When I lived in L.A., working on casual web games with Nate, we had a semi-regular game night with Todd and a bunch of cool people from the area (Will, Robert, Tim, Daina, others). Often – since some board games have long turns and thus long downtimes for the nonactive players – we would have philosophical and existential conversations about random stuff. We talked about economics, altruism, determinism, the nature of “good” and our philosophy regarding current events. It was awesome, and I miss it. :-/
But so anyway, the following thought “puzzle” came up during one of our discussions:
Imagine that there is a universe, call it Prime, that is an exact duplicate of ours in every way. That is, you-prime (hereafter, you’) exists in that universe, is doing exactly what you are doing now, and for every other person, object and state, the same prime-equivalent exists in the Prime universe.
Now imagine that at the same moment, in front of you and in front of you’, a portal opens to a third neutral universe. If you and you’ both step through (we can assume that if one of you does, the other will), how do you communicate with your doppleganger? As presented, you and you’ start talking at the same time, have the same ideas about breaking symmetry, even know that it might be difficult and can form (independently-but-together) a plan. Can the symmetry be broken?
At its heart, this is a question about a deterministic universe. (For my physics-y friends these days, I generally add an assumption that the third neutral universe is deterministic, so that the question is entirely about us and Prime [which is really us].) That is, given the fundamental assumption that you and you’ are identical, you will be forced as you consider the “puzzle” to conclude that symmetry can’t be broken. But if it bothers you enough because of the implications, you will argue with the assumption and then the fundamental question is the discussion:
How exact a copy can Prime be of our universe? If you could know the starting conditions of everything, could you reliably predict everything as it evolves? I personally don’t believe the universe is deterministic in this way, but I think regardless, we are once again saved from our (my?) terrible need to know by quantum mechanics which says, in essence, “you don’t get to know. Neener neener.”
#1 by Mike on 2010/01/22 - 7:50 AM
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That is why I have an unspoken agreement with all of my other selves to never walk through doors to other universes.
I’d recommend you do the same.
Mike
#2 by Monty on 2010/01/22 - 10:34 AM
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I’ve actually considered this problem. I figure the most important thing to do is vary the stimulus each copy of me receives, so that after a day or so, we’ll have sufficiently different instincts. So if I’m facing a copy of myself, we’ll at least be looking at different backgrounds. The first step is to find a bottle or spinner of some sort and use that to determine which of us gets to speak first. Then we’ll purposely vary our environments to maximize the differences until we can reasonably talk to each other as different (albeit very similar) people.
And since I’ve already come up with this plan, if something like this should happen, both copies of me will instantly know what to do. Easy!
#3 by Kelly on 2010/01/22 - 12:24 PM
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The bottle/spinner plan is a good one. It solves the problem I have with coin-flipping, which is that each of you will think you’re “heads.” But a spinner can only be pointing toward one of you.
The tricky thing is that you’ll both try to find a spinner at the same time in the same way.
Dave, if all involved universes are deterministic, does that mean that if we each flip a coin we have in our pocket, we will get the same result forever? What if we flip our coins so they collide in midair? Er, wait, damn, then we wouldn’t know which was which, because of course we picked the same coin.
Man, this idea irritates me, because most of the common-sense ways to get around it end up getting mirrored when Prime has the same idea. It’s a good thing that I also do not believe that the universe works this way.