# Which is more likely in real life - FTL travel or time travel? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [January 28, 2016, 6:10am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470 "2016-01-28T06:10:19Z")\ **Posts on this page:** 17\ **Page:** 2
**Author:** ![Anarcho\_Liberalist](https://avatars.discourse-cdn.com/v4/letter/a/df705f/32.png) [@Anarcho\_Liberalist](https://boards.straightdope.com/u/Anarcho_Liberalist)\ **Post date:** [January 28, 2016, 8:59pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/21 "2016-01-28T20:59:59Z")
> [@Chessic\_Sense](#): > > Can I count travel that appears to be FTL? If I get an exact clone orbiting Alpha Centauri and I’m deleted here, does that count? It should certainly count. It’s the fysical end result that counts. But more importantly: even if we had Star Trek style beaming and replication at our disposal, it would still be an extraordinary challenge to ‘beam’ the information faster than light travels. Or the other way around: sending _just_ information FTL would be an incredible step forward. Voted same thing / possible btw, although I agree that it’s not exactly the same thing, but so very related that if/once any of the two is accomplished in some way, the other is around the corner. ---
**Author:** ![Grrr](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/grrr/32/146_2.png) [@Grrr](https://boards.straightdope.com/u/Grrr)\ **Post date:** [January 28, 2016, 9:30pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/22 "2016-01-28T21:30:19Z")
My understanding is that time travel is possible in theory. However there are limitations. If you build a time travel device in 2016, you can (in theory) travel back in time with the device, but you will never be able to go back further than 2016 (or whenever you built the device). I remember Dr. Michio Kaku talking about this on one of his shows. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [January 28, 2016, 9:45pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/23 "2016-01-28T21:45:14Z")
> [@Chessic\_Sense](#): > > Can I count travel that appears to be FTL? If I get an exact clone orbiting Alpha Centauri and I’m deleted here, does that count? Any transmission of information faster than light is travel faster than light. It doesn’t matter if the FTL travel is done by a spaceship or a single yes/no bit of information. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [January 28, 2016, 10:01pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/24 "2016-01-28T22:01:55Z")
> [@That\_Don\_Guy](#): > > If you’re taking “frames of reference” into account, then FTL travel is already possible. > At some point in time (call it “0 seconds”), something located 3 light-seconds away from you starts traveling directly towards you at 2/3 the speed of light for 3 seconds. At 3 seconds, it reaches the point 1 light-second away from you and stops. > From your frame of reference, at 3 seconds, you see it start to move from the point 3 light-seconds away, and at 4 seconds, you see it reach the point 1 light-second away, so it appears to have traveled 2 light-seconds in 1 second, at a velocity of twice the speed of light. Care to give a real-world example? There aren’t any. Such frames of reference don’t contain anything real. No matter or information can function in that way. The interference fringes inside a microwave waveguide can travel faster than light…but they can’t carry information. They’re not real physical phenomena. You can manipulate two overlapping moire patterns (one on a transparency) and, if you do it just right, the patterns can appear to move much, much faster than you are actually moving the paper. But no actual “thing” is moving, only the relative positions of the patterns. You can’t send a signal that way. So, yes, sure, you can construct abstract frames of reference. It’s just algebra. But they can’t ever be made real. ETA: re-reading your example, I think you fail to apply the proper transforms. The sums of two high sublight speeds can never add up to a superlight speed. 2/3c + 2/3 c is not 1.5 c. ---
**Author:** ![Skald\_the\_Rhymer](https://avatars.discourse-cdn.com/v4/letter/s/ecccb3/32.png) [@Skald\_the\_Rhymer](https://boards.straightdope.com/u/Skald_the_Rhymer)\ **Post date:** [January 28, 2016, 10:15pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/25 "2016-01-28T22:15:30Z")
> [@Anarcho\_Liberalist](#): > > It should certainly count. It’s the fysical end result that counts. But more importantly: even if we had Star Trek style beaming and replication at our disposal, it would still be an extraordinary challenge to ‘beam’ the information faster than light travels. > > Or the other way around: sending _just_ information FTL would be an incredible step forward. > > Voted same thing / possible btw, although I agree that it’s not exactly the same thing, but so very related that if/once any of the two is accomplished in some way, the other is around the corner. Why are you spelling “physical” as you do? That is, why change the ph to f, but leave the y and a alone? ---
**Author:** ![Drunky\_Smurf](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/drunky_smurf/32/449_2.png) [@Drunky\_Smurf](https://boards.straightdope.com/u/Drunky_Smurf)\ **Post date:** [January 28, 2016, 10:21pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/26 "2016-01-28T22:21:27Z")
> [@John\_Mace](#): > > I suspect our puny ape brains have not discovered all there is to know about how the universe works. I’m going with both possible. This. So both are possible and just as likely as each other. > [@Skald\_the\_Rhymer](#): > > Why are you spelling “physical” as you do? That is, why change the ph to f, but leave the y and a alone? So, fisicul? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [January 28, 2016, 10:24pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/27 "2016-01-28T22:24:20Z")
> [@Skald\_the\_Rhymer](#): > > Why are you spelling “physical” as you do? That is, why change the ph to f, but leave the y and a alone? ph is not anarchic, but y and a are very liberal. ---
**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:** [January 28, 2016, 10:35pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/28 "2016-01-28T22:35:25Z")
With my layman understanding of physics, both are impossible. Conceptually, I’d say time travel is more impossible, if that makes any sense. A faster-than-light ship couldn’t negate its own existence in the way that a time machine almost certainly would. ---
**Author:** ![Projammer](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/projammer/32/559_2.png) [@Projammer](https://boards.straightdope.com/u/Projammer)\ **Post date:** [January 28, 2016, 11:09pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/29 "2016-01-28T23:09:03Z")
Many things that we take for granted today were at one time considered impossible because we didn’t have the have enough information to formulate the theories that made the action possible. Talking to someone on the other side of the continent in real time? Impossible because we had no idea that radio waves existed. Or, if you travel back far enough, comprehension that there was even another side of the continent. Ability to ‘see’ the soft tissue structures inside a person in hd without cutting a hole to look? Impossible. Until it wasn’t. It is the height of hubris to imagine that we know enough about the laws of the universe to categorically deny that an action is impossible. ---
**Author:** ![boffking](https://avatars.discourse-cdn.com/v4/letter/b/858c86/32.png) [@boffking](https://boards.straightdope.com/u/boffking)\ **Post date:** [January 28, 2016, 11:15pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/30 "2016-01-28T23:15:03Z")
FTL is already possible under certain circumstances. Ever seen pictures of reactor pools glowing blue? That is called Chernkov radiation. It is caused by radioactive particles moving faster than the speed of light. Of course this only refers to the speed of light through water. ---
**Author:** ![glee](https://avatars.discourse-cdn.com/v4/letter/g/b5a626/32.png) [@glee](https://boards.straightdope.com/u/glee)\ **Post date:** [January 28, 2016, 11:21pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/31 "2016-01-28T23:21:40Z")
> [@Roderick\_Femm](#): > > Or are they essentially the same thing? > > Definitions, if needed: > > FTL travel - the ability to travel from one solar system to another solar system faster than the speed of light can travel the same distance. Doesn’t matter how you do it - warp drive, alternative space, magic, I don’t care, as long as you can do it reliably and repeatedly. > > Time travel - the ability to move in time in a manner analogous to the way we already move in space, backwards, forwards, whatever. Perhaps like H G Wells device, or more like Dr. Who. There may be restrictions (there may be Time Lords, for that matter) but basically you can go whenever you want. > > Poll to follow. I thought we could already travel in time - but only forwards. You get on a rocket, travel fast for some distance, turn around and travel fast back. When you arrive, you have aged less than the planet you live on. Is that correct? Does it count? ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [January 29, 2016, 2:57pm UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/32 "2016-01-29T14:57:57Z")
I feel like FTL may be theoretically possible. Like if you could someone figure out a way to warp space (which we know gravity does…or is…or whatever) it seems conceptually possible. Time travel feels more like an odd mathematical artifact from some physics equations. I can’t really grasp my mind around the concept of 1842 or any (every?) other period in time actually existing somewhere simultaneously in such a manner that one could travel there AND what happening on those time periods effecting other events in other periods… ---
**Author:** ![glowacks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/glowacks/32/5548_2.png) [@glowacks](https://boards.straightdope.com/u/glowacks)\ **Post date:** [January 30, 2016, 2:40am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/33 "2016-01-30T02:40:20Z")
I assume by “time travel” you mean “time travel into the past”. Time travel into the future happens constantly, and we have measured it happening with atomic clocks. The past-direction is much harder and has no theoretic mean of occurring as far as I know. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [January 30, 2016, 2:45am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/34 "2016-01-30T02:45:58Z")
FTL travel. Aren’t there multiple ways this could be possible? Wormholes, expanding/contracting space-time around the ship, entering higher dimensional space, etc. ---
**Author:** ![drewder](https://avatars.discourse-cdn.com/v4/letter/d/57b2e6/32.png) [@drewder](https://boards.straightdope.com/u/drewder)\ **Post date:** [January 30, 2016, 2:46am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/35 "2016-01-30T02:46:21Z")
> [@msmith537](#): > > I feel like FTL may be theoretically possible. Like if you could someone figure out a way to warp space (which we know gravity does…or is…or whatever) it seems conceptually possible. If a race is a mile but I find a way to warp space so that I can finish in one step I haven’t changed the speed at which I travel but rather the distance required. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [January 30, 2016, 4:08am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/36 "2016-01-30T04:08:19Z")
> [@drewder](#): > > If a race is a mile but I find a way to warp space so that I can finish in one step I haven’t changed the speed at which I travel but rather the distance required. Well, yeah, that’s sort of the point. But if it gets you from Point A to Point B a mile away instantaneously, for all intents and purposes that’s how fast you’re moving. > [@glowacks](#): > > I assume by “time travel” you mean “time travel into the past”. Time travel into the future happens constantly, and we have measured it happening with atomic clocks. The past-direction is much harder and has no theoretic mean of occurring as far as I know. No, but FTL travel introduces a whole bunch of causality problems IIRC. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [January 30, 2016, 5:36am UTC](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470/37 "2016-01-30T05:36:22Z")
> [@msmith537](#): > > Well, yeah, that’s sort of the point. But if it gets you from Point A to Point B a mile away instantaneously, for all intents and purposes that’s how fast you’re moving. . . . > > FTL travel introduces a whole bunch of causality problems IIRC. Yep. If you can get from point A to point B faster than it would take light to go between the two points, then there is some not-as-fast-as-light but-really-really-fast frame of reference where you will be perceived as being at point B first and point A second. Any method, including wormholes, warping space, or teleportation can lead to causality reversal. But… Question: is this true of the “expansionary phase” of the early universe, right after the Big Bang? Space itself expanded faster than light. If someone had been on hand, and able to move at really high speeds, could he have sent a message back in time? (The whole fraction of a picosecond that there was of it…) [Previous page](https://boards.straightdope.com/t/which-is-more-likely-in-real-life-ftl-travel-or-time-travel/744470.md?page=1)