What is the status of relativity in the Star Trek universe?

[Destructor]

(Apologies if this has already been asked/answered.)

I've just started the Destiny trilogy and I have reached the part where the Columbia reaches Axion by accelerating normally using their impulse engines (their warp drive being broken), which due to time dilation (not a sci-fi concept, a real, measurable phenomena) means that the journey takes 68 days for them and 12 years on Earth.

I'm not unfamiliar with the concept (in fact I just finished a really good Reynolds novel, Pushing Ice, which used the same premise), but it still surprised me to see it showing up in a Star Trek novel, given that (televised in particular) Trek usually avoids any discussion of time dilation and relativity (two concepts that would be almost daily talking points if you really did work on a spaceship). This makes sense, since relativity is actually quite difficult to wrap your head around at the best of times, and also because I think if they did follow relativity, lots of the episodes would become completely unworkable.

So... I used to have the argument about Battlestar Galactica, that eached time they 'jumped', time on Caprica should advance by the amount of time it took light to go from wherever they were to wherever they ended up. Friends would say: "No, because they never 'accelerated', time dilation isn't a factor." I'd argue that it doesn't matter what mechanism you use to outpace light, the moment you have outpaced it, you have effectively time-travelled, and if they had the ability to outpace light they'd also have the ability to send messages backwards through time in order to prevent the original attack. The arguments would always devolve to a point where we'd be discussing the true nature of relativity and we'd get tangled in physics.

The problem with assuming that the warp drive from Trek or the jump drive from BSG somehow 'bypass' relativity is that they assume that there is some kind of 'universal' frame of reference that they are bypassing (in the case of Trek, this seems to be the advancement of time on Earth). But given that this isn't the case, does it have any meaning at all to say that, if I could appear on Alpha Centauri *now* (now being a somewhat more obscure term when dealing with relativity) without having to traverse the intravening distance, physics doesn't have a model for saying when I would actually arrive there.

Or, to put it another way: is time dilation a consequence of the process of accelerating, or a consequence of outpacing light by ANY means? And if the latter, is the depiction of the warp drive consistent with the modern day understanding on physics, assuming that subspace bypasses relativistic effects?

 

[Tiberius]

How do you figure that Galactica could send messages back in time?

 

[Destructor]

Because according to the postulates of special relativity, if you can propogate a message faster-than-light, you can send it to a second location and get a response from that location before you ever sent the message, as illustrated here:

http://www.theculture.org/rich/sharpblue/archives/000089.html

I'd say a Battlestar is a pretty effective message.

 

[F. King Daniel]

As with TV/film Trek, it's nonexistant except for when the plot calls for it. That's Destiny and a brief mention in The Romulan Way. Otherwise, time is 100% constant throughout the universe.

If Trek started taking these things seriously, it wouldn't be the Trek we know and love, full of all the fantastic nonsense we enjoy.

 

[Tiberius]

Because according to the postulates of special relativity, if you can propogate a message faster-than-light, you can send it to a second location and get a response from that location before you ever sent the message, as illustrated here:

http://www.theculture.org/rich/sharpblue/archives/000089.html

I'd say a Battlestar is a pretty effective message.

My take on a Battlestar sending a message would be...

12:00:00 The captain decides to send a message to a distant planet.

12:00:01 The ship jumps, leaving the location that it started from.

12:00:02 The ship arrives at its destination.

Because the ship isn't actually MOVING through space (it just blinks out of one location and reappears at another), it doesn't have any of that weird time-going-slower stuff.

Now, if the ship travelled through normal space fster than light, then yes, time would go backwards and you could send a message back in time. But jumping like a battlestar does wouldn't do that.

 

[Idran]

Because according to the postulates of special relativity, if you can propogate a message faster-than-light, you can send it to a second location and get a response from that location before you ever sent the message, as illustrated here:

http://www.theculture.org/rich/sharpblue/archives/000089.html

I'd say a Battlestar is a pretty effective message.

My take on a Battlestar sending a message would be...

12:00:00 The captain decides to send a message to a distant planet.

12:00:01 The ship jumps, leaving the location that it started from.

12:00:02 The ship arrives at its destination.

Because the ship isn't actually MOVING through space (it just blinks out of one location and reappears at another), it doesn't have any of that weird time-going-slower stuff.

Now, if the ship travelled through normal space fster than light, then yes, time would go backwards and you could send a message back in time. But jumping like a battlestar does wouldn't do that.

It doesn't actually matter; according to relativity, any method whatsoever of going from point a to point b at a rate faster than the speed of light in a vacuum can allow for violations of causality. This is entirely separate from time dilation, and it doesn't rely on how time goes slower as you speed up at all. Instead, it's a function of the fact that when two events are separated by some distance, the order in which those events happen can be different in different frames of reference. That example Tiberius posted is exactly about instantaneous transmission, for example; a message being received the exact instant it's sent.

Essentially, you have this situation: let's say you have two events A and B that happen far enough apart that they can't tell each other what order they happen in by any subluminal or luminal method. And let's say the math works out to allow for this situation.

Reference frame of A - A happens before B
Reference frame of B - B happens before A.

This isn't an illusion of measurement or an effect of light lag in this situation, it's the actual times these events occur at in those reference frames, and it isn't because of time dilation. And it doesn't violate causality because they can't transfer information to one another due to the speed of light limit; you wouldn't actually see it happening because it takes enough time for light to get there that neither side would realize something weird was going on. But let's say your departure is A, and you use any method at all of jumping FTL to where B is occurring, so that you arrive at the moment B happens. Well, once you get there, B's happening. But A - your departure - hasn't happened yet from the reference frame of B.

This is a very, very basic explanation, especially compared to what Tiberius posted, but it's the essentials of how I understand what happens with this; correct me if this is too strong an oversimplification or if I've missed the mark, Tiberius?

So in the end it's what KingDaniel said, yeah; relativity basically only exists in Trek in terms of time dilation and nothing else. I can't even think of any example of Lorentz contractions or changes in mass, either in canon or in TrekLit.

 

[Christopher]

I'm not unfamiliar with the concept (in fact I just finished a really good Reynolds novel, Pushing Ice, which used the same premise), but it still surprised me to see it showing up in a Star Trek novel, given that (televised in particular) Trek usually avoids any discussion of time dilation and relativity (two concepts that would be almost daily talking points if you really did work on a spaceship). This makes sense, since relativity is actually quite difficult to wrap your head around at the best of times, and also because I think if they did follow relativity, lots of the episodes would become completely unworkable.

So... I used to have the argument about Battlestar Galactica, that eached time they 'jumped', time on Caprica should advance by the amount of time it took light to go from wherever they were to wherever they ended up. Friends would say: "No, because they never 'accelerated', time dilation isn't a factor." I'd argue that it doesn't matter what mechanism you use to outpace light, the moment you have outpaced it, you have effectively time-travelled, and if they had the ability to outpace light they'd also have the ability to send messages backwards through time in order to prevent the original attack. The arguments would always devolve to a point where we'd be discussing the true nature of relativity and we'd get tangled in physics.

The problem with your argument is that you're confusing "can" with "must." Yes, in a universe whose laws of physics allow FTL travel, the same laws also allow the possibility of sending messages back in time. But that doesn't mean it always, automatically happens as a result of every FTL travel. It just means that the possibility of one allows for the possibility of the other. You have to arrange the FTL travel/transmissions in a certain way in order to achieve the result of sending a message back in time.

Okay, what you're saying is that if they had FTL travel, they could specifically arrange to send a message back and warn people. But that wouldn't necessarily work. It's easy to postulate a fictional universe that allows both FTL and backward time travel but requires self-consistency, i.e. makes it impossible to "change history" if you do go back. That's easy because it's what the actual laws of physics suggest would be the case. Quantum theory says that if you go back in time, you're entangling the past with the future you came from, making them both (and yourself) part of the same resolved quantum system, which effectively means that you've pre-emptively guaranteed that the future you came from is the one that will happen (or at least that you'd be unable to perceive any alternate futures that might have grown out of that past, because you're entangled with the one you came from and are thus stuck with it). So even if there is time travel in a fictional universe, it doesn't necessarily mean history is mutable. Indeed, if you want to take real physics into account, history shouldn't be treated as mutable.

The problem with assuming that the warp drive from Trek or the jump drive from BSG somehow 'bypass' relativity is that they assume that there is some kind of 'universal' frame of reference that they are bypassing (in the case of Trek, this seems to be the advancement of time on Earth). But given that this isn't the case, does it have any meaning at all to say that, if I could appear on Alpha Centauri *now* (now being a somewhat more obscure term when dealing with relativity) without having to traverse the intravening distance, physics doesn't have a model for saying when I would actually arrive there.

One can postulate a universe in which there is some external reference frame beyond our spacetime that could provide a sort of "absolute" time reference. That's discussed on this site here:

http://aether.lbl.gov/www/classes/p139/speed/space-time.html

In Trek terms, that could be subspace, say.

Or, to put it another way: is time dilation a consequence of the process of accelerating, or a consequence of outpacing light by ANY means? And if the latter, is the depiction of the warp drive consistent with the modern day understanding on physics, assuming that subspace bypasses relativistic effects?

Oh, that one's easy. The thing laypeople tend to overlook is that time dilation is a result of the equations of the Special Theory of Relativity, which is a limited, simplified case dealing strictly with flat space. Warp drive and wormholes grow out of the General Theory of Relativity, which takes gravitation and curved space into account. And yes, it is entirely possible to construct a metric from the equations of General Relativity that allows faster-than-light travel and has no time dilation. Miguel Alcubierre's original "warp drive" metric published in 1994 (pdf here) is just such a case.

Of course, one can construct a situation wherein a space warp undergoes time dilation, but it doesn't happen automatically. For instance, there's the Morris-Thorne-Yurtsever proposal for a wormhole time machine, where you move one mouth of a wormhole at relativistic speeds, thereby time-dilating it so that one mouth ends up effectively in the past of the other. But the time dilation has to be added specifically to the existing wormhole by conventional special-relativistic travel; it isn't an automatic feature, because the wormhole is a creature of General Relativity. (There might be some gravitational time dilation from the wormhole itself, depending on the metric, but that's a weaker effect.)

 

[Destructor]

And yes, it is entirely possible to construct a metric from the equations of General Relativity that allows faster-than-light travel and has no time dilation.

Phew! That's all I really was after.

I guess, in terms of the Battlestar argument, it wasn't that I was expecting them to send messages back to themselves, more than massive amounts of time would pass on Caprica while they were jumping around- something that became evidently untrue when they went back. But I guess the science bods on BSG have a better grasp of the situation than I do.

 

[Christopher]

I guess, in terms of the Battlestar argument, it wasn't that I was expecting them to send messages back to themselves, more than massive amounts of time would pass on Caprica while they were jumping around- something that became evidently untrue when they went back. But I guess the science bods on BSG have a better grasp of the situation than I do.

Yes, that's right. If they're actually travelling faster than light -- or, rather, employing some kind of spacetime warp that allows them to bypass conventional travel through space and reach a destination point faster than light could -- then they're in the realm of General Relativity, not Special, and time dilation isn't a factor. Time dilation applies to objects travelling near the speed of light but still below it. (Or rather, it applies to any relative motion between different observers, but it's only at high velocities that its magnitude becomes significant.)