Re: I take objection to NASA's Mars plans!

Well, you cannot go back to a point in time where the time machine is
not operating - at least for current designs.

Since no one has made a time machine this is all theoretical. But time
machine theory says there is a time violating region - von stockum
zones iirc - that is created by the machine by rotating the spacetime
continuum near the machine relative to the orientation far from the
machine. Space becomes timelike and time becomes spacelike. Then, you
move near light speed in the appropriate direction, and voila - you
emerge at an earlier time than you entered.

A similar effect can be created if you manage to make a wormhole and
move one wormhole mouth relative to the other and bring the moving
mouth near the stationary mouth - but delayed in time. So, enter the
stationary mouth and exit the one that had gone through an acceleration
cycle, and voila you're back in time. Go the opposite way to skip
forward in time.

Couple of problems here. First, to make wormholes or von stockum zones
requires vast amounts of energy compressed in very tiny spaces. This
can be done by large populations of miniature black holes - black hole
dusts. Second, they must be precisely controlled - this might be
achievable by use of charged and or spining black holes.

Another problem is the 'orbit' through the time machine. Once an
object is sent along a certain spacetime path from one point in time to
another - that 'time circuit' is filled - and all other users must take
that into account.

But in any case your idea about timelines being destroyed and so forth
is largely addressed by the fact that engineering limitations of the
machine, and speed of light limits, make it impossible for time
machines to violate causality globally. Even so, some think you can
travel to parallel universes (see Many Worlds Hypothesis) but you
cannot violate causality globally.

http://en.wikipedia.org/wiki/Time_machine
http://en.wikipedia.org/wiki/Many_worlds_hypothesis

Exciting as all these are, we don't need to wait for this sort of
outre' physics and engineering to be developed to have practical space
travel.

There are a whole host of commercial developments that we can do today
- with today's technology, that leads us inevitably over many centuries
- to the sorts of things described here.

Could the future ever interact with us today? Sure. If there are time
violating regions occuring naturally in the galaxy that future
generations can exploit to send messages, and objects to the present
day.

One of the most important things one could do if all this stuff
actually is possible, would be to send a self-replicating robot system
back in time with orders to build a proper time machine as early in
time as possible. That way the ability to travel to as many times, and
as many parallel universes, is maximized.

Pat Flannery wrote:
> Allen Thomson wrote:
>
> >
> >And vice versa. STR says FTL -> backward time travel with all
> >of the causality worries that brings. Sum'pin to think about.
> >
> >
>
>
> Also, if someone had invented time travel in the future, and they
> traveled back in history and change something, then that particular
> future where the time machine got invented ceases to be.
> So let's hope no one in our particular timeline invents one and goes
> back in time to before we were conceived, or a different sperm cell may
> fertilize mom's egg cell, and the "we" that is the "we" that is
> ourselves doesn't exist anymore.
> In short, if someone invents time travel in the future, then the whole
> present population of the world, and not just their mothers, may be
> screwed. =-O
>
> Pat

.

Relevant Pages

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