The traveller would
therefore not have been born, so could not have travelled back, so could not
have killed his grandfather, who would then have gone on to meet his
grandmother, so he would have existed after all meaning he could have travelled
back etc.…. Is there any
scientific basis for time travel? According to leading scientists, including now
Stephen Hawking there most certainly is. Okay, the next bit becomes a bit
confusing, but bear with it if you can. If a pulse of light is emitted at a
particular time at a particular point in space, then as time goes on, it will
spread out as a sphere of light whose size and position are independent of the
speed of the source.

After one millionth
of a second the light will have spread out to form a sphere with a radius of 300
meters; after two millionths of a second, the radius will be 600 meters and so
on. (Somewhat like ripples on a pond spreading out on the water’s surface except
in three dimensions in four dimensional space-time.)
This cone is called the ‘future light cone’ of the event. In
the same way, a past light cone can be drawn, which is the set of events from
which a pulse of light is able to reach the given event (12).

Now, the following
figure, shows the light cones associated with three points in space-time, A, B
and C. Scientist and author John Gribbin explains. "These points know nothing
about each other, and have no influence on each other, because for a signal to
get from any of these points to either of the others it would have to pass
outside the respective light cones, travelling faster than light.

But as time passes, observers that start out at each of these points will follow
their own more or less wiggly world lines into the future and up the page. At
some point in the future, the observer who started at point A will receive light
signals that come from point B, and this is the first time that such an observer
can be influenced by events that occurred at point B. But this observer can never have
any influence on events at point B, because to send a signal there it would have
to go backwards in time; any interaction is strictly one way." (13)

Now comes the interesting bit. *If *
the universe is rotating (and everything else rotates: planets suns, galaxies
etc. so why not?), then space-time will be dragged round in such a way that the
light cones (everywhere in the universe) are tipped over.
If it is rotating fast enough, then the light cones will tip over so far that an
observer who starts from point A can get to point B without ever going outside
the future light cone – that is without ever exceeding the speed of light. Using
this method you could travel from A to B to C and back round the universe to
Point A. (14) So, could this be a method of
practical time travelling? Probably not, but is does indicate
that time travel is not forbidden Einstein’s theories of general relativity, and
this concept of universal rotation and cone tipping has been the foundation for
a number of other theories as to the possibility of time travel.

The idea of time travelling UFOs does appear to explain at
least one other point. Researcher Jenny Randles explains. "If you travel a
hundred years forward the building that you now work in might by then have
been demolished and a busy motorway might run through the position. Your time
machine could then appear right in front of a gigantic truck, merrily speeding
along, oblivious to your arrival, which flattens you.

Any journey backwards by thousands or millions of years could see the spatial
location where you have begun your trip hugely altered, submerged under an
ocean or raised up inside a volcano, for example. There is just no way that
any machine developed for a physical move through time could do so whilst
remaining on the ground. Indeed, there is only one relatively safe place where
such a time transfer could happen – that is well above the surface, or better
still outside our atmosphere altogether." (15)
The idea of time travel could certainly answer some intriguing puzzles. One can
almost imagine one such traveller in prehistoric Illinois asking a fellow
traveller to hurry up and get back into the time machine.
"Hold on, I’ve dropped something. That gold chain you gave me." "Oh, it’ll turn
up" comes the reply only to give one Mrs Culp her 15 minutes of fame millions of
years later.
**Continues ...**