Incoming wormhole anomaly

[Splitsecond]

Incorrect: the black box is equipped with its own "warp drive" to allow it to return to Earth at FTL speeds. There is nothing to prevent this from being the case. It takes, for example, 58 seconds (using its "warp drive") to get back to Earth in the probe's frame, and since the probe is traveling away from Earth at 0.5c (e.g., because the reactor exploded, but the probe is really well built), the black box's travel time in the Earth's frame is -200 seconds, meaning it reaches the Earth about a hundred seconds before the probe left.

Unless, of course, you're saying that there is some reason that things can go "back in time" in the USS Einstein's frame of reference but not in the Earth's.

The black box doesn't travel faster than light relative to the space it occupies or the light around it. A warp drive gives the space around an object a velocity greater than c. The object continues at very slow speeds relative to space. The black box is always non-relativistic even though it has performed FTL travel. Special relativity is not used in these FTL situations. Causality is not broken.

[Quadhelix]

The black box doesn't travel faster than light relative to the space it occupies or the light around it. A warp drive gives the space around an object a velocity greater than c. The object continues at very slow speeds relative to space. The black box is always non-relativistic even though it has performed FTL travel. Special relativity is not used in these FTL situations. Causality is not broken.

I'm sorry, this is my fault for using the term "warp drive." The type of drive doesn't matter. The point is that the black box disappears from the probe and reappears at Earth about 58 seconds later according to the probe and 200 seconds earlier, according to an observer on Earth.

[escyos]

i also though that the gates waited a bit to get a few symbols and then connects with gates that have those first few symbols. as the person keeps dialling it finds the gate your trying to dial and then finds the one , you press the big red button and presto!

[Quadhelix]

i also though that the gates waited a bit to get a few symbols and then connects with gates that have those first few symbols. as the person keeps dialling it finds the gate your trying to dial and then finds the one , you press the big red button and presto!

The problem with that idea is that we have never seen a Stargate start to light up from an incoming wormhole, only then to shut down because, oops, they were dialing somewhere else.

[Splitsecond]

I'm sorry, this is my fault for using the term "warp drive." The type of drive doesn't matter. The point is that the black box disappears from the probe and reappears at Earth about 58 seconds later according to the probe and 200 seconds earlier, according to an observer on Earth.

The disappears/reappears comments shows that the probe travels through an alternate region of space-time at less than the speed of light in that region or simply changes its position in space-time. Either way, it never actually travels faster than c. While FTL is possible, an object cannot travel at more than c itself. All possible FTL solutions are a work around to make the object effectively FTL not actually FTL.

[Quadhelix]

The disappears/reappears comments shows that the probe travels through an alternate region of space-time at less than the speed of light in that region or simply changes its position in space-time. Either way, it never actually travels faster than c. While FTL is possible, an object cannot travel at more than c itself. All possible FTL solutions are a work around to make the object effectively FTL not actually FTL.

Unless I'm missing something major, all of that is irrelevant because the black box still makes it back to Earth before the probe left.

The basic facts are as follows:

1. The "probe" is at r=0 (Earth) at t=0, at which point it engages its FTL (of any type: wormhole, "warp drive," etc.)
2. The probe is at r=500c*s at t=100s
3. The probe accelerates to 0.5c in negligible time (negligible time to avoid a significant change in r); its direction of travel is directly away from Earth.
4. The probe launches an FTL-equipped black box back to Earth once it has stopped accelerating.
5. In the probe's frame of reference, it takes 58 seconds for the probe to get back to Earth.
6. This 58 seconds in the probe's frame is negative 200 seconds in the Earth's frame.

Since, in the Earth's frame, there was ~100 seconds from the probe's launch to the deployment of the black box and negative 200 seconds from the black box's deployment to its arrival, the black box arrives about 100 seconds before the probe launches and has thus objectively traveled back in time.

[Splitsecond]

No because the black box and Earth are both relatively at rest all the time. The speed of light relative to the black box was always c. The speed of the black box was ~5c, so the speed of light during the flight of the black box was ~6c.

[Quadhelix]

No because the black box and Earth are both relatively at rest all the time.

The black box was traveling away from the Earth at 0.5c (i.e., 50% of the speed of light) when it began its return trip, not at rest relative to it. It was traveling at 0.5c because it was attached to the probe, which accelerated to 0.5c immediately after ending its FTL-trip but before the black box was launched.

The speed of light relative to the black box was always c. The speed of the black box was ~5c, so the speed of light during the flight of the black box was ~6c.

This makes no sense. Furthermore, it is irrelevant: it does not matter how the black box got back to Earth, only that it did so in 58 seconds in the frame in which it was launched.

Since this frame was 500c*s from Earth and traveling away at 0.5c, that 58 seconds translates to negative 200 seconds in Earth's frame.

[Splitsecond]

The black box was traveling away from the Earth at 0.5c (i.e., 50% of the speed of light) when it began its return trip, not at rest relative to it. It was traveling at 0.5c because it was attached to the probe, which accelerated to 0.5c immediately after ending its FTL-trip but before the black box was launched.




This makes no sense. Furthermore, it is irrelevant: it does not matter how the black box got back to Earth, only that it did so in 58 seconds in the frame in which it was launched.

Since this frame was 500c*s from Earth and traveling away at 0.5c, that 58 seconds translates to negative 200 seconds in Earth's frame.

But the travel was done in a transformed space-time where the black box didn't go faster than light. You have to convert between normal and transformed space-time in your calculations.

[Quadhelix]

But the travel was done in a transformed space-time where the black box didn't go faster than light. You have to convert between normal and transformed space-time in your calculations.

But my argument doesn't care how the black box traveled, only that it was about 500 light-seconds away from Earth at t'=T and that it was at Earth at t'=T+58s.



Edit:

What I am having trouble understanding is why it is okay for the probe to go back in time in the frame of reference of the USS Einstein (see here), but not okay for the black box to go back in time in the frame of reference of the Earth.

[Splitsecond]

But my argument doesn't care how the black box traveled, only that it was about 500 light-seconds away from Earth at t'=T and that it was at Earth at t'=T+58s.



Edit:

What I am having trouble understanding is why it is okay for the probe to go back in time in the frame of reference of the USS Einstein (see here), but not okay for the black box to go back in time in the frame of reference of the Earth.

Your argument has to care about the black box because it is about the events of the black box. The FTL drive breaks the continuity of the black box wrt normal space-time. As far as the universe is concerned the black box's world line has a discontinuity.

It isn't okay for the USS Einstein to have the probe appear before it launched, just for the appearance to be detected before the launch is detected because the continuity of events is not changed, just the sequence as far as the spaceship is concerned. If causality is broken, you have a paradox, so causality must be unbreakable.

[Quadhelix]

Your argument has to care about the black box because it is about the events of the black box. The FTL drive breaks the continuity of the black box wrt normal space-time. As far as the universe is concerned the black box's world line has a discontinuity.

Yes, the black box disappears. However, you still have not given me a non-begging-the-question answer as to why the black box cannot make the trip that I described.

Your argument can be summed as follows:

1. Causality must be preserved.
2. Therefore, the black box cannot do what it is described to do.
3. Therefore, causality has not been violated.

The entire point of this argument is whether FTL travel allows causality violation.

It isn't okay for the USS Einstein to have the probe appear before it launched, just for the appearance to be detected before the launch is detected because the continuity of events is not changed, just the sequence as far as the spaceship is concerned.

Actual, simply as a point of fact, the USS Einstein is present at the launch; that is, it is passing the launch site at the time of the launch: the Einstein sees the probe disappear from r'=0 at t'=0. In the Einstein's frame of reference, the probe appears at about r'=492c*s at t'=-52s. Because, however, the probe is more than 52 light-seconds away, the Einstein doesn't detect the probe's arrival until t'=440s

If causality is broken, you have a paradox, so causality must be unbreakable.

...which is why FTL is impossible. Once FTL is allowed, then you have inherently destroyed causality.

Otherwise, you are basically saying that the probe's (post t=100s) frame is an invalid frame of reference: there is no reason that the black box could not reach Earth in 58 seconds in the Earth's frame of reference, yet there is a (as yet unexplained) reason why the black box cannot reach Earth in 58 seconds in the probe's frame of reference.

[Splitsecond]

Well it's more the fact that special relativity falls down the moment an observer sees light at >c. The black box transverses the FTL space, be it warp bubble, wormhole, subspace at relative sub-c speeds but the relative speed of its c value compared to normal c is ~5-6c. The distance actually traveled by the black box is less than c.delta.t or its speed relative to its light is <c. If you use special relativity to convert between the probe and the black box and then the black box and the Earth, you find that there is no time travel.

We know that the FTL drive to positive time to travel a distance from Earth's reference. The same will be true on the return leg. The important point is that none of the observers ever see themselves travel faster than the light they emit.

For a wormhole, you take the length of the wormhole route as the distance.
For a warp drive, you add a speed to the coordinate system.
For subspace/hyperspace/slip-stream, you convert to the subspace coordinate system, where the distance is less or c is more.
For Galactica-style hyperlight jumps or teleportation, there is no time of flight, just a discontinuity in the worldline. For this the start and end are simply detected by observers.

[Flibby]

Is the speed of light relative?

[Splitsecond]

Is the speed of light relative?

No, everything else is.