🚀 go-pugleaf

>Of the three
>proposed mechanisms for time travel (spinning blackholes, rotating
>cylinders and wormholes) each one only permits travel over the life-time
>of the machine, which itself doesn't travel through time.

Your wording could be misunderstood.  A wormhole may be created at one
moment and then exist into the indefinite future.  So from it one could
travel only to any time after the wormhole was created.  If we found an
already existing wormhole, deliberately created or otherwise, then we
could see the dinasaurs.  Unlikely though.

>There are
>no grounds in quantum theory for identifying the parallel timelines with
>the other worlds of the many-worlds interpretation of QM.

To the contrary, this would seem to me the most natural extension of QM
into this new domain.  When one finds a previously undiscovered internal
degree of freedom of a particle, the natural reaction is to just enlarge
the space of quantum states, and do "sum over all paths" or "linear
combinations of all possible states" in this new space.  So if we learn
that time machines allow new degrees of freedom, single presents being
consistent with multiple futures, the natural reaction is to toss them
in the total state space and do as ususal.

Robin Hanson  hanson@charon.arc.nasa.gov   "Stake Your Reputation"
415-604-3361  MS-269-2, NASA Ames Research Center, Moffett Field, CA 94035
510-651-7483  47164 Male Terrace, Fremont, CA  94539-7921