Saibal Mitra wrote:
> How would an observer know he is living in a universe in which information
> is lost? Information loss means that time evolution can map two different
> initial states to the same final state. The observer in the final state 
> thus
> cannot know that information really has been lost.

If the universe allows two different states to evolve into the same final 
state, the second law of thermodynamics wouldn't hold, and we would be able 
to (in principle) contruct perpetual motion machines.

I don't know why you say this can't be detected by an observer. In theory 
all we have to do is prepare two systems in two different states, and then 
observe that they have evolved into the same final state. Of course in 
practice the problem is "which two different states?" And as I suggest 
earlier, it may be that for anthropic reasons one or both of these states is 
very difficult to access.

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