I'm working from a hypothesis for Star Trek time-travel - one can travel into the past (and influence events there), but one cannot travel into the future. The asterisk to that rule is that if someone else has traveled from the future INTO your past, they can bring you along when they travel back - this has happened in (at least) these five cases:

  1. Q brings Picard forward to a possible future, though only in consciousness and not in physical form in "All Good Things".
  2. Jake bringing Sisko forward in "The Visitor" - what an incredible episode, by the way.
  3. Captain Braxton and several folks in "Future's End" and "Relativity".
  4. Several times in Enterprise with Daniels showing Archer the future.
  5. Admiral Kirk brings Dr. Taylor forward to the 23rd century along with the two whales in Star Trek IV.

So, in ALL the cases where the main characters go forward, there's an intermediary. The out-of-universe reason why they don't generally travel forward is obvious - dramatically, the characters are already in the future, so there's not much punch to going ahead as a regular part of the drama.

But have I overlooked any details here? The time travel chart on Memory Alpha seems to bear this out.

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    That makes sense to me. You can't travel into the future by yourself because your future has not been set yet. You CAN, however, travel with a future entity into their present, since that reality has been established. Commented Dec 15, 2011 at 17:24
  • Do you count returning to the future in ST IV?
    – Kevin
    Commented Dec 15, 2011 at 17:28
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    In the DS9 episode "Visionary", O'Brien traveled 5 hours into the future multiple times due to radiation poisoning, no intermediary involved. Commented Dec 16, 2011 at 4:04
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    In "The Neutral Zone" and "The 37s", groups of cryogenically frozen humans from the 20th century are encountered. Clearly this isn't a real example, but I'm mentioning it to point out the absurdity in the other answers' "can't travel to your future because it hasn't been 'set'" - the future can simply unfold without you until your arrival.
    – Random832
    Commented Dec 16, 2011 at 22:19
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    Um, is everyone forgetting or ignoring Yesterday's Enterprise?
    – Martha
    Commented Jan 17, 2019 at 6:23

6 Answers 6


Voyager 7x11, Shattered

An anomaly set in the present day pushes parts of the ship into the future, where present-day Chakotay was simply able to walk to.


While he had, in a sense, an intermediary, there was Berlinghoff Rasmussen in Star Trek: The Next Generation's episode A Matter of Time. Someone had come back to his time period and left a timeship, but after that, he had the time ship, the traveller was gone, and he was able to travel when he wanted.

There didn't seem to be any limits to his travelling around once he had the time ship.

I would think this might modify your theory a little to include the device as an intermediary, but it's not clear if, once someone has such a device, there are any limits on their travels.

  • +1 The timeship would act as the intermediary being from the future. I don't think Rasmussen would have been able to use it to travel to a future after the timeship was built. Commented Dec 15, 2011 at 17:52
  • Possible, but it doesn't say either way. And, while I prefer to stick with in-universe explanations, it also helps to keep in mind the conditions under which that episode was shot. They had to rush to do the 2 parter "Unification," which included Nimoy and was expensive. That strained the writers (I know, it's why they shut the door on us freelancers) and they needed a simple on-ship episode that was easy to write and film after doing a complex 2-parter AND dealing with the death of Gene Roddenberry. So details were likely not the producers' concern at that point.
    – Tango
    Commented Dec 15, 2011 at 17:59
  • Yeah - clearly in this case the timeship is the intermediary. But since we don't know when precisely it came from, or the details of the fellow's other travels, we don't have any evidence that the intermediary rule is violated. Thinking about it, in EVERY case, the intermediary is really technlogical, except for Q I guess. Commented Dec 15, 2011 at 18:39
  • @Chris: Yes, but I thought it should be included, since, in this case, the intermediary is a machine, not an agent of free will like a person. In other cases, intermediaries USE technology, but aren't. It doesn't break your theory, but it adds a few possibilities to consider.
    – Tango
    Commented Dec 15, 2011 at 18:54
  • Well, if we want to whip up some technobabble, we can say that it's something like a quantum state that changes over time, giving kind of an absolute time-keeping method. I remember something like this in Enterprise, where they manage to quantum date some piece of machinery to the future. We could stipulate that it's tied up with that, somehow... Commented Dec 15, 2011 at 18:59

The obvious and pedantic answer is that every single character on Star Trek has traveled into the future without a future intermediary: the arrow of time normally only goes one way (into the future). Everything—in Star Trek and out (with caveats)—travels forward in time at a rate of one second per second.

The less obvious (although possibly just as pedantic) answer is that you overlooked special relativity1.

Special relativity

Special relativity establishes that there is no absolute reference frame by which to judge events. What that means is that each frame of reference is judged relative to all others, and that there is no one universal timeline by which to judge whether an event counts as forward (or backward) time travel.

Or more formally, there are two postulates of special relativity:

  1. The laws by which the states of physical systems undergo change are not affected, whether these changes of state be referred to the one or the other of two systems of coordinates in uniform translatory motion.

  2. As measured in any inertial frame of reference, light is always propagated in empty space with a definite velocity c that is independent of the state of motion of the emitting body.

Time dilation

One of the consequences of this is that if one frame of reference is moving in relation to another frame of reference, a phenomenon called time dilation occurs. The larger the difference in velocity, the larger this dilation is.

What is time dilation? There's a classic example of a person standing on Earth, watching a rocket fly by. On that rocket, there's another person. Both the person on Earth and the person in the rocket have watches on that are working correctly: one second on the watch is exactly one SI second.

However, if the person on Earth had such crazy vision he could see the watch on the rocket man, he'd notice the rocket man's watch is slower than his, if only by a little bit. Conversely, the rocket man would notice the Earth man's watch has sped up, if only by a little bit.

This is because of both postulates of special relativity at play: the laws of physics are not affected for any one frame of reference (time moves forward in each frame of reference as fast as it always does) and that the speed of light does not change between frames of reference. Because the rocket man is moving faster relative to the Earth man, his frame of reference appears to be slower to the Earth man, and because the Earth man is moving slower relative to the rocket man, his frame of reference appears to be faster.

It's all very confusing, so I'll let Carl Sagan clarify.

Enterprise, time ship

What does this have to do with Star Trek and time travel? Consider being aboard the Enterprise: you're going several hundred times the speed of light. What might be a week-long trip for you (in that you only felt the effects of time, including aging, for a week) would be several years on a more slowly-moving frame of reference (like Earth). For the cost of a cabin on a starship, you'd be able to travel forward in time much faster than the ruffians back on Earth: aging only slightly while Earth's history passes right by.

Plot holes

Now of course, this doesn't happen on Star Trek: there aren't many (if any) plots where the Enterprise arrives back on Earth only to find it's 500 years into the future. And of course, special relativity—and its establishment of universal speed limit—is seemingly ignored with the warp drive.

One popular way to account for this is the Alcubierre drive, wherein the ship stays stationary, but the spacetime around the ship bends and propels the ship faster than the speed of light. Since the ship remains stationary, special relativity isn't violated and time dilation doesn't occur. A ship traveling at warp for one week would experience the same effects as a person remaining on Earth for one week.

Impulse drives

But we're not out of the woods yet: while the warp drive might not be affected by time dilation, there's still the matter of the impulse drive. Impulse drives are "conventional" (as much as that word can be used when talking about Star Trek) drives that propel objects at subluminal speeds.

Since they don't violate special relativity and most definitely increase the velocity of the objects they propel (magnitudes of up to very large fractions of the speed of light), time dilation occurs. So every time the Enterprise falls back to impulse, her crew is traveling into the future faster (relative to other, more stationary frames of reference), if only by a little bit.

Note 1 I am not a physicist, I am a layman. While I believe what follows is mostly accurate, I am most certainly glossing over many of the details and oversimplifying things. Those details should not affect the overall conclusion presented, though.

  • Good points. I did actually have some of these things in mind - what the intermediary provides, whether it's a thinking being or merely an object, is a bridge between these relativistic points of reference. If you ever have some spare brain cells, check this out: theculture.org/rich/sharpblue/archives/000089.html - I think you'd enjoy it. Having said all of this, Star Trek clearly operates from the point of view that, contrary to Special Relativity, there is absolute time and space. A series which more closely reflected the strangeness of reality would be interesting. Commented Dec 15, 2011 at 19:04

Well, the movie Star Trek IV 'The Voyage Home' had the crew of the enterprise perform a slingshot maneuver around a star to travel back into the past to get a pair of humpback whales and then perform the same slingshot maneuver to travel forward into the future.

So, the technique can obviously be used to go back and forward through time... was done without any outside help as far as I know - its' completely a Federation/Starfleet invention. The first time they did it was in TOS series if I'm not mistaken to study the past intentionally.

However, we hadn't seen an episode where 23rd or 24th century Federation crew intentionally went to the future first and then back... probably because of the Temporal prime directive.

Once you go to the future, you change the timeline because you disappeared from your point in time and appeared later on (similar to what happened when Archer was removed from the NX-01 by Daniels and taken to the future at the end of Season 2 of Enterprise).

Of course, that bit is then either forgotten in Season 3 when Daniels shows Archer the fight between the Federation and the Sphere Builders... or, Daniels learned his lesson and didn't allow for passage of time to occur in the past at those times but instead brought Archer back at the same point from which he left (well, the 31st century likely has full blown mastery of time to begin with, so they would find ways to prevent accidents like the one that destroyed the future).

Anyway, to get back to the topic at hand... unless you count the Warp Slingshot around a star maneuver, then you wouldn't find any on-screen examples of Federation crew going forward into the future on their own for say research purposes.

The only other method that I remembered just now is the one used by the Borg Sphere in First Contact. So, the crew of the Enterprise-E was able to reproduce the temporal vortex the Borg created using their own technology to return to their own future - though that's not their own technology (so technically speaking, 'outside intervention' would seem to apply here because they followed the Borg into the past through that method the Borg created first). Still, the Borg's method seems a lot more efficient than the slingshot maneuver.


Captain Braxton in the 29th century, really started setting the stage for Star Trek Time Travel during Voyager. In the final Time Travel Episode, He brought Seven to the future 4 times in an attempt to stop Voyagers destruction which turned out to be his fault all along. Captain Janeway was brought forward twice, the first to receive the mission to stop Braxton in another time period after Seven had done so completing her mission and then secondly to be congratulated.

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    That's not "without an intermediary from the future" at all.
    – Junuxx
    Commented Jan 28, 2013 at 20:47

In Eye of the Needle (VOY S1E07), there is a wormhole with one end in the Delta Quadrant in 2371, and another in the Alpha Quadrant in 2351. This wormhole turns out to be much too small for starships to travel through, but it seems that in theory, wormholes could allow people to travel into their future and back without an intermediary from 'the future'.

  • Arguably the wormhole itself was the intermediary :P since it existed in the future you could propose that it must have originated there, too. Commented Nov 25, 2014 at 14:26
  • @Lightness: All of the examples in the OP are clearly about sapient, intentional intermediaries. A natural phenomenon that anyone can use at a moment of their choosing is not an intermediary in the same sense at all.
    – Junuxx
    Commented Apr 6 at 18:43

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