One extremely fascinating question is that of whether time travel is scientifically possible, which is somewhat less relevant to this discourse since we wish to view time travel mainly as a conceptual paradigm. Even so, some answers to the above question prove to be of interest. One clichÈd approach is to claim that, if time machines will ever be invented, someone somewhere would certainly have traveled back to our time by now; and as soon as we found out about it, it would be announced as front-page news and emergency broadcasts all over the world. Since that has never happened, time travel will never be possible. The weakness in this logic is that, if we can reason this out, so can the people in the future, who would take great pains to ensure that their ventures to the past would remain as inconspicuous as possible. We are back at square one.
Another, potentially more fascinating, issue revolves around time paradoxes. A time paradox denotes a situation in which the effect of an incident contradicts or eliminates the cause of that same incident. As an example, imagine that in 1990, forty year old John Smith goes back in time and finds his younger self, aged ten, in 1960. Further suppose, for the sake of argument, that forty year old Smith suddenly whips out a gun and violently murders his ten year old self. As a result, ten year old Smith never grows up to become the forty year old Smith because he dies at the tender age of ten. How, then, could forty year old Smith go back in time to murder himself? Forty year old Smith cannot even exist! Thus, the effect of the incident (the murder of ten year old Smith) eliminated the cause (the existence of the murderer). However, things are hardly over yet. Consider the following solution to the problem:
The old Smith murders the young Smith. Consequently, the young Smith never grows up to be the old Smith. Therefore, the old Smith never gets a chance to go back in time to murder the young Smith because due to the chain of events that just took place, the old Smith does not exist. Therefore, the young Smith never gets murdered, because there exists no old Smith who will murder him. This allows the young Smith to grow up to be the old Smith, which allows for the murder to take place, and so on ad infinitum. Once a paradox takes place, time keeps switching between two mutually exclusive quantum branches, unable to ultimately settle on one.
For the record, many scientists use the time paradox concept as a second argument as to why time travel has to be impossible. Since time travel allows for the possibility of a paradox, and since a paradox is impossible, time travel itself must be impossible.
Of course, clicking here to view an introduction to quantum physics, or here to view a scientific analysis of fate, will probably not cause any paradoxes, in spite of the fact that the first link represents the past and the second link represents the future in terms of the contents of the current lexia.
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