Why strip Voyager of its borg and alien tech enhancements?

[Idran]

In what way doesn't warp drive make sense, scientifically? It's a completely made-up technology.

Special relativity, causality, and FTL: you can only pick two, all three are mutually contradictory. It's not a tech barrier, it's a physics barrier; you can't tech your way out of literally any usage of FTL resulting in time travel under special relativity as it is in our universe, because the order of events is only preserved for space-like separated events. (That is, for two events that are far enough apart in space and time that light couldn't pass from one to the other, the order in which they happen depends on your frame of reference. Not just the order in which they appear to happen, it's not a travel-time-of-light issue, but the order in which they actually happen.)

There's more information on it here, and a good illustration of it in the Ladder paradox here. But for a quick illustration of the ladder paradox, consider this: you have a barn with a door on either side, and a rod that's too long to fit inside the barn. The rod moves towards the barn fast enough that its length is shortened in your frame of reference small enough to fit within the barn, and you have a timer set up to close both barn doors at precisely the same time when the rod is within and open them again before the rod reaches the far side. What happens from the rod's frame of reference? From its frame of reference, it's too long to fit within the barn, and in fact the barn itself would be length contracted as well to be even smaller, so how can both doors close at precisely the same time from the frame of reference of the rod?

The resolution to the paradox according to special relativity if you run through the math is that in the rod's frame of reference, they don't close at precisely the same time; the actual time of the events of the two door closures are different from the perspective of the rod, purely because the rod is moving really fast. The door ahead of it closes and opens when the front of the rod enters the barn, and the door behind it closes and opens when the back of the rod enters the barn. And there exists yet another frame of reference in which the door behind the rod closes and opens before the door ahead of the rod; again, a frame of reference in which it actually does, not just one in which it appears to because of the travel time of light.

Because of stuff like this, literally any FTL drive would be violating causality for some pair of events every time it was used; you literally couldn't use it without having something happen "out of order".

Space and time are much weirder under relativity than even things like time dilation and Lorentz contraction suggest, and it's far more complicated than just the speed of light being a barrier. There are a ton of other variations on the ladder paradox in that Wikipedia article, there's a lot of alternate formulations that are also really weird from our usual perception of space and time; it's definitely worth a read.

 

[Christopher]

In what way doesn't warp drive make sense, scientifically? It's a completely made-up technology.

Special relativity, causality, and FTL: you can only pick two, all three are mutually contradictory.

Except that warp drive is grounded in the equations of General Relativity, which apply to a broader range of situations than Special Relativity (as the names indicate). Special Relativity applies solely to unaccelerated motion, as a simplification that made the math easier. General Relativity covers accelerated motion and establishes how gravitation can be characterized as a topological distortion (or warp) of spacetime. Einstein himself recognized that sufficiently extreme spacetime distortions could hypothetically produce shortcuts allowing effectively superluminal travel. That's why wormholes are more formerly called Einstein-Rosen bridges -- because those two worked out the math for them in the first place. The very concept of warp drive in science fiction was based on the General-Relativistic notion of spacetime distortion allowing effective superluminal travel. The warp drive equations that Miguel Alcubierre worked out in the 1990s are a solution of the GR equations, and though nobody had worked out that precise math before, the basic concept had been understood as an implication of GR since at least 1930 (when John W. Campbell wrote the first work of fiction that referred to an FTL drive "warping" space).

Granted, there are practical limitations that make it very unlikely for warp drive to work in practice, but it's not as great a stretch of physical law as people assume. It's just that most people don't realize that Special Relativity is only meant to be part of the picture. It's not meant to apply to situations where acceleration or spacetime distortion occurs. It just doesn't have the equations to cover those.

 

[Idran]

No, there are examples of the ladder paradox that also apply to non-interial motion; the man-falling-into-a-grate paradox, for example. Einstein-Rosen bridges and Alcubierre drives and all that still result in causality violations if used in practice, because the problem of simultaneity still exists in GR as much as it does in SR. Even if you found a way to develop FTL in real life, any such drive would still inevitably imply violations of causality when used.

Note that I never said FTL was impossible, just that FTL, relativity, and causality can't all be simultaneously held as true at once.

 

[Christopher]

Well, the way I'm coming at it is, I constantly hear people making the assumption that warp drive and other forms of FTL require "violating Einstein" or "proving Einstein wrong," when the fact is that pretty much every hypothetical FTL drive that exists in fiction (except for things like quantum jump drives or Infinite Improbability Drives) is based in Einstein's theories to begin with, just different ones from the well-known Special Relativity rules that most people think are the only thing Einstein ever did. The whole reason "warp drive" is called that is based in Einstein's own concept of gravity as a spacetime distortion or warp. It doesn't violate or contradict Einstein -- Einstein was the guy who came up with the underlying framework of it. Yes, there are issues of causality and energy and so forth that make it unlikely they could be achieved in practice, but that's okay when you're dealing with fiction, and the basic theory of it is entirely Einsteinian. So it's not just pure fantasy as some fans assume.

 

[Idran]

No, I know; the reason why I said it was unscientific is because warp drive in Trek doesn't violate causality, not because it's fundamentally impossible to have FTL and relativity at the same time. (Though interestingly, the "pick two" principle is only true under the specific manifestation of relativity that our universe happens to use.)

But this is a ton more detail than my silly joke that kicked this all off probably deserves, honestly. (The only reason I even went into that big effort post in reply is because the ladder paradox and its kin and the simultaneity issue are really cool, and I'll take any excuse to explain them. )