One of the things that strikes me as most peculiar and unexpected about the universe is this: that it is apparently finite and inhomogeneous in time, yet infinite and homogeneous in space.
>From what we can tell, the universe began about 13 billion years ago and has gone through a series of phases or "ages" in which the dominant physical effects have been strikingly different. And current observations appear to indicate that the pattern will continue into the future, with our current era of matter and stars being destined to give way to low temperature and long-term effects. However at the large scale the universe shows no evidence of being finite in size. Some models predict that it should be finite, but these aren't very strong predictions given the struggles which cosmology is facing these days. And even if it is finite as inflation models predict, it is so huge that there is no real hope of distinguishing it from infinite in size. Likewise the universe appears to be roughly the same everywhere. Although there is clumpiness at many scales, there is no belief that the average density or other parameters of the universe will be different in widely separated regions. Is this something that might be predicted by a multiverse theory? It might be argued that the finiteness of (past) time is predicted by the theory, because it is questionable whether it is meaningful to have an infinite amount of computation in your past. The apparent infinitude of the spatial universe however does not fit too well, for the same reason. If the universe is infinite then it plausibly carries an infinite amount of information. This would require an infinite amount of computation. Of course most of it is outside of the "light cone" imposed by relativity, so perhaps this loophole in some ways could avoid the need for truly infinite computation. Even if the universe is finite, it does seem extravagantly large. It seems hard to justify such a size from anthropic arguments, especially the sizes predicted by cosmological inflation theories. Surely humans could have evolved in a much smaller universe, one which contains less information and requires less computation. The universe seems to contain a lot more information than is necessary for minds like ours to exist. Perhaps there are subtle reasons why such a large size is necessary (for example, perhaps inflation is a side effect of the simplest set of fundamental particles which would allow atoms to exist and hence life to form, so we get a big universe as a side effect of having simple physical laws at the microscale). But unless we can find such linkages, this appears to count against an ensemble theory. Put another way, the all-universe model should predict that our universe is little more complex than it needs to be for us to evolve. In effect it predicts that such linkages will be found. Hal
