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It is commonly thought that forward time travel is more logically possible than backward time travel.

Does the following raise a paradox to forward time travel:

Tim goes 20 years in thee future to see he is happily married. Now, if he can't go back in time to his original time (and is stuck 20 years in the future), who marries his wife?

So he does and does not marry his wife? Is this a contradiction?

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    Forward time travel is happening now. When you travel forward in time faster.. you simply disappear from the lives of your friends (get on your spaceship). For them time happens ordinarily. You then appear in the future looking younger than them. So you couldn't meet yourself.. there is no other you to marry your wife.
    – Richard
    Dec 4, 2018 at 11:30
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    Time travel is exclusively a mental activity. The mind is not accompanied by the physical body during time travel activities. The mind is capable of such travels, but the physical body is quite limited, and couldn't endure the stresses involved. Just as when dreaming the physical body isn't really involved.
    – Bread
    Dec 4, 2018 at 12:06
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    Also, I suspect any actual mental time travels are rare and almost completely triggered subconsciously. Conscious efforts may help you along, but it is probably the subconscious that does the actual work.
    – Bread
    Dec 4, 2018 at 12:19
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    If going back in time is impossible, then Tim would have never married since he would not have returned back from his trip into the future.
    – EternalPropagation
    Dec 4, 2018 at 20:54
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    Tim can do what you describe by accelerating at relativistic velocities, he'll "travel" 20 years ahead while aging a few minutes (because time runs differently at high accelerations). Obviously, he'll have to abandon his wife to do it. The same effect is played out in the twin paradox.
    – Conifold
    Dec 4, 2018 at 21:49

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There is no paradox. By travelling in time for 20 years, Tim effectively removes himself from the Universe for that time, much as if he were in some form of suspended animation. Therefore, he doesn't get married during that time. Either he was married when he left, and his wife is happy to see him back, or he doesn't find he's happily married.

An alternate interpretation would note that I did exist in 1978 and was unmarried, and after traveling forty years into the future I am happily married. Since I traveled at mostly the same rate as everyone else, I was able to do things, like marry someone, on the way.

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Let us look at a model of what is happening.

Tim

-----xxxxxxx-------------------|

Husband (Tim)

??????------------|

Wife

----------------------|

One must explain the past of the husband in order to provide a coherent scenario. Here are two scenarios in which the above occurs that do not contain the specified contradiction.

Suppose the existence of parallel universes which contain largely agreeing events. Then traveling to the future of another universe in which Tim decided not to travel in the future could yield this result. For the time traveling Tim originated elsewhere than the happily married Tim.

Suppose that 20 years in the future, someone created a copy of Tim from the past. The copy has all of Tim's properties from that time. Then according to the copied Tim, he traveled to the future since there were no intermediary experiences from then to now. But we still must think of copied Tim as Tim since he possesses all the properties that would identify him as Tim by assumption.

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The problem is that, unless time travel is actually just moving to a different universe, Tim would be absent for 20 years, so there would be no Tim that his wife could have married.

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It is, I believe, unwise to construct a time traveling mechanism that would allow humans to traverse the past and/or the future.....(even if it is only for a few minutes).

The technical ability to circumvent the units of time-(i.e. cutting temporal corners), would radically disrupt our existing timeline and in all likelihood, devastate the temporal process leading to a series of "unintended consequences". The experience, while initially fascinating, would be way too bizarre and incomprehensible for our human intellect, as well as our emotional well being to handle.

My advice to "Tim", is avoid actions that may be irreversible and negatively consequential. In other words, try to remain in the present....and wait a while.

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    It's not that you would build a contraption that alters reality, either reality has always allowed for such a contraption to exist or it didn't. And in terms of forward time travel for the rest it would be as if you were on a long journey and returned to a place that changed during your absence whereas for you that journey was way shorter or was done unconscious like coma. Backwards time travel is harder to conceptualize but the paradoxes most likely only arise because we imagine it wrong. And staying in the present is an irreversible action with potential negative consequences as well.
    – haxor789
    Jul 6, 2022 at 9:43
  • Let the past remain as the past, let the present remain as the present and let the future remain as the future.
    – Alex
    Jul 6, 2022 at 18:29

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