Steve's very nearly right. I will add this:
Every choice taken where multiple possibilities exist results in the
branching into a new timeline. The best quantum physics models support
this scenario. In linear or sequential time observation reality, the
observer is only aware of the reality of the other possibilities as
being actual to the degree of their probability. At the 'static'
super-universe level, all possible timelines are expressed and fully
realized as so-called "Parallel Universes". Actually, where there are no
differences, those portions of the timelines are united and one the
same. That is, they intertwine.
In fact, during every-day common life we often branch away from one
another's timelines only to re-merge moments later and no one is the
wiser. This is easy because we all still stay on the main probability
current which is driven by larger external forces and composite group
consciousness. Only small undetectable deviations are typically able to
be travelled between those in the group.
All possible universes exist but they are not all equally probable and
so therefore are not all as easily realised by an observer. Many
observers in tune with one another affect the probability wave so that
they are more likely to observe the same reality as one another.
The possibility of time travel requires that an event having once
occured, be eternally existant. This means that it exists at the same
time as the present and all other moments for that matter. If all events
are eternal, and eternity is a time function, then all events are
co-existant in time. So then why are they not all observed
simulatenously? Because they are separated by 'space' and dimension of
'scale'. All events expand away from the observer. This is allowed by
the infinite 'fractality' of the space dimension. This way all events
can occupy the same point and time without colliding. Think of this if
you can; 'a fractal geometric point'. This is not the classical
geometric point of zero dimension but rather its inverse or infinite
The observation of the present and its relationship to past and future
may be illustrated by this diagram:
\ | /
\ | /
\ | /
past \|/ future
/ | \
/ | \
/ | \
This can be considered as two cones intersecting at a single point of
their vertices. The intersection is the point experienced as present or
Fortunately the probability functions yield up a nice tidy geometry
which has highest probability. This gives us a geometric space matrix
with certain realities predictable to a sufficient certainty to make
them likey determinate. We need not manipulate all (fractal)harmonics to
travel between fractal layers, just those either side of us to the
'fractal event horizon' each way. Since there is a discreet twist
between each level there is a finite set of harmonics that actually need
to be adjusted to span these limits.
Space travel is proportional to time travel. Because time passes us at
such a rapid speed we need to travel at an equally rapid speed to keep
pace with it. Once we are travelling at the speed of time (c) space
decreases to a point. This could be troublesome since we will be at all
points in the universe simultaneously.
Three steps are required for time travel:
1) Neutralize local gravity lock. This requires expansion of
self-vehicle full spectrum radiant field magnitudes and/or velocity
acceleration. This could be acheived through either brute force
'terawatt' magnitude external forces, or alternatively through subtle,
harmonically precise 'micro' forces.
2) Navigate timelines. Could be done by 'stroboscopically' slowing
(halting acceleration) at discreet intervals to maintain upper-harmonic
phase sync with local timeline/gravity/space.
3) Drop fields and halt motion to lock back into local gravity.
Be careful where you stop though. The local probability may not allow
your vehicle's physical existance at that point in time. This might not
really be a problem though because you probably couldn't obtain a
gravity lock in that instance.
All of this may involve ultimately unsolvable paradoxes which will
prevent the actual practicality of physical time travel. But this is the
logic of it nonetheless. At the mental level however, time travel is a
very real and attainable practice but nearly impossible to demonstrate
to another with physical proof.