Thought-experiment August: (3) Would it matter if you switched to an identical universe?

Suppose that you are captured by aliens who can travel to other universes. Furthermore, they tell you they are going to drop you into a different universe but, and here’s the catch, it is identical to this one. And by identical, I mean in every way, including its history. When you arrive, you find yourself in exactly the same time and place as when the aliens abducted you. There are your socks lying on the floor where you left them. All your books are there, earmarked and underlined with notes, just as if you were the one that marked them. There is your spouse/significant other welcoming you home—kids, neighbors, world, everything is exactly the same. Your photo albums are there with all your pictures of your life just as you lived it. In fact, the aliens tell you that this world is identical to yours in every way, except there is a trout in northern Canada that is 0.5 cm smaller in this place than the same fish in your old universe. That is the only difference, including the neural state of every living being in this universe. Your spouse loves you here and has had the identical history with you that your spouse had back home.

But you know this is not really your spouse. These are not really your parents. These are not your kids. Those are not your socks. This is not your universe (which is still out there somewhere). Yet, all your relationships are in place, just as you left them.

Does it matter? Would you mourn the loss of your other life?

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26 Responses to Thought-experiment August: (3) Would it matter if you switched to an identical universe?

  1. Joseph Smidt says:

    I have a few comments:

    1. Great thought experiment. I’ll even add to it a little and say that if we trusted the current quantum cosmology models that best describe our universe, we would conclude there are in fact a large number (if not infinite) of identical universes to ourselves in addition to every physically possible universe. Many cosmologists view this as a sign that new physics is needed to cancel out this craziness, but other muse: “what if the models that describe our universe so well really can be extended that far? Maybe there is something to all this.” You can find all the peer reviewed physics articles relating to this stuff here: I will also blog about this in the future.

    2. How the universe turned out to be exactly the same, minus a fish’s size is a really interesting question in itself.

    3. I would mourn the loss of my other life, but ultimately I think I would get through it and realize this is my lot in life.

    4. However, if everything was the same other than a fish’s size in reality I would convince myself that the odds are more likely I just mis-remembered the correct size of the fish and had some type of hallucination than the alternative.

    5. But again, great thought experiment and I will have to think more about this.

  2. Jeff G says:

    Or what if the aliens tell you all these things and then put you right back in your same old life?

    Since this possibility is FAR more probable than that of them telling me the truth, this is what I choose to believe in both cases, and live out my life accordingly.

  3. S.Faux says:

    Hmmm, everytime I go fishing, the fish get smaller. Now I know why.

  4. SteveP says:

    Jeff G. We’ll stipulate they are telling the truth and you know they are.

  5. Geoff J says:

    And by identical, I mean in every way, including its history.

    Well this would prove that there is no such thing as libertarian free will. As such we would be proven to all be puppets of either God or the great causal chain. Therefore I would resign myself to nihilism and not care.

  6. Left Field says:

    Wasn’t there an episode of Pinky and the Brain like this?

    Will I be missing back home or will my double from the other universe take my place?

  7. Joseph Smidt says:

    A string landscape post just for you. (I told your post would have me thinking all day. Great thought experiment.)

  8. ujlapana says:

    What happened to the other me? Did identical aliens exist in both universes simulaneously?

    I think I would assume I’d eaten a bad piece of meat or a bit of mustard and shake it off. Identical-universe-crossing aliens are too much to believe, no matter how noetic the experience may have felt at the time!

    It is curious to wonder how the fish ended up a different size…is the new universe slightly deficient in mass compared to your original? Surely they will diverge in short order, so no going back! Incredible to think that the slight mass difference at the Big Bangs ended up completely concentrated in one Canadian fish billions of years later….

  9. Jacob J says:

    ujlapana asks a good question and makes some compelling points.

    It seems to me that your final questions make assumptions that undermine certain aspects of the thought experiment. You said everything was exactly the same, so I what is your basis for saying at the end that this is “not really your spouse?” It seemed from your thought experiment that it is really my spouse. Indeed, I don’t think that within the confines of your thought experiment you can support your claim that it is not my spouse, parents, kids, and socks.

  10. Clark says:

    In my opinion our intuitions aren’t suited to such questions simply because we don’t have the realm of experience with such scenarios.

  11. Mark D. says:

    The premise of the question is that everything is exactly the same, a couple of details excepted.

    The proper answer is you don’t care and can’t care. The reason is that not only can’t you tell any difference in your friends and family, there isn’t one.

    Assuming you except the premise of course, and the premise is realizable.

    With regard to history, as a matter of fact the history is not the same, the new world was just recently cloned from the old one. As such the claim that the history is the same is a logical contradiction. The historical evidence can be the same, of course.

  12. Mark D. says:

    My apologies, I misread the premise. The proper answer is similar to Geoff J’s – you realize that LFW is wrong and debate within yourself whether to become a Calvinist or an absurdist.

    Of course that doesn’t mean you think that your friends and family are different from the the ones you left. They are identical and have been from the day they were born, right? The whole notion of quiddity violates the premise in any case.

  13. Mark D. says:

    It is too late. “Haecceity” rather.

  14. Cap says:

    I would like to know where the other me in this universe I was dropped into went.

    I think at first I would have a hard time accepting the fact that I was not with my real family and friends. Despite the fact that they act look and have the same history, if (as this experiment dictates), I have an absolute knowledge that I am in a different place I think it would matter and I would ‘mourn the loss of my life’.

    What’s more, I cannot tell anyone about it because they would never believe me. It would be a hard adjustment that I think could cause the loss of some relationships.

    The thing here that gets me is that you have an absolute knowledge of it somehow. This is what would cause me to distance my self from everyone.

  15. Last Lemming says:

    If I was the Inuit destined to eat that fish, I would mourn the fact that is was not a little larger. Otherwise, the familiarity would quickly overcome any sense of loss and I would carry on as normal.

    And I would not bother debating whether to become a Calvinist or an absurdist, since I can’t influence the outcome of that debate.

  16. Bro. Jones says:

    Does that mean I would be committing adultery by having sex with the “not my spouse from my universe but still my spouse ” woman living in my home?

  17. barcelo says:

    bro jones – if you are married then you probably stopped having sex a long,long time ago- and so the premise that everything is completely identical sadly renders your question irrelevant.

  18. SteveP says:

    By stipulation, this is not your universe. Identically the same, does not mean identity.

    Remember this is a thought experiment, the plausibly of this has no bearing. We don’t have intuitions about riding on light-waves either (Enstein’s famous thought-experiment), but we learn useful things.

    I think it would affect my relationships. CAP is right, you could tell no one, but knowing this for me would have some after effects. The point about committing adultery was very interesting, because technically under the terms of the experiment you would be!

  19. Geoff J says:

    Re: Adultery

    Since it would prove there is no LFW then there is also no moral responsibility so it wouldn’t matter anyway (nevermind the fact that you couldn’t choose anything other than your fixed fate to begin with)

  20. Allen says:

    Interesting problem and interesting comments.

    If we assume the thought problem applies to the physical world but not to the spiritual world, that is to spirit matter and the spirit offsprings of God, then the new universe is just a clone of my universe. There is a parallel to this in computer technology. When I install software on my computer, a log of the events is created, and this log is used to uninstall the software. The new universe could have been created via the events in a “log”.

    On the other hand, if we assume the thought problem also applies to our spirits, then everyone has the same spirits they had in the old universe, and the new universe can be considered as if it were our universe, and we can continue living our lives as we were doing.

    One point that I didn’t see discussed in the comments is *why* the fish is smaller. I don’t understand evolution very well, but I’m guessing that the smaller fish means there was a difference in the evolution of the new world compared to the old world. This implies that the new universe is not a clone of the old universe and that my progression in the new universe could be quite different than my progression in the old universe.

    If I knew in some way that it was impossible for me to ever go back to the old universe, I would forget about that universe and continue living my life in the new universe. What is, is. If I can’t go back, the old universe ceases to exist, except in my memory, and only the new universe exists to me. I tend to focus on the immediate, and I don’t think it would be difficult for me to forget the old universe.

  21. barcelo says:

    On a more serious note re adultery:

    comments so far have concentrated on our own decision, whether we speak up or get on with a new life.

    If you decide to put the past behind you and forget about your previous universe, well great but doesn’t your ‘new’ wife have the right to know that despite appearances, you are not the same person sharing her bed as the night before.

    in fact, all your existing relationships become fraudulent right?

    The best thing you could do is stay in new universe but start a brand new life. Remember, you’re not abandoning your family because they’re back in the original universe. If you feel sorry about abandoning these new individuals then remember it’s really not your fault, they’re complaining to the wrong guy.

  22. SteveP says:

    I find it interesting that even though these people have technically no claim on me, I would know them better than anyone else in the world. For example, I would know very clearly what this person, who is exactly like my wife, but not her, feels and thinks as well as I know my wife. I would understand how hurt she would be if left. I’m not sure I could walk away.

  23. FireTag says:

    Given that there are serious cosmological models of reality that predict exactly such universes do exist in an infinite spacetime, the only thought experiment is the travel part.

    What is the relationship between the spirit associated with you and the spirit associated with “you prime”? Why does a spirit care about the location of its body in spacetime? More interestingly to me, how does God view the relationship between the spirits associated with the two bodies?

    When I first learned that copies and variants of universes existed in one form or another throughout QM, I started reading the words about “other earths” in the vision of Moses in an entirely new light.

    Going from an earth-centered cosmos to one that was not earth-centered changed theology. Going from a single-earth cosmos to a multi-earth cosmos will, I suspect, change it again.

  24. Jeff G says:

    Sorry for the late response, but you are going to have to tell a REALLY fancy story about how I could ever “know” that the aliens aren’t lying to me. I can’t imagine any evidence for their honest that could ever out weigh my doubt regarding the scenarios veracity.

  25. SteveP says:

    Jeff G, I wouldn’t believe them either, but for the purposes of the thought experiment, you do believe them, and your beliefs are true i.e., you really are in another universe.

  26. Rameumptom says:

    Given I’m in a different, yet identical universe, could I assume that I have a different, yet identical God?

    Would my religion and Church leaders view me as being sealed to the woman and children? If yes, then what’s the problem with continuing on as things are? You have no way to return to your previous life, and nothing but a small fish has changed. As long as your identical other is not around, you would be expected to fulfill his responsibilities towards the identical family. Maybe you could have a renewal of vows with the wife, as a romantic thingy?

    Brigham Young was very practical and pragmatic when it came to polygamy and polyandry. He once allowed a woman to marry a second husband for time, in order to bear children for her incapable first/sealed husband. They conceived several children together. I don’t see how this would be much different.

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