Time Reversal
Reversing Time at Sub-light Speed
as Origionally posted on the internet By David Anderson, Ph.D.
In this series of articles we will show a solution using a rotating cylinder model that demonstrates how time travel is possible within the context of general relativity. This solution clearly permits time travel and communication not only to the future, but also to the past. Most important, it will show how reverse time travel can be achieved without having to travel faster than the speed of light. The advanced computer simulations we have run at the Time Travel Research Center have confirmed this model as a valid approach for actual time travel to the past.
Introduction
The rotating cylinder model is based on a conclusion of general relativity that shows rotation of matter causes a distortion in space-time. This distortion can become powerful enough to actually twist time around a rotating cylinder.
With the right amount of mass and speed, a pattern of what are referred to as “closed time-like curves” can be created.
Navigating through this pattern of closed time-like curves will permit time travel to both the future and the past without violating the laws of mathematics and physics.
To understand time control using rotating cylinders requires some understanding of general relativity. An overview of the “General Theory of Relativity” has been included as a separate article in this issue of The Space-Time Journal. It also requires a basic understanding of space-time physics, including the ideas of space-time diagrams, light-cones and closed time-like curves. Following is a brief review of these topics.
Space-Time Diagrams
A common tool we use to discuss space-time is the space-time diagram. This diagram plots the position of a particle as it moves through space-time. By connecting all the plotted positions, a line called the “world line” of the particle is created.
In reality, a true space-time diagram would have four dimensions including three space dimensions and one time dimension. This type of diagram is very difficult to illustrate and visualize. Wherever possible we use a simpler convention to illustrate concepts in space-time.
The illustration to the right shows a simplified space-time diagram with just one space axis (y) representing motion through one space dimension, and one time axis (t) representing motion through time.
Lets look at the example of a particle starting at rest on the origin of the y and t axes. If the particle does not move over time in the space dimension (y) it will not move off the time axis (t).
So for a particle at rest in some observers’ frame of reference, its space-time diagram for that observer is a vertical world line. This is illustrated in the space-time diagram to the right showing a particle at rest.
The path the particle follows, whether it moves in the space dimension (y), time dimension (t), or both represents what we call its world line. The world line represents the path the particle follows in space-time as a whole.
If the particle moves in the space dimension (y), its world line tilts away from the vertical as is illustrated in the space-time diagram of a particle moving at constant speed shown to the left. Straight (un-curved) world lines like this represent un-accelerated particles (i.e.) particles experiencing no forces.
If a particle experiences acceleration, its world line will curve away from the vertical time axis. If the same particle experiences decceleration, its world line will curve back towards the vertical time axis.
The resulting world line will be curved as is illustrated in the space-time diagram of an accelerating/deccelerating particle on the left.
In order to make a space-diagram more meaningful in has become common practice to normalize the axis to a specific standard.
Each unit on the time axis (t) is set to a second and each unit on the space axis (y) is set to one light-second. A light-second is the distance that light can travel in one second, which is 300,000 kilometers. This normalization of axes is illustrated to the left.
One Response to “Time Reversal”
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February 13th, 2008 at 1:30 am
I am not a physicist or any other type of scientist. But I became curious and mildly surprised upon reading about the rotating cylinder model. Ever since i was at least a teen (i am now 43) I have said quite seriously that there is no such thing as time, as we know it.
When trying to explain my feeling about this to my mother in a concrete way, I chose to use a cylinder shape (like a spring) to try to explain my concept.
Hmmm, probably just a coincidence…but who knows?