Jerry Clark, <[EMAIL PROTECTED]>, writes: > More relevantly, it is posulated as highly likely that, starting with > a random Life formation, SAS's will evolve of their own accord. One > proves this by showing that our UTM is also a universal constructor > (can take a coded blueprint and build out of it a machine at least as > complex as itself). UTM is also a universal destructor and therefore > mobile. Eventually you get evolution and SAS's.
There are difficulties with this, due to the difficulty of a formation defending itself against noise from outside. The Life universe does not seem to lend itself to constructing barriers. No one has ever built a wall that could withstand random Life noise. Of course, the same thing is true in our universe. There is no wall that can withstand everything that can be thrown at it (ultra-high temperatures, relativistic collisions, etc.). Life has evolved in special regions which are relatively gentle. Now, perhaps if the Life universe was big enough there would be regions that just happened to be formed of islands large enough to form living entities, surrounded by empty spaces so that these entities would not be destroyed from the outside. But these would be very rare, without any systematic large-scale phenomena to self-organize biospheres as we have in our universe. > Such 'Life' evolution raises an interesting question: These SAS's > would build universities and study mathematics, computer science and > physics. Some J.H.Conway of the Life universe would discover the amusing > and diverting Life game, and start discovering gliders, glider guns, > space rakes etc. Sooner or later a physicists would hear about this new > development and the realisation would be made that their universe *is* > a Life simulation. Such a discovery would of course revolutionise the > study of physics for these SAS's. This is simply an analog to what is happening in our own universe, as we discover regularities and create models of fundamental physics. Newtonian mathematics was found to apply with tremendous accuracy to the basic behavior of physical objects, and this has provided insight into the possible nature of the universe. > More interestingly still: when are *we* going to discover some CA or > similar which turns out to be *our* universe? In my lifetime I hope. There is nothing special about a CA; any set of mathematical laws which fully describe our universe. What you are really asking is when or whether we will find a fully unified and universal physical theory. Whether this theory can be expressed in a formulation based on CAs is insignificant in my opinion. In particular this would shed no light whatsoever on the likelihood that we are in some sense actually part of a computer simulation. Computers can simulate any mathematical or logical structure, and there is nothing special and CAs. Hal Finney
