Why our universe is open.

From: Saibal Mitra <smitra.domain.name.hidden>
Date: Mon, 21 Aug 2000 23:11:43 +0200

Although we now know for a very long time that the brain is a (very complex) machine, we pretend as if we are somehow more than what a machine ever could be. This bias will disappear as soon as there are machines around that can pass the Turing test.

This does raise interesting philosophical questions about consciousness. Suppose we had a very powerful computer that allows us to simulate an entire miniature universe, consisting of just one person living in a prison. It is assumed that at least the brain of the person is simulated in a realistic way. Using virtual reality techniques it would be possible for me to visit this prisoner. The prisoner can, from time to time, also visit us in the following way. At certain times the prisoner is allowed into a room. In this room the computer simulates a virtual reality apparatus. When the prisoner gets into the apparatus, he can control a ``real创 robot wandering in my room. This is thus virtual reality ``the other way around创. It would now be very difficult to deny that the prisoner has consciousness.

An interesting question can now be asked: Does the prisoner only exist when the computer is simulating his universe, or does his universe exist independently of our universe and simulating his universe simply means that we can take look at his universe and even interact with him?

If the latter is true then clearly all possible universes exist independently of each other. We can then ask why we find ourselves in this universe instead of the rather boring universe of the prisoner. I think that this must follow from probabilistic arguments. It may be that all universes are, in some sense, equally likely a priory. The probability that we find ourselves in a particular universe would then be given by an appropriate conditional probability. When we refer to our universe we actually refer to a large class of universes, because we don't have complete knowledge of our universe (we can only store a finite amount of information in our brains). So, given the knowledge we do have, we live in a large number of universes ``simultaneously创, and the number of ``equivalent创 universes increases with its size. We should thus ask for the probability that we live in any of the equivalent universes. It is thus clear that ``our创 universe is infinitely more likely than the prisoner`s universe.

Interestingly this fits in well with observational evidence that our universe is flat. From the arguments I gave above, you would expect that the universe is spatially open, because such an universe has an infinite volume. This infinite volume also cause me to exist in an infinite number of places simultaneously in a single universe, because the probability that somewhere an intelligent being emerges that has stored in his brain the same information as in my brain is extremely small but strictly larger than zero due to the finiteness of the amount of information that can be stored in the brain. It would, of course, necessarily be the case that this intelligent being is very, very similar to me and that he lives on a planet which is very similar to the earth.

Now it would be reasonable to expect that an universe where the density of ``copies创 of me is larger is more probable. By increasing the matter density of the universe I can increase the number of copies of myself, but if the matter density becomes too large then the universe would be spatially closed. Therefore it is reasonable to expect that we live in a flat universe.
Received on Mon Aug 21 2000 - 14:24:53 PDT

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