Way can we not travel in time?  If time can move forward, way can we not go back in time?
114656
It's not necessarily impossible according to theory, but given our current technology, it's out of the question.  There's a lot of trouble with time travel theory, including multiple paradoxes.\n\nThe most famous paradox is, of course, the grandfather paradox.  It goes something like this: One day, after you've built your time machine, you decide to travel back into the past to shoot your grandfather before your father is born.  Here is the major paradox, if you suceed in killing your grandfather, you couldn't be born to go back and shoot him.  Just as well, the conditions required for you to shoot him couldn't exist and thus he lives.\n\nStill on the 'travel back in time to shoot grandpa' string, several other things could happen as well.  You could be transported to an alternate timeline, similar to ours, but not ours, and whatever you do there doesn't affect anything in our time line.  You could go back and try and kill your grandfather, but you are thwarted in every attempt, which tends to imply some sort of destiny or grand scheme.  You could try to go back in time but are ripped to shreds because every fragment of your being wants to be in its natural time.  There's a million and one other things that could happen.\n\nThat, I believe, is not necessarily answering your question, though.  Time itself is not understood by physicists even now.  What it is, no one is quite sure!  (However, I'm fairly certain time is related somehow to mass.)  One thing that's always for certain is time moves forward in a very linear fashion, cause followed by effect otherwise called casaulity.  I can't say one way or another why exactly we can't go back in time and I won't say it's not possible, some theories say it is.\n\nHowever, I believe Stephen Hawking offered up the best proof against time travel to date: Wouldn't there be time tourists from the future visiting us if time travel was feasible?
386007
yes, and that's why it's impossible to time travel (no going past the speed of light either)
945559
Relativistic time travel is possible. Time passes more slowly for an observer who is in motion relative to one that is at rest. The next trick is to define which is which, which is why Einstein won the Nobel Prize (although it actually wasn't for relativity, but that's another question).
50046
I agree with the above answer....but think about this for a second.....if time travel ever becomes possible...we would all travel back in time to clean up stuff and change what we think we need to.....and since no one has shown up to change anything recently.....it just shows that time travel will never happen....
186287
Under Einstein's General and special theories of relativity, time travel is considered possible. Stephen Hawking has speculated that it must not have been discovered to be practical as we have not seen tourists coming from the future to visit us.
900982
Reverse time travel is impossible, but believe it or not, forward is 100 % possible. Then an object reaches an extremely high speed, near the speed of light, Time around it will go slower and the object willgo forward in time faster than everythng else. Astronauts in the space shuttle also travel throught time, but because their speed is only a tini fraction of the speed of light, their time travel is nearly unnoticed.
1044156
Einstien came up with a theory which was by moving very quickly, beyond humans fathomable grip on speed, you can actually stop time and if faster then that, go BACK in time. crazy huh? well if its ever true, we wont know, cause no one in the future in their right MIND would ever want to go back in time to the 20th century. come on. why not stand in the crowd and watch jesus being stoned while carrying the cross or go back further to live amongst the first civilzation of man.
84170
the answer is - it depends - on a lot of things\n\nI hate to answer a question with a question but here goes ...\n\n- do you mean in theory or in practice ??? (in [einstein's relativity] theory it is possible to travel into the future - all you need to do is to go out into space for a while - the time here on earth will continue to progress at a normal pace while time for you will progress more slowly - when you come back you'll have essentially traveled into the future - not quite a time 'machine' but same effect
68159
it is not that confusing. About three year ago on PBS there was a program that talked about time travel and one of the scientist stated that even if we could travel back in time we coul donly travel up to the point when the time machine was invented.\nBut do not forget there are manyh theories about time travel. For instance the grandfather paradox claims that you could not travel back in time, but others say you can but in a different dimension.
1131993
My opinion is that in order to travel through time we would need to be able to travel uncalculable extraordinary distances.\n\nImagine how fast the earth is moving through space. Not only would we need to calculate the speed of the Solar System; but the speed of the Milky Way Galaxy; the speed of the Universe; and in which direction.\n\nWhy would we need to know this? We would need to be able to travel to the actual physical position in which the Earth would be located at the time in which we were desiring to be present.\n\nIt is my opinion that if it were not for the fact that we are traveling at such and such a speed that "Time" itself would not be possible in the first place.\n\nThe fact that physical matter is never in the same location;;;EVER;;; is what I believe makes the existance of matter a possibility.\n\nImagine that if the Earth were a hundred miles away from its current location in just one small second of time. To travel back one second in time you would have to travel that one hundred miles of distance.\n\nWould the Earth be there if you could travel that distance? Some scientists want to believe that "worm holes" can link up huge distances in space by folding or warping space, distance, and time. \n\nI personally believe that God has the power to time travel; or how else could he know the future in order to prophesy; and I do believe he has proven the ability to prophesy. Yet, did he time travel, or did he make things happen according to his prophecy?\n\nOk; if God exists in the future; or at the end of time (the furthest point in which time has yet reached since the beginning of all time) and has the ability to travel back into various points of the timeline; he then has the ability to travel forward and backward in order to see how well things are going according to his own actions.\n\nSo then, Jesus would have seen everything before it ever happened. I also take into account that God must have the ability to be larger than the Universe and smaller than the smallest forms of energy and matter if he were truly capable of producing and controlling them.\n\nYet affording us free will is what allows us to be who we are.\n(see references below)\n\nIs it possible that matter is frozen in time at every location along the path of which it travels? In other words; Is our history preserved as if it were a tape or recording throughout all of its existence? It does not seem possible; but anything is possible with God. Maybe this is where the "Missing Universe" energy is located; frozen in time. If this were true than I believe it may be possible to time travel. One would have to have the ability to travel amazing distances at amazing speeds.\n\nI would have to believe that traveling into the past would be possible under the circumstance that matter becomes frozen in place as it travels and that a person could travel such distances and had much time available for the journey.\n\nSo if traveling into the past were possibe; because the past would be there; whereas the future may not be yet, would traveling into the future be possibe?\n\nAfter traveling backward, surely we could then travel back to the future from where we just came from. This theory would conclude that we exist in the "real" present and the future really has not happened yet.\n\nSo traveling into the future could only happen if we first traveled back into the past, and then went back to the future.; where we came from.\n\nSo lets say someone else traveled back from the future (which has not happened yet to us; because at which point do we cease to be the "real" point in which time has already existed?) into our present time. We would have to consider that if God really does prophecy by time traveling, then we do not currently live in the "real stream of time"; but time and history has already taken its course and has already been fulfilled.\n\nIn other words; we do not live in the real present; but
737000
Time travelling is a very difficult topic.\n\nYou can supposedly travel into the past if you travel faster than the speed of light but this involves getting a source of infinite energy as when matter gets closer and closer to the speed of light its mass will dramatically increase.\n\nThis is said to be very unlikely but general relativity says it may be possible on highly unusual circumstances.\n\nWormholes, permitted by general relativity,  could be possible only if it is traversable.\n\nIf you read general relativity and objects at speed of light you get time, space and gravity based dilations where light appears to be bent by gravity and arrives at an object at different times.\n\nYet again the object has to be travelling at 0.99c or faster!!\n\nI says time travel will never happens but i wish it would.
680669
we r travelling at 1 second forward per second.\n\nIf that's not that u meant, the easiest and most likely way to get a time machine to time travel is for yourself in the future to travel back now to give yourself the time machine now which u got in the "past" from the "future yourself" coming back to gave it to u.
1186042
That's the problem. You can't go beyond the speed of light. It is the cosmic speed limit. But if you could, then you'll be able to travel through time, past and future.
1139606
Im afraid I do not think time travel is possible.  Einstein’s theory says that as you move faster time slows down.  The problem lies in getting to a speed that is so fast that time actually moves backwards.  Anything with mass cannot reach the speed of light, because as its speed increases the amount for energy required to push it increases, so it would take an infinite amount of energy for something with mass to reach the speed of light.  Photons have a zero-mass and therefore light can travel at... well the speed of light :)\n\nSo if it was possible to break ourselves down into zero-mass pieces then it would be possible to travel the speed of light.  What is unknown is if you could travel so fast that you could actually "turn back time" which I do not believe is possible.  Or else we would see people from the future already coming back to the past.\n\nAnd then you would get those crazy little problems of ... if you went back in time and killed yourself at say 12 years old.   How would you have ever been old enough to actually travel back in time to kill yourself... because you would have been dead...\n\nIt could be possible to slow time down in relationship to yourself, so that the earth ages faster... If you consider that time travel.  Say for example you get into your space ship, and travel near the speed of light, then the earth would age faster relative to you.  If you consider that time travel then yes I believe that is possible.  But the thought of going forward, and back in time is not possible in my humble opinion.
1152446
Well this one is interesting.  Mathematics tell us that to move in time, one must move faster than the speed of light.  There are particles that do move that fast so it is theoretically possible.\n\nWith that having been said, I'll go back to the particles that move faster than light.  These particles cannot be seen or measured in any way that we can figure out but we know that they exist because of the reaction of other things.  ( its like the wind blowing,  you dont see it but trees and stuff react to it )\n\nOne theory suggests that if we do manage to travel back in time,  we wont be able to interact with it at all. ( I dont understand all the mechanics on this one)  But it would be like being an invisible ghost.  You could observe things and events but couldnt make actual physical contact with anything thus you couldnt change events.
409498
By traveling faster than the speed of light.  As velocity approaches the speed of light, time slows down.  Traveling faster than light speed then - would make you travel back in time.  Theoretically, it is possible (according to the theory of relativity) but scientifically, it doesn't seem possible.
721881
I dont think time travel is possible! Even if you were to go faster than the speed of light, it still takes time to get to where you are going. And that brings up another question, where do you go?? Do you zoom around the planet a few million times? Which direction? Does it matter, it still takes TIME to do it.\n\nJust for argument sake, lets say you could go back (or forward) in time. I dont know why you couldnt be seen, you just traveled to a different time and when you get there your there, just as if you were to travel to a different city.