Whoops! Misread this as "Quantum Immorality". Now there's a metaphysical topic worth pursuing! :nerd:

Whoops! Misread this as "Quantum Immorality". Now there's a metaphysical topic worth pursuing! :nerd: — jgill

Good one! You can misbehave all you like because in some other world you were Godly.

'Quantum immortality'). — Philosophuser

I would not believe a word anyone writes about the subject unless they put their money where their mouth is and kill themselves. Since no sane person would do that, the idea stands refuted. Even the people who claim to believe it, don't. Maybe that nutball in Nashville was testing out the theory, eh what? They say he believed in the lizard people. Compared to QI/MWI, that's practically sane.

QI is just wrong. The only you is the one in this world. The other ones may be identical copies, but they are not you. It's like forking a process in a Unix system. You get a copy identical in every way to the original; but it's a distinct process that has its own future after the moment of the fork. Even in MWI there is only one of you, the one in this world. The other one has the identical state as you (exact same configuration of atoms, identical life experiences, memories, thoughts) up to the moment where its future diverges from yours. To put it in theological terms, each "copy" has its own soul, if that metaphor helps to make my point more clear.

Two configurations of atoms may be identical, but they are not the same person. They're two distinct individuals that happen to have the same configuration up to some moment of time. Relates to the transporter problem. You die at one end and a copy with your memories and experiences is created at the other; but they are not the same individual. You can see that just by imagining a nondestructive scan at the sending end, resulting in two copies. Two souls identical in experience and mentality up to the moment of cloning, but with distinct diverging histories thereafter.

Whoops! Misread this as "Quantum Immorality". Now there's a metaphysical topic worth pursuing! :nerd: — jgill

Sure, like the theory that Bose-Einstein condensation allows for multiple universes to emerge together as highly correlated multi-excitations of the inflaton field, allowing for big bangs to occur simultaneously and evolve in perfect unison such that we are not inhabitants not of one universe but of many.

I call it the gang bang theory.

Taking MWI seriously, branching occurs upon measurement of a quantum system in a superposition of states corresponding to discrete measurement outcomes. Is dying a superposition of being alive and dead? Even in the Schrödinger's cat experiment, the only version of the cat that experiences dying is the dead cat. The live cat was always fine. If you start out dying, the only version of you that won't die is a cured version, and that is medicine, not quantum immortality.

On the broader multiverse or infinite-monkeyverse, we have the ship Theseus issue: is an identical copy of you identically *you*?

Well, I guess it depends what you consider "you" is.

If you are a physical being evolving over time, I guess no, other person in other place exactly like you is not you, there are two different persons.

If you are just a collection of mental states, I'm not sure, but in this case, there is not only one version of "you", a guy that was exactly like you until 10 years ago and now is doing different things is "you" too... And if you expand this vision, you will probably reach something like "open individualism", where you are everybody. Even more, since this don't require physical continuity a guy like you appearing now is your past "you" too... And, then, a guy remembering being a famous singer is him, even if these singer have never existed... Since this is based on memories, I guess that you could reach bizarre conclusions, like if your neighbor develop false memories of being you and you got amnesic, he is more you than yourself.

If we make the assumption that all possible versions of you are going to play out in the infinite multiverse, there are still a few things to consider.

1. The body actually has a limited lifespan. Thus there will be an end eventually to your existence in the "last" universe when there is no other option than your death.

2. "You" are not the other "You"s. There is only one of "You" that will get the lucky path of experiencing the entirety of your life. That you will not know the experiences of those that die. Thus we can also conclude that those that die, will not know the experiences of those that live.

2. "You" are not the other "You"s.

Yes, but from a subjective point of view they are others when they diverge, if the divergence is at the point of your death, you won't have more different experience, only the version surviving will experience things.

My question is, if quantum immortality is true and given approximately 107 billion people have lived on earth, there should be at least one or two who are immortal, alive and well somewhere in the world. Records don't show the existence of such individuals. What gives?

107 billion people
There are currently seven billion people alive today and the Population Reference Bureau estimates that about 107 billion people have ever lived. This means that we are nowhere near close to having more alive than dead. — Google

What is the probability that a person will achieve quantum immortality in the universe we exist in? :chin:

What is the probability that a person will achieve quantum immortality in the universe we exist in?

Supposedly, the probabilities os surviving certain events are almost 0, that's why only could happens in MWI, or maybe in an infinite universe. So the probabilities of see it in this particular world are almost 0 too.

One better objection I read is that if you are just an observer-moment and people can life indefinitely, the number os observer-moments in extraordinary survival situations would be far bigger than normal ones, so it would be more probable to you being experiencing one of them.

If you are just a collection of mental states, I'm not sure, but in this case, there is not only one version of "you", a guy that was exactly like you until 10 years ago and now is doing different things is "you" too... And if you expand this vision, you will probably reach something like "open individualism", where you are everybody. Even more, since this don't require physical continuity a guy like you appearing now is your past "you" too... And, then, a guy remembering being a famous singer is him, even if these singer have never existed... Since this is based on memories, I guess that you could reach bizarre conclusions, like if your neighbor develop false memories of being you and you got amnesic, he is more you than yourself. — Philosophuser

Right, none of which has anything to do with quantum mechanics. One can ponder exotic edge cases of unrelated identical twins, but these are questions about probability and language, not quantum mechanics.

There's an essay I read in The Atlantic, called The Multiverse Idea is Rotting Culture which dwells on some of the ideas in the OP.

The Multiverse Idea is Rotting Culture — Wayfarer

A point of clarification. The multiverse and the many worlds interpretation are two entirely separate ideas. The multiverse refers to the fact that parts of the early universe after the big bang moved away from each other very fast, and are no longer accessible to each other given the limitations of light speed. There's one big universe emanating from the big bang, and many separate islands within it, each unreachable from the others.

Many worlds is an interpretation of quantum physics that says that rather than an observation collapsing the wave function to one particular outcome, all possible outcomes occur, each in its own world that branches off at that moment.

Multiverse and many worlds are completely separate ideas. I'm not even sure that anyone has explored their interactions.

ps -- I read the article. The author, Sam Kriss -- whose work I know and enjoy -- conflates and confuses the multiverse and many worlds. He seems to be talking about many worlds in the article but sometimes calls it the multiverse.

Not only that. The New Scientist article Kriss links makes exactly the same mistake, talking about many worlds but calling it the multiverse. I believe there's quite a bit of confusion about this floating around.

A point of clarification. The multiverse and the many worlds interpretation are two entirely separate ideas. — fishfry

I’m well aware of the technical distinction but they tend to blur in the popular imagination. I was also going to mention Philip Ball’s criticism of MWI in Quanta magazine but I thought I’d leave it at the one.

BTW there’s a really good intro to Everett’s notion in Scientific American from a few years back The Many Worlds of Hugh Everett. I was struck by the shall we say less than auspicious origins of that idea.

I’m well aware of the technical distinction but they tend to blur in the popular imagination. — Wayfarer

I just wanted to note that for general info, especially since the linked article and the article that it referenced both made the same error.

BTW there’s a really good intro to Everett’s notion — Wayfarer

Sean Carroll, a rockstar physicist who makes terrific expository Youtube videos, is a big proponent of many worlds. I like to think of him as a great physicist but a not-so-great philosopher. In any event, the Schrödinger equation is physics. Interpretations of the Schrödinger equation are metaphysics, a point lost on many physicists. Remember that Newton did not make this error. He had his theory of gravity, which accurately predicted how massive bodies behave, up to the limits of observation at the time. But when pressed to say what gravity actually was, he famously said, "I frame no hypotheses." Meaning that science describes, it does not explain. Contemporary scientists still have a lot to learn from old Isaac.

I like to think of him as a great physicist but a not-so-great philosopher. — fishfry

Totally agree. He seems a super-nice person as well, and his podcasts are interesting but I think he's on the wrong side of the argument with respect to both MWI and multiverses (although, of course, who am I to say.) I think it would be preferable if science stopped trying to 'know the mind of God' as Hawkings said in Brief History of Time.

Oh shit! I just realized... If the universe is infinite in space, there are a lot of "yous", birthing continually, and if conciousness has nothing mystical and an identical person is you, then there is something like an "eternal retourn", you are in some sense "reincarnating", and living the same live continually, so if QI is possible, you will experience it, not a "copy" of you, but "this you"...

SHIT, some good objections?

If the universe is infinite in space, there are a lot of "yous", birthing continually, — Philosophuser

I regularly need to debunk this entirely fallacious claim, which is ubiquitous on the Internet and everywhere else.

Consider the infinite sequence 1, 2, 3, 4, 5, 6, ... It's infinite, but 2 never recurs, neither does anything else. Everything happens only once. For all you know, the world is just like that. Each of us really is a special snowflake after all.

Ok, you tighten your argument. In each finite region of space there are only finitely many atoms hence only finitely many possible configurations of atoms. If there are infinitely many such regions, what happens?

Consider that there are only two states, 0 and 1. Consider the sequence 0,0,1,0,0,0,0,0,0,0,0... Clearly there are infinitely many 0's. But 1 never reappears again. SOME state must recur infinitely often, but not every state necessarily does.

So even if the universe is infinite in extent; and we divide up space into infinitely many finite-volume regions, each containing only finitely many atoms that can take only finitely many configurations; it's true that SOME configuration must recur infinitely many times; but not the configuration representing YOU. Some sea slug gets replicated, but not me or you. Make sense?

Then again, there may well be laws of nature we don't yet know, that place constraints on which configurations can occur. So again, some sea slug gets duplicated but not you, because there is an as yet unknown law of nature that precludes humans from being replicated more than once, or left-handers, or primates, or whatever. Once atoms organize into chains of organic molecules, a biochemist will tell you that some combinations just can't occur at all.

Finally there is a probabilistic argument. You might say that statistically it's almost certain that every configuration would be duplicated infinitely many times. And you are correct. In the scenario of infinitely many regions, each of finite volume and containing only finitely many atoms; and in the absence of natural constraints as to what configurations may occur, so that we assume every configuration is equally likely; it is true with probability 1 that every possible configuration happens infinitely many times. That's the infinite monkey theorem.

However, that's not good enough. In infinitary probability theory, probability 1 events may fail; and probability 0 events might happen. The probability that you randomly select a real number from the unit interval and it turns out to be rational, is zero. Yet there are infinitely many rational numbers. You might pick one. I just threw a dart at the unit interval and it hit the point 2/3. A measure-zero miracle!

So the absolute best you can say is that IF all configurations of matter are equally likely (highly dubious IMO), the it is almost certain that every configuration will occur infinitely often; but it still might not. "Almost certain" is a technical term meaning that the probability is 1. But in infinitary probability, the event may still not occur. It's almost certain that a random real number is irrational; but rationals exist, lots of them. They just have what's called measure zero on the real line.

I really hope a few people read this and become disabused of this notion that in an infinite sample space everything must happen infinitely often. It's not true.

https://en.wikipedia.org/wiki/Infinite_monkey_theorem

https://en.wikipedia.org/wiki/Almost_everywhere

tl;dr: Some sea slug gets replicated infinitely often. But possibly you don't. Even in MWI, you might be the last copy of you alive. So make the best of it. Don't count on quantum immortality, which is based on bad math and arguably bad physics as well.

The probability that you randomly select a real number from the unit interval and it turns out to be rational, is zero. — fishfry

50%, surely? Otherwise you couldn't have a unique Dedekind cut for each real.

50%, surely? Otherwise you couldn't have a unique Dedekind cut for each real. — Kenosha Kid

Doesn't work that way. There are only countably many rationals and uncountably many irrationals. The rationals have measure zero in the unit interval and the irrationals have measure one. It's perfectly true that between any two reals there's a rational and vice versa, and this leads people into the common error you've made.

See for example

https://math.stackexchange.com/questions/124458/theres-a-real-between-any-two-rationals-a-rational-between-any-two-reals-but

https://math.stackexchange.com/questions/18969/why-are-the-reals-uncountable/18973

https://math.stackexchange.com/questions/1173495/are-there-many-fewer-rational-numbers-than-reals/1173502

I really hope a few people read this and become disabused of this notion that in an infinite sample space everything must happen infinitely often. It's not true. — fishfry

Repeating this for emphasis. But I fear it will be quickly forgotten. :cry:

Yes, I scratched my head at the seeming contradiction between the uncountability of the irrationals and the definition of the Dedekin cut, but of course by definition each cut either has a lower set with no upper bound or a greater set with no lower, et voila: uncountability. I guess I'd never really thought about it, thanks.

I guess I'd never really thought about it, thanks. — Kenosha Kid

You're welcome. Honestly it confuses me too, it's just one of those things that you "get used to," as von Neumann said. He famously said that in math you don't understand things, you just get used to them.

Yes, I always read the example of integer numbers, but this is an ordered series, the universe is not. And even if it's not granted, I guess the probabilities of it to occur are really high, like 99.999...%.

Yes, I always read the example of integer numbers, but this is an ordered series, the universe is not. And even if it's not granted, I guess the probabilities of it to occur are really high, like 99.999...%. — Philosophuser

Order makes no difference whatsoever to the argument. But if you insist, if the set of regions is countably infinite, it's ordered by picking any bijection with the natural numbers. Or if it has the cardinality of the reals, you can give it the usual order on the reals. If it has any cardinality whatsoever, you can biject it with an ordinal, assuming the axiom of choice, and give it that order. If the axiom of choice is false and the set of regions is not well-orderable, it's a very weird set. You have to pick one.

Or perhaps -- and this is my belief -- when physicists use the word infinity, they mean something other than mathematical infinity entirely, and haven't thought through the issues of basic set theory. I see this all the time.

The mainl point is that order is irrelevant in the argument. In fact my argument assumed a countably infinite set of regions and I didn't consider any other cases. It's hard to imagine an uncountable set of finite-sized regions, that's a very weird space. The real line can be divided into countably many finite-length intervals, delimited by the integers for example. But uncountably many? That's a weird topological space known as the long line. Like I say, physicists never think about the implications of their ideas about infinity.

Yes, I scratched my head at the seeming contradiction between the uncountability of the irrationals and the definition of the Dedekin cut, but of course by definition each cut either has a lower set with no upper bound or a greater set with no lower, et voila: uncountability. I guess I'd never really thought about it, thanks. — Kenosha Kid

I'm reminded of another example that illustrates the weirdness of the way the rationals sit in the reals.

Consider the rationals in the unit interval. Between any two irrationals there is a rational, infinitely many of them in fact. Suppose we were to put an interval, no matter how small as long as it's nonzero, around each rational. The intervals don't need to be the same size, as long as they're all nonzero. Then it's perfectly obvious that the intervals must overlap, and that their union must cover the entire unit interval.

Perfectly obvious, and false. Here's the counterexample. Since the reals are countably infinite, let $r_1, r_2, r_3, \dots$ be an enumeration of the rationals in the unit interval.

Let $\epsilon \gt 0$ be any tiny positive real number. Put an interval of length $\frac{\epsilon}{2}$ around $r_1$. Put an interval of length $\frac{\epsilon}{4}$ around $r_2$. Put an interval of length $\frac{\epsilon}{8}$ around $r_3$. In general, put an interval of length $\frac{\epsilon}{2^n}$ around $r_n$.

What is the sum of the lengths of all the intervals? Since there might be overlaps, the total length is at most $\displaystyle \sum_{n=1}^\infty \frac{\epsilon}{2^n} = \epsilon \sum_{n=1}^\infty \frac{1}{2^n} = \epsilon \cdot 1 = \epsilon$.

But $\epsilon$ is tiny, it's as small as we want! So we can cover the rationals in the unit interval with a collection of nontrivial intervals whose total length is as close to zero as we want! This is the definition of measure zero. And that means that the remaining elements of the unit interval, namely the irrationals, have length, or measure, 1. That's what it means to say that the probability of randomly picking a rational from the unit interval is 0; and the probability of picking in irrational is 1.

I love this example. The math is perfectly clear. I can not for the life of me visualize how the intervals could behave this way. But they do.

The other you being the same you depends on which stance on personal identity you take. But even then I'm inclined to say that neither biological or psychological view has it right.

As for the rest, I don't know.