Not Like Back to the Future

Time travel has long been thought about by pretty much everyone at some point in their life.  Whether it be due to wanting to change things in the past or gain insight into what the future holds, time travel is, in our nature, an interest.  Being able to achieve time travel would open humanity up to countless possibilities, ranging from a greater understanding of the past to gaining the knowledge of the future.  However, despite all this, there seem to be some inherent problems with time travel in general.

In the 1984 film, Back to the Future, the main character, Marty McFly, meets the eccentric scientist Dr. Emmett Brown, and travels back in time in a tampered with Delorean.  In the past Marty accidentally causes his mother to prefer him over his would-be father, and so he must find a way to get them back together so that he and his siblings can exist 'back in the future'.  While this makes an entertaining film, as far as theoretical 'actual time travel' goes, it, and including the simple theory behind the movie's version of time travel, are simply not viable.

The first problem many people interested in time travel become aware of is the simple question: "if time travel were possible, then why haven't we met any time travelers yet?"  People like to disprove this argument, saying things like "people in the future wouldn't be interested in coming back to our time," or "there might be laws against interfering in the past," but frankly these are childish excuses.  Given the ever stretching possibilities of the future, it just isn't reasonable to assume that if time travel was possible in it's pure form that we would have seen no signs of it by now.  All it takes is one lunatic getting hold of the technology for us to have future-men parading the streets with absurd technology from the future.  This would seem to disprove time travel with relative certainty, but fortunately for potential time travel, the nature of time is just not that simple.

Many scientists and other such thinkers are still convinced that time travel is, or at least 'should be' possible.  David Lewis, for example, opens up with the line "Time travel, I maintain, is possible," in his article "The Paradoxes of Time Travel."  Similarly, in Richard Taylor's "Space and Time," he also holds that time travel, that is, the moving away from a  point in time, and then 'later' returning to it, should logically be possible as well.  But how can these things be possible given the problem I stated above?  To move forward in my discussion at this point I will use evidence from these articles as well as information I have learned from a scientific class on the subject.

Time and space are inherently related.  It has been proven that at incredible speeds, time will actually slow down.  While this is only significant for near-light speeds, it nonetheless proves that the two are eternally linked, and that we can think of time is a similar way to space, much as E=mc^2 proved that mass and energy are interchangeable.  So this means that if we were to be able to go at near-light speeds and come out alive, we could slow the time around us, while the rest of the world goes at normal speeds.  In this way, we could travel for, say, a year, but in the meantime the Earth could move ahead 10, 20, or any other amount of years depending on the speed.  Thus, when we returned to the Earth, we would have effectively traveled into the future.  While this method provides for no means to move into the past, it at least proves that moving along the timeline separately from our local world is possible.  We would just need a greater understanding of the nature of time to discover a way to move in the opposite direction.  Perhaps this could be done through great distances, in which we have seen that the velocity of an object, if moving towards or away from another object, slightly shifts the 'present moment' in which a person standing at either location would say is happening 'now' (this bit of science is wildly hard to get your mind around, so you'll just have to bear with me for the moment).  So then by moving away from Earth from many light years away, we could shift the 'present moment' into the past, and if we were then to cross the distance back to Earth while maintaining the same velocity (only possible due to the theoretical wormhole given our current understanding- remember, nothing can move faster than light speed) then we could arrive back any amount of years in the past.

So simple!

But this still does address the problem I previously mentioned, the "why haven't we met time-travelers" problem.  Scientists have come to the conclusion that assuming the forth dimension is time, then moving one step up from that, the fifth dimension would be alternate realities.  So then we would be in a timeline that is 'yet to discover time travel.'  Our timeline would move up to the point of finding a way to move.  Then, should someone go back in time, they would create a branching reality in which time travelers do exist, and things would move forward parallel to our current, no-time traveler universe.  Without this way of thinking, time traveling encounters the paradox that Back to the Future touches on, that if you changed the 'present' in the past, then the present you might have never existed to change it, or just never have had any reason to time travel in the first place.  The movie just lets the Marty, who is faced with not being born, start to fade out, to cease to exist.  While this works for the film's purposes, it is not reasonable for reality.

But I digress.  I myself believe that time travel is possible, it is simply now a question of application of our theories, which we currently do not possess the proper technology.