of those sequences is the one being instantiated here on Earth. So the term "you" is ambiguous: it can refer to just the particular entire sequence of experiences being instantiated here on Earth, or it can refer to the set of all possible entire sequences of experiences that have the same initial portion as the one being instantiated here on Earth--your experience here on Earth up to now. You seem to be using it with the latter meaning, but the latter meaning doesn't say anything about what the you here on Earth will experience. It is perfectly possible to formulate a notion of "probability" in which it is meaningful to say that the probability is absurdly tiny that you, here on Earth, will see Hamlet emerge from a series of random quantum fluctuations. Which is all we can actually establish from experiment.

 

[Jarvis323]

Please, please be clear about exactly what you mean by "you". I have posted repeatedly about this already.

You, here and now on Earth, represent an initial portion (from your first experience up to now) of a particular entire sequence of human experiences--a particular person. But you, here and now on Earth, do not know exactly which entire sequence of experiences you are--which entire sequence the sequence of you here on Earth up to now is an initial portion of.

If Tegmark's reasoning is correct, whichever entire sequence of experiences your experience here on Earth up to now is an initial portion of, there are many other entire sequences of experiences elsewhere in the infinite multiverse that are identical. But that statement tells you nothing about which entire sequence of experiences your experience here on Earth up to now is an intial portion of. So it tells you nothing about what future experiences you, here and now on Earth, you should expect. Whichever future experiences you end up having, yes, there will be many other sequences of experiences, realized elsewhere in the infinite multiverse, that are the same; but that tells you nothing about which future experiences those will be.

In other words, there are many different possible entire sequences of experiences, all of which start with the same initial portion as your experience here on Earth up to now. Only one of those sequences is the one being instantiated here on Earth. So the term "you" is ambiguous: it can refer to just the particular entire sequence of experiences being instantiated here on Earth, or it can refer to the set of all possible entire sequences of experiences that have the same initial portion as the one being instantiated here on Earth--your experience here on Earth up to now. You seem to be using it with the latter meaning, but the latter meaning doesn't say anything about what the you here on Earth will experience. It is perfectly possible to formulate a notion of "probability" in which it is meaningful to say that the probability is absurdly tiny that you, here on Earth, will see Hamlet emerge from a series of random quantum fluctuations. Which is all we can actually establish from experiment.

This is all true. But one being that shares your prefix up to this point, will experience a chain of experiences that includes setting up a device and seeing Hamlet printed. In fact one will experience being in a reality where experimentally, all quantum random number generators always print Hamlet and nothing else. Being one who experiences that will be absurdly unlikely. But it will happen according to MWI. For them, experimentally, they would appear to live in a quantum Hamlet universe.

 

[PeterDonis]

one being that shares your prefix up to this point, will experience a chain of experiences that includes setting up a device and seeing Hamlet printed

Yes. But among the set of all beings that share the same prefix (good shorthand term, btw!), only a very tiny fraction will have that experience.

one will experience being in a reality where experimentally, all quantum random number generators always print Hamlet and nothing else

Yes, but this will be a much, much tinier fraction than the subset above.

it will happen according to MWI. For them, experimentally, they would appear to live in a quantum Hamlet universe

Yes, this is one argument for being skeptical that the MWI is true. It probably needs to be discussed in a separate thread if you want to go into it in more detail, since this thread is supposed to be about QI without the MWI.

 

[votingmachine]

Which are mathematical things, not physical things. We are not talking about abstract mathematics in this thread. We are talking about our actual universe and what is possible within it. So it's not enough to wave your hands and say "mathematically we know there are infinite sets with different cardinalities". Yes, we know that. But that says nothing about the cardinalities of the actual infinite sets (if there are any) that appear in our physical models, which is what we are talking about in this thread.

I thought the original question was precisely about whether everything imaginable happens in a MWI. Maybe I focused on the wrong part:

... a person like you in another galaxy or a brain that popped out in the middle of space, so even if there is no causal connection between them, there is a subjective sensation of continuity...

I'm not sure of the cardinality of the set of MW, but it seems smaller than the set of MW we can imagine. And that might be impossible. I'm not sure why a brain is popping up in the middle of space, with the exact conscious history of another brain, on earth. I did mention impossible things because that seemed impossible.

 

[PeterDonis]

I thought the original question was precisely about whether everything imaginable happens in a MWI.

Please read the thread title. The OP does mention the MWI, but only to describe where the "quantum immortality" idea originally came from. The thread is specifically about whether something similar is possible if the MWI is not true.

Maybe I focused on the wrong part:

What the OP described there does not require the MWI. In fact, one of the rather counterintuitive points made in the Tegmark paper referenced earlier is that, in a spatially infinite universe with inflation at the start, anything that would happen in some branch under the MWI will also happen in some Hubble volume of the spatially infinite universe on a single-world interpretation of QM. The latter kind of scenario is what we are discussing in this thread.

 

[PeterDonis]

I'm not sure of the cardinality of the set of MW, but it seems smaller than the set of MW we can imagine.

This is off topic. Please start a separate thread if you want to discuss this.

 

[votingmachine]

What the OP described there does not require the MWI. In fact, one of the rather counterintuitive points made in the Tegmark paper referenced earlier is that, in a spatially infinite universe with inflation at the start, anything that would happen in some branch under the MWI will also happen in some Hubble volume of the spatially infinite universe on a single-world interpretation of QM. The latter kind of scenario is what we are discussing in this thread.

I see the link and paper now. But doesn't it also make the same point that I am after in discussing the cardinality? The Level-1 multiverse is a subset of the Level-4 multiverse. The cardinality of the two is different.

I see that an infinite spatial universe is likely to have infinitely many variations of 14 billion light-year spheres. But I think that infinite set of 14 billion light year spheres is incomplete. The cardinality is lower. There should be an infinite number of those 14 billion light year spheres with 1 hydrogen atom in them (placed at an infinite number of positions), Each with the atom somewhere slightly different. And another infinite set with 2 helium atoms.

If the cardinalities are different then we can say some things are not in there. Level-3 variations are not found in the Level-1 set.

"Level I: A generic prediction of cosmological inflation is an infinite “ergodic” space, which contains Hubble volumes realizing all initial conditions."

There needs to be proof that the infinite set of initial conditions can be mapped one-to-one to infinite space. Perhaps that proof is in one of the references, but none is presented in that paper.

 

[PeterDonis]

The Level-1 multiverse is a subset of the Level-4 multiverse.

Yes, but this does not prove that the cardinality of the latter is greater than the cardinality of the former. Remember that we are dealing with infinite sets: an infinite set can have a proper subset that has the same cardinality. (In fact that's the definition of an infinite set.)

 

[votingmachine]

Yes, but this does not prove that the cardinality of the latter is greater than the cardinality of the former. Remember that we are dealing with infinite sets: an infinite set can have a proper subset that has the same cardinality. (In fact that's the definition of an infinite set.)

True.

But I also find it difficult to swallow that a universe is determined by the initial conditions ... that seems to contradict the results we see in this section of the Multiverse. But I see the parallel between the "unitary" part of MWI and that of determinism set by initial conditions. And thus why it is possible to consider the two functionally equivalent.

It does seem like that requires hidden deterministic variables ... and I cannot resolve that with the contradiction of that assumption seen in Bell's Theorem experiments. But I suppose we could anthropically live in a subsector where the results of Bell experiments are confusing. Although I would argue that to be an identical me, there has to be that set of experimental data.

 

[PeterDonis]

I also find it difficult to swallow that a universe is determined by the initial conditions ... that seems to contradict the results we see in this section of the Multiverse.

How so?

 

[votingmachine]

How so?

If there is an identical me in an identical multiverse measuring the identical electron present, and I measure the spin in one and the position in the other then the spin and position are both knowable with infinite precision. I don't have to presuppose entanglement, I merely have to suppose multiverse identity to that moment.

Every experiment with entangled things says that the two conjugate variables CAN NEVER be known with infinite precision. The identical multiverses are Einstein's Princes.

You either have to hold that conjugate variables are knowable, or unknowable. The experimental results in this multiverse are only consistent with them being unknowable.

Put another way, the two variables can be shown to not coexist at a level beyond the uncertainty principle. But the existence of Multiverses creates a situation where even though a singular I does not know the two, the two measurements exist, on what is the same particle.

Or if there is FTL hidden variable communication, I would notice that the particle was measured for spin, and therefore, my measurement was impossible. Maybe FTL hidden variable swapping works ... it eludes me how though. The two particles are merely identical, not entangled.

 

[PeterDonis]

If there is an identical me in an identical multiverse measuring the identical electron present, and I measure the spin in one and the position in the other

Inconsistent. If the two "mes" make different measurements on the electron, they're not identical.

The rest of your post just builds on this initial error.

 

[votingmachine]

Inconsistent. If the two "mes" make different measurements on the electron, they're not identical.

The rest of your post just builds on this initial error.

Hmm. I'm stuck in a loop on that response. Of course they are not identical once they are measured, but they were before the measurement. And that seems to be the EPR objection to QM completeness.

But I'll have to think on it. It seems a circular argument.

Let me try the same thing stated another way:

6 identical Multiverses where I have entangled pairs of photons headed for the usual ABC detectors. Now the multiverses diverge and I put all 6 possible pairs of settings (AA, AB, AC, BB, BC, CC). The results of those measurements of the same pair create a requirement for a complete instruction set. And a complete hidden instruction set is incompatible with the experimental results.

That may be the same issue ... once the pairs are measured, they are non-identical. Now I can't KNOW that there was a complete instruction set, unless another multiverse has me reincarnated with the previous 6 bits of knowledge.

I could be being anthropic though ... Tegmark does warn against that trap.

 

[PeterDonis]

Of course they are not identical once they are measured, but they were before the measurement.

So what?

that seems to be the EPR objection to QM completeness

No, it isn't. The EPR objection has nothing to do with what you are saying.

The results of those measurements of the same pair create a requirement for a complete instruction set.

No, they don't. The fact that results occur for all 6 pairs of settings does not mean all of those results were predetermined.

a complete hidden instruction set is incompatible with the experimental results.

Only if it obeys Bell's locality condition.

 

[PeroK]

This is all true. But one being that shares your prefix up to this point, will experience a chain of experiences that includes setting up a device and seeing Hamlet printed. In fact one will experience being in a reality where experimentally, all quantum random number generators always print Hamlet and nothing else. Being one who experiences that will be absurdly unlikely. But it will happen according to MWI. For them, experimentally, they would appear to live in a quantum Hamlet universe.

Without MWI, that's true of our universe: that a random character generator could produce Hamlet, but it is absurdly unlikely. And we can run an experiment to confirm/justify that claim.

You claim that if MWI is true then there must be a random character generator somewhere that generates Hamlet (and nothing but Hamlet).

What I ask is at least a description of an experiment that would test that claim. If you cannot provide at least an outline of how you would test that (to see whether it's true of not), then I claim that statement is physically meaningless and metaphysics, rather than physics.

We can all wave our hands and say there must be this and there must be that, but unless you can propose an experiment to confirm what you're saying, then it's not physics.

Believing MWI doesn't give anyone the right to abandon the principles of confirming claims by experimental evidence. This is my challenge to all your claims: that you are using a blind belief in MWI to avoid actually thinking about the universe from an experimental point of view and claiming things to be true that cannot be confirmed experimentally.

Further, I suggest that if MWI is true and even if you could somehow investigate more than one branch of the wavefunction, then (in any experiment constrained by the speed of light, and the lifetime of the universe) the chance of finding such a machine is still absurdly unlikely. So, from a physics standpoint it is still absurdly unlikely that you can show such a thing to exist.

 

[PeterDonis]

You claim that if MWI is true then there must be a random character generator somewhere that generates Hamlet (and nothing but Hamlet).

What I ask is at least a description of an experiment that would test that claim.

If you agree that without the MWI, a random character generator would have an extremely tiny, but not zero, probability of producing Hamlet and nothing but Hamlet, then it must be the case, because all QM interpretations use the same underlying math, that in the MWI, there would be a branch in which a random character generator produced Hamlet and nothing but Hamlet. You don't need an experiment to test that.

Bear in mind that the MWI is an interpretation of QM. That means it makes all of the same experimental predictions as any other interpretation of QM, including whichever one you are using to make the claim that without the MWI, there would be an extremely tiny, but not zero, probability of a random character generator producing Hamlet and nothing but Hamlet. So you can't distinguish between those two interpretations by any experimental test. All you can do is observe that they both use the same underlying math; the only difference between "there is an extremely tiny but nonzero probability of X occurring" and "there will be a branch in which X occurs" is which QM interpretation you choose.

 

[PeroK]

If you agree that without the MWI, a random character generator would have an extremely tiny, but not zero, probability of producing Hamlet and nothing but Hamlet, then it must be the case, because all QM interpretations use the same underlying math, that in the MWI, there would be a branch in which a random character generator produced Hamlet and nothing but Hamlet. You don't need an experiment to test that.

The adoption of the idea where we do not need experimental evidence for these claims, I suggest, is allowing metaphysical wool to be pulled over our eyes.

I'm drawing a distinction between the mathematics and the physics. Mathematically, you have an infinite sequence of worlds. But, once you introduce the need for experimental confirmation of these claims, you can't process an infinite sequence. I would like to insist that:

Everything that is claimed to exist has at least a theoretically plausible experiment that could find it.

This would ultimately allow us to assign some sort of probabilities to events in MWI according to the maximum practical probability of finding it - given certain fundamental constraints, such as the speed of light, the amount of available energy in the observable universe and the lifetime of the universe.

In other words: if we hypothetically dedicated all the available resources in the observable universe for the lifetime of the universe to finding out Hamlet machine, then the probability of finding it is still absurdly small. And that would allow us to say - with some well-defined physical meaning - that's it's absurdly unlikley that there is one. And to claim the definite existence of something we will (almost certainly) never find is metaphysics.

In a nutshell, my argument against blindly accepting the existence of everything that MWI may produce is to impose at least some measure of experimental verifiability. You could argue with my methodology, but I suggest some experimental methodology (that goes beyond hand waving) is necessary for us to be discussing physics at all.

 

[Jarvis323]

What I ask is at least a description of an experiment that would test that claim. If you cannot provide at least an outline of how you would test that (to see whether it's true of not), then I claim that statement is physically meaningless and metaphysics, rather than physics.

We can all wave our hands and say there must be this and there must be that, but unless you can propose an experiment to confirm what you're saying, then it's not physics.

If this is true, then quantum interpretations are not in the realm of physics.

Believing MWI doesn't give anyone the right to abandon the principles of confirming claims by experimental evidence. This is my challenge to all your claims: that you are using a blind belief in MWI to avoid actually thinking about the universe from an experimental point of view and claiming things to be true that cannot be confirmed experimentally.

Who has said they believe in MWI? Personally, I don't.

Further, I suggest that if MWI is true and even if you could somehow investigate more than one branch of the wavefunction, then (in any experiment constrained by the speed of light, and the lifetime of the universe) the chance of finding such a machine is still absurdly unlikely. So, from a physics standpoint it is still absurdly unlikely that you can show such a thing to exist.

If MWI is true, then the mathematics implies Hamlet machines. If what it implies is false, then MWI would have been false in the first place. We've assumed it was true as a thought experiment already.

 

[Jarvis323]

In other words: if we hypothetically dedicated all the available resources in the observable universe for the lifetime of the universe to finding out Hamlet machine, then the probability of finding it is still absurdly small. And that would allow us to say - with some well-defined physical meaning - that's it's absurdly unlikley that there is one.

You can argue that it's not worth discussing since it's just mathematics we're discussing. But the argument you've given is self contradictory. If we discuss mathematics, then we should be consistent.

If experimentally you find it extremely unlikely for a Hamlet machine to exist, that is fine.

But if you claim that a world where all quantum random number generators are Hamelet machines doesn't exist, and you've assumed many worlds interpretation is true, then all you've done is contradict your assumption.

In other words, even if we do some hand waiving and assume you could disprove a Hamlet machine exists, then all you could hope to do is disprove the assumption (MWI).

Physics is based on math. If we can't discuss the math itself (because in your opinion mathematics is just hand waiving), then we can't do any kind of physics in the first place. In other words, you're claiming physics isn't physics.

 

[akvadrako]

In a nutshell, my argument against blindly accepting the existence of everything that MWI may produce is to impose at least some measure of experimental verifiability. You could argue with my methodology, but I suggest some experimental methodology (that goes beyond hand waving) is necessary for us to be discussing physics at all.

Testing MWI might be possible if it implies QI and the other interpretations don't. QI can be tested because it assigns different probabilities to "living to 200" and "living to 1M" than there not being QI. So each time you find yourself living longer than you expected, seemingly by being lucky to be in the right world, it should increase your credence of QI and hence of MWI.

 

[PeroK]

If this is true, then quantum interpretations are not in the realm of physics.

I think it's generally accepted that taking an interpretation literally is metaphysical. But, an interpretation is a practical way of making sense of the theory.

In the case of MWI, there is a possibility that it might in future be experimentally verifiable.

Who has said they believe in MWI? Personally, I don't.

Okay, fair enough.

If MWI is true, then the mathematics implies it. If what it implies is false, then MWI would have been false in the first place. We've assumed it was true as a thought experiment already.

I'm saying you still need to make physical sense of the mathematics. In a way, I'm defending MWI by saying you can have it as a mathematical framework and then impose an experimental methodology which means you can (in a physically meaningful way) assign probabilities to things - in terms of some sort of maximum probability of such a things ever being "found" - assuming you can simulate looking through as many worlds as possible, for example.

Alternatively, you could take MWI with a finite branching - that's perhaps a simpler way to achieve the same thing.

 

[PeroK]

(because in your opinion mathematics is just hand waiving), then we can't do any kind of physics in the first place. In other words, you're claiming physics isn't physics.

There's no way to argue with such a nonsensical misrepresentation of what I've said.

 

[Jarvis323]

There's no way to argue with such a nonsensical misrepresentation of what I've said.

I apologize. I am coming around to understanding your point better I think. If I'm not mistaken, you're disagreement seems to be in making the assumption.

 

[mattt]

As others pointed out earlier, the existence of a Hamlet machine does not depend on the many-worlds interpretation of QM.

In the many-worlds interpretation of quantum mechanics, it exists as a branch of the wave function of the universe, whereas in type 1 scenario of Tegmark, it exists in some bubble.

In both cases, the probability of finding it experimentally, it's almost zero.

On the other hand, I see no problem in discussing about what the mathematics of quantum mechanics imply.