Question

is time travel possible or is it just fiction?
i heard many people say it is not true...so i was just wondering..

Answer 1

wat do u think abt it ?

Answer 2

i heard dat individual photons can't travel @ d speed of light.so it is impossible...i mean,i dont wanna disprove any1.. :)

Answer 3

In Wikipedia (again :-) there is a very good and well-sourced article:
http://en.wikipedia.org/wiki/Time_travel

Summary: the problem is unsolved, and there are theoretical arguments for and against. I personally think that it is impossible, especially backwards, because it would ruin causality.

Answer 4

photons do travel at the speed of light. Photons are light ! But massive objects like you or me cannot travel that fast because it would take an infinite amount of energy to accelerate us to that speed. Due to Special Relativity the faster we go the heavier we are and the harder it is to go faster. And the only way we could go back in time would be to travel faster than the speed of light which i just stated was impossible. However we can go ahead in time if we say left earth traveled around say the rim of a black hole and then returned, we'd be looking at a planet of the apes kinda thing (the old movie). Where a year for the space traveler is a century for the planet earth.

Answer 5

Travel into the future will be possible, but travel into the past will never be. Should that be possible in the future then it would have occured and we would have seen the proof via a return visit. I would be impossible for future generations to do a secret return visit without politicians screwing it up and revealing themselves.

Answer 6

We do not know if time travel is possible. Certainly there are some solutions within certain theories that permit for teh possibility of time travel, but only under certain conditions which may not apply to our universe.

For example, the mathematician found solutions to Einstein's General relativity field equations which permitted one to travel back through time as one travelled through space. These solutions are known as "time-like curves". However, in order for this solution to work, the universe as a whole must be cylindrical in shape, and be rotating about its central axis: properties which are not thought to be likely, and not experimentally verified.

Another proposed form of time travel, was found in the Kerr solutions of black holes. The Kerr solution refers to a spinning black hole, and may permit travel through its singularity. see this post http://openstudy.com/groups/physics#/groups/physics/updates/4e328b870b8ba7b2da416e0b for more details on Kerr black holes. Depending upon the path you take through such an entity could mean when you exit it, you could be in a different time (past or future), or in a different part of the universe (or a different universe entirely).

The Kerr solution is similar to that of a wormhole. A wormhole is like a tunnel between two points in space-time but existing in a hyper-dimensional space. As such it has two mouths. If you were to create a wormhole such that you could move its mouths through space, then you could create a time-machine. Relativity states that the faster you move (i.e. the closer to the speed of light you get), the slower time would flow for you. This would mean that the rest of the universe would be travelling into the future faster than you, so you may experience only 1 year of travel, but 100 years have past in the rest of the universe.

If you could move one mouth of a wormhole at relativistic velocities in your spaceship (leaving the other mouth on earth), then the earth mouth would be moving into the future faster than the one on your spaceship. In the example above if 1 year has passed for you and your wormhole mouth, and 100 years for the rest of the universe (including the other wormhole mouth), then you have a time machine. Someone on earth could step into the wormhole and move 100 years into their past. Conversely, someone on the space ship could step into the wormhole and step 100 years into the future. Note though that in this type of wormhole, time travel is restricted between to points in space, and to 2 points in time, and you cannot travel back in time to a point before the wormhole/time machine was created. This latter point is important, as it means that if this is a viable form of time travel, then we wont see people from the future at this moment in time.

The problem with teh above mechanism is that it assumes wormholes exist in nature. Again they are a theoretical solution to a set of equations, but we have no evidence that wormholes can exist. Secondly, if they do exist then the theory suggests that the presence of mass near to or passing through the mouth should cause it to collapse, and thus in order for it to exist and remain open, an exotic form of mass/energy is needed. Again there is no evidence or reason for such exotic matter to exist within or universe, and so these ideas are purely interesting theoretical exercises.

The general belief in physics is that time travel into the past is not possible (forward travel is, as we are all doing it right now, and the rate depends upon velocity), but that hasn't stopped physicists from investigating possibilities, and it will only be the universe that tells us what is possible or not.

Answer 7

Just noticed there that I forgot to put the name of the mathematician who discovered time like curves into the text. His name was Kurt Godel.

Answer 8

thank u all for these wonderful information. u all are so brilliant, that i think, if everyone on OS tries together, we can make our own time machine... :)