In this setting, humanity has advanced to the technological capability of extra stellar travel via faster-than-light drives. However, due to distances between inhabited areas being extremely large, travel between two systems is still very, very slow and resource intensive, taking years at a time (As light is known to do already).

As a result, technology was developed to effectively "tunnel" through space-time as a wormhole theoretically does in order to facilitate travel, and this effectively allows four-dimensional travel. What if the wormhole functioned on an entirely vector-based system, where the entry point and exit points must take into account spatial distance? For instance, if a traveler from Earth entered the wormhole and only traveled time (not space), he would end up in the exact same space as he left, just at a different point in time, meaning that the Earth would not be at the wormhole exit, it would not have arrived yet.

I could see that there would be a huge drive to map true planetary motion, complete with the development of a system to map locations in four dimensions, perhaps continuing on into the past so far as to map objects back to the big bang and expansion of space-time, a true final frontier.

Let's assume that creating wormholes is extremely energy intensive, and construction of a tunnel requires enormous feats of engineering and resources to the point where only one tunneling device exists for the time being and the actual opening is 25 m3 that travels with the space-time velocity of the device (meaning that the device must compensate for its own travel if it needs to exist in a specific point in space).

What potential for abuse does this system have? What methods might a government take to keep order? How might scientists attempt to study paradoxical behavior (If it even exists)? What other applications might this technology have (especially for historians and explorer types)? What might a universal reference point be for the device that is not mechanically determined?

  • $\begingroup$ What's the question? Do you mean "What would happen?" $\endgroup$
    – HDE 226868
    Oct 11, 2014 at 18:20
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    $\begingroup$ A phrase like "exact same space as he left" supposes absolute spatial references, which are not supported by known physics. If the wormhole's exit is tethered to the earth, the traveller would appear there. As the wormhole technology is imaginary, you are free to make up what it is tethered to, and therefore where any traveller would end up. $\endgroup$ Oct 11, 2014 at 18:41
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    $\begingroup$ @Zer0ah The Big Bang did not happen at a point. $\endgroup$
    – HDE 226868
    Oct 11, 2014 at 18:47
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    $\begingroup$ Ah I see, I shall have to do some more research I see, but for mean time let's say that there is a single given point in the universe that the device references (I shall add a question of what this point may be) $\endgroup$
    – Zer0ah
    Oct 11, 2014 at 18:52
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    $\begingroup$ When travelling back to 100,000 BC you need to consider both time and the relative dimension in space. $\endgroup$ Mar 8, 2015 at 22:37

3 Answers 3


Let me state for the record that all time travel ends with paradoxes - this is inevitable. There is no known way to model time travel without paradoxes (that includes the parallel universe approach). With causality in place, time travel irrevocably will present a paradox if you dig deep enough. Since this is fiction of course, we just need to make it plausible enough so the problems don't matter enough.

The Time Bomb

The simplest form of abuse is someone using this to transport an explosive device (or something who's target position will have destructive consequences) back in time, to an arbitrary location - and a time when there's no defense for the weapon.

The Grandmother Bomb

Depending on how you model your time travel rules, someone could go back and prevent the device from being made. Someone could arrive from the future (or infinite numbers of people could) to prevent it from being used. If you have time travel, anyone can have it in the future - and it lasts long enough for lots of people to come back to your time.

Too much power

Whatever the way the device works, it is obviously capable of manipulating matter at a basic level - if something goes wrong, it could just make the target space-time location explode. There's always the problem of replacing whatever is in the spot you want to put your stuff in: if you travel back in time, what if someone is in that place? What about just the air that's there? Do you replace it or push it away? I can imagine that forcing matter (or energy) to coexist forcibly with other matter, it could become accelerated to large fractions of c and just annihilate the entire place.


If someone had such a device, it's pretty obvious that they'd want to regulate use as much as possible. To the point where they might avoid even using it themselves unless absolutely necessary. Since in your premise this is used for transportation, it will be accessible to average people.

One way of preventing the above abuses would be to intentionally engineer the device to only work with an artificial endpoint (thus, it can only send people to a specific place at a nearby time and that place has to be explicitly created for use with this device), to only be able to transport within small time distances (aka, it can transport someone from here to another planet, but when they appear, it's at most a few seconds after you start the transport) and make sure it has a time lock (like banks) and requires explicit monitoring and manual authorization for all transports.

In essence, besides having to be controlled by some kind of incorruptible authority powerful enough to prevent abuse, it would have to be engineered to prevent abuse, even if reverse engineered. It would have to be made confusing, without anyone knowing the way it works entirely and possibly break or distort itself upon any attempt at disassembly. The stakes are too high.

Of course, it can be built for a purpose and then destroyed after it is fulfilled.

Paradoxical behavior

As stated in the beginning, paradoxes are inevitable. It's easy to come up with thought experiments that end in paradoxes - it's tough to come up with ones you can test without catastrophic consequences.

I'd say that, besides testing with tiny amounts of matter and energy to evaluate causality paradoxes (using only annihilations, collisions, transmutations and conservation laws) they would have to attempt all of this within very small time frames (in the order of milliseconds at most). Unless they mess up, they should be able to figure out at least the broad rules of how causality is affected and how far-reaching the effects can be, by extrapolating from stochastic processes. They might even be capable of evaluating the validity of deterministic physical laws.

Other applications

I can't think of many - time travel is manipulating time to your advantage. You might be able to speed things up (computers that send information backwards in time to themselves have been thought of in fiction) or slow things down (like stasis in star trek). You could perhaps experiment with processes that take millions of years to complete (send something back in time, in a container and attempt to meet it in your own time - provided your device isn't locked as I proposed).

Reference frames

The only way to really achieve this would be to pick something that isn't expected to change unpredictably within the amount of time you want to travel. This can be a signature the device can detect in space-time, rather than just space (perhaps the latter would be useless anyway). Since objects don't carry a tag in the universe, it would have to detect and measure its influence on its surroundings. This means it would have to be able to predict future behaviors accurately - if it's a star for instance, it would have to include very accurate stellar and orbital mechanics predictions to make sure it can maintain the reference.

It could perhaps maintain a set of references - multiple points that it uses to produce coordinates in space-time. This would be much like how spacecraft and aviation computers are built in threes - all perform the same job and check each other for errors - if two agree, an operation is correct, if all disagree, there's an error. A reference matrix, made of multiple points, would be much more robust and would allow for some errors in the predictions.

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    $\begingroup$ "Let me state for the record that all time travel ends with paradoxes" -- I disagree. If time travel meant moving to a parallel universe where time moves slightly faster or slower, you could seemingly move into a parallel universe like ours only 30 years earlier. However, you could not alter your parallel universe, but only the current. Even if you moved back into your own, it would be exactly as you had left it. $\endgroup$
    – Neil
    Jan 20, 2015 at 10:12
  • $\begingroup$ @Neil: Parallel universes can completely avoid paradoxes, though they end up with another problem: chaotic systems play a sufficient role in almost everything that while parallel universes could exist, it's exceptionally improbable that they'd bear any resemblance to the present one. If a small change in one universe caused a man to arrive home from work an extra half-second later on the evening when he would conceive his child, such a change could very easily affect which sperm fertilized the ova, and thus causing the child to be completely different. $\endgroup$
    – supercat
    Feb 21, 2015 at 20:10
  • $\begingroup$ @Neil: If in a parallel universe, even the tiniest thing had been different in e.g. Plymouth Colony, that would have likely caused noticeable consequences in Virginia around the time Thomas Jefferson was conceived, and had Thomas Jefferson not been who he was, it's unlikely the United States would have emerged in anything like its current form. $\endgroup$
    – supercat
    Feb 21, 2015 at 20:15
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    $\begingroup$ Just means you need a LOT of parallel universes and enough patience to find the one you need. $\endgroup$
    – Erik
    Apr 20, 2015 at 13:17
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    $\begingroup$ Uhh, just no. The results of attempting time-travel in GR has been solved mathematically. Should someone try to create a paradox by removing the cause for an effect, the result will inevitably be a self-caused event that prevents the paradox from being reached. GR is not pre-determined in this scenario. There is no way to predict which self-caused event will become real. $\endgroup$
    – Joshua
    Mar 6, 2019 at 17:25

As Neil pointed out, there is no absolute frame of reference, so I'll pretend that the frame of reference is relative to something - in some scenarios, the Sun; in others, the Earth, and in others, the center of the Milky Way.

What potential for abuse does this situation have?

Well, there's always the old 'execution-by-pushing-a-person-into-outer-space-so-s/he-dies-from-suffocation-and-heating/freezing' approach. You simply calculate at what point in time there will not be an Earth in that position, and push the person in.

For those who are horrified at the idea, I'll say that this system has the potential for some great advances in bringing things from one place to another. Say you have a lot of toxic waste, or spent nuclear fuel. Simply calculate the time at which that point in space will be filled by, say, a star, and push all the unwanted material in. Foom! - all the waste is gone. Quite the handy-dandy kitchen appliance.

In all seriousness, though, the effects of this system depend on how many people have access to it. If anyone in power thinks of the execution method I described above, they would instantly make a push for strict regulation of the devices. We'll confine that to Area 51, thank you very much. Honestly, government regulation depends on just who came up with the idea. If it's a relatively secret (i.e. classified DoD or MI5) government project, its very existence will be most likely hushed up. If it's a defense contractor, or a private company, word could spread. And if some guy/girl came up with it in his/her backyard, we're in trouble.

On to paradoxes. There are plenty: the grandfather paradox, the killing-the-inventor paradox, and the becoming-your-own-mother-or-father paradox. These are all fairly big problems in science, as they throw causality out the window. The only hope is that traveling in time fulfills what has already (or what will already) happen. The other hope is that of the multiverse (where each universe splits upon each decision, and if you kill your grandfather this all happens in another universe), but that's highly, highly speculative. So scientists would love to study the paradoxes.

Other applications. Hmm. Tricky. Well, not really, but hard to narrow it down. You could travel in time to test theories, take tours of famous places and meet famous people, and really do anything you want. However, there is a limit to what you could do. If the reference point is the Sun, you could only travel back in time in multiples of one year. Of course, all you'd have to do to travel to another point in time is to go back a bit further and wait it out, but that's a bit boring. Unless you're sipping pina coladas with Julius Caesar.


Perhaps if you could model things realllly well, then maybe time travel COULD include spatial travel.

If I travel back in time 100 years, but nowhere spatially, I most certainly won't end up in the same place. The Earth, Solar System, Galaxy have traveled fast and far.

If you had the technology to send yourself forward or backward in time "without changing space" with utmost precision, you could time it so that you land on something that has shifted over time, in the universe. You can't be too picky about where you want to go spatially. That way, YOU aren't moving spatially, but objects in the universe are rushing to meet up with you.


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