X-Message-Number: 20903 Date: Fri, 17 Jan 2003 20:27:42 -0700 From: Mike Perry <> Subject: Many Histories versus Many Worlds Robert Ettinger, ##20890: >David Deutsch thinks the "multiverse" is deterministic, although a >particular "universe" is not from the point of view of its inhabitants; but >he also thinks that, in any universe, the past is fixed. If he is wrong, and >there are "many histories" instead of many worlds, that's a different kettle >of fish. This can be interpreted in more than one way, and I'm not sure what is intended. Deutsch (in *The Fabric of Reality*) does note that, in a sense, time doesn't flow--the apparent flow of time is an artifact of how we observers see things. Each scenario at a particular time in a particular universe comprises a "snapshot" (think of one frame of a movie) that is unaffected by what comes before or after--or that's the way I read it. (And you will have to deal with certain problems posed by relativity, to decide just what to include in your "snapshot"--that is to say, which events at different points in space are considered simultaneous. It appears there are many possible overlaps or points in common with different snapshots.) In any case, that "the past is fixed" in a given universe is not the same as saying that history has a unique timeline. Under the many-worlds formulation worlds can split but can also fuse. (A "world" also is not necessarily a whole universe but can be a localized region.) The fusion, if it occurs, will obliterate any differences in histories between the components that fuse, thus, I think, rendering their distinguishing pasts unrecoverable. The loss of information inherent in this fusion in effect makes the past ambiguous. It seems, then, that, along with many worlds, each world will, as a rule, have many histories. Mike Perry Rate This Message: http://www.cryonet.org/cgi-bin/rate.cgi?msg=20903