It never ceases to amaze me how smart some people are.
Positive Energy Warp Drive from Hidden Geometric Structures
141–150 of 194 posts
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#142Earlier quoted context omitted.
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 ca…
> 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?
By "recent", you have to go back almost 30 years to the Aclubierre Drive (https://en.wikipedia.org/wiki/Alcubierre_drive) described in 1994. It forms part of the "we can come up with some interesting solutions to general relativity" literature.
That literature is not just a recent phenomenon. Research into theoretical wormholes (https://en.wikipedia.org/wiki/Wormhole#Development) goes back decades further.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#143Earlier quoted context omitted.
Your thinking assumes a preferred reference frame. https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity
Why could it not somehow hold in all reference frames?
In relativity, the speed of light is the only constant speed; therefore, in which reference frame are you going at e.g. 10c?
Perhaps the CMB is the preferred frame of reference for all motion and this problem has a trivial solution (I am not a physicist), but everyone I’ve seen explain relativity starts with “there is no preferred frame”, and the rest follows.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#144What 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.
The quantum world constantly needs to agree on what the state of the macroscopic world is, there is a limit to the speed of that agreement happening, hence the speed limit on the spread of information (speed of light). There are contradictions happening constantly in the quantum world, but they are resolved either way.
Any contradiction would be resolved on quantum level even if it can be interpreted at macroscopic scale as breaking of causality.
The important thing for physics would be to better clarify what time is. Why is the speed of light as much as it is, why is there time dilation related to mass and why is the time slowing down for objects travelling faster.
My guess is that the quantum world needs more of its own time to agree when there are more objects (more mass) close to one another, or that a fast travelling object needs to "agree" with its surrounding more frequently, and that overhead is manifesting as slowing of its time.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#145Earlier 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. 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.
Try this: https://www.youtube.com/watch?v=au0QJYISe4c
c isn't defined as the speed of light - light travels at c, but so does everything else, when you factor in movement through time.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#146What 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.
I've never managed to see how causality is a problem for FTL travel
If we perceived the world through sonar then causality would be violated by anything supersonic. If you were shot then you'd feel the bullet first and then "see" it moving back into the gun.
AFAICS if information can travel at >c, then physical objects traveling at >c doesn't violate causality
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#147Earlier quoted context omitted.
No, it isn't. Light is unique in this way.
Correct. In a bit more detail: Here's the grid coordinate system for the streets in my town. One intersection is (0, 0). But in the grid system used by the next town over, that same intersection is (100, 200). And that's fine - we're just shifting the origin, which changes all the numbers. The same thing happens with velocity. If I'm on the ground, "stationary" means that you're not moving with respect to the ground.…
> (Well... light isn't quite unique. The speed of light is unique in that way. But gravitational waves also travel at the speed of light.)
Right - this is a subtle but important distinction! Photons don't have primacy, space-time does.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#148This 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…
The scale is all wrong. A type 1 civilisation is, rougly, civilisation that covered earth with solar panels.
This drive needs a planet's mass in the form of pure energy, that's a totally different league. Also you dint have a planet to live on after that.
This is a major stretch for even a type 2
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#149Everyone always talks about FTL travel for spacecraft, but there's also an interesting perspective from weapons side (and this a reason to be a bit careful and think about some ethics as we move along). A FTL kinetic weapon would be devastating. If it comes with a collapsing warp bubble then there's basically a gamma ray "gun" that travels right in front of your mass that is traveling at tremendous speeds. You look a…
If we're talking surprising applications of FTL, what about reducing latencies within CPUs?
There's at least three sci-fi universes I know of that used ubiquitous nanoscale wormholes to speed up their processors.
Re: Positive Energy Warp Drive from Hidden Geometric Structures
#150Earlier quoted context omitted.
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?
Walking around with the sum total of human knowledge. That featured heavily in a lot of episodes where the ship carried around a library of everything and and could communicate back to the network on Earth for everything squared. Often problems were solved by database search algorithm.
And the VR Holodeck is spot on actually. I was having moments where I was questioning how much better the experience really would be with a matter-energy converter. It already works pretty well using stupid human perceptual tricks.