If I contend that time travel into the past is not possible in any possible version of future reality that we can access since no time traveller from the future has yet presented themselves to rebuff this contention, can my statements be realistically defended?

This, of course, does not directly rule out future (or past) travel into the future in excess of the local passage of time, but it does preclude the discovery of time portals where we find a way to make relative reference (t-1,t,x,y,z) == (t-1,t1,x,y,z) and also follows that we cannot have (t-1,t,x,y,z) == (t-1,t,x,y,z)1 which does not alone preclude finding a way to teleport (or wormhole) where a plane or an area defined by {(t-1,t,x,y,z),(t-1,t,x,y,z)1} == {(t-1,t,x1,y1,z1),(t-1,t,x1,y1,z1)1}

I would prefer if answers must reference (t,x,y,z) that they also reference t-1 for the scale of spacetime at (t,x,y,z) in the form (t-1,t,x,y,z).

EDIT: Alright, I can see that similar statements have been made previously as shown in answers (not questions!), and by well-known names in science but, that does not explain how this question is a duplicated of another question.

I am not asking, "Is it possible to go back in time?", I am asking "Is this statement defensible?".

  • 1
    $\begingroup$ "Is this statement defensible?" is not a question about physics. (It is not, by the way. Time travel could be perfectly possible, and humanity simply does not last long enough to discover it.) $\endgroup$
    – Chris
    Mar 10, 2018 at 6:11
  • $\begingroup$ @Chris I am inclined to edit the statement, but it already says "... any possible version of future reality that we can access". Perhaps it could say "reach"? Would you categorise the question as philosophy? $\endgroup$
    – Willtech
    Mar 10, 2018 at 12:08
  • $\begingroup$ But, I suppose that the assumptions of the second paragraph carry on a bit further than that. $\endgroup$
    – Willtech
    Mar 10, 2018 at 12:31

1 Answer 1


The fact no future human has visited us could be used as proof, yes. But then again, in a far-off future where time travel has been created, extremely strict rules and regulations regarding usage of it could have been put in place.

That said, it's clear to me that time travel is an impossibility of the highest order.

(I'm sorry that I couldn't answer you in your preferred format).

  • $\begingroup$ We presume if created the ability to do so would not be open-source for public consumption at any future point, and that all who participate adhere to the said strict rules. This alone seems unlikely. I suppose we should not expect any time traveller to necessarily be human, since if we could travel into the past then momentary intergalactic travel would also be possible, although, for the traveller, the passage of time would still be great without the use of hypothetical wormholes. $\endgroup$
    – Willtech
    Mar 10, 2018 at 4:56
  • $\begingroup$ @Willtech Either way, the prerequisite of time travel would be that our lives have completely pre-determined courses, rather than them changing constantly with every tiny move we make. $\endgroup$ Mar 10, 2018 at 5:03
  • $\begingroup$ "That said, it's clear to me that time travel is an impossibility of the highest order." [source required] $\endgroup$
    – Omry
    Mar 10, 2018 at 5:23
  • $\begingroup$ Although I do not agree that our lives are completely pre-determined, if you believe in free thought at least, causality argues that all future events are a result. For free thought to stand one must believe that we, our choices and actions, are ultimately more than a chemical reaction and an electrochemical response. $\endgroup$
    – Willtech
    Mar 10, 2018 at 5:23
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    $\begingroup$ -1: this is no scientific answer - you did not and cannot exam every human being on this earth, and conform they are all not from future. $\endgroup$
    – Shing
    Mar 10, 2018 at 14:48

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