I think Time Travel is possible and will happen in the future. Here's my theory. To Time Travel, we need to be going faster than speed of light. That's one way but there might be another one that we don't know of yet. Anyway, let's say for instance we can go back in time. I think when we go back in time, we wouldn't be this reality. We can't go back to the past of this reality. It has already happen. But we might end up in another reality or in a parallel reality if you want to call it that. As you know, there could be infinit number of parallel realities that might exist. And the past of our reality might be in a different parallel reality that is same or similar to ours but in the past. Meaning, it's the present in that reality but in our reality, we are ahead of them in time and space. So that way, what ever we do in that other reality(s) would not affect this reality even though both are the same realities with little or no differences. It's the same for going in then future. We would be time travelling to the future and other realities but the future version of ourselves. It's simple yet kind of makes sense.

I think that when you go back in time, the rules of that time are the reality. If you kill your Grandfather, you would not cease to exist. It would be a contemporary murder. When you return to your starting time, you simply would not be known by anyone. In the present, you never existed.

can u explain closely to mE y traveling faster than the speed of light can create time travel, i always hear and see this theory everywhere but i never get what they mean....

I think this MAY have arisen from a misunderstanding of Special Relativity,and the Lorenz contraction equations.

In a nutshell, as you approach the speed of light, three rather odd things happen:

You get shorter (measured along the axis of your direction of travel)
Your 'clock' slows down... e.g. time passes more slowly for you. (and hence the universe seems to 'speed up'.
Your mass increases.

You cannot REACH the speed of light because, as you approach it, your mass tends towards infinity, and hence you require almost infinite energy to go that bit faster to 'reach' the speed of light.
You also are almost flat.

And.... your 'time' slows to zero. (e.g. the universe wizzes past you infinately fast).

Extrapolating from the last point.... if you could somehow go FASTER than light, then your 'time' must go BELOW zero - e.g. negative time, e.g. time travel.

It's nonsense, of course, because it would be YOUR timeframe going backwards, not that of the rest of the universe.

Having said that, apparantly their are subatomic particles called Tachyons which, some physicists have postulated, behave as thought they are 'living' backwards... e.g. moving back in time, rather than forwards. Star Trek TNG had a few episodes featuring this.

Meow Purr.

The situation in special relativity is actually symmetric--from your point of view, other clocks in the universe slow down as well (they don't speed up).

As I understood it:
From the perspective of the person approaching lightspeed, all other clocks in the universe speed up.
From the perspective of the Universe, the wristwatch on the person approaching lightspeed slows down.

Meow Purr ???

There is no perspective of the universe. There are only different reference frames, each as valid as the next. You and I are travelling close to the speed of light right now, from some inertial frame's point of view. But if we were to see a spacecraft in that particular inertial frame we would, of course, consider it to be moving close to the speed of light and we would see its clocks running more slowly. But it's entirely relative, unless you break the symmetry.

Ok this is kind of hard to explain so please bare with me.

First, we see everything thanks to light, every object reflects/bounces off light then we see it. If the object does not bounce any light we will not see it, that's why you can't see in total darkness, because there is no light.

So lets say someone takes a spaceship to go faster than the speed of light, and this person is watched by another person in another spaceship, we can call this person the viewer. So the person brakes the light barrier aka goes faster than the speed of light. To the viewer, the person and the spaceship will not move, in fact they will look as if they have never gone anywhere. To the person in the spaceship going faster than light, everything will go dark outside the ship until he unbrakes the light barrier.

When the person in the spaceship faster than light slows down and unbrakes the sound barrier, the viewer (wich before saw the person and the spaceship not moving) will see the person in the faster than light ship dissapear into thin air, so he saw him freezed before than he saw him dissapear after the person in the faster than light speed unbroke the light barrier.

So then down to the point. Why do we travell in time when we go faster than light? Well, it is said that when you go faster than the speed of light, you arrive at the spot you started at BEFORE you even started. The more you increase the velocity, the faster you will arrive BEFORE you even started.

So for example, lets take one guy who goes around faster than the speed of light in a spaceship around the world. So he starts at the ISS( Spot 1) then he turns on his ship and goes around the Earth faster than light until reaching the ISS( spot 1 ) again, tthe problem is that while this guy goes around the world at faster than light velocity he arrives at spot 1 ( ISS) BEFORE he even started, if he increases even more the speed he will arrive even SOONER BEFORE he started, so as a consequence he is travelling back in time.

Ok that's my explanation, if you don't understand, or have a question, you are welcomed to ask.