Dear Don,
I have been reading Jacques's further posts with despair. Yes, of course living to great age is no evidence of MWI. However, if I believe in MWI then I believe I will live to great age.
I think you should bite the bullet and draw attention to the fact that there will always be a subsequent branch in which you are not dead, and if we never experience the branches in which we are dead then we can expect to live for ever. Don't forget to mention who said it first!
James
---- you wrote:
> Dear James,
>
> Thanks for your message, which I read after revising my paper and
> resubmitting it just a few minutes ago. (I'll attach part of my resubmittal
> message, leaving off the uudecoded file of the revised manuscript.) I did come
> to essentially the same conclusion Jacques Mallah did about the evidence of
> living to 2100, after receiving a message from Jerry Finkelstein, even before I
> received Jacques' message. It is a bit paradoxical, that in the MWI one
> predicts the certain existence of maverick worlds, such that the beings in them
> (and hence not directly aware of the many more more normal worlds) should
> conclude from their low likelihood that they are evidence against the MWI (or
> any other form of QM with the same basic measures), but this is presumably an
> inevitable consequence of a many-worlds theory.
>
> You might be interested in some comments I made in a previous version
> of my paper I sent to some colleagues March 19, 13 days before I put it on the
> LASNL eprint archive after shortening it to try to meet Phys. Rev. Lett. length
> requirements (which I failed to do at that time). On March 19 I was unaware of
> Tegmark's paper and did not remember Squires' discussion of quantum
> immortality, though they did not not change my opinion of it (fairly negative,
> as you can see from the excerpt, not at all glorious as the Christian view of
> heaven for believers). I'll attach this excerpt immediately below, followed by
> the header part of the resubmittal message, and then next (separated by
> #######) a message I sent to Jacques Mallah a few minutes ago.
>
> I certainly would not advocate suicide, even if one believed in the MWI
> (and maybe, for a pessimist, an attempt would be even worse in the MWI because
> of the certainty of a world in which he had a failed attempt that left him
> paralyzed or in terrible pain).
>
> Thanks for your messages.
>
> Best wishes,
>
> Don
>
>
> ************************************************************************
>
> \begin{sloppypar}
> \section{Different consequences
> when observers are destroyed}
> \end{sloppypar}
>
> One example of an observational distinction
> between many-world and single-history quantum theories
> is what observers should expect to observe
> when they are being destroyed differently
> in different ``worlds.''
> For example, assume that the death of an
> observer is due to causes that have
> significant quantum uncertainties.
> This seems almost certainly to be the case
> for human observers on earth.
> (I.e., quantum mechanics makes it
> in principle impossible for a life
> insurance company to give a unique correct
> prediction for the lifetime of a client.)
> Then in some ``worlds,''
> %(whether actual or possible),
> an observer would have one lifetime,
> whereas in other ``worlds''
> he or she would have
> a significantly different lifetime.
>
> Since quantum mechanical amplitudes
> are generically precisely zero
> only for a set of possibilities of measure zero,
> it is plausible to make the unproven assumption
> that human observers on earth
> in our present ``world''
> have a very tiny but nonzero
> measure or probability
> of living far beyond their life expectancy.
> For example, assume that if you are a twentieth century
> reader of this paper, the year 2100
> is sufficiently beyond your life expectancy
> that in almost all (but not quite all) ``worlds,''
> you will be dead by then.
> (If one postulates medical advances so
> that your life expectancy is extended past 2100,
> just replace this date with a sufficiently later date.
> I would be very surprised if
> it were medically and economically
> possible to expect for you to live
> more than a few centuries
> in most ``worlds.'')
>
> So if the probability or relative measure
> for you to live to 2100 is extremely small
> but not quite zero, in a single-history quantum theory
> it would be very improbable for you to be alive then.
> On the other hand, in a many-worlds quantum theory
> (which I personally adopt as my working hypothesis),
> I predict there will be some ``worlds''
> in which you are alive then and remember my prediction.
> (I assume that if you are not alive then,
> you will not remember my prediction.
> Thus I am disregarding the possibility
> of an other-worldly afterlife
> in which you are both aware of the year 2100
> and remember my prediction then.)
>
>
> Therefore, if you are alive in the year 2100
> in this universe
> and remember my prediction that you indeed will be,
> this will be strong evidence
> for a many-worlds quantum theory
> rather than for a single-history theory,
> since by the assumptions above,
> in a single-history theory
> it would be very improbable for
> the single existing ``world'' in the year 2100
> to have you alive in it.
> (Unfortunately, in the many-worlds theory
> I believe in, I would predict that in
> most of the ``worlds'' in which you are alive
> in the year 2100, I will not also be alive
> to say, ``I told you so,''
> and in most of the ``worlds''
> in which I am alive in 2100,
> your will not be alive to be told, ``I told you so,''
> so I must content myself to telling you now.)
>
> I first heard this bizarre prediction
> of many-worlds quantum theory from Edward Teller
> \cite{Tell},
> but he seemed to regard it as a {\it reductio ad absurdum}.
> %of many-worlds theories.
> At the time
> I did not attempt to rebut Teller's argument
> (and must admit I did not even understand it
> until another participant in the conversation,
> whose identity I don't remember now,
> later that night explained it to me).
> But now I believe this prediction of many-worlds
> quantum theory should be taken seriously,
> despite its extremely counter-intuitive nature.
>
> The counter-intuitive nature of the prediction
> that there exist ``worlds'' in which you are alive
> and remember in the year 2100 the prediction
> that you read by the year 2000
> can be softened somewhat by pointing out that
> the measure of worlds in which this occurs
> will no doubt be extremely tiny,
> so this observation
> %(of being alive in 2100
> %and remembering reading by 2000 a prediction
> %that you would be alive in 2100)
> is almost certainly a very atypical observation
> out of the set of all observations,
> even if it definitely occurs within a many-worlds theory.
> This is analogous to saying that observations
> when one is in the billionth second
> of one's life would be very atypical observations,
> less than one billionth of all one's observations,
> even though a large fraction of present humans
> experience such observations
> (though usually without realizing which second
> the billionth one is).
>
> The longer one waits into the future,
> the smaller the quantum mechanical measure
> (e.g., expectation value) for an observer alive
> at the end of the twentieth century
> to be alive then, but presumably
> this measure never drops precisely to zero
> at any finite time.
> One might summarize this gradual diminishment
> of the measure for the continued existence
> of an observer in many-worlds quantum theory by saying,
> ``Old observers never die; they just fade away.''
>
> Of course, one must recognize that this
> fading of the quantum mechanical measure
> is not to be confused with any observation,
> experience, or perception within the temporal
> sequence of ``worlds'' whose measure is fading,
> though there is also likely to be a quite
> different fading of one's intellectual
> abilities in the temporal sequence
> that one would experience.
> Because of this latter fading and other
> degeneration that is likely to occur,
> the many-worlds picture of ``everlasting life''
> within this universe is not a very hopeful one.
>
> The prediction of this section
> has the advantage of being testable by each of you
> (at least if a many-worlds theory is correct;
> if instead a single-history theory is correct,
> that alternative would not be observationally confirmed
> within this universe
> by the failure of the prediction to come true,
> because then you would be dead
> and presumably not conscious within this universe
> of the failure of the prediction).
> However, the prediction does have the disadvantage
> of requiring a long wait.
>
> One could attempt to speed up the test
> by trying to perform Deutsch's proposed experiment
> \cite{Deu} mentioned above.
> However, I personally doubt that this experiment
> could be performed before the year 2100, if ever,
> so it might not be any faster than just waiting
> for my prediction to be fulfilled.
>
> Another attempt to speed up the test
> would be to try something like Russian roulette
> a large number of times, assuming that
> its randomness can be traced to
> quantum mechanical fluctuations:
> If a many-worlds theory is correct,
> there would almost certainly be a ``world''
> in which you survived,
> but if a single-history theory
> is correct,
> after pulling the trigger many times
> you would most likely
> no longer be alive at all
> (at least within this universe).
>
> It has been argued
> that an advocate of a many-worlds theory
> ought to be willing to play Russian roulette
> for a nickel \cite{UnZu},
> since there would be worlds
> in which he survived, and in them
> he would be a nickel richer.
> But this argument ignores the grief
> to survivors and loss of the good
> that the experimenter might have done
> in the worlds in which he is shot,
> so such an experiment would be unethical
> whether or not many-worlds quantum theory
> is correct.
>
> Even a totally selfish
> experimenter might be deterred
> from playing Russian roulette
> by the possibility that in most of the
> ``worlds'' in which he survived,
> he might have been wounded by a bullet
> and suffering horrible disability
> or excruciating pain.
> (Such thoughts of ``worlds'' with botched
> attempts might also help deter people
> considering suicide if they put
> any credence into many-worlds quantum theory.)
> So do not try this experiment at home!
>
> #########################################################################
>
> Date: Mon, 3 May 99 16:06:02 MDT
> From: don (To: prltex.domain.name.hidden, prl.domain.name.hidden.org)
> To: prltex.domain.name.hidden, prl.domain.name.hidden.org
> Subject: resub LD7128 Page
> Cc: "Meher Antia" <attmail.wmdaniel.domain.name.hidden>, finkel.domain.name.hidden.lbl.gov,
> jlfinkelstein.domain.name.hidden, Jacques M Mallah <jqm1584.domain.name.hidden.ACF.NYU.EDU>,
> hartle.domain.name.hidden, jgribbin.domain.name.hidden.susx.ac.uk, don.domain.name.hidden.UAlberta.CA
>
> Dear Sir;
>
> Thanks for your snailmail message telling that my original submission
> of this paper, "Observational consequences of many-worlds quantum theory"
> (LD7128), that I submitted to you by e-mail April 1, was too long (536 lines).
> I have now shortened it by what I estimate to be at least 78 lines, so it
> should be about 458 lines long and hence fit your length limit of 460 lines.
> (I also found that one part of the paper was controversial and probably wrong,
> so I deleted it.)
>
> I have just replaced the paper at the LANL eprint archive with the
> message below, where the revised version may now be retrieved from the URL
> <http://xxx.lanl.gov/abs/quant-ph/9904004> if you wish to get it from there.
> Or, you may get the revised version from the uudecoded file at the bottom of
> the message below. If you would like a plain ASCII version of the LaTeX file,
> please let me know.
>
> Sincerely,
>
> Don Page
>
> ****************************************************************
>
> Date: Mon, 3 May 99 15:43:30 -0600
> From: don.domain.name.hidden (Don N Page)
> To: quant-ph.domain.name.hidden
> Subject: replace 9904004
> Cc: don.domain.name.hidden
>
> \\
> Title: Observational Consequences of Many-Worlds Quantum Theory
> Authors: Don N. Page (CIAR Cosmology Program, University of Alberta)
> Comments: 8 pages, no figures, LaTeX. Messages from Jerry Finkelstein and
> Jacques Mallah have led me to realize that, although I stand by my prediction
> that in a many-worlds theory you will be alive in the year 2100 in some worlds,
> paradoxically the evidence you will have then will not support many-worlds
> quantum theory over single-history quantum theory, since in either theory it
> will be evidence of very low measure and likelihood for a random observation.
> Therefore, I deleted this part of the paper (and shortened other parts).
> Report no: Alberta-Thy-04-99
> \\
> Contrary to an oft-made claim, there can be observational distinctions
> (say for the expansion of the universe or the cosmological constant) between
> "single-history" quantum theories and "many-worlds" quantum theories. The
> distinctions occur when the number of observers is not uniquely predicted by
> the theory. In single-history theories, each history is weighted simply by its
> quantum-mechanical probability, but in many-worlds theories in which random
> observations are considered, there should also be the weighting by the numbers
> or amounts of observations occurring in each history.
> \\
>
> ######################################################################
>
> Begin forwarded message:
>
> Date: Mon, 3 May 99 16:35:04 MDT
> From: don (To: Jacques M Mallah <jqm1584.domain.name.hidden>)
> To: Jacques M Mallah <jqm1584.domain.name.hidden>
> Subject: Re: Recent paper on MWI
>
> Dear Jacques,
>
> Thanks for your message. Jerry Finkelstein had asked me how the
> evidence of one's living to 2100 would be any diferent from the evidence of
> getting any other low-measure result, which would occur in MWI. (I suppose the
> only difference I see is that one would not be alive to be aware of the
> contrary evidence in other worlds.) But this got me to realize that although
> the maverick worlds in which one would live to 2100 certainly exist in the MWI,
> they would have so low a measure that one experiencing it would be experiencing
> a very low typicality observation, which if one counts the typicality as the
> likelihood, as I argue one should do in my Sensible Quantum Mechanics papers,
> would be evidence agains the MWI just as strong as against the single-history
> version.
>
> So I agree with your criticism. I had been waitng to change the paper
> until I got the referee's report back, but then today I got a message saying it
> was too long to be sent out to referees, so I shortened it and also replaced it
> at LANL, as you saw from my previous message. (I also thanked you for
> discussions.)
>
> On your last comment, about the anthropic principle, I agree that many
> have been saying that one should weight by the number of observers (and I cite
> several of them in my paper). But I have not seen anywhere published the
> simple observation that one does not get this in single-history QM for choosing
> between different possible histories. (Of course it does work for different
> parts of one history, and I alluded to that in my discussion of the paper of
> Martel, Shapiro, and Weinberg.)
>
> It was interesting that you referred to Smolin on the anthropic
> principle. He attacked it on page 205 of his book under the assumption that it
> would produce the least amount of life possible, which is what one would get
> from a single-history theory in which one just takes the conditional
> probability that life exists, without any further weighting by the amount of
> life or consciousness. I'll attach a message I sent to him shortly after
> writing my paper. He gave only a very short response that did not address the
> issues I raised, which may or may not indicate that he did not violently
> disagree with what I had written.
>
> Thanks again for your comments. I'm not sure when I'll have time to
> answer your objections to the combining religion with the MWI, and I'm afraid
> I've forgotten what the objections were (except for a vague memeory that it had
> something to do with the problem of evil, which certainly is a problem with
> almost any worldview but hasn't been taken as fatal by most adherents of
> religion).
>
> Best wishes,
>
> Don
>
> Date: Mon, 5 Apr 99 15:28:02 MDT
> From: don (To: smolin.domain.name.hidden)
> To: smolin.domain.name.hidden
> Subject: Observational Consequences of Many-Worlds Quantum Theory
>
> Dear Lee,
>
> I thought you might be interested in a new paper of mine which I
> submitted April 1 to Physical Review Letters and put on the quant-th eprint
> archive of LANL, where it as been assigned the number quant-ph/9904004 and thus
> can be found on the Web at the URL <http://xxx.lanl.gov/abs/quant-ph/9904004>.
>
> I will welcome any comments you may have.
>
> I think the ideas of this paper have some relevance to your fascinating
> thoughts in The Life of the Cosmos, which I enjoyed reading a few weeks ago.
> (I would like to have had time to make more comments about your book, but I
> haven't had time yet and probably won't in the very near future.)
>
> In particular, on page 204 you adjoin two more hypotheses to the
> anthropic principle to make it testable. I think I would agree with these two
> postulates, and I think I would agree with your conclusion at the top of page
> 205 ("it is most probable that we find ourselves in a universe with the least
> possible amount of intelligent life") if single-history QM were true. But if
> many-worlds QM is true, then I argue that one should weight the QM
> probabilities for the various worlds by the measure of observations in each
> world (crudely, by the amount of intelligent life, or the number of
> observations, or the number of observers, but these are only approximations).
> Then there is the trade-off between the presumably lower QM probabilities for
> worlds with less life and the increased weight of such worlds when one
> randomizes over observations rather than over worlds, so I suspect that random
> observations would tend to occur mostly in fairly fecund worlds (though I still
> would not be surprised if "fairly fecund" still means less than one
> civilization, on average, within a random region as big as our readily
> observable part of the universe, e.g., within 10^10 light years).
>
> Thus I would claim that both many-worlds QM and the anthropic principle
> (when applied in the form of Vilenkin's "principle of mediocrity," or in the
> form of the "typicality" or "conditional aesthemic principle" outlined in my
> quant-ph/9506010 or, in briefer form, in Int. J. Mod. Phys. D5, 583 (1996)
> (Ref. 9 of my new paper quant-ph/9904004) are in principle observationally
> testable. Of course, it would be interesting to be able to contrast the
> predictions one would get from Vilenkin's and my hypotheses from those one
> would be able to get from your hypothesis of maximizing the number of black
> holes, and if you have any comments on how to do that, I would find them
> interesting.
>
> Best wishes,
>
> Don
>
> P.S. One other comment I did want to make regarding Machian ideas of you and
> of Julian Barbour is that absolute acceleration and rotation do not seem to be
> explained in a 3+1 split of spacetime into a stack of spaces that are not glued
> together, but to me they do seem to be explained in a relativistic view of a
> spacetime as a 4-dimensional entity. In the latter view, classical particles
> are not merely characterized by points in space, but rather by worldlines
> through spacetime. The spacetime metric gives the intervals between various
> points along those worldlines and thus allows one to distinguish between an
> unaccelerated worldline and one that is accelerating. Thus it seems to me that
> it is making the background for particles a 4D spacetime rather than just a
> sequence of 3D spaces, and putting on a metric (actually an equivalence class
> of metrics under diffeomorphisms, so one does not have to assign any absolute
> meaning to individual points, but only to the metric relations between them)
> then makes geodesics preferred.
>
> So when you write on pp. 231-232, "Ultimately there must be no meaning
> to our rotqtion, except the relative motion between us and the rest of the
> universe," I can only agree if "the rest of the universe" can mean simply the
> local spacetime-cum-metric (or maybe a certain set of local geodesics of this
> spacetime, if it is viewed as easier to get the relative rotation between us
> and a set of geodesics than between us and spacetime itself); it need not have
> anything to do with distant galaxies.
>
> Or, to put it another way, in the approximation of classical particle
> motion as worldlines within a classical spacetime-cum-metric, there is indeed
> an absolute spacetime, though this must be seen as a spacetime-cum-metric
> modulo diffeomorphisms, so I am not claiming an absolute specification of which
> points are which within the spacetime, but only (in the assumed approximation)
> an absolute specification of the metric relations between whatever points are
> considered. (This is like saying that the surface of a particular apple has an
> absolute shape, which need not imply a preferred choice of points or
> coordinates on this 2D surface.)
>
> Thus I would disagree with your last sentence on page 239, "It is, at
> last, no longer sensible to speak of a universe with only one thing in it." At
> the classical level, one can imagine a spacetime-sum-metric with a single
> particle geodesic worldline in it, and this seems to me perfectly sensible
> (though not, of course, consistent with our observations of our universe).
>
> Of course, I do agree with you that when one goes to the quantum
> theory, one no longer has a single absolute spacetime. One might instead have
> a path integral with infinitely many spacetimes-sum-metrics, or maybe (e.g., in
> superstring/M theory) one might have something even radically more different.
> But I am just objecting to the claim that one lost an absolute spacetime at the
> classical level when one considers rotation or when one goes to GR. (I
> wouldn't say GR makes spacetime any less absolute than SR, but it just makes it
> non-flat in a way that obeys Einstein's equations, a way that is not determined
> purely by Einstein's equations but which also depends on initial or boundary
> conditions).
>
> This is not to say that I believe that the quantum world is any less
> absolute (it is quite absolute in my many-worlds view), but just that it does
> not have a single unique absolute spacetime.
>
> I could go on and on, but I don't have the time just now. But at least
> this shows that I found your book quite stimulating.
>
>
>
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Received on Tue May 11 1999 - 12:19:14 PDT