Can Curved Spacetime Enable Faster-Than-Light Travel?

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Discussion Overview

The discussion centers on the possibility of using curved spacetime to enable faster-than-light travel, exploring theoretical concepts within general relativity and various proposed propulsion mechanisms. Participants examine the implications of manipulating spacetime around a spacecraft and the feasibility of such approaches.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants propose that creating a dense region of matter at the back of a spacecraft could curve spacetime in a way that allows for faster-than-light travel, likening it to "surfing" on distorted spacetime.
  • Others argue that a dense region of matter would pull the spacecraft backwards, preventing any faster-than-light travel.
  • A participant questions the feasibility of the initial proposal, suggesting that the gravitational force produced by the mass would cause the spacecraft to accelerate towards it, which may not lead to the intended effect.
  • Some participants express skepticism about the existence of a known solution to the Einstein Field Equations that supports the proposed mechanisms for faster-than-light travel.
  • One participant suggests the idea of creating a push/pull propulsion system by redistributing mass, but another counters that this would not effectively move the spacecraft unless mass is expelled into space.
  • There is a mention of using light and its momentum for propulsion, with references to solar sails as a mass-efficient but low-acceleration option.
  • A later reply emphasizes that regardless of how spacetime is curved, nothing can exceed the speed of light locally, reiterating the built-in speed limit of Einstein's theory.
  • Another participant speculates about generating negative curvature behind the craft, which would require negative energy density, drawing a parallel to the Alcubierre drive concept.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the feasibility of faster-than-light travel through curved spacetime, with no consensus reached on the validity of the proposed mechanisms or their implications.

Contextual Notes

Some limitations include the lack of established solutions to the Einstein Field Equations that support the discussed concepts, as well as unresolved questions about the practical application of proposed propulsion systems.

Marcarious Thomas
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Based on the current understanding of general relativity, it is possible that curving spacetime in the back of a spacecraft would allow for faster-than-light travel. In general relativity, the curvature of spacetime is determined by the universe's distribution of matter and energy. If a propulsion system could create a very dense region of matter at the back of a spacecraft, wouldn't it possibly curve spacetime in a way that allows the spacecraft to travel through space faster than the speed of light, essentially "surfing" on a wave of distorted spacetime. This type of propulsion has some advantages over the Alcubierre drive in terms of energy requirements and does not involve the same degree of manipulation of the surrounding universe. What are your thoughts?
 
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A dense region of matter at the back pulls the spacecraft backwards. It doesn't allow faster-than-light travel in any way.
 
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I'm not getting the proposal.

You have a mass that curves spacetime - produces a gravitational force in older language, and that causes the spaceship to accelerate towards the mass. The spaceship then pushes the mass forward so it can keep accelerating forever.

I don't think that's going to work.
 
 
Marcarious Thomas said:
Based on the current understanding of general relativity, it is possible that curving spacetime in the back of a spacecraft would allow for faster-than-light travel.
You speak as though there is a known solution of the Einstein Field Equation that has these properties. Can you give a reference?

If you are not aware of such a solution, then your post is personal speculation, which is off limits here at PF.
 
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Marcarious Thomas said:
wouldn't it possibly curve spacetime in a way that allows the spacecraft to travel through space faster than the speed of light, essentially "surfing" on a wave of distorted spacetime. This type of propulsion has some advantages over the Alcubierre drive in terms of energy requirements
I also don’t think there is a known solution of the EFE with these properties. I also think a reference is in order.
 
Marcarious Thomas said:
Based on the current understanding of general relativity, it is possible that curving spacetime in the back of a spacecraft would allow for faster-than-light travel. In general relativity, the curvature of spacetime is determined by the universe's distribution of matter and energy. If a propulsion system could create a very dense region of matter at the back of a spacecraft, wouldn't it possibly curve spacetime in a way that allows the spacecraft to travel through space faster than the speed of light, essentially "surfing" on a wave of distorted spacetime. This type of propulsion has some advantages over the Alcubierre drive in terms of energy requirements and does not involve the same degree of manipulation of the surrounding universe. What are your thoughts?
You could start your investigations here:

 
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Would it be possible to create more density in the rear of the craft while also lessening density in the front? Creating a push/pull propulsion system much like a water pump? Redistribution of mass would be important but is it achievable in space?
 
nicm05 said:
Would it be possible to create more density in the rear of the craft while also lessening density in the front? Creating a push/pull propulsion system much like a water pump? Redistribution of mass would be important but is it achievable in space?
No. That's just moving stuff around your center of mass, which doesn't move. Unless you start throwing stuff out into space, of course, but that is just a rocket.
 
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Ibix said:
No. That's just moving stuff around your center of mass, which doesn't move. Unless you start throwing stuff out into space, of course, but that is just a rocket.
What is being done with light and its momentum to use as propulsion? Everything I’ve read is older and the thread has died off
 
  • #11
nicm05 said:
What is being done with light and its momentum to use as propulsion? Everything I’ve read is older and the thread has died off
As a rocket it's very mass efficient but extremely low acceleration. Solar sails have been deployed, though.
 
  • #12
Marcarious Thomas said:
Based on the current understanding of general relativity, it is possible that curving spacetime in the back of a spacecraft would allow for faster-than-light travel. In general relativity, the curvature of spacetime is determined by the universe's distribution of matter and energy. If a propulsion system could create a very dense region of matter at the back of a spacecraft, wouldn't it possibly curve spacetime in a way that allows the spacecraft to travel through space faster than the speed of light, essentially "surfing" on a wave of distorted spacetime. This type of propulsion has some advantages over the Alcubierre drive in terms of energy requirements and does not involve the same degree of manipulation of the surrounding universe. What are your thoughts?

The core problem is no matter how you curve spacetime, you cannot make anything travel faster than light locally.Einstein's theory has a built-in speed limit that applies to all matter and energy moving through spacetime, regardless of curvature.

What Actually Happens? When you create dense matter behind a spacecraft, you're essentially creating a gravitational field. This does curve spacetime, but the spacecraft still follows geodesics (the straightest possible paths through curved spacetime). Locally, it never exceeds the speed of light, you've basically built a very inefficient gravitational slingshot.
 
  • #13
Not sure but I think the OP is referring to generating negative curvature behind the craft to push it. This would need some negative energy density. At least this is similar to the "Alcubierre drive."
 

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