Time travel is defined by dictionary.com as the hypothetical transport through time into the past or the future. Although most believe this to only be possible in science fiction books and movies, the truth is that it may be more than just a silly plot in a book.

Time travel is the concept of moving backwards and/or forwards to different points in time, in a manner analogous to moving through space. Additionally, some interpretations of time travel suggest the possibility of traveling between parallel realities or universes. Time travel has been a common plot device in fiction since the 19th century. Although, one-way travel into the future is arguably possible given the phenomenon of time dilation (the phenomenon whereby an observer finds that another's clock which is physically identical to their own is ticking at a slower rate) in the theory of relativity.

Physicists take for granted that if one were to move away from the Earth and return, more time would have passed on Earth than for the traveler, so in this sense it is accepted that relativity allows travel into the future. Although, according to relativity there is no single objective answer to how much time has 'really' passed between the departure and the return. On the other hand, many in the scientific community believe that backwards time travel is highly unlikely for any theory which would allow time travel would require that issues of causality be resolved. For example, what if one were to go back in time and kill one's own grandfather before one's father was conceived? This idea is referred to as the Grandfather Paradox, the main argument involving backwards time travel which claims the journey impossible.

On the more negative side of the plausibility of time travel, Stephen Hawking has suggested that the absence of tourists from the future constitutes an argument against the existence of time travel. Of course this would not prove that time travel is physically impossible, for it may be, simply that it is never in fact developed. Even if it is developed, Hawking notes that, “time travel might only be possible in a region of space-time that is warped in the right way, and that if we cannot create such a region until the future, then time travelers would not be able to travel back before that date.” This picture would explain why we haven't been over run by crazy tourists from the future.

Lastly, the experiment of Lijun Wang may give more insight on the potentiality of time travel. Wang made it possible to send packages of waves through a bulb of cesium gas in such a way that the package appeared to exit the bulb 62 nanoseconds before its entry! His experiment resulted in the package of waves actually traveling faster than the speed of light, which is why the package of waves supposedly exited the bulb before it entered.

This idea of traveling through time has been and still is an important one for the simple fact that if this does now, has, or will exist; the balance in the world and perception of truth will most certainly change. Are those who believe in time travel crazy? The theory cannot be proven either way, so the answer is no. Believers in time travel are not mental and if that is the general consensus, then those who dismiss the idea without knowing any fact or theory are in the same boat. After all, anything that cannot be proven completely is simply a thought and will always remain that way. Therefore, time travel is still up in the air (no pun intended) when it comes to its existence and, until proven physically possible or impossible, is simply a theory that many wish they held the key to knowing.