# How can warp drive not violate relativity?
**URL:** https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186
**Category:** Factual Questions
**Created:** [November 26, 2012, 7:13pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186 "2012-11-26T19:13:57Z")
**Posts on this page:** 20
**Page:** 2
### Author:  [@Mijin](https://boards.straightdope.com/u/Mijin)
#### Post date: [November 27, 2012, 3:51pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/21 "2012-11-27T15:51:08Z")
nm
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### Author:  [@billfish678](https://boards.straightdope.com/u/billfish678)
#### Post date: [November 27, 2012, 4:50pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/22 "2012-11-27T16:50:36Z")
> [@PlainJain](#):
>
> Not so sure about that. If TT is possible and on-going then there would be visitors from an unimaginably far off future. With enough time almost anything is possible. If a culture has the curiosity to pursue building a Time machine it seems logical that they would eventually explore everywhere. If that culture is earth-based I’m sure we would have gotten around to seeing our earlier selves by now.
If they are from way far in the future that means they have a bunch of history to visit. And even more future to visit. And consider that most very likely time or long distance space travel is never going to be easy or have most of the population doing it.
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### Author:  [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)
#### Post date: [November 27, 2012, 5:39pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/23 "2012-11-27T17:39:31Z")
I have no idea if time travel will ever be feasible, but lack of time travelers isn’t evidence of lack of time travel. The timeline has to go through at least one original iteration before time travel is invented so that there’s something to go back and travel to.
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### Author:  [@leahcim](https://boards.straightdope.com/u/leahcim)
#### Post date: [November 27, 2012, 6:15pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/24 "2012-11-27T18:15:51Z")
> [@jackdavinci](#):
>
> I have no idea if time travel will ever be feasible, but lack of time travelers isn’t evidence of lack of time travel. The timeline has to go through at least one original iteration before time travel is invented so that there’s something to go back and travel to.
That’s the thing. There’s nothing in the universe other than our intuition that says there has to be an “original timeline”. In fact, in some ways, having someone from the distant future start the universe _more_ matches our intuition about how things should work than having a single uncaused event staring it all, or having an infinite sequence of causes.
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### Author:  [@The\_Hamster\_King](https://boards.straightdope.com/u/The_Hamster_King)
#### Post date: [November 27, 2012, 6:27pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/25 "2012-11-27T18:27:24Z")
> [@cmyk](#):
>
> We observe red-shift of galaxies caused by the expansion of spacetime.
Yes. My mistake. I was remembering a result from a few years ago where they didn’t find time dilation for distant quasars. (Which, since now I know that distant galaxies DO experience time dilation, is really weird … .)
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### Author:  [@jackdavinci](https://boards.straightdope.com/u/jackdavinci)
#### Post date: [November 27, 2012, 6:56pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/26 "2012-11-27T18:56:58Z")
> [@leahcim](#):
>
> In fact, in some ways, having someone from the distant future start the universe _more_ matches our intuition about how things should work than having a single uncaused event staring it all, or having an infinite sequence of causes.
You know, that’s something that occurred to me a few years ago, as you mentioned mostly intuitively, but also as a reaction to the paradox of spontaneous existence, and that I think about from time to time. But in the last month I’ve suddenly seen several others proposing something similar, so now I’m wondering if there is a more concrete rationale. Have there been any investigations or papers written?
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### Author:  [@leahcim](https://boards.straightdope.com/u/leahcim)
#### Post date: [November 27, 2012, 8:33pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/27 "2012-11-27T20:33:23Z")
> [@jackdavinci](#):
>
> You know, that’s something that occurred to me a few years ago, as you mentioned mostly intuitively, but also as a reaction to the paradox of spontaneous existence, and that I think about from time to time. But in the last month I’ve suddenly seen several others proposing something similar, so now I’m wondering if there is a more concrete rationale. Have there been any investigations or papers written?
I don’t think there’s ever been any kind of concrete rationale other than, “I don’t like uncaused causes, and I don’t like infinite regress of causes, is there a way that the universe might be structured in a way that avoids the existence of things I don’t like”. Of course _I_ also don’t like time travel and the grandfather paradox either. Unfortunately the universe has long been indifferent towards my preferences for how it should work.
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### Author:  [@Trinopus](https://boards.straightdope.com/u/Trinopus)
#### Post date: [November 27, 2012, 10:47pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/28 "2012-11-27T22:47:35Z")
> [@cmyk](#):
>
> We observe red-shift of galaxies caused by the expansion of spacetime. Wouldn’t this be considered relativistic/time-dilation?
Not quite… The red-shift is a Doppler shift, and applies to any waves emitted from (and/or received by) moving objects. The classic freight-train whistle effect. It isn’t a time-dialtion thingy but just a moving source thingy. (Technical term there.)
Time dilation would be visible in, say, very distant Cepheid variables cycling through their periods too slowly.
> [@The\_Hamster\_King](#):
>
> Yes. My mistake. I was remembering a result from a few years ago where they didn’t find time dilation for distant quasars. (Which, since now I know that distant galaxies DO experience time dilation, is really weird … .)
Do, in fact, distant Cepheid variables cycle “too slowly,” i.e., exhibit time dilation? Or is this troublesome to observe or compute?
(“How far away is it?”
“Depends on how fast it’s moving.”
“How fast is it moving?”
“Depends on how far away it is.”)
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### Author:  [@Punoqllads](https://boards.straightdope.com/u/Punoqllads)
#### Post date: [November 27, 2012, 11:07pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/29 "2012-11-27T23:07:31Z")
Doesn’t the FTL = TT relationship rely upon the assumption that there is no preferred frame of reference in spacetime? Would it be possible for the act of warping spacetime to create a preferred frame of reference within its “bubble”, thereby making the assumption no longer true?
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [November 27, 2012, 11:33pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/30 "2012-11-27T23:33:05Z")
It wouldn’t just have to establish a preferred frame within its bubble (that’s easy to do); it’d need to establish a preferred frame _everywhere outside_ its bubble, too.
And I won’t swear it’s impossible for spacetime to have a preferred frame. It’s just that, if it does, then Special Relativity is wrong. Which it might be, but that’s not the way to bet.
Oh, and the redshift of distant galaxies is not, despite appearances, a Doppler shift. It really is due to the expansion of space, and really does behave in measurably different ways from a Doppler shift (though admittedly, the difference is subtle).
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### Author:  [@Trinopus](https://boards.straightdope.com/u/Trinopus)
#### Post date: [November 28, 2012, 2:50am UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/31 "2012-11-28T02:50:01Z")
> [@Chronos](#):
>
> . . . Oh, and the redshift of distant galaxies is not, despite appearances, a Doppler shift. It really is due to the expansion of space, and really does behave in measurably different ways from a Doppler shift (though admittedly, the difference is subtle).
Lum! My bad; I thought it was just a speed-recession shift. (Is that at least part of the red shift, or is it all from expanding space?)
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### Author:  [@cmyk](https://boards.straightdope.com/u/cmyk)
#### Post date: [November 29, 2012, 6:19am UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/32 "2012-11-29T06:19:39Z")
> [@Trinopus](#):
>
> Lum! My bad; I thought it was just a speed-recession shift. (Is that at least part of the red shift, or is it all from expanding space?)
A pure Doppler Shift is caused by the compression of waves between the discrete motions of objects relative to another in flat (or close/everyday) space.
But, since spacetime is also expanding, there’s also a red-shift that is, for lack of a better word, accumulative. The farther away we observe something, the stronger the shift, even if the galaxies weren’t moving through space relative to each other.
This would be like a train’s whistle changing pitch, because the earth and its atmosphere is expanding in size, despite the fact the train, nor you, are in motion relative to each other (imagining that all things situated on the planet would remain in their respective positions, like the dots on an inflating balloon analogy; as impossible as the planet doing this actually is, but hey… it’s an analogy).
There’s also _gravitational_ red-shift that would be very pronounced around event horizons, but that’s a whole 'nuther ball of mass…
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### Author:  [@Trinopus](https://boards.straightdope.com/u/Trinopus)
#### Post date: [November 29, 2012, 6:41am UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/33 "2012-11-29T06:41:17Z")
I see my oops; I was thinking that distant galaxies also had a high recessional “proper motion.” But, of course, they don’t. They might have a very _small_ recession speed (or even be moving toward us!) but the vast bulk of the Hubble Constant is expanding space. Brain fart: I do that a lot!
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### Author:  [@cmyk](https://boards.straightdope.com/u/cmyk)
#### Post date: [November 29, 2012, 7:27am UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/34 "2012-11-29T07:27:00Z")
Unacceptable! You’re supposed to have all the answers!
Excuse me, my brain needs to use the restroom…
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### Author:  [@moriah](https://boards.straightdope.com/u/moriah)
#### Post date: [December 2, 2012, 9:18am UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/35 "2012-12-02T09:18:56Z")
> [@jackdavinci](#):
>
> But it begs a few questions:
Umm… [Begging the question - Wikipedia](http://en.wikipedia.org/wiki/Begging_the_question#Modern_usage)
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### Author:  [@BigT](https://boards.straightdope.com/u/BigT)
#### Post date: [December 2, 2012, 10:07pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/36 "2012-12-02T22:07:52Z")
> [@Chronos](#):
>
> It wouldn’t just have to establish a preferred frame within its bubble (that’s easy to do); it’d need to establish a preferred frame _everywhere outside_ its bubble, too.
>
> And I won’t swear it’s impossible for spacetime to have a preferred frame. It’s just that, if it does, then Special Relativity is wrong. Which it might be, but that’s not the way to bet.
A book I have on the subject claims there already are two preferred reference frames. The first is one I’ve heard you admit–that rotating objects act differently that supposing the universe is spinning and the object is still. Thus the universe being still is a preferred reference frame.
The second is based on the background microwave radiation, and involves changing your velocity until measurements from all sides show the same amount of energy, with no side blue- or red-shifted. This latter idea was specifically said to offer a possible hole in Einsteins theories.
And, finally, we know that Special Relativity is wrong because, like General relativity, it breaks down at quantum levels.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [December 2, 2012, 10:18pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/37 "2012-12-02T22:18:31Z")
Saying that something isn’t rotating doesn’t specify a reference frame, though. There is a whole large family of reference frames in which any given object doesn’t rotate.
As for using the CMB, that’s fundamentally no different from using any other large object (the Earth, the Sun, the center of mass of the Galaxy, etc.) to establish a reference frame-- You’re just using the ultimate large object. Besides which, the CMB doesn’t actually specify a global reference frame, either: If we establish a reference frame here where the CMB shows no Doppler shift, and observers in some distant galaxy do the same, we won’t have the same reference frame.
And General Relativity is known to be inconsistent with quantum mechanics, but Special Relativity works just fine. All of the most detailed models we have of quantum mechanics, which describe the workings of physics to greater precision than anything else in history, are fundamentally built according to special relativistic principles. There have been some alternate models proposed where SR breaks down in extreme cases, but this has not been validated by any experimental test.
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### Author:  [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)
#### Post date: [December 2, 2012, 10:31pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/38 "2012-12-02T22:31:13Z")
> [@BigT](#):
>
> The second is based on the background microwave radiation, and involves changing your velocity until measurements from all sides show the same amount of energy, with no side blue- or red-shifted.
How can you do that if the universe is expanding?
Light to your right comes from things moving away from you; light to your left comes from things moving towards you.
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### Author:  [@ZenBeam](https://boards.straightdope.com/u/ZenBeam)
#### Post date: [December 2, 2012, 10:35pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/39 "2012-12-02T22:35:15Z")
It’s not correct to say that having a preferred frame implies Special Relativity is wrong. A closed universe will have a preferred frame and still satisfy Special Relativity. See [The twin paradox in compact spaces](http://arxiv.org/abs/gr-qc/0101014):
> [@](#):
>
> Twins travelling at constant relative velocity will each see the other’s time dilate leading to the
> apparent paradox that each twin believes the other ages more slowly. In a finite space, the twins
> can both be on inertial, periodic orbits so that they have the opportunity to compare their ages
> when their paths cross. As we show, they will agree on their respective ages and avoid the paradox.
> **The resolution relies on the selection of a preferred frame singled out by the topology of the space**.
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### Author:  [@Chronos](https://boards.straightdope.com/u/Chronos)
#### Post date: [December 2, 2012, 10:38pm UTC](https://boards.straightdope.com/t/how-can-warp-drive-not-violate-relativity/642186/40 "2012-12-02T22:38:54Z")
This may seem like a nitpick, but that’s for a topologically-identified space, not for a closed space. Closed spaces of trivial topology still don’t quite have a preferred reference frame, although you can still end up with similar twin-paradox issues (the resolution is slightly more complicated than in the topologically-identified case, but similar).
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