Does the Alcubierre drive shorten distances?

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    Warp drive
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Discussion Overview

The discussion revolves around the Alcubierre warp drive and its implications for measuring distances in spacetime, particularly whether the distance between Earth and Alpha Centauri would be less than 4.3 light years when measured along a path through the warp bubble. The conversation includes theoretical considerations and interpretations of spacetime geometry, as well as the nature of the warp bubble itself.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that if an Alcubierre warp drive could be constructed, it would allow for travel to Alpha Centauri in less than 4.3 years due to changes in the geometry of spacetime.
  • Others argue that while the warp drive contracts space in front of the ship, this is compensated by an expansion of space behind it, suggesting that the overall distance remains invariant when measured through the warp bubble.
  • One participant asserts that the worldline of the spaceship is timelike, indicating that the ship does not travel faster than light with respect to the space inside the bubble, and therefore the distance must be less than 4.3 light years as measured through the bubble.
  • Another participant questions the interpretation of distance measurements, emphasizing that the distance from Earth to Alpha Centauri measured along a path through the warp bubble may differ from the distance measured from the ship's perspective.
  • Some participants highlight the need for careful interpretation of the ship's path and the properties of the warp bubble, which is made of exotic matter and has counterintuitive characteristics.
  • There are calls for mathematical backing to support claims about the requirements for the bubble's operation and the implications of the spacetime perturbations involved.

Areas of Agreement / Disagreement

Participants express differing views on the nature of distance measurement in the context of the Alcubierre drive, with no consensus reached on whether the distance between Earth and Alpha Centauri remains invariant or is effectively shortened when measured through the warp bubble.

Contextual Notes

Limitations include the dependence on theoretical constructs of spacetime and exotic matter, as well as unresolved mathematical interpretations regarding the mechanics of the warp bubble and its effects on distance measurements.

  • #151
So, my choice for traveler world line is very convenient. It turns out it produces a constant integrand for the odometer integral of .1 (everywhere!). So “all” that remains is determining the proper time bounds along the traveler worldline. That might take some time (proper time since I am my own world line).
 
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  • #152
PeterDonis said:
With respect to the bubble, that is correct. The bubble itself is moving with respect to Earth and Alpha Centauri. Which means that, from the viewpoint of the ship inside the bubble, Earth and Alpha Centauri are moving. That doesn't change any of the logic I gave in my previous post.


My previous post should make it clear that that is the question I am answering. I even gave you the logic behind the answer.

Here's another way of getting the answer (which I described in the previous thread you linked to): suppose the ship emits a light beam towards Alpha Centauri. Since the ship's worldline is timelike, the light beam will arrive at Alpha Centauri before the ship itself does. Since the ship takes less than 4.3 years to make the trip, the light beam must take an even shorter time to make it by the ship's clock. That means the distance, according to the ship (which means as measured through the warp bubble) must be less than 4.3 light years.
I realize this is a thought experiment, but in "practice" would a light beam even be able to leave the bubble? What I'm driving at is that with exotic matter and the reverse solution of the EFEs, we're really talking non-phyics (or perhaps to be kind "scifi"), aren't we?

EDIT: I'm in way over my head again, I realize. It just struck me as complete nonsense. o0)

But then again who am I to talk?

EDIT2: Oh, and there were a lot of hidden posts I had to activate..... Didn't see them initially.
 
  • #153
I want to highlight one point: in warp, the energy conditions are violated, and it is precisely the violation of the energy conditions that produces the effective displacement.
https://arxiv.org/abs/2103.05610
 

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