Time dilation and the Jump Drive

[sablewyvern]

I am fairly certain that modern physics shows us that a ship moving 1-6 parsecs in one week has all the temporal problems associated with FTL travel, regardless whether it travels at FTL speeds in real space, uses a wormhole, or just simply teleports.

There are no fixes to the wholesale destruction of causality this causes if we wish to use current, real-world physics. If you out-pace light, no matter how you do it, you will arrive before you left.

Any qualified physicist is welcome to contradict me.

 

[aramis]

One of the postulations of Traveller is that a form of hyperspace exists, and the those jump drives allow you to go where either:
1) C is higher
2) correlations between real world and hyperspace points are closer in hyperspace.
3) the tunnel created by the drive takes a shortcut through X-dimensional space (10 is a popular number...) which makes the distance attainable in a week.

you don't travel in the physics sense; you remove yourself from the reference, simultaneously being placed into a totally different reference, and exit back to the first frame at a different point, having removed oneself completely from the issue of travelling supra-C by being outside the universe for the trip.

 

[sablewyvern]

My point was that physics doesn't care how fast you're moving in real space. It simply compares how long it takes you to get from A to B, relative to the speed of light.

If you are at point A, move to point B, and a photon leaving A for B at the same time you departed A arrives at B after you, then causality collapses. How you got there has no bearing on the matter.

I don't claim to understand how it works (it isn't intuitive by any stretch), but thems the facts as they have been explained to me by people who study the stuff.

Edit: The explanations you present are a worthwhile handwave for explaining how FTL is possible. They do not, however, handwave away any of the effects of FTL travel.

Further Edit: I'd just like to point out that, if my personal opinion carried any weight, I would consider aramis's theory that Jump avoids causality issues to be not merely intuitive and logicial, but self-evidently so upon brief inspection by a reasonable adult. Conversely, I would regard the points that I have raised in this thread, that causality violations are unavoidable, to be illogical, flawed, silly and without any real basis.

Unfortunately, it has been made clear to me, by people that study physics, relativity and causality, that my personal opinion (and the one aramis is presenting) is just plain wrong.

 

[Icosahedron]

I'm afraid I qualified too long ago in the murky past to argue the finer details with you, SW, but IIRC your friends are probably ignoring the essential point that Relativity defines causality by way of light travel because light travels faster than anything else. If a new mode of FTL travel is postulated, then messages transferred by that means rather than light would become the definition of causality.
Relativity creates too many headaches to include in a fun game - just leave go of it FFS!

 

[sablewyvern]

Well, maybe I misunderstood or was misinformed then.

I still feel it's too complex a situation to bother trying to deal with realistically in a game with as much handwavium as Traveller, but won't press the point any further on this particular issue.

Please carry on amongst yourselves.

 

[tjoneslo]

Further Edit: I'd just like to point out that, if my personal opinion carried any weight, I would consider aramis's theory that Jump avoids causality issues to be not merely intuitive and logicial, but self-evidently so upon brief inspection by a reasonable adult. Conversely, I would regard the points that I have raised in this thread, that causality violations are unavoidable, to be illogical, flawed, silly and without any real basis.

Unfortunately, it has been made clear to me, by people that study physics, relativity and causality, that my personal opinion (and the one aramis is presenting) is just plain wrong.

The problem is that general and special relativity violate common sense. If I'm driving down a road, and you're driving down the same road in the opposite direction, the speed which we are approaching each other isn't your speed plus my speed. If you step on the accelerator, you (and your car) get heavier. And time slows down. If I close you in an elevator, there's no way you can tell if the elevator is still sitting on the Earth or has been launched into space and is accelerating away. Other than opening the door.

So if you want to ignore the reality warping effects of relativity, please feel free. I will 100% agree that it is confusing and adds nothing to the game.

 

[Supplement Four]

I will 100% agree that it is confusing and adds nothing to the game.

That its confusing, there is no doubt. That it adds nothing to the game is debateable.

I enjoy merging the pseudo-science of Traveller with real life and coming up with a "solution". If it adds to the suspension of disbelief, it actually adds to the game (at least, to my game anyway).

Like reading tech in a scifi novel and saying to yourself, "Yeah...yeah..I get it."

 

[tjoneslo]

So let me see if I can unravel your original speculation:

You are traveling in a starship at some great speed. You Jump. Your speculation is that jump space affects your travel in some manner so that the effects of time dilation are undone to allow causality to occur properly.

As a classic example, and I calculated this out at once, if you have two starships (ship a and ship b) moving toward each other in two different systems (system A and system B, 1 parsec apart), and ship a jumps to system B, where upon ship b jumps to System A. According to the rules of relativity, if ship a and ship b are moving toward each other at greater than 100 km/s, ship b will arrive in system A before ship a leaves.

This contradicts the "common sense" idea that ship b should arrive in System A two weeks after ship a left.

The only way this works is if jump space becomes what is know as a preferred frame of reference. You measure all of your time passage relative to the time passage of Jump Space. That is there are two clocks in the universe, yours and that of jump space (instead of one, yours).

So once you enter jump space, your clock becomes synchronized with the Jump Space clock. In the example above, as ship a enters jump space it does so at a specific jump space time, and when ship b enters jump space it does so at a specific (later) jump space time. I think this means jump space has a speed of light of zero (0).

In any case, this requires jump space to exist as a single large construct that exists over all of charted space, and probably the galaxy.

It does fit neatly with the "wrinkled sheet" theory of jump space. That is, the Traveller maps are flat (and not 3D) because jump space exists only as a single parsec thick sheet that passes through some systems and not others.

No gravitons required.

 

[jfetters]

The only way this works is if jump space becomes what is know as a preferred frame of reference. You measure all of your time passage relative to the time passage of Jump Space. That is there are two clocks in the universe, yours and that of jump space (instead of one, yours).

But you are in a bubble of N-Space, so your clocks shoudn't be touched at all. (As I understand these things, anyway... I think I need another stout draft! )

In any case, this requires jump space to exist as a single large construct that exists over all of charted space, and probably the galaxy.

It does fit neatly with the "wrinkled sheet" theory of jump space. That is, the Traveller maps are flat (and not 3D) because jump space exists only as a single parsec thick sheet that passes through some systems and not others.

No gravitons required.

Now that is an interesting theory! But Grandfather created that, right?

 

[aramis]

But you are in a bubble of N-Space, so your clocks shoudn't be touched at all. (As I understand these things, anyway... I think I need another stout draft! )

More importantly, within that bubble of N-Space carried into J-Space, you aren't moving much, if at all.

 

[atpollard]

For the record, is there even a tiny chance that Einstein was wrong and Newton was right and all this 'causality' is just a very bad dream? mega:

 

[aramis]

chance? yes.

Likeyhood? no.

 

[tjoneslo]

But you are in a bubble of N-Space, so your clocks shoudn't be touched at all. (As I understand these things, anyway... I think I need another stout draft! )

Well, according to physics, each particle in your body, crew mates, ship, cargo, etc. has its own "clock". The idea behind the jump field is to keep all of them together in the proper order. The physics of jump treats the object going through the jump as one single object, a super sized proton for example.

The liquid hydrogen jump fuel is super-cooled to near absolute zero to form a condensate around the ship for this reason.

Were the protective jump field not there, even the Brownian motion of the atoms in your body is enough to have them scattered randomly as the "clocks" attempt to synchronize with the jump space clock.

Now that is an interesting theory! But Grandfather created that, right?

You know, as much as I like grandfather and his kids, that explanation has gone beyond cliche to simply overly tired. I prefer there to be some mystery left in MTU. Grandfather never created jump space, he just figured out how to use it.

 

[WingOver]

Further Edit: I'd just like to point out that, if my personal opinion carried any weight, I would consider aramis's theory that Jump avoids causality issues to be not merely intuitive and logicial, but self-evidently so upon brief inspection by a reasonable adult. Conversely, I would regard the points that I have raised in this thread, that causality violations are unavoidable, to be illogical, flawed, silly and without any real basis.

Unfortunately, it has been made clear to me, by people that study physics, relativity and causality, that my personal opinion (and the one aramis is presenting) is just plain wrong.

Thank you, I really enjoyed that.

 

[inexorabletash]

BTW, if you want a good introduction to the problems of FTL and causality from the perspective of someone interested in justifying FTL travel within an SF context, my physicist buddy has an FAQ on the subject: http://www.physicsguy.com/ftl/

He also comes up with a possible rationalization for how you can have FTL without causality violations that actually works better for Traveller than the SF universe that spawned the discussion (Star Trek). The short version: if you impose a rule that all entry and exit into your FTL medium (Jump Space, for Traveller) must be done from the same reference frame you are never in a position to create causality violations. (You violate conservation of angular momentum, but we can handwave that away too - perhaps the vented hydrogen ends up spinning very fast.)

This would mean a ship would have to accelerate to some velocity before it could enter Jump. For instance, you have to be at rest relative to the black hole at the center of the galaxy. (Then we can handwave that this isn't a universal special reference frame, but local to some large volume of space and FTL travel outside the volume is not permitted.) One could possibly use this as justification of the 100 diameter limit and mis-jumps - within 100D, the ship can't get close enough to the required velocity and the mismatch affects the ship in some unpleasant way.

This would not permit the proposed trick where you accelerate to a pre-calculated velocity before entering jump so you come out of jump already on a high-velocity path to your desination.

(I don't think this adds much to Traveller, but you may find it useful.)

 

[sablewyvern]

BTW, if you want a good introduction to the problems of FTL and causality from the perspective of someone interested in justifying FTL travel within an SF context, my physicist buddy has an FAQ on the subject: http://www.physicsguy.com/ftl/

Well, that seems to agree with the position I was presenting earlier. It still makes little sense to me D), but appears to make the same arguments I have heard previously. I'd be interested to hear from anyone qualified on the subject who believes the linked essay to be in error.

 

[Foxroe]

I think that the problem with relying on contemporary real-world physics and accepted theories about FTL travel, is that most of these postulations conclude that FTL travel is impossible. If this is the case, doesn't it sort of negate the primary modus operandi of Traveller?

I feel that Traveller, by its very nature, necessitates large deposits of the rare-earth element Handwavium (or at least gas giants with large cores of bovine excrement). So I would say that any one person's game theory about how J-drives work, is just as good as any other.

Although it would be nice to have a generally accepted theory...

- Fox