# Re: Is Time Travel Possible? **URL:** \ **Category:** Cecil's Columns/Staff Reports\ **Created:** [August 2, 2014, 6:29am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627 "2014-08-02T06:29:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![The\_Great\_Unwashed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_great_unwashed/32/4791_2.png) [@The\_Great\_Unwashed](https://boards.straightdope.com/u/The_Great_Unwashed)\ **Post date:** [August 5, 2014, 5:38pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/21 "2014-08-05T17:38:29Z")
> [@Chronos](#): > > **RaffArundal** ’s post claimed to be objecting to time travel on grounds of conservation, but it’s not really an objection to time travel, but an objection to teleportation. There’s no reason why time travel would need to involve teleportation, in which case that objection doesn’t apply. You understand that if I popped out existence now to reappear at some time later, say September, that the universe during August would be short of my mass (etc.)? It is that (albeit temporary) shortfall that appears (to me) to violate conservation of matter. ---
**Author:** ![John\_W.Kennedy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_w.kennedy/32/1031_2.png) [@John\_W.Kennedy](https://boards.straightdope.com/u/John_W.Kennedy)\ **Post date:** [August 5, 2014, 7:02pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/22 "2014-08-05T19:02:15Z")
The big problem with time travel via Special-Relativity time dilation is that the square root in the equation makes t’ imaginary, not negative. ---
**Author:** ![RaffArundel](https://avatars.discourse-cdn.com/v4/letter/r/87869e/32.png) [@RaffArundel](https://boards.straightdope.com/u/RaffArundel)\ **Post date:** [August 5, 2014, 7:25pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/23 "2014-08-05T19:25:18Z")
Technically, I was objecting to the particular idea that you could pop in and out of space-time without breaking some laws. Or rather what my evil twin RaffArundal was thinking… I asked about laws being violated by the “skipping ahead” (or back) referred to by Czarcasm. So that is \*specifically \*talking about “time teleportation”. Lumpy covered time-dilation, which would be skimming forward not skipping and I have no issue with. I am in fact narrowing down our options based on what we know. Still now that you press it, I’m not sure how your comment jives when travelling backwards in time. Doesn’t it make it worse, not better? Assuming you “walked”, during that time you (mass/energy) are tripled - the original stuff, the backwards traveling stuff, and the stuff that resumes travelling forward. How does that not violate conservation laws? I’m still interested in the entropy question, since AFAIK increasing entropy (in a closed system) and time are related. But I will leave that for another day - I’m clearly not getting my questions for discussion across properly. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [August 5, 2014, 8:54pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/24 "2014-08-05T20:54:35Z")
> [@Frodo](#): > > Yes you can! I Was wrong. > [@Frodo](#): > > No, definitively not possible. Why am I seeing posts from two distinct parallel universes in one thread? Didn’t someone say that was impossible? ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [August 5, 2014, 9:00pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/25 "2014-08-05T21:00:06Z")
> [@sbunny8](#): > > The fact remains that no one has yet observed an example of cause and effect where the effect preceded the cause, but this doesn’t necessarily mean that such a thing can’t happen. Aren’t there some bizarre cause-and-effect mix-ups that theoretically can happen at the quantum particle level? And have any actually been demonstrated? I’m thinking of weird quantum stuff like [Delayed choice quantum eraser](http://en.wikipedia.org/wiki/Delayed_choice_quantum_eraser) experiments and other such bizarro stuff I’ve read about from time to time. But it all seems ungrokkable to me. ---
**Author:** ![Czarcasm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/czarcasm/32/4050_2.png) [@Czarcasm](https://boards.straightdope.com/u/Czarcasm)\ **Post date:** [August 5, 2014, 9:00pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/26 "2014-08-05T21:00:08Z")
> [@Senegoid](#): > > Why am I seeing posts from two distinct parallel universes in one thread? Didn’t someone say that was impossible? Yes…and no. ---
**Author:** ![watchwolf49](https://avatars.discourse-cdn.com/v4/letter/w/e9c0ed/32.png) [@watchwolf49](https://boards.straightdope.com/u/watchwolf49)\ **Post date:** [August 5, 2014, 9:28pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/27 "2014-08-05T21:28:16Z")
“If time travel were possible, where are the tourists” ---
**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:** [August 5, 2014, 10:34pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/28 "2014-08-05T22:34:14Z")
> [@](#): > > Quoth **The Great Unwashed** : > > You understand that if I popped out existence now to reappear at some time later, say September, that the universe during August would be short of my mass (etc.)? It is that (albeit temporary) shortfall that appears (to me) to violate conservation of matter. So don’t pop out of existence. Instead fly off in a spaceship on a perfectly ordinary trajectory, where your mass enters and subsequently leaves different locations in a perfectly ordinary way, in such a way that you come back after a year has passed for you but a century has passed for us. That’s certainly possible. It may even be possible (though signs point to “no”) to pull a similar trick, with a perfectly ordinary trajectory, but to arrive at a time earlier than when you left. Neither one is teleportation, but arguably the first and certainly the second would be time travel. ---
**Author:** ![The\_Great\_Unwashed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/the_great_unwashed/32/4791_2.png) [@The\_Great\_Unwashed](https://boards.straightdope.com/u/The_Great_Unwashed)\ **Post date:** [August 5, 2014, 11:11pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/29 "2014-08-05T23:11:19Z")
> [@Chronos](#): > > So don’t pop out of existence. Instead fly off in a spaceship on a perfectly ordinary trajectory, where your mass enters and subsequently leaves different locations in a perfectly ordinary way, in such a way that you come back after a year has passed for you but a century has passed for us. That’s certainly possible. It may even be possible (though signs point to “no”) to pull a similar trick, with a perfectly ordinary trajectory, but to arrive at a time earlier than when you left. Neither one is teleportation, but arguably the first and certainly the second would be time travel. Genuinely you have snapped me out of a revery, of course you are right (at least about travelling forward in time, that much has been repeatedly demonstrated experimentally). But still there seems to me to be some inconsistency with our conservation laws, could it be that they are wrong (or more prosaically that I have misunderstood them)? ---
**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:** [August 6, 2014, 1:46am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/30 "2014-08-06T01:46:45Z")
There’s a good chance that you’re misunderstanding them, since that very commonly happens. In particular, conservation laws are strictly local, not global: That is to say, if you draw a box somewhere, then Conservation of Energy states that the change in the amount of energy in the box is equal to the amount of energy that flows through the walls of the box. If something just poofs away, that violates the conservation law, since the content changed without anything going through the walls. If something flies out of the box, it doesn’t: The energy content of the box changes, but it’s from something passing through the walls. But local conservation does _not_ imply global conservation. It’s possible to have a universe where this law is true for every box you care to draw within the universe, but the total energy content of the universe as a whole nonetheless changes. In fact, it’s not hard to arrange this, and the Universe in which we live appears to be an example. ---
**Author:** ![Powers](https://avatars.discourse-cdn.com/v4/letter/p/edb3f5/32.png) [@Powers](https://boards.straightdope.com/u/Powers)\ **Post date:** [August 6, 2014, 2:07pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/31 "2014-08-06T14:07:18Z")
You also have to consider that the Conservation Laws may not completely describe our universe due to limited information. Saying that time travel is impossible because it violates the Conservation Laws is like saying Relativity is wrong because it violates Newton’s Laws. Powers &8^] ---
**Author:** ![salinqmind](https://avatars.discourse-cdn.com/v4/letter/s/3ec8ea/32.png) [@salinqmind](https://boards.straightdope.com/u/salinqmind)\ **Post date:** [August 6, 2014, 2:54pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/32 "2014-08-06T14:54:34Z")
I dimly remember reading of a scientific experiment performed some years ago, cannot remember any details, but I think it involved clocks. (atomic energy maybe?) The results were, the experimented on clock moved ahead, or moved back, by a tiny amount. This did not prove any time travel was feasible, but that tiny amount did prove it could be possible. Does anyone know what I’m talking about? I don’t! but I remember it involved clocks. ---
**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:** [August 6, 2014, 3:44pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/33 "2014-08-06T15:44:51Z")
Atomic clocks (which don’t have anything to do with atomic energy; they’re just really accurate clocks), one of which is in orbit and one of which is on the ground. They prove that gravitational time dilation exists, but that doesn’t have any bearing at all on the possibility of go-back-and-kill-your-grandfather time travel. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 6, 2014, 4:12pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/34 "2014-08-06T16:12:53Z")
> [@John\_W.Kennedy](#): > > The big problem with time travel via Special-Relativity time dilation is that the square root in the equation makes t’ imaginary, not negative. Strictly speaking, that would be going _sideways_ in time! Alternate histories maybe? ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [August 6, 2014, 6:51pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/35 "2014-08-06T18:51:32Z")
I’m posting this two weeks from now to tell you that time travel is definitely impossible, and you shouldn’t even try. Trust me. ---
**Author:** ![AHunter3](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ahunter3/32/368_2.png) [@AHunter3](https://boards.straightdope.com/u/AHunter3)\ **Post date:** [August 6, 2014, 10:59pm UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/36 "2014-08-06T22:59:20Z")
I think it’s a meaningless proposition (despite all the nice science fiction). Imagine a three dimensional cube with coordinates on the x, the y, and the z axis. Would you ask whether it is possible for the coordinate 1, 14, 29 to exist at 37, 14, 77? Time is not something you “travel through”; the person that you are exists in four dimensions and is bounded in each of those dimensions. You could hypothetically occupy some other locations instead, but you do, in fact, occupy the ones you occupy, that’s where you’re at. Heck, I’m not a determinist and this board is chock-full of determinists. ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [August 7, 2014, 12:41am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/37 "2014-08-07T00:41:58Z")
Hey, I got a nitpick about **Cecil** ’s column too: > [@Cecil](#): > > So don’t start making plans to visit the Pleistocene epoch just yet. Uh, isn’t the Pleistocene Epoch the epoch we are _currently_ living in? I hope so, as I visit there quote often. It’s a nice enough epoch, mostly. As **Cecil** himself notes, it’s only the last (20th) century that one may wish to avoid. (I know, I know. We’re currently in the Holocene Epoch. If that’s a real epoch unto itself, that is. The Holocene may be its own epoch, or it may just be the current phase of the Pleistocene – I’ve seen it described both ways in various sources.) ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [August 7, 2014, 1:00am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/38 "2014-08-07T01:00:31Z")
> [@Senegoid](#): > > Hey, I got a nitpick about **Cecil** ’s column too: > Uh, isn’t the Pleistocene Epoch the epoch we are _currently_ living in? I hope so, as I visit there quote often. It’s a nice enough epoch, mostly. As **Cecil** himself notes, it’s only the last (20th) century that one may wish to avoid. > > (I know, I know. We’re currently in the Holocene Epoch. If that’s a real epoch unto itself, that is. The Holocene may be its own epoch, or it may just be the current phase of the Pleistocene – I’ve seen it described both ways in various sources.) Given that the Holocene has seen the extinction of much animal life, the Earth’s surface has been altered to the point where it will show in the future geologic record, and enough CO2 has entered the atmosphere that the cycle of ice ages has probably been cut off, it’s looking like a new epoch more and more. ---
**Author:** ![qazwart](https://avatars.discourse-cdn.com/v4/letter/q/5fc32e/32.png) [@qazwart](https://boards.straightdope.com/u/qazwart)\ **Post date:** [August 7, 2014, 1:54am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/39 "2014-08-07T01:54:18Z")
Oh I know time travel is possible. Just last week, it was 1980. I was young, thin, and full of vigor. The next thing I know it’s 2014 and there are three kids who insist I’m suppose to pay for their college education. Now if I can only find the evil entity who stole my youthful body and placed my esence in this bloated old thing. But, first I’ve got to get some young punks off my lawn. ---
**Author:** ![barneydez](https://avatars.discourse-cdn.com/v4/letter/b/57b2e6/32.png) [@barneydez](https://boards.straightdope.com/u/barneydez)\ **Post date:** [August 7, 2014, 6:41am UTC](https://boards.straightdope.com/t/re-is-time-travel-possible/694627/40 "2014-08-07T06:41:19Z")
Will someone please let me know honestly if I should spend my _time_ reading this post? I actually did stop reading a few sentences after I saw the word theory used in its context in Ceasel’s original post. It’s theory or fact but be aware of what you asking for if you read further, you may not like the answer. It solves the GOD answer as well. There is no way possible that time travel is possible, by both measures, if with a God or without, but it may affect your belief in God. 1. It can only be one or the other. If there is a God, there is no, and I mean 100% no chance he can 31st in time. Truly if God existed in time, at any measure, is to say the god has a beginning and and and and thus isn’t a God at all. A God may enter or exist time when they so chose, but cannot exist in time by any measure or must be subject to end. Period. Therefore, a God must exist above a time line, such as looking at a ruler on the space station in midair. Either shape, the time line must be observed by a true God. The question alone is silly since anyone in any time on that ruler is subject to the ruler itself, that is, they must recognize they exist and that they are on the ruler we’ll call timeliness itself. But to navigate anywhere on that ruler, no matter what shape it may be in, cannot be navigated as it would force you to be elevated at a level only God can have the pleasure of enjoying the ability to exist as a God to begin with, and to say we can navigate to a level of a God and that by definition would prevent it from being a true God but rather just a god. So, time travel must be impossible, with or without a God, because… 2. If there is no god, then all laws subject to any law by definition should be able to go back to theory since mere probability would indicate our entire “known” universe can be chalked up to theories, including quantum mechanics, WITH THEORY EXCEPTION OF MOTION! Since even if your an atheist you have to admit there is a law in motion because even if your time line wasn’t in motion it would have to have the same probability of randomness as all exist of anything anywhere must; therefore, it would mean that the time limit email ruler itself was subject to there having a probability, as slight as it may be, that it would be able to protect itself from non existence and thus subject to any god or God. IDK, that’s just my opinion and if anyone has touched on that in a prior post, I will read every post as all would force me to think. Thanks and after plenty of pleasure reading other threads, this is the first time I have ever joined because I honestly would like my first question answered before I proceed. Thank you for taking the time to read all of mine if you did. I never prepare. I only type as I think and hope auto spell doesn’t mess up. Barney [Previous page](https://boards.straightdope.com/t/re-is-time-travel-possible/694627.md?page=1) [Next page](https://boards.straightdope.com/t/re-is-time-travel-possible/694627.md?page=3)