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.”