--------------

Well, I can't "explain" it since it's all mostly theory/speculation... but here are my thoughts.

Forward:

Possible? Yes. Probable for human beings at this point in time? No...

Time travel forward in time is caused by an object (person) travelling at close to the speed of light for a given period of time. Unfortunately, accelerating to the speed of light for a human being would take a very long time in order to avoid killing the human being from high G-forces. (Imagine sitting in a Dodge Viper and flooring it... now imagine that force on you x 1000000000... you'd turn into chunky salsa). Then, to slow down it would take an equally long time to keep the human being from being turned into chunky salsa. Also, very funny things start happening to matter as it approaches the speed of light, things that would not allow a human to survive. Time travel forward in time is clearly possible; however, it is not feasible for humanity at this point. In addition, it'd be pretty useless, too. =(

Backward:

Some physicists say "yes," others say "no," others say "maybe" - I say "no, period."

Paradox - (n) self-contradictory proposition.

We all know that paradoxes are those fun "what if" statements. "What if you went back in time and killed yourself... what would happen? Cause if you killed yourself then you wouldn't be able to go back in time and kill yourself. etc..." If a paradox were to occur, what would happen? That is irrelevant because paradoxes cannot occur. They are fun to think about, but I don't think we'll see any of them happening. As such, time travel backwards in time can't be possible simply because the universe won't allow it in order to keep this "kill yourself" paradox from taking place. Now, we can look INTO the past, but we can't "go" there. We can look into the past because of the fact that light takes time to travel. When we observe the Andromeda Galaxy, we are looking 2 million years into the past. Can we actually go to the Andromeda Galaxy 2 million years in the past? Nope...

There are my beliefs on time travel.
Forward - yes, but useless.
Backward - no, you can't.

Besides, if time travel backwards in time were possible (and if humanity lived long enough to discover technology enabling it to travel backwards in time), don't you think they would have used it to improve us (and in turn, them)? Imagine if someone went back in time to the 1700s and taught us how to create and use the internal combustion engine. Imagine where we'd be today! Imagine where THEY would be today! (Wait a minute... if we already had internal combustion technology in the 1700s, then why would they go back to the 1700s to teach it to us? But if they didn't go back into the 1700s to teach it to us, we would never have it! Oh no! Paradox!) See? Can't happen.

Time travel is fun...
-Warik

Unfortunately it is a little harder to do than to say.

I'm too tired to get crazy with this but I will if the topic stays around.

Time slows as the speed of light is approached. Unfortunately, the mass of the object becomes infinitely large. Therefore an infinite energy source would be neede to move at this speed.

Einstein's theory of relativity postulates these changes in mass and time, among others, near light speed. However, he also allowed that there are some constant quantities relating to four dimensions. From this he extrpolated that space and time are different aspects of the same thing, much as matter and energy are different aspects of the same thing. e=mc^2 for the matter and energy correlation.

For the space-time correlation something called the Lorentz factor was introduced. This factor is an equation which must be applied to Newton's 3 fundamental laws of physics to validate them in the universe.

This Lorentz factor also manipulates the equation for distance in a three dimensional universe, creating an equation in which the space time correlation is made manifest.

I really wish I could write the relevant equations but I would probably make a typo - anyway I don't have something on my keyboard for the radical or sqaure root...and I don't feel like typing x^1/2 a thousand times.

Those of you reading this already know the standard distance formual in a three dimensional coordinate system.

Anyway - as I mentioned the Lorentz factor changes the disatnce equation in the Einsteinian universe - the one described by the theory of relativity as opposed to the Newtonian universe.

Hypothetically, inserting faster than light speeds into these equations would allow that time would go backward as speed became greater than light. There are numerous paradoxes in this proposal. One is that speed is measured as distance/time - such as miles/hour and how to achieve greater speeds if time stops....what can distance then be relative to? There are also apparent contradictions regarding the increase in mass of the object at this speed.

deep breath........

The problem of energy sources is still unsolved. Computer models indicate that a rapidly spinning superdense black hole will assume the shape of a torus or donut.

The incomprehensible gravity of a black hole could provide sufficient energy to achieve these speeds - after all, black holes arepowerful enough to keep light from attaining any speed. So why can't they move us faster than light?! :-)

Certainly no conventional or even nuclear energy sopurce could generate the power for those speeds.

I have ignored the propulsion issue. Notwithstanding that, the theoretical basis for time travel is pretty solid.

Ok I sleep now.

Matt

During their research they discovered that by if you entered a worm with certain properties, which I can't remember right now and emerge from another similar worm hole, it is possible to travel backwards or forwards in time. Again, they thought of paradox's, but this assumption is based on a linear time line that does not branch or break.

Suppose for a minute that as we make choices in our life we create another new universe "parallel to many others that were created by the choices of individuals and events over the course of existence. Now, when you travel backwards you travel within your current time line. If you make a change in the past say kill yourself then you would cause a parallel universe to be created at that instant. Your universe would still exist, but in order for you to return to it in your present, you would have to move into it something of an all together different aspect to space travel and time travel.

The Lorentz transformation is done in the moving inertial frame. I other words the inertial reference frame that is moving at a different speed than the one your in. The reason this works is that space/time are invariant, just like the speed of light is invariant.