Time Travel: About Time!
Have you ever read about an event or a time in history and thought to yourself, if only time travel were possible? Ever looked back on your own past and wished you could just go back and make amends or do things differently? Ever looked up at the night sky, looking at the stars and wondered how long it would take to get there? Well, the answer to that one is that it would probably take longer to get to any star you see than it took for that stars' light to reach your eyes. In that statement alone we have discovered that we can at least physically see into the past. After all, the nearest stars' light takes roughly 4.5 light-years to reach anyone's eyes on Earth. So, any starlight you see has the potential to be older than our own solar system. In essence allowing us to see a star as it were many many years ago. Which begs the question: Of all the stars you see in the night sky, how many of them are still there today? Imagine if a telescope captured images of far away star systems with planets that were deemed to be Earth-like or life sustaining. Would it be in our best interest to try and get there only to find that the planet seen by the telescope no longer existed or was no longer habitable? Or even worse, that the star it revolved around had gone supernova and had swallowed it? But I stray from the intended path. Now that we have established that seeing into the past is possible, let's talk about travel into the future.
Travel into the future is a much more complicated endeavor than simply looking up at the night sky and seeing the past. There are a few ideas on how this might be accomplished. There is the Wormhole concept. The Wormhole is a concept in physics theorized to be a tunnel-like means of traversing from one point in space-time to another point in space-time. For a better idea at what a Wormhole might look like, take a sheet of paper and place a dot at both the top and bottom in the middle of the sheet. Then, keeping the dots visible, fold the sheet of paper so that the top and bottom edges are together. Now imagine a tunnel leading from the dot at the bottom of the sheet to the dot at the top of the sheet in between the edges you just put together. That is the way one might "bridge" the gap between two points in space-time without having to cover the entire distance between the two points. While this concept doesn't seem to be time travel in the traditional sense, one can imagine the amount of time it would have taken to get from point A to point B without the convenient use of a wormhole. Imagine a trip that would take so long to complete that you would be long dead before reaching your destination. Imagine using a Wormhole and covering the same distance almost instantly. Would that not arguably be a form of time travel?
There is the Black Hole Concept. A Black Hole is concept in Physics theorized to be region in space with a mass so great that it's gravity would allow nothing to escape, not even light. Since it swallows all light that passes within it's Event Horizon (the point at which nothing can escape it's Gravity), it is invisible, thus making it black in the blackness of space. It is theorized that if a spacecraft were able to remain stationary just outside the Event Horizon of a Black Hole, the warp of space time by the immense Gravity of the Black Hole would in effect slow down time as observed by the crew of the space craft, so that when the crew decided to go back home time will have gone by at it's normal rate at home while time had gone by much slower for the crew in the presence of the Black Hole. Thus making the crew members age much slower than their folks back home. In reality traveling into the future. Imagine leaving your children here on Earth to go to a Black Hole to float just outside it's Event Horizon and go back home to find that your children had grown older than you. That is future time travel.
Another concept, one that I find more realistic than the previous concepts, not because they are impossible but because they are huge undertakings. The technology needed to get to a Black Hole is probably decades or more away. And Wormholes, even if found will probably collapse before on could travel from one end to the other. This last concept, as impossible as it may sound is probably our best shot at future time travel. It requires speed and lots of it. It has been shown that time on a clock that is stationary ticks faster than a clock that is in motion. This was proven when a group of people took an Atomic clock on a flight to eventually land to find that the Atomic clock had counted time slower than synchronized atomic clocks that were stationary. So the faster you travel towards the speed of light the more time slows down for you and the more time that passes for stationary objects. You could travel at less than the speed of light for perhaps ten years and find that thousands perhaps millions of years had passed. Just turn down the speed or turn it up to adjust the amount of time you want to pass back on Earth. Of course, since this has never been done, it remains theoretical. However, it would be wise to consider that of all the concepts discussed, this would most likely be man's best bet at time travel.
Now, we talk about actual travel into the past. I will just say now that there is almost unanimous agreement that time travel into the past would be impossible because it would, in theory, create a paradox. For example: Let's say I created a time machine ten years ago and now I want to use it to go back in time and kill my mother and father. Just for the sake of argument, let's say I never got around to it and figured now would be ideal to go back and kill them. Okay. I killed them. Here's where the paradox comes into play. If I go back and kill them, how was I ever born to go back and kill them in the first place? Physicists theorize that some force in nature must exist to prevent this from happening, and others theorize that time travel in the past must be impossible for this reason alone. However, it is important to note that it may be possible if a paradox is avoided. After all, some leading physicists theorize that all information throughout time, past and present has been preserved somehow in space-time. Sort of a universal DVR.
Finally, if one wishes to travel in time, it would be wise to consider the consequences of what one might find. Furthermore, the consequences of travel so far into the future that one finds that nothing at all exists any more...anywhere.