Alcubierre Drive: Special Relativity Effects, Doppler Shifting, & More

[Fsmv]

I know there are quite a few questions about this drive due to the recent news but I have a question that I haven't seen in the other threads. Say we have a working ship that has already formed the bubble of space-time distortion and accelerating towards the speed of light starting from some arbitrarily small velocity.

Do the inhabitants of the spacecraft experience any sort of special relativity effects? Since one could go faster than light, they would be able to go somewhere and land then look back at themselves traveling, well the light they emitted anyway, right? Would that light be Doppler shifted or is there something that prevents you from observing such a ship, would it not emit light outside the bubble?

Maybe these questions are nonsensical since I don't understand that much about the drive. Either way, I'd like to know more about the effects of actually traveling somewhere and then arriving there faster than the speed of light, specifically utilizing the Alcubierre drive.

 

[Nugatory]

Strictly speaking, the Alcubierre travelers aren't moving faster than light, they're arriving at their destination before a light signal that left at the same time as them but followed a "longer" path through spacetime. You might try "www.physicsforums.com/showthread.php?t=637052" thread for some discussion of the sorts of things that could happen as a result.

 

[Chronos]

The problem with ftl travel is it generates paradoxes. A craft traveling at 2c would arrive at its destination before it launched [by its clock], according to the usual GR formula. Imagine launching from Earth in a vehicle traveling at 2c that has a rear oriented laser signaling device pointing at a mirror on the launch pad. Since your craft is traveling at 2c, the pulse from the rear laser can never catch up with your craft until it stops. Hence, your view of the rear pointed signal can never be obstructed by your space craft.

 

[SJBauer]

Assuming the impossible, even though the Alcubierre drive does not directly violate the laws of physics, it does have difficulties that may be impossible to overcome. One such problem states that the only way such a transport system is possible is if, like a train, it followed a pre-set path that had been laid ahead of time. To complicate matters, this "track" must also be laid at the speed of light; essentially requiring that an Alcubierre drive would have to precede itself in order to create an Alcubierre track. Since each preceding Alcubierre drive would have to precede itself, it does not seem possible that the Alcubierre track could be created. Rather it might just remain stationary like a black hole until acted upon by other gravitational influences. In other words, it could only be guided toward a direction from outside its buble of SpaceTime.

 

[sardar]

I can provide some insight into the potential effects of the Alcubierre drive on special relativity and Doppler shifting.

Firstly, it is important to note that the Alcubierre drive is a theoretical concept and has not yet been proven to be possible. It is based on the idea of manipulating space-time to create a "bubble" in which a spacecraft can travel faster than the speed of light, while the spacecraft itself remains stationary.

With that in mind, let's consider the scenario you have presented. If a spacecraft were to successfully create the space-time bubble and accelerate towards the speed of light, the inhabitants of the spacecraft would indeed experience special relativity effects. Time dilation and length contraction would occur, meaning that time would pass slower for the inhabitants compared to an external observer and their length would appear shorter.

As for the observation of light emitted from the spacecraft, it is possible that the light would be Doppler shifted. This is because, from an external observer's perspective, the spacecraft would appear to be moving at superluminal speeds, causing a shift in the frequency of the emitted light. However, it is also possible that the space-time bubble created by the drive would prevent any light from escaping, making it impossible to observe the spacecraft from the outside.

As for the effects of arriving at a destination faster than the speed of light, it is difficult to say for certain without knowing more about the mechanics of the drive. However, one possible consequence could be a violation of causality, as arriving at a destination before the light emitted from the spacecraft could potentially lead to paradoxes.

Overall, the Alcubierre drive is a fascinating concept that raises many questions and challenges our understanding of space and time. However, until it is proven to be possible and further research is conducted, we can only speculate on its potential effects on special relativity and other physical laws.