Faster than light speed travel (and consequently, time travel by our current understanding of relativity) through a worm hole.
If you don't understand relativity, the picture won't do you too much good. Basically, a worm hole is a "shortcut" through spacetime, meaning that you would not travel faster than the speed of light, but that you would take a shorter path than the light. Relativity says that as you approach the speed of light (impossible for anything with mass to actually reach the speed of light), time will go slower for you (you will still experience 1 second as you do now) than it would for somebody at rest. They would see your clock as ticking slower than theres.
By going through a wormhole and actually going faster than light to a given location, as shown in the picture, you actually travel to the past. Here is where the interesting part is, that you do not need a very strong understanding of physics to get. You know in movies, how there is always some kind of paradox when it comes to time travel, like how can you change what has already happened, what happens to the "present" as it was originally if you change the past, etc. etc.
What happens here is that the earth that you left behind when you traveled into the past will continue to exist, and the place that you arrive is PARALLEL UNIVERSE, exactly identical to the one you left, zomg!!! If this weren't the case, the people who watched you go through the wormhole would cease to exist as soon as you changed one thing in the past.
This wormhole idea does not violate relativity or general relativity, however it is not fully understood whether quantum physics would allow for it.
