Faster-than-light and 'hard' scifi

Is there any explanation for FTL communication or travel that's still considered within the realm of possibility by modern physics? From what I understand, quite a few have been debunked, so is there any way a space opera setting could be considered plausible?

From relativity, causality, FTL - pick two.

edited 3rd Sep '12 9:39:00 AM by Yej

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specifically that's special relativity that you've got to drop. Which will take a great deal of explaining.

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... and while magically well-behaved wormholes might seem like a good workaround at first glance (no need to go fast if there are shortcuts to everywhere), those turn out not to play well with causality either. Unfortunately, one pretty much needs to actually be a physicist to be able to write anything FTL-related which won't immediately be recognized as wildly implausible by the scientifically literate.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.

To clarify the above, FTL being possible means time travel would logically have to be possible, too.

Wormholes are a popular work-around; you get from point A to point B faster than light does, not because you're outrunning it but because you're taking a shortcut. You will have to bite the bullet and drop causality, though.

edited 3rd Sep '12 11:11:31 AM by RTaco

Not necessarily; if special relativity turned out to be wrong, it would theoretically be possible to travel faster than light without overturning time travel, but there's mountains of evidence in favor of special relativity.

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Well, in most SF, relativity gets dropped. Or rather the authors quietly pretend it didn't exist in the first place. The neatest solution is if you drop relativity by pretending that some sort of absolute time-line exists, the very thing relativity says doesn't. (a.k.a. a preferred frame of reference)

edited 3rd Sep '12 11:30:34 AM by McKitten

I can't even imagine what a verse would be like that dropped casuality instead of relativity. Which is probably why it's almost never done.

edited 3rd Sep '12 11:32:53 AM by Archereon

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How does it sound if I make it so that any attempt to use wormholes as time-travel results in the scientists going psychotic and smashing the machine and each other with whatever they can get their hands on (I plan to use Hyperspace Is a Scary Place anyway, and this will just turn it up a bit)?

All of this stuff is only an issue if you see sci-fi 'hardness' as a measure of quality SF

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Well like others said, dropping one of the three doesn't break physics and physicists aren't likely to care. It's if you don't drop one of the three. Also, how you drop one of the three is where you require physics knowledge (and also require a lot of specialised knowledge to recognise when it is wrong but probably not as much to know when it is wrong).

Dropping relativity does break mainstream physics, by definition. Dropping causality breaks common sense. Dropping FTL may break the plot. It's a bind, isn't it.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.

Hm, that's what I thought. Thanks everyone. I'm actually not writing any hard science fiction, I was just curious.

A random thought: Would it be more plausible if the work takes place in a single solar system, but in multiple universes? I have no idea what would be required for inter-universe travel though.

Nobody does or can have much of an "idea what would be required for inter-universe travel". This universe is all we know; we can only speculate which, if any, of our science and even our logic applies to anything beyond it. We don't even have a concept of existence that can be meaningfully applied outside this universe, so, per "it all depends on what your definition of 'is' is", this is the ultimate unanswerable question. Which, as far as sci-fi is concerned, means you can go as wild as you please, pretty much.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.

I see. I thought maybe quantum mechanics had some theories about parallel universes.

A many-worlds interpretation of quantum mechanics (of wave-function collapse, specifically) does exist, but is of little use in this regard, because the only natural way to get from one world to another is to use time-travel: Go back to the point at which an event cause the two worlds to split, then make sure the outcome of that event is such that you end up in the world you're aiming for. So, once again, causality as we know it goes out the window. Might as well go with FTL in the first place, in you're prepared to accept that, if you see what I mean.

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.

^ As far as we're aware, causality is merely correlation. There is no hard tangible evidence of causality in the physics sense. (Seeing as how causality and cause and effect are not the same thing...)

Meaning we very well could disprove causality via science.

edited 3rd Sep '12 3:42:38 PM by MajorTom

Sliders was a fun TV show, but didn't give a flying feather about scientific accuracy, if that's the sort of thing you're considering.

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What do you mean? The lede of the 'pedia article on "Causality (physics)" reads:

edited 3rd Sep '12 3:47:36 PM by kassyopeia

Soon the Cold One took flight, yielded Goddess and field to the victor: The Lord of the Light.

Tapazan, brane (no, I didn't misspell that; it's "brane" as in "membrane") theory might be what you want. It's particle physics rather than quantum mechanics, an offshoot of string theory, and brain-bending (heh) stuff.

Links: 1. The Other Wiki's page on Brane Cosmology

2. A basic primer in brane theory

There's also a Star Trek novel by Diane Duane, called The Wounded Sky, that you may want to read. I think it's pretty good — it sidesteps rather than discards general relativity and causality, by postulating a way to step outside of time. If there's no time, there's no time to pass, and therefore, no "speed", so exceeding lightspeed isn't an issue. It sidesteps causality by assuming that the cause doesn't necessarily have to precede the effect.

edited 3rd Sep '12 3:57:05 PM by Madrugada

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That's not sidestepping at all - that's shattering it into a million tiny pieces.

My work does, but it also uses You Already Changed the Past, so things still flow in a coherent, albeit hard to follow, order.

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Play it carefully and you could probably get into the One Big Lie category.

I saw this clip recently, which may be of interest.

In short, with that in mind, it would be possible to use a higher dimension as a way to warp between places. Of course, the problem would still be how to actually access that dimension, and you'd still throw some physics in for a loop, but conceptually it's an idea.

edited 4th Sep '12 3:04:33 AM by AnotherDuck

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The easy way to describe it is to say you're ducking out of reality so you technically never travel faster than light. This can lead to some causality issues of seeing yourself arrive before you've departed but other than that there shouldn't be any issues with relativity.

I'm not terribly confident of my physics here, but I think that moving into an alternate universe (either a full alternate universe or a form of hyperspace) in which certain physical constants are different to those here might work. For example, the speed of light might be much, much larger, allowing for much higher speeds without the attendant time dilation or increase in mass.

How one accesses this "other space" is itself a potential issue, but I don't think it implausible that some as-yet unknown phenomenon may yet be discovered to allow that, leaving it seeming to me to be still a somewhat-hard form of sci-fi "faster-than-light" travel.

edited 4th Sep '12 6:49:18 AM by ArsThaumaturgis

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