Can Warp Drives Really Make Faster-Than-Light Travel Possible?

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Discussion Overview

The discussion centers on the feasibility of warp drives for faster-than-light (FTL) travel, particularly focusing on the theoretical framework proposed by Miguel Alcubierre. Participants explore the implications of negative energy and spacetime bubbles, as well as the potential for causality violations associated with FTL travel.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants discuss the concept of negative energy and spacetime bubbles as mechanisms for achieving FTL travel.
  • There are claims that traveling FTL "within the bubble" does not eliminate the potential for causality violations in the surrounding universe.
  • One participant references a previous discussion involving a physics student from MIT, suggesting that the implications of FTL travel are complex and contested.
  • Another participant points out that while Alcubierre's theory may be valid within general relativity (GR), it could still lead to causality violations when considering round trips with different bubbles.
  • Some express skepticism about the enthusiasm surrounding warp drives, suggesting that it may stem from a lack of understanding of the underlying physics.
  • There are references to potential hazards associated with the Alcubierre drive, indicating that its practical application may be fraught with issues.
  • Participants express a mix of hope and skepticism regarding NASA's efforts in this area, with some questioning whether causality can be managed effectively.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of FTL travel and causality. Multiple competing views remain, with some arguing that FTL travel inherently implies causality violations, while others suggest that it may be possible to navigate these issues theoretically.

Contextual Notes

Participants note various assumptions and complexities regarding the definitions of causality and the mechanics of FTL travel, indicating that the discussion is limited by these unresolved aspects.

Who May Find This Useful

This discussion may be of interest to those exploring theoretical physics, particularly in the context of general relativity, causality, and speculative technologies related to space travel.

tade
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Popular Science has been running an article about Sonny White, a prominent engineer at NASA's JSC.

White has been attempting to realize a warp drive as theorized by Miguel Alcubierre of UNAM in Mexico.


Warp Factor

Faster-Than-Light Drive


Negative energy, spacetime bubbles propelling a craft faster than light.
 
Physics news on Phys.org
tade said:
Negative energy, spacetime bubbles propelling a craft faster than light.

... to boldly go into FTL causality violations.
 
1977ub said:
... to boldly go into FTL causality violations.

technically there are no CVs within the space time bubble.
 
tade said:
technically there are no CVs within the space time bubble.

"within the bubble" is not the problem. in the context of the surrounding universe, you are going FTL.

If you travel FTL "within the bubble" or if you do it by snapping your fingers, CV is implied. If you could fit the entire universe with you "within the bubble" then there'd be no problem CV-wise.

Here's a whole big jolly board discussion in which someone [who was a physics student at MIT] attempted to make this point and was rebutted with various assertions.
https://news.ycombinator.com/item?id=4536320

more with him:
https://news.ycombinator.com/item?id=4535481

The FAQ he refers to:
http://www.physicsguy.com/ftl/html/FTL_part4.html

You can work out a simple example with a train, a platform, and 2 FTL signaling devices which violates causality. You can arrange to be push a button and then shot with a laser beam before you pushed the button. It certainly makes no difference how the FTL signal gets there or whether causality is violated within the mechanism itself. Once you embed an intentional FTL event in a larger context, causality can easily be violated for observers/events in that larger context.
 
Last edited:
1977ub said:
"within the bubble" is not the problem. in the context of the surrounding universe, you are going FTL.

If you travel FTL "within the bubble" or if you do it by snapping your fingers, CV is implied. If you could fit the entire universe with you "within the bubble" then there'd be no problem CV-wise.

Here's a whole big jolly board discussion in which someone [who was a physics student at MIT] attempted to make this point and was rebutted with various assertions.
https://news.ycombinator.com/item?id=4536320

more with him:
https://news.ycombinator.com/item?id=4535481

The FAQ he refers to:
http://www.physicsguy.com/ftl/html/FTL_part4.html

You can work out a simple example with a train, a platform, and 2 FTL signaling devices which violates causality. You can arrange to be push a button and then shot with a laser beam before you pushed the button. It certainly makes no difference how the FTL signal gets there or whether causality is violated within the mechanism itself. Once you embed an intentional FTL event in a larger context, causality can easily be violated for observers/events in that larger context.

There's a lot of confusion going on in that discussion.
On a side note, I've heard that Alcubierre's workings are perfectly valid within GR.


At least NASA is boldly going... "where no man has gone before".:cool:
 
tade said:
There's a lot of confusion going on in that discussion.
On a side note, I've heard that Alcubierre's workings are perfectly valid within GR.

At least NASA is boldly going... "where no man has gone before".:cool:

It seems pretty clear to me that the "confusion" exists on the part of individuals who are more enthusiastic and less educated :)

Who is the most educated person you can find who believes that FTL does not imply CV?
 
1977ub said:
It seems pretty clear to me that the "confusion" exists on the part of individuals who are more enthusiastic and less educated :)

Who is the most educated person you can find who believes that FTL does not imply CV?


Isn't it similar to recession velocities being FTL due to curved spacetime? I don't really know, I'm clueless on GR.


I'm new to PF, not familiar with many people yet.
 
tade said:
Isn't it similar to recession velocities being FTL due to curved spacetime? I don't really know, I'm clueless on GR.

I'm new to PF, not familiar with many people yet.

i was thinking in terms of scouring the internet, or reading the news. The enthusiasm that a warp drive can go FTL without raising CV issues seems to be an uninformed position.
 
  • #10
1977ub said:
i was thinking in terms of scouring the internet, or reading the news. The enthusiasm that a warp drive can go FTL without raising CV issues seems to be an uninformed position.

True. Causality is an important principle.

But I'm not too worried about that. I hope that NASA will roll out some concrete preliminary tests soon.
It's probably a vain hope. :redface:
 
  • #11
tade said:
There's a lot of confusion going on in that discussion.
On a side note, I've heard that Alcubierre's workings are perfectly valid within GR.

It does not violate GR but it can be used to violate causality by making a round trip using two different bubbles. The paper I linked in post #5 here and in the other thread explains this in detail.
 
  • #12
cuberoot said:
It does not violate GR but it can be used to violate causality by making a round trip using two different bubbles. The paper I linked in post #5 here and in the other thread explains this in detail.

I guess it does. We'll just need to wait for NASA.
 
  • #13
I found this article fascinating on some hazards associated with the use of the alcubierre drive. If this is correct you may never want to use it.

http://arxiv.org/abs/1202.5708
 
  • #14
tade said:
I guess it does. We'll just need to wait for NASA.

Perhaps the various interested parties at NASA are confident that some guardian angel will prevent CVs.
 
  • #15
1977ub said:
Perhaps the various interested parties at NASA are confident that some guardian angel will prevent CVs.

Lol. If they cause CVs they might end up changing the fate of the human race or something like that.

Makes for good sci-fi at least. :-p
 

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