# New Research Shows That Time Travel Is Mathematically Possible **URL:** \ **Category:** Factual Questions\ **Created:** [March 8, 2018, 8:26am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228 "2018-03-08T08:26:27Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![DrCube](https://avatars.discourse-cdn.com/v4/letter/d/a3d4f5/32.png) [@DrCube](https://boards.straightdope.com/u/DrCube)\ **Post date:** [March 8, 2018, 3:35pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/21 "2018-03-08T15:35:01Z")
The number of things that are _mathematically_ possible is inconceivably large. That’s no argument for actual existence or physical possibility. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 8, 2018, 3:47pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/22 "2018-03-08T15:47:19Z")
[Moderating] > [@](#): > > Oh, look, it’s the same “bored-ninja.tk” site as OP’s last (locked) post. OK, I’m convinced. ---
**Author:** ![Stranger\_On\_A\_Train](https://avatars.discourse-cdn.com/v4/letter/s/13edae/32.png) [@Stranger\_On\_A\_Train](https://boards.straightdope.com/u/Stranger_On_A_Train)\ **Post date:** [March 8, 2018, 4:03pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/23 "2018-03-08T16:03:11Z")
> [@MetalHeader](#): > > What do you think about time travel? I personally think that it’s quite possible after reading this. [“Rotating Cylinders and the Possibility of Global Causality Violation”](http://www.isfdb.org/cgi-bin/title.cgi?50243). Mucking about in the timestream is never a good idea. You start with the best of intentions and end up destroying your star system, because Fate is a harsh and relentless bitch who does not like to be told what to do. Stranger ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [March 8, 2018, 4:36pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/24 "2018-03-08T16:36:48Z")
I’m traveling through time as I write this post. The secret is to maintain a steady pace into the future. ---
**Author:** ![Buck\_Godot](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/buck_godot/32/6573_2.png) [@Buck\_Godot](https://boards.straightdope.com/u/Buck_Godot)\ **Post date:** [March 8, 2018, 4:43pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/25 "2018-03-08T16:43:18Z")
> [@wolfpup](#): > > Suppose that this were the case, instead of the “free will” that you believe in. **How could you possibly tell the difference?** How could you, a mere biological creature capable only of subjective judgments, tell whether or not everything you were about to do, and the future of the entire universe, was already predetermined? But I’m not actually sure that actual free will as opposed to the illusion of free will is actually required for contradiction. If I had a time machine the first experiment I would do would be to ro write the letter “A” on a piece of paper. I then would go back in time and tell myself what I had written, at which point the old me would write “B” on the paper, and proceed with the experiment. But when I go back and tell myself I wrote “B” I would poeceed to write “A”, etc. Was “A” or “B” actually written? Bingo we have a causality paradox (and nobody’s grandfather has to get killed.) Now it could be because I had free will that I decide to be contrary in this way, or it could be because of the programming of my neurons. But I guarantee that this is what I would do. And because it is the obvious expriment, so would pretty much any other researcher who would develop time travel. Either through free will or because of their programming. So unless there is some cosmic gate keeper who is going to reprogram any brains to prevent them from acting this way (which in my opinion would be a bigger discovery than time travel itself), you still have to deal with the paradox. ---
**Author:** ![Riemann](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/riemann/32/3133_2.png) [@Riemann](https://boards.straightdope.com/u/Riemann)\ **Post date:** [March 8, 2018, 5:14pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/26 "2018-03-08T17:14:30Z")
> [@Alessan](#): > > Putting free will aside, the question of whether the universe is predetermined also depends on whether or not God does, in fact, play with dice. If the universe does indeed feature a random element at the quantum level, then there’s no such thing as “the” future. A billion billion billion different futures, maybe, but not just one. Why? The fact that a path is stochastic does not imply that all possible paths in the distribution actually occur. Many worlds is only one possible interpretation of QM. ---
**Author:** ![bardos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bardos/32/1069_2.png) [@bardos](https://boards.straightdope.com/u/bardos)\ **Post date:** [March 8, 2018, 5:40pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/27 "2018-03-08T17:40:14Z")
We are all time travellers already, we are travelling through time together. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [March 8, 2018, 6:53pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/28 "2018-03-08T18:53:41Z")
One possible resolution to the “Grandfather Paradox” is that any time you try to set up such a paradox, something happens (possibly with no apparent causal relationship to what you’re doing) that prevents it. Maybe, for instance, you just happen to die of a brain aneurysm just as you’re about to tell your previous self what you wrote. The aneurysm wasn’t exactly caused by your time travel, but timelines where the aneurysm didn’t occur simply don’t exist. ---
**Author:** ![FlikTheBlue](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/fliktheblue/32/10972_2.png) [@FlikTheBlue](https://boards.straightdope.com/u/FlikTheBlue)\ **Post date:** [March 8, 2018, 6:54pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/29 "2018-03-08T18:54:33Z")
> [@bardos](#): > > We are all time travellers already, we are travelling through time together. At a speed of one second per second 🙂 ---
**Author:** ![gazpacho](https://avatars.discourse-cdn.com/v4/letter/g/6f9a4e/32.png) [@gazpacho](https://boards.straightdope.com/u/gazpacho)\ **Post date:** [March 8, 2018, 7:07pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/30 "2018-03-08T19:07:58Z")
> [@FlikTheBlue](#): > > At a speed of one second per second 🙂 You can adjust your speed through time by adjusting your speed through space. The drawback is that it takes a lot of energy to adjust your speed through space enough to make much of a difference in your speed though time and you probably end up somewhere you don’t want to be. ---
**Author:** ![gnoitall](https://avatars.discourse-cdn.com/v4/letter/g/bb73d2/32.png) [@gnoitall](https://boards.straightdope.com/u/gnoitall)\ **Post date:** [March 8, 2018, 8:46pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/31 "2018-03-08T20:46:32Z")
> [@bardos](#): > > We are all time travellers already, we are travelling through time together. That’s very sage. How 'bout this one? > [@The Amazing Criswell](#): > > We are all interested in the future, for that is where you and I are going to spend the rest of our lives. But that’s wrong, because physics says we may spend the rest of our lives someplace besides the future. Like the past, or Gary, Indiana. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 8, 2018, 9:38pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/32 "2018-03-08T21:38:13Z")
> [@gnoitall](#): > > That’s very sage. It’s really more about thyme. ---
**Author:** ![k9bfriender](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/k9bfriender/32/3283_2.png) [@k9bfriender](https://boards.straightdope.com/u/k9bfriender)\ **Post date:** [March 8, 2018, 10:12pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/33 "2018-03-08T22:12:12Z")
> [@Aji\_de\_Gallina](#): > > Also, I’d be supremely bummed if the scientists who actually do time travel to it with a machine called TARDIS. Unless they reveal that they went back to the 60’s and talked to some BBC writers. ---
**Author:** ![MichaelEmouse](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/michaelemouse/32/101_2.png) [@MichaelEmouse](https://boards.straightdope.com/u/MichaelEmouse)\ **Post date:** [March 8, 2018, 10:14pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/34 "2018-03-08T22:14:02Z")
What does it mean for something to be mathematically possible? ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 8, 2018, 10:39pm UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/35 "2018-03-08T22:39:21Z")
> [@MichaelEmouse](#): > > What does it mean for something to be mathematically possible? I believe it means that the pertinent equations can be made to work for those conditions. For instance, we don’t really know what happens inside a black hole, but the inversion of space and time is mathematically possible in the relevant Einstein field equations. ---
**Author:** ![wolfpup](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wolfpup/32/10618_2.png) [@wolfpup](https://boards.straightdope.com/u/wolfpup)\ **Post date:** [March 9, 2018, 1:04am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/36 "2018-03-09T01:04:57Z")
> [@Chronos](#): > > One possible resolution to the “Grandfather Paradox” is that any time you try to set up such a paradox, something happens (possibly with no apparent causal relationship to what you’re doing) that prevents it. Maybe, for instance, you just happen to die of a brain aneurysm just as you’re about to tell your previous self what you wrote. The aneurysm wasn’t exactly caused by your time travel, but timelines where the aneurysm didn’t occur simply don’t exist. I would argue that the causality paradox is much more fundamental than such macroscopic examples, and that in fact the introduction of any matter or energy whatsoever – even a single quantum particle – from the future into the past would, according to chaos theory, necessarily alter the future. Which seems to mean that either time travel into the past is impossible, or one has to invoke “many worlds” – literally the Everettian Many Worlds – and say that any such travel changes the universe whose timeline the traveling entity – whether person or thing – inhabits. You can thus never return to the future from whence you came, but only to an unpredictably different one, because within the Many Worlds multiverse you are no longer in the same universe. By the same token, one would conjecture that if you send an object into the past while remaining in the present yourself, it will arrive in a different universe – not this one, but one whose timeline is consistent with its presence there. Otherwise you would face the paradoxical situation of retroactively changing your present. ---
**Author:** ![Weisshund](https://avatars.discourse-cdn.com/v4/letter/w/ba8739/32.png) [@Weisshund](https://boards.straightdope.com/u/Weisshund)\ **Post date:** [March 9, 2018, 1:18am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/37 "2018-03-09T01:18:54Z")
> [@gazpacho](#): > > You can adjust your speed through time by adjusting your speed through space. The drawback is that it takes a lot of energy to adjust your speed through space enough to make much of a difference in your speed though time and you probably end up somewhere you don’t want to be. I’d think the bigger draw back is you slow your personal flow of time to a crawl but everyone elses continues at normal speed, so no matter where you end up, when you turn around and come back, everyone you wanted to tell about it is dead and gone, and no one that is here cares who you are. ☹ ---
**Author:** ![Asympotically\_fat](https://avatars.discourse-cdn.com/v4/letter/a/e47c2d/32.png) [@Asympotically\_fat](https://boards.straightdope.com/u/Asympotically_fat)\ **Post date:** [March 9, 2018, 3:31am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/38 "2018-03-09T03:31:48Z")
> [@wolfpup](#): > > I would argue that the causality paradox is much more fundamental than such macroscopic examples, and that in fact the introduction of any matter or energy whatsoever – even a single quantum particle – from the future into the past would, according to chaos theory, necessarily alter the future. Without meaning to be overly critical, this argument to me doesn’t really make sense. Chaos theory broadly is about how in certain systems small changes to initial conditions result in much larger changes to later conditions, but an acausal spacetime (i.e. a spacetime with closed causal curves) cannot be described by the development of initial conditions. In other words chaos theory is a redundant concept when “time travel” is involved. ---
**Author:** ![jtur88](https://avatars.discourse-cdn.com/v4/letter/j/e9c0ed/32.png) [@jtur88](https://boards.straightdope.com/u/jtur88)\ **Post date:** [March 9, 2018, 3:50am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/39 "2018-03-09T03:50:10Z")
> [@Cartooniverse](#): > > Indeed, there is no future to visit. I’m not sure you simply take that as a given, and use it to disprove another theory. Certain futures may be inexorable, to a degree of certainty that their denial is untenable. For example, the light from a star, which is now 186,000 miles from my present position, will reach me one second in the future, and the principles of the theory (although I haven’t read them) that in the existing universe governed by the accepted laws, nothing can stop it. Just as certainly as “there is no future”. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [March 9, 2018, 7:42am UTC](https://boards.straightdope.com/t/new-research-shows-that-time-travel-is-mathematically-possible/810228/40 "2018-03-09T07:42:40Z")
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