Time Travel

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Time Travel

• By B. Justin Scholfield

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What is the nature of Time?

• Time is used to relate events
• We define two actions as simultaneous when we see
  the two actions at the same time

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Special General Relativity
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Special Relativity
This is the boost matrix, or Lorentz tensor. It
describes the translation of position and time to
another frame moving at speed v along one axis
Its called special relativity because it cant
handle acceleration that well. It can be used for
doing relativistic mechanics as long as gravity
is not involved Fun Fact It took Einstein only
8 weeks to come up with special relativity.
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General Relativity
This is the Einstein Field Equations It is
described as 16 coupled hyperbolic-elliptic
nonlinear partial differential equations
Meaning its very, very hard to solve.
In expanded form it is three pages long, just to
define the problem
The Field Equations are used to predict how a
distribution of mass will effect space
All the time machines I will mention will be
based on solutions to this equation
Fun Fact it took Einstein 8 years to create this
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The Diagrams of Time Travel

• Minkowski diagrams and Light cones

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Minkowski diagrams

• Minkowski diagrams are used to
• show a particle traveling thru space
• time, they have one time axis and
• one space axis.

The particles in a diagram form a world line
which is the line that a particle takes thru
space time
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Light Cones
Light Cones are used to show how a particle can
move. The edge of the cone cant be broken
because that would mean that the particle has
some how gone faster than light
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Accepted forms of Time Travel
The following forms of time travel are all future
ward and all of them have been experimentally
verified
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High speed based Time Travel
The equation shown is the formula for time
dilation at high speeds
For example at .999999c the dilation factor is
about 707
The difficulty with a practical application is
that to reach such high speeds requires a good
deal of acceleration
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Time Travel Because of Acceleration
General Relativity shows that time dilation is
created by acceleration. The acceleration can be
anything from gravity to linear acceleration to
angular acceleration

• Fun Facts
• There is a 7 difference in the time measured on
  earth and on a neutron star
• On a rotating disk with a 66,000 g centripetal
  acceleration an atomic clock was used to measure
  the time dilation for an experiment

That rotation leads to time dilation implies that
a possible time machine could be a high powdered
dryer
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The Twin Paradox
One twin leaves the earth and travels into space
on a space ship (a fast one) and the other stays
behind. The space twin is younger than the earth
twin when he returns. Why cant it be the other
way around?
Answer one has a curved world line, the other
doesn't.
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Backwards Time Travel
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The Gödel Universe
Gödel's Idea was to make a Universe that would
enable time travel. He dose this by using frame
dragging and a rotating Universe
Frame Dragging happens when a rotating mass drags
space with it, it there by causes light cones to
tip.
Fun Fact Yesterday (10/21/2004) the first
experimental verification of frame dragging was
published
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The Tippler Cylinder
The Tippler cylinder is related to the Gödel
universe. It uses an infinitely long rotating
cylinder to achieve the same effect.
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Worm Hole Time Travel
Worm Holes are solutions to the field equations
that allow space to be non simply connected
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How to make a Worm Hole into a Time Machine
Once a Worm Hole is made one end of it can be
placed in a high gravity field or accelerated to
a high speed then slowed down again. This
provides a time machine for as long as the Worm
Hole exists.
The a difficulty arises in doing this because
worm holes tend to be unstable and my be
destroyed if moved or placed into a high gravity
field.
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Problems With Worm Hole Creation
A worm hole requires an lot of tension to be kept
open, for a 3 foot diameter worm hole it is on
the order of 1036 tones. Something that could
hold at this level of tension would be classified
as can rightly be called exotic matter.
No one is sure how to make a worm hole. There are
many suggested methods of worm hole creation but
most require a black hole or an ability to
inflate one form the quantum foam.
A Worm Hole that passes thru time could also make
a unbounded energy resonance that would destroy
the worm hole.
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Paradoxes with Backwards Time Travel
The diagram is a picture of a billiard ball going
thru a worm hole time machine. This is a machine
version of the grandfather paradox. The billiard
ball has an infinite number of possible paths,
all self consistent. The solution to what the
path of the ball will be is as a group of
probabilities and cant be solved until we have a
better grasp of quantum gravity.
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In Closing
All The time machines That I have mentioned are
allowed by general relativity. There are no known
physics that dont allow this.
Sources
1.Time Machines Time Travel and Physics,
Metaphysics, and Science-fiction. Nahin, Paul J.
1999, Springer-Verlag New York, Inc 2. How to
Build aTime Machine. Davies, Paul. 2001, Viking
Penguin. 3. Black Holes Time Warps, Throne, Kip
S. 1994, H.W. Norton Company. 4. Factors,
Tensors, and the Basic Equations of Fluid
Mechanics. Aris, Rutherford. 1962 Dover Books 5.
The Einstein Equations. Author unknown.
http//archive.ncsa.uiuc.edu/Cyberia/NumRel/Einste
inEquations.htmlintro. Accessed 10/21/2004 6.
Spinning Earth Twists Space. News report.
http//www.nature.com/news/2004/041018/full/041018
-11.html. Accessed 10/21/2004