I am putting this out in order to clarify my understanding - hopefully the MWI experts out there can help me out here. A while back I asked whether the past can be undefined at a quantum level the way the future is. I asked this because I recall (somewhat vaguely unfortunately) reading or hearing something from Stephen Hawking in which he appeared to argue that at a certain very early point in the universe, there is no longer a single history, but quantum uncertainty comes into play, with important implications. Anyway, the response to my question indicated that most people still assume that history represents a single, well-defined line through the multiverse (I'm assuming MWI here, even though I know it's not the dominant theory/interpretation).
I have been thinking about this and it occurs to me that firstly, the single history is only partially true. Since quantum interference patterns occur in MWI due to interference between universes, which can only occur if universes can merge again after splitting, then at least at this level, the past is not well defined. If a universe merges back with another from which it had temporarily diverged, then an observer within that universe cannot say which path he followed to get there. She followed all possible paths. Of course those divergent universes were only trivially different, or else decoherence would have made the merging impossible. But of course in any real universe, there will be a vast number of such "nanohistories", because of the immense number of quantum interactions where merging occurs. So at this very short time/space scale level at least, it is impossible to define a single history. Correct? However at a macroscopic scale, it appears difficult for history to be intrinsically ambiguous. In other words the network of "nodes" of the multiverse is like a tree not a net. There may be tiny branches that rejoin one another at the smallest scale, but the limbs of the tree cannot merge back together. I can always define a single route back to the trunk, though if I go further up the tree, I will be forced to decide repeatedly which way to go. This branching is defined by time, so doesn't this effectively give an "arrow of time"? Yet the laws of physics are not supposed to be directional in time except through aggregation of effects as entropy. Are these two "arrows" related? How? -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/groups/opt_out.
