Questions - FTL in OA
Even clarketech must ultimately obey the laws of physics. It may be able to do things we find miraculous, but it cannot do things that are logically or physically impossible.
In order for information to be sent via quantum entangled qubits, a classical bit of information describing the measurement basis must also be sent, which adheres to v <= c.
Because it has no basis in physics. All imaginary quantities found in physics (e.g., quantum mechanical eigenstates) reduce to real eigenvalues when measured. This property, called Hermiticity, is rooted quite firmly in the mathematical basis of physics, and all possible physical theories that describe the quantum behavior of the universe.
The concept of wormholes, inflated from the quantum foam, and held open with negative energy/exotic matter is one of the few feasible solutions to FTL travel.
We have incorporated a version of the Alcubierre Warp drive within the scenario, albeit an STL version, we call a void mote. These are extremely difficult to produce and fairly limited in capability. None of the works of Alcubierre, Van Den Broeck, Hillman, Natario or the Loup et. al. proposal has demonstrated a solution to the causality paradox inherent in FTL travel. This is because you cannot have FTL, relativity, and causality in the same universe. A causal FTL universe would require the assumption that Einstein was wrong and only Newtonian physics apply. Because wormholes are not technically FTL travel they do not conflict with causality.
A brief essay on causality:
I need the help of my friends from the Canadian Space Corps to help me violate causality. I arrange for Alice to move out into space, and then assume a position at rest relative to me. Bob has to fly past me at event C, and Carol has to fly past Alice at event B. Things are arranged so that Bob and Carol are moving with the same speed, and both are moving in the direction from me towards Alice. At event A I use my ansible to transmit a message instantaneously to Alice at event B. Alice gives a copy of the message to Carol, who is flying past at the time that Alice receives my transmission. Now, Carol and Bob are in a different inertial frame to Alice and me, so they have a different slice through spacetime that they consider the present. This means that if Carol transmits the message to Bob with her ansible, then it will arrive at event C, just as Bob's ship if flying past me. Bob can then give me a copy of my message. The net result is that I have transmitted a message into my own past.
For any faster-than-light system there will be some inertial frame in which it appears to act instantaneously, and so the same argument may easily be applied to any such system.
Notice that you have to use the ansible twice to make a causality violation. You might think that things would be okay if your system only worked once in the entire history of the universe, but this won't work - in general there is no way in which to decide which use of the system was the first. Another possible way to avoid causality violations is to say that all the ansibles only work if they are at rest relative to each other, so that they share the same simultaneities. This, however, defines a preferred frame, so you'd have to throw away the principle of relativity.
I should note that this violation of causality does not involve a closed timelike curve (parts of the message's trajectory are spacelike).
Hyperspace, otherwise known as large extra dimensions, exists in a separate landscape at energy densities commensurate with the Big Bang. At the current temperature of the universe, it has been compactified down to a 3+1dimensional brane; the higher dimensional bulk is fundamentally inaccessible except via gravitons.
As a final thought, although we have chosen to include wormholes, we also understand they are purely theoretical, albeit on a pretty firm basis with respect to General Relativity (a wormhole 'No-Go' theorem has yet to be proven; on the other hand, ANEC violations are already found to exist in nature). It is a razors edge, but the Orion's Arm scenario is ultimately science fiction. We have quite simply selected wormholes as the solution that, as far as we know, does not violate modern understanding of the universe.
We do allow both. Wormholes do not violate causality, as they are an artifact of non-simply connected manifolds in General Relativity. Warp drives may violate causality; we allow warp metrics that do not possess closed timelike curves (e.g., are non-FTL).
The warp drive metric creates a closed timelike curve the instant v > c (with v being a property of the warp metric), which violates causality. (If you prefer, causes a Cauchy horizon to form.)
Due to the repetitive nature of this question we have decided to devote an entire section of the FAQ pages to answering it. Please note that the arguments we present here are in keeping with a hard science scenario based on a causal relativistic physical universe. We are not criticizing other franchises for their choice to include such phenomena. These FAQs are purely to answer the questions addressed to the Orion's Arm Universe and our stand on the matter.