Time Travel

Time travel, philosophy and whether it is possible

When you think of time travel, what image comes to mind? For most people, an image is instantly conjured up in the minds eye of someone getting in to a vehicle that accelerates at speed or spins around very rapidly, and then suddenly appears at some future time and place. Such is the way time travel is portrayed in film, with the implication that the traveller and their wonder-vehicle are somehow taken 'outside' of space and time then dumped back in at the future (or indeed past) time and place.

One element is correct - the need for speed, and realistically too, some sort of vehicle is needed to allow a human to time travel as speed is of the essence. But what is this more scientific form of time travel? It comes down to relativity. The faster something travels, relative to some other point of reference, the less time is experienced to pass relative to that other frame of reference. Although for you time appears to be passing normally, it does not appeared to be slowed down as you might think, nor indeed speeded up. Thus if it were technically possible for you to travel in a space vessel at near light speed during the time you measure to be one year passing you would be shocked on returning to earth to see that a much longer period of time had passed there, and your relatives may be long since dead if you were appreciably close to light speed.

There are a couple of interesting points to note here.

Firstly, it seems a little different to what we might intuitively consider to be time travel to the future. We don't have the odd but characteristic journey where we somehow instantaneously move from one point in space and time to another, as happens in films like back to the future or in literature in books like the Time Machine. However, upon reflection, it appears the results accord with what would be an acceptable idea of time travel.

The second point of interest is that this is not science fiction but science fact, and it has been observed in practice rather than thought to be just theoretically possible. For instance, two very accurate clocks can be synchronised, with one sent into orbit around the earth and the other left on the planet. After a period of time, it is seen that the two clocks are out of sync and that the one in orbit has experienced the passage of less time than that on earth, it runs 'slow' relative to the one on earth. This is because it has been moving much more quickly, and therefore experiences the passage of less time. Also unusual particles in cosmic rays last a lot longer than they should because they are moving so fast that their life expectancy, as it were, is increased. This is a very interesting thought indeed.

All this is of course relating to time travel to the future. But what about travel to the past? This is a lot more contentious. Whilst some invoke exotic ideas such as wormholes to create ways of moving from one time and place to another by travelling the relativity short distance through a wormhole, it is important to realise that in these models you cannot go back in time before the creation of said wormhole itself.

For some this gives a satisfactory answer to the "where are they" question famous from ET seekers when it is applied to humans travelling to the past from the future: the answer is that, if backward travel is possible at all, it is only possible back to the time when the first wormhole is created.

For many, the idea of travelling to the past opens up a can of worms, nevermind wormholes, and some expect it would require unresolvable and illogical causal loops, involving shady concepts such as backwards causation and more besides.

There are a cornucopia of well-known paradoxes that that associated with backward time travel, not all of which are related to the grizzly idea of killing your forebears for instance. One interesting paradox is to do with the creation of new knowledge out of thin air, whereby your future self travels back to the past and tells your earlier self how to create a time machine, for instance. This seems to suggest the genesis of new information out of the either, without a clear cause.

Whilst backwards time travel cases can be made to avoid these obvious paradoxes, a convincing account needs to be given of why these situations could not occur at all - the universe would seem to have to rule them out somehow. The often invoked appeal to parallel worlds or universes does not clearly seem to be of much help but can just shift these paradoxes into parallel worlds instead! Some scientists now believe that time travel to the past is actually impossible and banned by the universe, so to speak, though exactly how this is the case is not clear at the present time.

So there you have it. That is a brief overview of time travel to the past and future - feel free to leave your own thoughts, ideas and contributions on this fascinating topic!

Time Travel

Author: Dan moore

About the Author:
More About the Author >>> | My other pages >>>

Page Views: 1566 | Page Ranking: 114
Popular Tags:
time travel,philosophy,physics

Last Updated: Aug 26th 2009

Ask Dan moore a Question >>>

Category: Philosophy [More Categories]

Article Comments / Questions

No comments have been added to this question.
Comment on this Article