quarta-feira, maio 31, 2006

Do you believe in Time Travel?

Time travel: "is the concept of moving backward or forward to different points in time, in a manner analogous to moving through space. Additionally, some interpretations of time travel suggest the possibility of travel between parallel realities or universes."

Some theories are applied concerning time travel and all suggest that spacetime, or kinds of motion in space (if possible), will allow time travel into the past and future. There's a theory that sustains that time appears more slowly for faster-bodies, like for example, a moving clock will appear to run slow; as a clock approaches the speed of light its hands will appear to nearly stop moving. The effects of this sort of time dilation are known as the twin paradox.

Some other (fragile) theory sustains only that time travel toward the future: never backward. However, there are thinkers who argue that all the matter of the universe only exists in the present moment. Thus, if one were to travel back from the "present" to an earlier time, none of the material universe would be found there, because it will have remained in the present. Regarding a 4-dimensional spacetime, the traveller would have travelled "back" to an area of spacetime corresponding to an earlier value, but none of the other particles that form the universe will have done so, so the traveller finds precisely nothing when arriving back at the earlier time, which eliminites all the paradoxes about time travel.

Let us suppose that one could even go back in time. Returning back what would happen to the traveller if he/she killed his/her biological grandfather before he met his wife (our traveller's grandmother)? Then if the traveller did that, he/she would never have been conceived, so allowing traveller to go back in time isn't possible at all.

Another resolution seems to appear to solve/confuse more this problem. This theory holds that if one were to travel back in time, the laws of nature (or other intervening cause) would simply forbid the traveller from doing anything that could later result in their time travel not ocurring. Taking the example above, a shot fired at the traveller's grandfather will miss, or the gun will jam, or misfire, or some other event will occur to prevent the attempt from succeeding. With this, traveller will be unable to change history.

Opposite to this, we can regard this example: if one traveled back to the year before its birth to kill its parents and prevent its birth in the next year, that one wouldn't disappear from history, because simply by travelling back to the year before its birth, that persona would have established that he/she already existed in its adult form, complete with memories, in the year before its birth. In effect, traveller would have prevented nothing but a redundant, younger copy of itself from co-existing with him/her. Going back in time to prevent the premature existence of itself would likewise only push back the time at which the existence of itself was historically established.

One thing we could be certain (at least we want to believe in it), we live in our present with memories of our past and projecting our future to come, of course we could doubt about the veracity of that past memories or even doubt if they truly ever existed or was/has been our mind that has been creating it. But we must rise our heads and live Under our Milky Way, while we (still) have Time.