FTL in my book

[tomandlu]

Hi,

Apart from obviously being nonsense, does the following sort-of make sense (and, for bonus points, has anyone ever used this idea in fiction before):

“Let us suppose you travel at a little below the speed of light, and that for every second of ship time, a hundred seconds would pass externally.”

“Okay,” said Louie, concentrating hard and trying to ignore the constant discomfort of the ship’s acceleration.

“So, you complete a return journey that takes you a month, but you find that a hundred months have passed for everyone who stayed behind,” continued the machine. “In effect, the problem that cronium has to solve is not how long the journey takes for you, but how long it takes for a everyone else.”

“And that’s where the time-travel comes in?”

“Exactly – in the example I gave you, a cronium-shift during flight would gradually move you ninety-nine months into the past. The result would be that the journey would now have taken a month from all perspectives – stationary and moving.”

“I think I get it now,” said Louie. “But isn’t it dangerous? I mean, couldn’t you end up changing history or something?”

“Not at all,” said Cassita. “The shift available never allows you to arrive prior to your departure. Causality is always preserved”

“So I don’t get to kill my own grandfather?”

“Why would you want to do that?” said Cassita. “Was he unpleasant?”

Louie laughed. “No, he was really nice – well, one of them was. It’s just what people always say when time travel comes up.”

“Ah, I see. A paradox.”

... and if it does make sense, anyone want to tell CERN?

[Robert'); DROP TABLE *;]

It does make sense in a handwave capacity, but if you were clever, you could violate conservation of energy with it. (Since the "speed" of time is related to redshifitng of photons.)

[Macbi]

“So, you complete a return journey that takes you a month, but you find that a hundred months have passed for everyone who stayed behind,” continued the machine. “In effect, the problem that cronium has to solve is not how long the journey takes for you, but how long it takes for a everyone else.”

I don't understand. Your doing something to the people on the ship, and this makes the folks at home age more slowly?

[scarecrovv]

“So, you complete a return journey that takes you a month, but you find that a hundred months have passed for everyone who stayed behind,” continued the machine. “In effect, the problem that cronium has to solve is not how long the journey takes for you, but how long it takes for a everyone else.”

I don't understand. Your doing something to the people on the ship, and this makes the folks at home age more slowly?

As I understand it, the idea is that you go on your journey and come back, so you age 1 month and everybody else ages 100. Then you jump back in time by 99 months using handwavium so your history and everybody else's sync up. Except that the jump back in time is distributed across the whole journey.

[Izawwlgood]

The obvious question is what happens when/if you make a return journey along the same path. Or what happens if someone in the new timeline affects the ship in transit/arrival prior to it's jump back in time.

[tomandlu]

I don't understand. Your doing something to the people on the ship, and this makes the folks at home age more slowly?

As I understand it, the idea is that you go on your journey and come back, so you age 1 month and everybody else ages 100. Then you jump back in time by 99 months using handwavium so your history and everybody else's sync up. Except that the jump back in time is distributed across the whole journey.

Spot on...

[tomandlu]

The obvious question is what happens when/if you make a return journey along the same path. Or what happens if someone in the new timeline affects the ship in transit/arrival prior to it's jump back in time.

I'm not sure if either of those present a problem. You might 'see' yourself (since your image is essentially slower than you are), but you are never in the same time, same place as yourself from an earlier or later part of the journey. Bear in mind that you are not really going back in time in the ordinary sense - for every second of time that passes, the most you can go 'back' is <1... (if X is the amount of time the journey takes you, and Y is the time for the stationary observer, then the maximum shift available over the entire journey is Y-X).

I think it would look odd - you could pass the image of yourself on the way back, but not on the way out (just as you can pass a bit of rubbish you threw overboard on the way back into port, but not the reverse).

... of course my wavehandium avoids this rather confusing bit by making anything shifted invisible...

[AvatarIII]

the only problem i can see is if the ship is constantly travelling 9/10 of an instant back in time every instant, it's going to be continually occupying the same space, so you are going to have to do something that says it only shunts back in time once it has cleared the space that the ship occupied at the time you are going to be going back to,

so say the ship is going at 3x10⁸ms^-1 and the ship is, 300m long (3x10²) it will have to travel 10^-6s back in time every 2x10^-6 seconds.... i think.

[Izawwlgood]

Yeah I'm not sure I understood this properly: are you suggesting that while traveling at whatever speed you're going at, you are also constantly shifting backwards in time by exactly the same amount you lose due to time dilation?

Or, are you suggesting you make a trip, and upon arriving, instantly travel backwards in time by the equivalent length lost to relativity?

[tomandlu]

This one...

Yeah I'm not sure I understood this properly: are you suggesting that while traveling at whatever speed you're going at, you are also constantly shifting backwards in time by exactly the same amount you lose due to time dilation?

Not this one...

Or, are you suggesting you make a trip, and upon arriving, instantly travel backwards in time by the equivalent length lost to relativity?

Soon, their velocity reached half light-speed – over ninety thousand miles every second.

“Would you like to activate the shift?” asked Cassita, indicating a control.

“Sure,” replied Louie.

Cassita moved aside and Louie turned the simple switch. Outside, the universe returned to its normal shape and colour, the stars ahead and behind suddenly shifting away from them, the blue and red turning back to white. It was both impressive and slightly anticlimactic.

“That’s it then?”

“That’s it.”

“We’re travelling back in time?”

“Essentially, yes.”

Their speed was staggering and it was still increasing. The numbers were so large that Louie didn’t even like to try and think about them anymore. They made him feel light-headed and dizzy.

... at which point, for every second of ship time, they would be travelling back about 0.14 seconds externally

[Soralin]

The tricky part is avoiding simply going back into your own past. I mean, how would you limit that? If you tried limiting it to your speed, the question becomes: your speed, relative to what? I mean, in the story section there, it says they're moving at half light-speed, but half-light speed relative to what? (I suppose you could have some universal reference frame that your speed is compared against, although that's breaking relativity even further, which says that no such thing exists, and velocity (and thus rate of time passing) is all relative.)

For example, say that you're moving at .5c relative to Earth, and another object is also moving away from Earth at .5c in the same direction. Relative to that object, you're just sitting motionless and going back in time. And conversely, if you're sitting motionless relative to Earth, that means that you're traveling at a speed of .5c away from the aforementioned object, and since you're traveling at .5c (relative to that object), you should be able to activate the shift, and go back in time, relative to it.

[tomandlu]

The tricky part is avoiding simply going back into your own past. I mean, how would you limit that? If you tried limiting it to your speed, the question becomes: your speed, relative to what? I mean, in the story section there, it says they're moving at half light-speed, but half-light speed relative to what? (I suppose you could have some universal reference frame that your speed is compared against, although that's breaking relativity even further, which says that no such thing exists, and velocity (and thus rate of time passing) is all relative.)

For example, say that you're moving at .5c relative to Earth, and another object is also moving away from Earth at .5c in the same direction. Relative to that object, you're just sitting motionless and going back in time. And conversely, if you're sitting motionless relative to Earth, that means that you're traveling at a speed of .5c away from the aforementioned object, and since you're traveling at .5c (relative to that object), you should be able to activate the shift, and go back in time, relative to it.

Hmm... tricky...

Let's see...

You're travelling along the same path, same speed (relative to earth), as the other object (give 'em a wave). Then you turn on your shift, and at this point you start travelling back in time, relative to earth, 0.14 seconds for every second of earth-time. However, relative to the other ship, no shift should be available...

Yeah, I think you need a universal reference frame (gravitational centre of the universe?). Thank god for handwavium...

[tomandlu]

T(I suppose you could have some universal reference frame that your speed is compared against, although that's breaking relativity even further, which says that no such thing exists, and velocity (and thus rate of time passing) is all relative.)

... thinking about it, and a bit of a cheat, but there is a difference between rest and movement, otherwise the twin-paradox wouldn't work. e.g. two ships moving away from each other and 1/3 of C each does not produce the same result as one ship moving away from a stationary thing at 2/3 C. In the former, both twins age equally, but in the latter, the travelling twin will be younger than his stay-at-home sibling. This does seem to imply that there is an absolute 'rest'... or have I misunderstood?

[Robert'); DROP TABLE *;]

The twins paradox is resolved by considering that one of the twins must accelerate. It doesn't imply an absolute reference frame.

[tomandlu]

The twins paradox is resolved by considering that one of the twins must accelerate. It doesn't imply an absolute reference frame.

Ah, of course...

... okay, I think the solution is to say that the shift is relative to one's self at the time of turning on the shift... or something

[PM 2Ring]

Yeah, I think you need a universal reference frame (gravitational centre of the universe?).

Sorry, there isn't one. But you could use the comoving frame as a defacto rest frame.

While general relativity allows one to formulate the laws of physics using arbitrary coordinates, some coordinate choices are more natural (e.g. they are easier to work with). Comoving coordinates are an example of such a natural coordinate choice. They assign constant spatial coordinate values to observers who perceive the universe as isotropic. Such observers are called "comoving" observers because they move along with the Hubble flow.

A comoving observer is the only observer that will perceive the universe, including the cosmic microwave background radiation, to be isotropic. Non-comoving observers will see regions of the sky systematically blue-shifted or red-shifted. Thus isotropy, particularly isotropy of the cosmic microwave background radiation, defines a special local frame of reference called the comoving frame. The velocity of an observer relative to the local comoving frame is called the peculiar velocity of the observer.

Most large lumps of matter, such as galaxies, are nearly comoving, i.e., their peculiar velocities (due to gravitational attraction) are low.

I think it might be a good idea to have the time-shifting mechanism integral to the ship's drive, rather than having it as something that gets switched off & on (although that would mean getting rid of the scene quoted above). That way, your ship's world-line will always be a light-like geodesic, as far as the rest of the universe is concerned.

Thank god for handwavium...

Definitely!

[tomandlu]

I think it might be a good idea to have the time-shifting mechanism integral to the ship's drive, rather than having it as something that gets switched off & on (although that would mean getting rid of the scene quoted above). That way, your ship's world-line will always be a light-like geodesic, as far as the rest of the universe is concerned.

Yeah, I've been coming round to this opinion too. Not too much of a switch to handle...

[Kaelith]

But we do have a reference point, the atoms themselves. Our problem in understanding has been that we see this in the perspective of time, while the subject is of the particles that are moving. See, the closer you travel to the speed of light the slower your atoms age in relation to other atoms that are stationary, this we understand and has been proven with atoms clocks in real-life (atomic clocks being measured off energy pulses from atoms, which is universal and unchanging)..this being said, lets solve some problems.
No, you wouldn't ever see yourself (or grandfathers you may accidentally kill) because you never go back in time. Correctly, you are moving SLOWER through time. As stated n the original text, you cant ever go further back in time than your point of origin. There only seems to be a relative disparity in past/present/future when you have arrived back to where you were. Furthering this, as you accelerate, you accelerate the time dilation effect, and as you decelerate the opposite happens. There is no sudden shift in time.
So, with all this, we can say with certainty that you wouldn't occupy the same space as yourself. This would imply a staggering effect in space, where you would be in two places at once, which happen to be overlapping. By logic, we are time traveling, affected by space traveling within normal bounds of physics, not 'teleporting' which would be a travel through space while time remains constant, so no overlap would happen (just the same as, say, if you were to move your hand (theoretically) fast enough there is a 'blur' of where your hand was after you moved it. simply, that's not how space works). The act of traveling at the faster speed is the "switch" you would need to turn on 'time travel' mode.
Lastly, anyone moving at the speed you are at is also traveling time at the same speed...because the aging is only relativistic, someone going the same speed as you would be aging the same rate as you are. Doesn't matter in what direction, with you against you, doesn't matter because it is the same speed, and the only way to know if you would be aging faster or slower is to compare yourself to someone who is moving at a different rate. If you would to travel with a companion at near-light speed, both you and your companion would age at the same rate. then his side of the cabin detaches and you two are traveling side by side at NLS, same age rate (the distance in between you doesn't affect aging) then he turns his craft and heads in another direction, since the distance doesn't matter and you both are traveling at the same speed, you both are aging the same in reference to the point of origin(and to each other, same speed so you're practically standing still).

disclaimer time: im not a physicist, and have only looked up facts as needed/wanted, but the relativity theory and time travel have fascinated me for a long time and this is a subject that i have thought through many many many times before. theory crafting, logic, and a bit of evidence is all i have and if there's a flaw in my thought line please point it out. I hope this helps in your writing ;D
(ps, wrote late at night/early in morning so my apologies for grammar and spelling mistakes)

[Tass]

disclaimer time: im not a physicist, and have only looked up facts as needed/wanted, but the relativity theory and time travel have fascinated me for a long time and this is a subject that i have thought through many many many times before. theory crafting, logic, and a bit of evidence is all i have and if there's a flaw in my thought line please point it out.

There is. It is called theory of relativity for a reason. There is no absolute speed, only relative speed. If you are going at some speed one way and someone else is going "the same speed" the other way, then you are very much not aging at the same speed (both of you will see the other age slower).

Try to read the sticky thread about relativity in the main science forum.

[BlackHatSupport]

Interesting idea. And we'll just avoid the whole "occupying the same space" bit with some handwavium.

[Quizatzhaderac]

Hi,

Apart from obviously being nonsense, does the following sort-of make sense (and, for bonus points, has anyone ever used this idea in fiction before):

In Robin Cook's Abduction has time machines used similarly. However all of the action occurs on or inside the Earth so the book doesn't even go into as much detail as the sample from your book.

... and if it does make sense, anyone want to tell CERN?

It makes sense, but you're not actually solving the problem of FTL just restating it. I won't tell CERN because I don't think anyone's closer to time travel than FTL. However from a literary sense restating the problem like this seems like a good idea. Rephrasing the problem has been an important step in solving many problems. Also showing things from new perspectives is a big benefit of literature.

Regarding the reference frame: you can't actually have a absolute reference frame, but you can pick one and stick with it. Outside of a galactic core stars don't move at relativistic speeds next to their neighbors. Just have everything happen within a few hundred light years, don't have ships launch from each other, and don't talk about what would happen if you did.

Regarding the same space at the same time: Instead of continuously shifting back in time, you could do many tiny time shifts. Say the ship is 300 m long with a .01 dilation. To the observer on Earth the ship completely changes position every 3m/ c = 10 ns. So every 10 ns it shifts back in time 9.9 ns. To an outside observer the ship appears as 100 ships of 1/100 normal length sandwiched together. Looking out the front you'd see the back of the ship from 9.9 ns in the future, however they're be no paradox as it'd take 1000 ns to get a message to the back of the ship.

If you wanted to be trippy the ship could dock with itself, the actual experience being more like going in circles than moving through time.

[speising]

IMHO, saying you have a working time machine is on par, if not even equal to stating you have FTL.
so explaining an FTL drive with time travel is a tautology.

[tomandlu]

IMHO, saying you have a working time machine is on par, if not even equal to stating you have FTL.
so explaining an FTL drive with time travel is a tautology.

In terms of hard science, you're almost certainly correct - however, in this case, we don't have an FTL drive, we have a sub-FTL drive with time-travel used to offset the twin-paradox... oh, and Quizatzhaderac, I wasn't serious about CERN - it's just that the original post coincided with CERN having those odd results where particles seemed to have travelled FTL... (no longer the case, I'm sad to say...)

[bouer]

One thing I am concerned with is:

Soon, their velocity reached half light-speed – over ninety thousand miles every second.

I certainly would not want to accelerate to 1/2 c in a short time, accelerating at 1G would take over 4000 hours to reach that speed.

[tomandlu]

One thing I am concerned with is:

Soon, their velocity reached half light-speed – over ninety thousand miles every second.

I certainly would not want to accelerate to 1/2 c in a short time, accelerating at 1G would take over 4000 hours to reach that speed.

I have some special engines powered by "inverted gravitons" (a handwavium isotope):

The main engines were different. They used a linear accelerator that stuck out of the rear of the ship, which accounted for the long complicated tail, and consequently would drive them forward rather than up. Normally, this would have had the effect of turning the rear wall of the ship into a deck, but the main engines used inverted gravitons as part of their mix – strange particles that were responsible for transmitting the force of gravity. The resulting reaction would not even be felt, and Cassita intended to leave the electron engines firing at 1 G so that they wouldn’t be floating around. The graviton engines, meanwhile, would be generating 20,000 Gs, but the ship and its occupants wouldn’t feel any of it.

Mainly because, as you note, it would otherwise take forever to get anywhere. I do have some long treks - the graviton engines cannot be used in-system, which necessitates a fairly slow slog out of a sun's gravity-well (unless the system in question has a 'momenta-shunt' - another bit of handwavium):

“Most populated systems – including this one – are equipped with momenta-shunts,” explained the machine. “They can be used to either apply or remove velocity from a ship.”
“We’ll just stop dead?”
“Essentially, yes. They have their limitations, but they can cope with velocities up to about half the speed of light.”

and...

They were still travelling at a third of the speed of light, and there was no real chance of seeing the shunt until they were inside it, but he couldn’t resist trying. Cassita had described it to him in some detail, so he had a fairly good idea of what it should look like – a hollow sphere twenty miles across, studded with wide tubes that poked out into space. Louie imagined that it must look like a gigantic sea urchin. The tubes were the critical part of the shunt – arriving ships would roar down them at ridiculous speeds, only to be brought to a sudden halt by a series of shaped graviton fields. The tremendous energies involved would then be stored, before being applied to departing craft, hurling them outwards like stones from a sling.

Once again, necessity being the mother of invention...

[eSOANEM]

One thing I am concerned with is:

Soon, their velocity reached half light-speed – over ninety thousand miles every second.

I certainly would not want to accelerate to 1/2 c in a short time, accelerating at 1G would take over 4000 hours to reach that speed.

I have some special engines powered by "inverted gravitons" (a handwavium isotope):

The main engines were different. They used a linear accelerator that stuck out of the rear of the ship, which accounted for the long complicated tail, and consequently would drive them forward rather than up. Normally, this would have had the effect of turning the rear wall of the ship into a deck, but the main engines used inverted gravitons as part of their mix – strange particles that were responsible for transmitting the force of gravity. The resulting reaction would not even be felt, and Cassita intended to leave the electron engines firing at 1 G so that they wouldn’t be floating around. The graviton engines, meanwhile, would be generating 20,000 Gs, but the ship and its occupants wouldn’t feel any of it.

Mainly because, as you note, it would otherwise take forever to get anywhere. I do have some long treks - the graviton engines cannot be used in-system, which necessitates a fairly slow slog out of a sun's gravity-well (unless the system in question has a 'momenta-shunt' - another bit of handwavium):

"inverted gravitons" made me cringe a bit.

I don't mind phlebotinium, but please don't use real science words to describe it unless you're sure you're using them in a reasonable way. Say it uses handwavions if you want, or say it uses an inertia-decoupling device or somesuch but please, don't use real science in ways it doesn't work.

[tomandlu]

"inverted gravitons" made me cringe a bit.

I don't mind phlebotinium, but please don't use real science words to describe it unless you're sure you're using them in a reasonable way. Say it uses handwavions if you want, or say it uses an inertia-decoupling device or somesuch but please, don't use real science in ways it doesn't work.

Mildly disagree (although I take your point). AFAIK gravitons are still theoretical particles, so there doesn't seem any particular harm in ascribing sci-fi attributes to them (particularly when manipulated by 'inversion'). That aside, if I want a reactionless drive (essential if my protagonist isn't going to die of old age and/or boredom every time he goes anywhere), then why invent a new thing when gravitons present themselves so naturally to the scenario?

Is it really any worse than photon torpedoes? (and if you hate those as well, there are some heavily-armed nerds who would like a 'word' with you )

[eSOANEM]

Gravitons are indeed theoretical particles, but they have to behave in a way which gives rise to GR. This puts significant restrictions on how they can behave. Also "inversion" of a particle doesn't really make any sense and the closest sensical interpretation would be that it is some combination of charge, parity or time inversion which, seeing as gravitons need to be neutral bosons corresponds to talking about anti-gravitons which are just gravitons.

Gravitons cannot behave like that.

Photon torpedoes are also pretty abusive (although this is mainly because they are shown to be actual torpedoes rather than just a high-intensity laser pulse) but there are far too many problems with trek physics that it's difficult to object to any one particular bit. Furthermore, trek is not trying to be at all hard with its science. It is perfectly happy hand waving everything. You clearly are not (otherwise you wouldn't feel the need to explain the FTL). There is no point sorting out your FTL properly if you then abuse real science for your plot-device-to-ignore-inertia.

Also, what you're describing isn't reactionless, but rather inertialess (at least partially so). A reactionless drive is one which violates conservation of momentum (by not ejecting a reaction mass/accelerating some other mass it has "traction" (in some sense) with) whereas what you're suggesting is one where the passengers do not feel the inertial forces due to their bodies' resistance to acceleration.

[tomandlu]

Gravitons are indeed theoretical particles, but they have to behave in a way which gives rise to GR. This puts significant restrictions on how they can behave. Also "inversion" of a particle doesn't really make any sense and the closest sensical interpretation would be that it is some combination of charge, parity or time inversion which, seeing as gravitons need to be neutral bosons corresponds to talking about anti-gravitons which are just gravitons.

Gravitons cannot behave like that.

Photon torpedoes are also pretty abusive (although this is mainly because they are shown to be actual torpedoes rather than just a high-intensity laser pulse) but there are far too many problems with trek physics that it's difficult to object to any one particular bit. Furthermore, trek is not trying to be at all hard with its science. It is perfectly happy hand waving everything. You clearly are not (otherwise you wouldn't feel the need to explain the FTL). There is no point sorting out your FTL properly if you then abuse real science for your plot-device-to-ignore-inertia.

Also, what you're describing isn't reactionless, but rather inertialess (at least partially so). A reactionless drive is one which violates conservation of momentum (by not ejecting a reaction mass/accelerating some other mass it has "traction" (in some sense) with) whereas what you're suggesting is one where the passengers do not feel the inertial forces due to their bodies' resistance to acceleration.

My bad (with the 'reactionless' - a silly mistake, and not one I make in the book iirc. I have a vague recollection that inertia is a bad word, and one should always talk about momentum, but that's a different matter).

I dunno - my book isn't hard sf or soft, but somewhere in the middle. I try to be fairly realistic when working with stuff that we know about directly (relativity, g-forces, distances, etc.), but flexible when proposing handwavium-type solutions (cronium for time-travel, inverted gravitons for high-g drives, etc.). Besides, I don't attempt to give a definition of what 'inverted' might specifically mean (inverted around which dimension?), so I find it acceptable - especially as they are theoretical particles anyway and no real indication is given as to what else the graviton drive is doing to facilitate the process.

I guess it's down to taste - if, in Star Wars*, someone said that light sabres used 'harmonically resonating photons' or something, I wouldn't wince (whether I should or not is another matter), but midi-clorians make me puke. I guess I felt that gravitons were close enough, in terms of the types of forces they are associated with, to make choosing them over a totally made-up bit of handwavium the preferred option, but I don't have a problem with you having a different opinion.

* like Star Trek, it's possible that Star Wars may not be entirely realistic...

[eSOANEM]

Yeah, it is probably a matter of taste.

For me, the problem with midichlorians was the retcon rather than the handwaving. Luckily for me, the films tend to ignore most of the science enough that their explanations don't bug me.

Like I say, for me at least, I feel that, once you go down the road of trying to explain how things work you need to be consistent with known science but YMMV and it is your book.

It's probably worth noting that my favourite sci-fi author used to be an astronomer and his books are fairly hard (there are some soft elements but they're usually acquired through various means such that the characters don't know how it works and so there are no explicit contradictions with known science) also that, in the idea I have for a sci-fi story, the time travel/FTL device was never designed by anyone and exists solely in a closed worldline and so no attempt to explain its function is made and none of the characters understand it.

[Izawwlgood]

For me, the problem with midichlorians was the retcon rather than the handwaving.

I just want to interject here; the issue with midichlorians was that it took the entire premise of being a Jedi as being something that anyone with dedication and perseverance could aspire to, a code and way of existence anyone could undertake, and made it instead some trick of breeding. Just kidding, YOU didn't accomplish shit, your parents were just fill of these fortune symbiotes! Enjoy having magical powers, and don't worry, muggles won't ever fuck with you again!

It was horse shit. It took Luke Skywalker, the blandest of protagonists we could all write ourselves onto, and made his journey of self discovery and hard work a Superman story instead of a Batman story.

[tomandlu]

It was horse shit. It took Luke Skywalker, the blandest of protagonists we could all write ourselves onto, and made his journey of self discovery and hard work a Superman story instead of a Batman story.

Nicely put. I'd never really thought about it beyond my initial reaction of 'yuck'. It was as though the writer stopped half-way through Rapunzel to explain that the protagonist had a keratin mutation or something.

In fairness to Lucas (?!?) there was all that "the force is strong in this one" in the original trilogy, but that's a vague enough sentiment to allow for any number of interpretations.

[tomandlu]

Yeah, it is probably a matter of taste.

And knowledge...

TBH if I was worried about satisfying someone who could say "seeing as gravitons need to be neutral bosons corresponds to talking about anti-gravitons which are just gravitons.", I'd have written something else.

Hell, my opening chapter is set at CERN and includes a lecture by a physicist. I now tend to avoid dark alleys nears science labs...

[PM 2Ring]

The resulting reaction would not even be felt, and Cassita intended to leave the electron engines firing at 1 G so that they wouldn’t be floating around. The graviton engines, meanwhile, would be generating 20,000 Gs, but the ship and its occupants wouldn’t feel any of it.

Just a minor quibble: it'd be wonderful if you use small 'g' instead of big 'G' when talking about acceleration. I know lots of people use 'G' for acceleration, but it always bugs me because 'G' is the universal gravitational constant (which does NOT have the same units as acceleration).

From http://en.wikipedia.org/wiki/G-force#Unit_and_measurement

The unit of measure of acceleration in the International System of Units (SI) is m/s². However, to distinguish acceleration relative to free-fall from simple acceleration (rate of change of velocity), the unit g (or g) is often used. One g is the acceleration due to gravity at the Earth's surface and is the standard gravity (symbol: g_n), defined as 9.80665 metres per second squared,[3] or equivalently 9.80665 newtons of force per kilogram of mass.[4]

The unit g is not one of the SI units, which uses "g" for gram. Also "g" should not be confused with "G", which is the standard symbol for the gravitational constant.[5]

[tomandlu]

Just a minor quibble: it'd be wonderful if you use small 'g' instead of big 'G' when talking about acceleration. I know lots of people use 'G' for acceleration, but it always bugs me because 'G' is the universal gravitational constant (which does NOT have the same units as acceleration).

Hmm... easily fixed, but now I've got to decide between making physicists wince or potentially confusing others... most people associate g with grams (correctly) and have probably never heard of the UGC, but on the other hand, the context is unlikely to cause confusion ("why is the spaceship accelerating at 20,000 grams?").

[PM 2Ring]

Hmm... easily fixed, but now I've got to decide between making physicists wince or potentially confusing others... most people associate g with grams (correctly) and have probably never heard of the UGC, but on the other hand, the context is unlikely to cause confusion ("why is the spaceship accelerating at 20,000 grams?").

Well, you could follow Wikipedia's suggestion and use an italic g.

I guess it's reasonable to suggest that most people have never heard of G. Hopefully, some of those have heard of Newton's theory of gravitation. But it saddens me to think that a majority of people reading a science fiction story about space travel are totally ignorant of the universal gravitational constant.

[snowyowl]

"accelerating at 20,000 grams" could be referring to grams-force. A bit of an arcane reading, mind you, especially since the symbol for gram-force is, perhaps obviously, gf. It's not totally nonsensical, but it's esoteric enough that people who see "an acceleration of 20,000g" will probably interpret it correctly.

[Izawwlgood]

Spoilered for OT:

Spoiler:

It was horse shit. It took Luke Skywalker, the blandest of protagonists we could all write ourselves onto, and made his journey of self discovery and hard work a Superman story instead of a Batman story.

Nicely put. I'd never really thought about it beyond my initial reaction of 'yuck'. It was as though the writer stopped half-way through Rapunzel to explain that the protagonist had a keratin mutation or something.

In fairness to Lucas (?!?) there was all that "the force is strong in this one" in the original trilogy, but that's a vague enough sentiment to allow for any number of interpretations.

I'm not sure you caught my point; I wasn't upset that they used bad science, I was upset that their retconning actually changed the theme of the story. It became, as I said, not a story of Batman rising to face the challenges that could befall any of us, but of Superman, a simply naturally gifted individual who doesn't work for his powers.

'The force is strong in this one' before mitichlorians means 'This person has potential, this person has dedication and tenacity and is the master of their own destiny'. After you add mitichlorians, it just means 'This person has magical space powers and will use them'.

It's somewhat irrelevant to your own story, because you're not retconning anything, but at the very least, maybe consider how applying explanations affects things.

[snowyowl]

but at the very least, maybe consider how applying explanations affects things.

Unspoilered for on-topic.

Science-fiction doesn't have to be "hard", or we wouldn't have any soft science fiction. If the story isn't about the machines and the physics (some stories are), why do you need to have them? (not rhetorical, usually there's a reason if you think about it.)
Sure, you can have a story about vacuum decay and controlling the wavefunction collapse. You can also have a story which focuses on the plot and characters, and where FTL is achieved by "we have these really long tubes that are totally opaque, and that lets you travel interstellar distances in a reasonable time because it's not really faster than light if there is no light, now is it?". Or anywhere in the middle ground.

I'm just suggesting that while it's a very good idea to work out the behind-the-scenes physics so that you have a plausible reason why the Entreprise can't just teleport parts of their enemies' life-support system into their transporter room, and so you know what sort of tactics and trickses would be available to a skilled antagonist, it's not necessarily a good idea to explain all the details in the story. Try to avoid technobabble-heavy infodumps (warning: TVTropes links).

Real life example: most people have a relatively vague idea of how a computer works. We probably have some mental image of a sequence of transistors that manipulate 1s and 0s, and anyone who uses a computer regularly will use words like "program", "website", and "memory", but only comparative experts know about weird things like "x86 architecture" or "memory allocation". The "1s and 0s" line can be given somewhere in the middle of the story, when you want to show the characters just chilling around and relaxing, and also provide some background exposition. The "programs" and "memory", the parts that are tangentially relevant to the story, can be dropped in without explicitly explaining them, but letting the context speak for itself ("The hard drive is nearly full. Can we get rid of your 20 GB folder of cat pictures?").

So in response to your OP: is that scene really necessary for the story? (P.S. It's not just this scene, allegedly this is something you should be asking about every page of your book.)

[eSOANEM]

but at the very least, maybe consider how applying explanations affects things.

Unspoilered for on-topic.

Science-fiction doesn't have to be "hard", or we wouldn't have any soft science fiction. If the story isn't about the machines and the physics (some stories are), why do you need to have them? (not rhetorical, usually there's a reason if you think about it.)
Sure, you can have a story about vacuum decay and controlling the wavefunction collapse. You can also have a story which focuses on the plot and characters, and where FTL is achieved by "we have these really long tubes that are totally opaque, and that lets you travel interstellar distances in a reasonable time because it's not really faster than light if there is no light, now is it?". Or anywhere in the middle ground.

I agree with your first point that sci-fi does not have to be soft.

I disagree with your point about the long tubes. In my view, a bad explanation is far worse than no explanation. If you say you're story has FTL that's cool, but if you explain it then it better be good.

Now, you can make this choice between no explanation and good explanations for each piece of not-real-world tech in your story and still (in my view) end up with something which is not 'bad'. The badness only comes in when your explanations simply don't work (like the opaque tubes).

Furthermore, you can have depths of explanation e.g. say you have some device to allow for quick travel between systems. The softest approach is "it's an FTL drive"; The hardest approach is the Alcubierre solution (ignoring all the reasons why it doesn't work as an FTL drive); in between you have everything in between from "it jumps to hyperspace" to "it jumps to a parralel brane where the speed of light is faster and then jumps back" through "it reduces its passengers' inertia but I can't quite remember the specifics".

There is nothing wrong with not explaining or offering only partial explanations, particularly if it is something the characters themselves aren't going to know how it works e.g. "how does the warp drive work" "how the hell should I know? I'm just the pilot not a warp drive technician"

I'm just suggesting that while it's a very good idea to work out the behind-the-scenes physics so that you have a plausible reason why the Entreprise can't just teleport parts of their enemies' life-support system into their transporter room, and so you know what sort of tactics and trickses would be available to a skilled antagonist, it's not necessarily a good idea to explain all the details in the story. Try to avoid technobabble-heavy infodumps (warning: TVTropes links).

I agree with this although I disagree on the best way to avoid such silly things. I think the best way to avoid this is not to work out the internal physics but just to set up some arbitrary rules which your tech follows. With the example of beaming the life support systems over, you could make the requirement that the transporter cannot transport objects if things (currents/fluids etc.) are flowing into/out of them at any point but, if you make this restriction, either people need to hold their breath to be transported.

Real life example: most people have a relatively vague idea of how a computer works. We probably have some mental image of a sequence of transistors that manipulate 1s and 0s, and anyone who uses a computer regularly will use words like "program", "website", and "memory", but only comparative experts know about weird things like "x86 architecture" or "memory allocation". The "1s and 0s" line can be given somewhere in the middle of the story, when you want to show the characters just chilling around and relaxing, and also provide some background exposition. The "programs" and "memory", the parts that are tangentially relevant to the story, can be dropped in without explicitly explaining them, but letting the context speak for itself ("The hard drive is nearly full. Can we get rid of your 20 GB folder of cat pictures?").

This I agree with entirely.

Unless the point of your story is how the tech works then the reader does not need to know anything more about the tech than the characters plausibly would themselves. If you want to know how much the pilot of a spaceship would know about his FTL drive, ask yourself how much you know about how the engine in your car works. If you want to know how much your character knows about the implants in his brain which feed him personalised adverts, ask yourself how much you really know about how the internet works.