How to Time Travel
It may seem like an impossible feat, an almost ridiculous concept. But it can be possible.
To learn more about the science of time travel, read on!
1. Travelling at the speed of light (or close to it)
This one requires some background knowledge.
'The Theory of Special Relativity', first created by Einstein, states that your experience of time changes depending on your movement and velocity. Specifically, if you were travelling at very high speeds (close to the speed of light), each second would pass by much slower than someone who is stationary.
Here's a pretty famous example that Einstein came up with himself. Lets say there are two twins sitting here on earth, one named Al and the other Bert. Al has decided to go on a voyage in space which will last for 5 years, and he will travel at 94% the speed of light. Bert decides to stay at home. When Al comes back after his 5 year trip, he will find that Bert will be significantly older than he is. This is time ticks slower for a stationary body than for a moving body. Strange isn't it!
Granted, this isn't the most traditional sense of time travel, but it still is a form of time manipulation.
1.2 Using the Warp Drive
Since I've already written an article about this, I won't go too in depth. But, using the warp drive, we could travel even faster than the speed of light, exaggerating the effects described earlier in the article.
2. Going through a wormhole
This one is quite incredible.
In order to understand this one, either follow along or just imagine it in your head.
Take a piece of paper, and draw two points on either end, labelling one point as A and the other B. Let's imagine that the piece of paper is spacetime, and you want to travel from point A to point B, and the distance between the points is several light years.
In this case, traveling between the two points would take a very long time.
Now, fold the piece of paper so that there is a much smaller gap between the two points. Now, travelling between the two points is a lot easier. This is essentially what a wormhole does, it acts as a bridge between two different points in spacetime.
Now you may have noticed that I keep saying 'spacetime' instead of just 'space'. This is because space and time both intertwined, and inseparable. So, not only can a wormhole connect two separate points in space, but also two separate points in time. And so, a wormhole can be used for time travel.
3. Looking through a telescope
Light takes time to travel from one point to another, it doesn't travel instantaneously.
We can use this fact to perform this kind of pseudo-time travel.
Our own sun is about 8 light minutes away from earth, meaning it takes light 8 minutes to travel from the earth to the sun. If you were to look at the sun (which I would advise you don't do), your retina would be registering light that was let out by the sun 8 minutes ago. 8 minutes isn't a terribly long time, so lets go out even further.
Let's say there is a galaxy about 1000 light years away. If we were to look up to that galaxy from earth, we would be seeing what that galaxy was like 1000 years ago.
In the same sort of way, if aliens in that galaxy decided to use their telescopes to look at us, they would see the earth during the time of the crusades. Amazing, right?
And that's all!
http://www.livescience.com/39159-time-travel-with-wormhole.html
http://newt.phys.unsw.edu.au/einsteinlight/jw/module4_twin_paradox.htm
http://www.andersoninstitute.com/alcubierre-warp-drive.html
http://www.space.com/20881-wormholes.html