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Positive Energy Warp Drive from Hidden Geometric Structures

arxiv.org

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Re: Positive Energy Warp Drive from Hidden Geometric Structures

#111

Post by tarsinge »

gary_0 wrote: post #9

What do the authors of these warp drive papers think will happen causality-wise when the proposed vehicle effectively moves faster than c? You can't do that without doing nasty things to your light cone[0] and effectively traveling into your own past. Is a prerequisite of entertaining the idea of a warp drive that we disregard causality? As far as I know, there aren't any plausible loopholes in General Relativity tha…

I never understood the problem regarding causality and the light cone. Why a latency between photons and the FTL event break causality? Isn’t just a visual delay and the events aren’t still kind of “stacked”? Even if we alter photons we just break the visual ordering, the actions still happened in order.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#112

Post by T-A »

saagarjha wrote: post #75
dleslie wrote: post #63

Earlier quoted context omitted.

It's not creating new energy, right? It reads to me like causality violating configurations simply move energy around time as we'd move mass through space.

The second law, like all physical laws, does not violate conservation of energy. However, reversing causality can cause the reversal of entropy, which is what the second law deals with.

https://math.ucr.edu/home/baez/physics/Relativity/GR/energy_...

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#113

Post by T-A »

potatoman22 wrote: post #106
nine_k wrote: post #38

Earlier quoted context omitted.

AFAICT, GR is symmetric in relation of the direction of time, as are most other important physical theories. What may add the arrow of time is the second law of thermodynamics: a statistical evolution of a system is not symmetric. I wonder now how a violation of causality could either circumvent of contradict the second law.

I don't think we know that time's arrow is caused by the second law. Isn't that just a theory?

https://www.scientificamerican.com/article/just-a-theory-7-m...

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#114

Post by native_samples »

thaneross wrote: post #85
hyperpallium2 wrote: post #61

Earlier quoted context omitted.

If we're talking surprising applications of FTL, what about reducing latencies within CPUs?

Funnily enough, the writers of ST:TNG had this idea too. The main computer of the Enterprise-D was huge (9 decks tall) and generated a subspace field so that optical processing ran faster than light.

Star Trek's tech vision is astounding. How many things in it have actually been built? I count:

• Tablets (the padds)

• VR "holodecks"

• Computers that you can talk to and ask questions

• "Tricorders" (smartphones?)

• Turbolifts (https://www.dezeen.com/2017/07/12/thyssenkrupp-unveils-world...)

Maybe we'll get to add a warp drive to the list by the time I die.

What else?

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#115

Post by majewsky »

jchrisa wrote: post #91
quickthrower2 wrote: post #58

Earlier quoted context omitted.

How would you feel the effect? If you do it's more likely to be placebo as you can't avoid knowing where in the world you are!

I imagine if there is any amount of angular momentum imparted to the water in our cells, the reversal of the force propelling it would create a turbulent episode of transition.

The differences in force are way too miniscule on that scale. If you're looking for a measurable force differential across the extent of your own body, look at gravity instead. When standing up, the gravity at your feet is about 0.5 ppm smaller than at your head (for a body height of 1.75 meters). You don't feel that either; there is just no evolutionary advantage to being able to measure such tiny differences in local gravity, especially since we have acceleration sensors in our ears that are way more efficient at telling up from down.

The coriolis force differential, besides being rather small to begin with, has the additional problem that the coriolis force is proportional to the speed at which you're moving over the earth. If you were to accelerate to a speed where the coriolis force differential might be appreciable (e.g. by sitting in a bullet train or in a plane), it will be completely drowned out by any other momentary forces imparted upon you by the vehicle (trains or planes can move mostly straight, but not in a mathematical-grade straight line).

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#116

Post by native_samples »

jxf wrote: post #33
canjobear wrote: post #32

Previous work seemed to conclude pretty strongly that superluminal warp travel required negative energy. What's the insight here that gets around that?

The goal of warp drive is to produce a modified region of spacetime that makes it feasible to travel faster than light. There are an infinitude of different approaches. The authors in this paper find that if you impose specific constraints on the way the modified region of spacetime is shaped and evolves over time, you don't need the negative energy anymore. However, you do need a very high energy density, strong eno…

The sociology of this is fascinating. For my whole life I've heard that travelling faster than light is not only impossible, but so obviously absurdly impossible that only loons and sci-fi writers bother to think about it at all. Now I'm reading that "There are an infinitude of different approaches" to the problem!

What exactly is the breakthrough that has led to this recent spurt of warp drive papers? As far as I can tell the results are all purely theoretical and just re-arranging equations. None of them appear to rely on any recently lab discovered physics. Why couldn't this have been done in 1950, I wonder?

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#117

Post by drran »

nwallin wrote: post #79
TheDudeMan wrote: post #16

Earlier quoted context omitted.

"effectively traveling into your own past" Can you explain how traveling faster than light leads to that? Perhaps you meant "observing your own past?"

Being able to send messages faster than the speed of light grants the ability to send messages to yourself in the past. [0] If you can send messages to yourself in the past all manner of causality goes out the window. First of all, it gives you the ability to solve NP-complete problems trivially. Step 1: you receive a message from yourself from the future. It explains the problem, gives you a potential solution. Let'…

> Being able to send messages faster than the speed of light grants the ability to send messages to yourself in the past.

No, it doesn't. Even if we will be able to communicate instantly (0 delay = infinite faster than speed of light), we will not be able to send a message to the past (negative delay).

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#118

Post by fho »

foota wrote: post #82
hyperpallium2 wrote: post #61

Earlier quoted context omitted.

If we're talking surprising applications of FTL, what about reducing latencies within CPUs?

You don't even need FTL for that, just move quicker than your cpu!

I assume that in theory this would also work the other way around ... find a way to make your CPU move (spatially) a lot slower than you and perform millenias worth of computation in your coffeebreak.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#119

Post by liminvorous »

fpgaminer wrote: post #90
cletus wrote: post #39

The lesson we should really take here is the power of wishful thinking. People dearly want to believe in FTL travel. Without it, the Universe just seems so vast, empty and distant. The truth is it is and it isn't. It's only really that on our current time scales. Not to be a broken record (there's some new variation on some old idea like every week it seems), but I'm firmly in the camp that believes FTL isn't possibl…

> Theoretical: a lot of these theories rely on people not understanding the domain of a function We thought it was an aberration of mathematics when Einstein's equations blew up into singularities. A singularity couldn't exist in the real world, they said. Must just be an artifact of us using "real numbers", and we needed to be careful to respect the domains of those functions. Well, turns out singularities do exist…

Event horizons exist, I don't think we have any evidence singularities really exist inside them, or any way gather such evidence.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#120

Post by jjgreen »

gary_0 wrote: post #9

What do the authors of these warp drive papers think will happen causality-wise when the proposed vehicle effectively moves faster than c? You can't do that without doing nasty things to your light cone[0] and effectively traveling into your own past. Is a prerequisite of entertaining the idea of a warp drive that we disregard causality? As far as I know, there aren't any plausible loopholes in General Relativity tha…

Only (well-written) f77 is faster than c
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