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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

#21

Post by TrevorJ »

akiselev wrote: post #5
SmellTheGlove wrote: post #2

This sounds pretty amazing, but I also have no real idea what I'm reading. > A modest numerical analysis is carried out on a set of example configurations, finding total energy requirements four orders of magnitude smaller than the solar mass. Can someone smarter than me say whether this is within the (reasonable-ish?) realm of matter-antimatter reactions? Like Star Trek!? 4 orders of magnitude less than the sun's ma…

The first paper detailing the Alcubierre drive required exotic particles with negative mass to achieve a spacetime bubble (soliton) which is an issue since particles with negative mass have never been observed. The next big paper figured out how to do it with regular matter and it brought the requirements down to the energy equivalent of four solar masses. That would put it squarely into the realm of a type II or III…

Would be interesting if paired with the harvesting of energy from a black hole. It is theorized that you can do this 'remotely' by slingshotting a laser around a black hole. This functions the same way a normal gravity assist does, except in this case it's photons, and not spacecraft. Shoot a laser around one side of a black hole, it returns to you around the other side, but at a higher energy wavelength. In this way, perhaps you would not need to store the energy needed 'in' your spacecraft, but instead in a black hole that is some safe distance away.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#22

Post by [deleted] »

sigmoid10 wrote: post #15
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…

General relativity actually tells us nothing about whether causality is absolute. You can easily make up spacetime configurations that violate causality and still conform to general relativity. It's just that most people believe that causality should be protected, because... well it would be really weird if it wasn't. But it's just a conjecture and not like a theorem or anything.

[deleted]

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#23

Post by TrevorJ »

XorNot wrote: post #10
beervirus wrote: post #7

Earlier quoted context omitted.

> 4 orders of magnitude less than the sun's mass does sound like a positive development - still a lot but less than before, right? That’s something like 10^43 joules. Still not achievable anytime soon.

Progress in warp field research though has resulted in significant energy reductions though - everytime a more efficient formulation is found its a step on the way to a possible practical system. After all, if it was easy then everyone would be doing it.

We've definitely achieved progress on this sort of scale with transistor density. Not that it's at all similar, but it's interesting to observe that we do seem to be able to occasionally bring things within our grasp that would have sounded absolutely silly a lifetime ago.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#24

Post by wyager »

sigmoid10 wrote: post #15
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…

General relativity actually tells us nothing about whether causality is absolute. You can easily make up spacetime configurations that violate causality and still conform to general relativity. It's just that most people believe that causality should be protected, because... well it would be really weird if it wasn't. But it's just a conjecture and not like a theorem or anything.

It doesn't guarantee that causality is protected, but it certainly seems pretty suggestive that GR creates a big infeasibility region for positive-mass objects (outside of the future-past light cone). There are ways you could still violate causality despite this restriction, but it makes it a lot harder. There's no particular reason we couldn't have a ++++ spacetime, which wouldn't have this form of causal censorship, so I count this as one more piece of evidence towards "maybe causality violation is impossible".

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#25

Post by gary_0 »

TheDudeMan wrote: post #16
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…

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

No, not "observing your own past". Instead, your past self could observe your future self. And then your future self could turn their FTL ship around and run you over, killing their past self and creating a paradox.

https://old.reddit.com/r/askscience/comments/l9sba/why_does_...

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#27

Post by px43 »

gary_0 wrote: post #25
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?"

No, not "observing your own past". Instead, your past self could observe your future self. And then your future self could turn their FTL ship around and run you over, killing their past self and creating a paradox. https://old.reddit.com/r/askscience/comments/l9sba/why_does_...

> turn their FTL ship around

I feel like this is the part that would probabally be hard (ie not possible) when going faster than light, assuming such a thing is possible.

Also whatever magical space warp it is that lets you go that fast could presumably also obscure your ability to see yourself in the distance.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#28

Post by a1369209993 »

javajosh wrote: post #20
incompatible wrote: post #17

Earlier quoted context omitted.

I'd guess there would be frames of reference (with relative high-speed motion) in which you'd appear at the destination before you've left the origin. The laws of physics are supposed to hold regardless of which frame of reference you use.

SR is 2 assertions, really: first, that the laws of physics are invariant in all reference frames, and second (and far stranger), that the speed of light is invariant in all reference frames. It's that second rule that must be violated for FTL to work - FTL implies a reference frame in which light can, at the very least, switch directions! That is, light from behind you looks like it's coming from the front (but stil…

> SR is 2 assertions, really: first, that the laws of physics are invariant in all reference frames, and second (and far stranger), that the speed of light is invariant in all reference frames.

Technically that's only one assertion (that is, the second is a strict subset of the first).

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#29

Post by javajosh »

a1369209993 wrote: post #28
javajosh wrote: post #20

Earlier quoted context omitted.

SR is 2 assertions, really: first, that the laws of physics are invariant in all reference frames, and second (and far stranger), that the speed of light is invariant in all reference frames. It's that second rule that must be violated for FTL to work - FTL implies a reference frame in which light can, at the very least, switch directions! That is, light from behind you looks like it's coming from the front (but stil…

> SR is 2 assertions, really: first, that the laws of physics are invariant in all reference frames, and second (and far stranger), that the speed of light is invariant in all reference frames. Technically that's only one assertion (that is, the second is a strict subset of the first).

No, it isn't. Light is unique in this way.

Re: Positive Energy Warp Drive from Hidden Geometric Structures

#30

Post by gary_0 »

px43 wrote: post #27
gary_0 wrote: post #25

Earlier quoted context omitted.

No, not "observing your own past". Instead, your past self could observe your future self. And then your future self could turn their FTL ship around and run you over, killing their past self and creating a paradox. https://old.reddit.com/r/askscience/comments/l9sba/why_does_...

> turn their FTL ship around I feel like this is the part that would probabally be hard (ie not possible) when going faster than light, assuming such a thing is possible. Also whatever magical space warp it is that lets you go that fast could presumably also obscure your ability to see yourself in the distance.

"Turning around" is just stopping at some point (ie. some inertial reference frame) and then accelerating in the opposite direction with your FTL drive. You have all the time in the world to do this maneuver because you're already effectively in the past: https://physics.stackexchange.com/a/54242
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