Theories:
Multiple Dimensions (based on)
This theory states that the past can be altered, thus affecting the future.
There are problems. The commonest are the so-called paradoxes. For example, if we could travel through time, imagine what would happen to a time traveller if he (or she) travelled back in time and killed his own grandmother at birth. In theory the time traveller will therefore never be born, so the journey could never have been made in the first place; but if the journey never occurred then the grandmother would be born which means the time traveller would have been born and could make the journey ... and so on and so on. This is a paradox.
There are two possibilities to resolve this paradox. The first is that the past is totally defined, i.e. everything that has happened or must happen, including the time traveler's attempt to kill his grandmother, cannot be altered and nothing will change the course of history. In other words, the time traveller will experience endless "mishaps" in trying to kill his grandmother and will never achieve the murder, thus keeping time (or at least events) intact.
The second possibility is more complex and involves the quantum rules which govern the subatomic level of the universe. Put simply, when the time traveller kills the grandmother he immediately creates a new quantum universe, in essence a parallel universe where the young grandmother never existed and where our time traveller is never born. The original universe still remains. Stephen hawking believes he can explain the origin of our universe in a variation of this parallel-worlds theme.
Side Effects
Chaos theory is the theory of the unpredictable behaviour that can arise in systems obeying deterministic laws as a result of their sensitivity to variations in the initial conditions or to an excessive number of variables. Although deterministic laws enable the condition of a system to be predicted at any time in the future, to do so often depends on an ability to specify with great precision a set of parameters at an exactly specified moment. An example of chaos theory occurs in long-term weather forecasting. T'he meteorological laws may be well understood, but obtaining exact parameters to use with them may not be possible. In the butterfly effect, for example, it is postulated that the flap of a butterfly's wings can so upset the sensitive meteorological dynamics that an unforecast tornado may be set off by it.
Single Dimension (Calvinism)
This theory states that no matter what you do, there's only one outcome. It's predetermined, it's unavoidable. Any attempt to change it is not only impossible, but the actual attempt was predetermined, too.
Paul's Theory
Time is movement. The past is non-existant. We live in the now, we have recollection of what has happened before. Take an instant and freeze it where nothing moved, everything stopped exactly where it was, and no thoughts could be interpreted; overall there is not more movement in the world. Does time exist?
If you answered no, then Paul's theory stands. Time is movement, therefore it's an illusion (Paul, email me if I phrased this right).
If you answered yes, email me to explain your theory.
Time Travel is Impossible
Recently (in terms of when I wrote this), scientists have proven that time travel is impossible. Read the article here.
TV & Movies
What I plan on doing with this section is point out how the following TV or movie uses a form of time travel. Then, I will follow up with an analyzation if there's a consistency, flaw and/or paradox.
Deja Vu
Okay, prepare yourself, I'm about to go into rant mode. I appreciate the movie taking the time to explain the paradoxes of time travel. The Calvinism and the Timeline A / B theory. People need coaching. BUT! This movie makes no sense.
*SPOILERS FOLLOW*
Okay, the movie opens with these facts: Doug Carlin (Danzel Washington) happens upon a dead body of a woman, Claire Kuchever (Paula Patton). This is the series of events that follow: Doug finds the body of Claire. Doug then searches her apartment finding bloody swabs, a gun, and glasses (with his fingerprints all over the place). Now, when Doug sends himself back into time, here's where I take issue. He stops Claire from being killed by Carroll Oerstadt (Jim Caviezel), and they retreat to her apartment where she bandages him, pulls a gun on him, and they share drinks. My question is this: how can the original storyline still take place (where she's dead and all that stuff in her apartment happened) when she needed to be alive for all that stuff in the apartment to happen (why would Doug go to her apartment to change his bandages, pull a gun on himself, and drink from two glasses).
Time Travelling Authenticy: 1 out of 5
Frequency
One of my favorite time displacement movies.
Plot outline: In 1999 Queens, Officer John Sullivan (Jim Caviezel) has found a lead into an unsolved serial killer case (the Nightingale Killer) he remembers from his childhood. This discovery happens a couple days before the 30th anniversary of his firefighter father's death, Frank Sullivan (Dennis Quaid). While rummaging through some old items belonging to his father, he finds Frank's old ham radio. Through the rare occurrence of aurora borealis activity visible only once before in Queens in 1969, Frank soon finds that he is able to communicate with his father through the ham radio 30 years in the past. The two timelines move alongside each other, so when one detail changes in the past, at the same moment in the present, John remembers a new timeline (as well as the old). On the day his father originally died, John is able to give advice to his father and save his life. John then remembers his father living for another 20 years before dying (from cancer brought on by his habit of smoking cigarettes). That night, John wakes up from a nightmare of being at a funeral as a child. Turns out that now the Nightingale Killer has no longer claimed 4 lives, but 10. And his mother was now number 6....
Butterfly Effect
Back to the Future
Back to the Future II
Back to the Future III
Lost In Space
Time Machine
The Dead Zone (movie)
The Dead Zone (series)
Tru Calling
Quantum Leap
Futurama
The Outer Limits
Sliders
Lilo and Stitch (#134 - Melty)
The Simpsons (Treehouse of Horror VI)
Links
http://freespace.virgin.net/steve.preston/Time.html