- #316
tom.stoer
Science Advisor
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Hi, I stepped out for a while, but I would like to come back now.Dmitry67 said:So, the laws are identical, but initial conditions are different? If Universe is infinite, all combinations must happen. ...
My question was if I can create a universe with a tenth planet simply by writing down the general equations for the solar system and introducing a tenth planet in theory. You replied that this is a problem regarding initial conditions in an (infinite) universe.
Let's assume that within the MU you have several mathematical structures describing more or less our universe. As far as I understand you the different universes with - say - nine or ten planets - would belong to the SAME mathematical mutliverse but would live in different "areas" of the "many world" multiverse. If string theory is rigth then all its solutions would still belong to the same mathematical universe but live in different branches of the "many world" multiverse. But If I introduce another system like "game of life", then I would have to refer to the mathematical multiverse (I guess game of life is not a vacuum of string theory :-)
Looking at the "game of life" it serves as a toy model. It can either be described by a (completely Goedelized) mathematical structure and it would therefore be an own universe. Or it can be simulated by computer programs within our universe, therefore it can be seen as a substructure of the mathematical structure being our universe. Therefore within MUH we have the situation that mathematical structures can be own universes, or they can be substructures of universes.
Now we can look at the "game of live" from a third perspective. It can serve as a model for a universal Turing machine. Now having said that we remember that a universal Turing machine is able to simulate all other Turing machines. Therfeore game of life is able to simulate a large class of universes.
That means that a universe can exist on its own or it can be simulated by another universe. Within the universe everything looks identical (the structure is the same), but from the outside it looks different. Whereas the abstract structure can exit w/o any context, the simulated structure lives in a certain context. That means that we can construct an infinite tower of universes containing (simulating) each other.
But as any mathematical framework shall be free of any baggage, we must identify all structures with a certain kind of "algebraic isomorphism". So we must identify the Turing machine universe with the "game of life" universe.
Now let's assume for a moment that our universe is computable. Then we could (must!) identify it with a certain Turing machine or with a universal Turing machine + certain input. But then you have to explain why our universe looks so different from a Turing machine - or "game of life"! Of course I can easily escape this reasoning by giving up the idea that our universe is computable. So the other conclusion would be that our universe is not computable. Having concluded that our universe is not computable we immediately know that our universe is either (Goedel-)incomplete or inconsistent. As our universe exists and should therefore be consistent it must be incomplete. That means there are true statements which cannot be proven within our universe.
Now what does it mean for a mathematical structure to exists? Do we need a proof? What are these structures that exist within our universe w/o having the ability to be justified by our universe?