Is our universe simpler than a Turing universe?Another way into this question is “How would you design a universe?”. Being a software designer I would prefer a conventional digital computer, but not a Turing machine I think. (I feel uncomfortable with arguments involving grossly inefficient mechanisms. If the quest for simplicity has any validity then there is some sort of complexity budget. I admit that the 1071 particles in the visible universe suggests a substantial budget, but still insufficient for practical Turing machine programs. Some hard AI types were and are hopeful with computing element counts closer to 108.)
Here is a point that Tegmark does not make:
The universe must either have life built in or must be able to evolve it.I argue here that a Turing machine, or a PowerPC with enough RAM is almost certainly simpler than the universe we inhabit and whose rules we are still well short of knowing. On the other hand I suspect that machines as we know them are not by themselves suitable for evolution ab initio, and if we include self aware software in the package, the initial complexity investment is too great. A machine together with self aware software is probably more complex than the rules of our Universe, which just cooked up life Darwin’s way.
The Unix “proc” facility allows one program to experiment on another program in another address space and survive that program storing at arbitrary addresses and getting into infinite loops. The Keykos domain facility is simpler and easier to work with, but less familiar to most.
It is easy to provide such protection without special hardware but I don’t know if it ultimately simpler. Java aspires to just such protection. Other more interpretive systems have as well.
A great weakness in speculation such as this is lack of a clear idea of a simplicity metric. Kolmogorov complexity is one place to look. But is a 10100 life board with a random initial configuration more complex that one PowerPC chip?