Hi guys and girls, I'm sure this question has already come up many times before, but it's an important one, so I guess it can't do any harm to go over it again.
If the universe is thoroughly computational, what are the computations 'running' on? What I especially like to know is what options are discussed in digital physics. So far I have encountered only the following possibilities: (1) Mathematical platonism: all natural numbers, and all mappings between them (i.e. all algorithms), simply exist in 'Plato's heaven', including those algorithms that compute our universe. The simple non-spatiotemporal existence of those algorithms is enough to 'instantiate' a spatiotemporal world. This type of solution can be found in Tipler, Tegmark and our own Bruno Marchal. Major problem: the hard problem of consciousness. (2) Simulation by an advanced civilization: Our universe is simulated on a physical computer build by a superior intelligence. Nick Bolstrom has explored this option and found it quite probable. I don't know about that, but as a general approach to digital physics it fails. If we want to understand the physical universe in terms of computation then it is circular to postulate a physical hardware on which the computations are running. (3) Or perhaps it is not circular? This third option sees the physical universe itself as a (quantum) computer (or cellular automaton) computing its own future. Thus its present state is the input and the temporally next state is the output. Isn't this how David Deutsch approaches it? I am not very clear on this option. The major problem seems to be that you have to presuppose an initial state of the universe that itself is not the result of computation, just to avoid an infinite regress. Or you accept the regress and say the universe exists eternally (but this is problematic in light of the big bang). But then you still have to explain why the universe exists eternally. And then the explanation must still fall outside the computations going on in the universe... (4) The computations that yield our universe run on a platform that exists somewhere else, in another dimension that is principally inaccessible to us. Ed Fredkin has embraced this 'solution' and calls this other dimension simply "the Other" which has a theological ring to it. I don't like this option, but it seems to be the most straightforward one. Any thoughts or corrections? Are there some options I haven't discussed. -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
