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I just wanted to know whether time dilation is different from time travel or not. Personally I believe both are different. If they are the same things I just wanted to know why. According to me time dilation is something that applies for every object, while time travel particularly applies for humans. Moreover I feel that travelling through time also in a sense means being able to control time. Time dilation is just an effect due to special relativity and I think it is often confused with time travel. Time travel can be based upon time dilation but I do not think that it completely implies the same thing.

EDIT By time travel I mean like exact travelling. Like you can go in any direction. Similarly I mean into the past as well as the future. But I just wanted to know if there is a general difference since everyone could define time travel in a separate manner.

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    $\begingroup$ I think you need to define what you mean by time travel. $\endgroup$ – John Rennie Feb 3 '14 at 13:08
  • $\begingroup$ Re your edit: time travel in the sense you mean doesn't exist. $\endgroup$ – John Rennie Feb 3 '14 at 13:12
  • $\begingroup$ I am not saying it does not exist but its something I can't seem to understand in terms of the difference. It would be good if you can edit my question according to what you think. Thanks :) $\endgroup$ – rahulgarg12342 Feb 3 '14 at 13:13
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Time dilation and time traveling are completely different concepts, in the sense : time traveling : AS i know it , it is a hypothetical phenomena which involves in moving frome one space-time to another , it also includes moving to a different time from the starting point (future or past) irrespective of speed or mass of the object moving.

time dilation: using a very famous exapmle as i remember it of twin , one of the twin takes off from the Earth with the speed of light ,and returns say after one year . for the twin who took off , time remained constand and when he returns ...he will be a year younger than the twin who stayed . (relativity)

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Time dilation can never put you into the past. Whether or not it's moved you into the future depends on philosophical arguments. Getting to some future date while not having physically aged the appropriate amount could be considered travelling into the future, but other philosohers (or Sci-Fi troublemakers) will point out that all of us are travelling into the future.

A related fallacy (often used in semi-sci-fi stories) is that you cannot travel backwards in time simply by going faster than light. -- not that we have any solid reason to believe anything can go faster than light in the first place -- Even at, say, 10x lightspeed, it'll still take a year, externally observed, for you to travel 10 light-years. You can't get there before you started.

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    $\begingroup$ Should that read, A related fallacy .. is that you CAN travel...? $\endgroup$ – innisfree Feb 3 '14 at 16:17
  • $\begingroup$ @innisfree yeah, it should. Shame on me for mangled grammar. $\endgroup$ – Carl Witthoft Feb 3 '14 at 17:26
  • $\begingroup$ So I believe you do find them different, right? $\endgroup$ – rahulgarg12342 Feb 4 '14 at 11:42
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It would séem to me that just because the timescale of the ship does not match the timescale of the original frame, does not ,a priori, mean that you have actually traveled into the future. Just that you experienced the "trip" differently than those in the slower frame. So dilation is not travel,

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Consider what the transformations time translation and time dilation do to an object (for example a clock). These transformations are different. They do different things to an object, and are done differently by you.

When time translation is done to the clock, the transformed clock has its hands changed to a new position compared to the initial clock. You do the time translation transformation by simply waiting. For not perfectly understood reasons, you can only time translate the clock into the future (ie: advance the hands of the clock).

When time dilation is done on the clock, the transformed clock ticks at a different rate compared to the initial clock. You do the time dilation transformation by boosting the clock to a velocity. You can also do the time dilation transformation by moving the clock into (or out of) the gravitational field of a mass. The time dilation transformation can be done in both directions, either squeezing the time between the ticks or stretching the time between the ticks.

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