Talk:Quantum immortality

I can't find any reference for the term "fallacious insane nonsense"; indeed a Google search turns up no other cite than Wikipedia itself. If this is indeed a widely used term by detractors of this theory, and not just a colorful putdown, then a reference needs to be cited in order to maintain NPOV.

Derek, you added emphasis for total nonsense and, while I am inclined to agree with you that it's nonsense, that emphasis also causes the article to take a non-neutral point of view. Simply stating it and layout out the counter-argument in the following paragraph is sufficient. -- Nate Silva

You've got completely the wrong impression. I worked out the immortality consequence of the Many Worlds Interpretation in the early 1990's and have had a humourous page on the Web describing it since 1995, two years before Tegmark published his paper. See http://www.arbroath.win-uk.net/life.html (That page is now defunct but it has been more recently transferred to http://www.fisheracre.freeserve.co.uk/life.html Ho hum. That page too is now defunct. I'll put it back up when I get my ISP sorted out on a more permanent basis). Now at http://members.shaw.ca/derekross/life.html

Given that, I'm hardly likely to think that the idea is nonsense, let alone try to slant the article to indicate that it is. The only reason that I added emphasis was to point out that the words insane fallacious nonsense were a quote, not that they were true from an NPOV. I don't know where the quote came from and I certainly didn't add it to the article. If you want to de-emphasise it, fine. The article is pretty balanced either way. -- Derek Ross 19:57 Nov 16, 2002 (UTC)

I love the phrase "fallacious insane nonsense" -- FIN should be a new acronym. I just got the wrong idea from the emphasis: that the article was siding with that idea. Sorry for the confusion. -- Nate

Nuclear physicists

Im not well read on this theory, but wouldnt the answer to how alternate-universe physicists possibly survive the nuclear bomb, is bc there will be alternate universes in which the bomb was not set off? or indeed universes where the individual never became a physicist at all? Vroman 22:22 8 Jun 2003 (UTC)

You are correct. From the physicist's point of view the bomb will be extraordinarily difficult to set off, whereas from the independent observer's point of view (a safe 40 miles away), it will invariably explode first time every time (assuming that we run the experiment several times with new bombs and new physicists). Other miraculous happenings such as chasms, into which it drops, suddenly appearing below the bomb; aliens abducting the physicist; the blast being completely directed away from the physicist for purely statistical reasons; etc., might also occur (but only from the physicist's point of view). -- Derek Ross

No connection to boundlessness

I've removed the following addition by User:Harry Potter:

Another criticism suggests that the experiment confuses the infinite with the boundless - i.e. a sphere has a boundless surface which is neverthless not infinite. The physicist merely experiences their life regardless of whether or not this is seen from a many-worlds interpretation or not.

There is no indication of why boundlessness is relevant to the discussion. Please feel free to explain. -- Oliver P. 23:44 8 Jun 2003 (UTC)

Limited immortality

I'm not familiar with the specifics of this theory, but it seems to me that unless the physicist was immortal in at least one alternate universe, he could not be immortal in them all. That is, even if the bomb doesn't kill him throughout the multiverse, he still dies eventually. --Neonstarlight 08:00, 17 May 2004 (UTC)

The physicist will never be immortal in all alternate universes, only in the ones where immortality is possible for him. Of course, this may be none of the universes. -- Derek Ross

Living with p-zombies

It would mean, that I will live up to about 80, and then I will get older and older but not die, miraculously avoiding death from aging (with telomeres somehow not shortening). As probability of such miracles is extremely small, only my consciousness will get into these parallel universes. Therefore, all people I will met when I will be about 300 will be p-zombies.

Moreover: Every little moment the world I live in is splitting into a bunch of parallel universes, and my consciousness is going always to one and only one of them. Consciousnesses of other people also are going to one and only one of them, and hardly likely they are going to the same parallel universe I'm going. That means, that almost for sure all people I meet and talk to them are actually p-zombies. -- Anonymous reader.

Well that's one possibility. Of course it's rather more likely that by the time you are 80, Bayer will be marketing teleMore^®, the miracle telomere extender. Too bad for the zombies but I'm sure that the vampires -- er, I mean the pharmaceutical industry -- will be happy raking in the cash.

On more technical point you should also note, that according to the theory, your consciousness ends up in all of the universes that it can, not just in one. The only futures that it doesn't enter are the ones in which you have died. So you can rest assured that you will be dealing with ordinary people rather than zombies (unless some Hollywood Science type disease has gotten loose!) -- Derek Ross

I kind of assume that by "p-zombie", you mean a person whose consciousness/soul has taken another branch of the tree? Though I'm having trouble telling them apart, that sounds more like many minds than many worlds, does it not? In particular, this whole theory assumes (and tries to reason about) a brain/mind duality which many-worlds does not seem to support. (Actually it occurs to me that this page is independent of many-worlds, though that's where I linked to it from. So maybe the link was decpetive.)

P-zombie is probably an abbreviation for philosophical zombie. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 01:09, 8 Nov 2004 (UTC)

Location of the mind

It's me again. How could my consciousness be continued in more than one universe? Suppose there was a deadly duel between two gunslingers from my neighborhood yesterday, Quick Bill vs. Jim the Arrow. Jim won, Bill got killed. But during the duel, I was pretty safe and my survival was not affected by the outcome. So, my consciousness should go to all the universes where Jim won and all the universes where Bill won (excluding those few, where I died for random independent reasons). So why I can see now through my window alive Jim feeding his horse and Bill's funeral on nearby graveyard and not otherwise?

Bill's consciousness went to these universes, where he won and Jim was dead. In these universes, I exist only as p-zombie, otherwise I could see both Bill and Jim alive and dead. Or I have misunderstood something.

If we take a functionalist or materialist view of human consciousness, it is a perfectly replicable phenomenon, so the universe's splitting would lead to a copy of your consciousness, with each one continuing on its own merry way and having its own merry experiences. You would, in effect, be two different people in two different universes with nearly identical memories (before the split). -Seth Mahoney 18:24, Jun 21, 2004 (UTC)

Exactly. Just remember that once a universe splits into two there is no communication between the two universes. Your consciousness (in each universe) can only sense its immediate environment using the senses in its own universe. Lack of communication between the universes means that the two copies of your consciousness cannot share information in the way that the two halves of your brain in this universe can share information. So in this universe you may wonder why you can see now through your window a live Jim feeding his horse and Bill's funeral on nearby graveyard and not otherwise. However in the other universe you will be wondering why you can see now through your window a live Bill feeding his horse and Jim's funeral on nearby graveyard and not otherwise. -- Derek Ross | Talk

Implications

The implications of quantum immortality being correct are rather odd, and I think taken together they fail Occam's Razor. (Note that this all applies to quantum suicide as well.)

The mind must be independent of the brain.
The mind must, at every choice point/wave collapse, pick one path to follow.
The mind must always select the path that preserves itself, regardless of low probability of such a path.
Implication: it is impossible to experience death from the first-person perspective. Everyone will perceive themselves to live forever, though the people around them die off normally. Eventually everyone will perceive a world in which they are the oldest person alive. Eventually everyone will perceive a world in which they have so outlived their contemporaries that they are considered to be a Messiah. Etc.
Implication: suicide is impossible. Though all observers may see it succeed, the person attempting it will see it fail. This is not only true of quantum suicide, as _any_ suicide is a quantum one. (That entry is kind of silly, for that reason.) The bullet from the gun will, with finite (small) probability, teleport through your head. It violates classical physics, but quantum physics doesn't bat an eye.

Frankly, everything postulated under quantum suicide and this page is totally non-falsifiable anyhow because _they can never be observed_. Given that, I think we have to reject both on Occam's Razor grounds. And certainly never suggest to anyone that they actually _perform_ the thought experiment. The results would be messy. Glenn Willen (Talk) [[]] 21:30, 4 Aug 2004 (UTC)

The ideas of quantum suicide and quantum immortality do not stand alone. If they did, then perhaps we could reject it on the grounds of Occam's Razor like you suggest. The question is, can we reject these thought experiments without rejecting the strikingly simple mathematical formulation of quantum mechanics? This mathematical formulation has been extensively tested experimentally, rejecting it would require the construction of complex, contrived alternative explanations. -- Tim Starling 01:28, Aug 6, 2004 (UTC)

I have thought for some time that death may have these results, though never so formally. I'm amazed to find Wikipedia considering the possibility.

The effect can quite easily be observed, but only by a person who is expecting to die. It can also be verified; some universes ought to contain a larger proportion of survivors than others. Carefully studying the death rate in our universe might reveal important details (though our universe is most likely quite boring).

In general, some number of people should have clear memories of near-death experiences or feel certain they should not have survived particular events. Even more generally, we might be totally wrong about natural selection and evolution. Genetic memory would be a particularly interesting topic -- somehow, animals develop instincts which protect them from environmental hazards that would almost never be survivable. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 06:38, 7 Nov 2004 (UTC)

What Tim says is true. I would also add that some of your statements don't seem to follow from anything. For instance

The mind must be independent of the brain.
The mind must, at every choice point/wave collapse, pick one path to follow.
The mind must always select the path that preserves itself, regardless of low probability of such a path.

I disagree with all three of these statements and would replace them with the two statements

The mind is probably dependent on the brain.
The mind must, at every choice point/wave collapse, follow every single path however likely or unlikely.

I also find it puzzling that you should say "everything postulated under quantum suicide and this page is totally non-falsifiable anyhow because _they can never be observed_" since the experiment by its nature always has at least one observer. -- Derek Ross | Talk

Discussion boards

I find this discussion fascinating, though I really would like to see it expanded on a proper discussion board. Does anyone have a good link where we could let these questions expand properly?

two good sources for discussion on QI are http://groups.yahoo.com/group/Fabric-of-Reality/ and http://www.eskimo.com/~weidai/everything.html -- qarl

Anyhow, I feel rather confused about the concept of my mind being immortal with certainty under the many worlds-interpretation. Assuming the many-worlds interpretation, many instances of me will exist in these many worlds - but they can not communicate with each other. In some of these worlds, I will continue to exist for ever - but is this the world in which that will be the case? It seems to me that the likelyhood of this current "me" being in the world where the bullet passes safely through my head is exactly equal to the likelyhood of the quantum mechanical effect happening that allows the bullet to safely pass me by. So, when I am sitting there in front of the gun, I whould be really nervous - I will very likely be in the wrong world to survive the event! Of course, there is a world where I will survive - but if that world isn't this one, I won't be able to notice my survival. There is no communication between the worlds.

I'm not sure if this interpretation is quite correct. It assumes a static universe seen from the perspective outside the four usual space/time dimensions. Essentially, it assumes that worlds don't "split" but rather that all have always existed and will all continue to exist. That squarely places the current "me" in one of these worlds (quite probably one where I have a mortal lifespan). There does exist some worlds that have been exactly similar to this one up till the point the gun is fired, but where I do not die. Also there are some worlds (many more) that have been exactly similar to this one, but where I do die when the gun is fired. The probability of being in a world where I die is equal to the probability of the bullet killing me. That also seems to mean that the ratio of the number of worlds where I die to the number of worlds where I live is equal to that probability.

On a completely off tangent note, it also appears to me that the interpretation of many worlds as a static universe (all have always existed and all will always exist - no "splitting") can solve all paradoxes of time travel. One only needs to assume that it is impossible to go back in time on one's own time-line, but that need not prevent one from going back in time on another time-line. If time-travel requires movement to an alternate world, the classic paradoxes vanish. If I go back and kill my ancestors, all I am removing from the history of the world is my alternate self in the alternate time-line I have ended up in. The ancestors of the "me" that goes on murderous rampage are safely alive back in my old time-line. Alternatively; if I go back in time just a bit and meet myself, I am only meeting an alternate me - not my "current" me. So I can easily meet myself even if I know that I didn't. It is simply two different "me" from two different alternate worlds that meet.

Even if there is only a single timeline, it is possible to get around the classical paradoxes quite easily if we assume that changes made can only propagate at the same rate that our present moves into our future. That would allow us to go back and kill our grandfathers with no noticable effect when we return to our present since the changes caused by the deaths would move forward in time at the same rate as our present moves forward into its future. Thus the changes would never catch up. With this assumption there is no need for alternate timelines to ensure a paradox-free universe. Having said that, this hypothesis also implies that the past will not be as we remember it because of changes introduced by time-travellers. -- Derek Ross | Talk 01:41, 2004 Sep 15 (UTC)

What I really would like to know is what the mathematics says about this idea of static multiple worlds. Does it necessarily indicate a universe splitting into more and more worlds as time goes by, or is an interpretation for a static universe with all the infinite number of worlds existing from the start possible? In the former interpretation, time-travel would be very problematic - not so in the latter. Or does the mathematics say nothing at all regarding the question? Anyone who knows? --Stefan Möhl, Sweden, Lund 23:25, 14 Sep 2004 (UTC)

It doesn't necessarily indicate a universe splitting into more and more worlds as time goes by. It is also possible for two universes to combine into one as elementary particles combine with each other. In certain types of universe where everything collapses back to a point there will only be one world at the beginning of time and one world at the end of time although there may be many worlds in between. That is why the many-worlds interpretation of QM is sometimes called the many-histories interpretation. -- Derek Ross | Talk 02:43, 2004 Sep 15 (UTC)

Further, it is not possible to distinguish between "universe-splitting" and "infinite universes". Theories explain why conditions lead to specific observations, but there is no difference between two theories that predict identical observations for identical conditions. It necessarily cannot be determined whether infinitely many independant universes exist. One might say that the multiverse is in a superposition of states: in one state, the universe splits at each instant into distinct universes; in another, all possible universes coexist simultaneously. A more precise statement is:

Every observation will have exactly one of infinitely many outcomes, with varying probabilities dependant on previous observations.

Universes which produce identical observations are indistinguishable from each other. It is almost possible for an observation to have no outcome, but this in itself is an outcome. Subjectively, it is impossible to observe the null outcome, as it is equivalent to no observation at all. Therefore, no observer can cease to exist.

Note that it is also impossible to observe an observation of the null outcome. One can attempt to describe nothingness in any way one chooses, but cannot ever realize exactly what it is. This is the heart of Zen Buddhism. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 20:35, 7 Nov 2004 (UTC)

Quantum Immortality or Metaphysical Mish Mash

The consciousness of a person with acute paranoia and or schizophrenia, etc. have been omitted in this entry. How do these fit into so-called quantum immortality? Is a person with mental illness sick forever? Is Down's syndrome eternal. Isn't this a state of consciousness? If there are an infinite number of universes that would mean I could exist in a universe where everything: my wife, my children, my bad notes on the guitar were exactly the same as this one, except one my ears was upside down. This seems unlikely.

Charlie Turek 30 Sept 2004

Far worse, imagine how horrible a war must be for the losing side, or the incredible cruelty that may be inflicted during capital punishment. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 06:38, 7 Nov 2004 (UTC)

That's the scary thing about the many-worlds interpretation. Whether the quantum suicide/immortality part is true or not, there's little doubt that all possible outcomes, good and evil, are expected to occur, no matter what actions individuals may take to provoke or prevent them. -- Derek Ross | Talk 07:08, 2004 Nov 7 (UTC)

If acute paranoia or schizophrenia affected a person's consciousness drastically, there might be an effect. Otherwise I see no reason why they might not live long enough in their personal timelines for cures to be discovered if they were lucky (or not be discovered if they were unlucky).

As for the upside-down ears, quantum immortality is implied by the relationship of the present to the future under the many worlds interpretation, so you would only have upside-down ears in the future if you started off with upside-down ears in the present or if there was some good cause for change. For instance you might look in the mirror and think "I'd look better with upside-down ears. I think that I'll contact a plastic surgeon." and then go ahead with it; or perhaps a group of mad surgeons might kidnap you, cut your ears off and sew them back on again upside-down for their own twisted reasons. But I'm sure that you are perfectly capable of imagining your own unlikely scenarios. The point is that unlikely is not the same thing as impossible. -- Derek Ross | Talk 07:26, 2004 Nov 7 (UTC)

Niven

I recall that Larry Niven wrote a cautionary short story about an Earth where it is well-known that the many-worlds interpretation is true. Consequently, the suicide rate is very high. Does anyone know which story this is? --[[User:Eequor|ηυωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 18:48, 7 Nov 2004 (UTC)

I think that you may be talking about All the Myriad Ways which was written in 1968 and first published as part of a collection with the same name in 1971. A widespread knowledge of and belief in the implications of MWI might well lead to more common depression or suicide though. Even in the happiest of situations, you would be aware that in other parts of the multiverse things went badly for you. Although, strangely enough, when things go badly for you it doesn't seem to give any consolation that in other parts of the multiverse things must have gone well. It must have something to do with the human tendency to concentrate on the negative side of things. -- Derek Ross | Talk 18:56, 2004 Nov 7 (UTC)

Yes, that's it! Another observation one might make is that, knowing events will be better in other universes, it is always true that one may improve one's life by ceasing to exist in any particular universe, with some probability that one's life will become worse. One might view oneself to be the entire collection of parallel selves and opt to eliminate all their selves that are unhappy (i.e., the movie The One has a correct premise, but its solution is backwards).

A reason it is not consoling that other selves are better off is: their happiness does not affect one's own happiness. It is also very discouraging to know that one's life will always be worse than it could have been. It may be more consoling to realize that all things share this condition and, in that respect, one is no worse off than anything else (which is, essentially, dukkha). --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 21:23, 7 Nov 2004 (UTC)

Practical uses...

Are there practical uses for quantum immortality? Just as a lottery draw was being made, could you hook yourself into some sort of mechanism which would kill you in all the universes where your numbers didn't come up? Thus, from your point of view, you would be guaranteed to win the lottery? Evercat 22:21, 7 Nov 2004 (UTC)

Winning a lottery in such a manner would be possible, but not guaranteed. The mechanism might simply fail, and its failure may be much more likely than the possibility of variation in the lottery draw. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 22:57, 7 Nov 2004 (UTC)

The New Scientist letter pages considered that very situation (a machine gun tied to your lottery numbers) after the magazine ran an article on QI a few years ago. The trouble is that QI only works if the Many Worlds Interpretation of QM is correct. If the Copenhagen Interpretation of QM is correct, you're dead. In fact the practical uses all seem to involve putting yourself into lethal situations so you'd better be pretty sure that it's all going to work before you do it.-- Derek Ross | Talk 23:13, 2004 Nov 7 (UTC)

The Copenhagen interpretation has been disproven by Shahriar Afshar's double-slit experiment. --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 00:09, 8 Nov 2004 (UTC)

So far as I know that experiment is still rather controversal, so I wouldn't rewrite all interpretation based on it quite yet. Laura Scudder 06:15, 8 Nov 2004 (UTC)

More reasonable experiments

Can an experiment be constructed which does not require the observer's death, and can be validated by someone other than the observer? --[[User:Eequor|ηυωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 00:30, 8 Nov 2004 (UTC)

The Copenhagen interpretation and the many-worlds interpretation are just interpretations. You can't prove or disprove them except by comparing their intuitive consequences with that of the mathematical formulation of quantum mechanics. Both of them are nothing more than that: paths towards intuitive understanding, not predictive theories. The many-worlds interpretation fares rather better than the Copenhagen interpretation, but the many worlds interpretation still suffers from a reliance on discreteness not present in physical situations. It also implies that the various worlds do not interact (just by use of the term "world"), when in fact the coupling merely decays exponentially in the presence of dissipation. Most physicists understand the basic mathematical background of quantum mechanics, and are able to switch between various models and interpretations easily, as convenience dictates. -- Tim Starling 05:14, Nov 8, 2004 (UTC)

It doesn't seem productive to distinguish between an "interpretation" and a "theory". CI does make predictions, namely wavefunction collapse and indeterministic behavior of measurements. CI has been proven to be an inaccurate description of QM.

Wavefunction collapse is a convenient approximation to the actual situation. -- Tim Starling 13:29, Nov 9, 2004 (UTC)

Discreteness is present in all physical situations involving fermions.

It's present in all bound systems, whether they involve fermions or bosons. The continuum is also present, in the typical situation of binding by the electromagnetic force. Wavefunctions aren't restricted to an infinite-dimensional vector, Hilbert space has to be invoked. There aren't just many worlds, there's a world for every point in some large-dimensional vector space. -- Tim Starling 13:29, Nov 9, 2004 (UTC)

What does "the coupling merely decays exponentially in the presence of dissipation" mean? --[[User:Eequor|η

υωρ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 05:58, 8 Nov 2004 (UTC)

See quantum decoherence. It means the off-diagonal elements in the density matrix decay in proportion to <math>e^{-{t/\tau}}<math>. Decoherence occurs when there is dissipation of heat. -- Tim Starling 13:29, Nov 9, 2004 (UTC)

Since Eequor moved my text to the section above, I guess she's trying to subtly hint that I didn't answer her question. She asked "Can an experiment be constructed which does not require the observer's death, and can be validated by someone other than the observer?" The answer that I'm hinting at is no, it can't be validated. That's because the many-worlds interpretation is not a theory, it doesn't have testable consequences, except on the level displayed in this article. Quantum mechanics says that there is a density matrix with lots of non-zero elements. Presumably some of the basis states with non-zero densities are wavefunctions where the person is living, and some of them are wavefunctions where the person is dead. How we interpret this mathematical statement does not impact the results of an experiment.

To put it another way, quantum immortality is experimentally indistinguishable from extraordinarily good luck. -- Tim Starling 14:04, Nov 9, 2004 (UTC)

Oh, I'm sorry! I'd thought you must be replying to sth else; your comment had seemed to be in the wrong section. --[[User:Eequor|ᓛᖁ

ᑐ (https://academickids.com:443/encyclopedia/index.php/User_talk:Eequor)]] 21:56, 1 Dec 2004 (UTC)

I just realised this is related to the anthropic principle. The experimenter's data is skewed by only taking data points when he is alive. He doesn't sample the rest of Hilbert space. This is exactly the same as remarking that the Earth is amenable to life. Of course it is, we're standing on it! Similarly, you can skew personality statistics by only counting the people who bother to fill in a questionnaire. This is an extreme case: we only sample a tiny, carefully selected fraction of Hilbert space, by using a measurement apparatus that only takes data when the variable we wish to measure has the value we want to see. -- Tim Starling 14:21, Nov 9, 2004 (UTC)

Doomsday Argument paragraphs

I've added some stuff about how a version of the Doomsday Argument, generalized to the many-worlds scenario, might provide an argument against quantum immortality. The details of the generalized argument are deep within a rather long-winded paper that is linked from the Doomsday argument article. I don't know whether it's worth making a separate "Many-worlds Doomsday Argument" article where I can describe the mathematics more fully.

User:John Eastmond 1 Dec 2004

While I can see that the Doomsday argument shows that it is likely that no new humans will be born after a certain date, I can't see how it has anything to say about the individual lifespans of those humans after birth. When it talks about the end of the human race, it is surely talking about the end of new births rather than the death of individuals. Our Doomsday article simply plugs in a value of 80 years for the average (?) human lifespan and then assumes that mankind will die out eighty years after the last birth. Thus it is not clear to me what its relevance to the quantum immortality article is. -- Derek Ross | Talk 20:52, 2004 Dec 1 (UTC)

Thinking about it further the confidence level part of the Doomsday argument provides an easy way to harmonise the two arguments. When we say that the human race will have died out by 12,000AD with a 95% confidence level, we are saying (in terms of many worlds) that humanity will have died out in 95% of the worlds but will still exist in 5% of them. Because of the nature of the Doomsday calculation, you need to pick a confidence level less than 100%. Therefore "many worlds Doomsday" would predict that there is always a small percentage of the many worlds in which new humans were still being born and in which therefore, Doomsday never arrives. Note that this is independent of QI itself. Since Doomsday is about the birth of individuals, I, as an immortal individual, might find myself in a future where no other human beings are alive (Doomsday Soon) or in one of the same date where the birth rate is still above zero (Doomsday Later) without affecting the DoomsDay argument. -- Derek Ross | Talk 21:20, 2004 Dec 1 (UTC)

The more I think about it the less I can see the relevance of the Doomsday argument here. Reading the new text doesn't help, so I can only conclude that it needs clarification. I have moved the new text here, so that it can be discussed.

A suggested generalization of the Doomsday argument seems to argue against the immortality of an individual's consciousness. The basic Doomsday argument attempts to make a probabilistic prediction about the longevity of the human race. It proceeds by arguing that, a priori, we are equally likely to find ourselves anywhere along the timeline of human history. As it is not possible to stretch a uniform probability distribution over an infinite set of humans, this assumption implies that there must exist some finite limit to one's temporal position within the human race. As there seems to be no reason why such an upper bound should exist one concludes that there must be something wrong with the reasoning.

A possible solution is to adopt the many worlds view of reality in which time has a tree-like structure with many actually-occurring futures branching from each present moment. If one assumes that only a finite number of humans are born along each branch then one can apply a uniform probability distribution for one's position along a branch without any problem. On combining all these probabilities, with appropriate 'weights' for the different branches, one arrives at a final probability distribution that successfully spans an infinite set of human birth times. One finds that the Doomsday argument no longer predicts the lifetime of a particular version of the human race that the observer experiences if he lives until Doomsday.

These two paragraphs describe the Doomsday argument as it might be if the MW hypothesis is taken into account. I have a minor quibble with the adjective "tree-like" since the structure is more like a network but overall it seems to describe the situation reasonably clearly.

Thus one concludes that no particular version of the human race lasts forever. Instead one finds that for any given finite lifespan there is always some version of the human race that will have a longer finite lifespan. Now, instead of applying the argument to the human race, it is suggested that one can restate it in terms of 'moments' along a span of consciousness. One then concludes similarly that a particular stream of consciousness cannot continue forever. Instead, one finds that, for any given finite stream of consciousness, there are always versions of the stream of consciousness that have longer lifespans. Thus, as each stream of consciousness has a finite lifespan and so eventually dies, the rather daunting prospect of compulsory immortality is avoided.

This is the paragraph that I have difficulty with. It jumps to a lot of conclusions without making the steps clear. Also it uses linear concepts such as stream of consciousness where they are not appropriate. In the Many Worlds interpretation, memory may form a stream but consciousness need not. In principle there is surely one consciousness which keeps splitting at decision points, isn't there ? Finally the conclusion seems contradictory. On the one hand it states that there are always versions of the stream of consciousness that have longer lifespans which implies that QI is the outcome and on the other hand it states that as each stream of consciousness has a finite lifespan and so eventually dies, the rather daunting prospect of compulsory immortality is avoided. which denies that QI is the outcome. Which is it ? -- Derek Ross | Talk 22:50, 2004 Dec 1 (UTC)

I think you're absolutely right - I haven't made the link between the Doomsday Argument and quantum immortality very clear at all. I'll try to think up a better version of the last paragraph and post it here for discussion -- John Eastmond 13:00, Dec 2 2004 (GMT)

I don't think I could describe the link between the Doomsday Argument and Quantum Immortality in one paragraph. -- John Eastmond 14:15, Dec 8 2004 (UTC)

Fair enough. But then you don't absolutely have to. -- Derek Ross | Talk 15:06, 2004 Dec 8 (UTC)

Everett - father of QI

you might want to mention that the original derivation of the QI argument was made by Hugh Everett himself - as revealed in his correspondence with Keith Lynch.

Everett firmly believed that his many-worlds theory guaranteed him immortality: His consciousness, he argued, is bound at each branching to follow whatever path does not lead to death —and so on ad infinitum. (Sadly, Everett's daughter Liz, in her later suicide note, said she was going to a parallel universe to be with her father.)

http://www.hep.upenn.edu/~max/everett/everett23_lynch.html http://www.hep.upenn.edu/~max/everett/

--Qarl 22:30, 30 Jan 2005 (UTC)

That is one of the reasons why I kept pretty quiet about QI when I worked it out for myself in the early 1990s. It seemed to me that widespread belief in it would make suicide more attractive and I did not want to live in a universe in which my friends and relatives were more likely to kill themselves. Oh well, too late now. -- Derek Ross | Talk 01:49, Mar 26, 2005 (UTC)

sleep?

i think the discussion on the "sleep counter argument" should be edited and possibly removed - it is based on a misinterpretation of QI.

QI predicts that a person will have unending consciousness from their own perspective - not necessarily from the perspective of third parties. this is exactly what happens when a person sleeps - he experiences an unbroken chain of consciousness from falling asleep to waking (the interruption of dreams hurts nothing.)

a (lame) attempt at modifying the article:

...They also claim that the logic of the thought experiment would suggest that a conscious observer can never become unconscious, and therefore can never sleep. A counterargument to this is that the period of sleep is experienced only by third parties; the observer himself experiences falling asleep, dreams, and waking. From his perspective, the chain of consciousness in unbroken.

as i think about it - the "sleep counter argument" could be modified slightly to make it work. rather than sleep as a break in the chain - the "falling asleep" could be stretched into an infinite decline. this is very similar to Tegmark's decline counter argument.

--Qarl 23:38, 30 Jan 2005 (UTC)

Brain damage

I also wonder about the possibility of a partial transfer of consciousness from one instant to the next. What happens if one's brain is damaged only partially, is the consciousness the same or not? It seems easy to argue it is not the same, but then that could be generalized to individual brain cell deaths; meaning that no cells/conections that contribute to consciousness can be destroyed, perhaps this could be even further generalized to include the creation of new connections/cells as well. In which case only a static mind would be possible for the future of an observer. My memory tells me that I have been constantly changing (I realize this does not conflict with the above statements), but basically it seems the 'I' in the past has been destroyed at nearly every instant in my life. It seems vaguely feasible to rig an experiment that will kill a consciousness if it does not change between a time interval. Of course, I suppose the apparatus would simpyl fail every time in such a case; the unvierse would not want to be pushed into a universe that did not exist. --PhoenixPinion , 00:15 25 Mar 2005 (UTC)

It am pretty sure that is impossible to come to a sensible conclusion about this without a good idea of what consciousness itself is and what its relationship with physical events might be. It looks to me as if it is related to communication (perhaps a reflexive form of it) but nobody has a good explanation yet and as I result I doubt that we can say much more about QI than we already have. -- Derek Ross | Talk 01:55, Mar 26, 2005 (UTC)

I think this is a rather important point against the whole idea of quantum immortality. Physical brain damage and things like dementia can change the victim's personality and mind as a whole drastically. (By the way, the bullet example could lead to severe brain damage instead of death. Actually, I suppose all of the examples could, with some small probability, and we are dealing with small probabilities here.) If we add more and more brain damage, we'll end up with a less and less functional and finally with a completely dead mind. How does this fundamentally differ from causing deadly brain damage at once? --Lakefall 23:14, 10 Apr 2005 (UTC)

When I pondered this question, the hypothesis I arrived at is that perhaps consciousness is a "quantum" phenomenon in the sense that it is reducible to a single, binary, "on-or-off" quantum of consciousness, similar to how light either "is or ain't" once reduced to the photon level, but can be intensified arbitrarily above that smallest "unitary" measure by addition of more photons. Similarly, maybe consciousness as experienced by a healthy, young Albert Einstein (as an example of a human mind operating at a generally high level of awareness and function) could be analogized to a torrent of photons, while a cicada with half its head chewed off might be compared to a measly collection of three or four photons. While both Einstein and the brain-damaged insect might properly be described as experiencing "consciousness," as both have at least the minimal quantum of consciousness (at least under my thought experiment); nevertheless, clearly the healthy genious experiences his consciousness more intensely than the maimed bug.

If my S.W.A.G. has merit, then it is true that the vast majority of quantum-suicide experiments will result in messy emergency-room victims who nonetheless end up once again being "conscious" in some (greatly reduced?) sense, except for those universes in which the bullet truly extinguishes every last "quantum" of consciousness.

--Ryanaxp 05:51, Apr 11, 2005 (UTC)

What about Quantum longevity instead?

So a few months ago I read about the quantum suicide experiment, and I was sitting on the subway wondering why I wasn't dead yet. Not from natural causes, but I live in a dangerous city and do dangerous things like fly through the air 30,000 ft. above the ground. So I came back to Wikipedia to see if there was a theory on quantum longevity, and found this instead. I was wondering if there is another theory that isn't so far-fetched, that basically says the following:

The MWI is true, and if a quatum event creates a world where we die and one where we live, then we do not perceive ourselves as dying.
These events happen on the macroscopic scale and frequently enough that, for example, anytime you see someone killed on the news, there was (almost certainly) some split world where that person survived.
These split worlds aren't miraculous or fantastic, just slight variations of reality (e.g., the mass murder decided to start shooting in the K-Mart instead of the Wal-Mart that I was shopping in).
Immortality is physically impossible and will never be discovered by humans.

So putting this all together, we can basically say that, though it's ridiculous that we'll each notice ourselves living forever, we will notice that we live out our lives without experiencing some unnatural death. —Sean κ. ⇔ 18:27, 17 May 2005 (UTC)

You don't even need quantum physics for this, do you?

If the universe actually is spatially infinite (flat or open), and non-periodic, then by Kolmogorov's zero-one law everything that is possible happens somewhere - happens an infinite number of times, in fact. That's pretty simple.

Therefore, there is an infinite number of Earths identical or very similar to this one. In most (assuming no major advances in medicine) I'll die before I reach 100; in some I won't. In general, for any imaginable cause of death, there is some way, however unlikely, that it won't happen. Nuclear bomb goes off next to me? The blast and radiation all travel around me. Bullet in the head? Bounces off. Decapitation? Air molecules spontaneously arrange themselves into a new body.

The "laws" that say all these things are "impossible" are, like the second law of thermodynamics, only statistical. They're so unlikely as to be effectively impossible, but given an infinite number of chances they have to happen. And, obviously, on the Earths where they don't happen I won't notice - I'll be dead. Therefore, no matter what, an infinite number of me are going to live forever.

Can somebody tell me if this is wrong?

Nickptar 02:00, 23 May 2005 (UTC)

I'd just like to clarify what I mean by "the second law is statistical", in case anyone decides to attack that: in most randomly chosen systems with a hot object next to a cold object, heat flows from hot to cold. But the laws of physics are time-reversible, so if I take a system in which heat has been moving from hot to cold for a while, and reverse the direction of every particle, it will go backwards and heat will move from the cold to the hot object. This same argument can work for all sorts of unlikely occurence; if you drop a teacup on the floor, then reverse the direction of every particle in the vicinity, the sound waves, heat, and such released will come back to the teacup and cause it to go back together and jump up to your hand. Etc. As I said, many things are possible but so improbable as to be effectively impossible - but in an infinite universe, they all happen somewhere. Nickptar 02:12, 23 May 2005 (UTC)

The reason why QI doesn't apply under the infinite spatially flat universe scenario is that all of the duplicate Earths are independent. There is no communication between them whatsoever. So if you die there is no way that your consciousness can continue in one of your copies: each of which has an independent consciousness. This is different from the many-worlds scenario in which an infinite number of universes may share the same physical past moment (and indeed, under the right circumstances, the same physical future moment), thus allowing communication in a way which cannot occur in a spatially infinite but non-quantum universe. In a spacially infinite, non-quantum universe each copy of you has its own past and future which may be historically identical to that of other copies but which is not physically identical with any other copy. -- Derek Ross | Talk 06:38, May 23, 2005 (UTC)

Well, that starts getting deeper into the philosophical debate over what an "independent consciousness" is. Personally, I would consider someone with the exact same memories and way of thinking as me to be me, I'm not concerned with how that congruence came about in the first place. So if I die but someone somewhere who is exactly like me in every respect (except the dying part) goes on, I'd say that "I" was still alive. I suspect this just comes down to a matter of opinion, though, so if you disagree then you disagree and we should probably just leave it at that. I've participated in some pretty endless debates on this subject on Usenet and it always seems to come down to "yes it is"/"no it isn't" :) Bryan 07:20, 23 May 2005 (UTC)

Understood, Bryan. If you'll forgive me for paraphrasing, I have assumed that consciousness is a (communication) process whereas I think that you regard it as an (internal) state. Hence the difference in our viewpoints. Is that a fair summary ? -- Derek Ross | Talk 08:45, May 23, 2005 (UTC)

Sounds like an excellent summary to me. In the event that this material goes into the article all we'd need to do is describe out both viewpoints and mention how they differ, and hopefully that would be sufficient. I'm not aware of any definitive way of showing one or the other to be more "correct". Bryan 18:38, 23 May 2005 (UTC)

Agreed. The current state of knowledge doesn't give us any hint as to which one is more likely to be correct, so it's up to personal preference at the moment. -- Derek Ross | Talk 06:20, May 24, 2005 (UTC)

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