Time Travel
Moving
Backward In Time: Kerr Black Holes and Worm Holes
A black hole
occurs when a sufficiently large mass is compressed
into a sufficiently small space. The gravitational
field of a black hole is so massive that it warps both
space and time. Any objects in its vicinity will be
pulled inside and crushed. While such a black hole
would be deadly, a second type of black hole called a
Kerr black hole could potentially offer a mode of
space/time travel. Because of a Kerr black hole's
centripetal motion, a singularity would not be capable
of forming. As a result, the contents of the black
hole would have to be expelled in some way. Physicists
hypothesize that there may be an opposite of black
holes, known as "white holes." Rather than pulling
matter and light into themselves, white holes would
eject light and matter (1).
![Kerr Black
Hole](Images/timetravel2.jpg)
http://www.sipl.technion.ac.il/~avi/horizon/Horizon_heb_files/image001.jpg
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A black and white hole pair could exist at
distant regions of both space and time,
allowing for travel between the two. Not only
would the traveler be able to traverse vast
regions of space, they could hypothetically
travel to a previous point in time as well.
For example, the Doctor could enter a Kerr
black hole in the TARDIS near present day
earth and emerge in a galaxy far away and some
time ago.
The problem with such a mode of time travel is
that it is non-reversible. Because the
traveler emerges through a white hole, it
would be impossible for them to force their
way in the opposite direction to emerge at
their starting point. As a result, the
individual would be stranded a long way from
home with no way of returning. This is where
methods of travel such as worm holes become
more attractive options.
Einstein-Rosen bridges (worm holes), unlike
Kerr black holes, are not unidirectional.
Rather, they can be thought of more a
corridors between two points in space-time.
Worm holes could arise from the distortion of
space-time by sufficiently large masses, as
allowed by Einstein's theory of general
relativity (1). Such a passageway would be far
more convenient for time traveling, as one
would be able to not only visit a distant
place or era, they would be able to return and
share their experience.
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