Krasnikov tube vs Worm Holes and Alubierre Drive

[AmrlKJaneway]

The bottom line with all of these forms of metric engineering (warp drives, wormholes, or Krasnikov tubes) is that they rely on the same basic technology - that is to say a method of generating and controlling significant to astronomical amounts of exotic matter/energy that can violate the Average Null Energy Condition (ANEC). And because space and time are one and the same thing (space-time) then any kind of messing around with space is going to result in some form of messing around with time - which means potential time machines and potentially some form of Visser Collapse or an equivalent.

Going back to the original post on the thread - I'm not sure that it's correct to speak in terms of one or another of these being more or less realistic or plausible or 'hard science' - because they are all essentially different sides of the same coin in many respects. You can differentiate based on what you're wanting to do (and the tradeoffs involved) and the amount of exotic mass-energy required or the stability of the thing you are creating. But I don't think it really makes sense to speak in terms of what is more or less 'hard science'

My 2c worth,

Todd

So, if they all violate ANEC, why is it wormholes were chosen for OA?

Would the setting not work just as perfectly without them? Or is there a reason they are more feasible?

[Rynn]

Two out of three are in the setting. Void motes were heavily based on various speculative papers into warp drive configuration. Notably the idea of making them small to save on the inordinate amount of negative energy they would require (but bigger on the inside).

Two physicist members worked to design our wormholes and void drives IIRC. If they didn't include tubes I imagine it was for a good reason (I.e just having ANEC isn't enough). Perhaps the practicality of laying down such a massive construct.

[stevebowers]

The theory is that you can violate ANEC to a limited extent, allowing certain types of highly restricted metric construct. The somewhat strict restrictions we place on these constructs leads to further complications in the setting - and to me that makes them seem more realistic.

It would, of course, be possible to have a similar scenario to OA without wormholes and void bubbles- but history and communication in such a scenario would occur at a much slower pace. In the real universe I would expect that any sort of metric technology would be even more restrictive than we imagine in OA - maybe some very tiny comm-holes, at best - but even tiny comm-holes would radically change the nature of interstellar colonisation.

[AmrlKJaneway]

That makes sense.

[stevebowers]

Peter Kuhfittig came up with a solution that seems to allow wormholes with tolerably small amounts of exotic energy; there doesn't seem to be a similar solution for Krasnikov tubes, so they are probably too difficult to be practical.
(edit; the corrected figures are in this paper, which gives the dimensions we use in OA; https://arxiv.org/pdf/gr-qc/0508060.pdf )

[Drashner1]

So, if they all violate ANEC, why is it wormholes were chosen for OA?

Would the setting not work just as perfectly without them? Or is there a reason they are more feasible?

I wasn't present at the founding of OA, but joined not long afterward. Both wormholes and FTL capable warp bubbles existed in the setting at that time (warp bubbles were in very limited use, were tiny, and were solely the province of S5 and S6 minds). Warp bubbles were later retconned out of the setting for many years, until reintroduced in their current form as the basis for our reactionless drives (which existed in a different form prior to that point).

Both wormholes and warp bubbles in the early years of the project were based much more on popular/layman friendly scientific literature that had been written about them (mostly in the very late 80s and the 90s after Carl Sagan's book Contact led to Thorne and Morris 'inventing' a stable wormhole that didn't have a black hole sitting on top of it). They were very different from how we describe them now and with less basis in hard science. Thanks to Adam Getchell, a physics PHd, first wormholes were redesigned and warp bubbles were re-introduced.

I don't recall Krasnikov Tubes ever being discussed as a possible addition to the setting, and there seems to be much less theoretical background on them, so wormholes probably work better if we are considering the quantity of scientific papers - and presumably thought - that have been dedicated to them.

At various times in the early history of the project, there were occasional suggestions that wormholes should be removed (among other major changes), but the consensus always came back that we prefer the setting with wormholes. I don't really think you could say the setting would work 'just as perfectly' without the means to travel/communicate across large distances quickly.

Violation of the ANEC is really just an element of any kind of space-time engineering of this type (including Krasnikov Tubes, most likely), not really a problem in and of itself. That's what exotic matter/energy is for (and several current theories on WHs point to the possibility of such sufficient amounts being produced just by natural vacuum fluctuations to hold a WH open.)

Hope this helps,

Todd

[Worldtree]

The main questions that I have are-
-does everything have to happen in between multiple stars? When you want to go slightly closer to what OA considers plausible- which of course may not actually be what happens- I prefer to make as much as possible happen within a single solar system- especially one with lots of moons or artificial habitats. It's good to ask- Do you really need a large number of entire habitable planets...or do you really just need a large number of diverse locations? I know most space opera is more of a "thousand worlds or go home" kind of genera, but even our solar system is gigantic- most of the stories from all of history have happened on only our one planet, so sometimes it might be better to reframe the question as- how much time do the characters need to spend traveling through space and what kind of locations do they really need to go to? does this really need to be accomplished with wormholes?
Could they travel between moons of a gas giant, if you only need 8 or so locations?

I ask this in particular if your story is set within the next thousand years.

[Drashner1]

The main questions that I have are-
-does everything have to happen in between multiple stars? When you want to go slightly closer to what OA considers plausible- which of course may not actually be what happens- I prefer to make as much as possible happen within a single solar system- especially one with lots of moons or artificial habitats. It's good to ask- Do you really need a large number of entire habitable planets...or do you really just need a large number of diverse locations? I know most space opera is more of a "thousand worlds or go home" kind of genera, but even our solar system is gigantic- most of the stories from all of history have happened on only our one planet, so sometimes it might be better to reframe the question as- how much time do the characters need to spend traveling through space and what kind of locations do they really need to go to? does this really need to be accomplished with wormholes?
Could they travel between moons of a gas giant, if you only need 8 or so locations?

I ask this in particular if your story is set within the next thousand years.

Of course good stories (or even great stories) can happen in a single star system (or on a single planet or megastructure). You can even have multiple stars and solar systems to play with in a binary or multiple star system (which are very very common). And as you say, solar systems are HUGE - and each planet and moon (and large asteroid) within them is a WORLD.

For added fun, you can have megastructures that are themselves the size of world or even solar systems

For all its interstellar scale, OA is perfectly fine with the idea of very detailed and complex descriptions of worlds and solar systems (and habitats and megastructures) and with stories that are told on/in them. If a story is well done, we don't really care if it takes place across dozens of solar systems - or within the bounds of a single world or city or even building.

I can say that actually quite a lot of the stories set in OA are set in a single locale rather than hopping from system to system in the course of a single story.

Ultimately (as with so many things with OA) it comes down to what individual members feel like working on or including in their work.

Perhaps we should try to make that element of the setting clearer to more people consider playing at that scale?

Todd

[AmrlKJaneway]

So, if they all violate ANEC, why is it wormholes were chosen for OA?

Would the setting not work just as perfectly without them? Or is there a reason they are more feasible?

I wasn't present at the founding of OA, but joined not long afterward. Both wormholes and FTL capable warp bubbles existed in the setting at that time (warp bubbles were in very limited use, were tiny, and were solely the province of S5 and S6 minds). Warp bubbles were later retconned out of the setting for many years, until reintroduced in their current form as the basis for our reactionless drives (which existed in a different form prior to that point).

Both wormholes and warp bubbles in the early years of the project were based much more on popular/layman friendly scientific literature that had been written about them (mostly in the very late 80s and the 90s after Carl Sagan's book Contact led to Thorne and Morris 'inventing' a stable wormhole that didn't have a black hole sitting on top of it). They were very different from how we describe them now and with less basis in hard science. Thanks to Adam Getchell, a physics PHd, first wormholes were redesigned and warp bubbles were re-introduced.

I don't recall Krasnikov Tubes ever being discussed as a possible addition to the setting, and there seems to be much less theoretical background on them, so wormholes probably work better if we are considering the quantity of scientific papers - and presumably thought - that have been dedicated to them.

At various times in the early history of the project, there were occasional suggestions that wormholes should be removed (among other major changes), but the consensus always came back that we prefer the setting with wormholes. I don't really think you could say the setting would work 'just as perfectly' without the means to travel/communicate across large distances quickly.

Violation of the ANEC is really just an element of any kind of space-time engineering of this type (including Krasnikov Tubes, most likely), not really a problem in and of itself. That's what exotic matter/energy is for (and several current theories on WHs point to the possibility of such sufficient amounts being produced just by natural vacuum fluctuations to hold a WH open.)

Hope this helps,

Todd

That's great, thanks! I don't know much about the history of the setting, and I think it's great it's so flexible. This is my main problem with Star Trek. There are things that went great with the 60's reality of future space travel, that should have been re-written for the later series, but in order to keep a consistency, they refuse to retcon some of the ideas, and the setting just becomes less and less believable. Like the whole sub-space field thing should have been replaced with an Alcubierre metric by now. If OA isn't afraid to reconstruct an idea to comply with current theories/discoveries, I'm all for it!

[Drashner1]

That's great, thanks! I don't know much about the history of the setting, and I think it's great it's so flexible. This is my main problem with Star Trek. There are things that went great with the 60's reality of future space travel, that should have been re-written for the later series, but in order to keep a consistency, they refuse to retcon some of the ideas, and the setting just becomes less and less believable. Like the whole sub-space field thing should have been replaced with an Alcubierre metric by now. If OA isn't afraid to reconstruct an idea to comply with current theories/discoveries, I'm all for it!

The project is almost always in a low level state of reconstruction and ret-conning, with occasional surges in activity if circumstances warrant it. Lately we've seen a lot of activity around the early history of the timeline (not just expansion, but also altering existing content as our take on things changes).

At various times over the years we've also considered other alterations to our take on wormholes, or the removal of wormholes, or removing all the xenosophonts from the setting (although the general consensus has always come back to the fact that we like the setting better with wormholes and aliens ).

If some RL development definitively forced us to remove wormholes from the setting, then we'd probably do so - but so far that hasn't happened. There have been occasional articles indicating that wormholes might not be possible or that they might work rather different from what we depict - but these have been sufficiently theoretical that they count as another potential description of reality rather than a better description than the one that our WHs are based on.

Our general take on these things and to wait and see and only make major changes to core setting elements if the weight of theory seems to require it.

OTOH, we've done quite a lot of rapid updates based on the discovery of new planets in our portion of the galaxy

Todd