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Old 11-14-2019, 06:58 AM   #31
shawnhcorey
 
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Default Re: FTL 'Fuel' [Space]

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Originally Posted by vicky_molokh View Post
Instantaneous travel for any non-negligible distance is FTL by definition, and messes up causality just as much.
All FLT messes up causality.
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Old 11-14-2019, 07:00 AM   #32
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Default Re: FTL 'Fuel' [Space]

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Originally Posted by vicky_molokh View Post
Instantaneous travel for any non-negligible distance is FTL by definition, and messes up causality just as much.
I think arbitrary FTL breaks causality. If you restrict it to fixed routes I think you can have a set that doesn't break things. This means that either the players can't create arbitrary gates or can't create them at all and they are Ancient tech.
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Old 11-14-2019, 07:37 AM   #33
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Default Re: FTL 'Fuel' [Space]

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I think arbitrary FTL breaks causality. If you restrict it to fixed routes I think you can have a set that doesn't break things.
No, there is no god-frame. All FLT travel breaks causality.
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Old 11-14-2019, 08:26 AM   #34
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Default Re: FTL 'Fuel' [Space]

I think it's not about god-frames, but forbidding any route that allows the observation of events out of sequence. I think they're really constrained and arbitrary, but not impossible for hypothetical "FTL highways".
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Old 11-14-2019, 08:29 AM   #35
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Default Re: FTL 'Fuel' [Space]

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I think it's not about god-frames, but forbidding any route that allows the observation of events out of sequence. I think they're really constrained and arbitrary, but not impossible for hypothetical "FTL highways".
If you forbid any route that causes out of sequence, you have limited everything to slower than light.
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Old 11-14-2019, 08:48 AM   #36
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Default Re: FTL 'Fuel' [Space]

Not necessarily. There is disagreement whether causality breaking is real or just a mathematical artifact (it is impossible to know). For example, if we assume absolute numbers in the relevant calculations, then there are no malfunctions in causality (it also means that exceeding c would have some other interesting effects). Of course, is an untestable mathematical fix at this point in time.
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Old 11-14-2019, 08:59 AM   #37
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Default Re: FTL 'Fuel' [Space]

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No, there is no god-frame. All FLT travel breaks causality.
lwcamp had a good solution in his Verge setting. Basically, the moment before a wormhole would result in the creation of a time machine, the cosmic laws of the universe come in and delete it (it's actually some complicated resonances or somesuch that destabilize and destroy the wormhole, but it works out to the same effect). When this is due to the interaction of two wormhole tunnels, the weaker of the two loses and ceases to exist (this is actually the basis for a type of warfare in the setting). So, it works out to be FTL travel (although the author insists it doesn't count as such, as it's just a shortcut through space) that doesn't, as far as I can tell, break causality.

Relevant to the thread, those do use a sort of fuel, but it doesn't need to be anything special. Basically, the wormhole mouths are actually physical structures with mass and all that. When you enter a wormhole mouth, it gains mass equal to your own. When you exit a wormhole mouth, it loses mass equal to your own. If one end ever reaches 0 mass, the wormhole collapses. So, over time, any amount of matter that goes through in one direction must eventually go through in the other direction. Balance is typically maintained by shunting water ballast through the wormhole.
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Old 11-14-2019, 09:01 AM   #38
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Default Re: FTL 'Fuel' [Space]

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... if we assume absolute numbers in the relevant calculations, then there are no malfunctions in causality ...
Yes, if you assume there is a god-frame, Relativity becomes relative to the god-frame. Other calculations in Relativity is just a shortcut. That is, rather than calculating Relativity from one frame to the god-frame and then calculating from the god-frame to another frame, you can calculate directly from one frame to another.

But there is no god-frame. Reality is what you measure it to be, nothing more.
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Old 11-14-2019, 09:09 AM   #39
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That is an untestable proposition, so it is not scientifically relevant. Relativity says all frames are relative, not that there are no absolute frames. If the Universe is just one of many, then its frame is relative to the frames of other Universes while effectively functioning as an absolute frame for its components.

Last edited by AlexanderHowl; 11-14-2019 at 09:21 AM.
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Old 11-14-2019, 11:34 AM   #40
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Jump gates that work by bending space rather than actually going FTL shouldn't have any of those problems as far as I can tell.
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