A few years ago I posted a speculation about Harry Potter universes, from the Schmidhuber perspective. Schmidhuber argues that the reason we don't see such a universe is that its program would be more complex, hence its algorithmic-complexity measure would be less. Such a universe would basically have natural laws identical to what we see, but in addition it would have exceptions to the laws. You wave a wand and say "Lumino!" and light appears. (Here I am taking the Harry Potter name rather literally, but the same thing applies to the more general concept of universes with magical exceptions to the rules.)
You could also argue, as Wei does, on anthropic grounds that in such a universe the ease of exploiting magic would reduce selection pressure towards intelligence. Indeed in the Harry Potter stories there are magical animals but it is never explained why their amazing powers did not allow them to dominate the world and kill off mundane creatures long before human civilization arose. I suggested that the Schmidhuber argument has a loophole. It's true that the measure of a simple universe is much greater than a universe with the same laws plus one or more exceptions. But if you consider the set of all universes built on those laws plus exceptions, considering all possible variants on exceptions, the collective measure of all these universes is roughly the same as the simple universe. So Schmidhuber gives us no good reason to reject the possibility that our universe may have exceptions to the natural laws. If we do live in an exceptional universe, we are more likely to live in one which is only "slightly" exceptional, i.e. one whose laws are among the simplest possible modifications from the base laws. Unfortunately, without a better picture of the true laws of physics and an understanding of the language that expresses them most simply, we can't say much about what form exceptions might take. We know that they would be likely to be simple, in the same language that makes our base laws simple, but since we don't know that language it is hard to draw conclusions. Here is where the anthropic argument advanced by Wei Dai sheds some light; one thing we could say is that these simple exceptions should not be exploitable by life and make things so easy as to remove selection pressure. So this would constrain the kinds of exceptions that could exist. Ironically, waving a wand and speaking in Latin would indeed be the kind of exception that would not likely be exploited by unintelligent life forms. So purely on anthropic principles we could not fully rule out Harry Potter magic. But the complexity of embedding Latin phrases in the natural laws would argue strongly against us living in such a universe. Hal Finney --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to everything-list@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list -~----------~----~----~----~------~----~------~--~---