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How many believes in Quantum Immortality ?

  1. Yes

    4 vote(s)
  2. No

    29 vote(s)
  3. Maybe

    11 vote(s)
  1. Nov 17, 2007 #1
    How many believes in the thought experiment on MWI's Quantum Immortality that Max Tegmark put forth?

    I think it's bull****, otherwise why hasn't he killed himself to prove it?
  2. jcsd
  3. Nov 17, 2007 #2


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    Because it is an interesting thought experiment, but a rational being can't choose to perform it. This for two reasons.

    First, if MWI is false and he dies, then he dies, and since he doesn't know whether it is true or false, then this is enough to rationally prevent him from performing the experiment.

    Second, if MWI is true, by conducting the experiment he would severely pruning off his tree of successors in the multiverse, rationally causing pain to many hims where the experiment would half succeed, and causing sorrow to many families and friends, thus proving his own stupidity in almost all universes.

    However, as a thought experiment it is perfectly valid, since it is a purely formal argument and we don't care about the moral consequences in that case.
  4. Nov 17, 2007 #3
    so if MWI were to be true, immortaliy comes with it? its like u CANNOT ****n die even if u wish to? ever?

    wowwww that is one sad theory put forth... I Doubt this will do any good to humanity
  5. Nov 17, 2007 #4
    MWI is not true, and just as with Schroedinger's cat, decoherence explains why the cat/suicidant will end up in a macroscopic state, either alive or dead but not both.
  6. Nov 17, 2007 #5
    But, isn't that the Copenhagen interpretation?
    Doesn't this state consciousness has something to do with anything and goes against objective reality?
    here i gotta take stand with einstein and doubt that...

    Objective reality is obviously primary
  7. Nov 17, 2007 #6
    No, the Copenhagen interpretation was laid out long before decoherence was understood. Now we know that quantum states collapse when they interact with a macroscopic temperature reservoir, nonsense about consciousness is not necessary.

    As far as objective reality, I think you mean to stake you claim for determinate reality i.e. the idea that there are particles with simultaneously definite positions and momenta, regardless of what limits QM sets on our knowledge.

    I'm glad you agree with Einstein since in 1935 Einstein said he found a paradox that disproved quantum theory. The thought experiment showed that QM predicted the outcome of a certain experiment to be absurd, to deny determinate reality. Einstein's goal was to show that QM was incomplete, but when the experiements were actually done in the 1980s they showed that in fact Einstein was wrong and QM was right.
  8. Nov 17, 2007 #7
    So in layman terms you are saying you believe in the Copenhagen interpretation?
    What does QM being "right" means? we got like 15 different interpretations , which one is the "right" and most sensible?
  9. Nov 17, 2007 #8
    the implications of parallel universes must be accepted whether or not they challenge the aesthetic sensibilities of a bald ape- causal systems evolve algorithmically- which means they sort through all the possible configurations to generate complex states- they can't magically produce one history- that would be like a factorization program magically guessing the factors of a very large number- if you live in a causal world with consistant rules and structures then you know that there are parallel universes- and in some of them a version of you always survives-

    now what the most likely sort of survival states likely to be observed are is another issue
    Last edited: Nov 17, 2007
  10. Nov 17, 2007 #9
    setAI i've lingered around this forum for awhile and I see you are A STROOONG defender of MWI.
    There is no emperical evidence or data for this so, maybe you are the bald ape with a problem with death and hangs onto MWI for immortality wishes like a christian there is life after death?

    No trying to start a feud here and start arguement, just saying THERE IS NO EMPERICAL EVIDENCE of it.
    So whether you believe it or not, you do not know which is right.
    I can doubt it and you be right, you can believe it and I be right.

    To put it simple: Are you so convinced of MWI that you'd be willing to try the Quantum Suicide Experiment? (not recommending it) just hypothethically are you that certain?
    Last edited: Nov 17, 2007
  11. Nov 17, 2007 #10
    I have gone on record that I agree with David Deutsch that the MWI is the only legitimate interpretation of QM- and that all empirical evidence for QM is empirical evidence of the MWI- as all other interpretations merely ignore the other outcomes after measurement with no mechanism for 'wavefunction collapse' or description of what happens with those outcomes with decoherence- and I also agree with Deutsch that quantum computers PROOVE parallel universes- and that proof will be widely accepted when a qc performs a calcualtion with more information than is in the observed universe-

    also the notion that there is no empirical evidence for parallel universes is I feel a POV error from physicists that has baffled computer scientists and mathematicians where these ideas have been widely accepted for decades- there are very rigorous mathematical proofs which show that casual sets must sort through states algorithmically- and that show all possible states are realized somewhere in the computation- therefore the anthropocentric concept of a conscious observer dying is logically impossible- since the observer IS a configuration of matter- it is endlessly repeated in sections of the causal structure- any disolution of that configuration in a local sub-routine of the algorithm appears elsewhere by definition-

    I firmly agree with Deutsch/ Martin Rees/ Max Tegmark/ Nick Bostrom/ Jürgen Schmidhuber/ Marvin Minsky/ and many others who have extensively shown how these are unavoidable realities of living in a world with rules/time/locality/ and causality-

    I have said many times that a claim that an observer can 'die' is a claim that the observer is a magical entity made of fairy dust and beyond the laws of physics because it is unique and some godlike demon edits the universe preventing that very discrete configuration of matter from ever being built again anwhere in any universe- but evidence shows that an observer is a discrete ordered configuration of matter- and as such it is repeated throughout the multiverse of the entire casual structure of the universe by definition- quantum immortality is the rational analysis of the logical structure of causality- death is a mystical idea- yet the reverse seems to be the perception of many physicists [at least in America- the UK is rapidly accepting these ideas]
    Last edited: Nov 17, 2007
  12. Nov 17, 2007 #11


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    This is wrong. MWI is not proved true nor untrue. Also, decoherence is the very mechanism used in MWI to explain the emergence of splitting worlds from the Schrödinger evolution.
  13. Nov 17, 2007 #12


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    I doubt there are many people who believe in MWI primarily because they like the idea of quantum immortality. The main reason to favor the MWI is its conceptual simplicity--the Copenhagen interpretation requires you to treat measuring-devices in a fundamentally different manner than the quantum systems they measure, even though the measuring-devices themselves are really just large collections of interacting quantum particles. The MWI allows you to treat all systems on equal footing, giving you an objective picture of the universe in which the interaction of a measuring-device with a quantum system obeys the same fundamental laws as the interaction of individual quantum particles or groups of particles in isolation. As a side benefit, it also allows you to explain the results of experiments involving quantum entanglement without the need for any faster-than-light effects (no need for nonlocality).

    As for quantum immortality, this is by no means assured even if you believe the MWI, it really depends on your philosophical views on consciousness and personal identity. For example, leaving aside the MWI, if I step into a Star Trek style teleporter that takes aparts all my atoms in one spot and rebuilds the exact same pattern of atoms in another, would you say that the person who steps out at the other end is the "same person" as the one whose atoms were taken apart, or just a "copy" with false memories, with the "original" having died? Physics can't give you an answer to this sort of question, if there even is any "true" answer. But if you accept in this sort of example that your consciousness can jump along with the pattern of your body, and that your consciousness could even "split" if the teleporter created multiple versions of the same pattern of atoms, then in that case the idea of quantum immortality seems pretty natural.
  14. Nov 17, 2007 #13
    Who needs an ad hoc collapse of the wave function now that the theory of decoherence has been laid out? Just because Bohr held the view of ad hoc collapse doesn't make it part of the Copanhagen interpretation, or at least it shouldn't if there is to be any continuing debate at all.

    When I say that MWI has been disproved, I did not realize that people still held on to the idea of determinate classical states after so many EPR experiments have been done.
  15. Nov 17, 2007 #14


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    Maybe you're talking about the Copenhagen interpretation, and not MWI. MWI has no collapse.
  16. Nov 17, 2007 #15


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    I'm pretty sure decoherence doesn't explain why a quantum system would behave classically if there is nothing external interacting with it. The idea behind decoherence as I understand it is that if you have a small system A and its external environment B, and you treat them both using the laws of QM, then as A interacts with B, it becomes entangled and you can no longer see any interference effects in A on its own, they become spread throughout the combined system A+B. This is sort of analogous to the way that if you have 3 photons emitted together and thus entagled with one another, you will see no evidence of entanglement if you look at any pair of photons--the statistics of any pair will look just like that of unentangled photons--but you will see the correlations characteristic of entanglement if you measure all three together. As http://www.ipod.org.uk/reality/reality_decoherence.asp [Broken] puts it:
    If you look at the "reduced state" of the smaller subsystem A, apparently interactions with the external system B will cause it to go from a "pure state" to something close to a "mixed state", where you assign different probabilities to different states in a classical way, and you can assume that the probability of getting result X when you make a measurement can be broken down into a weighted sum like P(getting X) = P(getting X if system is in state #1)*P(system in state #1) + P(getting X if system is in state #2)*P(system in state #2) + P(getting X if system in state #3)*P(system in state #3) + ... (in a superposition of states you can't reason this way--that would be like assuming the probability a photon in the double-slit experiment is found at position x can be broken down into the probability it lands at position x if it goes through the left slit + the probability it lands at position x if it goes through the right slit, which would fail to take into account interference effects). However, if the combined system A + B is not modeled as interacting with anything external, then it'll still be in a giant superposition of very different macroscopic states, like Schroedinger's cat, so this doesn't really help with the problem of explaining why macroscopic systems behave classically without introducting some external system to measure or interact with them (which is a big problem in quantum cosmology if you want to treat the entire universe using quantum laws).

    See the comment from vanesch on this thread:
    Likewise, this comment from sci.physics.research says:
    Greg Egan also has a good set of pages on decoherence starting here.
    Last edited by a moderator: May 3, 2017
  17. Nov 17, 2007 #16
    There's an easy way to test this theory without hurting anyone: replace the gun with a paintball gun and replace the words "not killed" with "not covered in paint".

    Unfortunately, even if the experiment worked the only people who would know about it would be the ones in the world that the paint-free experimenter ended up in. Everyone else would see someone with a big dry-cleaning bill to look forward to.
  18. Nov 17, 2007 #17


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    It would not work with the paintball, since in that case the probabilities to observe clean clothes would be the same for both theories.
  19. Nov 18, 2007 #18
    we are going to need beefy computers [hypercomputers] before we can ever really start mapping out the Born probability space of macro scale systems- it involves hierarchies of cantor sets and vast algorithmic complexity -
  20. Nov 18, 2007 #19


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    Hm, probabilities for the quantum paintball gun's outcomes are rather easy to compute; each shot is clean with 50% probability, and messy with 50% probability.
  21. Nov 18, 2007 #20
    Even if we have no explanation for QM, that doesn't mean it can't be right. We know that QM has a great predictive value for experiments, and so an interpretation for why this works isn't necessary for it to explain reality.

    Maybe you should just stop caring about why QM is the way it is. It won't change the usefullness of QM in your life (assuming it even plays a role) and then maybe you can stop freaking out over some currently unfalsifiable idea.
  22. Nov 18, 2007 #21
    I don't agree with Tegmark that MWI implies immortality in his suicide experiment. I think that it a fallacy of just focussing on a particular sector of the entire multiverse and then naively defining the subjective time evolution. If you look at the entire multiverse, then all your copies just exist and you have an a priori probability of finding yourself in some particular state. This a priori probability of finding yourself to be that copy who has survived N suicide experiment decays exponentially for N ---> Infinity
  23. Nov 18, 2007 #22


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    But since one has a zero probability to find himself in a dead state, so it follows that "one" has a 100% probability to find himself in the surviving copy alive state.
  24. Nov 19, 2007 #23
    This is how I think we should analyze the problem.
    In the multiverse, all your possible states exist a priori with some a priori probablity. If |s_n> are the states in which you can find yourself in, and |psi> is the wavefunction of the multiverse, then the a priori probablity of finding yourself in |s_n> is
    Q_n = <psi|P_n|psi>/<psi|P|psi>

    where P_n = |s_n><s_n| I

    is the projection on the observer state |s_n>, I is the identity operator acting on the rest of the wavefunction and P is sum over all the P_n. So, what I'm saying is that at any moment you should think of yourself as being randomly sampled from all the possible states that can represent you. These states exist a priori in the multiverse. The definition of what is a bona-fide version of "you" is arbitrary and defined by the |s_n>

    This is time independent if the wavefunction of the entire universe is in an eigenstate of the Hamiltonian. We can just as well put the energy eigenvalue equal to zero, so that H|psi> = 0. Any nontrivial time dependency of the wavefunction would make the a priory probabilities depend on some global time coordinate which is unnatural.

    Now probabilities are invariant under unitary transformations. Since the operator Exp(-i H t) leaves |psi> invariant, we have:

    Q_n = <psi|P_n|psi>/<psi|P|psi>=

    <psi|Exp(-i H t)P_nExp(iH t)|psi>/<psi|P|psi>

    Note that P_n does not commute with Exp(iH t), otherwise the observer would find himself in a stationary state, so this argument is not like saying that
    P_n = Exp(-iH t)Exp(iH t)P_n = Exp(-iH t)P_nExp(iH t)

    If we put |s_n(t)> = Exp(-i H t)|s_n>, then

    Exp(-iH t)P_nExp(iH t) = |s_n(t)><s_n(t)| I

    And this just implies conservation of probability for the observer under time evolution provided |s_n(t)> is still in the linear space spanned by the |s_n>. However, this is not the case in suicide experiments. So, the probability of finding yourself alive after the suicide experiment is less than before.
  25. Nov 19, 2007 #24
    Perhaps you could you explain further? The only difference with my suggestion is using a paintball instead of a bullet. How would that change the probabilities?
  26. Nov 19, 2007 #25


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    The reason it doesn't work with a paintball is that the argument for quantum immortality specifically depends on philosophical assumptions about your subjective probabilities of experiencing one branch vs. another--specifically, it is assumed that you are never going to experience a branch where you don't exist. A bullet to the head causes you to stop existing in the branch where it happens, a paintball doesn't.

    To see why some might consider this plausible, consider, instead of a branching multiverse, a Star-Trek-style transporter/duplicator in a single universe, which can deconstruct you and reconstruct exact copies atom-by-atom in distant locations (assuming the error introduced by the uncertainty principle is too small to make a difference--if you don't want to grant that, you could also assume this is all happening within a deterministic computer simulation and that you are really an A.I. program). Now suppose this duplicator recreates two identical copies of you, one in Washington and one in Moscow. As you step into the chamber, if you believe it's meaningful to talk about the first-person probabilities of different possible next experiences, it would probably make sense to predict that, from your point of view, you have about a 50% chance of finding yourself in Moscow and a 50% chance of finding yourself in Washington.

    On the other hand, suppose only a single reconstruction will be performed in Washington--then by the same logic, you would probably predict the probability of finding yourself in Washington is 100%. OK, so now go back to the scenario where you're supposed to be recreated in both Washington and Moscow, except assume that at the last moment there's a power failure in Moscow and the recreator machine fails to activate. Surely this is no different from the scenario where you were only supposed to be recreated in Washington--the fact that they intended to duplicate you in Moscow shouldn't make any difference, all that matters is that they didn't, so you should have a 100% chance of finding yourself in Washington after the reconstruction. But now look at another variation on the scenario, where the Moscow machine malfunctions and recreates your body missing the head. I don't think it makes sense to say you have a 50% chance of being "killed" in this scenario--your brain is where your consciousness comes from, and since it wasn't duplicated this is really no different from the scenario where the Moscow machine failed to activate entirely. In fact, any malfunction in the Moscow machine which leads to a duplicate that permanently lacks consciousness should be treated the same way as a scenario where I was only supposed to be recreated in Washington, in terms of the subjective probabilities. If we extend this conclusion to the situation of "natural" duplication due to different branches of a splitting multiverse, the subjective probability should always be 100% that my next experience is one of a universe where I have not been killed.

    As I said, all this depends on making certain philosophical assumptions about there being some "real" truth about subjective probabilities--it's certainly not a direct consequence of the MWI, someone with different philosophical views about consciousness might accept the MWI but reject quantum immortality.
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