Is time travel possible?

[cyberninja45]

Licence said:

cyberninja45 said:

 Keeping in trend with vgchartz these days simple question is time travel possible? To me if time travel is possible why have we never encountered time travellers, what is stopping them from coming back into the past (our present).   This leaves me to conclude three logical scenarios.

1. Scientist got it wrong and time travel is impossible.

2. Time travel is possible and there are time travellers ,they just keep themselves hidden.

3. The world soon ends so time travel is never invented.

Is there something I am not understaning that someone would like to explain.

Note when I say explain I mean in your own words ,providing links and large quote trees does not show your knowledge on a topic.

Well, presumably you mean travelling backwards in time. Travelling forward it time is possible - we are doing it even right now (it took me a few seconds to write this reply, during which I travelled forward it time by that amount). Modern physics tells us that we can even travel forward in time at different rates (look up the http://en.wikipedia.org/wiki/Twin_paradox).

On the sub-atomic level, things get interesting. According to Feynman's quantum mechanics, anti-matter (which we have observed and can even create and store) is physically identical to normal matter travelling backwards in time. Whether it actually *is* normal matter travelling backwards in time is of course a good question. 

What quantum mechanics tells us is that if time travel backwards in time is possible, it would probably be different from the "Back to the Future" type time travel where you get into some device and exit at some point in the past. It would be more similar to that movie "The curious case of Benjamin Button", where you would meet someone who seems to grow younger and lose knowlegde as time goes by.

I have read up on relativity and time dialation and I try to picture what this would look like to an observer outside of our universe (hypothetical situation of course). To me an observer outside of our universe would be watching this happen like a roll of movie film with each frame unwinding at the speed of light (each frame being a frame of reference). Correct me if I am wrong.