Index * Introduction * What is time travel? * Forward time travel * Backward time travel * It is possible or not ? * Conclusión * Bibliography
Introduction
Physicists take seriously questions about the physical possibility of time travel. This is a matter of consistency of time travel with the laws of nature. This website primarily concentrates on philosophical matters that are even more basic than the issue of physical possibility. There are arguments that seem to show that time travel doesn’t even make sense, that it is illogical, that it is contradictory. Proponents of these arguments think that time travel is impossible no matter what the laws of nature are. When apparently sound reasoning leads to a contradictory conclusion, a paradox is the result. Many paradoxes arise in the consideration of time travel.
Time travel
Time travel is the concept of moving between different points in time in a manner analogous to moving between different points in space, generally using a theoretical invention known as a "time machine". Time travel is a recognized concept in philosophy and fiction, but has a very limited support in theoretical physics, usually only in conjunction with quantum mechanics or wormholes. Time travel has been a popular topic for science fiction for decades. Franchises ranging from "Doctor Who" to "Star Trek" to "Back to the Future" have seen humans get in a vehicle of some sort and arrive in the past or future, ready to take on new adventures. The reality, however, is more muddled. Not all scientists believe that time travel is possible. Some even say that an attempt would be fatal to any human who chooses to undertake it.
Forward time travel
Going to the future is better than going to the past, because is more complex and difficult so if you modify the past the things as we know it will not exsist, probably you will not exsist. To travel forward in time, an object needs to reach speeds close to the speed of light. As it approaches these speeds, time slows down but only for that specific object. It's impossible to travel to the past, though, as seen in Back to the Future, pictured, You can go into the future; you've got almost total freedom of movement in the future.
If you go fast, your clock runs slow relative to people who are still. As you approach the speed of light, your clock runs so slow you could come back 10,000 years in the future. The theory is based on Einstein's Theory of Special Relatively that states to travel forward in time, an object would need to reach speeds close to the speed of light. As an object approach these speeds, time slows down but only for that specific object travelling. For example, people flying over the Atlantic will experience time passing marginally slower than people on the ground.
Backward time travel
It may be imposible to travel backward on time, Traveling into the past is “difficult,” the author admits and there is one, crucial, limitation - you cannot travel back beyond the point when the first time machine is invented. As you get close to that speed, time slows down, but only for you, according to Einstein’s Theory of Special Relativity. Travel far enough, and you could return thousands of years into the future. Travelling backwards, though, is much, much harder - but still, “possible”.
You can use a wormhole but you have to create it, you can used it to go backward in time, you simply have to attach one end of the wormhole to a spaceship, fly around at near the speed of light for a while (so time slows down for the spaceship), then jump through the wormhole. If the spaceship flew for five years, only six months would have passed within the wormhole - so if you jump through it to the alien star, then fly back to Earth (on yet another spaceship), you arrive three months before you left. Because you rely on the wormhole, you can’t go further back than when the machine is invented - hence, perhaps, the reason we have never seen any time travellers. Either that, or the sheer amount of effort involved.
It is possible or not?
While time travel does not appear possible — at least, possible in the sense that the humans would survive it — with the physics that we use today, the field is constantly changing. Advances in quantum theories could perhaps provide some understanding of how to overcome time travel paradoxes. One possibility, although it would not necessarily lead to time travel, is solving the mystery of how certain particles can communicate instantaneously with each other faster than the speed of light. In the meantime, however, interested time travelers can at least experience it vicariously through movies, television and books.
Conclusion
We define time travel to mean departure from a certain place and time followed (from the traveller's point of view) by arrival at the same place at an earlier (from the sedentary observer's point of view) time. Time travel paradoxes arise from the fact that departure occurs after arrival according to one observer and before arrival according to another. In the terminology of special relativity time travel implies that the timelike ordering of events is not invariant. This violates our intuitive notions of causality. However, intuition is not an infallible guide, so we must be careful. Is time travel really impossible, or is it merely another phenomenon where "impossible" means "nature is weirder than we think?" The answer is more interesting than you might think.
