Re: Crit: Time travel intro

"Tina Hall" <Tina_Hall@xxxxxxxxxxx> wrote in message
news:MSGID_2=3A240=2F2199.13=40fidonet_406e51eb@xxxxxxxxxxxxxx
Logan Kearsley <chrono.surfer@xxxxxxxxxxx> wrote:
"Tina Hall" <Tina_Hall@xxxxxxxxxxx> wrote

It's only my theory; that you can't change what happened in the
past (thus can't change the present), because whatever you did
in the past _made_ the present. It's a result of your choice.

There's a little more weight behind it than that. The idea even
has it's very own name (well, not quite- it does derive from a
person's name): The Novikov Self-Consistency Principle. Short
version- Paradoxes Don't Happen.

Oh, nice. :)

My second favorite version of time travel is from the movie
_Primer_. The best way to describe that is that time is like a
continuous river that always flows at the same rate. If you go
back in time, say, an hour, you can make any changes you want,
but they'll only propagate forward as fast as everything else.
Metaphorically, that would be like getting out of the river,
walking back a ways, and dropping in some dye or whatever. If you
then travel any amount of time into the future, you'll find that
everything is just you left it- the dye hasn't flowed that far
yet. Travel back again, and you'll see things changing- the dye
moving along. It allows for setting up lots of short (or very
long, if you like, but that's much harder with the technology
portrayed in the movie) time-line cycles with different histories
that you can shift between.

Interesting, though not something I'd like. It also ignores that
changing things where the dye is put in would have to have an effect
even where the river meets the sea, and instantaeneous.

Well, there is no sea, and kinda the whole point is that it's not
instantaneous- it takes meta-time for the changes to propagate down the
time-stream. Although...

The latter is something that seems to be ignored even in stories with
changing the past/present. Or that there doesn't have to be any time
passing while you're somewhere back in time. (My theory is that you'd
get back the moment you started, since 'your own' time didn't move
forwards without you.)

....while presumably, in the _Primer_ scenario, your own time does move along
without you just as fast as every other part of the time-stream, I don't
think it was actually directly testable, because I'm pretty sure they had no
way of traveling forward in time- just back. The nature of the time-travel
machine makes it apparent that changes really do propagate down the
time-stream non-instantaneously, though.*

Given a time machine that can only take you back, the third possibility
arises that the act of going back erases the timeline after the point to
which you travel. Essentially, from the perspective of your point-of-entry
into the past, you spontaneously appear from nowhere and things are replayed
as a new scenario with you, the time traveler, added. I don't particularly
like that one because I don't like the idea of spontaneously generated
information like that, but it's easy to slightly morph it into a sort of
many-worlds scenario, where time travel just causes branching universes.

-l.
------------------------------------
My inbox is a sacred shrine, none shall enter that are not worthy.

*Basically, time cycles backwards and forwards inside the box between the
time it's turned on and the time it's turned off. If you put something in,
turn it on, turn it off, and take the something out, it will have aged
several months, or years. If you turn it on, then get in just before turning
it off, wait for the period of time that it was turned on, and get out,
you'll end up getting out right after turning it on, creating a duplicate of
yourself. Wait two periods, and you exit at the same time you entered, just
before the box is turned off. Three periods, and you go back again.... etc.
Every cycle creates a new block in the time-stream, and other boxes can be
used to go back and investigate each block to prove that the changes
propagate at normal time-speed.


.

Relevant Pages

  • Re: Crit: Time travel intro
    ... Logan Kearsley wrote: ... Metaphorically, that would be like getting out of the river, ... and dropping in some dye or whatever. ... Travel back again, and you'll see things changing- the dye ...
    (rec.arts.sf.composition)
  • Re: Interstellar Propulsion idea using an Asteroid and a few comets!
    ... > propagate for a ball to roll down it. ... Any 'effect' of the electric field (even if it is a charge spinning around ... And changes travel at speed of light. ... There is no reason to assume that gravitational fields dont work the same ...
    (sci.space.policy)
  • Re: Interstellar Propulsion idea using an Asteroid and a few comets!
    ... > propagate for a ball to roll down it. ... Any 'effect' of the electric field (even if it is a charge spinning around ... And changes travel at speed of light. ... There is no reason to assume that gravitational fields dont work the same ...
    (sci.physics.relativity)